Effect of Inter-Stage Pressure on Performances of Two-Stage Transcritical CO₂ Refrigeration Cycle with Dedicated Absorption Dual-Subcooling and Mechanical Recooling

The two-stage transcritical CO₂ refrigeration cycle with dedicated dual-subcooling and mechanical recooling is proposed. The inter-stage pressure is critical for such cycle performances; however, it has not been studied exactly. Therefore, the research aim is to disclose the effect of inter-stage pressure on performances of the proposed cycle. The main work consists of four aspects. Firstly, the comparative study is performed to display advantages of the proposed cycle. Secondly, the key temperatures, heat and power consumptions as well as performance indicators for different inter-stage pressures are analyzed in detail, based on the parametric model. Thirdly, the optimal inter-stage pressure for different conditions is obtained by the nonlinear direct search method. Finally, the economic performance is assessed. It is found that the compressor power of the proposed cycle drops by 12%, and the working temperature lower limit is reduced by 11°C. Furthermore, it is considered that the optimal inter-stage pressure is insensitive to the heat source temperature. The novelty lies in illustrating the effect of inter-stage pressure, obtaining trends of the optimal value, and pointing out the system feasibility. The paper is favorable for design and operation optimization of the proposed system.