Experimental evaluation of a water spray system for semi-outdoor spaces: Analysis of the effect of the operational parameters

As a consequence of climate change, urban overheating has increased in all the cities of the world during the last decades. It is therefore paramount to counteract such effect by promoting the use of effective solutions to mitigate overheating at a micro-scale level. In this work, a modular experimental setup based on a water spray system was designed, realized and tested to evaluate its thermohygrometric performance in semi-outdoor spaces such as bus/train/taxi stops, street resting stations and corner shops. The setup allows to vary three operational parameters: (a) the height of the nozzles from the ground; (b) the presence of an upper shielding to reduce the impact of solar radiation; (c) the presence of a side shielding to reduce the impact of wind speed. The combination of the operational parameters allowed to evaluate the performance of five configurations for the water spray system. Several performance indexes were calculated to assess the impact of each operational parameter. It was found that the best configuration guarantees a −20% reduction of dry-bulb temperature, and the minimum specific water and electricity consumptions of the system are 0.020 L/m2 and 0.150 Wh/m2, respectively. Also, the presence of the side shielding is the parameter that mostly influences the performance of the system, followed by the height of the nozzles, while the presence of the upper shielding has a minor effect. These operational parameters, however, increase relative humidity inside the nebulization volume; it is therefore important to verify if undesired wet conditions are reached.