空调器性能系数的讨论

从空调器的工作原理和制冷剂的热循环讨论了空调器的性能系数Ke 大于 1,即消耗 1焦耳的电能可以得到大于 1焦耳的制冷 (热 )量     

复合制冷循环间冷系统制冷剂/工质的选择论证

该文旨在从目前80余种制冷剂(包括替代工质)中筛选出能满足复合制冷循环间冷系统(以下简称复间冷)要求的中间传热介质(制冷剂/工质)。筛选步骤如下:1)按制冷剂的臭氧损耗潜势和全球变暖潜势挑选出满足环保要求的"环保型制冷剂";2)根据环保型制冷剂的物性对复间冷要求的满足程度,挑出合适度比较高的若干种;3)从前两轮筛选出的制冷剂/工质挑出做功能力最大者。最终氨成为3轮筛选唯一胜出的自然物质。考虑到氨的气味对人的呼吸道有刺激性,条件具备时可燃可爆,故再次仔细分析了其安全性,指出其燃爆可防、易防,拟定了相应防范措施,并列举了应用实例。全文结论为:氨物性对复间冷的合适度最高,环境最友好,安全可靠,性价比高。作为复间冷的制冷剂/工质,氨虽非最佳,但目前尚无更佳的替代物。     

Condensing heat transfer for R114/R12 mixtures on horizontal finned tubes

Two titanium tubes with external fins were tested in the horizontal orientation to determine heat transfer performance with R114, R12, and selected non-azeotropic mixtures of the two condensing on the outside surface. For the single-component situation, data were in excellent agreement with predictions from a modified Katz-Keller method, and little performance distinction was found between the tubes or between the pure refrigerants. All mixtures depressed performance below single-component levels, with even low second-component concentrations causing substantial degradation (up to 55% performance reduction for 5% R12). Gas chromatograph composition analyses of vapour from the condenser shell showed elevated concentrations of the more volatile component (R12), evidence that an added transport resistance contributed to the observed mixture performance reductions. If previously suggested benefits of mixtures in heat pump applications are to be realized, the associated condensers should be in a configuration so as to mitigate these performance penalties.     

采用非共混制冷剂对冷水机组换热器的影响

针对R22近期替代物多为非共沸混合制冷剂的现实和替代工作开展的需要,分析了采用非共沸混合制冷剂代替单组分工质后凝结和沸腾换热相界面传质阻力对蒸汽压缩式冷水机组蒸发器、冷凝器传热性能的不利影响,给出了由此引起的传热系数降低程度的估算,基于分析结果,对采用非共沸混合制冷剂的冷水机组换热器选型及设计进行了讨论。     

微通道换热器空调系统性能试验分析

本文通过对两套采用微通道换热器的KFR-72LW空调器样机（1号机：室内外换热器均采用微通道换热器;2号机：室外机为微通道换热器,室内机为管翅式换热器）,分别进行性能测试,对比分析采用微通道换热器与管翅式换热器的空调器性能差异。试验结果分析显示：微通道换热器空调器具有高效（强制冷性能）、减排（减少制冷剂充注量）、低成本（换热器小型化）等优点;但制热工况下,因室外机采用微通道换热器,换热面积大幅度减小,蒸发压力过低,导致制热效果不良、系统频繁除霜等问题,有待于进一步研究解决。     

高温工质冷凝换热试验台设计

系统介绍了高温工质冷凝换热试验台的设计方法。试验台由高温工质自然循环子系统、冷却水机械循环子系统和计算机监测控制子系统构成,试验段进出口温差及冷凝管进出口温度的测试、蒸汽锅炉充注量及液位控制、高温水箱自然作用水头的设计、冷却水流量计量水箱的设计等是试验台设计中值得重视的问题。根据误差分析结果,该试验台冷凝传热系数的相对误差为±7.19%,管内、管外的冷凝换热系数的相对误差分别为±4.95%和±8.73%。     

Research methods and performance analysis for the moderately high temperature refrigerant

In China, directly dropping high temperature refrigerant into conventional compressor is considered as a dominant technical route for development of moderately high temperature heat pump. Based on this route, selection criteria for high temperature refrigerant were presented with consideration of several influencing factors. Moreover, a set of research methods were built including theoretical calculations and experimental tests. Four high temperature refrigerants from HTR01 to HTR04 were compared and analyzed. In results, firstly, HTR03 and HTR04 belonging to non-ozone depleting refrigerants could bring outstanding environmental benefits; secondly, the condenser outlet water efficiently generated by heat pump using high temperature refrigerants could cover 60°C–90°C;; finally, the feasibility of the technical route and the research methods were proved. Supported by Program for New Century Excellent Talents in University (Grand No. NCET-04-0078)     

乙烯装置采用混合冷冻剂循环技术综述

概述了混合冷冻剂循环技术在乙奖装置的应用，阐述了混合冷冻剂的组成，开环及闭环混合冷冻剂的循环流程。     

Experimental study on forced convective boiling heat transfer of pure refrigerants and refrigerant mixtures in a horizontal tube

Convective boiling heat transfer coefficients of pure refrigerants (R22, R32, R134A, R290, and R600a) and refrigerant mixtures (R32/R134a, R290/R600a, and R32/R125) are measured experimentally and compared with Gungor and Winterton correlation. The test section is made of a seamless stainless steel tube with an inner diameter of 7.7 mm and is uniformly heated by applying electric current directly to the tube. The exit temperature of the test section was kept at 12°C ± 0.5°C for all refrigerants in this study. Heat fluxes are varied from 10 to 30 kW m⁻² and mass fluxes are set to the discrete values in the range of 424–742 kg m⁻² s⁻¹ for R22, R32, R134a, R32/R134a, and R32/R125; 265–583 kg m⁻² s⁻¹ for R290, R600a, and R290/R600a. Heat transfer coefficients depend strongly on heat flux at a low quality region and become independent as quality increases. The Gungor and Winterton correlation for pure substances and the Thome-Shakil modification of this correlation for refrigerant mixtures overpredicts the heat transfer coefficients measured in this study.     

A new three-parameter cubic equation of state for refrigeration engineering calculations

A new three-parameter cubic equation of state is proposed in which the repulsion pressure term of the semiempirical van der Waals equation has been modified based on the hard-sphere potential and a functional form similar to Redlich-Kwong attraction term is adopted for the attraction term. All three parameters are treated as functions of temperature. For the purpose of examining the applicability of the new equation, it was applied to describe the thermodynamic properties of difluoromethane (R-32) and pentafluoroethane (R-125). It has been found that the essential thermodynamic properties are represented by the new equation as accurately as a conventional far-complicated modified Benedict-Webb-Rubin equation in the working range of refrigeration equipment. The new cubic equation was also compared with the Peng-Robinson equation and the Carnahan-Starling-De Santis equation.