非稳态流动对管内湍流换热的增强机理  

Mechanism of Heat Transfer Enhancement in Unsteady Turbulent Flow in a Pipe

作　　者：耿丽萍[1] 吕海彬[1] 王玉刚[1] 周静伟[1] 

机构地区：[1]中国计量学院热能工程系,杭州310018

出　　处：《工程热物理学报》2016年第5期1071-1075,共5页Journal of Engineering Thermophysics

基　　金：国家自然科学基金项目(No.51206153);浙江省自然科学基金(No.LY15E060005)

摘　　要：通过对非稳态管内湍流流动及换热的数值模拟,发现决定非稳态信号强弱的因素对换热效果的影响不同。频率因素的影响非常有限,而振幅因素的影响在无量纲幅值小于1的情况下也不明显,但是当无量纲幅值大于1时,管内流动的换热强化非常显著,同时管内流动的阻力系数也有显著增加。由于幅值大于1带来的流动反向导致管道内的流动剧烈振荡,靠近壁面处的速度梯度在短期内发生大幅度改变并降低壁温,从而导致换热效果的显著增强。Numerical simulations are conducted in which the unsteady air flowed through a pipe and heated by the wall with a constant heat flux.The unsteadiness factors,amplitudes and frequencies,showed different influence to heat transfer performance.The influence of frequencies is very limited.Same situation appeared when dimensionless amplitudes are less than 1.However,when the dimensionless amplitudes are more than 1,heat transfer enhancement in the pipe is obvious and so with the increase of friction factors.Since the reversal flow will appear when dimensionless amplitudes are larger than 1,the large velocity oscillatory amplitude and velocity gradient near the wall appeared in a very short time.This caused the decrease of wall temperature.Thus appreciable heat transfer enhancement occurs with large dimensionless amplitudes.

关 键 词：非稳态 振幅 频率 强化换热 

分 类 号：TK124[动力工程及工程热物理—工程热物理]