Effect of Fin Tip Radius for Film Condensation on Micro-Fin Surfaces

This study provides an experimental analysis for condensation heat transfer of refrigerant R-134a on one plain surface plate and two micro-fin surface plates with fin tip radius of 4.5 and 70 μm. Each plate was tested at three different orientations with heat transfer surface upward, downward, and vertical. The test results on vertical plain surface agree very well with those predicted by the Nusselt equation [1916] and Kutateladze correlation [1963] at low Reynolds number and high Reynolds number conditions, respectively. The test results show no significant difference in condensation heat transfer coefficients on upward and downward, plain and micro-fin plates surfaces because all surfaces were covered by thick condensate film. However, for the vertical surfaces test, part of the microfin surface was not immersed in liquid condensate film. Surface tension force acted on the fin tip to pull down the condensate to the valley of the fins and enhanced condensation heat transfer. This result provides a further understanding that the fin tip radius plays an important role in condensation heat transferfi.