Performance optimization of transcritical CO2 cycle with parallel compression economization

Being a low critical temperature fluid, CO2 transcritical system offers low COP for a given application. Parallel compression economization is one of the techniques to improve the COP for transcritical CO2 cycle. An optimization study of transcritical CO2 refrigeration cycle with parallel compression economization is presented in this paper. Further, performance comparisons of three different COP improvement techniques; parallel compression economization alone, parallel compression economization with recooler and multistage compression with flash gas bypass are also presented for chosen operating conditions. Results show that the parallel compression economization is more effective at lower evaporator temperature. The expression for optimum discharge pressure has been developed which offers useful guideline for optimal system design and operation. Study shows that the parallel compression with economizer is promising transcritical CO2 cycle modifications over other studied cycle configurations. A maximum improvement of 47.3% in optimum COP is observed by employing parallel compression economization for the studied ranges.