ANALYSIS OF AIR AND WATER SPRAY INTERACTION

Abstract

In this study, we present energy and exergy analysis of mono and multi droplets shower cooling tower (SCT) for two-dimension (2-D) MATLAB mathematical model and three dimensional (3-D) Computational Fluid Dynamics (CFD) model for parallel flow and counter flow arrangements. SCT operated without fill because salt decomposition on the fill performance of conventional cooling tower leads to deteriorate. In MATLAB model mass, momentum, energy, exergy and droplet trajectory equations are solved simultaneously for predicting the exit conditions of water and air. 3-D CFD model has also been used for predicting the exit condition of water and air. The low temperature exit water is required for industrial application to cool condenser in industries, and low temperature exit air can be used for air cooling application for producing comfortable atmosphere indoors in India and other parts of the world. Mono and multi droplet diameters model were used to study 2-D MATLAB model and 3-D CFD model. Experimental data obtained from SCT are used to validate mono and multi droplets MATLAB and CFD models. Mono droplet model has uniform Sauter mean diameter (SMD), and multi droplet model has ten different diameters water droplets for the study. Rosin Rammler distribution is used to distribute ten different diameter droplets in multi droplet model. Parametric study of industrial and air cooling application of SCT are based on the variation of Inlet droplet diameters, water temperature, air DBT, air relative humidity, and water to air mass flow ratio (RLG). The variation in inlet parameters shows significant changes in exit air DBT, air specific humidity, water temperature, thermal efficiency, air convective exergy, evaporative air exergy, total exergy of air, water exergy, total exergy of the system, exergy destruction and second law efficiency (SLE). The results show the thermal efficiency of parallel and counter flow mono and multi droplet SCT decreases with increase in the inlet droplet diameters and RLG, and SCT thermal efficiency increases with increase in the inlet air DBT and air relative humidity. The results also show the model of cooling tower system produces the entropy. Therefore the amount of total exergy absorbed by air is less than exergy supplied by water. SLE of parallel and counter flow mono and multi droplet SCT decreases with increase in the inlet water temperature and air relative humidity, and SLE of SCT increases with increase in the inlet droplet diameter, air DBT and RLG. Parameters of air and water become asymptotic up to 0.5 m height of the parallel flow SCT, so the optimum height of tower should be 0.5 m for same operating conditions. Thus by reducing tower height investment cost can also be reduced.