New models for heat transfer and pressure drop during flow boiling of R407C and R410A in a horizontal microfin tube

The heat transfer of R407C and the pressure drop of R407C and R410A during flow boiling in a horizontal microfin tube were investigated. The measurements were conducted at saturation temperatures between -30 and +10 degrees C. The heat flux was varied between 1000 and 20,000 W/m(2). The mass flux amounted to 25-300 kg/s m(2) and the vapor quality was between 0.1 and 1.0. The microfin tube is made of copper with a total fin number of 55 and a helix angle of 15. The fin height is 0.24 mm and the inner tube diameter at fin root is 8.95 mm. The test tube is 1 m long. It is heated electrically. A total number of 1614 heat transfer measurements and 952 pressure drop measurements was conducted. A new method for deriving correlations is shown. With this new method a new correlation for the Nusselt number is being derived. The mean deviation of the calculated from the measured values is 9.8%. Within the range of +/- 30% there are 94.2% of the measured values. A new correlation for the total pressure drop is derived. The mean deviation of the calculated from the measured values is 18.1%. Within the range of +/- 30% there are 83.1% of the measured values. (C) 2016 Elsevier Masson SAS. All rights reserved.