Assessment of adsorber bed designs in waste-heat driven adsorption cooling systems for vehicle air conditioning and refrigeration

Adsorber bed design strongly affects the performance of waste-heat driven adsorption cooling systems (ACS) for vehicle air conditioning and refrigeration (A/C-R) applications. Adsorber beds should be specifically sized for vehicle A/C-R considering the limitations of mobile applications. However, there is no conclusive evidence on what type of adsober bed is proper for vehicle applications. To evaluate the performance of ACS, specific cooling power (SCP), adsorber bed to adsorbent mass ratio, and coefficient of performance (COP) are introduced and their order of importance are assessed. To investigate the available studies in the open literature, desired SCP of 350 W/kg dry adsorbent and adsorber bed to adsorbent mass ratio of less than one are calculated for a 1-ton-of-refrigeration, 2-adsorber bed, silica gel-water ACS. According to these criteria, previous studies are summarized into nine groups with respect to their adsober beds and consequently, finned tube adsorber bed design is selected among the existing designs. Finally, optimization of fin spacing and fin height, and enhancing thermal conductivity of adsorbent material by adding metal wool inside the finned tube adsorber bed are proposed as the practical solutions to increase heat and mass transfer rates within the adsorber bed.