Numerical Simulation Of The Indoor Thermal Environment And Thermal Insulation Characteristic Of Lightweight Roof

Traditional houses are mainly lightweight roof who is poor thermal insulation characteristic, the outer surface temperature of the roof in some areas is as high as 70 degree Celsius, and the inner surface temperature of the roof is very high. The radiation of inner surface of the roof on the human body accounts for a large part, and affects seriously people’s thermal comfort. Therefore, improving the performance of roof insulation and ventilation, to improve the ability to resist outdoor heat in summer is particularly important, but also can reduce air conditioning energy consumption, improve indoor thermal environment. In this paper, author analyzes roofing heat insulation performance and the indoor thermal environment by the numerical simulation method to improve the heat insulation performance of existing traditional dwellings, achieve the goal of energy saving and meet the requirements of thermal comfort of people.In the state of natural ventilation, the indoor air and roof is coupled heat transfer process. The temperature of roof and indoor air is varies with the change of outdoor air temperature and the solar radiation. In this paper, author builds a three-dimensional physical and mathematical model of the lightweight roof and indoor air-coupled heat transfer, through numerical simulation approach to analyze the impact of roof insulation, insulation thickness, indoor wind speed, the absorption coefficient of the outer surface of the roof, night ventilation and roof ventilation to thermal insulation properties and indoor thermal environment of the roof. Firstly, thermo-insulation roof not only can improve the indoor thermal environment, but also can play attenuation and delay effects to the outdoor temperature. With the increase of the insulation thickness, the thermal insulation characteristic of roof to delay and attenuation degree of outdoor temperature is gradually weakened. When the insulation thickness increases to about 200 mm, temperature fluctuations at inside surface of the roof hardly changes. Insulation thickness of 100 mm is quite reasonable. Secondly, considering the wind speed had certain influence on indoor thermal comfort, the paper analyses the indoor wind speed on the improvement of the indoor thermal environment, the analysis shows that indoor wind speed increases help reduce the internal surface temperatures of roof,but the indoor wind speed increases leads to the outdoor hot air into the room, a comprehensive analysis shows that indoor air is the best controlled at 1m / s or less, increasing indoor wind speed do not replace the roof insulation for improving thermal comfort. Heat-reflective roofing can significantly improve indoor thermal environment, is an economical and convenient measures.Due to indoor air temperature of the thermal insulation roofing appears statified phenomenon. To further study the performance of lightweight roofing insulation and indoor thermal comfort, In this paper, author made a further analysis on roof ventilation, the result shows that roof ventilation can eliminate the phenomenon of the temperature stratification in the building, the ratio of roof opening equal to 0.01 is reasonable, too large ratio can’t improve indoor thermal environment. Finally, analysis showed that roof insulation with the ventilation enables better insulation performance.