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Table of Content
25 April 2020, Volume 71 Issue S1
    Determination and correlation of vapor-liquid equilibrium for polyoxymethylene dimethyl ether system
    Zhuodong SONG, Zuoyi ZHANG, Xuelong PAN, Yunfang WANG
    2020, 71(S1):  1-6.  doi:10.11949/0438-1157.20191346
    Abstract ( 63 )   HTML ( 7)   PDF (482KB) ( 30 )  
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    The vapor-liquid equilibrium data of the PODE2-PODE3 binary system was determined by the modified Rose vapor-liquid equilibrium reactor under normal pressure conditions. The thermodynamic consistency test was carried out on the measured experimental data, and the results showed that the measured vapor-liquid equilibrium could pass the thermodynamic consistency test. The Aspen Plus v8.8 simulation software was used to correlate the NRTL, Wilson, and UNIQUAC activity coefficient models respectively, and the corresponding binary interaction parameters are obtained through regression. By comparison, the average absolute deviations of the temperature and vapor phase composition between the fitted and experimental values are not more than 0.37 K and 0.0044, respectively, indicating that the fitted results of the three models are in good agreement with the experimental data, and the deviations are all within a reasonable range. This work adds basic data for distillation to the chemical database, and also lays the foundation for further research on distillation design and engineering design with PODE2 and PODE3 systems.

    Vapor-liquid equilibrium for methanol-formaldehyde-polyoxymethylene dimethyl ethers ternary system
    Pan LI, Hui KONG, Zhuodong SONG, Zuoyi ZHANG, Yunfang WANG
    2020, 71(S1):  7-14.  doi:10.11949/0438-1157.20190440
    Abstract ( 42 )   HTML ( 5)   PDF (552KB) ( 15 )  
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    Polyoxymethylene dimethyl ether (PODEn) is a kind of compound with high oxygen content,which is developing to be a high quality diesel additive in recent years.At a constant pressure of 101.3 kPa, the vapor-liquid equilibrium data of methanol-formaldehyde-PODE2 ternary system was determined using the improved vapor-liquid equilibrium double cycle Rose kettle.Based on maximum-likelihood method,the measured ternary vapor-liquid equilibrium data were correlated by NRTL, Wilson, and UNIQUAC activity coefficient model with Aspen Plus software.And the corresponding binary interaction parameters and simulated calculation values of the three models are obtained respectively. By comparing the calculation value of three models with experimental value, the average absolute deviation in boiling point and vapor-phase composition were determined,which were less than 1.10 K, 0.0250 and 0.0240, respectively.The correlation results of the three models are applicable to the system, and the obtained binary interaction parameters can be applied to the distillation design of the methanol-formaldehyde-PODE2 ternary system, laying a data foundation for the industrial separation optimization of the related matter system.

    Structure and hydrogen bonding study on acylamino acid protic ionic liquids composed of 2-N-ethylhexylethylenediaminim cation with acylalanineate anions
    Jiaxin LIU, Yu XU, Er HUA
    2020, 71(S1):  15-22.  doi:10.11949/0438-1157.20191380
    Abstract ( 25 )   HTML ( 0)   PDF (791KB) ( 11 )  
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    The possible molecular structures S1—S5 of acylamino acid protic ionic liquids (AA-PILs) composed of 2-N-ethylhexylethylenediaminium cation coupled with acylalanineate anions forming [HEtHex][Acylala] were studied by the density functional theory at M06-2X/6-311G (d,p) level. The obtained BSSE-corrected interaction energies (ΔE0BSSE) for all the structures are in the region of -136.14~-117.26 kcal?mol-1. For each PIL, the values of ΔE0BSSE in the [HEtHex]1+[Acylala]- (S1—S3, protonated at the primary amine, -136.14—-127.01 kcal·mol-1) are larger than in the [HEtHex]2+[Acylala]- structures (S4 and S5, protonated at the secondary amine, -119.03—-117.26 kcal·mol-1). The IR results show that N—H vibration spectra is disappeared. In the meantime, the stronger O—H vibration spectra appeared in the region of 2400—2815 cm-1 since stronger O—H…N hydrogen bond was formed between [HEtHex] molecule and [Acylala] molecule. The results of natural bond orbital the stabilization energy mainly caused by the interaction between the lone pair electron lp(N) in the [EtHex] and the anti-bonding orbital σ*(O—H) in the [Acylala]: lp(N)→σ*(O—H). The hydrogen bonding energy and the second-order interaction energies are in the range of 18.69—24.19 kcal·mol-1 and 43.58—57.58 kcal?mol-1, respectively. H-bonding between [HEtHex] and [Acylala] is classified as the strong hydrogen bond.

    Thermodynamic study of liquid air energy storage with air purification unit
    Chen WANG, Xiaohui SHE, Xiaosong ZHANG
    2020, 71(S1):  23-30.  doi:10.11949/0438-1157.20191131
    Abstract ( 30 )   HTML ( 0)   PDF (643KB) ( 7 )  
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    In the current research on liquid air energy storage (LAES), it is found that the performance of LAES system is generally overestimated without considering the power consumption of air purification. This paper therefore proposes a complete LAES system with air purification unit.The LAES system consists of three parts: charging cycle, discharging cycle and TSA process.The whole system is verified to be feasible by the simulation in the Aspen Plus? version 8.4, and the thermodynamic analysis of this system is carried out. The results show that the thermodynamic performance of the system can be effectively improved by increasing the discharging pressure, the air turbine inlet temperature and the proportion of the thermal oil used in the discharging cycle. About 36% of the stored heat of compression is not fully used, if it is totally recycled, the exergy efficiency of the whole system can reach 0.623. The electricity storage efficiency of the LAES system with air purification unit is 0.471, which is 6.8% lower than that of the baseline LAES system.

    Topology optimization on heat conduction based on entransy theory
    Tingwei ZHANG, Bin LI, Xiaoqiang ZHAI
    2020, 71(S1):  31-37.  doi:10.11949/0438-1157.20191079
    Abstract ( 27 )   HTML ( 2)   PDF (922KB) ( 16 )  
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    Based on entransy theory, the entransy equilibrium equation for two-dimensional steady heat conduction with internal heat source is derived, and the entransy dissipation in this heat conduction process is analyzed. Then, taking entransy dissipation as the objective function, the thermal conductivity of the material as the design variable, the topology model is built with solid isotropic microstructure with penalization method, the model is solved by globally convergent method of moving asymptotes. The entropy generation is also applied as the objective function to compare with the entransy dissipation. The results show that both of minimum entransy dissipation and minimum entropy generation lead the similar heat transfer structure during the optimal process, the topology structure extends outward gradually as the iteration goes on and tends to be optimal, the average temperature can be decreased by 9℃. Finally, the topology structures with different high conductive material fraction are compared under the objective function of minimum entransy dissipation, the results indicate that the entransy dissipation decreases under different volume ratios of high thermal conductive material. Considering the optimization effect and cost, with the high conductive material fraction of 20%, the entransy dissipation of optimal structure can be reduced to 8.7%.

    Thermodynamic study on fluid catalytic cracking of Fischer-Tropsch wax to produce clean gasoline
    Jiannian HAN, Gang WANG, Mei YANG, Meijia LIU, Chengdi GAO, Jinsen GAO
    2020, 71(S1):  38-45.  doi:10.11949/0438-1157.20190694
    Abstract ( 27 )   HTML ( 3)   PDF (528KB) ( 42 )  
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    Fischer-Tropsch (F-T) wax is mainly composed of long-chain paraffin without any sulfur or nitrogen and is well suited for producing clean gasoline. The contents of naphthenic and aromatic species of F-T wax are exceptionally low, a high gasoline fraction with a high-quality motor octane number and low olefin fraction is still problematic. Thus, the solution aims at enhancing isomerization and aromatization reactions in the fluid catalytic cracking (FCC) process. This paper shows that the thermodynamic analysis of the catalytic cracking reactions of F-T wax. Emphasis was given to the enthalpy change and equilibrium constant of the reaction to produce gasoline fraction at different temperatures. The results of the calculation indicate that the cracking of highly paraffinic F-T wax is endothermic (enthalpy change on reaction is about 80 kJ/mol), and the equilibrium constant and the equilibrium conversion from reactant to products increase with increasing temperature.In the case of isomerization, the equilibrium constant of n-paraffin in isomerization is extremely lower than olefin. It s speculated that olefin cracked from n-paraffin isoforms further to i-paraffin, reasonably. Therefore, a zoned reactor can be designed to promote the conversion of olefin. The equilibrium constant of n-paraffin cyclization is low at different temperatures and then occurrence of reaction is difficult. On the other hand, the value of the equilibrium constant of aromatization of naphthenic is high, as a consequence, suitable reaction temperature is the key to increase the aromatics in gasoline further.

    Performance optimization of regenerated Brayton heat pump based on ecological coefficient of performance criterion
    Jie XU, Jun WANG, Liping PANG, Meng LIU
    2020, 71(S1):  46-50.  doi:10.11949/0438-1157.20191314
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    Due to the destruction of the ozone sphere by chlorofluorocarbon (CFC) and the pressure of environment protection, the traditional vapor-compression heat pump using CFC as working fluid is increasingly restricted. Brayton heat pump, of which working fluid is environmental-safe air has been paid more attention. The Brayton heat pump cycle is one of the most important air heat pump cycles. In this paper, a performance analysis and optimization of a regenerated Brayton heat pump cycle has been carried out by taking the ecological coefficient of performance (ECOP), i.e., the ratio of heat load to the loss rate of availability (or entropy generation rate), as the optimization objective. The irreversibilities considered in the analysis include the finite heat transfer rate in the hot- and cold-side heat exchangers and the regenerator, the non-isentropic compression and expansion losses in the compressor and expander, and the heat leakage. The maximum of the ecological performance criterion and the corresponding optimal conditions have been derived analytically. The effects of the temperature of the working fluid on the performance of this cycle have been investigated. The influences of the effectiveness of the regenerator as well as the hot- and cold-side heat exchangers, the isentropic efficiencies of the compressor and expander on the ECOP are examined and shown by numerical examples.

    Comparison of air-source heat pump water heater performance with transcritical cycle using CO2, R170 and R41 as refrigerant
    Dong WANG, Yaru LIU, Zhuo CHEN, Zunli KOU, Yuehong LU
    2020, 71(S1):  51-56.  doi:10.11949/0438-1157.20191137
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    On the basis of an air-source heat pump water heater (ASHPWH) system, a thermodynamic model used to calculate system performance is developed. Then, the performances and exergy efficiencies of a transcritical cycle with CO2, R170 and R41 are investigated and compared. The results indicate that the COPheat and exergy efficiencies of R41 (R170) system are about 31.77% (4.9%) and 23.34% (3.6%) higher than that of CO2 system under the same condition. R41 and R170 also have obvious advantages in increasing the heating capacity. Moreover, the optimum high pressure of systemwith R41 (R170) is more than 35% (43%) lower compared to that with CO2. So, besides CO2, R41 and R170 are also promising refrigerants for an ASHPWH system.

    Fluid dynamics and transport phenomena
    Analysis of velocity and concentration field characteristics of heavy gas leakage in large space
    Qianru ZHANG, Xu ZHANG, Wei YE, Chengqiang ZHI, Yixiang HUANG, Wenxuan ZHAO, Jun GAO
    2020, 71(S1):  57-67.  doi:10.11949/0438-1157.20191163
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    In the real industrial plants, the equipments are often critical to the contaminant dispersion and distribution. The leakage position on both sides of the obstacle has been taken into consideration. Gravity intensity index, dimensionless concentration, and the proportion of flammable and explosive area have been defined. The accuracy of the computational fluid dynamics (CFD) model was verified by experiments, and the velocity field and concentration field of different pollutant release rates were calculated by CFD. The calculation results show that the structure of the velocity field and the distribution pattern of the concentration field change with the increase of the pollutant release rate. When the dimensionless number θinlet exceeds 0.0288, new eddy currents will appear near the pollution source, and the dimensionless concentration distribution begins to appear vertical stratification. When the contaminant volumetric release rate exceeds 2.66667×10-5 m3/s, the size of the flammable, explosive and explosive areas becomes significant, leading to potential explosion risks.

    Numerical simulations on unsteady temperature distribution of sandwich bulkhead tank in launch vehicle
    Bin WANG, Ruisheng YANG, Weidong ZHENG, Rui ZHOU, Xiaobin ZHANG
    2020, 71(S1):  68-76.  doi:10.11949/0438-1157.20190824
    Abstract ( 31 )   HTML ( 1)   PDF (1438KB) ( 8 )  
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    In the launch vehicle with liquid oxygen and kerosene as propellants, the load-bearing sandwich bulkhead tank can shorten the length and lengthen the aspect ratio of the whole vehicle. And it can eliminate the segment between the liquid oxygen (LO2) tank and the kerosene tank, so as to reduce the structural mass. The bulkhead is required to have good thermal insulation properties while bearing the bi-directional pressure load of the LO2 and kerosene tank. The unsteady temperature distribution of the tank, including the liquid nitrogen (LN2) and the kerosene tank and the foam cored sandwich bulkhead, is analyzed with the CFD method when it is cooled down from room temperature to the moment the LN2 filling is completed. The numerical model considers the effect of icing on the thermal boundary of the tank surface and the LN2/vapor nitrogen (VN2) phase change process due to heat leakage. The influence of whether the fork ring is wrapped or unwrapped PMI insulation material on the kerosene temperature and the LN2 evaporation rate is especially analyzed. The calculation results show that the local minimum temperature of the kerosene is less than 240 K when the fork ring is wrapped with the insulation material, while it is greater than 260 K when the insulation material is not included. The calculation results provide reliable reference for the optimal design of LO2 and kerosene bulkhead tank.

    Experimental investigation on performance of temperature control system for aircraft precision instrument
    Yang LI, Shoujin CHANG, Haitao HU, Haoran SUN, Zhancheng LAI, Shanmin LIU
    2020, 71(S1):  77-82.  doi:10.11949/0438-1157.20200127
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    To improve the performance of aircraft precision instrument, a temperature control system with passive heat dissipation and active temperature control was designed. In the system, the heat pipe and radiation coating were used as passive radiator to transfer the heat from the instrument. The first stage temperature control was established by semiconductor cooler and insulation layer, and the second stage temperature control was established by electric heating device. The control logic was designed to control temperature. A verification test platform was built, and the temperature control accuracy of the temperature control system under different operating conditions was tested. The result shows that the temperature control accuracy of the system is within ±0.1℃ under the conditions of different environmental temperatures and system setting temperatures.

    Experimental investigation on condensation heat transfer of refrigerant R134a in micro-scale channel
    Hongbo ZHAN, Wenyuan ZHENG, Tao WEN, Dalin ZHANG
    2020, 71(S1):  83-89.  doi:10.11949/0438-1157.20191168
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    A condensation heat transfer test system was built to investigate the condensation heat transfer characteristics of R134a flowing inside one multi-port extruded tube with the hydraulic diameters of 0.63 mm, and a jet impingement cooling method was used to condense superheated refrigerant. The experiments were performed at vapor quality between 0 and 1, mass flow rate of refrigerant between 115 and 290 kg/(m2·s), saturation pressure between 0.35 MPa and 0.5 MPa. The local condensation heat transfer coefficients of the tube under different working conditions were obtained, and the influences of several factors on condensation heat transfer were analyzed. The experimental results show that, in condensation process, the local condensation heat transfer coefficient will decrease with the decrease in vapor quality. At a certain saturation pressure, the condensation heat transfer coefficient and local heat flux are corresponding to each other. The condensation heat transfer coefficient will increase with the decrease in saturation pressure. On the basis of the experimental data, a new correlation is proposed to calculate condensation heat transfer coefficients of refrigerant R134a in the multi-port extruded tubes in experimental conditions.

    Experimental research on micro-scale effect for dynamic viscoelastic properties of polymer melt
    Kui LIU, Minjie WANG, Danyang ZHAO, Yanshai WANG
    2020, 71(S1):  90-97.  doi:10.11949/0438-1157.20200052
    Abstract ( 28 )   HTML ( 1)   PDF (2279KB) ( 11 )  
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    The viscoelastic properties of polymer melts during shear flow process are affected by the physical scale of the microchannels due to the stretch or compression. The viscoelastic properties of four polymers are researched systematically by the dynamic oscillation shear test, as well as the variation of viscoelastic properties with the characteristic scale. The experimental results show that polyamide (PA), thermoplastic polyurethane (TPU) and polylactic acid (PLA) all exhibit the viscosity dominant characteristics of loss modulus greater than storage modulus with the angular frequency varing from 1—100 rad/s. While polypropylene (PP) displays the elasticity-dominated characteristic at high angular frequencies. Both storage modulus and loss modulus decrease with the drop of characteristic scale. In the process of characteristic scale changing from 1000 μm to 250 μm, the elastic effect on the three polymer melts including polyamide, polyurethane and polypropylene are more sensitive to micro-scale changes than the viscosity effect. The difference between the change rate of storage modulus and that of loss modulus is 5.8%, 4.2% and 2.6%, respectively. The viscosity effect of polylactic acid melt on micro-scale changes is basically the same as the elastic effect. The change rate of loss modulus is only 0.3% higher than that of storage modulus. The difference of molecular chain characteristics of polymers leads to different change rates of storage modulus and loss modulus with characteristic scale. The order of sensitivity for polymer melts viscoelasticity to micro-scale changes is polyurethane melt, polyamide melt, polypropylene melt and polylactic acid melt, of which the change rates of viscoelastic characteristic parameters are 28.6%, 22.6%, 20.6% and 19.45%, respectively.

    Study on structure optimization of heat exchanger and evaluation index of heat transfer performance
    Xiufeng LIU, Shi ZHANG, Zhijie ZHOU, Hao ZHENG, Chengze WANG, Hongyuan SHI, Mengjie LI
    2020, 71(S1):  98-105.  doi:10.11949/0438-1157.20191189
    Abstract ( 34 )   HTML ( 1)   PDF (860KB) ( 23 )  
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    There are some problems in the cooler of a launch vehicle. Firstly, the pressure loss of the shell side is large. Secondly, the segmental baffle structure makes the working substance flow in Z-shape. It is easy to form a dead zone behind the baffle, which promotes scaling on the shell side and reduces the overall heat transfer performance of the heat exchanger. Two heat transfer enhancement schemes for shell-side structures are proposed in this paper. The first scheme is to reduce the number of segmental baffles and increase the baffle spacing. The second scheme is to replace the original baffles with helical baffles. In order to verify the accuracy of the thermodynamic design method adopted in this paper, the thermodynamic design method of segmental baffle and helical baffle shell-and-tube heat exchangers are verified according to the experimental results in literature. The results show that the deviation between the experimental results and the calculated data obtained by the thermodynamic design method in this paper is within 37%, which meets engineering requirement. According to different optimization parameters, the optimization results are different. There is basically a following rule: the optimal design can reduce the total pressure drop on both shell and tube sides of heat exchanger, but its heat transfer performance decreases at the same time. Therefore, a comprehensive index is needed for evaluation. In this paper, the ratio of heat transfer Q to power consumption caused by flow resistance of heat exchanger is proposed as a comprehensive performance evaluation index. This index indicates that exchanging heat quantity obtained by heat transfer system per unit pump power. The larger the value, the better the economy. After calculation, it is found that the comprehensive evaluation index of the optimal scheme is increased by about 22.2% compared with the original scheme.

    Recurrence analysis of pressure fluctuations inclapboard-type internally circulating fluidized bed
    Bing ZHANG, Liping WEI, Haipeng TENG
    2020, 71(S1):  106-113.  doi:10.11949/0438-1157.20190876
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    The complex and unclear effects of fluidization and solid circulation within a clapboard-type internally circulating fluidized bed on the pressure fluctuations needs to be further investigated to clarify the basic mechanism. The present work measured the pressure fluctuation signals at different gas velocity ratios, and analyzed which by time domain and recurrence analysis methods. The characteristic parameters of standard deviation, recurrence rate, determinism and Shannon entropy were obtained. It was observed four states of no circulation, bubbling circulation, transition circulation and turbulent circulation with an increase in superficial gas velocity ratio. The four circulation states can be identified by the standard deviation of the pressure pulsation signal, the black-and-white structure proportion of the recurrence plot and recurrence characteristic parameter. Recurrence characteristic parameters show good linear relation in different circulation regions,which can be used to characterize the circulation states of the internally circulating fluidized bed system.

    Heat and humidity coupling non-steady state transfer model of multi-layer wall with additional air layer and its verification
    Xueqiong HE, Huibo ZHANG, Guojun YU, Chengnan SHI
    2020, 71(S1):  114-119.  doi:10.11949/0438-1157.20191272
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    In order to predict the temperature and humidity distribution and dynamic change of multi-layer wall with additional air layer accurately, the transient coupling transfer law of heat and humidity in porous media wall is studied. Based on Luikov, Fick s law and other basic transfer theory, the transient coupling transfer control equation of hot and wet air in the wall is derived. Through the improvement of the driving potential of the governing equation and the coefficient of the equation term, taking the air moisture content and temperature as the driving potential, the coupled heat and humidity transfer instability model of the building porous media wall is established. The MATLAB simulation program is designed by using the implicit difference scheme of finite volume method. The corresponding initial conditions and boundary conditions are set up to calculate the distribution of temperature, humidity, heat transfer and moisture transfer with time in the multi-layer wall with additional air layer. Finally, the accuracy and feasibility of the model are verified by comparing the simulation results of the new model with those of WUFI software.

    Characteristics of ice storage based on new type of flat micro heat pipe arrays
    Zichu LIU, Zhenhua QUAN, Yaohua ZHAO, Heran JING, Mengliang YAO, Xin LIU
    2020, 71(S1):  120-128.  doi:10.11949/0438-1157.20191143
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    This study experimentally investigated a new type of ice storage device (ISD) based on flat micro heat pipe arrays (FMHPAs). The structure and working principle of device were explained in details, and test rig was built. The applicability of FMHPAs as the core heat transfer element was experimentally verified, the characteristics of temperature distribution, cold storage power, cold storage capacity and cold storage density of ISD based on FMHPAs with different boiling temperature working fluids (R141b and acetone) are compared and analyzed. The results showed that ISD based on FMHPAs presented well performance. In the same time, the average cold storage power of FMHPAs with R141b and acetone was 0.14 kW and 0.187 kW, respectively, and the cold storage capacity per unit mass was 139.22 kJ·kg-1 and 184.33 kJ·kg-1, respectively. The cold storage density of ISD based on FMHPAs with R141b and acetone was 22.54 J·K-1?kg-2 and 17.61 J·K-1?kg-2, their performance better than ISD based on circular heat pipe.

    Working pressures on performance of ultrasonic atomization liquid desiccant dehumidification system
    Zili YANG, Caiyun GAO, Feiran GONG, Xuyun YU, Yun YU, Tianxun CAI
    2020, 71(S1):  129-135.  doi:10.11949/0438-1157.20191134
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    The effect of working pressures on the performance of the liquid desiccant dehumidification system was studied in this work. The ultrasonic atomization liquid desiccant dehumidification system (i.e., UADS) was taken as the prototype while a model based on the mass balance, the energy balance of the atomized solution dehumidification process was employed to simulate the performance. It was found that the dehumidification performance of the UADS system increases significantly with the rise of working pressure. In particular, when the air inlet temperature climbs, the facilitating effect of raising working pressure on the dehumidification efficiency becomes more significant. Meanwhile, a more significant promoting effect from the working pressure on the moisture removal rate was also presented with the rise of the inlet humidity ratio of the airstream, while its effect on improving the dehumidification effectiveness was weakening. In addition, the dehumidification performance tends to be more stable with the rise of the working pressure and less affected by the inlet conditions of the airstream. This study may help in clarifying and promoting the performance of the liquid desiccant dehumidification system under different working pressures.

    Forced convective heat transfer around spherical aerostat based on M-L transition model
    Houju PEI, Yanlong JIANG, Hong SHI, Yonglong CUI, Changdong CHEN, Xiaohui QIAN
    2020, 71(S1):  136-141.  doi:10.11949/0438-1157.20191105
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    The forced convective heat transfer is an important aspect of the thermal control of near-space aerostats and it is well known that the flow state (laminar or turbulent) has a significant impact on it. Currently, most numerical studies on forced convective heat transfer are conducted using the Reynolds-averaged Navier-Stokes equations, for example, the Spalart-Allmaras (SA) model, k-ε model, k-ω model, and the shear-stress transport k-ω model. However, these turbulent models consider the flow state as a fully developed turbulence and the transition process is not taken into account, which may lead to imprecise simulation results. Therefore, an appropriate method is needed to simulate the transition process. In this study, the M-L transition model is used and its applicability is verified by comparing the pressure coefficient around a spherical aerostat obtained from different turbulent models with those from experimental data of the literature. The numerical simulation is carried out using the fluid dynamic software CFX with the Reynolds number ranging from 106 to 108. The average Nusselt number is obtained and a new correlation of Nu for the forced convective heat transfer around a spherical aerostat is proposed.

    Combined convective heat and pollutant removals in enclosures with different vented slots
    Lei WANG, Fuyun ZHAO, Yang CAI, Weiwei WANG, Yunhe WANG, Guobiao YANG
    2020, 71(S1):  142-148.  doi:10.11949/0438-1157.20191091
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    A numerical investigation of displacement ventilation on a heated and polluted strip within a partially open enclosure, having various locations of airflow inlet and outlet, is considered. The effects of different governing parameters on the fluid flow, heat and mass transfer were analyzed systematically. Results illustrated that the different arrangements of airflow inlet and outlet exhibit the dual effects on heat and mass transports and the radiuses of heat and mass dissipation within the enclosure. Both heat and mass transfer rates present larger values for the locations of inlet and outlet placed at the vertical sidewalls while they presents smaller radiuses of heat and mass dissipations for inlet and outlet placed at the two vertical and the top sidewalls, respectively. Results could be beneficial for heat and pollutant removals from the electronic boxes or building enclosures.

    Coupled flow and heat transfer characteristics of piezoelectric fan with cross flow
    Xinjun LI, Weiwei CHEN, Shihua LU
    2020, 71(S1):  149-157.  doi:10.11949/0438-1157.20191080
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    Piezoelectric fan is a solid-state device which generally consists of a patch of piezoelectric material and a flexible blade. It employs the reversed piezoelectric effect to make the piezoelectric patch expand and contract periodically, driving the attached flexible blade to oscillate at the same frequency. Due to the oscillatory motion of flexible blade, the neighboring fluid is periodically excited and thus a pseudo-jet or streaming flow is produced shedding along the fan tip. On account of its some features, such as simple structure, low power consumption, and easy controllability, piezoelectric fan has recently gained much attention in the practical applications, such as electronics cooling, energy harvesting, biomimetic robotic propulsion, etc. Innovation on heat transfer enhancement with active flow control technology is a frontier issue aspect facing to the engineering thermal science. The effects of α (the angle between vibrating direction and cross flow direction) and u (cross flow velocity) on the amplitude of a single piezoelectric fan have been tested by using Laser Doppler Vibrameter (LDV). Three-dimensional unsteady flow and heat transfer characteristics driven by single piezoelectric fan arranged normally to the heated surface with different β (the angle between piezoelectric fan center line and cross flow direction) was per-formed by using dynamic meshing scheme. The displacement of the vibrating fan was determined from vibration test by using LDV. An experimental test for the local convective heat transfer coefficient distribution was also made by using infrared camera. The results show that aerodynamic loading from cross flow gets minimum and the amplitude of the piezoelectric fan is maximum when α equals 90°. When β equals 90°, the vortical structures excited by the coupling effect of piezoelectric fan and cross flow impacts the heated surface, and the shed-ding vortex is easier to be broken down in downstream region in relative to the other cases. In this condition, the local convective heat transfer in fan-tip vibration envelope is effectively enhanced, and the coupled heat transfer performance is 2 times larger than β=45° and 135°. The cycle-averaged local heat transfer coefficient distribution obtained by tested is well consistence to the numerical simulation.

    Analysis of heat and mass transfer characteristics during energy discharging in membrane energy accumulator
    Surui SUN, Dechang WANG, Jincui ZHANG, Zhen LIU, Yanhui LI
    2020, 71(S1):  158-165.  doi:10.11949/0438-1157.20191209
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    Concentration difference nondestructive energy storage can convert heat energy into the chemical potential energy of the solution. It can be used in solar lithium bromide absorption refrigeration system to improve the working stability of the system effectively. However, when the concentration of the solution is too high or the operating temperature is too low, it s easy to precipitate and crystallize, which will cause difficulty in putting energy. The membrane energy accumulator can solve the problem that it is difficult to release energy when crystallization occurs in the lithium bromide concentration difference accumulator. In order to analyze the internal heat and mass transfer characteristics of the membrane energy accumulator, the experimental test system of heat and mass transfer in the energy release process of the membrane energy accumulator is set up. And the mathematical model of heat and mass transfer of the membrane energy accumulator applied in the solar absorption refrigeration system is established. The CFD software is used to solve the three dimensional mathematical model. Comparing the calculated results with the experimental results, the mass transfer deviation of the water vapor molecule is less than 6%, and the solution temperature deviation is less than 15%, the reliability of the unsteady mathematical model is verified and the model is used as an analytical tool for heat and mass transfer in the energy release process of the membrane energy accumulator. According to the experimental and simulation results, the average mass transfer efficiency of 70% MS (mass fraction lithium) bromide solution is improved by 44.03% compared with 60% MS solution. When the evaporation temperature increases from 4.5℃ to 12.3℃, the average mass transfer efficiency will increase by 108.34%. And the mass transfer efficiency is improved by 40.77% with the decrease of effective length from 80 mm to 30 mm. The average mass transfer efficiency of water vapor can be improved by increasing the initial concentration, evaporation temperature, or reducing the effective length of the membrane channel.

    Performance of condenser duct under flight condition of a certain transport aircraft
    Hang ZHANG, Liping PANG, Ying WANG
    2020, 71(S1):  166-171.  doi:10.11949/0438-1157.20191093
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    The condenser used in evaporation circulation refrigeration system of a transport aircraft was studied. The difference of evaporation circulation refrigeration system working environment among transport aircraft, helicopter and small civil aviation aircraft was analyzed. Star CCM+ software was used for simulation modeling, through the fluid simulation analysis to the condenser air duct, the causes of the pressure failure of the evaporation circulation refrigeration system under the flight condition of the transport aircraft were described, the condenser air duct optimization scheme is put forward. Computational fluid dynamics (CFD) is used to verify the effectiveness of the optimization scheme. Finally, flight verification was carried out on the transport aircraft.

    Discussion on method of engineering computation of plate-fin heat exchanger pressure characteristic
    Pengcheng HE, Li ZHUANG, Liang HU, Gang LIU, Ruiqi WANG, Yaqiang BAO
    2020, 71(S1):  172-178.  doi:10.11949/0438-1157.20191096
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    Heat exchanger is the fundamental equipment of industry, which is important for the air vehicle, widely used in engine and ECS subsystem which is needed for it. The heat exchangers are usually used for passenger safety and comfort, which is also the important device for other equipment to keep normal and efficient work. The references of heat exchanger design and hydrodynamics have been contrasted and analyzed, some concepts and definitions are different from each other, the engineering calculation expressions of pressure characteristic of plate-fin heat exchangers have been put forward on the basis of hydrodynamics. One type of offset strip fin has been chosen for air-air heat exchanger, the one-pass and two-pass heat exchanger was set, which contained sudden expansion and contraction and 90°elbow and 180° elbow for the local pressure drop computation, the heat transfer is not considered, the Halton sequence is used for quasi-Monte Carlo, which is for heat exchanger at some temperature and pressure and Re outlet conditions computation, the probabilistic analysis is worked for the conclusions. As the two kinds of calculation examples shown, the header pressure loss and drop are little part to total heat exchanger pressure drop at most conditions, and the most probability density is about 0.05, the ratios of the total pressure drops to outlet pressures are very little, the constant pressure can be used for calculation of the fluids property.

    Design and experimental study on constant humidity relic showcase using Stirling cryocooler
    Ning WANG, Xuejun ZHANG, Yang ZHAO, Zhihua GAN, Chunwei ZHANG, Meng YU
    2020, 71(S1):  179-186.  doi:10.11949/0438-1157.20191100
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    The influence of relative humidity on cultural relics is significantly important in the preservation of cultural relics in museums. Considering the disadvantage of low cooling capacity in the semiconductor cooler which is widely used in small relic showcases currently, and the advantages of Stirling cryocooler, such as large cooling capacity, long service life, safety and reliability, etc., a novel constant humidity relic showcase using a Stirling cryocooler is designed and built to achieve the precise regulation of relative humidity in the microenvironment. In this device, the cold head of the Stirling cryocooler is placed in an optimal-designed water tank to control the water temperature, and the air humidity in the showcase is controlled by the direct contact between air and water for heat and mass transfer. The results show that the heat transfer efficiency between cold head and water can be greatly improved by using heat sink and circulating water pump. Appropriate fan control strategy can effectively improve the humidity control speed, maintain the humidity stability and reduce the system energy consumption. The relative humidity in the showcases can be adjusted continuously from 45.0% to 65.0% under the premise of being stable.

    Cockpit thermal control performance of new helicopter heat pump air conditioning system
    Kun LUO, Xiaodong MAO, Liping PANG
    2020, 71(S1):  187-193.  doi:10.11949/0438-1157.20191136
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    The helicopter often faces low temperature environment in the flight process, in order to ensure the safety of the pilots and equipment, the cockpit needs to be heated. The traditional environmental control mode of engine bleeding air will cause engine compensation, the application of heat pump air conditioning in helicopter environmental control system can reduce compensation while meet the demand of helicopter cooling and heating, the heat pump air conditioning system takes lube oil waste heat as heat source, and heat the cockpit with heat pump cycle. However, the operating temperature range greatly limits its application in helicopters. Therefore, a new type of helicopter heat pump air conditioning system with waste heat recovery is proposed, and the transient response of cockpit temperature and system performance of the system are studied by establishing the dynamic simulation model of the system. The results show that the new heat pump air conditioning system can meet the heat demand of helicopter in low temperature environment, and its heating capacity and heating efficiency are higher in the working temperature range. The low temperature performance of the system is improved, and the adaptability of helicopter in low temperature environment is significantly improved.

    Numerical analysis on aerodynamically generated sound dipole source characteristics of shunt T-elbow
    Yalin LIU, Ke WANG, Lei ZHAO
    2020, 71(S1):  194-203.  doi:10.11949/0438-1157.20191145
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    To explore the generation mechanism of airflow regenerative noise caused by the presence of local components such as T-elbow in duct systems and suppress it from the source, the distribution of aerodynamically generated sound on the inner surface of the local component pipe segment represented by the T-elbow pipe were obtained by using finite element method (FEM) and computational fluid dynamics (CFD) method jointly. The strengths and distributions of the aerodynamic sources on inner surface of T-elbows with different inclination angle of branch pipe and different airflow rate ratio of the branch pipe were investigated. Results show that the dipole source caused by the turbulent motion dominates the noise within the pipeline when the airflow through the T-elbow,and the main noise sources are located along the branch pipe. An inclination angle of 30° at the branch inlet can weaken the sound source intensity to the greatest extent and reduce the sound energy transmitted by the sound wave. A change in the flow rate ratio of the branch pipe can not cause the main positions of the aerodynamic sound source to change, but may bring about the change in intensity of sound source accordingly. The changes in the inclination angle and in flow rate ratio may lead to the change of unsteady vortex motion of the flow in the pipeline, thereby affecting the surface dipole source intensity and noise propagation.

    Parameter design of aircraft fuel regeneration cooling thermal management system
    Weiwei CHEN, Xiande FANG, Shihua LU, Fujian LIN, Ye ZHANG
    2020, 71(S1):  204-211.  doi:10.11949/0438-1157.20191223
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    The scheme of hypersonic vehicle integrated thermal management system based on the aviation fuel regeneration cooling technology was discussed by considering the service environment of aircraft and the design requirements of the mass and geometric size of the thermal management system. According to different heat load types and heat transfer modes, together with the newly proposed in-tube heat transfer correlation under supercritical pressure for hydrocarbon fuels, the heat transfer parameter design methods for the two types of heat transfer equipment in aircraft thermal management system were given. The main functional modules of the aircraft thermal management system were created and encapsulated by using the graphical interactive interface of MATLAB/SIMULINK platform. Taking the typical RP-3 aviation kerosene as an example, the parameter design process of the thermal management system with aviation fuel as heat sink was realized.

    Influence of airborne cold source parameters on evaporative cycle system performance
    Ruiqi WANG, Zanjun GAO, Hua YANG, Wenchao HU, Hongbo ZHAN
    2020, 71(S1):  212-219.  doi:10.11949/0438-1157.20191274
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    In order to study the characteristics of airborne evaporation cycle system, this paper is based on the existing equipment and conditions of laboratory, the research object is the airborne evaporation cycle system and the working medium is R134a. By controlling the speed of the compressor and the opening degree of the electronic expansion valve, the temperature and flow rate of the cold source are adjusted respectively. In this way, we can investigate the influence of the temperature and flow rate of the cold source on the compressor inlet refrigerant superheat, outlet temperature of the heat source and refrigerating capacity. The results show that under the test conditions in this paper, the effect of cold source antifreeze inlet temperature on system performance is obvious. As the cold source inlet temperature increases, the compressor superheat decreases gradually and the heat source outlet temperature increases obviously. However, the influence of cold source flow rate on system performance is not significant. Based on experimental data, a simulation model of evaporator is established. Applying the model to the evaporation cycle system model, comparing the experimental data with the simulation data, it can be seen that the simulation model of the evaporator is accurate and reliable, and can be used to simulate the performance of the evaporator.

    Analysis of heat transfer performance of copper-water heat pipe based on nano enhanced-PCM
    Dongmin TIAN, Yanpeng WU, Fengjun CHEN
    2020, 71(S1):  220-226.  doi:10.11949/0438-1157.20200113
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    In this paper, the solid suspension of lauric acid with different mass fraction of nano-alumina particles was prepared based on magnetic stirring and ultrasonic shock processing, and its thermal conductivity was tested. By means of the coupling between phase change material and the adiabatic section of the ordinary heat pipe, the temperature of each part of the heat pipe under different heating modes was measured, and the performance of the heat pipe was analyzed. The results show that when lauric acid is wrapped around the adiabatic section of the heat pipe, the temperature of evaporation section can be effectively reduced. The thermal conductivity of metal oxide nanoparticles was enhanced by adding appropriate concentration of metal oxide nanoparticles. The cooling performance of the heat pipe increased with the concentration of alumina nanoparticles in lauric acid. With the increase of concentration, the effect increased at first and then decreased. The mass fraction was the optimal concentration of 1.0%. Compared with the coupling module of pure lauric acid and ordinary heat pipe, adding 1.0% alumina particles can reduce the evaporation temperature by 10%, reduce the fan energy consumption up to 60%, and store nearly 27% of the input power during heating.

    Effects of different propeller blades on gas-liquid two-phase mixing characteristics in stirred reactor
    Yibin LI, Yajuan SONG, Xiaohui DAI, Zhenggui LI
    2020, 71(S1):  227-235.  doi:10.11949/0438-1157.20191315
    Abstract ( 24 )   HTML ( 1)   PDF (1159KB) ( 18 )  
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    A stirred reactor is a device that supplies mechanical energy to a stirred medium by obtaining a suitable flow field. It is widely used in industrial production, especially in the chemical industry, and many chemical production applications are more or less affected by the effect of stirring. Due to the lack of data on the design parameters of propeller blades at home and abroad, the profile of propeller blades is poor, and the stirring performance needs to be improved. In order to study and compare the stirring effect of several propeller blades, the propelling blade of the stirred reactor is taken as the research object, and polymerization medium of the mixing reactor is simplified to water and gas. First, the propeller blades are designed according to the design parameters. Four different types of propeller blades are designed by using different helix angles and contour shapes. Then, three-dimensional diagrams of the four propelled stirred reactors are drawn and unstructured meshing is performed according to the two-dimensional diagrams. Finally, the internal flow characteristics of the four propelled stirred reactors were simulated and analyzed by using multiple reference frames, VOF multiphase flow models, and RNG k-ε turbulence models. When the speed is 400 r/min, we qualitative analyze the distribution and uniformity of radial velocity and the mixing degree through comparing radial velocity cloud graph and the variation of gas volume fraction cloud graph from 0 to 18 s (including 0.6 s, 6 s, 12 s and 18 s). Besides we also define the dimensionless gas volume fraction and axial velocity, so 0 to 18 s (including 0.6 s, 6 s, 12 s and 18 s) hybrid rate,distribution of the gas volume fraction and the rate of change of the axial velocity are quantitative analyzed. According to the results of numerical simulation, the mixing characteristics and mixing degrees of the four types of propelled stirred reactors were compared. We can draw the following conclusions the asymmetric blades with variable spiral angle (FDC-450-γ) has a more uniform flow rate, the mixing rate is faster and the mixing degree is better. In this paper, four different propeller blades are selected for comparison and analysis, which lays the foundation for subsequent research and engineering practice.

    Analysis of principle, performance and applicability of indirect evaporative water chiller
    Jianpei CHANG, Xiang HUANG, Miaomiao AN, Zhaoyang LI
    2020, 71(S1):  236-244.  doi:10.11949/0438-1157.20191210
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    The structure types and working principle of evaporative water chillers are summarized. Analysis of cold water production by evaporative cooling through the psychrometric charts, theoretical and experimental results verify that the indirect evaporative cooling on the wet channel side is not adiabatic direct evaporative cooling. According to the performance test analysis of the indirect pre-cooling evaporative water chillers, the wet bulb efficiency of several types of to indirect evaporative coolers are between 41% and 92%. Vertical tube, plate tube and dew point indirect evaporative coolers are more efficient than horizontal tube indirect evaporative coolers, indirect pre-cooling evaporative water chillers can produce cold water to reach sub-wet bulb temperature. In addition to the influence of the efficiency of the indirect evaporative cooler, the production of water temperature is also affected by the gas-water ratio in the padding tower and the external heat source in the padding tower. Data center air conditioning system with indirect pre-cooling evaporative water chillers, mechanical refrigeration chillers, ethylene glycol natural cooling as cold source. The time of evaporative water cooling and the natural cooling of ethylene glycol in Urumqi, Beijing, and Shanghai are 8736, 6261, and 4708 h, respectively. Compared with mechanical refrigeration, the annual energy saving rate is 62%, 53%, and 46%, respectively.

    Freeze-drying monitoring technology of cultural relics based on infrared temperature measurement
    Shaozhi ZHANG, Yang LI, Yiyang XU, Youming ZHENG, Tian LUAN, Heng LU
    2020, 71(S1):  245-251.  doi:10.11949/0438-1157.20191180
    Abstract ( 18 )   HTML ( 1)   PDF (1269KB) ( 7 )  
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    Many saturated cultural relics unearthed in the south need dehydration. The application of freeze-drying technology can effectively eliminate the cracking caused by the surface tension of liquid water. The material temperature is a process parameter that needs to be strictly controlled during the freeze-drying process. Due to the indivisible and irregular shape of cultural relics, the temperature in the different area of cultural relics is not uniform, resulting in inconsistent freeze-drying progress. In order to guarantee the success of the freeze-drying process of large-scale and multitudinous cultural relics, saturated woody cultural relic is taken as sample, infrared temperature sensor and thermal imager are combined together to monitor temperature of the freezing process of cultural relics. The results show that the infrared temperature sensor is very sensitive to the change of surface temperature of the sample, and can effectively track the dynamic process of temperature, but the accuracy of temperature measurement will be affected by the change of sample emissivity and environmental fluctuation. The infrared camera can achieve high measurement accuracy by calibrating the emissivity, and the temperature distribution map can be used to screen the highest/lowest temperature region on the entire surface of the sample. After the analysis of the temperature data, the surface temperature is low when the sample is close to the heat exchanger end of the chamber, and the surface temperature is high near the position of the door, besides, the upper surface temperature of the sample is slightly lower than the side temperature of the sample. The infrared temperature measurements are anticipated to give hints for the control of freeze-drying equipment, thus to reduce the risk of freezing drying failure, and relieve the workload of cultural relics protection staffs.

    Separation engineering
    Preparation of coaxial electrospun zein nanofiber film embedding sodium lignosulfonate for enhanced adsorption of heavy metal ions
    Junyuan WU, Weizhi HUO, Zhiqiang LI, Jiaheng ZENG, Yanbin JIANG
    2020, 71(S1):  252-260.  doi:10.11949/0438-1157.20191063
    Abstract ( 25 )   HTML ( 0)   PDF (1901KB) ( 10 )  
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    In order to fabricate nanofiber film with enhanced adsorption capacity for heavy metal ions, the coaxial electrospinning was utilized to embed sodium lignosulfonate (SLS) in electrospun zein fibers. The process parameters were optimized, i.e. the electrospinning voltage is 14 kV and the core-to-sheath flow rate ratio is 1∶1. The TEM results indicated that SLS was embedded in electrospun zein films successfully. However, its loading capacity, encapsulation efficiency and loss ratio were influenced by the pH of solution. The results of metal ion adsorption tests indicated that SLS enhanced adsorption capacity of Ni2+, Zn2+ and Cd2+, among which Zn2+ is the most significant. The pseudo-second-order model was more suitable to describe the adsorption. Furthermore, the adsorption capacity of these three metal ions increased with increasing pH of the solution under acidic conditions.

    Experimental analysis of low pressure water permeability of single channel ceramic membrane tube
    Da TENG, Tielin LI, Ang LI, Liansuo AN, Guoqing SHEN, Shiping ZHANG
    2020, 71(S1):  261-271.  doi:10.11949/0438-1157.20200067
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    As a porous medium, inorganic ceramic membrane has the advantages of high separation efficiency, acid resistance and alkali resistance. It is regarded as a research hotspot in the fields of seawater desalination, wastewater treatment and gas separation. In this paper, Al2O3 tubular single channel ceramic membrane material is used to construct membrane module. Taking tap water, flue gas condensate and desulfurization wastewater of coal-fired power plant as examples, the permeability experiment of membrane module under low transmembrane pressure difference is carried out. The influence of membrane structure parameters, transmembrane pressure difference and water temperature on permeate flux and permeate water quality is studied, and the mechanism process of membrane pollution is also discussed and analyzed. The experimental results show that the structural parameters of the ceramic membrane tube are the key factors, the permeability flux increases linearly with the increase of pressure under the low transmembrane pressure difference, and the concentration polarization phenomenon is not found. The change of water temperature affects the permeability flux by changing the viscosity, and the permeability flux decreases when the water quality is poor, the pore diameter of the ceramic membrane tube affects the permeability flux. As the core element of permeable water quality, microfiltration and nanofiltration membrane have obvious effect on improving the content, turbidity and chroma of suspended solids, but have little effect on the salinity and conductivity. From SEM, it can be seen that the deposition and bridging of pollutants on the surface or inside of membrane will lead to serious membrane pollution. It is of great significance to fully understand the key factors affecting the permeability of ceramic membrane tubes and the mechanism of pollutants, so as to improve the technical level of membrane separation.

    Water vapor adsorption performance of composite adsorbent MWCNT/MgCl2
    Huizhong ZHAO, Min LEI, Tianhou HUANG, Tao LIU, Min ZHANG
    2020, 71(S1):  272-281.  doi:10.11949/0438-1157.20190915
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    Composite adsorbent MWCNT/MgCl2 was prepared by grinding multi-walled carbon nanotubes (MWCNT) and anhydrous magnesium chloride (MgCl2) with mass fraction of 30%, 40% and 50% respectively. Digital scanning electron microscope (SEM) was used to observe the structure appearance of the composite adsorbent. The thermal conductivity of the composite adsorbent was measured by Hot Disk thermal constant analyzer. Representative temperature and humidity were selected by constant temperature and humidity box to test the water vapor adsorption performance of the composite adsorbent under different working conditions. The pseudo-second order kinetic model was used to fit the experimental data under the condition of 25℃, 50% RH. And the isothermal and hygroscopic curves of three samples were tested by Autosorb-IQ automatic gas analyzer under 25℃. The experimental results show that, under the same temperature and humidity conditions, the adsorption capacity of the composite adsorbent improved with the increase of MgCl2 mass ratios. The adsorption capacity of the composite adsorbent M1, M2 and M3 with the MgCl2 content of 30%, 40% and 50% under the condition of 25℃ and 50% RH is 0.62, 0.79 and 0.94 g/g respectively. When the constant humidity is 50% RH and the temperature changes from 15℃ to 35℃, the adsorption capacity of the composite adsorbent is affected by the dual effects of temperature and saturated water vapor pressure, which first increases and then decreases. When the temperature was fixed at 25℃ and the relative humidity increased from 50% RH to 80% RH, the adsorption capacity of the composite adsorbent greatly increased. Also, the composite adsorbent showed good adsorption ability at low temperature and low humidity of 35℃, 25% RH. When the relative pressure P/P0 was 0.3, the adsorption capacity of M1, M2 and M3 was 0.24, 0.25 and 0.30 g/g, respectively. With the increase of the adsorption relative pressure, the moisture adsorption capacity of the composite adsorbent also improved, reaching 3.54, 3.75 and 4.42 g/g, respectively. The preparation study of the composite adsorbent MWCNT/MgCl2 provides a basis for the study of the properties of the adsorbent, and has potential significance for the study of solar absorption air water intake.

    Process system engineering
    Mixture product design based on molecular surface charge density distribution and machine learning
    Haitao MAO, Lu WANG, Zhiying XU, Wancui XIE, Jian DU, Lei ZHANG
    2020, 71(S1):  282-292.  doi:10.11949/0438-1157.20190795
    Abstract ( 31 )   HTML ( 2)   PDF (1637KB) ( 14 )  
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    Modern business pays increasing attentions to mixture products due to its adjustable characteristics. For the design methods towards such kinds of products, the development of model-based design methods is faster than others, because of its efficiency and wide application. However, the models for some properties, like odor and color, with acceptable accuracy or general application range are still not available. Therefore, an application methodology of machine learning (ML) with molecular surface charge density distribution (Sdescriptors) for mixture product design is proposed in this study, where descriptors are employed to represent the product and ML is responsible for correlating them to the target properties, for the purpose of designing product directly. Specifically, machine learning model is expected to predict Sdescriptors of candidate products according to the assigned property value, and ingredients are screened out using Euclidean-based method according to the predicted descriptors. Finally, the properties of the candidate mixtures and its ingredients are verified by experiments. This methodology is introduced using a case study of mixture substitution fragrance design for cis-3-hexenyl propionate and two mixture fragrances are obtained ultimately. The odor properties of mixtures and physicochemical properties of their components are similar to the target, which highlights the effective of the proposed method.

    Study on energy storage of regional pipe network system based on time-of-use pricing
    Xiaoyu GUO, Zhe TIAN, Jide NIU, Jie ZHU
    2020, 71(S1):  293-299.  doi:10.11949/0438-1157.20191155
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    The regional cooling system is mainly divided into three parts: source, network and users. The pipe network can not only link the source and users, but also realize energy storage. Therefore, the energy storage effect of pipe network can be used to realize the interaction between refrigeration station and power grid. Taking the refrigeration station of a industrial park located in Guangzhou as an example, this paper builds a regional cooling system based on Dymola platform and Modelica language. Based on time-of-use pricing, three control strategies are proposed based on the characteristics of heat storage and delay of pipeline network to explore the application of heat network in power response. Results show that, the effect of the network storage maintained at room temperature is 0.31 h. The use of pipe network heat reduce power consumption by 6.4% and 6.7% of electricity. Visibly network effect is an important resource in power grid demand response.

    Analysis of environmental control and thermal control for manned spacecraft
    Bin QI, Xixi DUAN, Rong A, Hongsheng JIANG
    2020, 71(S1):  300-306.  doi:10.11949/0438-1157.20191193
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    There is strong coupling between environmental control system and thermal control system of manned spacecraft in terms of heat and material flow. In the design stage, it is necessary to carry out integrated system simulation analysis, so as to predict and verify the system performance. A typical integrated environmental control and thermal control system model of manned spacecraft is built using system modeling and simulation methods, including crew module, air purification module, air supply and pressure regulation module, fluid loop module, etc. The performance of the system is analyzed. The simulation analysis was carried out for the manned flight conditions of three persons in 7 days. The results show that the parameters of temperature, humidity, pressure and oxygen partial pressure in the cabin can be controlled within the requirements of aerospace medical indicators by reasonable design. The simulation results of the environmental control system and thermal control system accurately predict the working process of the system, show the changes of the main parameters, and the results are reasonable, which verify the correctness of the simulation method and the system simulation model. By controlling the opening of the bypass valve in the outer loop of the fluid circuit, the temperature of the control point in the outer loop can be accurately controlled to ensure that the temperature and humidity in the cabin are within a reasonable range. In addition, the setting of temperature control point in the outer loop will affect the state of the environmental control system and thermal control system. By reasonably designing the temperature control point in the outer loop, the temperature and humidity in the cabin can be guaranteed to meet the requirements of aerospace medical indicators. The research results play an important role in the integrated design and optimization of environmental control system and thermal control system.

    Biomass moisture content prediction in fluidized bed dryer based on LSTM neural network
    Huangfeng FANG, Yaoyao LIU, Wenbiao ZHANG
    2020, 71(S1):  307-314.  doi:10.11949/0438-1157.20190692
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    As a common form of renewable energy with abundant reserves, environmental friendliness and easy access, biomass has aroused general interests in the field of energy research and utilization. Biomass moisture content is a significant factor for the efficient utilization of biomass resources, therefore drying becomes a necessary step before the biomass utilization.Fluidized bed has been widely used in the drying process due to its good heat and mass transfer characteristics. For the online monitoring of the biomass drying process, arc-shaped electrostatic sensor arrays along with a LSTM (long short-term memory) neural network are deployed to establish a neural network model for the prediction of biomass moisture content in the fluidized bed dryer. Experimental tests under different conditions are carried out on a lab-scale fluidized bed dryer to obtain data for model training and testing. Besides, the LSTM neural network model is determined through the optimization of the model parameters. Compared with normal RNN (recurrent neural network) model,the prediction results from the LSTM neural network model have smaller mean relative error, which can predict the biomass moisture content in the fluidized bed dryer with certain accuracy.

    Design and optimization of integrated thermal management system for high-speed aircraft
    Rong A, Liping PANG, Dongsheng YANG, Bin QI
    2020, 71(S1):  315-321.  doi:10.11949/0438-1157.20191197
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    Under the dual effects of aerodynamic heating and high-power electronic equipment heating, the advanced high-speed aircraft heat sink and energy demand are exponentially rising, which seriously restricts the function and performance of the aircraft. In order to improve system cooling and power supply performance and reduce engine performance loss, the optimization design of integrated thermal management system is studied. In this paper, based on the large heat load high-speed aircraft with Mach number (Ma)1—4.4, the optimization design for the three integrated thermal management systems is carried out to optimal match the fuel heat sink, the outer duct convection heat sink, the ram air and flight missions. The equivalent quality method was used to analysis, which equalizes the mass, energy consumption and gas source consumption to the fuel weight penalty, and defined as the objective function. The results reveal that when the Mach number is lower than 2, the outer duct air heat sink mode is more economical. However, with the increasing of the flight speed, the refrigeration cycle pressure ratio significantly increased, which cause the fuel weight penalty increased sharply. When the Mach number is 2—4.5, the fuel heat sink mode is more suitable. Its fuel weight penalty is mainly due to the increasing of flight speed. Compared with engine bleed air, rim air is more suitable for higher Mach number. Thus, for the cruise Mach number below 2, the integrated thermal management system equipped with “external duct bleed air heat sink and engine bleed air” earns less engine performance loss. For the cruise Mach number of 2—4.5, the integrated thermal management system equipped with “fuel heat sink and switchable engine bleed air/rim air” earns better engine performance.

    Research of multi-stage temperature control system in large-sized aircraft cabin zone
    Lulu SHI
    2020, 71(S1):  322-327.  doi:10.11949/0438-1157.20191188
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    The temperature control system of large-sized aircraft has both delay and delay of large cabin capacity and fast dynamic feedback of small cabin capacity. At the same time, the influence of the flow rate on the performance of the aircraft will also bring about temperature changes, which will increase the difficulty of system control. In order to keep the cabin temperature control in the comfort zone of large passenger aircraft, the traditional control system has some limitations, and more advanced control methods are needed. In this paper, a multi-stage temperature control structure is designed according to the temperature characteristics of cabin area. The design scheme of the anti-windup PID control model is used to control the system.The temperature control system has the speed of control, stability of hysteresis control and anti-interference ability. At the same time, the cold road control uses the speed of the four-wheel air circulation system to replace the component outlet temperature to control the temperature of the mixing chamber in the traditional control to avoid system failure caused by inaccurate measurement of the component outlet temperature sensor when icing and other phenomena occur in the system.

    Modeling and validating of air cycle machine in aircraft environmental control system
    Fanxin MENG, Jianing SUN, Yue ZHOU, Zanjun GAO, Dingbin CHENG
    2020, 71(S1):  328-334.  doi:10.11949/0438-1157.20191125
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    Mathematical models of compressor-turbine-fan air cycle machine were established in aircraft environmental control system. The simulation models of air cycle machine were developed. The performance test principles and procedures are put forward for the product and performance tests are carried out to obtain the performance data under design conditions. By comparing simulation results and experimental data for compressor pressure ratio and efficiency characteristics, turbine temperature drop, fan pressure rise, the simulation model was corrected and validated. Results show that the modeling method provided in this paper can calculate the performance of the air cycle machine accurately with the ±10% simulation error. The simulation precision meets the requirements of aircraft environmental control system engineering design and it is helpful to develop environmental control system and its components.

    Simulation and optimization of air supply system layout for special vehicle cabin
    Gang XU, Liping PANG
    2020, 71(S1):  335-340.  doi:10.11949/0438-1157.20191102
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    Because of its special function and closeness, special vehicles can not use the opening and closing of windows to control cabin ventilation like civil vehicles, drive special vehicles for a long time, the cockpit faces small space, less cold source, large heat load, lack of fresh air, and the external environmental conditions are complex. This requires the fine design of the air supply system for special vehicle compartments to meet the thermal comfort and thermal control needs of personnel and multiple devices, so it is necessary to optimize the ventilation system based on the cockpit characteristics of special vehicles to ensure the thermal requirements of the whole cabin. In order to make the heat exchange between the cockpit air supply and the heat source in the cabin as complete as possible and bring out more heat, this paper first establishes the three-dimensional physical model and simulation model of the typical cabin and crew for a special vehicle. The simulation and optimization analysis of air distribution for 10 kinds of air supply modes is carried out, and the multi-physical field of special vehicle cabin is obtained. The optimization of air distribution is carried out from two aspects: tuyere form and tuyere position. In the tuyere form optimization, a variety of tuyere combination forms are proposed and simulated respectively. Aiming at equipment temperature control, personnel thermal comfort and air age, the simulation results are evaluated by using evaluation function, and 10 types of air supply conditions are simulated. From the simulation results, based on the above multi-optimization objectives, the tuyere position optimization for the preliminary optimal air supply form is further carried out. On the basis of the optimization results of tuyere form, genetic algorithm is used to set the position parameters as optimization parameters, two evaluation functions are selected as the optimization objective functions, and the constraint conditions such as head and foot temperature difference are set to the optimization model. The simulation results are screened and the inverse optimization is carried out. Finally, the optimal tuyere position is obtained and the optimization of air distribution is completed. This study has certain significance for the study of limited space thermal comfort and air quality of fully sealed special vehicles.

    Simulation study on four-wheel booster refrigeration system
    Yue ZHOU, Helin ZHANG, Dingbin CHENG, Juncheng YIN
    2020, 71(S1):  341-345.  doi:10.11949/0438-1157.20191381
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    In this paper, the steady state simulation of four-wheel booster air circulation refrigeration system is carried out, the result of which is compared with the existing research data. Further, the temperature disturbance characteristics of the system is analyzed combined with the main system disturbance source. Simulation results show that when the temperature of the bleed air temperature or ram air disturbance occurs, the system temperature changes, the degree of which agrees with the disturbance degree. However the bleed air pressure disturbance will cause the system temperature to change greatly, that is to say, the bleed air pressure disturbance to the four-wheel booster air circulation refrigeration system influence is most intense. This paper provides reference for the design and optimization of the environmental control in the future.

    Surface and interface engineering
    Performance analysis of gas film of adaptive cylindrical seal
    Junjie LU, Wei ZHANG, Fangmin XIE, Yongfeng JIAO
    2020, 71(S1):  346-354.  doi:10.11949/0438-1157.20191025
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    An adaptive cylindrical gas film seal is proposed. Consider the problem of eccentric gas film convergence and define the abrupt change of the Rayleigh step to the gas film cycle, the relationship between the Reynold equation and the film thickness function is established, and the lubrication characteristics of friction pair are obtained. The results show that the gas bearing force is increase with speed and pressure, the leakage increases with increasing pressure but decreases with increasing speed. It is thus concluded that the internal pressure flow of the seal is dominant. Subsequently, the curved groove engraving technique is proposed, and the experiment is carried out. The results show that there are obvious scratches and wear in the chute groove, and the gas bearing force of chute groove is weaker than the straight groove, but the leakage of chute groove is smaller than the straight groove. It shows that the tangential flow of the chute groove is smaller than that of the straight groove, which results in the leakage of the chute groove is smaller than that of the straight groove. At the same time, the theoretical calculation model is agreeing well with the experimental results. The research results lay a theoretical foundation for the application of adaptive cylindrical gas film seals.

    Energy and environmental engineering
    Dehumidification characteristics of recirculated desiccant wheel dehumidification system under variable working conditions
    Wenxiang WU, Xiaoqu HAN, Zhijie ZHOU, Yu WANG, Daotong CHONG
    2020, 71(S1):  355-360.  doi:10.11949/0438-1157.20191224
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    The relative humidity of air is generally above 80% in the ship cabin. However, the people will feel uncomfortable and the immunity will decrease when the relative humidity of air is higher than 70% in the environment. Effective air dehumidification will improve the air quality in the cabin and ensure the normal navigation of the ship. According to the characteristics of the relative humidity of air in the ship cabin and the waste heat generated by the operation of the equipment, the air can be dehumidified by the rotary desiccant wheel. And the waste heat of the ship can be recovered and used as the regenerative heat source of the rotary desiccant wheel which has the characteristics of large dehumidification, high control precision, economic and environmental protection. So it s promising to apply the rotary desiccant wheel dehumidification air conditioning system to the ship for recovering the waste heat of the ship and improving the air quality of the cabin, in this way low energy consumption and efficient dehumidification can be achieved. Therefore, a regenerative recirculating dehumidification air conditioning system was proposed in the present work. The dehumidification characteristics of the system under different working conditions were quantitatively studied, and the effects of different cycle bypass coefficient (45%—85%), process air temperature (28—40℃), the relative humidity of process air (50%—85%) and regeneration air temperature (130—160℃) on the dehumidification performance of the system were obtained. The experiment results showed that the rotary desiccant wheel dehumidification air conditioning system proposed could efficiently improve the dehumidification ratio compared the conventional sea water direct cooling. Under the same cycle bypass coefficient, the dehumidification ratio increased with the increase of process air temperature, relative humidity of process air and regeneration air temperature. There existed optimal dehumidification ratios of the system, and the corresponding optimal cycle bypass coefficient was 50%—75%. It decreased with the increase of the process air temperature and the relative humidity, and increased with the increase of the regeneration air temperature.

    Photovoltaic and thermal performance of solar PV/T system with phase change material
    Chenyu ZHANG, Ning WANG, Hongtao XU, Jianfei ZHANG, Meng CAO, Talkhoncheh Fariborz Karimi
    2020, 71(S1):  361-367.  doi:10.11949/0438-1157.20191092
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    This paper based on the phase change heat storage and release characteristics of phase change material (PCM). The fatty acid PCM is filled in a collector equipped with metal fins to regulate the temperature of the photovoltaic (PV) plate. The performance of photovoltaic/thermal-PCM (PV/T-PCM) system under different intermittent thermal regulation strategy is analyzed. Results show that PCM can effectively alleviate the temperature fluctuation of PV cells. However, the temperature stratification phenomenon of PCM is still serious which restricts the utilization rate of PCM. A reasonable thermal regulation strategy plays an important role in preventing overheating of PV cells in PV/T-PCM systems and improving system performance. The data shows that the PV conversion efficiency can be increased by 3.4% and 2.6% respectively with the control of the Case 2 (control temperature is set to 45℃, the regulation time is 30 min) and the Case 3 (control temperature is set to 50℃, the regulation time is 30 min). On the other hand, the total efficiencies of the system in Case 2 and Case 3 are 90.8% and 84.45%, which are significantly improved compared with Case 1 (no regulation).

    Performance of direct-expansion photovoltaic/thermal(PV/T)-air source heat pump system
    Boyao DU, Zhenhua QUAN, Longshu HOU, Yaohua ZHAO, Haibo REN
    2020, 71(S1):  368-374.  doi:10.11949/0438-1157.20191150
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    With flat heat pipe (micro-heat pipe array) as the core component, a new type of PV/T-air collecting evaporator and direct-expansion PV/T-air source heat pump system were designed and built to realize the functions of year-round water heating, winter heating, summer cooling and year-round photovoltaic power production. Experimental study on the performance of heat pump system under the weather conditions from March to May in Beijing was carried out in different operating models (S, SA and A).The experimental results show that the COPS of model S, SA and A is 4.8, 4.2 and 3.8,the η of three models is 109.7%, 125.9% and 32.4% under typical working conditions, which means under the condition of solar irradiation, the performance of the multienergy complementary system in mode S and SA is better than that in mode A. The new heat pump system has a significant performance, and the experimental results provide basic data support for its application.

    Contrastive research of heating performance of direct expansion solar/air assisted heat pump system and air-source heat pump
    Kunru MA, Xuefeng LI, Siqi LI, Cuijuan GAO
    2020, 71(S1):  375-381.  doi:10.11949/0438-1157.20191138
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    In view of the fact that, during heating, the traditional air source heat pump when placed outdoors is very prone to frost, a new type of direct expansion solar / air-assisted heat pump was proposed, which can absorb solar energy as well as air energy at the same time. Due to this creation, namely, the combination of solar collector and heat pump evaporator, the frost issue can be effectively alleviated. To verify its performance, a new direct expansion solar / air-assisted heat pump system and an air source heat pump system were established. From Feb. 26th to Mar. 2nd, a 5-day practical test on the floor radiant heating of rural buildings was conducted in a village of Handan City. Then, based on the results, we conducted comparative analysis on the two systems’ heating performance, power consumption, and the change of COP. It is found that when the average outdoor temperature is 10℃, and the solar radiation reaches the peak of 571.5 W/m2, the heating capacity of the direct expansion solar / air-assisted heat pump increased approximately 70% and its total heating capacity of the day increased about 12% compared with the air source heat pump. And when the temperature is between 0℃ and 8℃, the COP can still reach 3.46, the heating needs can be basically met. Furthermore, we optimized the new type heat pump, and hopes to gradually promote its practical application in cold regions.

    Experimental investigation on energy-efficiency performance of temperature swing adsorption system for CO2 capture
    Bowen LIU, Shuai DENG, Shuangjun LI, Li ZHAO, Zhenyu DU, Lijin CHEN
    2020, 71(S1):  382-390.  doi:10.11949/0438-1157.20191075
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    Post-combustion CO2 capture (PCC) is considered to be an important technology for reducing carbon dioxide emissions owing to its easy retrofit to power plants. Chemical absorption, adsorption and membrane separation are typical mainstreams in PCC. In technological cluster of CO2 adsorption, temperature swing adsorption (TSA) is one of efficient methods. In recent years, the topic on energy consumption and energy efficiency of TSA is emerging as an urgent response to the possible large-scale deployment of CCS. However, most studies apply mathematical model and simulation method for performance assessment for TSA, without enough specific supports from experiment researches. To conduct an experiment-guided analysis on the energy-efficiency of TSA, a 4-step TSA apparatus was designed and developed. The separation and energy-efficiency performance are the main performance indicators in the analysis. Zeolite 13X-APG was employed in experiment and its selectivity of CO2 over N2 was obtained according to isotherms of two components measured experimentally. Four groups of experiment results were obtained for affect analysis from CO2 concentration, desorption duration, adsorption temperature and desorption temperature to the purity, recovery rate, specific energy consumption and second-law efficiency. The results show that the range of second-law efficiency is between 3.24% and 9.23% with the maximum recovery rate of 83.97% and purity of 94.70%. Increase of desorption temperature and CO2 concentration, decrease of adsorption temperature lead to the improvement of separation and energy-efficiency performance. Extending the desorption time benefits the separation performance. However, such longer operation time probably causes a bad performance, which may be propitious to the optimization of operation strategy for TSA system.

    Steady state performance of power generation/refrigeration combined system for new high speed vehicle
    Liang GUO, Heng LI, Liping PANG, Xiaodong MAO, Jingquan ZHAO, Xiaodong YANG
    2020, 71(S1):  391-396.  doi:10.11949/0438-1157.20191130
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    At present, the research of high-speed vehicle has become a hot issue in the field of aviation science at home and abroad. With the increase of speed, the traditional air heat sink can no longer be used as refrigerant of environmental control system alone. At the same time, the rapid increase of electronic equipment brings more heat load and more power consumption. Therefore, the power generation and refrigeration capacity become two major problems restricting the performance improvement of high-speed vehicle. Based on the basic air compressor refrigeration cycle and the existing fuel as the heat sink environmental control system, this paper proposes a new type of high-speed carrier power generation refrigeration technology, and makes a detailed analysis of its steady-state performance. This scheme can make full use of fuel as heat sink, effectively transfer airborne heat load to fuel when the fuel does not exceed the safe temperature limit, and finally send it to the engine for combustion. It can also realize the use of high-temperature and high-pressure air as power-driven power generation device to meet the power demand of high-speed carriers. Through detailed theoretical calculation and computer modelling and simulation, the research results show that under the conditions of 1.45 kg·s-1, 644℃ and 3.89 bar (absolute pressure), the power generation of the system can reach 200 kW by adjusting the parameters of each component of the system to ensure that the maximum fuel temperature does not exceed 150℃, and at the same time, the temperature of the cabin can be controlled at about 30℃ under 100 kW heat load. It satisfies the requirement of high-speed vehicle for electric energy and the control of heat load very well.

    Effects on performance of small water-source heat pump water heater with CO2 by refrigerant charge and determination of optimal value
    Dong WANG, Yaru LIU, Zhuo CHEN, Zunli KOU, Yuehong LU
    2020, 71(S1):  397-403.  doi:10.11949/0438-1157.20191098
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    On the bases of an existing water-source heat pump water heater with CO2 as a refrigerant, the optimal charge was calculated by different theoretical methods. The changes of system performance were studied with various refrigerant charges by a series of experiments and the optimal value was used to verify the accuracy of the theoretical one. The results indicated that there existed an optimal charge in a water-source heat pump water heater with CO2 as a refrigerant where the system yielded the best COPheat and the value was 270 g in the experiment system. If the refrigerant charge was reduced to 89% (230 g), COPheat would reduce by 10.8%, while 111% (300 g) charge reduced COPheat (coefficient of heating performance) by 2.6% and it could be concluded that the performance of such system was particularly sensitive to the insufficient charge. Moreover, the hot water yield increased with the increase of refrigerant charge, but the effect was not obvious when charge exceeded the optimal value. Comparing with the experiment result, it was found that both the experimental data method and the rated operating method could be applied in the studied water-source heat pump water heater system with the maximum error of 3.7%. This study may provide theoretical guidance on how to determine optimal refrigerant charge and how to maintain efficient operation of a small CO2 transcritical system.

    Environmental control system based on thermoelectric cooler
    Dongcai GUO, Qiang SHENG, Peng YANG, Jie XU, Ze WANG, Bo YANG, Jiaokun CAO
    2020, 71(S1):  404-410.  doi:10.11949/0438-1157.20191078
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    Space science experiments are an important work of the space station and scientific satellites, in some space science experiments, the temperature of environment exceeds heat sink temperature range, effective heating and cooling measures are required. Thermoelectric effect has high reliability and low complexity, which is applicable for temperature control in low gravity conditions. In this paper, the effect of thermoelectric cooling and heating at different fluid temperatures is analyzed, and the results show that the smaller difference between fluid temperature and aim temperature, the better effect of thermoelectric cooling and heating effect. The quantity of thermoelectric module decreases first and then increases with increasing current in the environment temperature cooling condition, and it is monotone decreasing in the heating condition. Since the cooling condition requires more thermoelectric modules than the heating condition, the quantity of thermoelectric module is determined according to the cooling conditions. Through the analysis of the environment temperature control system under different flow rates, it can be seen that the larger the flow rate, the higher efficiency of the heat exchanger, and the higher thermal load of the thermoelectric module. As the thermoelectric thermal load has greater impact than the efficiency heat exchanger on the whole system, the total efficiency is decreasing with increasing liquid flow rate. When the fluid temperature is close to the aim temperature, the total efficiency of the thermoelectric environment temperature control system is more than the efficiency of the thermoelectric module in an interval with specific temperature and flow rate. In this paper, performance analysis methods are provided for thermoelectric cooling and heating condition, which has important reference significance for the design of space station experiment temperature control system.

    Field investigation on human related VOCs in existing buildings in one university
    Yabin JIA, Xu ZHENG, Kai GAO, Jun GUAN, Pian WEI, Bing QI, Huiyan ZHENG
    2020, 71(S1):  411-416.  doi:10.11949/0438-1157.20190926
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    In order to study the influence of occupants on the indoor VOCs in universities, we conducted VOCs sampling campaign in 82 densely occupied classrooms and conference rooms in one university. The VOCs concentration levels and influencing factors were analyzed. The results showed that 29 human related VOCs species with high detection rate and higher concentration values were confirmed, including 9 kinds of aromatic compounds, 9 kinds of alkanes, 8 kinds of ketones and aldehydes and 3 kinds of alcohol esters and halides, and the concentration levels and I/O ratios of the main VOCs substances were obtained. Statistical analysis of the influencing factors showed that indoor occupancy rate, season and room type have significant effects on different VOCs species, in which seasonal factors have the highest degree of influence on target VOCs pollutants, followed by room type and indoor occupancy rate. This research can provide a scientific reference for further understanding of indoor VOCs pollution and control strategies in densely occupied buildings.

    Configuration analysis of integrated thermal management about high altitude long-endurance unmanned aerial vehicle
    Huicai MA, Yiling LIU, Xiaomin DANG
    2020, 71(S1):  417-424.  doi:10.11949/0438-1157.20191356
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    There are many subsystems such as power supply system, fuel system and environmental control system(ECS) in the high altitude long-endurance unmanned aerial vehicle(UAV).They are independence and also have correlations with each other on the demand and use of the thermal. The new configuration of integrated thermal management about high altitude long-endurance UAV is put forward and the research about the parameters matching among the systems has been done. The preliminary design of the major system compoments is presented and the mathematical models of the compoments are established, such as heat exchanger, reheater, condenser, compressor and turbine. The structure parameters for engineering have been obtained.The computer simulation system of the integrated air-conditioning pack and liquid cooling system is established on the Flowmaster platform. It is presented that the computer simulation results match with design objective very well. The new configuration can make the thermal be integratly used under different working conditions with the heat exchanger which is used to exchange the heat between the air-conditioning pack and liquid cooling system. The aircraft performance penalty is reduced,which can show the superior of the integrated thermal management configuration. As the system configuration optimization is completed with the integrated aircraft thermal management, the target radar cross section (RCS) of the stealth high altitude long-endurance UAV will also be reduced.

    Thermal flight time of fuel heat management system for high speed vehicle
    Xiaodong YANG, Liping PANG, Rong A, Liang JIN
    2020, 71(S1):  425-429.  doi:10.11949/0438-1157.20191117
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    At present, the airborne thermal load of high speed vehicle is increasing exponentially. But the temperature of the fuselage increases with the flight time due to the aerodynamic heating effect. These factors severely restrict the endurance of the high-speed vehicle and the working time of the electronic equipment. Fuel oil can be the preferred airborne heat sink because it is necessary to be carried liquid with large ratio heat capacity. The working temperature of fuel heat sink will be affected aerodynamic heating effect, consumption rate, flight time, comprehensively. In this paper, a fuel heat management system for high speed vehicle will be studied to analyze the influence of parameters design on the flight time. The dynamic characteristic equations were established for the fuel thermal management system. The concept of thermal fight time was further proposed to evaluate the flight time constrained by thermal load effect. The effects of the above factors and the design parameters on the fuel thermal management system were discussed in detail. The above work can provide a reference for the design and selection of the thermal management system for high speed vehicle.

    Calculation and analysis of soil source heat pumps intermittent heating operation time
    Gang WANG, Yan ZHAO
    2020, 71(S1):  430-435.  doi:10.11949/0438-1157.20191111
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    In order to make full use of soil heat energy, the relationship between heat supply, running time and system performance was studied. By establishing the hourly heat balance equation of the room, the calculating formula on room temperature change and time was derived. The average indoor temperature, heat pump running time, downtime, and heating running share were calculated by this model, and the simulation calculation and analysis of five operating schemes were carried out.


    in the calculation of underground coil length design, the heating running share should be calculated based on the heat pump unit s heat supply. When heat pump heat production is same, the time period (the sum of one running time and downtime) is small, the running time is short, the average water temperature of the underground coil outlet is high, and the heat pump operation efficiency is high, but as the time period becomes smaller, the average indoor temperature decreases, thermal comfort decreases. When the time period is the same, the heat pump unit s heat supply is bigger and the running time is shorter, the average water temperature of the underground coil outlet is higher, and the heat pump unit s efficient is higher. According to these characteristics, the heat source can be allocated in the form of an heat pump unit with a 100% heat load + an auxiliary heat source with 20%-30% heat load.

    Thermal management of airborne integrated environmental control system
    Desheng MA, Liping PANG, Xiaodong MAO, Sujun DONG
    2020, 71(S1):  436-440.  doi:10.11949/0438-1157.20191083
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    Using fuel as the main heat sink, and introducing liquid PAO and R134a as auxiliary heat sink, a new scheme for thermal management of environmental control system was proposed. The air compression refrigeration subsystem and the high-temperature PAO subsystem use air-PAO heat exchanger as the connection point and are coupled into the thermal management subsystem of cockpit and electronic cabin 1. The cryogenic PAO subsystem and the evaporator compression refrigeration cycle are coupled to the thermal management subsystem of the electronic compartment 2. The simulation models of main components such as air-liquid heat exchanger and liquid-liquid evaporator/condenser are established by combining mathematical calculation with computer modeling and simulation. The results show that under certain air inlet temperature and pressure conditions, fuel as the main heat sink can absorb a lot of heat, and the complementary heat of each subsystem can meet the temperature control of the cockpit and the electronic cabin, to ensure its stable and efficient operation.

    Multi-condition thermal models of avionics pod using stochastic configuration network
    Jie ZHANG, Liping PANG, Hongquan QU, Tianbo WANG
    2020, 71(S1):  441-447.  doi:10.11949/0438-1157.20191082
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    Avionics pod is a main carrier for multifunctional airborne electronic equipment, which effectively improves the performance of fighter. Increasing power of electronic equipment and low-pressure flight environment can exacerbate thermal environment in pod and can further affects the reliability of electronic equipment, so it is important to predict the thermal response of equipment under different flight conditions. In this paper, a thermal modeling method using thermal network analysis and stochastic configuration network is proposed and is further verified by experimental data of avionics pod with a ram air cooling system. The data of five conditions (high temperature storage, high temperature working, low temperature storage, low temperature accident and low temperature working) is divided into three groups according to heat transfer mechanism and is used to establish the storage thermal models, the working thermal models and the comprehensive thermal models, respectively. Thermal network analysis is used to obtain the input of network. Four-fold cross-validation and gray-scale analysis are used to determine hyper-parameters. The results show that the range sequence can be unified to [1—40] and the maximum number of hidden nodes of three thermal models can be set to 6, 9, and 11, respectively. The modeling results are positive, and the prediction error of electronic equipment temperature in the whole process of multi-conditions is within 3.512℃. Thus, the thermal modeling method that describes the thermal relationship of electronic equipment by data mining can be used to predict the avionics pod temperature in expected flight environment and evaluate the performance of thermal management system.

    Material science and engineering, nanotechnology
    Effect of active carbon nanoparticles on electrochemical properties of phosphorus-nitrogen double-doped graphene
    Chaoling HAN, Zhenqian CHEN
    2020, 71(S1):  448-453.  doi:10.11949/0438-1157.20191135
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    Fuel cell as a new clean energy technology has the characteristics of high energy conversion efficiency and environmental protection. It has been widely used in transportation, aerospace and other fields. Among the factors affecting the performance of fuel cell, the efficient catalysis and stability of electrodes are most importantly for the performance of the fuel cell system. In recent years, graphene based materials have provided theoretical feasibility for the study of low platinum (Pt) and high efficiency catalysis due to their excellent electrical and mechanical properties. In this study, phosphorus-nitrogen double-doped graphene was prepared with a one-step thermal reduction synthesis by using hexachlorocyclotriphosphazonitrile (HCCP) as the raw material. With adding the active carbon nanoparticles, the spacing between graphene layers was increased, and the agglomeration between graphene layers was also decrease, which result in a significantly promotion of the oxidation reduction reactions (ORR) performance. The results show that when the mass ratio of AC to GO is 10%, the specific surface area and electrochemical performance are improved most obviously with the limiting current density is -6.89 mA·cm-2 and the oxidation activity can be maintained above 80%. Therefore, the material we prepared for phosphorus-nitrogen double-doped graphene has great potential as the non-metallic catalyst material for fuel cells.

    Research of thin film nanocomposite (TFN) membranes incorporated spherical mesoporous silica nanoparticles with carboxyl group
    Yan SUN, Shitao LIU, Shang DENG, Liyun YU, Dongwei LYU, Jun MA, Xianbin LIU
    2020, 71(S1):  454-460.  doi:10.11949/0438-1157.20190920
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    Thin film composite (TFC) membranes incorporated with inorganic nanoparticles to form thin film nanocomposite (TFN) membranes, which had attracted much attention recently. However, the instability of nanoparticles in the TFC membranes and the insufficient mechanical strength of the membranes became the main challenges. Mesoporous silica nanoparticles with an average particle size of ca. 110 nm were modified with carboxyl groups, noted as MSN—COOH and further immobilized on the functional layer of the TFC membranes. The carboxyl groups were successfully incorporated into the mesoporous channels of MSN by characterization techniques, MSN—COOH nanoparticles were successfully bonded to the surface functional layer of the TFC film and formed the crosslinked network. Our experimental results revealed that the TFN membrane hybridized with MSN—COOH demonstrated up to 56.2% improvement in water ?ux, higher salt rejection, and improved mechanical strength compared to the control TFC membranes. Due to the addition of hydrophilic functional groups in monodisperse mesoporous nanoparticles, the hydrophilicity of the membrane surface was increased. Because of the ordered arrangement of monodisperse mesoporous nanoparticles in the matrix, the roughness of the membrane was lowered to a great extent, which was beneficial for enhancing water molecular transfer and fouling resistance of the membranes. Compared with plain TFN membranes, it had better stability and flexibility which kept the stabilization of membranes under high pressure filtration operation.

    Modification of commercial forward osmosis membranes and investigation on treatment of coking wastewater
    Zhiqiang LI, Na LYU, Lanying JIANG
    2020, 71(S1):  461-470.  doi:10.11949/0438-1157.20190670
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    Forward osmosis technology is an emerging membrane separation technology and has broad application prospects in the treatment of organic wastewater. In this paper, the Poten and HTI commercial forward osmosis membranes were modified and used for the rejection of refractory toxic small molecules (indole and pyridine) in coking wastewater. The effects of PIP concentration, membrane orientation and draw solution concentration on the membrane water flux, Js/Jwratio and organic matter rejection before and after modification, and the changes of the membrane characteristic parameters before and after modification were investigated. The results show that the membrane water flux and the Js/Jw ratio are reduced to different degrees after the interfacial polymerization modification of the Poten membrane and the HTI membrane. The water permeability coefficient A and the salt permeability coefficient B of the modified two forward osmosis membranes were both reduced. The membrane structure parameter S and the rejection of NaCl and organic matters were improved; the rejection of organic matter by HTI-IP composite membrane (81%) was significantly higher than that of IP-2 composite membrane; compared with FO mode, IP-2 composite membrane had higher water flux and reverse salt flux in PRO mode. In addition, both water flux and reverse salt flux increase with increasing draw solution concentration in different membrane orientations, but in FO mode, membrane flux exhibits a non-linear increase.

    Experimental study on air filtration performance of nanofiber membrane with hydrophilic and hydrophobic function at different relative humidity
    Yanpeng WU, Wei ZHAO, Fengjun CHEN
    2020, 71(S1):  471-478.  doi:10.11949/0438-1157.20191333
    Abstract ( 27 )   HTML ( 1)   PDF (1295KB) ( 7 )  
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    In this paper, PAN/PVP composite nanofiber films with hydrophilic function, PAN nanofiber films and PAN/PVDF composite nanofiber films with hydrophobic function were prepared by electrospinning with static contact angles of 23.6°, 81.2° and 131.9°. Using the self-constructed air filtration system, the filtration experiments of three kinds of nanofiber membranes were carried out under 40%, 55% and 70% humidity gradients. The filtration efficiency, resistance loss and quality factor (QF) of nanofiber membranes were analyzed. The results show that the filtration efficiency of the three nanofiber membranes increases with the increase of relative humidity, the resistance loss of PAN/ PVP film and PAN film increase with the increase of relative humidity, and the resistance loss of PAN/PVDF decreases with the increase of relative humidity. The QF value of PAN/PVP film and PAN film decreases with the increase of relative humidity, and the QF value of PAN/PVDF film increases with the increase of relative humidity. The higher is the relative humidity, the better is the filtration performance of PAN/PVDF nanofiber membrane.

    Investigation on photothermal conversion characteristics of graphene nanosheets-glycol nanofluids
    Fuheng LI
    2020, 71(S1):  479-485.  doi:10.11949/0438-1157.20191033
    Abstract ( 32 )   HTML ( 2)   PDF (971KB) ( 13 )  
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    The application of nanofluids to solar collectors is an important breakthrough in solar thermal conversion. Graphene nanomaterials have good absorption properties in visible and near-infrared regions.The graphene nanosheet material was prepared by Hummer method and characterized. Different mass fractions of graphene nanosheets-ethylene glycol nanofluids were configured. The smouldering test was carried out under the solar simulator and the photothermal conversion efficiency of the graphene nanosheets was calculated, and the photothermal conversion characteristics were compared with the base liquid. The results show that the photothermal conversion efficiency of the nanofluid solution increases with the increase of its concentration. After reaching the critical value, the photothermal conversion efficiency no longer increases but decreases. Among them,the temperature increase of graphene nanosheet nanofluid solution at the concentration of 0.0007%(mass) is up to 65.56℃, the photothermal conversion efficiency is 76.35%, and the ethylene glycol efficiency is increased by 49.65%. It indicates that graphene nanosheets have good optical properties and have good application prospects in solar collectors.

    Thermal effect analysis of nonmetallic addition manufacturing in spacecraft cabin environment
    Dongsheng YANG, Rong A, Jianbin ZHANG, Dapeng WANG, Bin ZHANG, Yingli XU, Junjie QIN, Shufen LIU
    2020, 71(S1):  486-493.  doi:10.11949/0438-1157.20191118
    Abstract ( 20 )   HTML ( 0)   PDF (1320KB) ( 5 )  
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    In view of application requirement of unattended non-metallic augmentation manufacturing technology in the future operation and maintenance development of space station, the thermal environment in the process of augmentation manufacturing in the space cabin environment is analyzed. The device was modeled, the distribution and heat production characteristics of the multiple heat sources was analyzed, the thermal diffusion effect was controlled, and temperature field simulation of local thermal insulation and integral enhanced convection design were carried out. Results showed that, the power consumption of the airtight device is about 72-96 W, the wall temperature of the device is maintained at about 29℃ when the initial temperature is 20℃, and the heat dissipation efficiency between the device and the environment can reach 21.6 W·m-2, which meets the temperature requirement of space material addition manufacturing and the temperature stability and reliability of the device. It provides certain theoretical guidance for on-orbit test verification in China, and provides new ideas and schemes for future extravehicular environment.

    Current situation and economic analysis of waste battery recycling industry
    Jing LI, Gang DU, Juanjuan YIN
    2020, 71(S1):  494-500.  doi:10.11949/0438-1157.20191585
    Abstract ( 36 )   HTML ( 5)   PDF (1004KB) ( 19 )  
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    The rapid development of new energy vehicles makes power battery recycling a hot research topic, but there is less research on the decommissioned battery recycling industry and economic analysis. This paper studies the current situation and existing problems of domestic waste battery recycling industry at present, analyzes the economics of battery recycling and the sensitivity factors arising from the production and operation process. At the same time, this paper points out that the development of battery recycling technology should be “decommissioned power battery resource regeneration - high value lithium-electric raw materials” as the main line, battery recycling enterprises should actively coordinate and coordinate with the new energy vehicle industry, build a regional recycling system, improve the overall economic level of the industry, the power battery recycling industry has a certain guiding significance.