Study on water spraying distribution to improve the energy recovery performance of indirect evaporative coolers with nozzle arrangement optimization

Abstract

In response to the worldwide call for energy conservation and carbon emission reduction, indirect evaporative cooling as a green and environmentally friendly technology has been extensively researched and developed. In the practical application of this technology, the spray nozzle arrangement results in different wettability factors of the wet channel surface, which accordingly has a significant impact on its cooling efficiency. Existing research has discussed indirect evaporative coolers (IECs) in various external shapes, internal configurations, and materials. However, the IEC performance improvement was rarely analyzed from the perspective of the spray nozzle arrangement. This paper developed and validated a numerical model to predict the spray water density distribution of the solid cone nozzles on the impact surface with uniformly divided square grids. The actual water spray density obtained from this model could then be used to correct the wetting factor in the existing IEC numerical model. The control variable method was applied to compare the effect of inclined angle and distance between the nozzles. According to the uniformity coefficient as well as coverage ratio of the water spray, the optimal arrangement scheme, i.e. the nozzles mounted along the centerline with the distance of 160 mm, was determined. Results showed that a uniform coefficient of 0.74 can be obtained in the optimal distribution of the full cone nozzle. Greater air cooling and dehumidification were achieved by the optimized nozzle arrangement scheme compared with the original single-line arrangement scheme of the nozzles. The coefficient of performance (COP) of the IEC system could be increased by 16% under the same operating conditions when the optimized spray nozzle arrangement was adopted, which indicated the benefit and importance of the IEC spray nozzle arrangement optimization.