Investigation on the coupled heat and mass transfer process between extremely high humidity air and liquid desiccant in the counter-flow adiabatic packed tower

This paper presents the theoretical and experimental studies on the coupled heat and mass transfer process in a counter-flow adiabatic structured packed tower with the inlet air humidity ratio ranging from 20 g/kg air to 160 g/kg air. The simulation results show that the ε-NTU model is no longer reliable for extremely high humidity conditions, as the assumptions of the ε-NTU model are no longer valid due to the great solution concentration variation. The finite difference model shows that the driving forces of heat and mass transfer decline much more significantly in high humidity conditions than in low humidity conditions. Totally 313 experimental runs were conducted using noncorrosive KCOOH as the liquid desiccant. The experimental results indicate the optimal ranges of the main parameters in high humidity conditions. Moreover, empirical correlations are obtained for the humidity removal rates at varying parameters. In high humidity conditions, the dehumidification effect is more significantly influenced by the liquid-air flow rate ratio and less influenced by the desiccant concentration and temperature compared with the low humidity conditions. This research helps to understand the heat and mass transfer process in extremely high humidity conditions and promote the application of liquid desiccant dehumidification technology in the field of industrial waste heat recovery.