两相冷却微通道在瞬态热流下热响应特性仿真分析

Simulation Analysis of the Thermal Response Characteristics of Two-Phase Cooling Microchannel under Transient Heat Flow

对微通道换热器建立二维流动换热模型,研究阶跃热流对其热力学参数的动态响应特征。讨论了不同工况下壁面不同位置传热量、传热系数、干度和温度的热响应动态特性,获得了定量表征不同工况下热响应模式的相图,分析了变工况对均温性的影响。结果表明,微通道壁温在面对瞬时高热流时呈现单调上升、超调稳定或超调上升三种响应模式,三种模式可能在同一工况下同时存在。超调稳定模式下,增大流量和减小热流有助于弱化超调温度,减小超调时间;超调上升模式下,干度越高管壁飞升温度越大。稳定干度小于0.2时管壁处于单调上升模式,在0.20~0.67之间时出现超调稳定模式,超调上升模式在出口干度大于0.67时出现。增大流量,减小热流等方式可以有效提高管路均温性能。

A two-dimensional flow heat transfer model is established for the microchannel heat exchanger,and the dynamic response characteristics of the step heat flow to its thermodynamic parameters are studied.The thermal response dynamic characteristics of heat transfer,heat transfer coefficient,quality and temperature at different positions of the wall under different working conditions are discussed,and the phase diagrams that quantitatively characterize the thermal response mode under different working conditions are obtained.The influence of variable working conditions on temperature uniformity is analyzed.The results show that the microchannel wall temperature exhibits three response modes,i.e.,monotonically rising,overshooting stable,and overshooting rising in the face of instantaneous high heat flow,and the three different modes may coexist under one same operating condition.In the overshoot stable mode,increasing the flow rate and reducing the heat flow will help to weaken the overshoot temperature and reduce the overshoot time.In the overshoot rising mode,the higher the quality is,the higher the temperature of the tube wall will be.When the stable quality is less than 0.2,the pipe wall is in a monotonic rising mode,when the stability quality is between 0.2 and 0.67,an overshooting stable mode occurs,and the overshooting rising mode occurs when the outlet dryness is greater than 0.67.Increasing the flow rate and reducing the heat flow can effectively improve the temperature uniformity of the pipeline.