两种不同通道内周期性充分发展流动换热的模拟研究

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.

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

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.