Computational Fluid Dynamics simulations to evaluate the performance improvement for Air-cooler equipped with a water spray system.

Air cooler heat exchangers are devices widely used in industrial applications to cool a process fluid. Most plants are built in arid areas with high air temperature but limited water resources. Therefore, in the hottest periods, a considerable air-cooler performance decrease occurs. Evaporative cooling by water spray, to cool the inlet air, is increasingly used as an efficient approach to enhance the air-cooler performance. This paper presents the study of the effect of evaporative cooling provided by the use of a water spray system. It has been developed through numerical simulation with Computational Thermo-fluid Dynamics that can be an effective tool for the performance evaluation of such system. CFD simulations easily allow parametric studies for the evaluation of alternative design configurations, especially when the different configurations are all embedded within the same computational domain and grid. In the vast majority of these studies the Lagrangian-Eulerian (LE) approach has been used, with the continuous phase (air in this study) represented in a Eulerian reference frame while the discrete phase (water droplets in this study) in a Lagrangian reference frame. This study, in particular, focuses on the effect of droplet size, nozzle arrangement and air velocity on performance of air-cooler. This knowledge is crucial for designing efficient spray cooling systems. Due to a number of reasons, which include water consumption restriction and the regulation of plant, spray cooling systems are becoming the preferred choice for many power plants because they can be applied in existing plants, and this is an enormous economic saving. In this way, it is possible to enhance the performance in high ambient air temperature without high costs.