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Enhancement of Flow Boiling and Condensation Heat Transfer to Alternative Refrigerant Mixtures for HCFC-22 in Tubes

增强管内 HCFC-22 替代制冷剂混合物的流动沸腾和冷凝传热

基本信息

批准号：
08555057
负责人：
YOSHIDA Suguru
金额：
$ 8.7万
依托单位：
KYUSU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08555057/
关键词：
Alternative Refrigerant Mixtures for HCFC-22 Enhancement of Heat Transfer Boiling Heat Transfer Condensation Heat Transfer Horiaontal Flow Pressure Drop

项目摘要

Experiments were made on convective boiling and condensation heat transfer for the flow of alternative refrigerant mixtures of R-410A and R-407C for HCFC-22 inside horizontal micro-fin and herringbone tubes, and following results were obtained.In general, the heat transfer for R-410A can he regarded as a pure refrigerant heat transfer, but the heat transfer coefficient for R-407C reduces due to a mass transfer resistance at low quality and low flow rate in both the tubes.In boiling, the heat transfer coefficient for both the mixtures increases with increasing mass flow rate. With both the tubes, the heat transfer is greatly enhanced over a smooth tube ; enhancement becomes larger in the micro-fin tube at low flow rate but in the herringbone tube at high flow rate. Observations of air-water two-phase flow behavior in both the tubes were made to explain the mechanism of the heat transfer enhancement.In condensation of both the mixtures, the heat transfer coefficient increases with increasing mass flow rate, but there is little effect of heat flux. The enhancement of condensation heat transfer in the herringbone tube becomes larger at low quality and low flow rate compared to the micro-fin tube. A method for predicting the local condensation heat transfer coefficient was developed for the condensation of binary and ternary refrigerant mixtures inside a horizontal smooth tube, and a prediction method was also presented for film condensation heat transfer in the micro-fin tube based on a flow observation.In both the tubes, a pressure drop for R-407C is generally 20 to 30 % higher than that for R-410A corresponding to the difference in the vapor density. The pressure drop in the herringbone tube was a maximum of 50% larger than that in the micro-fin tube.

对HCFC-22的替代工质R-410 A和R-407 C在水平微肋管和人字形管内的对流沸腾和冷凝换热进行了实验研究，得到了以下结果：R-410 A的换热可视为纯工质的换热;而R-407 C在低干度和低流速时，由于传热阻力的影响，传热系数降低，在沸腾时，两种混合物的传热系数均随质量流速的增加而增加。与这两种管相比，光滑管的传热大大增强;在低流速下，微翅片管的传热增强变得更大，但在高流速下，人字形管的传热增强变得更大。通过对两种管内空气-水两相流动特性的观察，对强化传热的机理进行了解释，发现在两种混合物的冷凝过程中，传热系数均随质量流量的增大而增大，但热流密度的影响很小。与微肋管相比，人字形管在低干度、低流量下的凝结换热强化程度更大。针对二元和三元混合制冷剂在水平光管内的凝结换热，提出了一种局部凝结换热系数的预测方法，并基于流动观测结果提出了微肋管内膜状凝结换热的预测方法。R-407 C的压降通常比R-410 A的压降高20 - 30%，这对应于蒸汽密度的差异。人字形管中的压降最大比微肋管中的压降大50%。