Numerical study on the performance of a two-nozzle spray cooling system under different conditions

Abstract

The cooling performance of natural draft dry cooling towers (NDDCTs) would significantly be reduced when the ambient air is hot. To address this problem, the spray pre-cooling technology has been introduced to cool the inlet air of the tower. The effect of two-nozzle distance on the evaporative cooling performance will instruct the arrangement of multi-nozzle for industrial applications. This paper is therefore to study two nozzles vertically arranged in a wind tunnel by the numerical simulation. A 3-D model was developed and validated for simulation studies. The effects of two-nozzle distance, inlet air speed, inlet air dry-bulb temperature and humidity on the evaporative cooling performance were investigated. Besides, a modified cooling efficiency was proposed to effectively evaluate the cooling performance with considering both the cooling affected region and the air temperature drop. The simulation results indicate that the modified cooling efficiency is more or less affected by the two cooling affected regions generated by two nozzles at the wind tunnel exit. The modified cooling efficiency of the tangent region is similar to that of the separating region, and it is 2.5% higher than the partially overlapping region. Generally, the high modified cooling efficiency is accompanied with the high air dry-bulb temperature and the low humidity. The modified cooling efficiency increases with the decreasing inlet air speed.