A theoretical and experimental investigation of an absorption refrigeration system for application with solar energy units

Abstract

Application of the second law of thermodynamics to refrigeration systems is useful in identifying the thermodynamic losses and in finding out where improvements might be made. Theoretical absorption refrigeration cycles are analysed using the first law-based equations of energy balances and the second law-based concept of lost work. A thermodynamic efficiency, defined and formulated from the lost work approach, is used to examine a lithium bromide -water absorption cooling cycle with hot water as the heat source and cooling water as the heat sink. The cycle parameters are varied over applicable operating ranges in order to find their effect on the cycle thermodynamic efficiency. To accomplish this objective and to make a parameteric analysis for the L iBr -water absorption cycle under steady-state conditions, two computer programmes are written. The results indicate the system might be improved by better design. The efficiency variation is compared to variations of coefficient of performance found in the literature. A LiBT -water absorption refrigeration system for low hot water temperature applications has been proposed and detailed design aspects have been considered. Fabrication and testing of a laboratory model of the absorption refrigeration system have been described. As new design methodologies of solar energy applications have been developed recently, a study of solar thermal systems for absorption refrigeration has been presented. This includes the classification, description and modelling of solar systems. Types of design procedures of solar systems for absorption refrigeration are discussed and a computer programme has been implemented which prints out the yearly solar fraction of a solar thermal system with daily storage for supplying heat to an absorption cooling cycle. Numerical performance tests are carried out and the results show that the phibar-f chart design method is a simple and convenient mean of predicting the thermal performance of solar systems.