Condensation of refrigerants on horizontal tubes-characteristics of vapor shear controlled regime.

Abstract

Heat transfer measurements and flow visualization studies are reported for condensation of R 113 at near atmospheric pressure on single horizontal tubes of 8.0 mm and 19.0 mm in outer diameter with vertical vapor downflow. The vapor ranged from 0.34 m/s to 15.6m/s, and the condensation temperature difference from 3.1 K to 32.3 K. The slow of condensate was visualized by injecting a dye tracer into the condensate film. The film showed the inception of waves and the change of wave pattern with the increase of vapor velocity. In the three dimensional wave regime the film showed an abrupt change of thickness at an angular position somewhat lower than the tube axis. The heat transfer results are compared with available experimental data and with theory. Empirical equations for the average heat transfer coefficient based on the equivalent Reynolds number concept are proposed for the vapor shear controlled regime.