Thermodynamic analysis and performance evaluation of activated carbon-ethanol two-bed solar adsorption cooling system

Abstract

• Thermodynamic analysis of a two bed solar adsorption refrigeration system is presented. • Activated carbon-ethanol is the best adsorbent-adsorbate pair for the continuous operating adsorption cooling cycle. • The maximum C O P S Y of the system is 0.68 for the desorption temperature of 95 °C. • Dependency of performance parameters with desorption temperature is studied. • Isothermal adsorption is thermodynamically efficient as compared to isobaric adsorption. In this study, a thermodynamic model for analysing the performance of a two-bed solar adsorption cooling system (SAC) has been presented. It projects isothermal adsorption instead of isobaric to reduce the heat of adsorption and hence improve the performance of SAC system. An adsorption chiller of 500 W capacity operating at an evaporator temperature of 5 °C and a condenser temperature of 45 °C is selected for the present research. The proposed adsorption chiller uses activated carbon/ethanol as the working pair. The refrigeration cycle operates between an evaporator pressure of 2.01 kPa and a condenser pressure of 23.1 kPa. The input heat distribution in the bed component, followed by, assessing the effect of maximum desorption temperature on the performance of the system is also carried out. The maximum coefficient of performance of 0.68 is observed for a desorption temperature of 95 °C.The thermal performance of the system is also studied for adsorbate fraction, adsorbent bed pressure and effect of desorption temperature on various parameters. It has been found that the isothermal adsorption process increases the thermal performance of the SAC and it is estimated that coefficient of performance of the system with isothermal adsorption is 13.23% times more when compared with conventional isobaric adsorption. The study aims at providing a formidable solution to the low performance of adsorption cooling systems.