Study on Formula for Predicting Convective Heat Transfer Coefficient in Urban Canopy Layer Taken Account of Atmospheric Stability

Abstract

Complex heat transfer fluxes occur between external surfaces of building walls and the urban canopy layer on typical summer days. The convective heat transfer coefficient on urban surfaces is an essential index that indicates roughly the characteristics of sensible heat fluxes inside the canopy layer. An experiment was conducted to obtain a formula for predicting convective heat transfer coefficients. The radiative heat transfer was calculated by Gebhart's absorption factor method. The heat transfer coefficients over a rough floor in the velocity range from 0.5 m/s to 2.0 m/s were larger than those over a smooth floor. An experimental formula for the heat transfer coefficients with a function of reference velocity and bulk Richardson number was derived by a nonlinear regression model. Experiments must be carried out to accumulate data and obtain high quality prediction formulas.