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Table of Content
05 April 2016, Volume 67 Issue 4
    CIESC February(HUAGONG XUEBAO) Vol.67 No.4 February 2016
    2016, 67(4):  0-0. 
    Abstract ( 51 )   PDF (1990KB) ( 594 )  
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    Present situation and prospect of recovering valuable elements from cyanidation tailing
    LÜ Cuicui, DING Jian, FU Guoyan, LIU Ya, LU Yonggang, QIAN Peng, YE Shufeng
    2016, 67(4):  1079-1089.  doi:10.11949/j.issn.0438-1157.20151352
    Abstract ( 177 )   PDF (1722KB) ( 495 )  
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    The cyanidation tailing is a staple hazardous solid waste. It contains valuable elements, such as copper, lead, zinc, gold, silver, sulfur, iron, etc.. Comprehensive utilization of cyanidation tailing not only recovers these valuable elements to achieve the maximum use of mineral resources, but also reduces its damage to the environment. In this paper, the characterization of cyanidation tailing was introduced. As the cyanidation tailing came from the gold extraction by cyanidation, the particle was very fine, and the residual cyanide in the tailing pulp was as much as 400 mg·L-1. Thus, appropriate pretreatment should be carried out, which can be classified as physical, chemical and special technical methods. The research status and existing problem of recovering copper-lead-zinc, sulfur-iron and gold-silver from cyanidation tailing were then presented in detail. Based on the existing problem of treating cyanidation tailing, the future research topics on the development of new flotation technological flowsheet, synthesis of new reagents and the reuse of ultimate tailing were proposed. The comprehensive utilization of cyanidation tailing would bring about economic and environmental benefits eventually.

    Viscosity and electrical conductivity of Betaine·HCl-6EG-nNiCl2·6H2O deep eutectic ionic liquids
    GONG Kai, HUA Yixin, XU Cunying, LI Jian, LI Yan, ZHOU Zhongren
    2016, 67(4):  1090-1097.  doi:10.11949/j.issn.0438-1157.20151264
    Abstract ( 132 )   PDF (607KB) ( 273 )  
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    The viscosity and electrical conductivity of Betaine·HCl-6EG-nNiCl2·6H2O deep eutectic ionic liquids, formed by adding nickel(Ⅱ) chloride hexahydrate (NiCl2·6H2O) into a deep eutectic solvent (DES) composed of Betaine hydrochloride (Betaine·HCl) and Ethylene glycol (EG) in 1:6 molar ratio, were reported at 303—353 K and 303—348 K with an interval of 5 K under atmospheric pressure. The viscosity and electrical conductivity associated with temperature and NiCl2·6H2O concentration were investigated, respectively. The results revealed that within the selected temperature and NiCl2·6H2O concentration ranges, Betaine·HCl-6EG-nNiCl2·6H2O deep eutectic ionic liquids showed low viscosities and good electrical conductivities. With increasing temperature, the viscosities decreased and electrical conductivities increased. The effect of temperature was more significant on viscosity than on electrical conductivity. The dependence of temperature of viscosity and electrical conductivity was found to be greatly described by Arrhenius empirical expressions. According to these expressions, the activation energies for viscous flow and conduction were calculated. With increasing NiCl2·6H2O concentration, the values of the activation energies for viscous flow and conduction increased. Because of the adding NiCl2·6H2O, the formations of the larger size complex ions reduced the concentrations of the effective conductive ions and increased the ionic radius, resulting in increasing viscosity and decreasing electrical conductivity.

    Measurement and correlation of liquid-liquid equilibrium data for acetic ether-resorcinol-acid brine system
    KONG Lingqi, WANG Yuanpu, CAO Wu, LI Yugang
    2016, 67(4):  1098-1102.  doi:10.11949/j.issn.0438-1157.20141904
    Abstract ( 124 )   PDF (425KB) ( 287 )  
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    Acetic ether was used as solvent for extraction of resorcinol under the environment of acid brine. Liquid-liquid equilibrium (LLE) data of acetic ether-resorcinol-acid brine quasi ternary system were determined at atmospheric pressure (101.33 kPa) and 313 K with the equilibrium method. The experimental data showed that the mutual solubility of acetic ether and water was increased with increasing resorcinol which reduced the extraction effect of the acetic ether on resorcinol, while the solubility of acetic ether in water was reduced in the existence of ammonium sulphate which was good for the extraction process. The experimental data were correlated with NRTL model and parameters were obtained. The calculation results agreed well with the experimental data, indicating that the models used were suitable for the system. The model also provided data for the design of extraction process of m-phenylenediamine hydrolysis for joint production of resorcinol with m-aminophenol.

    Thermodynamic analysis on synthesis of sulfolene by group-contribution method
    WANG Xiugang, SHEN Yang, TIAN Binghu, WU Fengchao, WU Jianhua
    2016, 67(4):  1103-1109.  doi:10.11949/j.issn.0438-1157.20151302
    Abstract ( 162 )   PDF (1095KB) ( 630 )  
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    The thermodynamic analysis of sulfolene synthesis reaction was carried out by group-contribution method. The reaction enthalpy, entropy, Gibbs free energy and equilibrium constant were calculated in the temperature range of 300—600 K and the pressure range of 0.1—10 MPa. The effects of temperature, pressure and reactant ratio on equilibrium conversion were also discussed. The calculation results indicate that sulfolene synthesis is a reversible exothermic reaction, and it is spontaneous when the temperature is less than 460 K at standard pressure. The reaction occurs more easily at lower temperatures and higher pressures. Temperature, pressure and the reactants ratio all show significant effect on equilibrium conversion, and the temperature is the most significant factor. Lower temperature, higher pressure and higher reactant ratio favor the promotion of equilibrium conversion, and the maximum equilibrium conversion is close to 1. The experimental results show good agreement with the thermodynamic calculation, and the relative deviation is less than 10%.

    Saturated vapor pressure, crystallization temperature and corrosivity of LiBr-[BMIM]Cl/H2O working pair
    LUO Chunhuan, ZHANG Yuan, SU Qingquan
    2016, 67(4):  1110-1116.  doi:10.11949/j.issn.0438-1157.20150230
    Abstract ( 124 )   PDF (553KB) ( 584 )  
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    In order to solve the problems of crystallization and corrosion for LiBr/H2O, LiBr-[BMIM]Cl/H2O and LiBr-[BMIM]Br/H2O were proposed as new working pairs. The influences of ionic liquids on crystallization temperatures and saturated vapor pressures of LiBr/H2O were investigated. The saturated vapor pressures, crystallization temperatures and corrosivity of LiBr-IL/H2O with a mass ratio of 2.5 were measured and compared with that of LiBr/H2O. The results showed that the saturated vapor pressures of [BMIM]Cl/H2O and [BMIM]Br/H2O were almost the same as that of LiBr/H2O with a 8%—9% lower concentration. In general operation concentration range, the crystallization temperatures of LiBr-[BMIM]Cl/H2O were about 30℃ lower than that of LiBr/H2O with the same absorption ability. Under the same corrosion conditions, the corrosion rate of carbon steel for LiBr-[BMIM]Cl/H2O was obviously smaller than that for LiBr/H2O, and the corrosion rate of copper for LiBr-[BMIM]Cl/H2O was nearly the same as that for LiBr/H2O. As an alternative working pair, LiBr-[BMIM]Cl/H2O has a great potential for absorption heat pump systems.

    Phase equilibria of quaternary system LiCl-LiBO2-Li2SO4-H2O at 298.15 K
    CAO Lina, LI Long, ZHANG Nan, GUO Yafei, DENG Tianlong
    2016, 67(4):  1117-1122.  doi:10.11949/j.issn.0438-1157.20151204
    Abstract ( 109 )   PDF (453KB) ( 340 )  
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    The phase equilibria and phase diagram of the quaternary system (LiCl-LiBO2-Li2SO4-H2O) at 298.15 K, which was not reported in the literature, were studied with the isothermal dissolution equilibrium method. Solubilities and physicochemical properties including refractive index (nD), density (ρ), pH and conductivity (κ) in the quaternary system were determined experimentally. According to the experimental data, the dry-salt diagram, water-phase diagram and the diagram of physicochemical properties versus lithium chloride concentration in the quaternary system were plotted, respectively. The experimental results showed that there were two invariant points named as invariant co-saturated point (Li2SO4·H2O + LiCl·H2O + LiBO2·2H2O) and incommensurate co-saturated point (Li2SO4·H2O + LiBO2·2H2O + LiBO2·8H2O), five univariant curves and four crystalline regions corresponding to Li2SO4·H2O, LiCl·H2O, LiBO2·8H2O and LiBO2·2H2O in the quaternary system at 298.15 K. Neither double salt nor solid solution was formed, and the phase diagram of this system at 298.15 K belonged to hydrate-type Ⅱ. The two kinds of hydrate lithium-containing minerals (LiBO2·2H2O and LiBO2·8H2O) were found for the first time. The salting-out effect of LiCl in the solution was obvious for the composition of Li2SO4. The diagram of physicochemical properties including nD, ρ, pH and κ versus composition shows that the physicochemical properties were changed regularly with increasing lithium chloride concentration in the solution and the singular values were achieved at the invariant points of the quaternary system at 298.15 K.

    Phase equilibria in quaternary system Na+,K+//Br-,SO42--H2O at 373 K
    CUI Ruizhi, SANG Shihua
    2016, 67(4):  1123-1128.  doi:10.11949/j.issn.0438-1157.20151183
    Abstract ( 76 )   PDF (453KB) ( 264 )  
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    According to the composition of the brine resources in the west of Sichuan Basin, phase equilibria in the quaternary system Na+,K+//Br-,SO42--H2O at 373 K is measured by the isothermal solution saturation method, and the solubilities and densities of the solution are determined experimentally. Using the experimental results, the dry salt phase diagram, water diagram and the densities versus composition diagram are obtained. In the phase diagram of quaternary system Na+,K+//Br-,SO42--H2O at 373 K, the double salt Na2SO4·3K2SO4 is found. There are three invariant points, seven uninvariant curves and five crystallization fields in the quaternary system. The five crystallization fields correspond to NaBr, Na2SO4, K2SO4, KBr and Na2SO4·3K2SO4(Gla), respectively. The crystallization field of NaBr has the smallest crystallization area, whereas the double salt Na2SO4·3K2SO4(Gla) has the biggest crystallization field in the quaternary system. It means that the double salt Na2SO4·3K2SO4(Gla) has the smaller solubility, and it can be easiest separated from solution. Compared with the two phase diagrams of quaternary system Na+,K+//Br-,SO42--H2O at 323 K and 373 K, the result shows that the numbers of invariant points, crystallization fields and unvariant curves are the same. The double salt all forms in the phase diagrams of quaternary systems at two different temperatures. But univariant curve GH of the corresponding balance solid phase is different and the crystal water of sodium bromide has disappeared at 373 K. In comparison with the quaternary system Na+,K+//Cl-,SO42--H2O and the quaternary system Na+,K+//Br-,SO42--H2O at 373 K, the two phase diagrams have very similar shapes, each of them having three invariant points, seven univariant curves and five crystallization fields. The crystallization field of the salt NaBr is apparently smaller than that of NaCl. It is also found that halide has the salting-out effect on sulfates. The water content and the density transformation rules are discussed simply. The water content is lower with the higher solution of bromine and the density is higher with the higher solution of bromine.

    Analysis of operation and heat transfer characteristics in pulsating heat pipe based on infrared thermal imaging technology
    LIU Xiangdong, WANG Chao, CHEN Yongping
    2016, 67(4):  1129-1135.  doi:10.11949/j.issn.0438-1157.20151338
    Abstract ( 173 )   PDF (4798KB) ( 376 )  
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    By combination of infrared thermal imaging technique and high-speed visualization method, the surface temperature distribution of condenser in a pulsating heat pipe (PHP) and operating state of working fluid inside the PHP are obtained and the relationship between them and heat transfer performance of the PHP is analyzed. The results indicate that the working fluid sequentially exhibits three quasi-steady operation modes with the increasing heat load viz. small pulsation in single pipe, large pulsation among different pipes and unidirectional circulation. In addition, in the condenser the dominated flow patterns are dispersed bubbles and vapor plugs, and the proportion of the dispersed bubbles decreases with increasing heat load. The difference in strength of heat and fluid flow in the PHP leads to the different characteristics of temperature distribution in the condenser, implying that the infrared thermal image of condenser is an important evidence to the evaluation of working fluid operation and heat transfer performance of the PHP.

    Characteristics of mass and heat transfer in lignite pyrolysis with solid heat carrier
    LI Fangzhou, LI Wenying, FENG Jie
    2016, 67(4):  1136-1144.  doi:10.11949/j.issn.0438-1157.20150598
    Abstract ( 196 )   PDF (1088KB) ( 428 )  
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    A comprehensive numerical model coupled two correlative one-dimensional unsteady heat conduction equations of spherical particle with distributed activation energy model has been developed for heat and mass transfer mechanism in lignite pyrolysis with solid heat carrier. The finite volume method and the genetic algorithm optimization toolbox based on Matlab software were employed to calculate the thermal and dynamic parameters, separately, and the reliability of the predictions was further validated by thermogravimetric data of the Hulunbuir lignite and temperature measuring experiment on a laboratory-scale fixed bed reactor, respectively. It was found that the variations in mass and heat transfer during lignite pyrolysis with solid heat carrier showed a complex coupling characteristic. The time-dependent rules of temperature field in radial direction have been obtained by varying operation conditions, such as coal particle radius, the initial temperature and feed amount of solid heat carrier. Besides, the relationship between the releasing rate of pyrolytic products and temperature field revealed that the change of temperature field with heating time in lignite pyrolysis was the primary cause of different distribution of the pyrolytic products.

    Natural convection heat transfer from horizontal offset elliptic tube based on holographic interferometry
    ZHU Jinrong, DAI Jinmei, CHENG Xiaomin, ZHANG Jinye, CHENG Chunfu
    2016, 67(4):  1145-1149.  doi:10.11949/j.issn.0438-1157.20151327
    Abstract ( 90 )   PDF (2481KB) ( 260 )  
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    Natural convection heat transfer from a horizontal offset elliptic tube is experimentally investigated using holographic interferometry. The effect of the ellipse major axis from horizontal to vertical direction on heat transfer is analyzed. Interferometric fringes of the tube in infinite space at different inclination angles 0°—90° are recorded. The local and average Nusselt numbers are determined according to the reconstruction of the temperature field around the tube. The experimental results indicate that the heat transfer increases with the ellipse major axis inclined from horizontal to vertical direction. The local Nusselt numbers above the tube is the minimum and the maximum is located near the major axis when the direction of the major axis are horizontal and vertical. The results obtained in this investigation show good agreement with the existing experimental and numerical studies, which can contribute to the optimal design of heat exchanger and also provide a test method for engineering applications.

    Effect of electrostatic on bubble hydrodynamics in gas-solids bubbling bed with and without immersed horizontal tubes
    WU Yingya, PENG Li, LAN Xingying, GAO Jinsen
    2016, 67(4):  1150-1158.  doi:10.11949/j.issn.0438-1157.20151394
    Abstract ( 81 )   PDF (4238KB) ( 163 )  
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    The present paper studied the effects of electrostatics on gas-solids hydrodynamics and bubble characteristics of gas-solids bubbling bed with and without immersed horizontal tubes by applying the two-fluid model coupling with the electrostatic model. At first, the two-fluid model without electrostatic field was adopted to simulate the hydrodynamics in the gas-solids bubbling bed with and without immersed horizontal tubes. Further coupled with the electrostatic model, the effects of electrostatics on bubble distribution characteristics in the gas-solids bubbling bed with and without the immersed horizontal tubes were investigated. The results demonstrated that in the electrostatic field conditions, the two-fluid model can be used to predict gas-solid flow conditions, the bubble diameter, and bubble riser velocity for gas-solids bubbling bed with and without immersed horizontal tubes. However, the immersed horizontal tubes in gas-solids bubbling bed caused an intense disturbance of gas-solids, making a concussion in the distribution of the bubble diameter and bubble riser velocity. The electrostatics did not have a large effect on the average solids holdup of the bed, but showed a greater impact on the bubble characteristics. The electrostatics decreased the number of bubbles of the gas-solids bubbling bed without the immersed horizontal tubes and made more number of bubbles be concentrated in the lower region of the gas-solids bubbling bed with the immersed horizontal tubes and more number of large bubbles be located in the upper part of the gas-solids bubbling bed with the immersed horizontal tubes.

    Optimal design for measuring gas holdup in gas-liquid two-phase slug flow using quick closing valve method
    ZHAO An, HAN Yunfeng, ZHANG Hongxin, LIU Weixin, JIN Ningde
    2016, 67(4):  1159-1168.  doi:10.11949/j.issn.0438-1157.20151293
    Abstract ( 108 )   PDF (1380KB) ( 166 )  
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    Quick closing valve (QCV) method is a common means of calibrating gas holdup in gas-liquid two-phase flow test. Unreasonable selections of spacing between valves and trapping times in QCV could bring about large error in gas holdup measurement, particularly since the gas slug and liquid slug in slug flow present flow characteristics with random variability. In this study, an optimal design was proposed for measuring gas holdup using QCV method. The cross-correlation velocity of gas-liquid two-phase slug flow was measured based on the signals between axially upstream and downstream probes. Then, the lengths of gas slug and liquid slug were extracted from the upstream probe signals under different flow conditions. Also, the gas holdup in liquid slugs was calculated by using Maxwell equation. On that basis, the gas holdup series was simulated at different spacing between valves based on the gas slug ratio in pipe. By analyzing the fluctuation of gas holdup series, the floor level of trapping times was indicated under the condition of 95% confidence coefficient and 5% permissible error at different spacing between valves. Finally, an experiment was conducted to assess the trapping times in QCV with the spacing setting at 1.55 m length. The measuring errors of gas holdup using QCV method was statistically analyzed, and it was proved that the design guideline provided a sufficient condition for setting up the spacing between valves.

    Effect of feeding gas on pneumatic conveying of pulverized coal in industrial-scale vertical pipe
    PAN Xiangming, GUO Xiaolei, LU Haifeng, LIU Kai, FU Lin, LI Peng, GONG Xin
    2016, 67(4):  1169-1178.  doi:10.11949/j.issn.0438-1157.20151094
    Abstract ( 72 )   PDF (3217KB) ( 241 )  
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    The dense-phase pneumatic conveying of pulverized coal was investigated in an industrial-scale vertical pipe (50 mm I.D.). Air and CO2 was used as feeding gas or carrying gas, which consequently forms four typical cases, namely Air→Air, Air→CO2, CO2→Air and CO2→CO2. Comparison was conducted between the above cases to analyze the conveying characteristics of pulverized coal experienced different courses. The results showed that the compound modes of feeding gas and carrying gas could affect the fluidized state of pulverized coal in the feeder vessel and result in the differences of stability and flow patterns of conveying process. Electrical capacitance tomography (ECT) was employed to monitor the flow patterns, while the solid concentration signals obtained from ECT were analyzed on the basis of standard deviation (SD) function and power spectral density (PSD) function. It was concluded that the flow pattern of pulverized coal in the case of Air→Air was a stable annular flow, and the stability of the case of Air→CO2 was the worst in which the flow pattern changed from a stable flow to slug flow. Both cases of CO2→Air and CO2→CO2 performed plug flow. In comparison, in the case of CO2→CO2, the bigger plug and higher peak value of PSD were obtained.

    Contrastive analysis of reducing ultrafine particulate matters emission by two modified kaolin
    SUN Wei, LIU Xiaowei, XU Yishu, CHEN Dong, ZHANG Yu, CUI Jiang, XU Minghou
    2016, 67(4):  1179-1185.  doi:10.11949/j.issn.0438-1157.20151364
    Abstract ( 97 )   PDF (2380KB) ( 167 )  
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    Two kinds of typical modification methods, hydrochloric acid potassium manganate modification and sodium hydroxide modification are chosen. These modification methods may change the physical and chemical characteristics of kaolin by using the strong acidity and strong oxidizing of hydrochloric acid potassium manganate, and the strong basicity of sodium hydroxide. And these changes may improve the particulate matter (PM) captured efficiency of kaolin. A typical coal chose in the experiment burns with the raw and modified kaolin in an electrical heated drop-tube furnace, and the particle size distribution of particulate matter is obtained. According to the experimental results, the acid modification can significantly improve the capture efficiency of PM0.2 (particles with the aerodynamic diameter less than 0.2 μm) by kaolin, but the alkali modification inhibit the capture of PM0.2. According to the characterization analysis, for the acid modification kaolin, the Al—OH bond, Al—O—Si bond, Si—O bond and Si—O—Si bond of kaolin are significantly weaken, which can promote the reaction between kaolin and alkali metals, and thus the capture efficiency of PM0.2 is promoted. For the alkali modification kaolin, the Si—O bond and Si—O—Si bond of kaolin are weaken, but the Al—OH bond and Al—O—Si bond of kaolin are strengthened. The strengthened functional groups inhibit the sectional capture processes of alkali metals by kaolin, reducing the capture efficiency of PM0.2.

    Double temperature chilled water unit based on large temperature glide zeotropic mixture
    LIU Jian, ZHANG Xiaosong
    2016, 67(4):  1186-1192.  doi:10.11949/j.issn.0438-1157.20150285
    Abstract ( 72 )   PDF (516KB) ( 136 )  
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    Accordingly to the properties of zeotropic mixture R32/R236fa, a novel double-temperature chilling unit is proposed which can be used in the temperature and humidity independent control air conditioning system (THICS), the unit can produce two different temperature of chilled water (such as low temperature is 7℃ and high temperature is 16℃). An experimental system is established to test the performance of the unit. The results show that at inlet water temperature of the condenser of 32℃ and inlet water temperature of the evaporator of 7℃ and 16℃, the coefficient of performance (COP) of the system can reach 3.92 when the mass component ratio of R32 is 60%. But under mass fractions of R32 of 50%, the combination properties of the system is the best and COP is higher than 3.55 in different operation condition. The results of this study provides the experimental foundation for the application of large temperature glide zeotropic mixture used in the double-temperature chilling water unit.

    Numerical simulation and experimental validation of heat transfer and pressure drop characteristics in metal foam under wet conditions
    WENG Xiaomin, GAO Yang, XU Xudong, ZHUANG Dawei, HU Haitao, DING Guoliang
    2016, 67(4):  1193-1199.  doi:10.11949/j.issn.0438-1157.20151122
    Abstract ( 112 )   PDF (4078KB) ( 261 )  
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    The application of metal foam in the airside of heat exchanger has the potential to improve the heat transfer performance under wet conditions. In order to know the heat, mass transfer and pressure drop characteristics of wet air in metal foam, numerical models for water droplet formation, growth and movement are developed. The mass transfer rate model for droplet formation is based on the heterogeneous nucleation rate and critical nucleation radius of droplet; the mass transfer rate model for droplet growth is based on the species conservation of water vapor on phase interface between the droplet and moist air; the contact angle model of the droplet under combined effects of gravity and air forces is based on the force analysis of droplets on the ligament. The models of mass transfer rate during water droplet formation and growth processes and the model of contact angle are reflected in the continuity, momentum and energy conservation equations as the mass source term and momentum term, which realizes the simulation for the water droplet formation, growth and movement processes in metal foam. The experimental validation of the proposed model shows that, the maximum deviations of the heat transfer rate and pressure drop between the simulation results and experimental data are 11.9% and 17.7%, respectively.

    Effects of fin pitch on heat transfer and flow resistance of twisted-serrated spiral finned tube banks
    WANG Xuegang, YUAN Yichao
    2016, 67(4):  1200-1206.  doi:10.11949/j.issn.0438-1157.20151179
    Abstract ( 100 )   PDF (740KB) ( 183 )  
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    In order to improve the heat transfer enhancement of serrated spiral-finned-tube, twisted-serrated spiral finned tube was fabricated by changing the deflection angle and the twisted direction of serration. Twisted-serrated spiral finned tube banks with the diameters of 38 mm and 51 mm were researched by numerical simulation combined with modeling experiments. The influence of fin pitch on heat transfer and resistance characteristics of twisted-serrated spiral finned tube was obtained. The results showed that Nu at air-side increased firstly and then decreased with the increase of fin pitch from 3.63—8.47 mm. The effects of fin pitch on Nu at air-side was weaker when the fin pitch was larger than 6.35 mm. Eu at air-side decreased with increasing fin pitch. For twisted-serrated spiral finned tube banks with the diameters of 38 mm and 51 mm, comprehensive performance index Nu·f-1/3 was the maximum when the fin pitch is 6.35 mm. Thus, Pf =6.35 mm was the optimum fin pitch within the range of 3.63—8.47 mm.

    Temperature characteristic of electric double layer capacitor under galvanostatic cycling
    ZHANG Xinglei, WANG Wen, HUA Li, HENG Jianpo
    2016, 67(4):  1207-1214.  doi:10.11949/j.issn.0438-1157.20151075
    Abstract ( 60 )   PDF (2030KB) ( 251 )  
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    Temperature characteristic is one of the important properties for an electric double layer capacitor (EDLC), and the reversible and irreversible heat are combined with the charging and discharging for an EDLC. In this study, the numerical simulation of heat transfer, conducted with the finite element technology, and temperature measurement inside and outside EDLC were performed during galvanostatic cycling with different current densities. The heat transfer characteristics and temperature distribution were analyzed by the comparison between the simulated and measured temperatures. And then, the variation and the influencing factors of reversible heat and temperature oscillation during galvanostatic cycling were discussed. Meanwhile, the EDLCs need to be cooled during charging and discharging cycles with great current according to the measured results.

    CFD simulation on effect of interfacial shear force on water vapor condensation in inclined flat tube
    DENG Hui, BAI Yan, LI Xinxin, ZHANG Dongming
    2016, 67(4):  1215-1224.  doi:10.11949/j.issn.0438-1157.20150976
    Abstract ( 80 )   PDF (5187KB) ( 318 )  
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    Considering the interfacial shear force, a mathematical model to the condensation of turbulent vapor flowing downward in an inclined flat tube is proposed and implemented in computational fluid dynamics (CFD). The predicted results from the CFD model are compared with the experimental results from the literature for the vapor condensation in a prototype tube (2600 mm length, 3 mm width and 50 mm altitude in 60° inclination to vertical). It is found that the condensate rate and mean condensation heat transfer coefficient (HTC) from CFD simulation agree very well with the experimental quantities. Using CFD model to calculate the interfacial shear stress by varying vapour velocity, the results demonstrate that the value of shear force depends on the vapor velocity at the tube inlet, and shear force decreases continuously with the vapor flow and condensation. Simulating the interfacial shear effect on the condensation, it shows that the interfacial shear increases the local condensation HTC, and meanwhile, reduces the local condensate rate. The simulation results also shows that the interfacial shear weakens the gravitational effect on the film accumulation and obviously decreases film thickness from 0 to 0.8 m in the tube axial length. However, from 1.0 m to the tube outlet, the gravitational force dominates over the shear force, and thus the shear effects can be completely neglected. It is also found that the condensate film is speeded up particularly from 0 to 0.2 m in axial length thanking for the interfacial shear.

    Numerical study on plume characteristics of liquefied natural gas spills
    ZHANG Xiaobin, LI Jingfeng, QIU Limin
    2016, 67(4):  1225-1232.  doi:10.11949/j.issn.0438-1157.20150740
    Abstract ( 107 )   PDF (614KB) ( 342 )  
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    When a large number of LNG suddenly leaks and evaporates, it will form a low temperature cloud in the wind downstream, which may cause frostbite, burn and oxygen deficit hazard to the ground personnel. Based on the computational fluid dynamics (CFD) method, the two-phase multicomponent flow mathematical framework together with the turbulence closure are built to model the cryogenic flow. The phase-change mass transfer of water vapor in the air due to the temperature depression is considered. Because of the existence of non-liquefied gases such as oxygen, the Hertz-Knudsen equation for calculating the mass transfer rate of water vapor is modified. Detailed methods for setting the boundary conditions of the computational domain are presented and the influence of Coriolis force caused by the earth rotation is evaluated. The Burro experimental series of LNG released by LLNL are simulated and the results are used to evaluate the numerical models. It is found that the results using models with the phase change of water vapor are closer to the experimental results than that without the phase change. The studies are of directive significance for the safety environment assessment and design of LNG received terminal.

    Interaction characteristics between longitudinal vortices with counter-rotating directions in heat exchanger channel
    SONG Kewei, LIU Song, WANG Liangbi
    2016, 67(4):  1233-1243.  doi:10.11949/j.issn.0438-1157.20150618
    Abstract ( 66 )   PDF (1592KB) ( 200 )  
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    Longitudinal vortices can enhance heat transfer with small pressure loss penalty and has been widely applied in heat transfer enhancement of tube bank fin heat exchangers. Setting winglet vortex generator (VG) that can generate longitudinal vortices on the fin surface is a promising technique to enhance the airside heat transfer. In order to obtain better heat transfer performance, lots of VGs are punched out of the fin surface, so several longitudinal vortices appear in the flow channel. The interaction of vortices affects the intensity of longitudinal vortices and their effect on heat transfer enhancement. In this paper, the interaction of counter rotating longitudinal vortices generated by winglet VGs is quantitatively analyzed under different transversal distances between VGs. The effects of interaction of vortices on the intensity of vortices, flow field structure and heat transfer are discussed in detail by using the longitudinal vortex intensity parameter Se. The results show that the interaction of counter rotating longitudinal vortices increases with the decrease of transversal distance between VGs. When the distance between VGs is zero, the interaction between counter rotating vortices is the most serious, while the values of ΔSe, ΔNu and Δf get the minimum values. The maximum decreasing percentage of ΔSe, ΔNu and Δf are 45%, 50% and 38%, respectively. The interaction between counter rotating vortices does not necessarily decrease the heat transfer of longitudinal vortices. The heat transfer performance depends on not only the intensity of vortices but also their structure. The common flow region formed between counter rotating longitudinal vortices is beneficial for heat transfer enhancement. Due to the interactions of counter rotating longitudinal vortices and their effect on heat transfer enhancement, an optimum arrangement of VGs exists for better heat transfer performance. The best heat transfer performance can be obtained when the transversal distance between the VGs is twice the projected length of the base of VGs.

    Heat transfer characteristics of supercritical CO2 at low mass flux in tube
    BAI Wanjin, XU Xiaoxiao, WU Yangyang
    2016, 67(4):  1244-1250.  doi:10.11949/j.issn.0438-1157.20151178
    Abstract ( 132 )   PDF (736KB) ( 555 )  
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    An experimental investigation on the heat transfer characteristics of CO2 during gas cooling process in a horizontal tube is conducted. The experimental data is obtained over a mass flux range of 79.6-358.1 kg·m-2·s-1, inlet pressure range of 7.5-9.0 MPa and mean bulk temperature from 25.0 to 50.0℃. The effects of mass flux, pressure and bulk temperature on the heat transfer efficiency are investigated. The combined parameter of Gr/Re2 is used to quantify the buoyancy force effect on the heat transfer. The experimental results show that the heat transfer coefficient of the CO2 increases with increasing mass flux. The peak value of the heat transfer coefficient shifts to a higher temperature region as the pressure increases. It appears that the peak value of the heat transfer coefficient occurs at bulk temperature slightly lower than the pesudo-critical temperature at low mass flux. The lower mass flux is reached, the greater influence of buoyancy force effect. The experimental heat transfer coefficients are compared with some existing correlations. The predicted results present obvious deviation compared to the experimental results at low mass flux. A new heat transfer correlation for the tube is proposed based on the experimental data. The maximum error between the predicted results of the new correlation and the experimental data is 20%.

    Fractal characteristics of temperature oscillation in pulsating heat pipe under medium-low load
    FANG Haizhou, YANG Honghai, WANG Jun, LI Jianhua, ZOU Jing
    2016, 67(4):  1251-1257.  doi:10.11949/j.issn.0438-1157.20150957
    Abstract ( 99 )   PDF (784KB) ( 229 )  
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    Various method, including analyses of power spectrum, wavelet decomposition, pseudo-phase-plane trajectories and correlation dimension, were used to analyze the non-linear dynamics characteristics of temperature oscillation signal of pulsating heat pipes (PHPs). A continuous line, self-similarity were identified under different sampling frequency, and the chaotic behavior of temperature oscillation signal was shown by power spectrum diagram. Wavelet decomposition indicated fractal characteristics of temperature oscillation. Four types of attractors were identified under different power inputs, which showed different space fractal structure. It was found that the temperature fluctuations belong to fractal chaotic behavior. All of the calculated fractal dimension showed that the system existed 3—6 fractal dimension. With the increase of embedding dimension, the fractal speed relations as R134a was greater than acetone, and acetone was higher than deionized water. For most runs, the large correlation dimensions were corresponded to better thermal performance.

    Characteristics of drag reduction in different cross sections of hydrophobic micro pin fins
    JIANG Guilin, GUAN Ning, ZHANG Chengwu, LIU Zhigang
    2016, 67(4):  1258-1268.  doi:10.11949/j.issn.0438-1157.20150890
    Abstract ( 89 )   PDF (7801KB) ( 218 )  
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    The hydrophobic coatings with different properties are coated on the surfaces of micro pin fins with different cross sections of circular, diamond and elliptical to obtain hydrophobic micro pin fins with contact angles of 99.5°, 119.5° and 151.5°, respectively. The reduction coefficient of the pressure drop and the friction resistance are measured experimentally when water flows through the hydrophobic micro pin fins at different flow rates. Experimental results show that the change rate of pressure drop in ellipse and diamond micro pin fins increases gradually, however the change rate of pressure drop in circular micro pin fins increases at first and then decreases when the contact angle changes from 83° (the red copper smooth surface) to 151.5°. With the increase of the flow rate, the change rate of pressure drop in ellipse micro pin fins gradually decreases, while it decreases at first and then almost keeps constant in diamond and circular micro pin fins. The investigation also illustrates that the resistance reduction rates in all of test sections become large with the increase of the contact angle at the same Re. Under the same contact angle conditions, the resistance reduction rate gradually decreases in elliptical micro pin fins with the increase of Re, while it decreases at first and then keeps almost constant in diamond shaped and circular test sections. The minimal resistance reduction rates in diamond shaped and circular micro pin fins are 50.81% and 58.68% at contact angle of 151.5°, respectively.

    Numerical simulation and mechanism of jet atomization in water-sparged aerocyclone
    QIU Facheng, XU Fei, QUAN Xuejun, LUO Dan, DAI Mingxing, WU Jingping
    2016, 67(4):  1269-1276.  doi:10.11949/j.issn.0438-1157.20151032
    Abstract ( 141 )   PDF (6396KB) ( 291 )  
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    Water-sparged aerocyclone (WSA) is a new type of high efficient gas-liquid mass transfer reaction equipment. The gas phase pressure drop characteristics, liquid phase reflux ratio and jet atomization process in the WSA were better simulated using the Reynolds stress model (RSM) and the multiphase flow model of volume of fluid (VOF). The mechanism of jet atomization process in the WSA was also discussed in detail. Both simulation and experiment results illustrated that the gas phase pressure drop of WSA will go through a low pressure drop zone, a pressure drop jump zone, a pressure drop transitional zone and a high pressure drop zone with the increase of gas inlet velocity. The determination method of a turning point between two adjacent pressure drop areas was given. The water jet presents steady jet, deformation and bag-like breakup, bag-like breakup and shear atomization, shear atomization and liquid drop centrifugation, respectively, in the above-mentioned pressure drop areas. The water jet in the WSA was fully atomized and the mass transfer interface between gas and liquid phases was maximized when the gas phase inlet velocity reached the turning point between the pressure drop transitional area and the high pressure drop area. The results could be used as a theoretic basis for establishing a adjusting method for jet atomization and flow field in the WSA.

    Overall heat transfer coefficient of plate-fin heat exchanger during a mixed refrigerant cryogenic process in low quality
    CAO Le, LIU Jinping, XU Xiongwen, LI Rixin
    2016, 67(4):  1277-1286.  doi:10.11949/j.issn.0438-1157.20151177
    Abstract ( 146 )   PDF (851KB) ( 251 )  
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    Plate-fin heat exchangers (PFHEs) are mostly employed in medium- and small-sized LNG plants. However, works about the heat transfer characteristic optimization of mixed refrigerant in PFHE under low quality have been barely carried out nowadays. Thus, a Linde-Hampson cycle using single stage compressors and recuperative heat exchanger was established and mixed refrigerant (N2-CH4-C2H4-C3H8-iC4H10) was used to obtain the refrigeration temperature of -160℃. Meanwhile, the overall heat transfer coefficient and the correlational influence factor were mainly analysed. The experimental results showed that the overall heat transfer coefficient of the PFHE was about 2.6—22.7 W·m-2·K-1 while the refrigeration temperature and the circulated composition had week influence on the overall heat transfer coefficient. Meanwhile, the existing correlations cannot accurately predict the heat transfer coefficient of the mixed refrigerant under low quality and low flow velocity. However, the correlation of Cavallini and modified Granryd can used to predict the HTC of mixed refrigerant under low quality and low flow velocity after modification in this work. Additionally, some suggestion have been proposed in the design and optimization of PFHEs considering the refrigerate flowrate and pressure drop.

    Effect of Fe2O3 on surface properties and activities of V2O5-WO3/TiO2 catalysts
    LIU Jianhua, YANG Xiaobo, ZHANG Chen, WU Fan, LI Zhong, XIA Qibin
    2016, 67(4):  1287-1293.  doi:10.11949/j.issn.0438-1157.20151284
    Abstract ( 116 )   PDF (613KB) ( 524 )  
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    Effect of Fe on the denitration activity and sulfur dioxide oxidation rate of vanadium-titanium based SCR catalysts is worthy to be investigated. In this work, Fe2O3-V2O5-WO3/TiO2 catalysts with various mass ratios of Fe/V were prepared by incipient wetness impregnation method and characterized. The results showed that the denitration activity and sulfur dioxide oxidation rate of catalysts initially increased then decreased with the loading of Fe2O3. The highest denitration activity of 91.78% and sulfur dioxide oxidation ratio of 1.01% were achieved with a Fe/V mass ratio of 3.0. XPS and H2-TPR measurements showed that with the loading of Fe2O3, the content of active vanadium and V4+/V5+ ratio on the surface of catalysts decreased, while the relative-content of surface adsorption oxygen(Oα) increased hence the oxidation ability of catalysts enhanced. Moreover, the NO-TPD results showed that the capability of NO adsorption on catalyst surface enhanced with the loading of Fe2O3.