边界层方程求解传热传质复合自然对流的偏差分析

引　言动量、能量及质量的边界层方程是Naveir Stokes完整方程的简化形式 ,自上世纪初提出以来 ,应用极广 .传热传质复合自然对流是自然界和工业过程中常见的现象 ,由于存在热与物质扩散两种浮力相对大小及方向的差异以及Prandtl数和Schmit数的影响 ,使该问题颇为复杂 .Bottema

DEVIATION ANALYSIS OF BOUNDARY LAYER SOLUTIONS FOR COMBINED HEAT AND MASS TRANSFER BY NATURAL CONVECTION

Numerical analyses were made for combined heat and mass transfer by natural convection on a vertical surface. Both boundary layer equations and full equations of momentum,energy and mass were solved by using a control-volume formulation, and the results were compared in detail for velocity, temperature, concentration, Nusselt and Sherwood number profiles. The discrepancies of boundary layer analysis from full equations under different values of buoyancy ratio B were systematically investigated for Pr/Sc>1,Pr/Sc<1 and Pr/Sc=1. The value of buoyancy ratio B_min predicted by boundary layer equations at the minimum heat and mass transfer rates was consistent with that of full equations solutions. The boundary layer analysis did not predict the velocity, temperature and concentration profiles accurately at Pr/Sc≠1 in the region near B_min. The maximum deviations of Nusselt and Sherwood numbers occurred near B=-1, and they were 40 percent and 21 percent respectively for Pr/Sc=3.18, and 40 percent and 35 percent respectively for Pr/Sc=0.14. The boundary layer equations might predict the heat and mass transfer rates rather accurately except the region near B_min, however, the deviation tends to increase with increasing ｜B｜.