Investigation of heat and mass transfer and gas–liquid thermodynamic process paths in a humidifier

A humidifier is crucial for water evaporation in a humidification–dehumidification desalination system. Its performance has a significant impact on system efficiency. However, existing models are not fully applicable to the estimation of heat and mass transfer in a humidifier. In this paper, a novel gas–liquid heat and mass transfer model for a humidifier is proposed. It can accurately predict the heat and mass transfer performance in the humidifier. It is observed that increasing liquid inlet temperature improves the humidifier performance most significantly. In the humidifier, the temperature and humidity ratio of air increase in waves along the height. The distributions of the heat and mass transfer rates are primarily dominated by the transfer driving forces. Heat and mass transfer primarily occur at the top and bottom of the humidifier because of the considerable difference in the temperature and humidity ratio at the two terminals. The air rapidly reaches supersaturation during the heated and humidified processes, whereas the supersaturation is low, with the highest being 2.1%. The thermodynamic process path of air in the supersaturation stage can be simplified as lying on the saturation curve. The resulting error is less than 4%.