An irreversible thermodynamic model for solar absorption refrigerator

A solar refrigerator is made of a solar collector and a refrigeration system. Real solar refrigerators usually operate between two limits, maximum coefficient of performance (COP) and maximum cooling load. A new model is presented to describe an irreversible absorption refrigerator, in which not only the irreversibilities of heat conduction but also those resulting from friction, eddy and other irreversible effects inside the working fluid are considered. The influence of these irreversible effects on the performance of an absorption refrigerator with continuous flow is investigated. The analytical expressions of the optimal refrigeration coefficient and the cooling rate of the refrigerator are derived. The predictions of the model are compared with semi-empirical cycle model of single-stage absorption refrigeration machines. The results obtained here can describe the optimal performance of a four temperature level absorption refrigeration affected simultaneously by the internal and external irreversibilities and provide the theoretical bases for the optimal design and operation of real absorption refrigerators operating between four temperature levels.