Abstract
Film condensation of downward flowing R-113 vapour at near atmospheric pressure on single horizontal tubes was studied experimentally over wide ranges of vapour velocity and condensation temperature difference. The flow of condensate was visualized by injecting a dye tracer. Three flow regimes : smooth surface, two-dimensional waves and three-dimensional waves, were observed. In the last flow regime an abrupt thickening of the condensate film was seen at an angular position about 1.75 rad from the tube top. Turbulent mixing of condensate was observed in the thick film region. The present and earlier heat transfer results for R-113 and R-21 were compared with the laminar two-phase boundary-layer theory. The point at deviation from the theoretical prediction was found to be dependent on a dimensionless number which gave a transition criterion between smooth and wavy condensate surfaces. A correlation equation for the average heat transfer coefficient is proposed, where an equivalent Reynolds number is introduced for the high vapour velocity region.
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