Research On Coupled Heat And Moisture Transfer Mechanism Of Porous Media For Thermal Insulation Materials

Energy,environment and sustainable development are the themes of the survival and development of human society in the 21 st century.Among them,sustainable development is the center and energy and environment are the guarantee and foundation.In recent years,with the rapid development of China's national economy,the acceleration of urbanization and the transformation of modern lifestyle,energy consumption has increased year by year,and the contradiction between supply and demand has intensified.People pay more attention to energy conservation.The application of thermal insulation materials in building envelope structure and heating and air-conditioning greatly reduces building energy consumption and improves people's quality of life,it has become an industry encouraged and supported by national policies.However,in the use of thermal insulation materials,the influence of moisture is inevitable.It will not only reduce the thermal insulation performance of thermal insulation materials,but also shorten the service life,and even cause damage to the building environment and human health.In order to explore the transfer mechanism of moisture and heat in thermal insulation materials and put forward corresponding moisture-proof measures,it is necessary to study the coupled heat and moisture transfer mechanism of porous media for thermal insulation materials,which has important theoretical and practical significance.In this paper,taking the representative macroscopic volume of thermal insulation materials as the research object,when moisture content is contained in porous media,the parallel model of heat-moisture coupling transfer in black box,the series model of heat-moisture coupling transfer in black box,the model of heat-moisture coupling transfer in grey box and the model of heat-moisture coupling transfer in white box are established,the process of heat and moisture transfer reflecting from roughness to precision,and the formulas of thermal conductivity and moisture conductivity corresponding to each model are derived.According to the structural characteristics of porous media,the mechanism of coupled heat and moisture transfer in porous media is analyzed,and the mathematical model of coupled heat and moisture transfer is established with temperature gradient and vapor pressure gradient as driving forces.Taking rock wool as an example,the influence factors of thermal conductivity of thermal insulation materials are studied by numerical calculation.The results show that the larger the porosity and pore channel distribution coefficient are,the smaller the thermal conductivity is,and the smaller the moisture content,water content and tortuosity are,the smaller the thermal conductivity is.Taking glass wool felt as an example,the accuracy of the formulas for calculating the thermal conductivity of the four coupled heat and moisture transfer models is verified by comparing the data obtained from the thermal conductivity measurement experiments with the simulation results,showing that the formulas given in this paper can be used for calculating the thermal conductivity of thermal insulation materials.The research results of this paper can simply analyze the heat and moisture transfer process of humid insulation materials,effectively obtain the thermal conductivity and moisture conductivity.It has certain reference value in theoretical research and engineering practice,and puts forward new suggestions for the study of heat and mass transfer in porous media.