两种不同工质在微通道内沸腾换热特性的实验研究

Experimental Study on the Boiling Heat Transfer Characteristics in Micro-channel with Two Different Working Medium

为研究流体物性、流动和换热过程的状态参量对微通道内沸腾换热特性的影响规律,本文采用去离子水和无水乙醇在当量直径为0.293 mm的矩形微通道进行了不同质量流量和热流密度条件下的沸腾换热实验研究,通过对实验数据的计算和处理,分析总结了流体的热物性、质量流量、热流密度、干度和Bo数等参量对沸腾换热系数的影响规律。结果表明:沸腾换热系数随着热流密度、干度和Bo数的增大而降低,核态沸腾占主导地位;相同的质量流量和热流密度条件下,去离子水的沸腾换热系数明显高于无水乙醇的沸腾换热系数,并且前者的换热系数随质量流量的增大而增大,而后者变化不明显。根据考虑了通道尺寸效应及流体物性参量总结出的换热系数关联式进行了计算,计算结果对去离子水和无水乙醇的平均绝对误差分别为14.2%和16.6%,可认为该关联式适用于微通道内沸腾换热系数的预测。

Experiments are performed in rectangular micro-channels （ dH = 0. 293 mm） under the condition of different mass flux and heat flux to evaluate the flow boiling heat transfer characteristics with deionized water and anhydrous ethanol. Research in micro-channels is aimed at studying the influence rule of state parameters of fluid properties, flow and heat transfer process of boiling heat transfer characteristics. According to the calculation and comparison of experimental data, the relationship between boiling heat transfer coefficient and thermal physical properties of fluid, mass flux, heat flux, vapor qualities, Boiling number are presented respectively. The results show that boiling heat transfer coefficient decreases with the increasing of heat flux, vapor qualities and Boiling number. Nucleate boiling is dominant in the process of heat transfer. Under the same condition the boiling heat transfer coefficient of deionized water is obviously higher than the boiling heat transfer coefficient of anhydrous ethanol. The heat transfer coefficient of deionized water increases with the increasing of mass flux, but anhydrous ethanol has no significant changes with mass flux. The results from heat transfer correlation taking scale effect and fluid properties into consideration have 14.2% and 16.6% MAE （ Mean Absolute Error） for deionized water and anhydrous ethanol respectively. It proves that the heat transfer correlation has good applicability of predicting the boiling heat transfer coefficient in micro-channels.