微通道换热器大温差条件下流动换热研究

随着高效预冷器在航天航空领域发挥越来越重要的作用,紧凑高效换热器的研究成为了人们关注的热点。本文基于紧凑微通道换热器的几何特征,针对矩形截面平行流道换热器内超临界压力低温流体(氢和氦)在大温差条件下的流动换热现象进行数值模拟研究。通道截面边长小于1 mm,热流体氦和冷流体氢的进出口温差均大于600 K。通道内流体换热系数在顺流和逆流条件下有不同的变化趋势,并出现峰值。换热量随着通道宽度的增大而增大,流动压降随着通道宽度的增大而减小。冷热流体逆流时换热量大,压降较小,但对换热器材料要求较高。

Investigation on Flow and Heat Transfer in Microchannel Heat Exchanger With Large Temperature Differences

As the high efficiency pre-cooler plays an important role in the field of aerospace,the study of high efficiency compact heat exchanger becomes a concerned topic.Based on the geometric characteristics of the compact microchannel heat exchanger,the flow and heat transfer of cryogenic fluids(hydrogen and helium)at supercritical pressures in parallel heat exchanger with a rectangular cross-section is numerically investigated.The length and width of the channel cross-section is less than 1 mm.The temperature differences of the hot fluid helium and the cold fluid hydrogen at the inlets and outlets are greater than 600 K.It is shown that the heat transfer coefficient in the channel has different patterns of variations and peak values under the conditions of parallel-flow and counter-flow.The heat transfer increases with the increase of the channel width,and the pressure drop decreases with the increase of the channel width.When the hot and cold fluids are countercurrent,the heat transfer is better than the co-current condition and the pressure drop is smaller.