变物性对微通道内流动与传热的影响

THE INFLUENCE OF VARIABLE THERMAL PROPERTIES ON THE FLOW AND HEAT TRANSFER IN MICROCHANNELS

分别采用入口物性、平均物性和变物性对D_h=0．333 mm、Re=101～1775的矩形微通道内层流流动与传热进行了三维流固耦合数值模拟。将不同方法下局部和平均流动与传热特性的计算结果与新近文献中的实验结果、常见关联式及近似理论解进行了对比分析。结果表明,与入口物性法相比,平均物性和变物性法均获得明显较低的fapp和较高的h_z和Nu_z。与平均物性法相比,变物性法在通道起始段具有更高的fapp Reave和较低的h_z,而在后段具有较低的fapp Reave和较高的h_z。Nuave的计算结果与Sieder-Tate关联式吻合良好,表明传统的宏观数学模型能够正确用于预测本文尺度和Re范围内微通道内的流动与传热特性。

The inlet, average and variable thermal properties were adopted respectively to numerically simulate the 3D conjugate heat transfer and laminar flow in rectangular microchannels with a hydraulic diameter of 0.333 mm and Reynolds numbers of 101-1775. The results of local and average flow and heat transfer performances are compared among different methods, and with the experiments, correlations and simplified theoretical solutions from the open literatures. The results show that, compared with the inlet property method, both the average and the variable property methods have evidently lower lapp, but higher hz and Nuz. Compared with the average property method, the variable property method has higher fappReave and lower hz at the front section of the channel, but lower fappReave and higher hz at the rear stage. The calculated Nuave agree well with the Sieder-Tate correlation. Thereby the validity of traditional macroscale theory is verified in predicting the flow and heat transfer performances for the dimension and Re range in question.