不同屋顶结构下室内自然对流传热数值分析

Numerical analysis on indoor natural convection heat transfer in different roof structure

以室内自然对流传热过程为研究对象,采用质量守恒方程、能量守恒方程进行数值计算,给出了Ra数在10~3～10~8之间时,三种不同屋顶结构下室内等温线、流体流线的分布特征和Nu数的变化特征.分析结果表明:随着Ra数的增大,等温线由近似竖直变为水平,靠近高、低温壁面有边界层的产生,高Ra数下的室内气流变得紊乱;三种屋顶下的Nu数曲线形状相似,Ra=10~3时拱形屋顶的Nu值最大,高Ra数时平屋顶房屋的Nu值最小,换热效果较差;拱形屋顶Nu与Ra的拟合公式为:Nu=0.316Ra^(0.262).

The research object is the process of indoor natural convection heat transfer. Mass conservation equation and energy conservation equation are used to make numerical calculation. This paper presents the distribution characteristic of indoor streamlines and isotherms as well as the variation characteristic of Nu in three different roof structures with Ra among 10^3~ 10^6. Results of analysis indicate that the iso- therms turn from nearly vertical to level and boundary layers arise near the hot wall surface and the cold wall surface when increasing Ra. The indoor airflow turns into a turbulence when Ra value is high. The Nu curve shape of three roof structures is similar. When Ra= 10^3, the vaulted roof＇s Nu value is the highest. When Ra value is high, the flat roof＇s Nu value is the lowest with the worst heat transfer effect. The fitting formula of Nu and Ra in vaulted roof is Nu=0. 316Ra0.262.