Controlled airflow fluctuations for improved performance of mist cooling systems: Enhanced evaporation and thermal comfort

Abstract

Rising global temperatures and resulting heat stress on people necessitate sustainable outdoor cooling solutions. Mist cooling offers promise, and this work proposes a novel approach: incorporating fluctuating airflows into misting systems. We hypothesize that mist-cooled fluctuating airflows could provide more efficient outdoor cooling for people, for two reasons: 1) Increased turbulence and mixing promoting higher water evaporation rates; 2) dynamic airflow leveraging transient thermal perception for improved comfort.

Wind tunnel experiments and numerical simulations support this hypothesis, revealing that fluctuating flow, compared to constant flow with the same average velocity, enhances evaporation. Lower frequencies, higher amplitudes, and profiles with steeper gradients led to higher evaporation rates. These findings assume an idealized domain, excluding natural wind patterns. Furthermore, predictions confirmed that fluctuating flows consistently provide superior thermal comfort compared to constant flows. Fluctuating airflow with misting achieved equivalent comfort at 38% lower energy consumption compared to fluctuating flow without misting and 81% lower compared to constant flow with misting. The proposed technology has the potential to improve outdoor comfort and decrease resource consumption. It is scalable, not complex, and can be implemented into existing systems, though it may face challenges such as increased wear on fan components.