Thermodynamic study of carbon dioxide transcritical refrigeration cycle with dedicated subcooling and cascade recooling.

• The effects of key parameters on system performance are investigated. • The optimal recooling capacity ratio is fitted by the neural network approach. • Lower limit of heat source temperature in the proposed layout is reduced by 4 °C. • 28.5% of compressor work in subcooling subcycle for the proposed layout is saved. • The payback period of proposed system is 10.1 years. Stimulated by the fast development of cold chain commodity market and a large amount of demand in cold storages, the application of CO 2 refrigeration system is to enhance remarkably. Owing to the low critical temperature of CO 2 , the dedicated subcooling technology is widely-used in the CO 2 transcritical refrigeration cycle to increase the system performance. In this regard, reducing the compressor power of subcooling subcycle and extending the working range of heat source temperature is highly important for the mechanical subcooling technology and absorption one, respectively. Motivated by such purpose, the CO 2 transcritical cycle with dedicated subcooling and cascade recooling is presented and the thorough investigation is performed thermodynamically. The proposed system is compared with layouts with dedicated mechanical subcooling and dedicated absorption one at first. Subsequently, the effect of recooling capacity ratio, the critical parameter for the system performance, is analyzed in-depth. Finally, the optimum recooling capacity ratio for different conditions is fitted by the neural network approach. Compared to layouts with dedicated mechanical subcooling and dedicated absorption one, the secondary compressor work goes down by 28.5% and the lower limit of heat source temperature is extended by 4 °C, respectively in the proposed system. The paper is favorable for the development and performance improvement of CO 2 transcritical refrigeration systems. [ABSTRACT FROM AUTHOR]