Evaluation of the effectiveness-NTU method for countercurrent humidifier

Abstract

An analytical method is advantageous in designing and optimizing the humidifier of the humid air turbine cycle. In this paper, the energy effectiveness-NTU model for the countercurrent humidifier is built and verified by the 141 groups of test data obtained from an experimental facility of pressurized packing humidifier. The effect of pressure and inlet conditions including water/air mass flow rate ratio, inlet water temperature and inlet air wet bulb temperature on the heat capacity rate ratio and the energy effectiveness is analyzed. A sensitivity analysis is performed in order to indicate the key inlet parameter to improve the energy effectiveness of countercurrent humidifier. It is shown that the maximum deviation of the energy effectiveness calculated by the analytical method is 22.7% comparing to the experimental data. However, the maximum deviation is not more than 16% when considering the actual operating conditions for the humidifier of heat capacity rate ratio being greater than1.5. Heat capacity rate ratio changes monotonically with pressure and inlet parameters, and the energy effectiveness has an inflection point of minimum value when heat capacity rate ratio is equal to 1. Sensitivity analysis shows that water/air mass flow rate ratio is the most critical factor.