The mass transfer performance in a packed pilot absorber with an inverse U-shaped tunnel to prevent the carryover of solution is discussed in this study. The empirical correlation for the overall gas-phase volumetric mass transfer coefficient (K(y)a) is determined. The correlation is given in dimensionless form by Sh(G)' = 8.9 X 10(-8) (p(soln)/P)(-0.57) (ScGReG1.53)-Re-1/3 and the modified Sherwood number (Sh(G)') is defined in this study for the overall volumetric mass transfer coefficient. The vapor pressure of the working solution (p(soln)) is used to represent the characteristics of different working solutions at their operating concentrations and temperatures. This will overcome the disadvantages of the traditional convective mass transfer relationships which use such indirect parameters as the viscosity, density, or concentration to represent the working solutions in their correlations. Because the liquid desiccant solution works on the principle of absorption and has the property of absorbing moisture from air, the vapor pressure of the inlet liquid solution is lower than that of the air stream, and dehumidification take place. Therefore, the driving force of dehumidification in the absorber is dependent on the vapor pressure of the working solution. Our data showed that the mass transfer coefficients varied significantly with the vapor pressures of the working solutions. The correlated equation shown above fitted the experimental data very well, and the average value of the errors between predictions and experimental data is about 4%.