Research On Thermal Performance Of Prefabricated Aerated Concrete Composite Insulation Exterior Wall Panel

The outer wall is the outer envelope structure with the largest contact area between the building and the outdoor environment,and it is also the part with the largest heat transfer and heat consumption in all envelope structures.The quality of its thermal insulation performance has a great impact on the energy consumption of the building.For the exterior walls of prefabricated buildings,whether the design of the joint thermal bridges and structural thermal bridges of the external wall panels is reasonable is also an important factor that affects whether the new wall panels can be promoted and used.This paper focuses on the thermal performance of a new type of composite thermal insulation external wall panel proposed by the research group.The main work is as follows:(1)Research on the thermal conductivity of the base plate aerated concrete slab of the composite thermal insulation exterior wall panel.The effect of steel connectors and different reinforcement numbers and diameters on the thermal conductivity of the aerated concrete slab is analyzed by numerical simulation calculation method.,The results show that the thermal bridge effect of steel connectors is obvious;according to the simulation results,when the number of aerated concrete slabs is 4 on-line and the number of reinforcement is 4,the thermal conductivity correction coefficient is recommended to be 1.10,and the number of on-line and down-web reinforcements is each It is recommended to take 1.15 when there are 6 roots.(2)Taking the aerated concrete slab with a thickness of 150 mm,4 longitudinal reinforcements and a reinforcement diameter of 8mm as the research object,the numerical simulation method is used to analyze the influence of the thickness of the steel protective layer and the material of the end tie bars on the thermal conductivity of the aerated concrete slab.The results show that when the thickness of the protective layer increases from 20 mm to 30 mm,the heat transfer and equivalent thermal conductivity of the model decrease.The analysis is due to the increase in the thickness of the protective layer,which reduces the length of the tie bars at the end and increases the heat at the same time.The thermal resistance transferred along the length of the end tie ribs.In addition,after changing the material of the end tie bars from steel to FRP,the heat transfer and equivalent thermal conductivity of the aerated concrete slab are further reduced.(3)In order to determine the correction coefficient of the type I composite wallboard insulation in the thermal design calculation,the steady-state heat transfer simulation analysis was carried out on the type I wallboard insulation with different insulation materials and insulation thickness,and it was found that the same kind of insulation The correction coefficient of the material has nothing to do with the thickness of the insulation layer,but is related to the proportion of the wallboard area occupied by the slurry protective layer(ie wallboard specifications);from SEPS,XPS,SXPS to PU,the thermal conductivity of the insulation material gradually decreases,but The correction coefficient gradually increases,indicating that the smaller the thermal conductivity of the insulation material,the greater the equivalent thermal conductivity is affected by the thermal bridge effect of the slurry protective layer.The influence of type I wallboard specifications on the correction coefficient of the insulation layer is analyzed by theoretical calculation.The results show that the smaller the type I wallboard specifications,the greater the correction coefficient.When the wallboard height is more than 3m,the correction coefficient tends to be stable.The height of wallboards commonly used in residential and public buildings is3 m and above.Therefore,the correction coefficients of the four thermal insulation materials in the thermal design calculation of type I composite panels are determined as: SEPS: 1.17,XPS: 1.19,SXPS: 1.22,PU: 1.29.(4)In order to study the effect of joint thermal bridge on the insulation performance of the wall,the steady-state heat transfer of the wall panel indirect joint thermal bridge and the wall panel and the beam and column joint thermal bridge were simulated,and the results showed that the wall panel indirect joints The internal surface temperature of the joints between the wallboard and the beams and columns is higher than the dew point temperature,and the insulation measures for the wallboard joints are designed reasonably.At the same time,the effect of the filling depth of polyurethane foam at the joints of the wall panels on the heat transfer of the joint thermal bridge was simulated,and the results showed that different filling depths of the polyurethane foam had less influence on the heat transfer at the joints of the wall panels,which was more effective in satisfying the external requirements.Under the premise of waterproofing the wall,the filling depth of the panel joint polyurethane foam can be reduced to reduce the cost.(5)In order to study the influence of the structural thermal bridge on the insulation performance of the wall,the heat transfer simulation analysis of the structural thermal bridge of the built-in external wall corner was carried out,and the results showed that the external corner of the steel structure and the internal corner of the reinforced concrete structure The surface temperature is higher than the dew point temperature,and the heat preservation treatment of the thermal bridge is reasonable.At the same time,in order to reduce the construction cost,reduce the rock wool insulation treatment measures at the steel beams and steel columns of the outer wall of the steel structure,and conduct a heat transfer simulation analysis.The results show that the inner surface temperature of the outer wall corner is still higher than the dew point temperature after the rock wool is removed.