THERMODYNAMIC OPTIMIZATION OF SOLAR-DRIVEN REFRIGERATORS

This paper describes the thermodynamic optimization of a class of refr igerators without work input, which are driven by heat transfer from a solar collector. The model consists of a finite-size solar collector with heat loss to the ambient, and a refrigerator with three finite-si ze heat exchangers, namely, the evaporator between refrigeration load and refrigerant, the condenser between the refrigerant and the ambient , and the heat exchanger between the solar collector and the refrigera nt The total thermal conductance of the three heat exchangers is fixed . The solar collector heat loss to the ambient is proportional to the collector-ambient temperature difference. The first part of the paper reports the operating conditions for maximum refrigeration effect, spe cifically the optimal collector temperature, and the optimal way of al locating the thermal conductance inventory to the three hear exchanger s. For example, the optimal condenser conductance is equal to half of the total thermal conductance, and is independent of other operating p arameters. The second part of the paper examines the changes in the op timal design when the price of the refrigeration load (p(L)) is differ ent (higher) than the price of the heat input provided by the collecto r (pH). The optimal collector temperature and the optimal three-way al location of the thermal conductance inventory are reported as function s of the price ratio p(H)/p(L).