Thermodynamic limits of humidifiers and dehumidifiers

Humidification and dehumidification are among the most important desalination technologies, in which humidifiers and dehumidifiers are the key components. Previous research has mainly focused on overall system improvement, but few studies have focused on the thermodynamic limitations of the humidification and dehumidification processes. By introducing temperature and enthalpy effectiveness, the thermodynamic limits have been explored. It was successfully established that there are three operating states for the humidifier and dehumidifier. The analytical expressions of enthalpy and temperature effectiveness boundary values in each state were obtained. The results of visualizing the influence of mass flow ratio, inlet temperature, inlet and outlet relative humidity, and pressure on the feasible range of enthalpy and temperature effectiveness were presented. This study explores the thermodynamic limits of heat and mass transfer equipment that can be applied to other types of humidification and dehumidification equipment.