Boiling and Condensation Heat Transfer for New Refrigerants Flowing in Horizontal Tubes

氢氟醚最近被提议作为包括氢氟碳化物在内的传统制冷剂的替代品，因为氢氟醚具有零臭氧消耗潜能值和较小的全球预警潜能值。HFE245mc和HFE143m分别是替代CFC114特别是用于热回收热泵系统和HFC134a用于制冷系统的替代品。本研究对水平管内流动的HFE245mc和HFE143m进行了沸腾换热和冷凝换热实验。对于每一种新制冷剂，在沸腾传热特性上没有发现与传统制冷剂的特殊差异，这是将测量的局部沸腾传热系数与作者适用于传统制冷剂的相关性进行比较的结果。同样在冷凝过程中，每一种新制冷剂的传热系数都可以通过Hraguchi等人对传统制冷剂的相关性得到令人满意的预测。对比计算结果，HFE245mc的沸腾和冷凝换热系数大于等于CFC114的换热系数。同样，HFE143m沸腾冷凝时的换热系数与HFC134a几乎相等。因此，从传热的角度来看，HFE 245mc和HFE143m分别作为CFC114和HFC134a的替代制冷剂是没有问题的。为了研究HFE245mc和HFE143m在螺旋槽管内流动的传热系数的增强，目前正在进行沸腾和冷凝实验。

Hydrofuluoroethers (HFEs) have recently been proposed as substitutes to conventional refrigerants including HFCs, since HFEs have Zero ozone depletion potential and also smaller global warning potential. HFE245mc and HFE143m are such substitutes to replace CFC114 especially for heat recovery heat pump systems and HFC134a for refrigerating systems respectively. In the present study, experiments were made on boiling and condensation heat transfer for HFE245mc and HFE143m flowing inside horizontal tubes.1. For each new refrigerant, there was found no peculiar difference from conventional refrigerants in the characteristics of boiling heat transfer, as results of comparisons of measured local boiling heat transfer coefficients with the authors' correlation applicable to conventional refrigerants.2. Also in condensation, the heat transfer coefficients for each new refrigerant can be satisfactorily predicted by the Hraguchi et al's correlation for conventional refrigerants.3. Comparing the values calculated from the correlations, the heat transfer coefficient for HFE245mc showed to be higher than or equal to that of CFC114 for boiling and condensation.4. Similarly, the heat transfer coefficient for HFE143m showed to be almost equal to that of HFC134a for boiling and condensation.5. From the standpoint of heat transfer, therefore, there was no problem in the use of HFE 245mc and HFE143m as the alternative refrigerants to CFC114 and HFC134a, respectively.6. In order to study the enhancement of the heat transfer coefficients, now, experiments are being on boiling and condensation for HFE245mc and HFE143m flowing inside spirally grooved tubes.