流体热物性对粗糙微通道内传热性能的影响

为了明晰工质种类对微通道传热性能的影响,研究了导热系数λ,比热容cp,动力粘度μ和密度ρ影响微通道传热性能的规律。首先研究了水和煤油在构造的粗糙微通道中流动与传热性质的差异,然后将各个因素孤立的研究其对于整体传热性能的影响。结果发现,在粗糙微通道中的层流充分发展流动状态,Poiseuille数(Po)基本不随Re变化,也不随工质热物性变化;水和煤油的Nusselt数(Nu)都随Re的增大而增大,且煤油的Nu的数值和随Re的增长率都大于水的对应值。研究还发现,Nu随着λ的增加而减小,随着cp和μ的增加而增加,不随密度ρ变化;同时,λ和μ对Nu的影响比cp大。

Effects of thermal properties of the working fluid on heat transfer characteristic in rough microchannels

The effects of thermal properties on the heat transfer patterns in rough microchannels have been investigated using numerical simulations.The four thermal properties are: thermal conductivity λ,specific heat capacity cp,dynamic viscosity μ,and density ρ.A simple microchannel was modeled with rectangular roughness.The effect of the Reynolds number(Re) was examined on both flow and heat transfer for water and kerosene.Then each thermal property parameter was separated from others to check the effects on heat transfer,with the respective variations of corresponding values from water to kerosene.It was found that in the developed laminar flow through the rough microchannels,the Poiseuille numbers(Po) were almost independent of Re and the kind of fluids,but the Nusselt numbers(Nu) of both fluids increased with Re.In addition,the value and the incremental rate of Nu for kerosene were larger than the corresponding values for water.Finally,results showed an increase in Nu with the decrease of λ,with the increase of cp and μ.And cp showed a weaker effect on Nu than λ and μ.