Design, Construction and Performance Evaluation of a Combined Refrigerator and Food Warmer

Abstract

The design, construction and performance evaluation of a combined refrigerator and food warmer based on vapour compression refrigeration cycle has been carried out in this work. The research has been conducted with the motive of recoverying the condenser heat for food warming. In this way, the system has been used in performing the dual purpose of a refrigerator and a heat pump. The system comprises a conventional refrigerator utilizing HFC-134a as refrigerant and the warmer mounted on top of the refrigerator. The insulation consists of polyurethane foam for the cold chamber and fibreglass for the warmer. Relevant thermodynamic relations were used to design the important parameters of the system, such as refrigeration effect and capacity, compressor size, lengths of evaporator, capillary and condenser tubes, and thickness of the walls of the refrigerator and warmer compartments. In the experimental tests conducted, temperatures of -12 oC and 69 oC were obtained in the unloaded refrigerator and warmer respectively. About two and a half litres of water at an initial temperature of 27.8 oC became frozen within a period of approximately 120 minutes in the refrigerator. The same quantity of water at the same initial temperature was heated to 50 oC in about 150 minutes.