逆流式微通道换热器设计与操作特性分析

Conjugated heat transfer in micro-channel heat exchanger

采用一维对流导热耦合模型对逆流式微通道换热器传热特性进行分析和模拟, 考察了结构参数、操作条件和材质热导率对微换热器整体效率的影响. 计算结果表明, 由于器壁径向和轴向传热的相互影响, 与常规尺度换热器相比, 微通道换热器的设计和操作特性有许多明显不同的特征. 微通道换热器存在最佳操作流量值, 该值可作为标准负荷流量, 微换热器不宜在亚负荷状态下操作; 操作流量越大, 微通道换热器最大换热效率越低;微换热器结构采用大深宽比通道和适当的间壁厚度为佳.

Conjugated heat transfer performance in a countercurrent micro-channel heat exchanger was analyzed and simulated by using the one dimensional gas convection and wall axial heat conduction model. The effects of structural parameters, operating conditions and heat conductivity of wall material on the performance of heat transfer of this micro-channel heat exchanger were investigated. The simulation results indicated that the properties of micro-channel heat exchanger were much different from those of conventional heat exchanger due to the synergetic effect of radial and axial heat conduction in the micro-channel heat exchanger. Low conductivity metal, such as stainless steel, is an excellent wall material and available for micro-channel heat exchanger. There existed an optimal operation flux, which could be used as a standard flux for a given micro-channel heat exchanger, and micro-channel heat exchanger was not suitable when the operation flux was lower than the standard flux. The maximum heat transfer efficiency of micro-channel heat exchanger decreased with the increase of operating flux. The calculation results also showed that micro-channel heat exchanger with high aspect ratio channel and optimal wall width had higher efficiency than other configurations.