Flow and Heat Transfer Characteristics of $CO_2$/Oil Mixtures in a Circular Tube

  • Kang, Byung-Ha (School of Mechanical and Automotive Engineering, Kookmin University) ;
  • Lim, Dong-Seop (Graduate School of Mechanical Engineering, Kookmin University)
  • 발행 : 2008.12.31


The present study is directed at flow and heat transfer of $CO_2$ and oil mixtures in a circular tube. PAG and POE oils are considered in this study. Flow characteristics of $CO_2$ and oil mixtures have been investigated by flow visualization. Pressure drop has been measured in the range of operating mass flow rate from 0.1 to 0.4 kg/min in a circular tube. Heat transfer characteristics of $CO_2$/oil mixtures have been investigated using a counterflow heat exchanger. In case of pure liquid $CO_2$ as well as $CO_2$ and POE mixtures, flow are seen to be uniform so that $CO_2$ and POE oil are still miscible even at flowing state. However, it is found that $CO_2$ and PAG are not miscible. Pressure drop of $CO_2$/PAG mixtures are much higher than that of $CO_2$/POE mixtures as well as pure $CO_2$ at a fixed mass flow rate. As the concentration of POE oil is increased from 0 to 5 wt%, pressure drop is increased. However, heat transfer rate and heat transfer coefficient of $CO_2$/POE mixtures are much higher than that of $CO_2$/PAG mixtures. The f-factor correlation and Nusselt number correlation for $CO_2$/POE oil mixtures are suggested in this paper.



  1. Clodic, D., 2008, Latest HVAC&R Development Trends in European Response to Imminent HFC Regulations, Plenary Session, Proc. 12th International Refrigeration Conference at Purdue, West Lafayette, USA
  2. Lee, J. H. and Park, Y. M., 2002, Vapor Pressure and Miscibility for R404A/POE Oil Mixtures, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 14, No. 4, pp.285-292
  3. Lim, T. W. and Kim, J. H., 2003, A Study on Pressure Drop in Two-Phase Flow Boiling of Refrigerants in Horizontal Tube, Korean Journal of Air- Conditioning and Refrigeration Engineering, Vol. 15, No. 6, pp. 510-517
  4. Mori, K., Onishi, J., Shimaoka, H., Nakanishi, S., and Kimoto H., 2002, Cooling Heat Transfer Characteristics of CO2 and CO2-Oil Mixtures at Supercritical Pressure Conditions, Proceeding of the Asian Conference on Refrigeration and Air Conditioning 2002, pp. 81-86
  5. Choi, H. S., Kang, B. H., Park, K. K., and Kim, S. H., 2004, An Experimental Study on Miscibility and Vapor Pressure of R-744/Oil Mixtures, Korean Journal of Air- Conditioning and Refrigeration Engineering, Vol. 16, No. 2, pp. 150-157
  6. Coutinho, J. A. P., Joergensen, M., and Stenby, E. H., 1995, Predictions of three-phase regions in CO2- oil mixtures, Journal of Petroleum Science & Engineering, Vol. 12, No. 3, pp.201-208 https://doi.org/10.1016/0920-4105(94)00044-5
  7. Zingerli, A. and Groll, E. A., 2000, Influence of Refrigeration Oil on the Heat Transfer and Pressure Drop of Supercritical $CO_2$ during In-Tube Cooling, IIF-IIR Commission B1,B2,E1 and E2, Purdue Univ., USA-2000, pp. 269-278
  8. Munson, B. R., Young, D. F., and Okiishi, T. H., Fundamentals of Fluid Mechanics, 2nd Edition, Wiley, New York, 1997, pp. 552-575
  9. William, S. J., Engineering Heat Transfer, 2nd Edition, CRC Press, New York, 2000, pp. 461-466