OPTIMAL ALLOCATION OF A HEAT-EXCHANGER INVENTORY IN HEAT DRIVEN REFRIGERATORS

This paper reports the thermodynamic optimization (or entropy generation minimization) of a heat-driven refrigeration plant, that is, a refrigerator without work input, which is driven by a heat source. The treatment accounts for the heat transfer irreversibilities of the three heat exchangers, and for the finiteness of the total heat-exchanger inventory. The operating conditions for maximum refrigeration rate are determined. It is shown that the heat-exchanger inventory must be divided optimally between the three heat exchangers. For example, half of the inventory must be placed in the hear exchanger used to reject heat to the ambient. The maximum refrigeration rate per unit of total heat exchanger inventory is reported. These thermodynamic optimization principles are then applied to a refrigerator driven by heat transfer from a solar collector.