Contribution to the improvement of the energy efficiency of solar sorption refrigeration systems: application to absorption systems

Abstract

Solar-driven absorption refrigeration using the ammonia–water (NH₃–H₂O) pair offers a sustainable cooling solution for regions with high solar potential. This thesis develops a steady state thermodynamic model of a single-effect NH₃–H₂O solar absorption refrigeration system, based on mass, energy, and equilibrium balances, and solved using Engineering Equation Solver (EES). A parametric study examined the effects of generator temperature, evaporator temperature, absorber/condenser pressures, and ammonia concentration on the coefficient of performance (COP). Results show COP increases with generator temperature up to an optimum, beyond which irreversibility limits further gains, while higher ammonia concentration improves COP by reducing the circulation ratio. Conversely, increasing evaporator temperature reduces COP due to shifts in solution equilibrium. The maximum COP obtained was 1.28, at Ph = 7 bar, Pb = 1 bar, x = 25%, and a generator temperature of 110–115°C. The model was validated against published data, showing good agreement. These findings identify optimal operating regions and offer design guidelines for improving solar absorption cooling performance in high-irradiation regions such as Algeria.