Steady state heat transfer of an oxidized copper surface in subcooled liquid helium

Steady state heat transfer of an oxidized copper surface was measured in subcooled liquid helium (LHe). The heat transfer surface is 20 mm in diameter and faced upward. Chemical oxidation was treated on the surface by the same method which was applied to the superconductor for the helical coil of the large helical device (LHD). To research the temperature dependence of heat transfer characteristics, LHe was subcooled at 4.2, 3.8, 3.4, 3.0 and 2.7 K using a superfluid helium (He II) cryostat. In the range of these temperatures, critical heat flux (CHF) is monotonically decreased as increasing the temperature of the subcooled LHe; and minimum heat flux (MHF) slightly depends on the temperature. In this paper, the heat transfer characteristics of the oxidized surface are discussed compared with those of copper surfaces from other studies.