frost-free refrigerator, optimization, energy, cost
A steady-state simulation model was devised and its predictions for energy consumption were compared with experimental data obtained elsewhere, with differences not exceeding a 9% error band. The model was used to find out the evaporator air flow rate, the number of evaporator and condenser fins, the compressor size and efficiency, and the insulation thicknesses of both compartments which yield the minimum energy consumption when the total cost is constrained. The optimization led to a refrigeration system with energy consumption 18% lower than that observed for the baseline system without any cost penalty. The system performance for four different compressors including a high efficiency, a large capacity and a variable-speed one was also analyzed. According to the cost function adopted, the variable-speed compressor shall not cost 26% more than a single-speed one with the same piston displacement.