Study On Coupled Heat And Moisture Transfer Model Of Multilayer Walls In Hot And Humid Climate

In hot and humid climate of south china, temperature changes frequently. The heat and moisture transfer through wall has an important impact on service life of buildings, energy consumption and indoor environment. Therefore, based on the theory of heat and moisture transfer, the characteristics of coupled heat and moisture transfer are studied in this paper using simulation software. And experiments were conducted to analyzed coupled heat and moisture transfer under actual climatic conditions.First, a model of coupled heat and moisture transfer is established according to Darcy's law, Fick's law, Fourier's law. Using COMSOL Multiphysics simulation software, the effects of parameters of walls on the coupled heat and moisture transfer in porous media are investigated under hot-humid climate. The results show moisture diffusivity and sorption capacity have greater effects on the model at the midpoint of the wall.According to the established model of coupled heat and moisture transfer, three different types of wall are analyzed with and without absorption and desorption processes which consider varying coefficient. The results show that the peak value of the total heat flux with absorption and desorption processes has hysteresis effect. Wall of internal insulation material can reduced sensible heat flux, but can not reduced latent heat flux. So latent heat flux can't be neglected in calculation of building energy consumption.The solutions of the model are studied. Numerical solution is developed. Based on Luikov equation, a time domain recursive algorithm is used to solve the model. The results are compared with the finite difference algorithm. The conclusion shows that this algorithm agreed with the finite difference algorithm, analytical solution and experimental data. It proves that the algorithm can be used to solve coupled heat and moisture transfer model in porous media. There are a little effects on results changing the time step and increasing the sizes of time step can reduce the time of calculating.In order to study heat and moisture transmission characteristics and prove the validity of this model, this experiment based on existing equipment and experimental program builds a test platform and tests temperature and relative humidity under actual climate. The comparison of experimental data with simulation results verifies the correctness of the model.According to the model established before, vapour condensation at inner surface of the wall is analyzed under four kinds of indoor and outdoor conditions by comparing the dew point temperature and temperature of inner surface of the wall.