Thermodynamic Modelling and Experimental Investigation of Two Bed Solar Vapour Adsorption Cooling System

Abstract

Adsorption cooling technology is an alternative to conventional cooling systems. The low heat transfer properties of the adsorbent-adsorbate pair utilised in adsorption cooling systems have an impact on the performance of the systems. Thus, researchers are concentrating on enhancing the performance of the system by introducing new composite adsorbent pairs. A transient model of a two-bed adsorption cooling system employing activated carbon-ethanol is presented to evaluate performance. The Coefficient of Performance (COP) and Specific Cooling Power (SCP), have been evaluated using SIMULINK platform. An adsorption chiller of 600 W capacity operating at an evaporator temperature of 50C with isothermal adsorption is used to improve the performance of system. The analysis envisages that a maximum heat input is used for the desorption of adsorbate from the bed and is 4543.44 kJ. The maximum COP is 0.68, for a desorption temperature of 950C. Moreover, the exergy destruction of the adsorbent bed has been evaluated as 0.19 kW. The next phase of the work is the design, development and performance study of the two-bed adsorption cooling system. The evaporator, condenser, adsorbent bed, energy storage tank and solar collector are designed and fabricated. The experimental COP of the system is 0.68 for the maximum hot water inlet temperature of 880C. The study also concentrated to investigate a composite adsorbent for the proposed system. The characteristic study of the composite suggests, composite B, having activated carbon 70% in weight, expanded graphite powder 10%, metal organic framework 10% and binder 10% as the favourable choice for adsorption cooling system. The thermal conductivity of the composite B and volumetric adsorption uptake of activated carbon ethanol is determined as 0.29 Wm-1K -1 and 0.983 respectively. The thermodynamic modelling of the system as well as experimentally with the selected composite adsorbent ethanol is carried out to evaluate its performance. The study reveals that COP of the system increases by 14.81% when using composite as compared with activated carbon-ethanol. The performance of the proposed system with the thermal energy storage material is also investigated. It is observed that the COP of the system increases by 20.69% as compared to the adsorption cooling system that uses activated carbon-ethanol