最新刊期
      卷 28 ， 期 6 ， 2007

      • Heat Transfer of Channel Type Wheel Heat Exchanger under Frosting Condition

        Vol. 28, Issue 6, Pages: 1-6(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.001
        摘要：Formation of frost on the surface of exhaust outlets causes the performance degradation of channel type wheel fresh air ventilators when operating under low ambient temperature in winter. In this study, a detailed model for the channel type wheel heat exchangers under frosting condition was established, including a frosting sub-model and a channel type wheel heat exchanger sub- model. Analysis on the heat transfer characteristics of a frosted channel type wheel heat exchanger was performed under different ambient conditions. In addition, the intervals of defrosting were obtained under different operating conditions. The computing results are in agreement with the experimental data.  
        关键词：engineering thermophysics;Channels wheel heat exchanger;frosting;Heat transferring   
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      • Vol. 28, Issue 6, Pages: 7-12(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.002
        摘要：The existing equation for calculating water vapor supersaturation degree at frost surfaces was improved. An analytical model to simulate the performance of evaporators for indirect cooling refrigerators under frosting conditions was established. The mass of frost accumulating on the evaporator surface, the airside pressure drop, the frost density and thickness were calculated. In addition, the computing results were compared with the experimental data. It appears that the present model has good ability to simulate the performance of evaporators for indirect cooling refrigerators.  
        关键词：engineering thermophysics;Indirect cooling refrigerator;evaporator;frost;simulation   
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      • Analysis on Thermal Conductivity Enhancement for PCM Embedded in Metal Foam

        Vol. 28, Issue 6, Pages: 13-17(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.003
        摘要：Analysis for estimating effective thermal conductivity of the phase change thermal energy storage filled up with metal foams was performed. Based on the analysis of metal foam structure, a model consisting of a two-dimensional array of hexagonal cells was established in which the fibers form the sides of the hexagons and the unit cell was assumed as nine heat transfer layers. The functional relations between the effective thermal conductivity and the porosity were derived with the thermal resistance analysis. In addition, numerical data of the effective thermal conductivity with paraffin embedded in aluminum foam and copper foam were compared with those with paraffin embedded in aluminum fin and copper fin. The results indicate that the thermal conductivity and efficiency of the phase change thermal energy storage by filling metal foams are obviously higher than those by filling metal fins.  
        关键词：engineering thermophysics;Energy storage technique;metal foam;effective thermal conductivity;Porosity;Phasechange energy storage   
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      • Vol. 28, Issue 6, Pages: 18-22(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.004
        关键词：Engineering therrnophysics;Chip cooling technique;Experiment;Vapor chamber;Thermal physical performance   
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      • Vol. 28, Issue 6, Pages: 23-28(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.005
          
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      • Effects of 3A Molecular Sieve on THF Hydrate Decomposition

        Vol. 28, Issue 6, Pages: 29-34(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.006
          
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      • Vol. 28, Issue 6, Pages: 35-40(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.007
        摘要：Air source heat pump is widely used, and a capacity modulation with concentration of mixture refrigerant is a new type modulation of environment protection and energy conservation. In this paper, the state of the art of existing variable concentration devices with mixture refrigerant is presented and their types are described according to their locations in the system. The analysis results indicate that the variable concentration device should be set at the outlet of liquid refrigerant in order to change concentration of mixture refrigerant in air source heat pump. Moreover, a rectification section is more effective to change concentration than a gasliquid separator or liquid reservoir, and the middle throttling apparatus should be an electronic regulation device other than a capillary tube. The improvement and application of variable concentration devices in air source heat pumps are also discussed.  
          
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      • Manufacturing Technology and Performance of Micro Thermoelectric Coolers

        Vol. 28, Issue 6, Pages: 41-46(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.008
        关键词：pyrology;Micro thermoelectric cooler;review;Leg length;Manufacturing approach   
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      • Vol. 28, Issue 6, (2007) DOI: 10.3969/j.issn.0253-4339.2007.06.009
        关键词：engineering thermophysics;enhanced heat transfer;experiment study;Twisted tube;condenser;Fouling   
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      • Vol. 28, Issue 6, Pages: 51-56(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.010
        摘要：LiBr-water absorption chillers are commonly adopted in multifunction energy systems. The empirical part-load performance model for chillers presented by DOE-2 is one of the analytical methods to solve chiller performances. In this study, the applicability of the DOE-2 model for absorption chillers was analyzed. A modified DOE-2 model for double effect steam-driven absorption chillers, as an example, was developed and its reasonability and validity were tested by the product data and the general theoretical model. Application case study confirms the ability of the modified DOE-2 model to fast predict the part-load performances of absorption chillers.  
        关键词：engineering thermophysics;LiBr-water absorption chiller;Analytical method;Part-load performance   
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      • Performance Experiment of R290/CO2 Cascade Refrigeration System

        Vol. 28, Issue 6, Pages: 57-60(2007) DOI: 10.3969/j.issn.0253-4339.2007.06.011
        摘要：Performance experiments of R290/CO2 cascade refrigeration system were conducted. The performance of a cascade refrigeration system having a high temperature cycle using R290 as refrigerant and a CO2 based low temperature cycle was compared with that of a cascade refrigeration system having a high temperature cycle using R22 as refrigerant and a CO2 based low temperature cycle. The results show that the optimum mass flow rate ratio and the maximum COP of the R290/CO2 cascade refrigeration system increase with the increase of evaporation temperature and with the decrease of condensation temperature. Moreover, the power consumption of the R290 compressor is slightly higher than that of the R22 compressor and the COPh of the R290 cycle is higher than that of the R22 cycle at the higher compressor inlet temperatures.  
          
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