Study of steady-state heat transfer of pool boiling in saturated liquid helium at atmospheric pressure.

Abstract

Effects of surface inclination and roughness on saturated pool boiling curve were experimentally established for atmospheric liquid-helium. Based on the measured boiling curves, the following results were obtained. In nucleate boiling, heat transfer coefficients are increased as either the surface inclination or the roughness is increased. As for film boiling on vertical and inclined surfaces, the so-called two-phase boundary layer model underestimates heat transfer coefficients but it can correctly estimate the effects of surface superheat and surface inclination. This result indicates that a vapor film of laminar, smooth-interface is restricted to a small distance from the leading edge of the vapor film, but the nature of the vapor film remains laminar irrespective of the distance from the leading edge. Critical heat flux is not dependent on surface roughness and its dependency on surface inclination is predicted well by Vishnev's correlation. Finally, the minimum-heat-flux point temperature is not affected by surface roughness and inclination.