Derivation and validation of dimensionless models for the heat and mass transfer coefficients of a structured packed bed dehumidifier

This study presents the derivation of two general types of correlation for the heat and the mass transfer coefficients (inside an adiabatic structured packed bed of a liquid desiccant system, which uses aqueous lithium chloride as a solution) as expressions of Nusselt and Sherwood numbers, respectively. These general equations summarize the physical and thermophysical properties of the air, the solution, and the contactor, which make them capable to be used for any parametric study provided they are fitted in a wide range of experimental data that include all the properties involved. Specifically, in this study, the experimental data taken at various air superficial velocities and solution flow rates were fitted to the said correlations. Comparison between the predicted and experimental values shows very good agreement with deviations for both coefficients within ±10% and average errors of 4.58 and 2.79% for the heat and the mass transfer coefficients, respectively. In addition, the calculated outlet air humidity ratios and temperatures match closely the experimental data. The fitted correlations for the heat and the mass transfer coefficients can be used to perform parametric studies at different air superficial velocities and solution flow rates with very good accuracy.