4384 -- Analysis of Refrigerator / Freezer Appliances Having Dual Refrigeration Cycles ✓ Most Recent

This paper investigates the benefits of using two separate refrigeration cycles to meet demands for both the freezer and fresh food compartments in domestic refrigerators. The energy savings that can be obtained by delivering refrigeration at the higher temperature as required by the fresh food compartment is found to be a function of the cabinet load ratio (defined as the ratio of the fresh food to the freezer cabinet loads) and the ratio of the freezer and refrigerator cycle COPs. Depending on the values of these two parameters, the energy requirement for a dual-cycle * system can be up to 30% lower than that for a comparable single-cycle ** system meeting the same cabinet loads. This energy-saving approach can help manufacturers meet the Department of Energy's year 2001 energy use standards for domestic refrigerators. The dual-cycle system also offers the advantages of reduced defrost (not included in the previously mentioned energy savings estimate) and the ability to maintain higher humidity conditions in the fresh food compartment. The feasibility of using the fresh food compartment as a sink to subcool liquid refrigerant prior to its entry into the freezer capillary tube was also investigated. The advantage of the subcooler was found to be most significant at low cabinet load ratios in dual cycles for which suction-line heat exchangers were not present. When high-effectiveness suction-line heat exchangers in the fresh food and the freezer cycles were employed, a maximum reduction of 3% in total electrical power requirements at a cabinet load ratio of 1.0 resulted from the indirect mechanical subcooling modification.