Heat and mass transfer in an internally cooled ionic liquid dehumidification system: Experimental study and empirical modeling

In response to increasing demands for energy-efficient and environmentally friendly humidity control, liquid desiccant dehumidification systems have attracted increasing attention for their potential in heating, ventilation, and air conditioning (HVAC) applications. This study developed and experimentally investigated an internally cooled dehumidification system using Crecoplus 5100c ionic liquid (IL) as the working fluid. This IL was selected owing to its low corrosivity, favorable thermophysical properties, and compatibility with internally cooled configurations, rendering it particularly suitable for stable and long-term dehumidification. The system integrates a vertical counterflow configuration with a fin-tube heat exchanger to enhance heat and mass transfer. Parametric analyses were conducted to evaluate the effects of cooling water temperature and flow rate, IL temperature and flow rate, and air flow rate on dehumidification performance. The results indicated that lower cooling water temperatures and higher flow rates significantly improved the vapor pressure gradients and enhanced mass transfer. Increasing the IL flow rate significantly enhanced the wetting of the heat exchanger surface and the gas–liquid contact area. This improved the dehumidification efficiency by up to 238% and increased the mass transfer coefficient by over threefold. In the present experiments, the maximum dehumidification efficiency was over 90% at high IL flow rates. Empirical correlations for Sherwood and Nusselt numbers were developed based on dimensionless parameters and validated against experimental data. The developed Sherwood correlation achieved a mean absolute deviation (MAD) of 29.5%, whereas the Nusselt correlation achieved an MAD of only 1.4%, substantially lower than those of existing correlations. These findings offer practical insights for optimizing operational parameters and improving the design and control of IL-based dehumidification systems.