Energy, entransy and exergy analyses of a liquid desiccant regenerator

Abstract

In the present study, the energy exchange between the liquid desiccant and the ambient air, entransy dissipation during coupled heat and mass transfer processes and exergy destruction with respect to the reference state for the liquid desiccant regenerator are analyzed. Expressions for energy, exergy and entransy (EEE) of the regenerator are derived and also quantified along the height of the liquid desiccant regenerator. By varying the operating parameters such as desiccant temperature and concentration, air temperature and humidity ratio and air and desiccant flow rates, the performance of the regenerator is investigated in terms of entransy, exergy and desorption efficiencies. From the EEE analyses, it is observed that by increasing the desiccant temperature from 60.3 °C to 65.2 °C and decreasing the air humidity ratio from 18.7 gwv/kgda to 14.3 gwv/kgda simultaneously, the overall energy exchange, exergy destruction and entransy dissipation are increased by 26%, 37% and 39%, respectively. Further, the entropy generation along the tower height is also investigated and observed that for a given set of operating conditions, with increase in distance along the tower height, the entropy generation increases by 96% and decreases by 35% for the air side and the solution side, respectively.