Thermal comfort improvement in urban spaces with water spray systems: Field measurements and survey

Abstract

An experimental study was conducted to improve the comfort and liveability of urban open spaces during the hottest months of the summer by implementing an overhead water mist cooling system. The campaign was conducted in two different Italian urbanscapes (Ancona and Rome, representative of Cfa and Csa climates) one after the other.Monitoring data and comfort questionnaires were combined to extract useful information by means of statistical tests, regressions and data mining algorithms and, ultimately, to delineate design and operating guidelines to maximize people's satisfaction with the misted environment.The cloud of droplets reduced the temperature and the UTCI by 8.2 °C and 7.9 °C respectively, against a 7% mean humidity premium. The vertical cooling and humidification profiles obeyed a Lorentzian distribution, peaking within approximately 0.5 m of the injection. The severe overheating experienced outside of the cooled areas evanished under the spray, with 67% (Ancona) to 90.6% (Rome) of respondents reporting only slight bending from thermal neutrality. Perception and preferences towards solar radiation, humidity level and wind all improved within the droplets mist.In terms of comfort-oriented, optimized design criteria, the system proved to work best with a dominant and steady light breeze (1–2 m/s), in highly irradiated sites and suspended at 1.2–1.5 m above the average height of users.