大温差下印刷电路板式换热器起动过程建模与实验

Modelling and experimental investigation into starting process of printed circuit heat exchangers at large temperature difference

针对大温差下的印刷电路板式换热器(PCHE)的起动过程,提出了一种一维瞬态换热计算模型,该模型考虑了印刷电路板式换热器固体结构的内部导热过程,可计算起动过程中换热介质和印刷电路板式换热器的温度响应。同时以N_(2)为换热介质,开展了印刷电路板式换热器的瞬态换热实验,N_(2)的最高、最低温度分别为450、103 K,将模型计算结果与实验结果进行对比,冷侧N_(2)出口温度的模型计算值与实验值之间的平均误差为11.3 K,实验结束时热、冷侧换热量的计算偏差均在7%以内,该结果证明了所提出的计算模型的有效性。在上述计算模型的基础上,对起动过程中印刷电路板式换热器工作参数的空间分布和时域变化特征进行了计算和分析,结果表明换热器的外侧盖板与固体核心区之间的传热过程非常重要,在进行大温差下的瞬态换热过程计算时不应被轻易忽略,同时增大两侧换热介质的流量和减小换热器外侧盖板的厚度是缩短印刷电路板式换热器起动过程响应时间的有效方法,且在一定的流量比范围内,两侧换热介质入口雷诺数之积是影响响应时间的重要因素。

A one-dimensional transient heat transfer model is developed in this study for the starting process of Printed Circuit Heat Exchangers(PCHE)at large temperature difference.The model considers the internal heat conduction process of the solid material of the printed circuit heat exchanger and is able to predict the temperature behavior of both fluid and solid materials.Transient heat exchanger experiments using N_(2) as the medium on the printed circuit heat exchanger are conducted.The maximum and minimum temperature of N_(2) are 450 K and 103 K,respectively.Com⁃parison of the model prediction results with the experiment results proves the validity of the model.The average devia⁃tion of the outlet temperature at the cold side during the starting process is 11.3 K and the calculation deviations of heat transfer on both sides are within 7%.Furthermore,the model is applied to the calculation and analysis of the spa⁃tial distribution and time domain variation characteristics of the operating parameters of the printed circuit heat ex⁃changer.The results indicate that the heat transfer between the cover plate and the core region of the printed circuit heat exchanger is important and cannot be easily ignored in the simulation of the transient process at large temperature difference.The results also show that increasing mass flow rates of fluid at both sides and decreasing the thickness of the cover plate are effective methods to shorten the response time of the starting process.Moreover,in a certain range of the mass flow rate ratio,the product of the Reynolds Number at the inlet of the printed circuit heat exchanger on both sides is an important factor affecting the response time.