Experimental and Theoretical Studies on Air Humidification by a Water Spray for Humid Air Turbine Cycle

Abstract

Humidification of compressed air is important for humid air turbine cycle. Earlier studies paid more attention to packed bed towers. However, a spray tower has inherent advantages such as less pressure loss and low cost. In this study, a pressurized model spray tower was established for the experiments. A specially designed air diffuser was installed to achieve uniform air velocity profiles over the cross section and a mist eliminator was used to trap the water droplets in the outlet air. Performance of the tower was tested at different pressures and water/air ratios. Pressure loss was measured and analyzed at different air velocities. A comprehensive analysis of the humidification process in the spray tower was carried out. A mathematical model considering droplet motion and conservation of heat and mass was developed to predict heat and mass transfer in the water droplet-air two-phase flow. Local heat and mass transfer coefficients over height of the tower were calculated. It has been shown that the parameters of outlet air and water can be calculated within a maximal error of 7.3% compared with the experiment results. Droplet size is a main parameter that affects operating performance of the spray tower. It has also been indicated that pressure loss in the spray tower is low and this will benefit its application in HAT.