This paper describes an analysis on the performances of a cascade refrigeration cycle operated with blends of carbon dioxide (CO2, or R744) and hydrofluorocarbons (HFC) as the low-temperature working fluid. The aim of this work was to study the possibility of using carbon dioxide mixtures in those applications where temperatures below CO 2 triple point (216.58 K) are needed. The analysis was carried out by developing a software based on the Carnahan–Starling–De Santis (CSD) equation of state (EoS) using binary interaction parameters derived from our experimental data. The properties of the investigated blends (R744/R125, R744/R41, R744/R32, R744/R23) were used to simulate the behavior of a cascade cycle using ammonia (R717) as the high-temperature-circuit working fluid and operating at evaporating temperatures down to K70 8C. The use of a suction–liquid heat exchanger on the low-temperature side of the circuit was also investigated. Results show that the R744 blends are an attractive option for the low-temperature circuit of cascade systems operating at temperatures approaching 200 K.

Blends of carbon dioxide and HFCs as working fluids for the low-temperature cir-cuit in cascade refrigerating systems / DI NICOLA, Giovanni; Giuliani, G.; Polonara, Fabio; Stryjek, R.. - In: INTERNATIONAL JOURNAL OF REFRIGERATION. - ISSN 0140-7007. - 28:(2005), pp. 130-140. [10.1016/j.ijrefrig.2004.06.014]

Blends of carbon dioxide and HFCs as working fluids for the low-temperature cir-cuit in cascade refrigerating systems

DI NICOLA, Giovanni;POLONARA, FABIO;
2005-01-01

Abstract

This paper describes an analysis on the performances of a cascade refrigeration cycle operated with blends of carbon dioxide (CO2, or R744) and hydrofluorocarbons (HFC) as the low-temperature working fluid. The aim of this work was to study the possibility of using carbon dioxide mixtures in those applications where temperatures below CO 2 triple point (216.58 K) are needed. The analysis was carried out by developing a software based on the Carnahan–Starling–De Santis (CSD) equation of state (EoS) using binary interaction parameters derived from our experimental data. The properties of the investigated blends (R744/R125, R744/R41, R744/R32, R744/R23) were used to simulate the behavior of a cascade cycle using ammonia (R717) as the high-temperature-circuit working fluid and operating at evaporating temperatures down to K70 8C. The use of a suction–liquid heat exchanger on the low-temperature side of the circuit was also investigated. Results show that the R744 blends are an attractive option for the low-temperature circuit of cascade systems operating at temperatures approaching 200 K.
2005
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11566/52710
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