Development Of The Heat Transfer Module For Green Envelope Based On DeST

Green envelope is a passive energy-saving technology effective in thermal insulation,reducing the cooling load by reducing the heat flux through the envelope surface with the help of transpiration and evaporation.Normally,equivalent thermal resistance is used for estimating the influence of green envelope in cool load.Equivalent thermal resistance is an accessible parameter for designers to estimate the annul energy consumption rapidly.Nevertheless,this parameter can't estimate the dynamic cooling load in small time step because the ignorant of transpiration and evaporation.On the contrary,dynamic heat transfer simulation of green envelope can describe the transpiration of vegetation and evaporation of substrate accurately.It also has advantage and high accuracy in both short term and long term cooling load calculation.However,the domestic energy simulation software Designer's Simulation Toolkit(De ST)can't calculate the effect of green envelope because its lack of green module.In order to solve these problems,we conduct the following work:(1)Base on Beer's law,we developed a dynamic optical parameters model,modified the solar radiation algorihm in Fast All-season Soil Strength(FASST)model.Besides,we used Penman-Monteilh(P-M)equation to modify the evaporation and transpiration algorihm in FASST model.Then we had a modied FASST model for green envelop dynamic heat transfer calculation including modules of green roof,green fa?ade and green wall.(2)Developed a green envelope calculation program in C++ based on the modified FASST model,conducting field experiment of green wall,using the data measured to validate the program's accuracy in green wall simulation,using the measurement data of former research to validate the program's accuracy in green roof and green facade simulation.Compared with the measurement result,the MBE and RMSE of envelope internal surface temperature calculated by our module were lower than 1 °C.(3)Integrated the green envelope calculation program into De ST,executting a cosimulation with De ST in green envelope simulation and analyzing the co-simulation result of green roof,green fa?ade and green wall.The influence of substrate moisture content,leaf area index(LAI),leaf angle distribution(LAD),and minimum stomatal resistance to vapor diffusion in energy efficientcy was anylised.The energy efficientcy had a linear correlation with LAI and minimum stomatal resistance to vapor diffusion,while had an asymptotic correlation with substrate moisture content and LAD.In this paper,we modified the FASST model for heat transfer calculation of envelope,realized the dynamic building energy simulation for green envelope,promoted the application of green envelope.