【作者】 孟冲；

【导师】 吴剑峰； 公茂琼；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 制冷及低温工程， 2007， 硕士

【摘要】 -80℃的低温环境在生物材料的活性储存、食品的低温保鲜、医学工程、低温环境模拟等领域都有着广泛的应用和良好的应用前景。单级蒸汽压缩制冷循环由于受到压比及冷凝、蒸发压力等条件的制约,而无法有效实现-40℃以下的制冷温度,工业界较为普遍采用双级复叠式系统实现这个温区的制冷需求。传统的应用于-80℃温区的复叠制冷系统低温级的制冷工质主要有R13、R503和R23,前两者具有很高的ODP值和GWP值,逐渐将停止使用,后者GWP值、压比及排气温度都很高。现在常用的制冷工质是R508系列,仍然具有较高的GWP系数,且润滑油溶解性能较差,将会导致系统可靠性和效率的降低。因此,开发一类高效、环保的替代工质显得异常紧迫和至关重要。对于替代工质而言,其整机性能研究的重要性是不言而喻的。本文针对复叠温区的新型共沸工质开展了一系列的整机性能研究,主要工作如下:1.新型共沸工质的循环性能计算利用美国国家标准技术研究所NIST(National Institute of Science and Technology)开发的制冷剂热物性计算软件REFPROP7.1计算了新型共沸工质的循环特性,并与R508B进行了比较,计算结果显示:R170+R116系和R170+R116+R23系具有相对较好的制冷性能。2.双级复叠式制冷循环实验系统的设计与搭建通过参考专利CN2364403Y、CN2694182Y、CN1485589A和国标GB/T5773-2004,建立了一套两级复叠制冷实验装置,来实验测量上述制冷剂的循环性能。在实验测量方面,采用高精度的温度、压力测量及采集系统,保证能得到精确的实验数据。本实验台适用于复叠温区各种工质。3.传统复叠温区制冷工质的整机性能实验研究通过实验测试,比较了不同冷凝、蒸发温度下低温级常用制冷工质R13、R23、R503、R508A和R508B的COP、压比及制冷量等循环性能,又结合各制冷工质的环境性能、热工性能,分析了现有常用复叠系统低温级制冷工质各自的优缺点,为新工质的开发及进一步制冷性能对比实验工作提供了有益的帮助。4.新型共沸混合物的整机性能实验研究在不同冷凝温度和蒸发温度下,分别测量了新共沸工质R170+R116系、R170+R23系和R170+R116+R23系的整机性能。从跟传统制冷工质中性能较好的制冷工质R508B比较来看,新开发的这三种共沸混合物不仅ODP系数为零,GWP系数较小,而且整机制冷性能较为优越,具有替代现有复叠温区常用制冷工质的巨大潜力。更多还原

【Abstract】 There are many wide applications in the temperature range of -80℃, such as biology, iatrology, biophysics, life science, and so on. Generally, the lowest effective refrigeration temperature for a traditional vapor-compression cycle is about -40℃, limited by the pressure ratio, condensing temperature and evaporating temperature. In order to achieve a lower temperature of -80℃, a two-stage cascade refrigeration cycle is necessary.In the low temperature stage of a two-stage cascade system, R13, R23 and R503 are the traditionally used refrigerants. However, because of their high ozone depletion potential (ODP) values and global warming potential (GWP), the usage of those kinds of refrigerant are limited and finally forbidden. So the popularly used refrigerant in the low temperature stage is R508B now, which is an azeotropic mixture of R23 and R116, still with a large GWP value because of its HFC and FC components. Furthermore, the refrigerant of R508 is less soluble in compressor lubricant, which would lead to a reduction of system reliability. So, it is necessary and important to find some effective and environment-friendly alternative refrigerants used in the low temperature stage of the two-stage cascade refrigeration cycle. It is self-evident that the investigation on refrigerating performances is essential for alternative refrigerants. Capacity measurements for the new azeoreopic refrigerants have been conducted by the author, which are presented as follow:1.Refrigeration performance calculation for new mixturesWith a software of REFPROP7.1, the thermodynamic performances of some new proposed refrigerant mixtures and R508B were compared by calculation of such important parameters as COP, pressure ratio, discharge temperature and volumetric refrigerating capacity. It is clear that, the new azeotropic mixtures of R170+R116 and R170+R116+R23 have better performances.2.Design and establishment of an experimental apparatus for performance testOn the basis of patents of CN2364403Y, CN2694182Y, CN1485589A and GB/T5773-2004, an experimental apparatus was designed and fabricated. High precision thermometers, pressure transmitters were used to obtain the precise data. Furthermore, the experiment apparatus is designed to adapt to different kinds of refrigerants for cascade refrigeration systems.3.Research on traditional refrigerants for cascade refrigeration systemsThermodynamic performances of COP, pressure ratio and refrigerating capacity for five traditional refrigerants of R13, R23, R503, R508A and R508B were messured at different condensing temperatures and evaporating temperatures. Based on the environmental features and thermodynamic performances, disadvantages of these traditionally used refrigerants in the low temperature stage of a two-stage cascade refrigeration cycle were analyzed. The results obtained in this study are useful for searching some effective and environment-friendly alternative refrigerants and further experimental capacity comparison.4. Research on new refrigerants for cascade refrigeration systemsSeries binary and ternary azeotropic mixtures of R170, R116 and R23 have zero ODP and less GWP values were proposed and their performances were measured and compared with R508B. All of them show good potential for use in cascade refrigeration system for -80℃applications.更多还原