Study On Heat And Mass Transfer Of Insulation Materials Porous Media Based On Three Boxes Model

Insulation materials are widely used in many areas of aerospace, thermal equipment, architectural decoration, home appliances and other production and life.As a typical porous media, heat and mass transfer process are complex. Currently,there are some limitations in method analysis, model analysis and experiment analysis.This paper establish two types of heat and mass transfer “three boxes” model of insulation materials porous media based on representative macroscopic volume,namely: the first “three boxes” model and the second “three boxes” model.The first“three boxes” model include: the first black box model, the first gray box model and the first white box model. The second "three boxes" model include: the second black box model, the second gray box model and the second white box model. Then,establish the heat transfer model for each model based on six kinds of models, the mathematical models for calculating thermal conductivity are derived under different kinds of heat transfer models.The thermal conductivity which over heating dry air in the state of 101.325 kPa and 70°C transfers glass wool representative macroscopic volume is calculated.Analyze the relationship with porosity, pore channels distribution coefficient, average tortuosity, pore channels slope and thermal conductivity. Obtain four important conclusions: thermal conductivity decreases with increasing porosity, thermal conductivity increases with increasing average tortuosity, thermal conductivity increases with increasing pore channels distribution coefficient, thermal conductivity increases with increasing pore channels slope.Independently developed a set of insulation materials thermal conductivity testing device, thermal conductivity testing laboratories were conducted based on the porosity of 35% glass wool. Comparative analysis experimental data and theoretical data, the error meets engineering standard. The “three boxes” model can be directly used to analyze heat and mass transfer problems and calculate thermal conductivity in porous media.The research results provide references for insulation materials and other materials porous media in momentum, energy and quality transfer mechanisms. At the same time, it has a scientific significance in production process of insulation materials.