Visualization of Air-Water Two-Phase Flow Distribution in Multi-Plates Heat Exchanger at different header baffle configuration

• Main Authors: Yao-hung Chiang, 江曜宏
• Other Authors: Chien-Yuh Yang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/u49qu5

碩士 === 國立中央大學 === 機械工程學系 === 103 === In this study, air-water two phase flow visualization experiment has been carried out using transparent acrylic plate heat exchanger to understand the flow distribution inside header and channels. The purpose is to simulate the refrigerant’s flow distribution inside evaporator using air-water as working fluid and improve the flow distribution by introducing the baffles. Experiments are carried out for Reynolds numbers ranging from 50 to 250 for two different baffle arrangement, namely, baffle on top and baffle on bottom of the header. Detailed studies on the effect of different baffle flow area ratio, header inlet flow area ratio, and baffle spacing are also carried out. The result shows that the insertion of baffle into the inlet of header has significant affect on flow distribution inside the plate heat exchanger without any header inlet flow area restriction. The baffle arrangement on upper half of the header showed uniform air-water mix in comparison to baffle arranged on bottom half of the header. So out of three different baffle flow area ratios (25%, 50% and 75%)at baffle arranged on upper half of header configuration, 25% and 50% flow area ratio significantly improved air-water mix compare to 75%. Between 25% and 50% flow area ratio, there is no significant difference in air-water mix has been observed. By restricting the flow at the entrance of header using baffle, the result showed significant improvement of air-water mix. Under restricted inlet flow condition, the baffle spacing on 5 channels, a uniform air-water flow distribution is achieved. But the pressure drop significantly increased.