Heat transfer to subcooled Helium II

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In this research, (1) the improvement of the performance of experimental apparatus has been attempted and (2) the experiment of steady heat transfer to subcooled Helium II has been performed.Results are as follows.(1) The insert which consists of heat exchangers and the lambda-plate separating the Helium I bath and Helium II bath has been manufactured. It has been investigated since last year if subcooled helium II could be produced steadily. A lower bath-temperature of subcooled helium II of Tb=1.72 [K] -1.75 [K] at P=0.1044 [Mpa] was attained. It took about one hour to attain the condition of the above-mentioned subcooled Helium II from the beginning of evacuating He I in saturated Helium II bath.(2) The steady heat transfer characteristics to subcooled Helium II have been investigated using Rh-Fe temperature sensors and Pt-Rh wire as the temperature sensors and the heating surfaces at the same time. The heat transfer characteristics to subcooled He II in increasing heat flux and vertical orientation was obtained for Rh-Fe temperature sensors. It was found that the temperature of heating surface for these sensors were higher than that of Au-Mn [0.25%] wire (dia.=0.08 [mm], Tb=2 [k]) by M.Shiotsu et al.. The heat transfer characteristics to subcooled He II in increasing/decreasing heat fluxes and horizontal were also obtained for Pt-Rh wire. The temperature of heating surface for Pt-Rh wire was also higher than those using Au-Mn wire by M.Shiotsu et al. and Rh-Fe wire (dia.=0.051 [mm], Tb=1.85 [K]) by I.Arend et al. and it became higher for smaller diameter of the wires.