Performance comparison of an adiabatic and an internally cooled structured packed-bed dehumidifier

Liquid desiccant dehumidifiers are used to improve the indoor air quality and achieve lower humidity levels in conditioned spaces. The performance of these dehumidifiers can be enhanced by providing simultaneous cooling in them. This paper presents the performance comparison of an adiabatic and an internally cooled structured packed-bed dehumidifier. The non-adiabatic structured packed-bed absorber consists of rigid media pads with cooling water flowing through the tubes embedded in the packing. The desiccant (CaCl2 in this study) falls by gravity while air flows in the cross flow configuration. The performance of this absorber has been evaluated at varying desiccant flow rates. The moisture removal from the air, the effectiveness of the dehumidifier and the mass transfer coefficients between air and solution have been compared for the dehumidifier operation with and without internal cooling. It is found that the optimum liquid to gas flow rate ratio for maximum effectiveness is about 1.0.

Research highlights
► For internally cooled desiccant dehumidifiers, a maximum effectiveness of 0.706 was achieved experimentally.
► An optimum desiccant flow rate of 5l/min yielded the maximum dehumidifier effectiveness.
► At this flow rate, the corresponding liquid to gas flow was about 1.0.
► The effectiveness of a cross flow dehumidifier is much less as compared to a counterflow configuration despite internal cooling.