Study of a fogging system using a computational fluid dynamics simulation

Abstract

Fogging is one of the most effective methods for lowering the air temperature in rooms and greenhouses. It also has many industrial applications, especially in gas turbines where this method presents great advantages over others in terms of achieving better turbine performance in hot weather conditions.With this in mind, a numerical study was performed in STAR-CCM+ to investigate mist dynamics at a turbine's inlet duct, specifically measuring: (i) residence time of water droplets; (ii) mass transfer between water and air; (iii) coalescence and agglomeration of the water droplets; and (iv) changes in air density and temperature inside the duct. The results were compared against the same variables taken from experimental wind tunnel data and found to be similar with respect to the behavior of temperature and relative humidity.Therefore, it was possible to conclude that the results obtained in the simulation were close to those reported experimentally with differences from 3 to 6%. Based on the profiles and contour graphs obtained, it was also found that the best mass and energy transfer occurs when an atomizing diameter of 20 µm is used with the lowest relative humidity possible. Working with this humidity and droplet diameter, it is possible to avoid water runoff on duct walls.