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Flow boiling heat transfer characteristics of carbon dioxide in horizontal micro-fin tubes.

Author(s) : KUWAHARA K., HIGASHIIUE S., KOYAMA S.

Summary

From the viewpoint of global warming protection, working fluid for refrigerators, air-conditioners and heat pumps are making the shift to natural refrigerants in place of halogenated hydrocarbons. Among the natural refrigerants, carbon dioxide (CO2) is non-toxic, non-flammable and has a low GWP. Therefore, CO2 has been proposed as a working fluid for various types of refrigeration systems. It is then important to clarify in-tube heat transfer characteristics of CO2 in order to develop the designing method for heat exchangers. It is also required to improve the performance of heat exchanger by using micro-fin tubes. Most of investigations on CO2 heat transfer, however, have been performed for that of smooth tube. In this study the flow boiling heat transfer characteristics of CO2 is measured using five types of spirally grooved micro-fin copper tubes. Experiments were carried out at 3, 4 and 5 MPa in pressure at mass velocity varying from 135 to 650 kg/m2.s. The previous correlation for smooth tubes was modified based on the present experimental results, which is taking account of the effect of grooves and larger nucleate boiling of micro-fin tubes on the forced convection term and the nucleate boiling term, respectively. The modified correlation for flow boiling of CO2 in the micro-fin tubes predicted almost all of measured data within ±30%.

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Pages: 2009-5

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Details

  • Original title: Flow boiling heat transfer characteristics of carbon dioxide in horizontal micro-fin tubes.
  • Record ID : 2009-1982
  • Languages: English
  • Source: 3rd Conference on Thermophysical Properties and Transfer Processes of Refrigerants
  • Publication date: 2009/06/23

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