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

Abstract

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 °C. The heat flux was varied between 1000 and 20,000 W/m2. The mass flux amounted to 25–300 kg/s m2 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.