Experimental Study on Heat Transfer through Wall Subjected to Rain in Guangzhou

Located in hot and humid climate region, Guangzhou has strong solar radiation and abundant rain. Its potential of utilizing climate resource is great, and its possibility to realize passive cooling is high. The rain hours are over half of the total hours a year and the annual average rainfall can reach 1830.8 mm. Rain has been found that affect the thermal performance of building walls in two ways, by cooling the surface during rain and by evaporation of the absorbed moisture after rain. The rain process reduces the heat transfer from outside to inside and decreases the energy consumption of building. An experimental study is conducted of the heat transfer process though wall subjected to rain of Guangzhou summer. It has been finished in rainy days. The experiment measures the climate factors, the inner and surface temperatures of the walls, and the heat flows of the wall. The results of the heat transfer measurements show that the effect of rain to the wall's heat transfer is not negligible. At the same time, this article also introduces a handheld microwave moisture meter named MOIST 200B, and proposes a calibration method of the mass moisture of the building material to the moisture index that the MOIST 200B measures. Additionally, the article discusses the moisture change pattern of the cement mortars simply.