Effects of varying oblique angles on flow boiling heat transfer and pressure characteristics in oblique-finned microchannels

Flow boiling experiments are conducted in oblique-finned microchannels with different oblique angles to investigate its effects on two-phase heat transfer, pressure drop and instabilities. These studies are carried out with FC-72 dielectric fluid at three different oblique angles of 10°, 30° and 50°. Three mass fluxes ranging from 194 kg/m2 s to 386 kg/m2 s, and effective heat fluxes from 14.9 W/cm2 to 70.0 W/cm2 are tested with high-speed flow visualisations to explore the physical boiling phenomenon in the microchannels. Results show that heat transfer performance increases with oblique angles from 10° to 50° due to the increase in secondary channels which promote flow mixing. This causes an increase in pressure drop from 10° to 30° oblique angles due to the increase in flow separation and flow diversion. Pressure drop, however, is almost negligible when the oblique angles are increased from 30° to 50°. As a result, the 50° oblique-finned microchannels presents an attractive option for further parametric studies.