Effect of oil on heat transfer and pressure drop of R744 in 6.1 mm horizontal smooth tube.

Number: pap. n. R27, 2438



This paper presents experimentally determined flow boiling heat transfer coefficients and horizontal pressure drop for R744/oil mixtures in horizontal, smooth, 6.1 mm inner diameter, copper tube. experiments were carried out at saturation temperatures of -15°C, and -30°C, mass fluxes between 100 and 400 kg/m2s, heat fluxes ranging from 2 to 15 kW/m2, inlet vapor qualities from 0.1 to 0.8, and oil circulation ratio from 0.5 to 2%. The effect of miscible POE oil was evaluated by comparing results of R744/oil mixture with pure R744 experimental data from Park and Hrnjak (2006, 2007), who used the same experimental facility. The results show that flow boiling heat transfer coefficient of pure R744 and R744/ oil mixture at various oil circulation ratio increase when heat and mass fluxes increase. While the main heat transfer mechanism is nucleate boiling, convective boiling becomes increasingly important with increasing of mass fluxes both for pure R744 and R744/oil. Increasing oil circulation ratio generally initiates a gradual decrease in heat transfer coefficient and not affected pressure drop significantly..

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  • Original title: Effect of oil on heat transfer and pressure drop of R744 in 6.1 mm horizontal smooth tube.
  • Record ID : 30000998
  • Languages: English
  • Source: 2010 Purdue Conferences. 13th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2010/07/12


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