Performance evaluation of a two-stage silica gel + water adsorption based cooling-cum-desalination system

• Futility of air-cooled single-stage adsorption cooling system is demonstrated.
• Design features of two-stage silica-gel + water adsorption system are reported.
• Proposed an empirical way of accommodating thermal wave phenomena.
• Assessment of system performance for various cycle times and evaporator pressures.
• Optimum cycle time is observed to be independent of evaporator pressure.

The first objective of this paper is to show that a single-stage adsorption based cooling-cum-desalination system cannot be used if air cooled heat rejection is used under tropical conditions. This objective is achieved by operating a silica gel + water adsorption chiller first in a single-stage mode and then in a 2-stage mode with 2 beds/stage in each case. The second objective is to improve upon the simulation results obtained earlier by way of empirically describing the thermal wave phenomena during switching of operation of beds between adsorption and desorption and vice versa. Performance indicators, namely, cooling capacity, coefficient of performance and desalinated water output are extracted for various evaporator pressures and half cycle times. The improved simulation model is found to interpret experimental results more closely than the earlier one. Reasons for decline in performance indicators between theoretical and actual scenarios are appraised.