考虑热辐射效应的泡沫金属有效导热系数数值分析

Numerical Analysis of the Effective Thermal Conductivity of Metal Foams With Thermal Radiation Effects

有效导热系数是泡沫金属工程应用中传热相关设计的一个重要参数。该文基于简化元胞结构模型,通过直接求解样品内部导热微分方程和辐射传递方程,研究FeCrAlY开孔泡沫金属的有效导热系数。比较了基于剖球模型与传统等截面支架搭接模型的计算结果,分析剖球模型下孔隙单元尺寸、孔隙率、样品平均温度等因素对有效导热系数的影响。研究结果表明,孔隙单元结构对有效导热系数的影响很大,不能仅通过孔隙率和孔隙数密度来研究有效导热系数的变化规律。高温下辐射传热占主导,孔隙率越高,孔隙越大,有效导热系数对温度越敏感。增大孔隙率、减小孔隙尺寸、降低工作温度等会减小泡沫金属的有效导热系数。基于简化几何模型的直接数值模拟可以作获得泡沫金属有效导热系数的一种行之有效的方法。

The effective thermal conductivity （ETC） of metal foams is an important property for thermal designing in related engineering applications. The ETCs of FeCrA1Y open-cell foams were studied by solving the conductive- radiative heat transfer equations based on simplified geometrical models. The results based on the sphere-subtracted structure and that based on traditional structures with uniform ligaments were compared, and the effects of porosity, pore size and bulk mean temperature on ETCs were analyzed. The results show that the cell morphology affects the ETCs significantly, which implies the variations of ETCs can not just be studied by changing the porosity and pore size. Thermal radiative heat transfer is the dominant heat transfer mode at high temperature. The ETC becomes more sensitive to the temperature with the increase of porosity and pore size. Larger porosity, smaller pore size and lower temperature will lead to a lower ETC. It is demonstrated that direct numerical simulation based on simplified models is an efficient way to estimate the ETCs of metal foams for academic and engineering applications.