Model-based investigation of a heat pump driven, internally cooled liquid desiccant dehumidification system

Liquid desiccant dehumidification system is regarded as a promising and energy-saving solution for dehumidification. A heat pump driven internally cooled desiccant dehumidification system is investigated in this paper. Dehumidifier and regenerator are both internally cooled/heated types compared to previous adiabatic ones, and heating and cooling capacities of a heat pump cycle are utilized for regeneration and dehumidification respectively. System model is established and validated to investigate system performance and effects of different influencing parameters. It's indicated that two main issues, which are restricting the system performance, are encountered, i.e. mismatching property among the three fluids inside the dehumidifier/regenerator and heat offset due to solutions circulating between dehumidifier and regenerator. Heat transfer mismatching ratio (xt) and mass transfer mismatching ratio (xω) are defined to indicate the degree of mismatching property. A lower solution flow rate and a solution-solution heat exchanger with a better recovery efficiency are highly recommended to obtain a better system performance. Further, an improved system with external pre-cooler and pre-heater was proposed to improve the matching property among the three fluids, and COPsys is found to be increased from 5.96 to 6.68 with an increasing ratio of 12%. xt is found to be reduced from 0.357 to 0.168, and xω from 0.282 to 0.127.