【作者】 牛宝联；

【导师】 张于峰；

【作者基本信息】 天津大学 ， 热能工程， 2007， 博士

【摘要】 以R13为主的工业用制冷剂对环境的破坏作用很大,在发达国家已经被停止使用,在发展中国家也将于2010年停止使用。其目前常用的替代制冷剂R23、R508b在替代中存在着一些问题,而且价格昂贵。寻找环境性能友好,热力性能优良,价格低廉的制冷剂迫在眉睫。单一的环境性能友好制冷剂在低温下都或多或少存在一些问题,但利用它们的混合物将弱化其中单一制冷剂的弱点,强化单一制冷剂的优点,有可能组合出低温性能优良的制冷剂混合物。本文将围绕制冷剂的优选和新型制冷剂性能展开。本文首先对混合制冷剂的组分进行筛选。在甲烷和乙烷的衍生物、自然制冷剂以及碳氢制冷剂中,根据环境性能、安全性能、物理化学性能、热力性能和循环性能的优劣对制冷剂进行筛选。最终确定了R290和CO₂为最佳的制冷剂组合。凝固点温度的确定。CO₂在混合物中的凝固点温度随着其分数的增加而升高。为了找到混合物在-70℃左右的凝固点温度,运用CO₂和备选组分的非理想溶液的固液平衡模型,采用活度系数修正的方法使得计算出的溶解度更加精确。混合物受凝固点温度的影响,使得CO₂在混合物中组分受到限制。新型制冷剂组分配比的确定。根据不同组分配比的R744/R290混合物热力性能和安全性能,以及循环性能的差异最终确定混合制冷剂R744/R290（71%/29%）。通过最小不可逆（火用）损失和部件（火用）损失法两种模型的有机结合,计算得到复叠制冷系统主要部件的最小不可逆换热温差和最小不可逆（火用）损失,精确地计算了系统各部件的总体（火用）损失,准确地得到系统的可进一步优化的量。最后,在搭建的复叠制冷系统实验台上,将不同组分的R290和CO₂进行实验,找到循环性能随组分变化规律,验证了理论选择的新型制冷剂的正确性。同时将新型制冷剂与R13进行了循环性能对照,结果表明,新型制冷剂的制冷量和COP均优于R13。新型制冷剂的连续稳定性实验则表明新型制冷剂安全可靠,稳定性好。更多还原

【Abstract】 Industry refrigerant predominated by R13 has greatly damage effect on its ambient environment. For this, R13 has been phased out by the year 1996 in developed countries and before 2010 in developing countries. The alternative refrigerants of R13 such as R23 and R508b also have some disadvantages in the substitute process. And these alternative refrigerants are quite expensive. It is important to find alternative refrigerant which has good enveironmental, thermodynamical performance and low cost.Pure refrigerant which is friendly with ambient environment has some problems when used at low temperature. However, when mixed by two of them, the defects will be weakened and the merits will be swelled. And then the mixture will has good low temperature performance. In this paper, an environmental-friendly new alternative refrigerant was proposed, and performance of the new refrigerant was forcased in theory, and related experiments were carried out.At first, compositions of mixture were chosed from methane and ethane derivatives, natural refrigerants, and hydrocarbons refrigerants by environment performance, safty performance, physics and chemical performance, transmitting performance, thermodynamics and cycle performance. Then the binary mixture composed by R290 and CO₂ is considered as the best low temperature refrigerant.Second, freezing point temperature of mixture was found. Freezing point temperature of mixture moves up with the increasing of CO₂ fraction. In order to find the exact freezing point temperature at around -70℃, solid-liquid equilibrium model of non-idea solution was set up. The modifying of activity coefficient makes the solubility calculating more accurate. Influnced by the freezing point temperature of mixture, the fraction of CO₂ was limited in mixtures.The mixture ratio was determined. Based on the difference of thermodynamics, safety and cycle performance the mixture ratio of R290 and CO₂ was confirmed as 29% and 71%.By the organic combination of the least irreversible exergy loss method and com- -ponent exergy loss method, two exergy losses were obtained as follows: one was the least irreversible exchanging heat temperature difference and the least irreversible exergy loss, the other was the whole exergy loss of refrigeration system components. All of these gave the more accurate values for the system to improve its performance. Finally, at the cascade refrigeration sytem experiment table, experiments about diffent mixture ratio of R290 and CO₂ were done and then found the rules that cycle performance varied with the changing mixture ratio, and validated the new refrigerant chosed in theory. The experiments on the cycle performance comparison of R13 and the new refrigerant showed that the new refrigerant had more refrigeration capacities and COP. And the consecutive stability experiments showed that the new refrigerant was safety and stability.更多还原