Abstract:
This study describes three-dimensional computational fluid dynamics CFD simulations of air flow and water droplets through a fin fan cooler assisted with direct evaporative cooling through misting; and proposes an optimized sizing of nozzles resulting in an optimized evaporation process that corresponds to air stream with uniform temperature below or equal to a desired value. The system being studied is a fin fan cooler FFC used in a refinery to cool down a process fluid by forced convection. When the ambient temperature exceeds 34.5 °C, water mist is sprayed into air through 238-uniformly distributed nozzles. Due to high enthalpy of vaporization of water, heat will be extracted from air and hence its temperature is decreased before reaching the tube bundle level. The non-uniform air profile with the current distribution of nozzles is causing non uniform cooling, and hence non uniform temperature profile of air which may result in the lack of performance for the entire process. CFD simulations are run to optimize air temperature just before the tube bundle level by controlling vaporization through proper sizing of nozzles that results in different flow rates of water mist across different nozzles. The location of nozzles was not changed, the size of 14 nozzle in chosen locations was decreased and the size of 11 nozzles at chosen location was increased. The total flow rate of water was preserved. The baseline simulation results showed that temperature reached 34.5 °C in tubes bundle region, but air temperature was not uniform. The optimized sizing plan resulted in uniform air temperature below or equal to 34.5 °C in tubes bundle region.
