Experimental study on R410A flow boiling heat transfer outside three enhanced tubes with different fin structures

In order to further explore the influence of the outer fin structure on flow boiling heat transfer, the refrigerant R410A was used to conduct flow boiling heat transfer experiments outside three kinds of enhanced tubes with different outer fin structures (including micro-porous, integral-fin, and independent small bosses structures). The outer diameter of the tubes is 19.05 mm with a mass flux range of 50 kg/m2 s–80 kg/m2 s, and the inlet and outlet vapor quality is maintained at 0.2 and 0.8, respectively. The micro-porous tube showed the best heat transfer performance in the test conditions (the heat transfer coefficient is about 2.52–2.64 times of that of the smooth tube), and the next is the integral-fin tube. Due to local evaporation to dryness, the performance of the independent small bosses tube is inferior to that of the smooth tube. In addition, the heat transfer characteristics of the micro-porous tube under different average vapor qualities were tested and analyzed. Finally, the heat transfer coefficient of the tested tubes can be accurately predicted by modified correlations in the deviation of ±10%.