Quantifying the effect of ground view factor and ground temperature on outdoor mean radiant temperature

Abstract

• The MRT difference can result from human heights and radiant ground area. • The MRT is clearly influenced by ground temperature. • The ground temperature near an individual has a noticeable effect on the MRT. • Averaging the non-uniform ground temperature may result in an MRT overestimation. The outdoor mean radiant temperature (MRT) is greatly affected by ground radiation related to ground view factor ( F g-p ) and ground temperature ( T g ). However, the effects of F g-p and T g on the MRT are frequently oversimplified and have rarely been quantified. Therefore, this study aims to quantify the effects of F g-p and T g on the MRT through microclimate measurement and Monte Carlo ray-tracing simulations. The results suggest that during summers in Shanghai, the effect of F g-p difference resulting from various human heights on the MRT can be ignored among 70–230-cm-tall individuals when the distance ( L ) between the edge of the radiant ground area and human body is greater than 40 m. Moreover, the effect of the F g-p difference resulting from various radiant ground area can be ignored for an individual shorter than 230 cm when the L is not less than 70 m. For ground with a uniform temperature, the MRT may decrease by 6.3 ℃ when T g is reduced by 16.4 ℃ in Shanghai summer. For ground with non-uniform temperature, the size of the lower-temperature area has a noticeable effect on the MRT. Moreover, averaging the non-uniform T g may result in an MRT overestimation by 2.5 ℃ for 150–190-cm-tall human bodies.