Experimental analysis of dehumidification performance of counter and cross-flow liquid desiccant dehumidifiers

Abstract

In a liquid desiccant dehumidifier, the air-to-solution flow direction plays an important role in the dehumidification performance and the physical size of the dehumidifier tower. In this research, the dehumidification performance of counter-flow and cross-flow liquid desiccant dehumidifiers were compared via a series of experiments carried out in the environmental test chamber. To predict the dehumidification performance of both flow type dehumidifiers in various operating conditions, empirical models returning the dehumidification effectiveness and the enthalpy effectiveness, which were adopted as performance indices, were also derived based on the experimental data. From the sensitivity analysis conducted by using the proposed empirical correlations, it was observed that when the inlet air humidity ratio increased from 10.1 g/kg to 22.7 g/kg, the dehumidification effectiveness and enthalpy effectiveness of the counter-flow liquid desiccant dehumidifier increased from 51.2% to 82.4% and 40.2% to 72.5%, respectively. Meanwhile, both effectiveness values of the cross-flow dehumidifier increased from 62.3% to 63.4% and 46.3% to 55.0%, respectively. Likewise, when inlet solution temperature varied from 15.2 to 31.1 °C, the dehumidification effectiveness and enthalpy effectiveness of the counter-flow type dehumidifier decreased from 71.7 to 45.4% and 64.4 to 47.3%, respectively, while those of a cross-flow type dehumidifier decreased from 65.3 to 54.8% and 55.8 to 45.2%. Consequently, one may conclude that the cross-flow liquid desiccant dehumidifier would provide relatively stable dehumidification performance regardless of the changes in operating parameter, but the cross-flow dehumidifier may have limited dehumidification performance, especially at the lower desiccant solution temperature and in highly humid process air conditions.