Study On In-situ Measurement Method Of Heat Transfer Coefficient Of Exterior Wall Of Building Envelope

With the development of society,building energy consumption is increasing year by year,so building energy efficiency is the problem that is needed to attach great importance to.The detection of heat transfer coefficient of building envelope has an important function and meaning for the development of building energy efficiency.Heat flow meter method,the hot box method,dynamic analysis method and infrared thermal image method are included in the testing methods of heat transfer coefficient of building envelope.Hot box method and the dynamic analysis method have high accuracy and small error while the field testing condition is strict;Infrared thermal imager method is still in the exploration stage and the technology is not yet mature;The heat flow meter method is simple and accurate while it is affected by the season.It is the most widely used testing method currently.The heat flow meter method is used to detect the heat transfer coefficient of building envelope in this paper.The heat flux density,cold and heat side surface temperature of the wall and ambient temperature are detected by heat flow meter method in this paper.The heat exchange resistance,heat transfer resistance and heat transfer coefficient of cold and hot side are calculated by the instruments.According to the material composition and structure of the wall,the thermal resistance and heat transfer coefficient of the wall under ideal condition are calculated by the principle of heat transfer.Then the field detection value is compared with the theoretical value.The results show that the field detection value of the heat transfer coefficients of the envelope and the theoretical value in Jiangxi Province Foreign Trade College,Nanchang County Indoor Stadium,Jiali Nanchang Comprehensive Development Project and Fuzhou City Tang Xianzu Memorial Hall were 0.60 w/(m~2·k)and 0.634 w/(m~2·k),0.66 w/(m~2·k)and 0.678w/(m~2·k),0.56 w/(m~2·k)and 0.599 w/(m~2·k),0.94 w/(m~2·k)and 0.988 w/(m~2·k)respectively.The relative errors between the field detection value and the theoretical value are 5.36%,2.65%,6.51% and 4.86% respectively.So the heat flow meter method used in this paper has good accuracy.In the process of the theoretical calculation of heat transfer coefficient,the heat transfer process of the heat flow meter method is simplified as one-dimensional steady-state heat transfer while the direction that heat flow passes through the wall is not the only in the actual process.It is the form of three-dimensional to pass around.There are so many heat flow components that the heat flow value detected on site has a certain loss.The value of the heat flow and heat resistance is smaller and the heat transfer coefficient is bigger,which makesthe field detection value of the heat transfer coefficients exist error compared with the theoretical value.