Thermal behavior of buildings with curved roofs as compared with flat roofs

摘要

In this paper, a detailed finite element model dealing with heat transfer through a domed or vaulted roof is suggested based on a three-dimensional heat transfer equation and solar geometry. This model allows a comparison of the thermal behavior of curved and flat roofs in terms of heat flux and daily heat flow through them into an air-conditioned building under different climatic conditions. The results of numerical calculations show that the ratio of daily heat flow through curved roofs to that through flat ones is not affected by the curve radius, thickness and construction material of the roof, but is significantly influenced by the half rim angle θ_o of the roofs and the ambient temperature. Compared to a flat roof, under typical hot dry climatic conditions, the daily heat flow through a domed roof of θ_o = 90° is about 40% higher, whereas the daily heat flow through a south-north oriented and an east-west oriented vault of θ_o = 90° is about 20 and 27% higher, respectively. The reason for this is mainly attributed to the convective heat transfer between the enlarged curved roof and ambient air. However, when θ_o < 50°, heat flux and daily heat flow through a curved roof is close to that through a flat roof. The results also confirm that curved roofs are not suitable for areas with higher air temperature and intense sky diffuse radiation typical of hot humid areas.