Analysis of air humidification process for humid air turbine cycle with a detailed air humidifier model

Abstract

Humid Air Turbine (HAT) cycle is one of the most efficient humidified gas turbine cycle that shows the potential to be competitive with combined cycle The humidifier is the distinctive component of the HAT cycle, and the air humidification process is of significance for the overall performance. However, due to the lack of reliable mass transfer coefficient, the existing theoretical model of the humidifier cannot reflect the actual humidification process. This work focuses on a method to estimate the heat transfer coefficient for the humidification process based on experimental data. The global and local mass transfer coefficients are obtained, respectively. The results show that the segmented simulation with the local mass transfer coefficients (SL-2) is significantly better than the overall simulation with the global mass transfer coefficients (SL-1). The mass transfer coefficient (hD) distributed along the height of the humidifier is obtained. At the bottom and the top of the humidifier, the sensible heat transfer and the latent heat transfer dominates the air humidification, respectively. In the packing segment of the humidifier, the heat transfer has low effectiveness of 43%, but the exergy efficiency is 96%. At the top and bottom of the humidifier, the effectiveness of heat transfer is higher than 70%, but the exergy efficiency at the bottom of the humidifier is lower than 20%. Adopting appropriate inlet air and water temperature are the available methods to reduce the exergy loss. The thermodynamic analysis in this work can provide a basis for optimizing HAT cycle configuration and humidifier structure.