Critical heat flux of a two-phase closed thermosyphon with fins

The critical heat fluxes (CHFs) of two-phase closed thermosyphons with and without fins were studied. The thermosyphons were fabricated using 1.25-mm-thick iron tubes with inner diameters of 16, 21 and 26 mm. The lengths of the evaporator, adiabatic, and condensation sections were 20, 10 and 20 cm, respectively. Pure water, ethanol, and R134a refrigerant were used as the working fluids with 50 % filling rate of the evaporation length. CHF data when using fins of different thicknesses (1.0, 1.5 and 2.0 mm), radii (5, 10 and 15 mm), and spacing (10, 20 and 30 mm) were recorded. The CHF increased with the fin thickness and radius but decreased with the increase in fin spacing. In addition, the CHF increased with the diameter of the thermosyphon tube. Overall, the CHF of thermosyphons with fins was higher than that of thermosyphons without fins regardless of the working fluid.