BITZER semi-hermetic piston and screw compressors for CO2 cascade refrigeration systems
- Authors: Renz G.1
-
Affiliations:
- Bitzer Kuelmashinenbau GmbH
- Issue: Vol 92, No 2 (2003)
- Pages: 2-6
- Section: Articles
- URL: https://journals.rcsi.science/0023-124X/article/view/106129
- DOI: https://doi.org/10.17816/RF106129
- ID: 106129
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Abstract
After many years of oblivion of carbon dioxide, the interest to it from the side of developers of refrigeration equipment has recently increased noticeably, which is caused primarily by aggravated environmental problems. In recent years, many cascade installations for commercial and industrial low-temperature cooling (t0 = - 50 °С) have been successfully put into operation. It should be kept in mind that in comparison with other refrigerants C02 has better thermophysical properties in this mode. This is chemically inert, fire and explosion-proof substance.
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##article.viewOnOriginalSite##About the authors
G. Renz
Bitzer Kuelmashinenbau GmbH
Author for correspondence.
Email: info@eco-vector.com
Research Department Head
GermanyReferences
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Fig. 1. Simplified scheme of cascade refrigeration unit: 1 - medium-temperature evaporators; 2 - low-temperature evaporators; 3 - CO2 compressor; 4 - intercascade heat exchanger: evaporator for NH3 and condenser for CO2; 5 - medium-temperature receiver; 6 - low-temperature receiver
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Fig. 2. Simplified scheme of cascade system with lower branch on CO2: K1-K6 - medium-temperature evaporators; F1-F3 - low-temperature CO2 evaporators
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Fig. 3. Comparison of boiling and condensing pressures within the standard operating range for CO2 and R22
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Fig. 4. Comparison of vapor density values within standard suction pressure ranges for CO2 and R22
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Fig. 5. Sectional view of a semi-hermetic piston compressor
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Fig. 6. Sectional view of a semi-hermetic screw compressor (without oil separator)
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Fig. 7. Diagram of CO2 mass flow rate variation depending on suction gas superheat at different boiling temperatures (condensing temperature - 10°С, superheat 10°С)
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Fig. 8. Kinematic viscosity of the mixture when dissolving CO2 in ROE oils
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Fig. 9. Boundaries of miscibility of CO2 with ROE oils and PAG oil at subcritical temperatures
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Fig. 10. Cooling capacity of a Bitzer screw compressor at a volumetric capacity of 220 m3/h
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Fig. 11. Relative cooling capacity at different boiling temperatures
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Fig. 12. Comparison of mass flow rates of different refrigerants in Bitzer screw compressor at volumetric capacity of 220 m3/h (condensing temperature -10 °С, superheating 10 °С)
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Fig. 13. Cascade refrigeration and freezing unit with piston compressors "Bitzer" [upper branch on R290 (propane), lower - on R744 (CO2)]
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