A new evaluation index for indoor hot environment in naturally ventilated building with hot surface

Indoor wet-bulb globe temperature (WBGT) was extensively used to evaluate the indoor hot environment in a naturally ventilated building, but it does not consider the effect of air movement caused by the hot surface. A potential evaluation index, which is a difference between the mean radiant temperature and the air temperature (Δtr–a), was introduced to be integrated with the indoor WBGT to evaluate the indoor hot environment with hot surface. Subjective evaluation of the occupant's thermal perceptions and objective measurement of indoor physical parameters were carried out in a typical naturally ventilated room with hot surface ranged from 50°C to 250°C. The results show that the indoor air temperature, mean radiant temperature and WBGT were increased by 8.6°C–12.9°C, 11.2°C–29.7°C and 4.7°C–7.5°C, respectively, with participant's light activity, and by 9.9°C–13.5°C, 14.9°C–29.4°C and 5.7°C–8.0°C, respectively, with participant's heavy activity. Indoor air temperature was increased linearly with the indoor WBGT, whereas the mean radiant temperature was increased non-linearly with the indoor WBGT. Besides, the non-linear relationship between the occupant's thermal perceptions and Δtr−a coincided very well with those between occupant's thermal perceptions and indoor WBGT. This suggests that the Δtr–a may be a potential index to be integrated with the indoor WBGT for evaluating the indoor hot environment in naturally ventilated building with hot surface.