Film condensation heat transfer characteristics of R134a on horizontal stainless steel integral-fin tubes at low heat transfer rate

Condensation heat transfer characteristics of R134a on the integral-fin tubes are experimentally investigated. The test tubes are made of stainless steel, and the root diameter of the tubes is 13.27 mm. The height of fin is 1.19 mm, and the densities of the integral fin are 19 fpi and 26 fpi. The present tests were conducted at the saturation temperatures of 20 °C and 30 °C. The condensation heat transfer coefficients of the tubes having 19 fpi and 26 fpi at the saturation temperature of 20 °C are higher than that of the plain tube by 4.4 and 3.1 times, respectively. When the temperature difference across the condensate film is less than 0.7 °C, the enhancement of the tube of 19 fpi is much larger than that of the tube of 26 fpi. The Honda and Nozu model shows the smallest mean deviation between the estimated values and experimental results among the existing models.