Cooling effect of fanned parasol for mitigating outdoor heat stress

Abstract

Using a parasol is a practical strategy to generate a cooling effect for mitigating outdoor heat stress. This study introduces a new type of parasol, i.e., fanned parasol, consisting of a small fan and a portable parasol. The fanned parasol is economically affordable, practically convenient, and effective in mitigating outdoor heat stress. The mechanisms of the enhanced cooling effect of the fanned parasol compared with the ordinary parasol are experimentally investigated. Both the ordinary and fanned parasols experience two stages, the stored cooling energy by the parasols functions during Stage I. The results reveal that the cooling effect is stronger during Stage I than that during Stage II. Compared with the ordinary parasol, the fanned parasol has two mechanisms to enhance the cooling effect, i.e., the direct and indirect fan cooling effects, by overcoming the wind-blocking effect and heat-trapping effect of the ordinary parasol. The fanned parasol directly enhances the cooling effect by 4.3% and 18.9% during Stages I and II respectively and indirectly enhances the cooling effect by 28.0% and 34.8% during Stages I and II respectively. The enhanced cooling effect is dominantly explained by the indirect fan cooling effect by 86.7% and 64.8% during Stages I and II respectively. Therefore, the introduced novel fanned parasol effectively mitigates outdoor heat stress, mainly attributed to its indirect fan cooling effect.