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FUNDAMENTAL STUFY OF A SMALL-SCALE HEAT PUMP

小型热泵的基础研究

基本信息

批准号：
11450083
负责人：
HIHARA Eiji
金额：
$ 4.48万
依托单位：
THE UNIVERSITY OF TOKYO
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450083/
关键词：
Heat pump Heat exchanger Small diameter tube Micro-channel 微小機構圧縮機

项目摘要

Size reduction of heat exchangers is one of the most important technologies for micro-scale heat pumps. In order to develop small-scale heat pumps, in this study fundamental research of small-scale heat exchangers were executed, which include heat transfer and pressure loss characteristics in small diameter heat transfer tubes, distribution of gas liquid two-phase flow at a T-junction and measurement and simulation of heat exchangers with small diameter tubes.(1) For boiling heat transfer and pressure drop characteristics inside small diameter tubes, the diameter of heat transfer tubes were varied between 0.5 and 3 mm ID, and the HFC134a was selected as a working fluid. For smaller diameter tubes than 1mmID, heat transfer coefficients were deteriorated due to dry out in the quality range higher than 0.5. When the vapor quality at the inlet of the evaporator is less than 0.1, the flow pattern becomes intermittent and heat transfer performance decreases significantly.(2) Phase separation of gas-liquid two-phase flow at an impacting tee was investigated experimentally and theoretically. It was found that if the flow rates in the branches were different, phase separation was observed. Based on the principle of minimum energy dissipation, a thermodynamic model was derived. The results of the model were qualitatively in good agreement with the experimental behavior of impacting flows.(3) The performance of fined small tube heat exchangers was investigated both experimentally and theoretically. The Inner diameters of tubes were 1.0mm, 2.1mm and 4.0mm. Calculation results show that the volume of a 2.0mm tube heat exchanger can be reduced to 33% of that of a 4mm tube heat exchanger with the same capacity. The flow distribution in a branching unit strongly affects the exchanged heat.

换热器的小型化是微型热泵的关键技术之一。为了发展小型热泵，本文开展了小型换热器的基础研究，包括小管径传热管内的传热和压力损失特性、T型管接头处的气液两相流分布以及小管径换热器的测量和模拟。(1)对于小直径管内的沸腾传热和压降特性，传热管的直径在0.5和3 mm ID之间变化，并选择HFC 134a作为工作流体。对于小于1mm ID的较小直径管，由于在高于0.5的质量范围内干燥，传热系数恶化。当蒸发器入口干度小于0.1时，蒸发器内的流动变得断续，传热性能明显下降。(2)对冲击三通内气液两相流的相分离进行了实验研究和理论分析。发现如果分支中的流速不同，则观察到相分离。基于最小能量耗散原理，推导了一个热力学模型。模型的计算结果与实验结果在定性上吻合较好。(3)对翅片管换热器的性能进行了实验研究和理论分析。管的内径为1.0mm、2.1mm和4.0mm。计算结果表明，在相同的处理能力下，2.0mm管换热器的体积可以减少到4mm管换热器的33%。分支单元中的流量分配强烈地影响交换热量。