Theoretical analysis of heat and mass transfer characteristics of a counter-flow packing tower and liquid desiccant dehumidiflcation systems based on entransy theory

摘要

Dehumidifier and regenerator are the key components of a liquid desiccant dehumidification system. This paper examines the heat and mass transfer processes of a counter-flow packing tower using entransy analysis. Under ideal thermodynamic conditions, if NTU rn of the counter-flow packing tower is infinite, the reversible process only exists when the inlet states of air and solution lie on the same isorelative humidity line. In actual heat and mass transfer processes, the relative position of the inlet parameters of air and solution in the psychrometric chart will influence the entransy dissipation in the packing tower. Based on the analytic solution of temperature difference and humidity ratio difference between air and solution, minimum entransy dissipation is determined when the states of inlet air and solution lie on the same iso-relative humidity line. The influence of inlet characteristics can be quantified using an unmatched coefficient of inlet parameter (gamma). This parameter is an indicator of the flow-path design and the system optimization. Furthermore, a practical application is presented by comparing three typical flow paths. The flow path with the smallest y value reduces the required temperature of heat sources from 60 degrees C to 45 degrees C. The realization of such low-grade heat sources not only means high/efficient utilization of heat or solar energy, but also results in less waste heat. (C) 2017 Elsevier Ltd. All rights reserved.