Employing the spray system to improve the regional thermal environment in outdoor open space

Rapid urbanization has led to a significant urban heat island effect . When the spray cooling system is applied to outdoor public space, it is helpful to improve the microclimate . While a reasonable spray system is an important guarantee to improve the thermal comfort of the human body in the spray space. In this study, the combination of experimental measurement and questionnaire survey was used to explore the thermal comfort index suitable for evaluating natural and spray space to modify the heat stress scale. The accuracy of thermal sensation prediction based on the original thermal comfort index and the corresponding heat stress scale was compared between the two methods of thermal sensation regression and thermal unacceptable percentage prediction. A heat stress scale based on natural and spray space in Qingdao was proposed. The results showed that compared with direct exposure to sunlight, the spray space could effectively improve thermal sensation (−1.07) and thermal comfort (+0.80), and inhibit the rate of skin temperature rise (+0.553 ∼ −0.155 °C/min). The thermal unacceptable percentage method can be used to predict the thermal sensation in the natural space, and the prediction rate (88 %) of the universal thermal climate index (UTCI) was the highest. The thermal sensation regression method can be used to predict the thermal sensation in the spray space, and the standard effective temperature (SET ⁎ ) prediction rate (60 %) was the highest. In the assessment of outdoor thermal risk, when the UTCI exceeded 38 °C in Qingdao, the heat risk reached the range of strong heat stress, and it was necessary to start the spray device to improve the thermal environment . When the SET ⁎ in the spray space exceeded 41 °C, the spray still cannot improve the thermal health status, and it was recommended to reduce outdoor activities. • The thermal response of human body in the spray was studied. • The heat stress scale in the spray was corrected. • The applicable thermal comfort index in the spray was explored. • Two thermal sensation prediction methods were compared.