ABSTRACT

In order to improve the heat transfer performance of the microchannel heat exchanger, a composite heat transfer enhancement method was proposed. Viscoelastic fluid was used as working fluid in pulsating flow condition, and rib plates were added to the microchannel to bring extra disturbance to the flow. The Oldroyd-B constitutive model of the viscoelastic fluid was used in the numerical simulation, and the flow field, temperature field, Nusselt number (Nu), and pressure drop were analyzed when the average Reynolds number (Re) is 10. Both Strouhal number (St) and amplitude are important factors affecting heat transfer, but they have an insignificant influence on pressure drop at low Reynolds number. The St = 0.125 and amplitude A = 0.8 are better parameters. The increase of Weissenberg number (Wi) will cause the vortex to split into several subsidiary vortexes during its development, which will also develop to various positions in the channel, thus further enhancing the heat transfer. When the Wi is in the range of 1 ~ 5, the performance evaluation criteria rises at a relatively fast rate, from 1 to 1.404.

摘要

为了提高微通道换热器的传热性能，提出了一种复合强化传热方法。在脉动流动条件下，使用粘弹性流体作为工作流体，并在微通道中添加肋板以对流动带来额外的扰动。数值模拟采用粘弹性流体的Oldroyd-B本构模型，分析了平均雷诺数（Re）为10时的流场、温度场、努塞尔数（Nu）和压降。 (St) 和振幅是影响传热的重要因素，但它们对低雷诺数时的压降影响不大。St = 0.125 和幅度A= 0.8 是更好的参数。魏森伯格数（Wi）的增加会导致涡流在发展过程中分裂成多个辅助涡流，这些辅助涡流也会发展到通道中的各个位置，从而进一步增强传热。当 Wi 在 1~5 范围内时，性能评价标准以较快的速度上升，从 1 上升到 1.404。