Development of a solar-driven adsorption cooling system for a continuous production of cold
Creators: name: Ahmed, Hassan Zhohair Hassan
Publisher: name: University of Calgary
Year: 2012

description: Bibliography: p. 224-246
description: Some pages are in colour.
description: Refrigeration applications contribute in a considerable number of fields in human life and consume large amount of electricity. The booming progress in the field of green cooling technology offers a considerable number of solar-powered refrigeration systems as alternatives for the conventional refrigeration machines. However, due to the intermittent nature of the solar radiation, the day-long continuous production of cold is a challenge for the solar-driven cooling systems. In the present study, a novel solar-powered adsorption cooling system which is able to produce cold continuously along the 24-hours of the day is proposed. This system has a flexibility to control the cold production process, cooling duration, as well as starting and ending the cooling at any time as required. The introduced system consists of two adsorption beds which are integrated in a single flat plate solar collector and positioned at the opposite sides of the solar collector. A complete cycle of the system consists of two half-cycles which are similar in operation. Each half-cycle operational time period is 24 h, starting at the apparent sunrise time and ending at the next day sunrise time. The theoretical thermodynamic operating cycle of the system is based on adsorption at constant temperature. A complete cycle consists mainly of four consecutive processes; an isosteric preheating and pressurization process, an isobaric heating and desorption process, an isosteric depressurization cooling process, and an isothermal cooling adsorption process. Both of the cooling system principle of operation and the ideal thermodynamic cycle description are explained in detail. Moreover, a steady state thermodynamic analysis is performed for all components and processes of the proposed refrigeration system. The analysis is based on the energy conservation principle and the equilib­rium dynamics of the adsorption process through the use of the Dubinin-Astakhov adsorption equilibrium model. Also, activated carbon-methanol is used as the work­ing pair in the case studied. Furthermore, the influences of various parameters on the system performance and operation are investigated and discussed. A mathematical model is developed to investigate the dynamic behavior of the system. The coupled heat and mass transfer equations within the reactor are derived from basic principles of the mass and energy balance relations. Additionally, the linear driving force equation which represents the non-equilibrium adsorption kinetics is merged with the derived equations. The variation of solar radiation along the day is considered to provide more realistic simulation through modeling the instantaneous local solar irradiation. In addition, the real local hourly ambient temperature and wind speed changes are also taken into account. The predictions for various cases and operational conditions are investigated and discussed. In addition, the feasibility to control the cold production process has been justified by the simulation model for two different control schedules. The system performance under different climatic conditions, summer and winter, as well as at different locations, Cairo and Calgary cities, has been studied as well.