排风隔热墙的多孔渗流层临界厚度研究

Research on Critical Thickness of Porous Seepage Layer of Ventilation and Thermal Insulation Wall

排风隔热墙是一种新型节能外墙,本文利用其一维稳态传热简化解析模型,结合达西定律,获得了室内空气与外墙内表面之间的换热热流密度与多孔渗流层厚度的关联式.通过对给定压差条件下热流密度的极值分析,论证了渗流层临界厚度的存在,导出了该厚度的一维模型准确解及其近似计算公式.经过与墙体传热过程的二维数值计算结果相比较,发现获得的临界厚度的准确解误差小于2%、近似解误差小于4%,适合工程计算和分析.对排风压差、渗流层导热系数、外层结构热阻对临界厚度的单因素分析表明:随着排风压差、多孔材料导热系数及外层结构热阻的增大,渗流层临界厚度大致呈线性增加的趋势。

Ventilation and thermal insulation wall is a new-type of energy saving exterior wall. This paper obtains the correlation between the heat transfer flux（ indoor air and inner surface of the exterior wall） and the critical thickness of the porous seepage layer,by relying on the simplified analytical model of the one-dimensional steadystate heat transfer of the ventilation and thermal insulation wall,as well as the Darcy Law. Through analysis of the extreme value of heat flux under the given differential pressure,the paper proves the presence of the critical thickness of the seepage layer,and derives the exact solution and the approximate computational formula of the thickness one-dimensional model. By comparing with the two-dimensional numerical simulation calculation results of the wall body heat transfer process,it is found that the error of the exact solution of the critical thickness is less than 2%,and the approximate solution less than 4%. This proves that it is suitable for engineering computation and analysis. The single factor analysis（ factors： ventilation differential pressure,heat conductivity coefficient of seepage layer,thermal resistance of external structure） regarding the critical thickness indicates that the critical thickness of the seepage layer roughly increases linearly,when the ventilation differential pressure,porous material conductivity coefficient,and thermal resistance of external structure increase.