Cross vane expander compressor (CVEC) is a newly invented expander-compressor combined unit, where it is introduced to replace the compressor and the expansion valve in traditional refrigeration system. The mathematical model of CVEC has been developed to examine its performance and it was found that the energy consumption of a conventional refrigeration system was reduced by as much as 18%. It is believed that this result can be further improved by optimizing the device. In this paper, the coefficient of performance (COP) of CVEC has been optimized under predetermined operational conditions. Several main design parameters of CVEC were selected to be the variables and the optimization was done with theoretical model in a simulation program. The theoretical model consists of geometrical model, dynamic model, heat transfer model and valve dynamics model. Complex optimization method, which is a constrained, direct search and multi-variables method, was used in the study. As a result, the optimization study suggested that with an appropriate combination of design parameters, a large COP improvement in CVEC R134a refrigeration system is possible. With a reduction of 20% in the shaft radius and 17% in inner cylinder radius, and the increase of around 16% in ports diameter, an improvement of 58% in COP can be achieved.
Key words: Coefficient of performance (COP), cross vane expander-compressor, simulation, optimization.
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