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Table of Content
31 December 2018, Volume 69 Issue S2
    Current status and recent progress of LNG navigation safety standards
    ZHU Linlin, HUANGFU Lixia, GUO Kaihua
    2018, 69(S2):  1-8.  doi:10.11949/j.issn.0438-1157.20181124
    Abstract ( 76 )   PDF (362KB) ( 39 )  
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    For environmental and economic considerations, liquefied natural gas (LNG) has gradually become the preferred alternative fuel for LNG ships. The LNG navigation safety has attracted widespread attention of various countries, and corresponding standards are issued to ensure LNG navigation safety application. The article collates and summarizes the LNG navigation standards from four technical aspects of LNG port and terminal, LNG bunkering, LNG ships and LNG transportation, introduces and analyzes the current status of international and domestic LNG navigation safety standards to describes its recent progress and focus, which provides reference for the future application and generalization of LNG inland waterways in China. At present, the focus of improving the safety of LNG navigation is on the two core areas of LNG bunkering with high accident probability and complex inland transportation. The existing standards lack definitions and safety regulations for small LNG bunkering facilities. The improvement of quantitative risk assessment methods for LNG transportation and in-port bunkering operations is a hot and difficult study point.

    Principles and advances in perspiration cooling materials on human comfort adjustment
    DING Yi, DING Guoliang, ZHUANG Dawei
    2018, 69(S2):  9-16.  doi:10.11949/j.issn.0438-1157.20181148
    Abstract ( 46 )   PDF (3999KB) ( 27 )  
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    Fabrics with perspiration cooling technology will increase the perspiration efficiency of sweat and improve human thermal comfort. This article outlines the main features and principles of perspiration cooling technology, including rapid sweat absorption, rapid sweat perspiration, and high air permeability. New perspiration cooling materials are illustrated, covering moisture absorbent and quick-dry fibers, micropatterned superhydrophobic textiles, water-driven shape memory polymers, moisture-expansion multiply-layer composites, and moisture gradients driven polymer composites. The progress in the commercial development of functional clothing using perspiration cooling technology is presented. Finally, the advantages and disadvantages of various perspiration cooling technologies are summarized, and their development directions are suggested.

    Application of phase change materials in automobile energy saving
    ZHANG Liang, SHI Zhongke
    2018, 69(S2):  17-25.  doi:10.11949/j.issn.0438-1157.20181262
    Abstract ( 108 )   PDF (2579KB) ( 91 )  
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    At present, the automobile has become an indispensable transportation tool of work and life. At the same time the automobile also becomes the main source of environmental pollution. To save the energy, reduce the environmental pollution and realize sustainable development, the research of new energy vehicles has become the main trend and a basic policy of world's automobile production and usage. Temperature control of power battery is one of the key technologies of electric vehicle. The temperature control technology and thermal properties of PCM used in lithium batteries have been studied by scholars to solve the temperature instability and improve the safety performance of lithium batteries in new energy vehicles. By adding compounds such as metal, graphite and cellulose, the heat transfer performance of the battery had been improved. The mathematical equation of heat conduction established by computer simulation provides a theoretical basis for the application of PCM in lithium battery. In addition, the applications of PCM in energy recovery of vehicle exhaust and indoor temperature control are the research direction of vehicle energy saving. These process of indoor temperature control by PCM can be active or passive. This not only reduces the pollution during automobile operation, but also saves energy and enhances the safety of automobiles. Meanwhile, it keeps the temperature constant during the process of move and stop, and then the passengers will be more comfortable.

    Performance analysis of a novel compressor-ejector cycle with two-stage evaporation
    LIANG Xingyu, LIU Hongxin, CAO Xiang, SHAO Liangliang, ZHANG Chunlu
    2018, 69(S2):  26-30.  doi:10.11949/j.issn.0438-1157.20181163
    Abstract ( 55 )   PDF (484KB) ( 27 )  
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    Ejector cycle and two-stage evaporation cycle are two different ways to improve coefficient of performance (COP) for vapor-compression refrigeration or heat pump systems. They decrease the irreversible losses in throttling and heat transfer process, respectively. To further improve COP, a novel compressor-ejector cycle with two-stage evaporation is proposed. In this cycle, an ejector is applied to lift the lower evaporating pressure by recovering the expansion work. A thermodynamic model is developed to analyze performance of the new cycle. Numerical results indicate that COP of the new cycle under basic operating conditions is 20.4%, 10.9%, 7.6% higher than basic refrigeration cycle, ejector cycle and two-stage evaporation cycle, respectively. The improvement of COP is applicable to different refrigerants.

    Selection of state equations for evaporation calculation in LNG receiving terminal
    LI Ran, LIU Jingjun, LI Yuxing, YIN Yue, ZHU Jianlu, CHEN Wenjie, WANG Wuchang
    2018, 69(S2):  31-37.  doi:10.11949/j.issn.0438-1157.20181103
    Abstract ( 48 )   PDF (520KB) ( 36 )  
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    LNG physical parameters are the basis for the establishment of LNG receiving terminal model, process simulation calculation. Based on foreign experimental data, Aspen HYSYS software was used to analyze and evaluate the prediction accuracy of physical parameters such as density, enthalpy, and dew point of PR, SRK, LKP and BWRS equations, and evaluate the gas-liquid equilibrium and thermodynamic parameters calculation model. The tank evaporation model of the LNG receiving terminal was established to compare the accuracy of the four equations of state. The results showed that the PR equation had the highest prediction accuracy in the calculation of gas-liquid phase equilibrium, and the relative error was 4.70%. The most accurate thermodynamic parameters were calculated by LKP equation, and the prediction error was 2.59%. Considering the calculation accuracy of thermodynamic parameters and phase equilibrium parameters, the PR equation had the highest precision and the prediction error was 3.77%. In addition, the simulation results of evaporation and tank pressure by PR equation are in good agreement with the field data. Therefore, PR equation is recommended for evaporation calculation of LNG receiving station. The research results are useful for the selection of physical parameters and the equation of state for evaporation calculation of LNG receiving station.

    Thermodynamic analysis of absorption refrigeration cycles using ionic liquids as absorbents
    SUN Yanjun, DI Gaolei, XIA Juan, WANG Xiaopo, JIN Liwen
    2018, 69(S2):  38-44.  doi:10.11949/j.issn.0438-1157.20181093
    Abstract ( 49 )   PDF (692KB) ( 32 )  
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    The thermodynamic performances of three working pairs (R161/[hmim] [Tf2N], R32/[emim] [Tf2N] and R290/[emim] [BF4]) have been analyzed. Non-Random Two-Liquid (NRTL) model was used to correlate the vapor-liquid equilibrium data of refrigerants/ionic liquids. The effects of generator outlet temperature, evaporator outlet temperature, absorption temperature on the circulation ratio, COP and exergetic coefficient of performance (ECOP) have been discussed. The COP of R32/[emim] [Tf2N] system is close to that of R161/[hmim] [Tf2N] system and the COP of R290/[emim] [BF4] is the lowest. When the evaporation temperature is 5℃ and the absorption temperature is 25℃, the COP of R32[emim] [Tf2N] system reaches more than 0.59. However, the COP of R290 is always less than 0.1. Upon reducing the absorption temperature, it can expand the feasible temperature of the cycle and improve the COP. When the evaporation temperature is 5℃ and the absorption temperature is reduced from 30℃ to 25℃, the COP increases more than 1.4 times.

    Heat transfer and pressure drop characteristics inside stainless steel three-dimensional enhanced tubes
    SUN Zhichuan, LI Wei, YAN Xiaolong, MA Xiang, CHEN Wei, JIN Chunhua, WU Jie
    2018, 69(S2):  45-54.  doi:10.11949/j.issn.0438-1157.20181081
    Abstract ( 80 )   PDF (2469KB) ( 42 )  
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    Heat transfer and pressure drop characteristics of refrigerant R410A inside three horizontal enhanced tubes (EHT) and one smooth tube were investigated experimentally. All stainless steel two-side enhanced tubes were fabricated using a multiple high-pressured extruding process. These three-dimensional two-layer surface structures are composed of staggered dimpled protrusions or boat-shaped cavities and petal-shaped background patterns in a grid-like arrangement. According to the single-phase heat balance analysis, the proportion of heat loss in total heat is no more than 5% for the entire test range. Changing the water flow rate in the case where the refrigerant mass flow rate was maintained at a fixed value, the water-side heat transfer coefficients for each tube tested were obtained by the Wilson plot method. On basis of the thermal resistance model, it was found that 1EHT-1 exhibits the best single-phase heat transfer performance, followed by the 3EHT and 1EHT-2. A large difference between the experimental results of these evaporation and condensation tests was observed in the three enhanced tubes. It can be attributed to the effect of low thermal conductivity of stainless steel on the temperature distribution in the region of protrusions/cavities.

    Cooling and dehumidification performance of a novel semi-decoupled solid desiccant heat pump
    LU Fanli, GE Tianshu, DAI Yanjun, WANG Ruzhu
    2018, 69(S2):  55-60.  doi:10.11949/j.issn.0438-1157.20181184
    Abstract ( 48 )   PDF (557KB) ( 28 )  
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    The solid desiccant heat pump system (SDHP) can handle sensible and latent heat load simultaneously with high coefficient of performance (COP). However, the sensible heat load removal capacity of this system is relatively weak and the fluctuation of supply air temperature is large due to the frequent switch of the role of two desiccant coated heat exchangers (DCHE). In this study, the concept of semi-decoupled SDHP (SSDHP) system is proposed to overcome these disadvantages. In SSDHP system, the DCHE which acts as an evaporator operates in series with a conventional evaporator, and another DCHE functions as a condenser. Experiments are conducted to demonstrate the feasibility of this novel system under ARI humid condition to provide satisfied air. Results show that the comfortable supply air of 18.36℃ (max:19℃, min:18℃), 11.67 g/kg and the COP of 4.71 can be obtained. In addition, the influences of temperature and humidity ratio of fresh air on system performance are also analyzed.

    Coupled thermal dynamic performance in cryogenic liquid oxygen tank under slosh excitation
    LIU Zhan, FENG Yuyang, LEI Gang, LI Yanzhong
    2018, 69(S2):  61-67.  doi:10.11949/j.issn.0438-1157.20181055
    Abstract ( 51 )   PDF (599KB) ( 28 )  
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    The computational fluid dynamics (CFD) technique is used to investigate the thermal-dynamic coupled process in cryogenic liquid oxygen tank under the slosh excitations. The influences of the external environmental heat leak and the phase change occurring on the liquid-vapor interface are considered in detail. The slosh force, fluid slosh momentum, tank pressure, and fluid temperature distribution in tank caused by the external excitation are analyzed. The results show that both the slosh force suffered by tank and fluid slosh momentum have reducing trends with fluctuations under the external sinusoidal excitation. Influenced by the external slosh, the connection area between the subcooled liquid and the superheated vapor increases, so the superheated vapor is greatly cooled by the liquid, and the tank pressure decreases almost linearly with time. As for the fluid temperature monitors, while they are close to the liquid-vapor interface, the fluid sloshing has an obvious effect on the variation of monitors' temperature. In general, the temperature distribution in the tank is formed with the high temperature region in upper and low temperature region in bottom, and the high temperature in the external region and the low temperature in the interior. While as located on the top of tank, the vapor test points have a large temperature fluctuation, influenced by the top dished-head. For the bottom liquid temperature monitors, their values are larger than parts of liquid test points' temperature, with the direct heat transfer from the bottom dished-head wall.

    Modeling and optimization of water-to-water falling film evaporator
    YAN Hongzhi, HU Bin, WANG Ruzhu
    2018, 69(S2):  68-75.  doi:10.11949/j.issn.0438-1157.20181118
    Abstract ( 60 )   PDF (873KB) ( 35 )  
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    With the advantages of excellent heat transfer performance and less refrigerant charge, falling film evaporator has been widely used in seawater desalination and other industries. However, due to the practical problems of liquid level control and dry patches interactions, the structure design of falling film evaporator should be optimized for refrigeration applications. To resolve those problems, a simulation model for water-to-water falling film evaporator was conducted in this paper. Through the finite volume method, the temperature distribution along the working tubes and the heat exchanger has been obtained. For an existed falling film evaporator with 4-pass working tubes under boiling temperature of 80℃ and spraying mass of 0.4 kg·s-1, it is suggested that 2-pass working tubes should be in falling film region in order to arrive the largest heating capacity. The distribution of heat transfer coefficient along the tube is also investigated. Finally, it is proposed that there exits an optimal boundary line between full liquid and falling film region. It may provide a new idea for optimal design of falling film evaporators.

    Evaporation heat transfer performance of R410A inside 3-D double-enhanced tubes
    CHEN Jingxiang, LI Wei, ZHU Hua, JIN Chunhua, DU Jincai, ZHANG Zhengjiang, LIU Li
    2018, 69(S2):  76-81.  doi:10.11949/j.issn.0438-1157.20181086
    Abstract ( 84 )   PDF (2372KB) ( 20 )  
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    An experimental investigation on R410A evaporation characteristics inside newly developed 3-D enhanced tubes is performed, and the results are compared with a smooth tube with inner diameter of 11.07 mm. The test section is a 2 m long tube-in-tube heat exchanger and the mass flux ranges from 70 to 150 kg/(m2·s), vapor quality ranges from 0.1 to 0.9 when saturation temperature is maintained at 10℃.The heat transfer characteristics in low vapor quality region and high vapor quality region are discussed within the tested mass flux range. Four evaporation correlations are introduced to validate the test results of the smooth tube, and the results show that the predicted values have a good consistence with the experimental results.

    Flow boiling heat transfer characteristics of superhydrophilic modified surface in microchannels
    ZHOU Kan, LI Wei, LI Junye, ZHU Hua, SHENG Kuang, BAI Guanghui, CHANG Hao
    2018, 69(S2):  82-88.  doi:10.11949/j.issn.0438-1157.20181085
    Abstract ( 57 )   PDF (2314KB) ( 32 )  
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    Saturated flow boiling experiments were conducted to investigate the influence of surface wettability on the hydraulic and thermal transport performance in a large width-to-height aspect ratio, one-sided heated rectangular microchannel with deionized water as the working fluid. The superhydrophilic surface is fabricated through the Plasma Enhanced Chemical Vapor Deposition (PECVD) method on the originally smooth hydrophilic silicon wafer. The contact angles of the silicon wafer and superhydrophilic surface deposited with 100 nm-thickness silicon dioxide thin film are 65° ±3° and less than 5° respectively. Effects of heat flux and mass flux on the heat transfer characteristics for the superhydrophilic and silicon wafer surface are discussed through experimental measurements, which are further explained by flow patterns observed through high speed visualization. The local heat transfer coefficient decreases first until approaching a minimum value and then increases towards the exit along the flow direction. Severe heat transfer deterioration is obtained for the bare silicon wafer surface with increased heat flux, resulting from the local dryout phenomenon as can be verified by the flow visualization. Improved heat transfer performance is obtained on the superhydrophilic surface for relatively low mass fluxes and high heat fluxes as a result of latish occurrence of the local dryout phenomenon.

    Revision and validation of ventless storage model of cryogenic fluid
    QIN Tianyi, SHI Yumei
    2018, 69(S2):  89-94.  doi:10.11949/j.issn.0438-1157.20181139
    Abstract ( 46 )   PDF (358KB) ( 26 )  
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    Mathematical and physical model should be established to simulate and predict the process of ventless storage to guarantee the safety of storage and transportation. Based on semi-empirical model established by Russian scholars, heat leak was revised in this paper to better simulate the ventless storage process. The revised model was applied on a 2 m3 liquid nitrogen ventless storage experiment. The results of calculation and experiment were compared to validate the effectiveness of the heat leak revision. The result showed that the errors of the Russian model and the revised model were both negative. The absolute value of error was reduced after revision. Same working condition was also calculated with thermal stratification model of higher complexity. However, the revised Russian model still showed better performance in predicting this ventless storage process and was much easier to use in engineering situations.

    Preliminary study on high temperature heat pump system with water refrigerant
    WU Di, HU Bin, WANG Ruzhu, JIANG Nanshan, LI Ziliang, YU Jingjing
    2018, 69(S2):  95-100.  doi:10.11949/j.issn.0438-1157.20181112
    Abstract ( 50 )   PDF (1201KB) ( 27 )  
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    In the face of serious energy and environment problems, energy conservation and environmental protection have always been the hotspot that needs special attention in national and international aspects. Combining the advantage of high temperature heat pump and natural refrigerant of water, water vapor high temperature heat pump system (WVHTHP) is the ideal heat pump system in the next generation. WVHTHP not only can effectively recycle low grade waste energy but also is a green and sustainable technology. The preliminary study shows the closed water vapor compression heat pump cycle is feasible under the condition of negative pressure evaporation and positive pressure condensation. And the confirmatory test show that when the compressor suction temperature is fixed 80℃ and the discharge temperature increases from 117℃ to 133℃, the system pressure ratio increases from 3.47 to 5.94 and the system COP decreases from 5.8 to 3.7. When the compressor discharge temperature is 120℃, and the system pressure ratio is 4.2 and the system COP is nearly 5. The system performance of WVHTHP is very superior, and it has great potential in industrial application.

    Analysis of influence of surging on heat transfer characteristics of liquified natural gas flow boiling in channel of plate-fin heat exchanger
    WANG Haoxian, LI Jianrui, HU Haitao, DING Guoliang, WU Chunlin, CHEN Hui, XING Zhanyang
    2018, 69(S2):  101-108.  doi:10.11949/j.issn.0438-1157.20181116
    Abstract ( 54 )   PDF (872KB) ( 33 )  
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    Under surging conditions in the sea, the phase change and flow characteristics of two-phase fluids in plate-fin heat exchanger channels will change, which will affect the heat exchanger performance. In order to clarify the surging impact mechanism, a model for heat transfer characteristics of liquefied natural gas flow boiling in channel of plate-fin heat exchanger under surging conditions was established. Firstly, the mechanism of heat transfer and mass transfer of two-phase flow in the channels was analyzed, and the numerical model to simulate the flow and heat transfer under steady conditions was established; secondly, a model for reflecting the surging acceleration was added in the numerical model, which realizes the simulation of heat transfer charactersitics under surging conditions; the proposed model was verified based on the experimental data under onshore conditions. Based on the proposed model, the effects of vapor quality, frequency and amplitude of surging on heat transfer characteristics were analyzed. The results show that, the heat transfer coefficient increases with the increasing surging amplitude, while it decreases with the increasing surging frequency; as vapor quality increases, the influence of surging on heat transfer gradually changes from deterioration to enhancement; as vapor quality is within 0.2-0.8, the surging impact factor for the heat transfer coefficient is within 87.9%-110.0%. The effect of surging on time-average heat transfer coefficient changes with different conditions, representing a maximum deterioration of 5.0% and a maximum enhanceent of 2.0%.

    Noise characteristics of enhanced vapor injection heat pump under heating condition
    ZOU Chenbao, RAN Xiaopeng, ZHAI Xiaoqiang, LUO Qiong
    2018, 69(S2):  109-115.  doi:10.11949/j.issn.0438-1157.20181188
    Abstract ( 63 )   PDF (1506KB) ( 28 )  
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    Based on a self-developed enhanced vapor injection (EVI) air source heat pump, noise source was identified and spectrum analysis was analyzed by the fractional step operation method. The heating performance and noise variation law under variable conditions also were studied. It provides a targeted direction for reducing the noise of heat pump. The results show that the sound pressure level (SPL) of noise is enlarged when the rotating noise frequency of fan is close to the excitation frequency of compressor. When the fan switches from high speed to low speed under partial load, the SPL drops by 6.44 dB. The replenish pressure and inspiratory pressure are increased by EVI, and the SPL at -12℃ is increased by 1.05 dB compared with the gas filling valve closed. The SPL is increased by 2.1 dB when the opening of main valve is 100% compared with 30%. The influence of main valve opening on the noise is greater than that of gas filling valve.

    Experiment on transport performance of bubble pumps with R134a/R23-DMF solutions
    WANG Qin, LIU Yilun, LU Wei, WANG Shikuan, HE Wei, HAO Nan, ZHANG Shaozhi
    2018, 69(S2):  116-122.  doi:10.11949/j.issn.0438-1157.20181131
    Abstract ( 54 )   PDF (664KB) ( 23 )  
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    An experimental rig was built and researches on the transport performance of bubble pumps with R134a/R23-DMF solutions and three lifting tubes of different inner diameters (6 mm, 8 mm and 12 mm) were conducted. On the same concentration of solutions, the results showed the gas mass flow rate and the generating temperature increased approximately linearly with the increase of the heat input, the pumping ratio decreased approximately reversely with the increase of the gas mass flow rate, and the heat input had slight effect on system pressure. The concentrations of solutions had slight effect on the pumping ratio and generating temperature, but it had obvious effect on system pressure. The pumping ratio of the bubble pump and the poor R134a/R23 solution mass flow rate with lifting tube of 8 mm inner diameter has medium variation range compared with those of 6 mm and 12 mm lifting tubes, but the range of the gas mass flow rate was the widest and the generating temperature was the lowest. It showed that the bubble pump with lifting tube of 8 mm inner diameter was appropriate for the diffusion absorption refrigerator. The experimental results will be helpful to the design of bubble pumps for the diffusion absorption refrigerator.

    Experimental study on influence of adiabatic material breakage on evaporation rate of B type LNG simulator cabin
    FU Yunzhun, WU Shuang, LIN Jichao, JU Yonglin, NIU Weichen
    2018, 69(S2):  123-127.  doi:10.11949/j.issn.0438-1157.20181111
    Abstract ( 62 )   PDF (3052KB) ( 36 )  
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    The structure and adiabatic mode of a new Type B liquefied natural gas simulator cabin are introduced and a low temperature test device for adiabatic effect is built. The temperature distribution of the adiabatic layer in the simulated cabin under the condition of breakage is tested, and the experimental results show that the evaporation rate of the local liquid nitrogen in the simulator is 2.138%/d, which increases by 0.226%/d compared with the insulating layer intact condition. It can be concluded that the damage of the local adiabatic structure has influence on the adiabatic performance of the simulator and the ship. The research results provide an important reference for the development and design of LNG cargo tank.

    Finite element analysis and structural optimization of tubesheet in coil-wound heat exchanger
    CHEN Jie, JI Bowen, ZHUANG Dawei, LU Laiyun, ZHANG Xiaohui, DING Guoliang
    2018, 69(S2):  128-134.  doi:10.11949/j.issn.0438-1157.20181132
    Abstract ( 60 )   PDF (4198KB) ( 34 )  
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    The coil-wound heat exchanger is widely used in large-scale liquefied natural gas (LNG) installations. The tubesheet is an important component of the coil-wound heat exchanger. Due to the fact that the tubesheet is located at the junction of the tube-side and the shell-side and the densely holes reduce the structural strength, the tubesheet is a weak part of the LNG coil-wound heat exchanger, and a prediction model of the stress on the tubesheet is needed to check the stress intensity. In this paper, a model of tubesheet unit including short section, shell cover and shell of heat exchanger is developed and finite element calculations of tubesheet under multiple working conditions are carried out by Ansys. The stress intensity is checked according to JB4732-1995. The modeling results show that the tensile stress inside the shell causes the large local membrane stress at the short section connected to the tubesheet due to the shell-side fluid pressure acting on the shell of the heat exchanger, and the local membrane stress exceeds the allowable stress intensity. By increasing the thickness of the short section of the tubesheet from 45 mm to 57.5 mm, the excessive local membrane stress can be avoided.

    Flow boiling heat transfer of propane in helically coiled tube
    WAN Xingchen, LIN Wensheng
    2018, 69(S2):  135-140.  doi:10.11949/j.issn.0438-1157.20181122
    Abstract ( 43 )   PDF (528KB) ( 29 )  
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    As natural refrigeration, propane will be alternative refrigerant in the future due to its good performance and its lack of impact on the environment. Currently, the study for flow boiling heat transfer of propane in helically coiled tube is few. This paper presents the experimental results of flow boiling heat transfer of propane in helically coiled tube. The internal diameter, helical diameter and helical pitch of helically coiled tube are 8 mm, 42 mm, 21.5 mm respectively and the outer tube is straight smooth tube. As warm fluid, water flows between outer tube and helically coiled tube. The heat flux can be adjusted by changing inlet temperature and flow meter of water. The heat transfer coefficients in experiment are compared to predictions from several boiling correlations both in straight tubes and helically coiled tubes in the literature. Comparison results show that helically coiled tubes have better heat transfer effect than straight tubes. The results also shows that when the heat flux is less than 6 kW·m-2, Guo's correlation shows higher accuracy than Ji's correlation. So Guo's correlation is recommended at low heat flux condition.

    Comparison of solutions of LNG heat exchangers used on LNG powered ships
    TIAN Yajie, LIN Wensheng
    2018, 69(S2):  141-146.  doi:10.11949/j.issn.0438-1157.20181128
    Abstract ( 67 )   PDF (506KB) ( 29 )  
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    For the gas supply system used on LNG (liquefied natural gas) powered ships, propane and 50% aqueous solution of ethylene glycol are used as the intermediate heat exchange medium at the given low pressure condition. Choose the heat transfer correlation of spiral tubes and shell side heat transfer correlation for the heat exchanger. Then calculate the heat transfer area and the length of the coiled tubes of the spiral wound LNG heat exchanger (SWHE) with MATLAB programming software. Combined with engineering practice, the distribution of the tube length and heat transfer area when using two-stage heat exchangers are discussed. The HYSYS simulation results show that when the flow and the heat exchange state of the LNG in the pipe are the same, the mass flow rate of the required water glycol is 10 times that of the mass flow rate of propane. Due to the phase change of propane, the flow rate of gaseous propane on the shell-side of the heat exchanger that varies greatly, which can reach 1.7 m/s at the exit. So it requires the heat exchanger to have a higher resistance to pressure. The flow rate of water glycol in the shell side is only about 0.2 m/s. When it is divided into two-stage heat exchangers, the heat exchange area and the length of the tubes of the gasification stage are less than 12.7% of that of the heating stage. When the two stages are the same size, at least 80% of the heat exchange area is wasted. The selected heat exchanger is used on the LNG powered ship. Both space utilization and safety are required. After the calculation, it is believed that although propane changes phase, the heat transfer advantage is not obvious and the safety advantage is not as good as water glycol.

    Preliminary study on heat transfer calculation of submerged combustion LNG vaporizer
    XU Jingxuan, LIN Wensheng, RUAN Binhui
    2018, 69(S2):  147-152.  doi:10.11949/j.issn.0438-1157.20181138
    Abstract ( 92 )   PDF (479KB) ( 45 )  
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    In this paper, the heat transfer calculation method of the (SCV) is studied. Through subsection calculation, the applicability of the existing heat transfer calculation model to the heat transfer calculation of the submerged combustion LNG vaporizer is explored. Zukauskas model of fluid transverse swept tube bundle is applied to calculate the external heat transfer of the tube. As for the internal heat transfer of the tube, Dittus-Boelter model, Shah (1982) model, Kandlikar (1990) model and Kew and Cornwell (1997) model are utilized. The results show that the calculated results of Kandlikar (1990) model and Kew and Cornwell (1997) model have a small deviation in the calculation of boiling heat transfer in the LNG pipe, which are 38.46% and 38.33% respectively.

    Numerical simulation of droplet coalescence and bounce process on hydrophobic surfaces
    CHENG Saifeng, LIANG Caihua, ZHAO Wei, ZHANG Xiaosong
    2018, 69(S2):  153-160.  doi:10.11949/j.issn.0438-1157.20181061
    Abstract ( 56 )   PDF (1064KB) ( 44 )  
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    The phenomenon of droplet coalescence-induced self-propelled jumping is of great significance in enhancing heat transfer, preventing frosting and defrosting in heat pump air conditioning systems. The processes of droplet coalescence and self-propelled jumping are modeled independently in consideration with the released surface energy, gravity potential energy, the viscous dissipation and surface tension energy dissipation caused by contact angle hysteresis. The simulation values are in accordance with existing experimental data in the literature. It was found that the number of droplets, the uniformity of the radius and the surface characteristics do affect the process of coalescence and self-propelled jumping. With the increasing of droplet numbers, the critical contact angle in process of coalescence decreases from 120° to 105°. The critical contact angle in process of self-propelled jumping decreases from 140° to 130° with the increasing of uniformity of droplet radius. The results indicate that larger droplet number and higher uniformity of droplet radius are beneficial for coalescence and self-propelled jumping. In addition, the influence of solid-liquid contact fraction on the process coalescence and self-propelled jumping decreases with the increase of contact angle.

    Evaporative cooling experiment of microchannel heat exchanger in loop heat pipe
    LIU Haichao, SHAO Shuangquan, ZHANG Hainan, TIAN Changqing
    2018, 69(S2):  161-166.  doi:10.11949/j.issn.0438-1157.20181065
    Abstract ( 45 )   PDF (1396KB) ( 27 )  
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    The microchannel heat exchanger is applied as the heat exchanger of the loop heat pipes in data center, and the evaporative cooling experiment is carried out on the side of the microchannel condenser. The influence of evaporative cooling on the microchannel condenser is measured by using the enthalpy difference chamber in the experiment, and the temperature difference between the inlet and outlet air of the microchannel condenser and evaporator with different indoor and outdoor temperature and humidity was analyzed. The experimental results show that evaporative cooling can make the condenser inlet air temperature achieve a large temperature drop and increase the temperature drop of the inlet and outlet air, while the spraying can cool the air through the heat pipe about 0.3-1.9℃ and increase about 0.1-0.6 kW heat transfer of the system. Moreover, the evaporative cooling capacity of microchannel condenser and evaporator increases with the increase of indoor and outdoor temperature difference, and decreases with the increase of outdoor relative humidity. Compared with single heat pipe air conditioning, loop heat pipe with evaporative cooling in data center can make better use of natural cooling energy, prolong the utilization time of air conditioning system in a year, and expand the application area of the system.

    Dynamic simulation on cryogenic multi-stream heat exchange processes with multi-node coupling method
    ZHANG Pu, ZHOU Li, GUO Kaihua, CHEN Zhenghua, WANG Weijie
    2018, 69(S2):  167-173.  doi:10.11949/j.issn.0438-1157.20181120
    Abstract ( 47 )   PDF (624KB) ( 38 )  
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    Multi-Stream Heat Exchanger (MSHE) is the core component of gas liquefaction system, its working performance can significantly affect the cooling characteristics and thermal efficiency of system. Based on the principle of two-phase volume node, this article established dynamic simulation method for Mixed-Refrigerant (MR) cryogenic system with a Multi-Node Coupling (MNV) MSHE model. The study results reveal that the heat leak's influence on cooling characteristics of MSHE is negligible during start-up process, while significant and can't negligible in low temperature situation. The liquid-level oscillation in MSHE channel can significantly impact the cooling characteristics, and induce the circulating MR composition shift, cooling capacity and cooling-down rate oscillation in further, which may deteriorate the cooling performance of the MSHE. The results suggest that measures should be taken in design and operation process to avoid the liquid level oscillation phenomenon in MR low-temperature MSHE channels.

    Experimental study on pressure drop characteristic of two-phase flow in reduced tee junction with flat tube
    XU Xiaoxiao, CHEN Long, XIAO Jiumin, LIU Chao
    2018, 69(S2):  174-179.  doi:10.11949/j.issn.0438-1157.20181171
    Abstract ( 40 )   PDF (902KB) ( 56 )  
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    The pressure drop characteristic of two-phase flow in normal T-junction has been fully investigated. However, few articles focus on the pressure drop characteristics of the reduced T-junction with flat tube. In this paper, R134a were used as the work medium, and the experimental study on the pressure drop characteristics was carried out at the T-junction placed horizontally. Experimental results show that the existing pressure drop empirical correlations of microchannel were not able to predict the two-phase flow in microchannel flat tube frictional pressure drop accurately. Through fitting experimental data, the empirical correlation of frictional pressure drop for stratified flow with quality range of 0.01-0.45 and flow range of 0.7-3 g/s in microchannel flat tube is obtained, and the gas-liquid interaction coefficient C in Chisholm model was modified to predict the irreversible pressure drop of stratified flow with flow range of 1.1-5.3 g/s, quality range of 0.03-0.26 and separation ratio is 0.1-0.8 from header to flat tube.

    Experimental study on air source heat pump system with compressor frequency conversion and capillary
    NIU Jianhui, XU Shuxue, LIU Shuailing, MA Guoyuan
    2018, 69(S2):  180-185.  doi:10.11949/j.issn.0438-1157.20181130
    Abstract ( 40 )   PDF (528KB) ( 35 )  
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    Aiming at the household air source heat pump for “coal to electricity”, a capillary as a throttle element is proposed to replace the thermal expansion valve or the electronic expansion valve, and an experimental device for heat pump system was set up. The influence of different capillary length on the compressor suction pressure, exhaust temperature and heat capacity of the unit under variable frequency regulation of compressor were experimentally studied. The experimental results show that, after replacing the thermal expansion valve or the electronic expansion valve, the system can run stably for a long time. The system has the best thermal performance when the capillary length is 500 mm and the compressor frequency is 35 Hz, and the heating capacity and heating COP are the largest, but the suction pressure and the exhaust temperature are moderate.

    Experimental study of frost growth characteristics on surface of finned-tube heat exchangers
    ZHANG Lumeng, GUO Xianmin, XUE Jie
    2018, 69(S2):  186-192.  doi:10.11949/j.issn.0438-1157.20181134
    Abstract ( 58 )   PDF (649KB) ( 28 )  
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    The air source heat pump (ASHP) system has excellent energy saving and emission reduction effects. However, under environmental conditions of low temperature and high humidity in winter, frost will occur on the surface of the evaporator easily, which affects the heat transfer performance and reliability of the system. The experimental study of frost growth characteristics on the surface of the finned-tube heat exchangers was carried out in this paper. The frost surface temperature was measured by the infrared thermal imager, and calibrated by using the direct measurement with micrometer and thermocouple device. The effects of the ambient temperature, relative humidity and face velocity on the frost thickness, frost mass and the frost-wet air interface conditions are analyzed. The difference between the frost surface temperature and the ambient temperature is regarded as the heat transfer driving force of frosting, and the difference between the water vapor partial pressure in wet air and the saturated water vapor partial pressure at the interface, i.e., the interface water vapor pressure difference, is regarded as the mass transfer driving force of frosting. The frosting mechanism of the finned-tube heat exchangers is analyzed, which lay a foundation for the optimum design and anti-frosting and defrosting of ASHP system.

    Polymer crystallization by phase field method coupling with lattice Boltzmann method
    WANG Xin, YANG Binxin
    2018, 69(S2):  193-199.  doi:10.11949/j.issn.0438-1157.20181228
    Abstract ( 35 )   PDF (2556KB) ( 49 )  
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    On the basis of simulating the phase field method of dendritic growth, this work combined the multi-relaxation format of lattice Boltzmann method of the phase field method, established the phase field-lattice dynamic coupling model, and numerically simulated the microstructure of dendrite growth occurred in the process of polymer crystallization. This coupling model circumvented difficulties of traditional phase field method that needed resolve solid liquid interface accurately in high resolution which would severely impact the option of time steps. Using lattice Boltzmann method (LBM), this work came up the adaptive time stepping, that allowed changing time step expect sizing grid correspondingly, in other words, time step can be large, however, the results of numerical simulation will not emerge the phenomenon of dispersion, avoid the using of high precision differential formats. Using FORTRAN to accomplish the coupling model's establishment and simulating the crystallization of isotactic polystyrene, this work researched the crystallization of isotactic polystyrene at different experimental temperature, and compared the simulated results with the reality experimental results, to determine the feasibility of the coupling model.

    Effects of freezing conditions on cryopreservation of plant cells
    XIE Yanqi, ZHU Kai, WANG Yabo
    2018, 69(S2):  200-204.  doi:10.11949/j.issn.0438-1157.20181164
    Abstract ( 42 )   PDF (1764KB) ( 29 )  
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    Basic research at the cellular level is an essential part for ensuring the quality of food and vegetables in cold storage. Intracellular ice formation (ⅡF) causes severe cellular damage, thus causing many problems in cryopreservation. The pre-cooling process has an important influence on the formation of intracellular ice crystals. Therefore, photographing the intracellular ice crystal formation process provides the necessary support for optimizing the cryopreservation scheme. The onion epidermal cells were frozen at different cooling rates, and a low-temperature microscopy system was used with a high-speed camera to visualize the ⅡF process in the cells. At the same temperature, the greater the rate of cooling, the lower the probability of intracellular ⅡF emergence. However, the growth rate of ice crystals at the edge of the cells increased, and the degree of damage to the cells fluctuated significantly.

    Performance of solar steam ejector refrigerator
    YU Chaoqun, ZANG Runqing, DUAN Zhenkun
    2018, 69(S2):  205-209.  doi:10.11949/j.issn.0438-1157.20181123
    Abstract ( 38 )   PDF (574KB) ( 23 )  
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    Based on the study of the performance for the solar steam jet refrigeration system, the experiment takes R134a as the refrigerant and uses the control variable method to study the influence of the evaporation temperature and generator temperature on the ejection coefficient, the cooling capacity and the COP of the refrigeration system. The results show that:when the condensing temperature and generator temperature are constant, the injection coefficient, refrigerating capacity and COP increase with the increase of evaporation temperature. When the condensing temperature is 35℃ and the evaporation temperature is 6℃, the generator temperature is below 66℃, and the injection coefficient, refrigerating capacity and COP are 0. When the generator temperature is more than 66℃, the injection coefficient, refrigerating capacity and COP increase first and then decrease with the increase of temperature. When the generator temperature is 84℃,the maximum values are 0.223, 2.02 kW and 0.204 respectively.

    Treatment of phenol wastewater by microwave catalytic wet oxidation under high pressure
    XUE Chao, MAO Yanpeng, WANG Wenlong, SONG Zhanlong, ZHAO Xiqiang, SUN Jing, WANG Yanxiang
    2018, 69(S2):  210-217.  doi:10.11949/j.issn.0438-1157.20181225
    Abstract ( 54 )   PDF (933KB) ( 36 )  
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    Traditional technology of wet oxidation was often carried out under the situation of high temperature and pressure, which results in low efficiency of the reaction, serious wear of the reactor and harsh reaction conditions. And the degradation rate and efficiency was often under at a lower level. The objective of this study was to elucidate the mechanism degrading wastewater by using MW-CWPO, in which the production of hydroxyl radicals can be promoted, and hence improves the degradation of pollutants under relatively gentle conditions. In this research, p-nitro phenol (100 mg/L) was used as target pollutant, and carbon nanotubes and hydrogen peroxides were used as catalysts and auxiliary oxidant. It is investigated that the high power, high pressure, and high concentration of catalyst and oxidant can effectively improve the degradation efficiency of organic wastewater. Besides, it was found that MW radiation can promote hot spot (exceed 1000℃) formation on the surface of catalysts, which can enhance hydroxyl generation by the decomposition of oxidizers and dissolved oxygen at the condition of high temperature. Additionally, the catalysts after reaction were scanned by electron microscope and find that the surface of the carbon nanotube used in the experiment had no apparent modification, so that it can be reused for a long time. Since factors such as pressure can enhance the degradation rate of organic wastewater, they can be controllably modified to accelerate chemical reactions or improve degradation rate of actual chemical industry wastewater.

    Process intensification of removing arsenic from industrial phosphoric acid by Keltics static mixer
    REN Xinlin, MEI Yi, FENG Mengli, LI Boyang, LYU Wuhua, WEN Yaling, WANG Chi, HE Dedong
    2018, 69(S2):  218-225.  doi:10.11949/j.issn.0438-1157.20180935
    Abstract ( 60 )   PDF (977KB) ( 40 )  
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    The agitation tank and Keltics static mixer were used to remove arsenic (As) from industrial phosphoric acid by using phosphorus pentasulfide (P2S5). The single factor experiments, orthogonal experiment and response suface methodology were conducted to acquire the optimal process conditions. The results showed that the removal efficiencies of both of the two reactors were higher than 98.8% and the content of As were less than 0.5 mg·kg-1 in the purified phosphoric acid, which met the national standard of China GB 1886.15-2015 for food grade phosphoric acid. As the agitation tank was the reactor, the optimum process conditions were that the actual dosage of dearsenifying agent was 4 times of the theoretical dosage, reaction temperature was 65℃, reaction time was 70 min and the stirring speed was 300 r·min-1. As the Keltics static mixer was the reactor, the optimum process conditions were that the actual dosage of dearsenifying agent was 4 times of the theoretical dosage and the phosphoric acid flow was 0.66 m3·s-1. Under this condition, the disposal phosphoric flow was increased greatly, and the reaction time was only 2.4 s and the amount of phosphoric acid treated per unit of time is 372 times that of the stirred reactor. As Keltics static mixer is used to remove arsenic (As) from industrial phosphoric acid, there are many advantages, such as the shorter technological process, the simpler construction, the continuant operation, etc., which is hopefully to realize the process intensification of dearsenifying As from phosphoric.

    Nitrogen expansion liquefaction and separation process for natural gas with high ethane content
    HE Ting, LIN Wensheng
    2018, 69(S2):  226-231.  doi:10.11949/j.issn.0438-1157.20181119
    Abstract ( 71 )   PDF (657KB) ( 26 )  
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    It is an economical and reasonable choice to separate ethane at the same time of natural gas liquefaction. On the basis of the conventional nitrogen expansion cycle, a nitrogen expansion liquefaction and separation process for natural gas with high ethane content is proposed. Four different kinds of natural gas, with ethane contents of 10%, 20%, 30% and 40%, are investigated with the proposed process by using the process simulation software HYSYS to analyze and compare the specific power consumption of the liquefaction process under different liquefaction pressure. In order to reduce the energy consumption of the process, the influence of the refrigerant flow rate, the outlet pressure of the nitrogen expander and the throttle temperature are further studied under the condition that the C2H6 content of the LNG product is less than 1% and the purity of the liquefied ethane is up to 99.5%. On this basis, the process is optimized in combination with the optimizer in the HYSYS software. The results show that, when the ethane contents are 10%, 20%, 30%, 40%, the specific power consumption decreases by 7.24%, 6.13%, 5.8%, and 7.07%, respectively.

    Adhesion characteristics of urea aqueous solution in solidification and crystallization
    LI Zhaoning, ZHAO Yanjie, TANG Yupeng
    2018, 69(S2):  232-239.  doi:10.11949/j.issn.0438-1157.20181094
    Abstract ( 45 )   PDF (1134KB) ( 30 )  
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    During the preparation process of the cold storage slurry,the crystal layer adheres and accumulates on the surface of the heat exchanger, which greatly worsens the heat transfer characteristics and reduces the system efficiency. It is found that when the binary eutectic solution is in the solid-liquid two-phase region, there is a micron level liquid film between the heat transfer surface and the crystal layer, which will significantly reduce the adhesion of the crystal layer. In this paper, the crystallization model of two components eutectic solution is put forward. With urea solution as the research object, the adhesion of crystal layer under different working conditions is tested by the crystallization and scour experiment. In the scour experiment of the crystal layer in the solid-liquid two-phase region urea solution, it is found that the crystal layer can be scoured and shedding under the suitable flow rate and supercooling degree. However, the crystalline layer with solid phase region can not be thoroughly washed away. The experiment shows that there is a positive correlation between supercooling and adhesion, and indirectly proves the existence of micro liquid film.

    A method of extraction and separation of oridonin
    LI Changhui, MENG Ling, GUI Xia, YUN Zhi
    2018, 69(S2):  240-245.  doi:10.11949/j.issn.0438-1157.20180517
    Abstract ( 23 )   PDF (490KB) ( 32 )  
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    A new method for extracting oridonin from rubescens and processing extracts was studied. The solvent back-mixing method was used to extract oridonin, and the extract with higher target product concentration was obtained. The optimum conditions for the extraction of oridonin were found by the single factor method:the ratio of material to solvent was 1 (g):8 (ml); the oridonin content contained in mixed solvent was 652 mg/L; temperature was 35℃; pH was 5.5. By adding water to change the polarity of the extracted solvent, and accompanied by low-temperature fractional precipitation. The remaining extracted solvent was evaporated under reduced pressure to obtain an extractum of 22.2% of oridonin, which was significantly higher than that reported in the literature. After pretreatment, the extracted had almost no loss of oridonin during the desolvation process, which solved the problem of large loss of oridonin in the conventional concentration process.

    Experimental study on saline solution by direct contact membrane distillation
    LIU Yangjiu, HAN Jitian, WANG Yunshan, TIEN-CHIEN Jen
    2018, 69(S2):  246-251.  doi:10.11949/j.issn.0438-1157.20181135
    Abstract ( 65 )   PDF (509KB) ( 38 )  
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    Polyvinylidene fluoride (PVDF) hollow fiber membrane is used as membrane material, NaCl solutions with concentrations of 5%, 15% and 25% are treated by direct contact membrane distillation. Orthogonal experiment is used to optimize the operation conditions, and the result show that value of the permeate flux (J) could achieve maximum value of 12.599 kg/(m2·h) when the inlet temperature of liquid side (T1) is 80℃, inlet temperature of osmotic side (T3) is 20℃, and flow rate (Q) is 100 L/h. Gained output ratio (GOR) could be 13.775 when T1 is 80℃, T3 is 35℃ and Q is 40 L/h. The salt rejection ratio all is more than 99.9%. The result of single factor experiment show that J is raised with the increase of T1 and Q, but decreased with the increase of T3. GOR is increased with the increase of T1 and T3, but decreased with the increase of the Q. The research indicate that membrane distillation technology has a good applied prospect of treat saline solution.

    Sensor fault detection and diagnosis for data center air conditioning system based on LSTM neural network
    WANG Luyao, WU Bin, DU Zhimin, JIN Xinqiao
    2018, 69(S2):  252-259.  doi:10.11949/j.issn.0438-1157.20181084
    Abstract ( 51 )   PDF (3900KB) ( 51 )  
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    The faults of data center air-conditioning system directly results in increasing energy consumption and reducing operation reliability. Combined with deep learning technology, a fault detection and diagnosis method of sensors for air conditioning system is proposed by using LSTM (long short term memory) neural network. Verified by the experiment, the method can identify the fixed biases and drifting biases of both liquid line temperature sensor and discharge temperature sensor through building the fault detection and diagnosis models for them respectively. For the fault-free condition, the detection accuracy of this method is about 90%. For the sensor fault whose deviation degree is greater than the minimum detection deviation of the method, the detection accuracy is above 94%.

    Steady-state simulation model of vapor-injected heat pump systems with flash tank
    SUN Haoran, HU Haitao, LI Hao, DING Guoliang, WU Chengyun, WANG Xuyang, LYU Zhongyuan
    2018, 69(S2):  260-265.  doi:10.11949/j.issn.0438-1157.20181117
    Abstract ( 35 )   PDF (774KB) ( 28 )  
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    A steady-state simulation model of vapor injection heat pump systems with flash tank is developed. In the model, the vapor-injected compressor model is developed by establishing the theory-based explicit equations; the heat exchanger model is established using multi-zone method to reflect the characteristics of each phase zone; and a system iteration algorithm based on sequential module method is developed to solve the component models. The validation results show that, for the compressor model, the deviations of the mass flow rate and input power are within ±7% and ±5%, respectively; for the heat exchanger model, the deviations of the heat capacity and pressure drop are within ±3% and ±4%, respectively. Compared to the traditional heat pump system, the heat capacity is increased by 18.9% when the outdoor temperature is -20℃.

    Control configuration design with genetic algorithm for decentralized control system
    LI Fan, XU Feng, LUO Xionglin
    2018, 69(S2):  266-273.  doi:10.11949/j.issn.0438-1157.20180833
    Abstract ( 18 )   PDF (640KB) ( 58 )  
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    Chemical processes are usually high-dimensional multivariable systems. When designing the bottom regulatory PID control system, the traditional subjective analysis methods relying on control engineers are difficult to be applied and fail to the optimal control configuration, so a simple and fast computer optimization algorithm is urgently needed. So, an optimization algorithm for decentralized control loop configuration is proposed based on genetic algorithm. In this algorithm, the structure matrix is encoded in string form and the variable pairings are transformed into an integer array, then through choosing the right genetic operator the operations involving crossover, mutation and selection are applied on the integer array. The optimal variable pairing scheme under unconstrained condition is obtained. Moreover, the genetic operator is improved and adjusted according to the constraint conditions. Based on the optimal pairing scheme under unconstrained conditions, the optimal variable pairing scheme with constraints can be obtained by only using mutation and selection operators with a faster calculation speed. Finally, the validity and correctness of the algorithm are tested by case studies involving TE process.

    Research on multi-stage power control system of lignite microwave drying production line
    ZHOU Xinzhi, SHAO Lun, CUI Ke, YANG Yang, ZHOU Yu, ZHANG Ruobin
    2018, 69(S2):  274-282.  doi:10.11949/j.issn.0438-1157.20181210
    Abstract ( 52 )   PDF (1125KB) ( 30 )  
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    Compared with conventional evaporative drying processes, microwave drying technology realizes simultaneous and rapid heating of both the inside and outside through microwave radiation, and has the advantages of low energy consumption, high efficiency, and no pollution in the lignite drying and upgrading process. However, overheating and thermal runaway tend to occur during microwave drying of lignite, which may cause spontaneous combustion of lignite or even explosion, thus resulting in great loss to the production line. In order to realize optimal control of lignite temperature during microwave drying, a lignite moisture content based method for dynamic adjustment of target temperature range was proposed in this paper. Based on this method, an active coordinated microwave power control system for multistage microwave drying chambers on the production line was established through modeling and simulation of the microwave drying chambers and analysis of on-site sampling data. Taking temperature and reflection coefficient as its input parameters, the system can dynamically adjust the output power of microwave sources through a PID control model. The system was installed and tested on the microwave lignite drying production line built by Nanjing Sanle Corporation in Hailar, Inner Mongolia. The results show that the system can accurately control the temperature range of lignite at each stage of microwave chambers, guarantee production safety, and keep the lignite moisture content under 10%.

    Transient simulation of steam discharge with differeat load
    LU Nianci, WANG Ruixiang, MA Qingyang
    2018, 69(S2):  283-290.  doi:10.11949/j.issn.0438-1157.20180946
    Abstract ( 38 )   PDF (677KB) ( 31 )  
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    The mathematical model of non-equilibrium thermal process of steam accumulator and the mechanics model of aircraft based on Newton's law and gas dynamics for some thermal system was established. Based on the test date, the simulation result was tested and verified. The kinetic and thermodynamic comprehensive simulation of the steam process for different carrier-based aircraft mass was analyzed. The results was showed as follows:when the mass of the aircraft is 8, 20, 35 t, the end speed of aircraft is bigger than 72 m/s, the maximum acceleration is less than 6g and the time of catapult is less than 3 s. With the aircraft mass becoming greater, the steam discharging mass becomes larger, the end pressure of steam accumulator becomes lower,as while the down rate of the pressure of cylinder is small and the leaking quality of cylinder is bigger.

    Research on temperature prediction model for microwave heating based on wavelet denoising and improved PSO-SVM
    ZHOU Xinzhi, SHAO Lun, LI Rongkun, ZHAO Chengping, DONG Chenlong
    2018, 69(S2):  291-299.  doi:10.11949/j.issn.0438-1157.20181211
    Abstract ( 53 )   PDF (1577KB) ( 46 )  
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    Aiming at the nonlinear correlation and time-delay of microwave heating process, a microwave-heated lignite temperature prediction method based on wavelet denoising optimized by thresholds through correlation principles and support vector machine optimized by improved particle swarm optimization is proposed. The temperature for microwave heating of lignite is acquired via wavelets with an optimized threshold based on relevant principles. The particle swarm optimization algorithm is improved by introducing the similarity function and the control parameter α. It is used to optimize the penalty coefficient C, the insensitive loss function parameter ε and the kernel function parameter g of the microwave heating lignite temperature support vector machine prediction model parameters. As the similarity function increases, the random variability of the particles increases; the number of iterations increases, and the control parameter α decreases. The simulation results show that the optimized support vector machine regression prediction model improves the accuracy of microwave heating lignite temperature prediction, and provides a mathematical model for the study of microwave drying lignite control method.

    Thermodynamic analysis of micro tri-generation system based on SOFC/MGT/ORC
    YOU Huailiang, HAN Jitian, LIU Yang
    2018, 69(S2):  300-308.  doi:10.11949/j.issn.0438-1157.20181101
    Abstract ( 60 )   PDF (862KB) ( 36 )  
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    Thermodynamic analysis of a micro tri-generation system comprising of a solid oxide fuel cell (SOFC), a micro gas turbine (MGT), an organic Rankine cycle (ORC), and heat recovery devices for use as combined generation of cooling, heating and power is investigated in this paper. The mathematical model of the tri-generation system is developed and validated, the input parameters of system under the design condition are exhibited. A parametric study is performed to observe the effects of some key parameters such as the fuel flow rate, fuel utilization factor, steam to carbon ratio and compressor pressure ratio on the evaluation criteria of the system and its components. Results show that under the design conditions the system electricity and exergy efficiency are 69.12%, 64.4% respectively in summer mode while at the same time the overall efficiency of the system can reach 92.65% which is 13.1% higher than that in winter.

    Simulation calculation and analysis on self-pressurization system of LNG vehicle storage tank
    FANG Ping, CHEN Yu
    2018, 69(S2):  309-315.  doi:10.11949/j.issn.0438-1157.20181159
    Abstract ( 44 )   PDF (1767KB) ( 25 )  
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    Analyse the dynamic change of pressure and temperature in the working tank of the self-pressurizing system of liquefied natural gas (LNG) vehicle, using the simulation software SindaFluint to model and calculate the classical self-pressurization process based on lumped parameter method. The variation of pressure and temperature in the tank at different speeds and ambient temperatures is studied. The results show that the pressure fluctuation frequency in the tank changes from fast to slow in the process of self-pressurization, and the pressure becomes more and more stable with the continuation of the pressurization process. The temperature of the gas phase fluctuates synchronously with the pressure, while the main temperature of the liquid phase remains basically unchanged at 112.5 K. The higher the speed, the greater the frequency of pressure fluctuation in the tank. However, the environmental heat leakage has little effect on the self-charging system.

    Dynamic characteristics simulation of marine turbocharger under process of rapid load reduction
    ZHANG Guolei, SUN Rui, ZHANG Xiaoyu, FENG Yongming, MA Qingyang
    2018, 69(S2):  316-323.  doi:10.11949/j.issn.0438-1157.20180867
    Abstract ( 29 )   PDF (709KB) ( 24 )  
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    It is so important for marine turbocharger unit to maintain a reasonable ratio of wind to fuel oil, ensure normal combustion and avoid surge in the compressor in the process of rapid load reduction. A simulation model consisting of supercharged boilers and turbocharger unit was built. The response pattern of marine turbocharger unit in different reduction amplitude of load was researched. The simulation results show as follows. The load of the power system is reduced from 100% to 20%,the bypass valve is continuously opened for approximately 5 s to exhaust excess air. In the process of rapid load reduction, the greater the amplitude of the load reduction, the smaller the surge margin of the compressor and more likely the compressor is to surge. The lower the final stable load of the system, the smaller the surge margin of the compressor and more likely the compressor is to surge.

    Spontaneous path selection for hazardous chemical transportation based on quasi-decision tree pruning
    XU Wenxing, LIANG Jingjing, BIAN Weibin, DAI Bo, TAO Guanliang, LIU Cai
    2018, 69(S2):  324-329.  doi:10.11949/j.issn.0438-1157.20181243
    Abstract ( 14 )   PDF (1638KB) ( 28 )  
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    Under the premise of ensuring the safety of hazardous chemicals transport vehicles, in order to solve the path optimization problem more quickly, a quasi-decision tree pruning based optimization method is proposed. Based on the overall planning and local optimization of the vehicle planning program, in order to take full use of the optimal path information of the initial planning, during the transportation of hazardous chemicals vehicles, a quasi-decision tree pruning method is proposed for local optimization, thus the searching speed is improved. The feasibility of this method was verified by path planning between Beijing Petroleum Co. Ltd. of China Aviation Oil and Beiyuan gas station of China Sinopec.

    Simulation and optimization of energy utilization system of 25000 tons of LNG powered chemical tanker
    YAO Shouguang, HANG Jianwei, FENG Guozeng, XU Jinjin, GU Conghui
    2018, 69(S2):  330-340.  doi:10.11949/j.issn.0438-1157.20181166
    Abstract ( 52 )   PDF (1070KB) ( 29 )  
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    25000 tons of liquefied natural gas (LNG) powered chemical tanker was studied. After analysis of the original ship exhaust gas system and high temperature cooling water system, considering the residual heat resources of the original ship and the unused LNG cold energy, combinations such as exhaust power turbine, LNG cold energy generation ORC, freezing water desalination,high and low temperature cold storage and air-conditioning systems were installed to meet the demand of power generation, desalination, cold storage and air-conditioning in this ship. Also, five kinds of energy system cascade utilization schemes of LNG cold energy were put forward. Through the simulation calculation and comparative analysis of software HYSYS, aspects of exergy efficiency and economy of each scheme were evaluated. The result showed that low temperature cold storage + high temperature cold storage + air conditioning system was the best in economy and exergy efficiency. The exergy efficiency of new system can be improved to 62.87% after optimization. At the same time, the annual economic income can reach 12.2785 million CNY.

    Performance of combined cooling, heating and power system based on SOFC/GT/TCO2 integrated power cycle and LiBr-water absorption chiller
    LIU Yang, HAN Jitian, YOU Huailiang
    2018, 69(S2):  341-349.  doi:10.11949/j.issn.0438-1157.20181102
    Abstract ( 102 )   PDF (842KB) ( 50 )  
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    A novel combined cooling, heating and power system is proposed. The waste heat of the exhaust gas from the SOFC/GT hybrid system is recovered by a transcritical CO2 cycle and a LiBr-water absorption chiller for cooling, heating and power supply. Thermodynamic mathematical models of the CCHP system are developed, then energy and exergy analyses are used to analyze the performance of the CCHP system. The effect of air-fuel ratio, SOFC pressure, CO2 flow rate, CO2 split ratio and the outlet pressure of the TCO2 pump on the performance of the entire system are studied. The results show that the overall energy utilization, the net power generation and the exergy efficiencies of the entire system can reach 108.5%, 70.79% and 68.29%, respectively, under the specified condition. The overall energy utilization efficiency can be improved by increasing air-fuel ratio or CO2 split ratio, and decreasing SOFC pressure, CO2 flow rate or the outlet pressure of the TCO2 pump. The net power generation and the exergy efficiencies can be improved by increasing SOFC pressure or the outlet pressure of the TCO2 pump, or by decreasing air-fuel ratio. The net power generation and the exergy efficiencies first decrease and then increase with the increase in CO2 flow rate or CO2 split ratio.

    Intrusion detection of industrial control system based on PSOGSA feedforward neural network
    XU Wenxing, WANG Wanhong, WANG Fang, LIU Cai, JING Shaoxing, ZHAO Guoxin
    2018, 69(S2):  350-357.  doi:10.11949/j.issn.0438-1157.20181244
    Abstract ( 14 )   PDF (565KB) ( 29 )  
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    Aiming at the increasingly serious safety situation of industrial control system (ICS) in petrochemical industry, a forward neural network (FNNPSOGSA) based on particle swarm optimization (PSO) and universal gravitation search algorithm (GSA) is proposed to solve the problem of intrusion detection. A hybrid algorithm based on PSO and GSA is proposed by using the global optimization ability of GSA and the fast local convergence of PSO. PSOGSA is used as a new training method of FNNs to study the effectiveness of FNNPSOGSA model in practical engineering application scenarios. By comparing the FNNPSOGSA prediction results with the FNNPSO, FNNGSA and the improved FRGNN (K-NN) and FRGNN (Naive Bayes) prediction results in the reference literature, the results show that PSOGSA is feasible in training FNNs and has higher prediction accuracy and more generalization ability. The algorithm is applied to attack prediction in intrusion detection of industrial control system (ICS), and simulation study is carried out using industrial intrusion detection standard data set. The results show that the algorithm can achieve very good results in intrusion detection of industrial control systems.

    Simulation of initiative counter steam control during process of rapid deceleration in ship
    ZHANG Guolei, QUE Chenyu, TAN Xiu, LI Jian, SONG Fuyuan, JIANG Zhengyue
    2018, 69(S2):  358-364.  doi:10.11949/j.issn.0438-1157.20180898
    Abstract ( 23 )   PDF (648KB) ( 24 )  
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    The initiative counter steam control is an effective measure to ensure the system running correctly through avoiding the rise sharply of drum pressure during the rapid deceleration of steam power system. The simulation models of composition units were built including the supercharged boiler, main steam turbines, valve, condenser. The response pattern of steam power system on the different operating conditions of counter steam was researched. The results show that the max maximum opening of astern-valve should be 30% to 35% and the holding time of keeping the astern-valve at maximum is as short as possible.

    Experimental analysis of anti-dust property on superhydrophobic surfaces
    WU Yanpeng, GUO Zhanchuang
    2018, 69(S2):  365-372.  doi:10.11949/j.issn.0438-1157.20181105
    Abstract ( 49 )   PDF (903KB) ( 25 )  
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    In this paper, superhydrophobic surfaces are prepared by chemical vapor deposition on template, and the anti-dust property of superhydrophobic surfaces is experimentally studied. The static contact angle of superhydrophobic surfaces is 157° and its roll-off angle is 2.6°. The superhydrophobic surfaces and bare glasses with different tilt angles are placed in the ventilated laboratory for a period of time. Then the mass, quantity and diameter of the dust particles on the surfaces are analyzed with electronic balance and micro-imaging technology to investigate the anti-dust property of superhydrophobic surfaces directly. The results show that the dust accumulation of superhydrophobic surfaces are 46%-80% of bare glass surfaces, which can effectively reduce the dust quality of 20%-54%; the shorter the time is and the bigger the tilt angles are, the more excellent the effectiveness of anti-dust property of superhydrophobic surfaces are; the changes of the dust diameter of these two kinds of surface are almost the same, but the dust quantity of superhydrophobic surfaces are 24%-83% of bare glass surfaces, which indicates that the dust quality of superhydrophobic surface is smaller than bare glass surfaces' because of the low amount of dust. The anti-dust property of superhydrophobic surfaces is remarkable.

    Analysis on performance of thermally driven cooling and power cogeneration system with dual working mode
    PAN Quanwen, WANG Ruzhu
    2018, 69(S2):  373-378.  doi:10.11949/j.issn.0438-1157.20181115
    Abstract ( 44 )   PDF (737KB) ( 27 )  
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    Power and cooling cogeneration system using organic Rankine cycle (ORC) and adsorption system can make a better utilization of low grade heat. A thermally driven cooling and power cogeneration system with dual working mode was proposed for application cases with/without cooling demand. In the cogeneration mode, power and cooling is yielded by ORC and adsorption systems, respectively. In the power-only generation mode, cooler of ORC system is cooled by the output chilled water of adsorption system so that working fluid condensation temperature of ORC system is lower and more power generation is obtained. A mathematical model was built and the system performance was numerically studied and analyzed. The simulation results show this ORC-adsorption system with dual working mode has better performance than solo ORC, adsorption and traditional ORC-adsorption systems, especially under the conditions of high hot water temperature.

    Comparisons of rotary and scroll compressors in small air-source heat pumps for low ambient temperature
    LI Minxia, LI Yuhan, MA Yitai, WANG Pai, WANG Feibo, ZHAN Haomiao
    2018, 69(S2):  379-387.  doi:10.11949/j.issn.0438-1157.20181091
    Abstract ( 75 )   PDF (2390KB) ( 26 )  
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    An air-source heat pump (ASHP) is an energy-saving device that utilizes energy of higher grade to move energy from a lower heat source, which is air, to a higher heat source. This article describes the concept of small-scale ASHP for low ambient temperature (input power at 1-4 kW, environment temperature down to -20℃) and its energy efficiency evaluation method. Two suitable types of fully enclosed compressors are introduced:rotary compressors and scroll compressors. The compression principles of the two compressors were compared. Through technical analysis and product research, the basic characteristics, the enhanced vapor injection (EVI) and the liquid injection technologies, the frequency conversion technology and the applicable operating conditions of the two compressors were analyzed. The characteristics of their variable compression ratio (VCR) are described. The manufacturing processes of the two compressors are compared. A comparison of applicability for the two compressors is presented.

    Influencing factors of direct oxygen enrichment device based on electro-osmosis
    LI Yi, ZHANG Xiaosong
    2018, 69(S2):  388-393.  doi:10.11949/j.issn.0438-1157.20181057
    Abstract ( 58 )   PDF (558KB) ( 30 )  
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    With the continuous emergence of global climate and environmental issues, the issue of CO2 emission reduction has attracted more and more attention from all sectors of society. Among them, thermal power plants that use burning minerals as the main energy source are the largest sources of CO2. Reducing CO2 emissions from thermal power plants is also of great significance in mitigating the greenhouse effect. Currently, effective measures to achieve CO2 emission reduction in thermal power plants are oxygen-enriched combustion. Oxygen enrichment technology has important practical value for reducing CO2 emissions from thermal power plants. In this paper, based on the traditional electro-osmosis solution dehumidification technology, a new type of oxygen enrichment method based on electro-osmosis directly acting on the air is proposed. According to theoretical analysis, it is found that the oxygen enrichment effect of the device can be significant increased by improving the air humidity or electric field strength when the electric field intensity is less than 50 kV.

    Performance of R744 commercial centralized refrigeration systems
    LIN Liguan, DAI Yanjun, HAFNER Armin
    2018, 69(S2):  394-401.  doi:10.11949/j.issn.0438-1157.20181127
    Abstract ( 56 )   PDF (854KB) ( 26 )  
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    Three R744 supermarket refrigeration systems are compared, including conventional booster system (CB), booster system with parallel compression (PC) and multi-ejector booster system with parallel compression (EJ). The parallel compressors in PC and EJ systems work under lower pressure ratio and consequently the energy of compressors decreases. In EJ systems, expansion valves are substituted by ejectors, so that the irreversible loss in the system could be lower. The air-conditioning system integrated with PC and EJ system are also discussed respectively. The optimal high side pressure of each system is confirmed. The value of high side pressure becomes larger when the outdoor temperature increases. When the ambient temperature is fixed, the multi-ejector system features the lowest high side pressure. The power consumption of each system is obtained by the simulation models. The results indicate that the power consumption of PC could be decreased, ranging from 6.8% to 12.3% compared to CB. And for EJ, the power consumption is even smaller, where the gap is 6.3% to 17.5%. Compared with HFC (hydrofluorocarbon), such as R404a, the R744 supermarket refrigeration system is of great energy saving potential in warm climates.

    Numerical simulations of desublimation of CO2 or water vapor in liquid methane with cellular automata method
    XU Xiaoying, YOU Hao, WANG Wen
    2018, 69(S2):  402-407.  doi:10.11949/j.issn.0438-1157.20181170
    Abstract ( 41 )   PDF (2726KB) ( 25 )  
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    The physical mechanism of crystal growth was analyzed using heat and mass transfer equations, Navier-Stokes equations and growth dynamics in this paper. Cellular automata (CA) method was used to form a phase change model. The desublimation process of water vapor and CO2 in liquid methane is observed by computer simulation. Not only the two-dimensional simulation results of ice crystal growth, but also the two-dimensional and three-dimensional simulation results of CO2 crystal growth in liquid methane were obtained. Results show that this model could simulate water and CO2 crystallization under sub-cooled and supersaturated environment. The two-dimensional ice crystal result is very similar to the real ice crystal with topological structure. CO2 crystal has simpler structure and the simulation results confirm to the characters of authentic CO2 crystal. This model can be improved to analyze the water and CO2 crystallization in liquid natural gas (LNG) and may be used to improve the technology processes of storage, transportation and utilization of LNG.

    Thermodynamic analysis of novel refrigeration cycle based on physicochemical thermal effect
    ZHOU Jie, YIN Yonggao
    2018, 69(S2):  408-412.  doi:10.11949/j.issn.0438-1157.20181300
    Abstract ( 38 )   PDF (486KB) ( 31 )  
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    A novel refrigeration cycle based on physicochemical thermal effect was proposed. This cycle utilizes the endothermic effects of the decomposition reaction of ammonium carbamate as well as the vaporization of the reaction product to refrigerate, and releases heat through the reverse reaction. The thermodynamic performance of the cycle was investigated and evaluated under different operating conditions. The results show that the temperature difference between endothermic and exothermic reaction should not be higher than 40℃. The intermediate pressure has a significant influence on the coefficient of performance (COP) of the system and there is an optimal intermediate pressure to achieve the maximum COP. The optimal intermediate pressure is determined, and the optimal intermediate temperature is the equilibrium temperature at this pressure. Besides, the novel cycle has a higher COP than the theoretical cycle of the single-stage vapor compression refrigeration system by about 20%. Compared with the cycle utilizing the phase change of the material to refrigerate, this novel cycle has better prospects for development.

    Economic analysis of pressure energy utilization in natural gas distribution station
    MA Shuaijie, LIN Wensheng
    2018, 69(S2):  413-419.  doi:10.11949/j.issn.0438-1157.20181146
    Abstract ( 36 )   PDF (547KB) ( 24 )  
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    There are various ways to utilize pressure energy in natural gas distributing stations. It is necessary to select the most economical system according to the conditions of station. Taking a distribution station with the flow rate of 106 m3·d-1 as an example, HYSYS is used to calculate the output of three systems (power generation by expanding directly, dry ice production and liquefied natural gas production) under different initial pressures and pressure drops. This paper uses the net present value to analyze the economy of these three systems and choose the most suitable one based on their advantages and disadvantages. The results show that utilizing pressure energy to produce LNG has the best economy, and it has low requirement for the initial pressure and pressure difference; only when the initial pressure and pressure difference reach certain conditions, utilizing pressure energy to generate power can be valuable; only when the initial pressure and pressure difference reach certain conditions, the system to produce dry ice can work. When the initial pressure and differential pressure are in moderate conditions, the economy of direct expansion power generation is better than that of producing dry ice. When the initial pressure and pressure difference are large enough, the system producing dry ice is more economical than power generation.

    Alternative scheme and dehumidification and regeneration performance validation for economic multi-component solution
    WANG Mu, YIN Yonggao, GUO Xiaoshuang, CHEN Tingting
    2018, 69(S2):  420-424.  doi:10.11949/j.issn.0438-1157.20181301
    Abstract ( 76 )   PDF (472KB) ( 31 )  
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    This paper aims to search for a more economical multi-component solution to replace single solution and validate its dehumidification and regeneration performance. A configuration scheme for multi-component solution is forecasted by simple mixing rule. Moisture content of outlet air is used as evaluation indexes. Experiments are carried out to verify the dehumidification capacity and regeneration capacity between single solution and multi-component solutions. 43%, 45% and 48% LiCl/CaCl2 multi-component solutions are substitutions for 39% LiCl solution. 51% LiBr/CaCl2 multi-component solution is substitution for 52% LiBr solution. Taking dehumidification performance, regeneration performance and economy into consideration, 48% LiCl/CaCl2 multi-component solution has 29.5% higher regeneration capacity than 39% LiCl solution and one third price of 39% LiCl solution. Since it has the best regeneration capacity, lowest price and slightly worse dehumidification capacity, it is the best substitute for dehumidifier. 51% LiBr/CaCl2 multi-component solution has 50.8% higher regeneration capacity than 52% LiBr solution. It also has similar dehumidification capacity to 52% LiBr solution and half price of 52% LiBr solution. It's a good substitute for dehumidifier.

    Process of BOG treating in LNG receiving station with normal temperature compressor
    XIONG Xiaojun, HE Ting, LIN Wensheng
    2018, 69(S2):  425-430.  doi:10.11949/j.issn.0438-1157.20181153
    Abstract ( 63 )   PDF (569KB) ( 30 )  
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    A certain amount of boil-off gas (BOG) will be produced during the operation of LNG receiving station. At present, three processes of torch, compression and re-condensation are commonly used to process BOG. Due to the low temperature of BOG, the cryogenic compressor is widely used in the compression process. However, the cost of cryogenic compressor reduces the economic benefits of LNG receiving station. Therefore, this paper proposes a process for BOG treating using a normal temperature compressor. The process utilizes the high temperature BOG of the compressor outlet to heat the low temperature BOG at the inlet of the compressor. On the one hand, the inlet temperature of the compressor is increased, which makes it possible for the normal temperature compressor to replace the cryogenic compressor; on the other hand, the BOG temperature at the outlet of the compressor and the cooling capacity required for the BOG re-condensation is reduced. Both cryogenic temperature compression and normal temperature compression process are simulated by HYSYS software. The results show that the normal temperature compressor process is more advantageous for small LNG receiving stations.

    Applications of QRA in LNG projects and existing problems
    YANG Xiaodong, LU Xuesheng, SHU Xiaoqin, BAI Gailing, LIN Wensheng, LIU Shimin
    2018, 69(S2):  431-435.  doi:10.11949/j.issn.0438-1157.20181144
    Abstract ( 68 )   PDF (496KB) ( 35 )  
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    Through the comparisons of the prescriptive code requirements of NFPA59A and risk-based method of QRA, this paper gave the introduction of QRA application in LNG projects, e.g., in LNG facility sitting studies. A QRA example of a domestic LNG receiving terminal sitting study has been given to illustrate its significance. The existing problems of QRA applications in LNG projects have been illustrated through discussion on DNV QRA analysis results of HRCD database. A few suggestions were proposed for QRA developments in LNG applications.

    Influence of load characteristic on economic operation of LNG receiving terminal
    CHEN Taoqiang, LI Ning, WEI Guanghua, GAO Yifeng, LIU Ben, HUANGFU Lixia, GUO Kaihua
    2018, 69(S2):  436-441.  doi:10.11949/j.issn.0438-1157.20181126
    Abstract ( 37 )   PDF (501KB) ( 22 )  
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    For a specific environment gas pipe network and terminal equipment, the operation of the terminal strategy depends on the load characteristics. Study on the best operating strategy of different load characteristics has a great significance to energy-saving. Based on the periodicity of daily load and peak and valley price, the optimization mathematical model is established and the universal optimization criterion is derived. In addition, the optimization scheme of three typical working conditions is obtained with the dynamic simulation system, and also the universal optimal operation scheme of day and month is obtained. The load characteristic curve equation is derived by analyzing the field data, which allows of the optimization of each kinds of load characteristic. The calculation shows that the optimal operation scheme can save up to 12% of the daily cost compared with the on-site operation strategy. According to the typical monthly load distribution in summer, the optimal scheme can save 6.3% per month compared with the on-site strategy.

    Long-distance transportation of liquefied natural gas (LNG) and cold energy utilization
    DU Xu, CHEN Yu, JU Yonglin
    2018, 69(S2):  442-449.  doi:10.11949/j.issn.0438-1157.20181160
    Abstract ( 39 )   PDF (1096KB) ( 24 )  
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    The end temperatures and the pressure drop of the long-distance pipeline for the LNG transportation, at different thickness of the thermal insulation layer with different external environment temperatures, are obtained by using Sinda/Fluint software. The simulation results show that the LNG temperature increase is 4.068℃, and the pressure drop is 2.52 MPa at thickness of the thermal insulation layer of 0.1 m and the outside temperature of 33.5℃, after 12 km long distance transportation of LNG at inlet temperature of -160℃ and inlet pressure of 6.6 MPa. Taking into account of these conditions, the LNG cold energy utilization scheme at downstream of the pipeline is designed by HYSYS software, for a total cold capacity of 300000 m2 operating respectively at cold storage, normal temperature storage and high temperature storage, at around 12 km away from the LNG receiving station.

    Crystallization characteristics of dynamic formation process of ice slurry in small-scale ice making machine
    LIU Ruijian, LIANG Kunfeng, JIA Xueying, WANG Lin
    2018, 69(S2):  450-458.  doi:10.11949/j.issn.0438-1157.20181143
    Abstract ( 37 )   PDF (4653KB) ( 23 )  
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    The ice slurry was prepared by using the small scale ice making machine. The effects of crystallization time, second refrigerant temperature, additive type and concentration, and scraping speed on the dynamic generation process of the ice slurry were investigated. The heat balance method was used in the study. The ice packing factor at different times of the crystallization process was microscopically photographed, and the equivalent diameter of the ice crystal size was obtained based on image processing. The experimental results show that the cooling rate of the ice-making solution is less affected by external conditions during the test time of the dynamic crystallization process, but the type and concentration of the additive have a great influence on the phase change crystallization temperature and supercooling degree of the ice-making solution. The ice packing factor and ice crystal size of the solution increase with time. The temperature of the brine, the type and concentration of the additive have a great influence on the ice content of the solution, and the factors that have the greatest influence on the ice crystal size are the scraping speed and the additive concentration. When the crystallization process is carried out for 30 min, the ice content of the solution reaches 25%, and the ice crystal size can reach about 0.12 mm.

    Characteristics of cold storage LNG cold energy utilization air conditioning system for heavy truck under whole road condition
    WANG Fang, LI Mengchu, ZHANG Yanling, ZHU Caixia, WANG Shuaiqi
    2018, 69(S2):  459-465.  doi:10.11949/j.issn.0438-1157.20181136
    Abstract ( 51 )   PDF (1946KB) ( 24 )  
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    In order to meet the refrigeration demand of LNG heavy truck driving space, an air conditioning system for the cold energy of LNG heavy truck with cool storage function is designed, and the whole road traffic model is constructed, and the refrigeration performance and the influencing factors of the LNG heavy truck in the uphill section, the stationary section and the downhill section are analyzed. The results show that the cooling capacity of LNG heavy truck is 6.150 kW in the upper section of the air-conditioning system, the cold storage capacity is 0.551 kW. The air conditioning refrigeration capacity of the stationary section is 4.201 kW, the cold storage capacity is 0.420 kW. The cooling capacity of the downhill section is 2.902 kW, and the cooling capacity of the regenerator is greater than that of 0.598 kW. The system can control the storage quantity rationally by controlling strategy, and meet the demand of stable cooling of the air conditioning system under the whole road condition of LNG heavy truck.

    Hydrogen production via sorption-enhanced steam reforming of tar
    XIE Huaqing, ZHANG Weidong, LIN Heyong, YU Qingbo
    2018, 69(S2):  466-472.  doi:10.11949/j.issn.0438-1157.20181003
    Abstract ( 46 )   PDF (928KB) ( 25 )  
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    The sorption-enhanced steam reforming process was applied to the tar removal to produce high-purity hydrogen. In this study, the reforming catalyst was Ni/Mg-Ca12Al14O33 prepared by solid-state reaction method, and the CO2 sorbent was CaO-Ca12Al14O33 prepared by sol-gel method. The effects of temperature, S/C ratio (the mole ratio of the steam to the carbon in the reaction system) and the WHSV (mass hourly space velocity) on enhancing hydrogen production from tar reforming. The results showed that the addition of the CO2 sorbent can improve the tar reforming efficiency, with the H2 yield and volume fraction increased significantly. Especially, the H2 volume fraction reached over 95%. As the S/C ratio rose and the WHSV declined, the hydrogen production was accelerated, for both of the common steam reforming and the sorption-enhanced reforming. And, for the two processes, when the S/C ratio reached over 12:1 and the WHSV reached below 0.128 h-1, the change of the reforming efficiency was no longer distinct. Compared to the common steam reforming, the best temperature to produce H2 was decreased for the sorption-enhanced reforming, and the H2 yield at 800℃ can reach 87.35%. Compared to thermodynamic results, the H2 yields from the experiment were lower, but the sorption-enhanced reforming can narrow the gap between the experimental and thermodynamic values.

    Analysis of temperature and pressure variation of type C independent cargo tank for LNG carrier
    WANG Tao, AN Yuhui, CHANG Xuanyu
    2018, 69(S2):  473-479.  doi:10.11949/j.issn.0438-1157.20181114
    Abstract ( 42 )   PDF (707KB) ( 24 )  
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    For semi-refrigerated and semi-pressurized liquified natural gas(LNG) carrier without liquefaction systems, the temperature and pressure in the tank will gradually increase in voyage, with the density and volume of the liquid cargo will change accordingly. In this paper, a simplified method for calculating the daily variation of temperature and pressure of a 14000 m3 LNG carrier is proposed. The calculation results show that the deviation of the daily variation of temperature and pressure calculated by the simplified method is small under the condition of higher loading rate, which can meet the basic requirements of engineering calculation. The relationship between the loading rate and the maximum allowable relief valve setting and the influence of the loading rate on the temperature and pressure of the liquid cargo are also discussed and analyzed.

    Experimental investigation on refrigeration performance of R290 linear compressor
    ZOU Huiming, LI Xuan, TANG Mingsheng, SHAO Shuangquan, TIAN Changqing
    2018, 69(S2):  480-484.  doi:10.11949/j.issn.0438-1157.20181060
    Abstract ( 50 )   PDF (2193KB) ( 31 )  
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    According to the cooling demand of commercial refrigerator, an R290 linear compressor is developed and the experimental investigation on its cooling performance is carried out. The experimental results show that cooling capacity and COP of the linear compressor are 604 W and 1.42 on the rating conditions. Its COP decreases with the decreasing of cooling capacity and the COP is just about 1.02 with 40% cooling capacity. As the power frequency is lower than the nature frequency of linear compressor, cooling capacity and COP decreases greatly. The analysis on power consumption indicates that it is necessary to enhance the linear motor performance and reduce the gap between the piston and cylinder to improve the efficiency of linear compressor.

    Applicability of heat pump air-conditioning system with groundwater preheating fresh air
    WANG Lin, HE Hui, WANG Zhanwei, SONG Zun, LIANG Kunfeng, MA Aihua
    2018, 69(S2):  485-491.  doi:10.11949/j.issn.0438-1157.20181165
    Abstract ( 46 )   PDF (778KB) ( 22 )  
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    The traditional groundwater source heat pump air conditioning system directly uses groundwater to heat the evaporator of the heat pump unit, and the low-grade thermal energy stored in the groundwater is not effectively utilized. Given those problems, a novel groundwater source heat pump air-conditioning system preheating fresh air with groundwater was proposed. The primary feature of the presented system is the cascade utilization of low-grade energy, namely the novel system preheats fresh air by groundwater at first, then the groundwater is recycled by the heat pump unit for the secondary utilization, which is beneficial to improve the utilization rate of low-grade thermal energy of groundwater and remarkably save energy consumption of heat pump unit. The operational principle of the novel system and air treatment method in the heating mode was analyzed and the hourly heat loads of an academic communication center in the whole heating season (120 days) in four selected typical cities (Wuhan, Changde, Beijing, Zhengzhou) was simulated with DeST, moreover, a comparative study on heating characteristic and energy consumption between the novel system and conventional groundwater source heat pump air-conditioning was conducted. The results showed that the energy consumption of the novel underground water source heat pump air conditioning system is much lower than that of the conventional groundwater source heat pump air conditioning system. The innovative groundwater source heat pump air conditioning system is preferred for hot summer and cold winter area and cold region in China. Moreover, the energy saving rate is more than 50% in each region, and it should be noted that the energy saving effect is better in hot summer and cold winter area than cold region.

    Preparation and characterization of expanded graphite/metal organic frameworks composite sorbent
    XU Jiaxing, CHAO Jingwei, LI Tingxian, WANG Ruzhu
    2018, 69(S2):  492-499.  doi:10.11949/j.issn.0438-1157.20181174
    Abstract ( 64 )   PDF (2953KB) ( 44 )  
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    Low density and low thermal conductivity are common drawbacks of powder metal organic frameworks (MOFs), which is one of key point limited the application of MOFs. MIL-101(Cr) as a typical water adsorption MOFs with high adsorption capacity is the major study object in this work. Two methods of directly dry-mixing and soaking are utilized to composite expanded graphite (EG) with MOFs, after compression by mold, a series of composite sorbents pellets with different EG content and packed density are developed. The optical microscope is utilized to observe the structure of materials, by which the influences of packed density and EG content on microscale structure are analyzed. The tests of saturated sorption capacity of pure MOFs and composites are carried out in a constant temperature and humidity chamber, whose results indicates the sorption capacity of pure MOFs will apparently reduce if the compression pressure is higher than 3 MPa. Accordingly, composite sorbents are prepared under relatively low compression pressure, whose sorption capacities are decrease with the increase of EG content, which is only caused by the decrease of MOFs content while there is no negative effects of EG on MOFs adsorption. Volume method is applied in adsorption kinetics study, which reveals the adsorption rates of pellets pure MOFs are much lower than powder pure MOFs. However, the composites shows 2.7 times higher surface diffusive coefficient than pellet pure MOFs ascribed of the appearance of more mass transfer channels caused by compression with EG. The results of thermal conductivity measurements of composite sorbent illustrate that thermal conductivities are obviously enhanced with the increase of EG content while a much smaller enhancement is observed by increasing packed density. Comparing with pure MOFs, the developed composites by dry-mixing method with EG mass content of 50%, with packed density of 408 kg·m-3 shows extraordinary high thermal conductivity of 2.76 W·m-1·K-1, which is 22 times higher than pure MOFs.

    Simulation analysis of influence of thermal insulation material breakage on boil-off rate for B type LNG carrier
    FU Yunzhun, LI Pengkui, JU Yonglin
    2018, 69(S2):  500-504.  doi:10.11949/j.issn.0438-1157.20181113
    Abstract ( 36 )   PDF (11123KB) ( 44 )  
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    Based on the analyses of the containment system of a new independent type B liquefied natural gas (LNG) carrier, the distribution of temperature field and heat transfer calculation were analyzed in different kinds of conditions using the method of computational fluid dynamics (CFD) numerical simulation. In addition, the boil-off rate under different conditions was calculated. The results show that the evaporation rate of the LNG carrier is increased by 12% compared with that of the intact insulation layer, when the thickness of the insulating layer was 400 mm, the air temperature was 5℃ and the insulation layer is damaged by 1 m2. The thermal insulation capacity of insulation materials and the insulation layer damage had great influence on the heat transfer and evaporation rate of LNG cargo hold.

    Effect of methane concentration on diamond film in high power microwave plasma system
    LUO Kai, WANG Jianhua, YU Junhuo, WENG Jun
    2018, 69(S2):  505-511.  doi:10.11949/j.issn.0438-1157.20181169
    Abstract ( 39 )   PDF (5168KB) ( 26 )  
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    In a laboratory-made 10 kW microwave plasma chemical vapor deposition (MPCVD) apparatus, the influence of methane concentration on the growth of diamond film under a high-power microwave plasma was analyzed. The characteristics of high-power microwave plasma discharge environment were diagnosed by plasma emission spectroscopy. At the same time, the morphology and quality of diamond films obtained under different deposition conditions were characterized by SEM and Raman spectroscopy to determine diamonds in a highpower microwave plasma environment. The optimal methane concentration range for membrane growth was abtained. Experiments show that when microwave power is kept at 5000 W, when the CH4/H2 is less than 1%, the secondary nucleation phenomenon in the diamond film is obvious, and the grain size is small; when the CH4/H2 is more than 2.5%, the diamond film can get larger crystal grains, but easy to produce germanium crystals; when CH4/H2=1.5%-2%, diamond films with complete crystal grains and high quality can be obtained.

    Influences of micro-fin structure on flash boiling characteristics of liquefied gas under tank depressurization
    REN Tao, DUAN Zhongdi, DING Guoliang
    2018, 69(S2):  512-516.  doi:10.11949/j.issn.0438-1157.20181137
    Abstract ( 55 )   PDF (2083KB) ( 36 )  
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    The boiling liquid expanding vapor explosion (BLEVE) is a most common hazard in liquefied gas storage and transportation, and its explosion energy depends on the superheat degree of the metastable liquid at the loss of containment. For preventing the flash boiling of liquefied gas, this paper presents a new method by using micro-fin surface to promote nucleation in superheated liquid. A visualized experimental rig is established. The nucleation process on micro-fin surface under rapid depressurization is observed and compared to that on smooth surface; the transient pressure evolution in the container is measured. The results show that the onset of nucleation on micro-fin surface is about 50 ms earlier than that on smooth surface. The adopted micro-fin surface in the experiments reduces the pressure rebound and the maximum liquid superheat degree by up to 24.1% and 21.7% respectively among the release pressures of 200-500 kPa.