Irreversible refrigerators with isothermal heat exchanges: Réfrigérateurs irréversibles avecéchanges thermiques isotherms

A maximum for the coefficient of performance (COP_f) is verified for a temperature difference between reservoirs and the hot isotherm of a closed irreversible cyclical refrigerator working at steady-state conditions. A maximum also exists when the COP_f is considered as a function only of a parameter depending on the thermal characteristics of the heat exchangers. The influence of the parameter and entropy generation on the COP_f maxima is described.     

废旧冰箱保温材料热解气体的红外光谱研究

采用热重-红外光谱联用技术分析了废旧冰箱保温材料在加热速率20℃／min条件下、40-850℃范围内的热失重行为、气体产物组成和释放规律。结果表明：物料热解气体释放强度变化与热失重变化趋势基本一致;热解产物含有C02、氟氯烃、CFC．11、H20、醇类、烃类、CO、羰基化合物、胺类化合物及芳香族化合物等物质。其中CO2在260—480℃的主热解阶段大量释放;发泡剂CFC．11集中在135—270℃析出：CH4主要在350—700℃的温度区间析出;CO在520℃附近形成最大吸收峰。热解气体中还检测到少量NH3和HCN,是原料组成聚氨酯结构中的氮元素热解所致。     

低温技术在太空监测领域的应用

随着低温技术的发展,制冷机的各方面工作性能显著改进,低温技术在航天领域得到了广泛应用。介绍了低温技术在国外太空监测卫星中的应用情况,分析其发展趋势。对太空监测所需要不同温度区间的制冷方法进行了总结,最后以国外执行监测任务卫星上的制冷系统为例说明制冷系统设计过程。     

A review on recent developments in new refrigerant mixtures for vapour compression‐based refrigeration,air‐conditioning and heat pump units

In the present paper, an attempt has been made to review the performance of new refrigerant mixtures employed in vapour compression‐based refrigeration, air‐conditioning and heat pump units. The studies reported with refrigerant mixtures are categorized into six groups as follows: (i) hydrocarbon (HC), (ii) hydroflurocarbons (HFC), (iii) HFC/HC, (iv) hydrochloroflurocarbons (HCFC), (v) carbon dioxide (R744) and (vi) ammonia (R717). This paper explores the studies reported with new refrigerant mixtures in domestic refrigerators, commercial refrigeration systems, air conditioners, heat pumps, chillers and in automobile air conditioners. In addition, the technical difficulties faced with new refrigerant mixtures, further research needs in this field and future refrigerant options for new upcoming systems have been discussed in detail. This paper concludes that HC based refrigerant mixtures are identified as a long‐term alternative to phase out the existing halogenated refrigerants in the vapour compression‐based systems. Copyright © 2010 John Wiley & Sons, Ltd.     

基于微功率无线通信技术的电冰箱能效试验系统的设计（上）

传统的电冰箱能效试验采用的热电偶连接线必须跨越冰箱门才能连接到温度记录仪上,这样必定在冰箱门处产生细小的缝隙,从而影响了间室的密封性,使检测的结果出现误差。该文介绍了一种利用微功率无线通信技术开发的新型检测系统,避免了此类误差的产生,并阐述了该系统的工作原理和软硬件结构。实际应用证明,该系统各方面性能良好,测量数据准确...     

能量选择性电子热机和制冷机的性能特征分析

 针对不同热电子库组成的电子热机和制冷机系统,本文运用费米—狄拉克统计分布计算了在球坐标下两不同热电子库的净电子流密度随能量的分布函数,进而得到相应的热流.接着,计算了电子热机和制冷机各性能参数,数值模拟出该机的优化性能特征曲线.从而得到提高电子机工作性能的方法.     

Experimental investigation of control updating period monitoring in industrial PLC-based fast MPC: Application to the constrained control of a cryogenic refrigerator

In this paper, a complete industrial validation of a recently published scheme for on-line adaptation of the control updating period in Model Predictive Control is proposed. The industrial process that serves in the validation is a cryogenic refrigerator that is used to cool the supra-conductors involved in particle accelerators or experimental nuclear reactors. Two recently predicted features are validated: the first states that it is sometimes better to use less efficient (per iteration) optimizer if the lack of efficiency is over-compensated by an increase in the updating control frequency. The second is that for a given solver, it is worth monitoring the control updating period based on the on-line measured behavior of the cost function.     

A method for estimating the composition of the mixture to be charged to get the desired composition in circulation in a single stage JT refrigerator operating with mixtures

It has been shown earlier in literature that the composition of the mixture in circulation at steady state is different from that charged into the system in Joule-Thomson refrigerators operating with mixtures. There are no methods in literature that help us charge a particular composition into the system in order to get the desired composition in circulation at steady state. Experiments were performed with 30 different charge compositions, two different heat exchangers, and two different heat loads to understand the relationship between the composition in circulation and that charged. Based on these experiments, a method is proposed for estimating the charge composition required to get the desired composition in circulation.     

Factors impacting microbial load of food refrigeration equipment

Our aim was to determine factors that have an impact on the bacterial load of inner surfaces of food refrigeration equipment to develop recommendations that should be made to consumers. We investigated 23 domestic refrigerators (DRs) and, for comparison, six serve-over counters (SOCs). Several zones were studied for aerobic mesophilic counts (AMC) presumptive Bacillus cereus and coagulase-positive staphylococci. In addition, for each DR sample, we collected data on the condition of the sampled surface and refrigeration practices. In DRs, there was no correlation between AMC and temperature, relative humidity, pH or cleaning frequency. AMC counts in SOCs, which are cleaned and disinfected weekly, were similar to the figures from the less frequently cleaned DRs, but B. cereus and coagulase-positive Staphylococus were less frequently found in SOCs. In DRs, the highest AMC counts were reached when both condensation and food traces were visible, i.e. when growth conditions were met, resulting in a mean of 10⁴ CFU/cm² against of mean of 32 CFU/cm² on clean surfaces and dry surfaces with food traces. Consequently, two recommendations for consumers are (1) to avoid condensation and (2) to clean up food spills as soon as possible.     

Comparative assessment of environment-friendly alternatives to R134a in domestic refrigerators

In the present work, the possibility of using R152a and hydrocarbon refrigerants (such as R290, R1270, R600a, and R600) as alternatives to R134a in domestic refrigerators has been assessed theoretically. The refrigerants are assessed over wider range condensing and evaporator temperatures. The assessment was done with standard parameters such as pressure ratio, volumetric cooling capacity (VCC), coefficient of performance (COP), compressor input power, compressor discharge temperature, and total equivalent warming impact (TEWI). The results obtained showed that pure hydrocarbon refrigerants are not suitable to be used as alternatives to R134a due to its mismatch in VCC. R152a has approximately the same VCC with about 9% higher COP and lower values of operating pressure and compressor input power. The discharge temperature of R152a was higher than that of R134a by about 14–26 K. TEWI of R152a was about 7% lower than that of R134a. The reported results proved that R152a is an energy-efficient and environment-friendly alternative to phase out R134a in domestic refrigerators.