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Development of Microchannel Heat Exchanger for Refrigeration

制冷用微通道换热器的研制

基本信息

批准号：
09555071
负责人：
SUZUKI Yuji
金额：
$ 8.7万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555071/
关键词：
Microchannels Heat Exchanger Heat Transfer and Flow Characteristics Two Phase Flow Phase Change

项目摘要

An experimental study on two-phase flow, nitrogen gas and water (or glycerin solution), in microchannels has been conducted to investigate characteristics of fluid flow and heat transfer. An array of 25 parallel microchannels was fabricated on a stainless steel plate by electric discharge machining process. Dimensions of the microchannel are 209 μm high, 212μm wide and 9.96 mm long. Pressure drop across the channels was measured and flow behavior was simultaneously recorded with a high speed video camera. Temperatures of the wall and fluid were measured to determine heat transfer coefficients at the channel surface. The results show that the Chisholm's parameter C for two-phase flow in microchannels is smaller than that in conventional-sized channels and the parameter was well correlated with the flow patterns in case of nitrogen gas and water. Nusselt numbers obtained in single-phase experiments agree approximately with Peng and Peterson's experimental results. In two-phase experiments, heat transfer was enhanced with the stirring effect by gas flow and Nusselt number reaches twice as large value as that in liquid single-flow.Flow and thermal characteristics of a new type of microchannel heat exchanger were examined experimentally concerning the both cases of single and two phase flow. The heat exchanger is composed by laminating thin stainless-steel plate of 200μm thickness with microchannels of 250μm width, and other plate with manifolds (i.e. header & footer) alternately. The microchannel heat exchanger was shown to have higher overall heat transfer coefficient than that of conventional heat exchangers. The performance of the microchannel heat exchanger in liquid phase region was shown to be predicted by the characteristics of laminar flow. In case of boiling of working fluid, large pressure drop appeared for a few bubbles but rapid increase of heat transfer rate was not observed until hard boiling.

对微通道中氮气和水（或甘油溶液）的两相流动进行了实验研究，探讨了流体流动和传热特性。采用电火花加工工艺在不锈钢板上制备了25个平行微通道阵列。微通道尺寸为209 μm高，212μm宽，9.96 mm长。通过高速摄像机测量了通道上的压降，同时记录了流动行为。测量了壁面和流体的温度，以确定通道表面的传热系数。结果表明，微通道中两相流的Chisholm参数C小于常规尺寸通道，且在氮气和水的情况下，该参数与两相流的流型具有良好的相关性。在单相实验中得到的努塞尔数与Peng和Peterson的实验结果大致一致。在两相实验中，气体流动的搅拌作用增强了传热，努塞尔数达到液体单流时的两倍。对一种新型微通道换热器在单相流和两相流情况下的流动和热特性进行了实验研究。换热器由厚度为200μm，微通道宽度为250μm的不锈钢薄板与带有歧管（即头、脚）的其他板交替层合而成。结果表明，微通道换热器具有比传统换热器更高的总换热系数。用层流特性可以预测微通道换热器在液相区的性能。工质沸腾时，少数气泡出现较大的压降，但直到硬沸腾时传热速率才迅速增加。