Intermediate pressure of two-stage compression system under different conditions based on compressor coupling model

Aimed at a two-stage compression system consisting of two compressors with the low-pressure end as inverter twin rolling piston and the high-pressure end as non-inverter isolated rolling piston, based on the geometric model of compressor, and by application of the theories such as mass or energy conservation equations, mass leakage loss model, heat transfer, etc, this paper established a dynamic compressor coupling model in a two-stage compression system with variable capacity, which was experimentally verified. It was revealed that the two-stage compression was not a continuous compression process. The intermediate pressure has the fluctuation characteristics. Among all factors related to the intermediate pressure, the effect of the ratio of the theoretical displacement of the low-stage compressor to that of the high-stage compressor on the intermediate pressure was the most vital determinant. The intermediate pressure was sensitive to the variation of heating capacity, but it was passivated to the heating COP.

▶ Two-stage compression dynamic coupling model with variable capacity was established. ▶ Two-stage compression dynamic coupling characteristic is described and analyzed. ▶ Thermodynamic parameters in the controlling volume have the fluctuation performances. ▶ The characteristics of intermediate pressure under different conditions are analyzed. ▶ Variations of system heating capacity and COP with intermediate pressure are analyzed.