Temporal variation of wall flow and its influences on energy balance of the building wall

Abstract

The characteristics of energy balance and heat transfer on building walls are important for building energy consumption and outdoor thermal/wind environment. The in-situ measurement of energy balance and wall flows during clear days on a 16-story building in Guangzhou, China is introduced and analyzed in this paper. The velocity along the wall was measured by 3D ultrasonic anemometers. The surface temperature was measured by infrared camera and thermal couples. The ambient temperature, relative humidity, wind velocity and solar radiation were recorded by weather stations. The Rayleigh number of wall flows reached as high as 1.44 × 1014. We found that the different kinds of heat flux reach their maximum value in a day cycle at different times. The transmittance of the atmosphere keeps decreasing from sunrise to sunset on Guangzhou’s typical clear days thus inducing different incoming solar radiation. The wall surface temperature and air flow were visualized by infrared videos. The diurnal change of energy balance on the south facing wall was calculated based on the solar radiation, long wave radiation and heat transfer caused by natural convection adjacent to the wall.