Abstract:

The convective mass transfer coefficient on the outer surface of a building is an important parameter in the calculation of the heat and moisture coupling of the enclosure and the simulation of building energy consumption. To get the parameter directly and accurately, a method for measuring the mass transfer coefficient of the wall on the building surface is proposed. The mass transfer coefficient of the naphthalene specimen can be calculated by measuring the mass flux and surface temperature of the naphthalene specimen. To verify the accuracy and reliability of the method, 6 different wind speeds were set up in the wind tunnel, and two pieces of the same experimental wall were made. The naphthalene sublimation method was applied to compare with the traditional thermal balance method. The results show that the surface temperature of naphthalene specimen decreases with the increase of wind speed, and the convective mass transfer coefficient increases gradually. The results of the two methods are close to each other. The difference of the convective mass transfer coefficients between the two methods are less than 10%, and the average deviation is less than 5% under different wind speed conditions. It is considered that the method is feasible. The research can provide guidance for testing the mass transfer coefficient of building external surface under outdoor real conditions, and is also significant for the study of heat and moisture coupling calculation and the evaporation and heat transfer of walls.

Key words: convection, mass transfer, heat transfer, naphthalene sublimation, heat balance

摘要：

建筑外表面对流传质系数是围护结构热湿耦合计算和建筑能耗模拟中的重要参数。为直接准确得到该参数，提出了建筑物壁面对流传质系数的测量方法，该方法通过测量萘试件的质量通量和表面温度，即可计算得到壁面传质系数。为验证该方法的准确性及可靠性，在风洞内设置6组不同风速工况，分别采用了萘升华法与传统热平衡法进行对比。结果表明：随风速的增加，萘试件表面温度随之降低，而对流传质系数逐渐增加。两种方法测试结果接近，二者所得对流传质系数相差在10%以内，不同风速条件下平均偏差小于5%，认为该测量方法可行。该研究可为室外真实条件下建筑外表面对流传质系数提供测试方法指导，对热湿耦合计算和墙体蒸发换热的研究也具有重要意义。

关键词: 对流, 传质, 传热, 萘升华, 热平衡