Study On Rainfall Interception And Passive Evaporative Cooling Of Ceramsite Roof

With the acceleration of urban construction process,As a result of the change of the underlying surface of the city,the proportion of impervious area increases gradually.When the rainstorm occurs,the time of confluence is shortened and the peak value of runoff increases.Every summer,most cities are frequent waterlogging,while producing a larger urban heat island effect.The roof as building not fully developed the fifth facade,is the source of rainwater,slowing down runoff,thus laying on the roof in the city can be part of the rainwater retention of porous ceramics in a short period of time,delayed runoff time,reduce runoff peak and reduce the city rain and flood disasters.At the same time,after the rainstorm,the moist porous ceramsite can be cooled passively under the solar radiation and the high temperature to reduce the room temperature.Through the establishment of ceramic roof model,to star the experiment of ceramsite roof rainwater interception and passive evaporative cooling.And draw the following main conclusions:The slope of the roof increased from small to large,both the start time of runoff and the arrival time of peak were ahead of schedule,the peak flow increased,and the runoff interception rate decreased,at the same rainfall intensity,.Especially the simulation of heavy rainfall,slope from 3%to 5%and 10%,compared with the stone roof,the ceramsite roof runoff start time delay 1.03min,0.98min and 0.45min respectively,the peak flow was decreased by 0.26L/min,0.24L/min,0.26L/min,radial flow rate increased by 25.38%,21.93%and 20.07%respectively.The height of roof increased slightly,both the start time of runoff and the arrival time of peak were delayed,the peak flow decreased,and the runoff interception rate increased,but the change of ceramsite roof was larger.the simulation of heavy rainfall,the height from 100mm,150mm to 200mm,compared with the stone roof,the ceramsite roof runoff start time delay 0.95min,1.17min and 1.95min respectively,the peak flow decreased 0.27L/min,0.68L/min,0.78L/min,time to peak delay 4min,3min,4min respectively,the runoff interception rate increased 195.2%,28.14%and 36.59%respectively.With the increase of roof height,the capacity of roof closure of ceramsite roof and stone roof is also increased.However,because of the dense structure of the stone and the pore filling inside the ceramsite,the water absorption rate of the ceramsite is larger,so it shows stronger closure capacity.The dry days in the early stage of roof increase gradually,both the time of runoff start and the time to peak arrival are delayed,the peak flow rate decreases,and the runoff interception rate increases.But the change of the ceramsite roof greatly,when the simulated rainfall,the dry early days from Id,3d to 7d,compared with the stone roof,ceramic roof runoff start time delay of 1.07min,1.42min and 2.74min respectively,the peak of runoff decreased 0.21 L/min,0.42L/min,0.52L/min,the corresponding closure rate were decreased by 19.33%,27.67%,33.77%.With the increase of dry days,a part of moisture in the pore of ceramsite will flow out of the body,and the other part will evaporate under the influence of solar radiation and air temperature.In these two cases,the moisture content of ceramsite will gradually decrease,so it will absorb more moisture when it rains.As a result,the number of days before dry increased,and the interception capacity of ceramsite roof under heavy rainfall was more obvious than that on pebble roof.Under the condition of continuous sunny weather,compared with the lawn roof and the stone roof,when the ceramsite roof is in dry state,the evaporation and heat insulation effect is not good;In the case of continuous precipitation,the moist porous ceramsite can be cooled sufficiently under high temperature,on the one hand,most of the energy can be consumed while the ceramsite can block some of the solar radiation directly reaching the roof outer surface,on the other hand,because the ceramsite are filled with pores,the heat of the roof can be taken away from the roof under the action of wind,it can reduce the temperature of the roof outside,reduce the heat from the roof into the room and cut down the energy consumption of the air-conditioning.