Analysis Of Condensation Characteristics And Anticondensation Measures Effect Of Thermal Insulation Wall In Hot Summer And Cold Winter Area

The problem of condensation in the thermal insulation wall is becoming increasingly prominent,which not only affects the thermal insulation performance of the insulation layer and the strength durability of the wall structure,but also increases the risk of mildew on the inner wall.Based on the theory of heat and humidity coupling transfer,the heat and humidity coupling transfer model of one dimension wall with the temperature and relative humidity as the driving force was established.The finite volume method and the additional source term method were used to discretize the control equations and boundary conditions,and the form of the two discrete equations was unified.Then,the program was written in Python language.And the numpy scientific computing framework and TDMA iterative method were used to improve the computational efficiency.The relative error of the program simulation results is less than 5% according to the analytical solution and experimental data in the literatures.Taking the Nanjing area as an example,the heat and moisture coupling transfer simulation of the thermal insulation wall under the stable boundary conditions in the hot summer and cold winter area was simulated,and the dew condensation characteristics of the thermal insulation wall were obtained.In hot summer and cold winter area,the condensation is easy to occur inside the external thermal insulation wall under the summer condition,and the moisture accumulation is easy to occur inside the internal thermal insulation wall under the winter condition.Moreover,the greater the difference in moisture resistance between the thermal-insulating material and the base material of wall,the faster the moisture accumulating rate occurs when the wall undergoes a wet accumulation phenomenon.Through the simulation of heat and moisture transfer of the thermal insulation wall under the typical meteorological year,it is found that the thermal insulation layer and the inner wall of the internal and external insulation wall have different condensation risks under the dynamic conditions.Subsequently,based on the dew condensation characteristics of the thermal insulation wall,the suitable locations for the air layer and vapor barriers layer were obtained.Through the simulation analysis of each condition of the four thermal insulation walls with anticondensation measures,the dynamic anti-condensation effect was obtained.The humidity-controlled active anti-condensation measure can regulate the humidity at the inner surface of the thermal insulation wall.It can control the relative humidity at the inner surface of the wall in the range of 50%~55%,and effectively prevent the mildew at surface of the wall;In addition,it can also reduce the relative humidity inside the thermal insulation layer of the internal thermal insulation wall to prevent condensation inside the thermal insulation layer.The three kinds of passive anti-condensation measures,such as thermal insulation material with large moisture resistance,air layer and vapor barrier layer,can regulate the relative humidity of the thermal insulation layer and reduce the condensation time of the thermal insulation layer in the whole year.Under the six kinds of simulated conditions,the XPS insulation material can reduce the condensation time of 938 h,584h,56 h,44h,197 h,and 81 h inside the insulation layer of the external insulation wall,respectively.And the air layer can reduce the time of 396 h,179h,50 h,38h,196 h,77h.In addition,the vapor barrier layer can adjust the relative humidity of the thermal insulation layer within the range of 45% to 60%.Among three kinds of passive anti-condensation measures,the dynamic anti-condensation effect of the vapor barrier layer is the best,the thermal insulation material with the large moisture resistance is the next,and the air layer is the weakest.