两种不同通道内周期性充分发展流动换热的模拟研究

Simulation of Periodically Fully Developed Flow and Heat Transfer in Two Different Channels

周期性直肋通道是从不同型式的高效换热器中抽象出来的通道模型,采用非稳态数学模型,应用周期性充分发展的假设模拟了周期性矩形直肋通道(A)和半圆形直肋通道(B)内的流动换热情况,并对两种通道的换热特性及其所表现出来的非线性特性进行了对比.计算时采用低雷诺数Re、二维、层流强制对流模型.结果表明,当Re较小时,流动与换热处于稳态;当Re大于某一临界值时,流动与换热发生了非稳态振荡,系统均表现出丰富的非线性现象.在计算范围内,A通道随着Re的增大经历了稳态与周期性振荡阶段;B通道则先后经历了稳态、周期性振荡、拟周期振荡以及混沌状态.

Periodic channels with different shapes of straight rib are abstracted from different types of high-efficiency heat exchangers.The heat transfer and fluid flow in the periodic rectangular straight rib channel （A）and the semi-circular straight rib channel （B）were simulated based on the unsteady-state mathematical model under the assumption of periodically fully developed flow.Meanwhile,the heat transfer properties and the demonstrated nonlinear characteristics in two different channels were compared.A low Reynolds number Re ,two-dimension,laminar forced convection model was adopted when calculated.It is found that when Re is small,the flow and heat transfer present a steady state;when Re is larger than the critical value, unsteady oscillation occurs,and the system shows rich nonlinear phenomena.In the range of calculation,channel A has experienced steady and periodic oscillation phases with the increase of Re ;channel B has experienced steady,periodic oscillations,quasi-periodic oscillations and chaos with the increase of Re .