Dry mist systems and its impact on thermal comfort for the tropics

Abstract

Tropical countries, like Singapore, are hot and humid throughout the year. Coupled with the Urban Heat Island effect from rapid urbanisation, Singapore has seen a long-term increase in annual average temperatures over the years. One solution is the use of misting systems that tap on the principle of latent heat of vaporisation to provide cooling. This paper specifically addresses the use of air-assisted "Dry Mist" systems, where the sprays are of ultra-fine droplet size, measured using PIV system in this study, and do not cause a wet sensation upon contact. This study has found that suitable operation conditions are during hot afternoons where Relative Humidity is lower, between 50–65%. Through both objective and subjective measurements, it was found that wind velocities above 0.58 m/s and Solar Irradiances above 571 W/m2 are the limits for operation. The subjective measurements also found majority of the participants feeling colder from the system, and despite a slight increase in skin wetness, there is also increase in wet feeling pleasantness. A statistical analysis also found that changes in Thermal Sensation Vote (TSV) is most significantly captured by changes in skin temperatures and wet feeling pleasantness vote, while changes in Thermal Comfort Vote (TCV) is most significantly captured by changes in Tmrt and Air Humidity Vote.