Counter-crossflow indirect evaporative cooling-assisted liquid desiccant dehumidifier: Model development and parameter analysis

Abstract

Using auxiliary internal cooling is an effective way to improve the dehumidification effectiveness of the liquid desiccant dehumidifier (LDD) compared with the adiabatic dehumidifier. Indirect evaporative cooling (IEC) is a promising solution for internal cooling owing to its high efficiency and environmentally friendly features. A hexagonal plate heat exchanger (PHE) consisting of both counterflow and cross flow was used as a core in an IEC-internally-cooled LDD to ensure efficient heat transfer and facilitate easy installation simultaneously. A numerical heat and mass transfer model was established and validated, and an intensive parameter analysis of the thermal performance of the dehumidifier was conducted. The influential parameters include inlet primary air conditions (temperature, humidity, and velocity), inlet solution conditions (temperature, mass flow rate, and concentration), secondary to primary airflow ratio, the geometry of the heat exchanger, and channel gap. The performance of the newly developed counter-cross flow LDD with IEC-assisted cooling was improved by 16 % and 8.4 %, respectively, compared to the adiabatic and staggered flow type dehumidifiers. Among all the design parameters of the heat exchanger, the channel gap has the most significant effect on the dehumidification efficiency, and the recommended optimum height is 0.004 m. The air velocity is the most influential operating parameter on the dehumidification efficiency. The dehumidification effectiveness is reduced by 23 % as the primary air inlet velocity decreases from 4.5 m/s to 0.5 m/s.