Plastics, compressors, CHT, superheating
Manufacturers of hermetic refrigeration compressors for domestic and commercial applications have been increasing the energy efficiency of their products systematically over the last decades through the continuous efforts of in-house research groups, universities and suppliers. This joint effort encompasses the technical fields of design, materials, processes, manufacturing, and simulation techniques, to achieve a multidisciplinary approach to compressor optimization as applied to refrigeration systems. Gains such as increased efficiency of the electric motor, reduction of bearing friction power loss, minimizing back flow on valves have already been addressed and the continuous search for new approaches have been proposed. This work presents a study of energy efficiency gain by comparing low conduction heat transfer plastic materials to metallic materials used in current compressor designs. The components compared include the cylinder head, discharge muffler, shock loop, valve plate and crankcase. The energy efficiency gain was evaluated using the Coefficient of Performance (COP) through the use of the Conjugate Heat Transfer (CHT) model using superheating temperature. The CHT model temperature results were compared with the values measured by an instrumented compressor. To complement the study, the parts and assemblies were structurally evaluated using the finite element method under performance and durability test operating conditions. The feasibility of the mold filling process was verified, because the final design of the components must be a compromise between functional requirements and process solution. In conclusion, the results show that significant efficiency gains can be achieved through the use of engineering thermoplastic. This is achieved through careful material selection and proper design that considers not only material properties, but material and process costs using the flexibility of injection molding to group parts and subsystems.