Thermal Calculation And Simulation Analysis Of The Composite Wall Of The North Farm House

Energy resource and environment are the great challenges that every country especially our country is facing with.Building energy conservation is the main approach to solve energy resource.The adoption of wall thermal performance is one of main act for building energy conservation.The investigation on the existing residential area of Northeast China showed that in recent years,new energy-saving wall has been used in rural housing.In the countryside,depending on the position of the insulation material,composite wall is divided into outer insulation wall?sandwich insulation wall and inner insulation wall three kinds.This paper will focus on analyzing the disadvantages and advantages of three kinds of wall,and undertake a comprehensive evaluation using AHP,so that we can select the wall type which fits the requirements of rural house in cold area.In order to make a comprehensive analysis of the composite wall,firstly,the thermal insulation effect of the wall must be determined.The survey results about northeast rural existing residential show that the new energy-saving wall improve the insulation performance of the wall,but there is a phenomenon of mildew on the corner of the wall.According to the experience of building in the city,it is considered that reinforced concrete is filled in these parts and result in the existence of thermal bridge effect.Therefore,in order to analyze the thermal insulation effect of the wall,this paper firstly established the mathematical physical model of the heat transfer and mass transfer of the composite wall,and then the solving method is proposed.Then take the north and south exterior wall of a farm house that located in Jilin Province as the objects of study,testing the thermal performance of the composite wall.The thermal performance of the main part of wall and the bridges around the wall are tested by using heat box method and heat flow meter method,respectively.Test results show that the heat transfer coefficient of the main wall wall and the surrounding thermal bridge is not the same,the heat transfer coefficient of the thermal bridge around the wall is much larger.Based on the theory of fluid mechanics and heat transfer,the proposed model was calculated and analyzed by Fluent.Analysis results show that the insulation material layer of the main wall part of the wall has little effect on the heat transfer process,and has great influence on the heat transfer of the thermal bridge.When the thermal insulation material layer is on the outer surface of the wall,the range of the thermal bridges is smaller and the temperature difference in the same material layer is very small.But when the thermal insulation material layer is on the inner surface and the middle layer of the wall,the temperature difference of the same material layer is very large.The maximum temperature differences in the outer corner thermal bridge and t-wall thermal bridge are 14? and 8?,respectively.Using the analytic hierarchy process to select the external wall heat preservation method in the cold area,According to the calculation results of the wall heat preservation effect and the structural characteristics of three kinds of heat preservation methods,we give a numerical example analysis,which provides a theoretical basis for the comprehensive selection of external wall insulation.