Modeling Mean Radiant Temperature Distribution in Urban Landscapes Using DART

Outdoor performance of the black globe temperature sensor on a hot and humid tropical region

A crucial variable to evaluate thermal comfort is the mean radiant temperature (T_mrt). In this paper we evaluate the performance of the 150 mm black globe thermometer to provide reliable T_mrt values for outdoor settings in Singapore. Accurate T_mrt values are calculated by the method of integral radiation measurements. Based on these, the mean convection coefficient of the black globe has been re-calibrated. Results show an improvement in the estimation of T_mrt with the new coefficient in comparison with the default version suggested in ISO7726:1998. Increasing the averaging periods of the measured variables improved the performance of the derived mean convective coefficients to estimate T_mrt. During clear skies day and for 10-min averaged data, RMSE for T_mrt reduce to 3.9 °C (7.4 °C for ISO7726:1998 coefficient) with an overestimation on high incoming solar radiation periods and an underestimation during the morning and evening (low solar elevation). During overcast dry conditions an underestimation of T_mrt is also expected which is higher in the rain/wet periods. The mean convective coefficient presented in this work can provide improved estimations of Tmrt relevant for outdoor thermal comfort studies in hot and humid tropical climates like Singapore.