Summary
Heat rejection from CO2 flow near the critical point, where commercial refrigerators spend most of their operating hours, was investigated in this study. Experimental results on the heat transfer coefficient and pressure drop of mass flux from 100 to 240 kg/m2.s at pressures from 5 to 7.5 MPa in a horizontal smooth tube of 6.1 mm inner diameter are provided and compared with correlations. The heat rejection process below critical pressure was categorized into superheat, two-phase, and subcool zones in which the bulk-mean temperature was superheated, saturated, and subcooled, respectively. The results indicated that the heat transfer coefficient in superheat zone is significantly higher than correlations proposed for single-phase turbulent flow, and the condensation was identified from the tube wall temperature below saturation temperature. This superheat zone accounts for a significant portion of the heat rejected in the subcritical cycle and affects on condenser sizing.
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Details
- Original title: Heat rejection from R744 flow under uniform temperature cooling in a horizontal smooth tube around the critical point.
- Record ID : 2011-0032
- Languages: English
- Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 34 - n. 3
- Publication date: 2011/05
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Indexing
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Themes:
Heat transfer;
CO2 - Keywords: Horizontal tube; Heat transfer; Critical point; Refrigerant; CO2
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Excellent heat rejection from CO2 near the crit...
- Author(s) : KONDOU C., HRNJAK P.
- Date : 2010/06/13
- Languages : English
- Source: IIR/Eurotherm sustainable refrigeration and heat pump technology conference. Proceedings of the Eurotherm Seminar No. 88, Stockholm, Sweden, June 13-16, 2010.
- Formats : PDF
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Heat transfer to supercritical carbon dioxide i...
- Author(s) : WALISCH T., TREPP C.
- Date : 1997/10/02
- Languages : English
- Source: Compression systems with natural working fluids. International R&D on heat pump, air conditioning and refrigerating systems. Workshop proceedings.
View record
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Heat rejection from R744 near the critical point.
- Author(s) : KONDOU C., HRNJAK P.
- Date : 2010/12
- Languages : English
- Source: 2010 Purdue Conferences. 13th International Refrigeration and Air-Conditioning Conference at Purdue.
- Formats : PDF
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Heat transfer and various convection structures...
- Author(s) : CHEN L., ZHANG X. R.
- Date : 2014/11
- Languages : English
- Source: Applied Thermal Engineering - vol. 72 - n. 1
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Preliminary experimental results of CO2 gas-coo...
- Author(s) : HASHIMOTO K., SAIKAWA M.
- Date : 1997/11/06
- Languages : English
- Source: Heat transfer issues in "natural" refrigerants. International conference.
- Formats : PDF
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