Effect of longitudinal micro fin tube enhancement in evaporation of R410A

An experimental investigation of evaporating heat transfer was conducted for smooth and coaxial micro-finned aluminum tubes with an internal diameter of 6.3 mm. The study used R410A at a saturation temperature of 10 °C running at mass fluxes from 100 to 250 kg/m2-s, heat fluxes from 4 to 14 kW/m2, and qualities from 0.1 to 0.8. The testing facility had a 15 cm long test section heated by a secondary heated water loop, a transparent visualization section which used a high-speed camera to capture flow regimes, and vertical and horizontal pressure drop test sections. The micro-finned enhancement factors were 1.14-1.85, 0.91-1.72, and 1.05-1.66 for heat fluxes of 4, 9 and 14 kW/m2 correspondingly. Calculations for the finned tube used the molten diameter surface. Flow regimes were similar for both tubes, except for qualities tested, and the regimes were correctly predicted by Cheng et al. (2008). Images of the flow regimes were captured for each testing quality and for mass fluxes. Pressure drop in the micro-finned tube was higher than the smooth tube for both horizontal and vertical tube orientations. The difference in pressure drop increased with higher vapor quality