Experimental study on partially internally cooled dehumidification in liquid desiccant air conditioning system

Abstract

The dehumidifier is one of the essential components in air-conditioning systems with liquid desiccant. Compared with adiabatic dehumidifiers, internally cooled dehumidifiers can achieve better dehumidification performance. In this study, dehumidification effectiveness and moisture removal rate were adopted to evaluate and compare the performance of these two kinds of dehumidifiers. The results indicated that internally cooled dehumidifiers can significantly improve performance compared with adiabatic dehumidifiers, especially when the solution is at a high temperature and/or low concentration in the downstream section of the liquid desiccant flow. Performance improvement and energy saving can be taken into consideration simultaneously by only supplying cooling water to the latter part of the dehumidifier. Solution temperatures at 20-25°C for adiabatic dehumidifiers are optimal and those at 25-30 °C for internal cooled types. Lower temperatures of the cooling water can result in higher values for dehumidification effectiveness and moisture removal rate in an internally cooled dehumidifier; the limited temperature difference between cooling water and solution might seriously weaken the effect of the cooling water. Dimensionless Sherwood number Sh was calculated, and discrepancies between predicted values and experimental data are almost within ±20%. © 2013 Elsevier B.V.