Experimental and theoretical studies on air humidification by a water spray at elevated pressure

Humidification of compressed air is important for humid air turbine cycle. In this paper, theoretical and experimental investigations are carried out to analyze and predict the humidification process in spray tower. For predicting the heat and mass transfer in the water droplet–air two-phase flow, a one-dimensional numerical model simulating the conservation of heat and mass of water and humid air was developed. The model considers the effect of droplet motion on the heat and mass transfer. Experimental data were obtained on a pressurized model spray tower at different pressures and water/air ratios, which had been adopted to validate the numerical model. Droplet diameter of the spray was measured and these data were used in the model. Predictions of outlet conditions of air and water for giving input conditions agree well with experimental data, which produces a maximal error of 7.3%. On the basis of the model, distributions of droplet velocity and volumetric heat transfer coefficient over height of the tower are predicted. The effect of droplet diameter on the characteristic performance of spray humidifier is also analyzed in the simulation.