Convective Condensation of R410A in Micro-Fin Tubes

An experimental investigation was performed for convective condensation ofR410A inside five micro-fin tubes with the same outer diameter of 5 mm and helix angle of 18°. Data are for mass fluxes ranging from about 180 to 650 kg/m2 s. The nominal saturation temperature is 320 K, with inlet and outlet qualities of 0.8 and 0.1, respectively. The results suggest that tube 4 has the best thermal performance for its largest condensation heat-transfer coefficient and relatively low pressure-drop penalty. The heat-transfer enhancement mechanism is mainly due to the surface area increase over the plain tube at large mass fluxes, while liquid drainage and interfacial turbulence play important roles in heat-transfer enhancement at low mass fluxes. In addition, the experimental data were analyzed using seven existing pressure-drop and four heat-transfer models to verify their respective accuracies.