Exergy and energy analysis of an adsorption-based power and cooling cogeneration system based on a complete coupled CFD model

This study presents a cogeneration osmotic heat engine system integrating finned tube adsorption separation unit and reverse electrodialysis unit. Few studies have analyzed the osmotic heat engine system from the perspective of the second law of thermodynamics. To fill this knowledge gap, an exergy and energy analysis of the cogeneration OHE system is conducted based on a complete coupled computational fluid dynamic model for the first time. In contrast to the commonly used lumped model of adsorption separation process in previous literatures, temporal and spatial variations within the adsorbent bed are considered. The effect of the fin geometric features on exergy destruction distribution and system performance is comprehensively discussed. Results reveal that the maximum exergy destruction rate occurs at the beginning of switching process. The configuration of branched fins renders the highest exergy destruction followed by that of straight fins and nullity fins. The exergy destruction with branched fins during heating process and reverse electrodialysis process accounts for around 50 % and over 20 % of the total exergy destruction, respectively. Larger fin pitch leads to reduced energy efficiency and total exergy destruction. However, the exergy efficiency exhibits a trend of initial reduction and subsequent improvement. As the branch angle and branch length increase, the energy efficiency, exergy efficiency and total exergy destruction are all first elevated and then reduced. A maximum exergy efficiency of 18.9 % can be obtained with a fin pitch of 64 mm, which rendering the electric efficiency of 0.37 % and COP of 0.68, respectively.