Evaporating and condensing heat transfer coefficients in R134a and R410 filled thermosyphon at low temperatures.

K. S. Ong, Alex Tung, Tan A. H., Proc. 9IHPS, 2008

An experimental investigation on the performance of a two phase thermosyphon at evaporator temperatures below 70oC was conducted. The thermosyphon was filled alternately with R134a and R410. The evaporator section was heated by resistance band heaters. The condenser was a concentric pipe water-cooled jacket. Experiments were carried out with R134a at fill ratios of 0.5 and 0.7 and with R410 at fill ratio of 0.5 at various angels of inclination of the thermosyphon from 45o – 90o. Evaporator power input varied from 100 - 500W. In order to maintain uniform cooling at the condenser section, coolant mass flow rate was kept as high as possible. Mean condensing and evaporating heat transfer coefficients were determined experimentally. The overall thermal resistance for the present thermosyphon was found to be about 0.060 K/W for both R134a and R410.