Experimental investigation of water spraying in an indirect evaporative cooler from nozzle type and spray strategy perspectives

Abstract

Indirect evaporative cooling is a refrigerant-free and low-energy-consumed cooling technology. In practical cases, degraded cooling efficiency of indirect evaporative coolers (IEC) can be observed owning to poor wettability of the wet channels. Although many efforts had been made to improve the unevenly distribution of water film inside an IEC, existing research focus on developing novel materials for better diffusion and optimizing the nozzle arrangement. The influences of nozzle types and water spray strategy (continuous or intermittent) on water distribution performance had seldom been discussed. In this study, the IEC is experimentally investigated from the point of water spraying. Firstly, the water distribution performance of five commonly used spray nozzles has been quantitatively investigated by three proposed indicators (coverage ratio, uniformity coefficient and water volume in distribution regions) under different water rate. Secondly, the optimal nozzles are selected to be used in an advanced porous IEC prototype with good water storage and diffusion characters, which can facilitate the intermittent spray strategy. A series of intermittent spray strategies were tested to recommend a combination of spraying period and intermittent period for higher wet-bulb efficiency and less water consumption. The results show that the spiral type nozzle is the optimal for IEC application because of its high coverage ratio, good uniformity and acceptable water volume in the distribution area. The recommended intermittent spray strategy for porous ceramic IEC is a combination of 10 s–12 s spraying period and 1 min intermittent period.