Study On The Impact Of Permeable Laying Material On Outdoor Thermal Environment

With the accelerated urbanization process in China, a lot of agricultural land haschanged into urban land. Farmland, woodland, grassland and other natural permeablematerial is replaced by asphalt, concrete, artificial non-permeable material, tofundamentally change the characteristics of the underlying surface, lead to the heatisland effect. The existing domestic research on artificial permeable materials aremostly concentrated in replenishing groundwater, reduce the surface runoff duringrainstorm. The research of the impact of artificial permeable materials on the outdoorthermal environment is few.According to the basic theory of the permeable material, this paper analyzes theflow of air and water in permeable material, and established evaporative cooling modelof permeable material. Then this paper introduced the common permeable pavementsystem used in China and its flow-producing mechanism.In order to analyze the impact of the permeable material on outdoor thermalenvironment in the practical application, three different types of underlying surface,natural soil, permeable brick, non-permeable brick, were tested in ChongqingUniversity Huxi Campus. According to the experiments after rain in four seasons, thefollowing conclusions are drawed. Under the condition of faint solar radiation and lowair temperature, the difference of surface temperature among these three underlyingmeterials is not obvious. Under the condition of strong solar radiation and high airtemperature, both the natural soil and permeable bricks can lower their surfacetemperature through a passive evaporative cooling after rain. Natural soil has the bettercooling effect than permeable bricks and can continue cooling effect longer. Thepermeable bricks in the practical application are focus on the infiltration of rain waterand lack of rainwater storage, therefore, its continuous cooling capacity is relativelyweak.Based on the circumstances above, permeable bricks which have a better coolingeffect were developed. First permeable bricks made of different particle sizes andsurface colors were produced. Then the saturated moisture content and passiveevaporate experiment of different types of bricks were tested. Considering a variety of factors, a type of permeable bricks with a lager moisture content and better coolingeffect was chosen.