Experimental study on film condensation characteristics at liquid nitrogen temperatures

The understanding of cryogenic condensation mechanisms is insufficient mainly due to the difficulties of modeling and direct measurement, especially when the condensate film is in the wavy laminar flow regime. In this work, we designed a condensation testbed to measure the key heat transfer parameters at liquid nitrogen temperatures within a large range of flow regime. It is the first time to extend the cryogenic condensation data to the film Reynolds number (Reδ) as high as 1151. The applicability of Kutateladze's correlation (Kutateladze, 1963) to cryogenic fluids is verified. Moreover, the condensate flow pattern is collected by a high-speed camera. The obvious large interfacial waves are found to occur after Reδ reaches 343 and the accompanied disturbances enhance the cryogenic condensation heat transfer significantly. The large interfacial waves are gravity dominated while the small interfacial waves are determined by both surface tension and gravity. A correlation between the dimensionless interfacial wave velocity and Reδ is further developed with the accuracy of ±20% for 82% of the data. The quantified study on the wavelength, velocity and frequency of the cryogenic interfacial wave will offer the insights of the interfacial instability enhancement mechanism on the cryogenic condensation heat transfer.