抄録
Steady and transient heat transfer from a horizontal surface to liquid helium was measured from convection to film boiling region at bulk liquid temperatures between 2.5 and 5.1K. The test copper cylinder was insulated with vacuum, except the flat heat transfer surface of 20mm in diameter. The influence of four different surface treatment, three kinds of finish and coating over the same copper sample on maximum heat flux was also investigated in the pressure range of 0.046<P/Pc<0.92 corresponding to the temperature from 2.5 to 5.1K.
Experimental results obtained in the developed nucleate boiling region shifted to larger ΔT value than the reported data compared at the same heat flux and nucleate boiling data were correlated with a modified Rohsenow equation. The film boiling data were correlated well with Rayleigh number and Nusselt number based upon Laplace reference length. Three kinds of dynamic temperature variation were noted corresponding to three boiling regions for the step change of heat input. The peak of the maximum heat flux curves shifted toward 0.5Pc for the two more rough sufaces. Maximum heat flux was found to decrease with surface coating for the polished surface.
