A humidification test stand can be used for study on cyclic humidification process of humid air turbine（HAT） has been established. Adopting self-designed swirl nozzle

through changing the diameter of spray-hole at top of the nozzle

the air inlet and oulet parameters in different atomizing fields have been measured

and the influence of liquid-drop size upon the heat transfer and mass transfer process being analysed. The results of test show that the relation between heat medium transfer performance and liquid-drop size isn’t merely increasing or decreasing one

but having an optimal atomizing particle size distribution i.e. Sotainian mean diameter（SMD）.