Performance analysis of a centrifugal compressor in a vapor compression refrigeration cycle with an energy-based approach

Authors

1 Faculty of Mechanical Engineerig, Shahrood Unoversity of Technology

2 Faculty of Mechanical Engineering, Shahrood University of Technology

10.22044/jsfm.2025.15188.3903

Abstract

Despite the advantages of centrifugal chillers, such as high capacity, high energy efficiency, and stable performance, these systems have been less studied. Therefore, this research investigates the performance of centrifugal chillers under various conditions. Considering the sensitivity of centrifugal compressors to the mass flow rate, this study examines not only the thermodynamic aspects of the chiller cycle but also the operation of the centrifugal compressor. Thermodynamic and numerical modeling were conducted using the EES and CFX software, respectively.The results from the EES modeling showed that under identical mass flow rates and pressure ratios, the coefficient of performance (COP) of the cycle with the R134a refrigerant in a two-stage configuration was 8% higher than that of a single-stage configuration, while for the R744 refrigerant, the COP increased by 23%. Additionally, the examination of intermediate pressure in two-stage cycles revealed that the highest COP under the same conditions occurs when the intermediate pressure is 1.7 times the evaporator pressure.The analysis of different refrigerants indicated that R134a had the highest COP, while R744 exhibited the lowest COP. The effect of cycle mass flow rate on compressor performance was numerically investigated; the results demonstrated that increasing or decreasing the chiller cooling capacity by 50% brings the compressor performance closer to the surge and choke points. Furthermore, numerical analysis examined the Mach number in the impeller for different mass flow rates.

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References

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Journal of Solid and Fluid Mechanics
Volume 14, Issue 6
May and June 2025
Pages 1-18

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