Dehumidification performance analysis of counter and cross flow liquid desiccant dehumidifiers for a packaged liquid desiccant air conditioning unit

Abstract

In this research, dehumidification performances of two packed-bed liquid desiccant dehumidifiers having different air-to-liquid flow configurations; that is, the cross flow and the counter flow types, were compared via a series of experiments carried out in the environmental test chamber. As performance indices, dehumidification effectiveness and enthalpy effectiveness were measured in each experiment for both liquid desiccant dehumidifiers. In order to predict dehumidification performance of both liquid desiccant dehumidifiers in various operating conditions, empirical models returning the dehumidification effectiveness and enthalpy effectiveness of both counter flow and cross flow type dehumidifiers were also derived based on the experimental data. The empirical models were compared with existing models to validate the reliability of the proposed models. From the sensitivity analysis conducted by using the proposed empirical correlations, it was observed that the dehumidification performance of the counter flow type liquid desiccant dehumidifier was highly affected by the inlet air humidity ratio and the inlet temperature of the desiccant solution, while the performance of the cross flow type dehumidifier was relatively less affected by those operating parameters. Consequently, one may conclude that the cross flow type liquid desiccant dehumidifier would provide relatively stable dehumidification performance regardless of the humidity ratio of the entering process air and the temperature of the desiccant solution, while the counter flow type dehumidifier would show better dehumidification performance at the higher humidity ratio of the entering process air and at the lower temperature of inlet desiccant solution. However, the cross flow type dehumidifier may have limited dehumidification performance especially in the lower solution temperature and in the highly humid process air conditions.