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CO2 flow boiling heat transfer evaluation and visualization in a horizontal round tube with and without oil at low temperatures.

Number: 1101

Author(s) : ZHAO H., LI X., TANG K., HATTORI K., MUGABI N., ELBEL S.

Summary

This paper investigates CO2 flow behavior in a smooth 7.9mm horizontal copper tube with and without oil at low evaporation temperatures (< -10°C). Heat transfer coefficients and pressure drop are measured at different evaporating temperatures, -10°C, -20°C, and -35°C at a mass flux of 150 kg/(s-m2) and heat flux of 5kW/m2. Flow visualization is conducted to study flow regimes. Test results with different oil concentrations in the refrigerant (1% and 5% OCRs) are compared with the performance data without oil. Test results with the low oil concentration of 1% OCR show little impact on both heat transfer and pressure drop in the two-phase flow region compared to the no-oil condition. Increasing oil concentration to 5% OCR leads to large changes in both heat transfer and pressure drop at all temperature conditions. A general trend of increased HTC and pressure drop is observed when compared to the no-oil and 1% OCR conditions.

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Pages: 9 p.

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Details

  • Original title: CO2 flow boiling heat transfer evaluation and visualization in a horizontal round tube with and without oil at low temperatures.
  • Record ID : 30032641
  • Languages: English
  • Source: 16th IIR-Gustav Lorentzen Conference on Natural Refrigerants (GL2024). Proceedings. University of Maryland, College Park, Maryland, USA, August 11-14 2024
  • Publication date: 2024/08
  • DOI: http://dx.doi.org/10.18462/iir.gl2024.1101

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