基于场协同原理的泡沫金属热沉流动换热特性模拟

Convection heat transfer simulation for metal foam heat sink based on the field synergy

泡沫金属具有非常大的比表面积和良好的导热性能.为研究不同冲刷方式下泡沫金属的换热特性,建立三维矩形泡沫金属换热模型.通过数值模拟,分析两种不同冲刷方式对泡沫金属热沉特性的影响,以及泡沫金属孔隙率、孔密度、流速对其换热性能的具体作用.模拟结果表明：垂直冲刷方式下,加热面温度均匀性、系统热阻和表面换热系数等换热特性明显优于水平冲刷方式,这与场协同原理是基本吻合.其受热面温度分布均匀性也优于水平冲刷,这是由于在垂直冲刷下,温度场与流场的协同特性得以很大改善所致.文中研究范围无论何种冲刷方式,泡沫金属热沉的换热性能受孔隙率影响较大,孔密度的影响次之,但孔隙率和孔密度对系统压降均起很大作用,流动阻力也随之增大;在相同的孔密度和来流流速条件下,随着孔隙率的增加,Nu数先增大后减小,存在最优孔隙率,当孔隙率处于0.7～0.8范围时,两种冲刷方式下换热性能最好.

Metal foam has large specific surface area and good capacity of thermal conductivity. This paper aims to explore and examine the heat-transfer characteristics of metal foam sink with different inlet flow direction,based on a three-dimensional numerical model. The research tries to identify how the mental foam heat sink characteristics are affected by two different inlet flow directions in order to explore field synergy mechanism in system. Some factors,such as pore porosity,pore density and flow velocity,are also investigated. For some heat sink performance,such as the temperature uniformity of heating surface,system thermal resistance and so on,it is found that horizontal flow mode behaved better than vertical flow mode,which conform to the field synergy theory. The heat transfer performance for metal foam heat sink is firstly influenced by pore porosity,followed by pore density regardless of inlet flow direction. Within the porosity range of 0. 7 to 0. 8,the best heat transfer performance for both kinds of flow direction are obtained.