Boiling heat transfer characteristics with highly wettable heated surface under forced convection conditions

Abstract

Under forced convection and atmospheric pressure conditions, heat transfer characteristics were studied using an annulus channel of a heater rod with highly-wettable surface. Improvement of phase change heat transfer under boiling and condensation process requires that either liquid heated or vapor cooled can contact a heat transfer surface effectively, but either a vapor layer or a liquid film can be formed repeatedly on the surface during boiling and condensation processes. As oxide semiconductor materials are known to be highly wettable, TiO2 was coated on a heater rod surface. The Leidenfrost temperature for the TiO2 coated surface was higher than that for the uncoated surface. Under mass flux conditions from 600 to 1700kg/m2s, the heater rod surface temperature at variable power conditions was measured. A higher heat flux at the point where the forced convection vaporization started and a larger critical heat flux were observed for the TiO2 coated surface than that for the uncoated surface.