Numerical Simulation Of Heat And Moisture Transfer Of Walls And Optimization Of Structural Schemes

Building energy consumption accounts for a very high proportion of total energy consumption.Coupled heat and moisture migration of the building wall has a great influence on the insulation performance and the mould germination.There is no central heating in mild areas,and the indoor thermal environment is poor.In winter,people use heating equipment by themselves more and more.Use heating equipment not only increases the risk of mold growth,but also leads to a sharp increase in building energy consumption.From the knowledge above,based on the coupled heat and moisture migration model of porous media,this paper conducts research on the heat and moisture migration characteristics of building walls in Kunming and the risk of mold growth,which is of great significance for optimizing the wall insulation performance and reducing the risk of mold growth.The main contents of the present research are listed as follows:First,this paper take temperature gradient and relative humidity gradient as driving potential,establish a mathematical model of coupled heat and moisture migration in building walls.Then,use the multi-physics simulation software COMSOL to solve mathematical models and simulate classic cases,verify the scientificity of the COMSOL software to solve the mathematical model of coupled heat and moisture migration in the wall by comparing the calculated results with the experimental data.Secondly,based on the conclusions from previous chapters,under different working conditions,numerical simulation was done,distribution of temperature and humidity inside the wall was analyzed,the risk of condensation on internal insulation walls was evaluated.Thermal and moisture performance of the wall under different solar radiation intensity,indoor temperature,and insulation thickness is studied.Results show that it took about 5 hours for the heat from the solar radiation to travel from the outer wall to the inner wall;indoor heating equipment can cause the overall temperature of the wall to rise by 3 ℃-5 ℃;insulation layer can reduce the temperature fluctuation of the inner wall from 0.5 ℃ to 0.1 ℃,the 40 mm insulation layer can make the wall have better insulation and moisture insulation performance,and the performance improvement of increasing the thickness of the insulation layer is not obvious;non-extremely humid environment,there is no risk of condensation on the building walls.Then,based on the mould germination risk evaluation model,the mould germination risk of typical walls under different solar radiation intensities,indoor relative humidity,and growth substrates is studied.Results show that the risk of mould growth on walls without direct sunlight was 10 times that of walls with direct sunlight;regardless of whether there is direct sun exposure,the value on the inner surface of the wall is 2%-3% higher than the interface;controlling the relative humidity in the air at 80%can effectively inhibit the growth of moulds;if the relative humidity in the air is controlled below 78%,there will be no risk of mould growth;the temperature and humidity conditions in Kunming were not conducive to the growth of harmful moulds.Last,this paper takes building load,wall economy per unit area,and the mould germination as three optimization index,building optimization model of wall structure based on AHP-TOPSIS.And through this model,from five alternative wall structure schemes,it is calculated that the fly ash self-insulating block wall is a relatively good wall structure.