Three dimensional heat transfer characteristics of superfluid helium and its mechanism

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Major Results of this study are as follows.1) Steady-state heat transfer and its critical heat flux on a flat plate of various dimensions in He II were measured under wide ranges of experimental conditions. Effect of the test plate dimension was clarified and an equation which can describe the experimental data was presented.2) To investigate the mechanismof heat transfer in case of expanding or shrinkingheat flow from a heated surface in He II, measurements of heat transfer were made for the following cases : (1) the heat flow expands from a test plate located at one end of a rectangular ductcontaining He II with the cross sectional area larger than the surface area of the test plate to the other open end of the duct, (2) for a duct with a sudden increase in its cross sectional area, (3) for a duct with an orifice.3) Moreover, the measurements were made for a duct with the heated surface located on the wall at the middle of the duct and heat flowed turning to both open ends of the duc … More t. Effect of the gap length from the test heater to the opposite wall was clarified. Equations that can express the experimental data of 2) and 3) were given.4) Transient heat transfer from a test plate produced by a step heat input with the height higher than the steady-state critical heat flux was measured for the above mentioned cases of (2), (3) and (4). The transient heat transfer for a stepwise heat input is such that the quasi-steady state exists with a certain lifetime on the extrapolationof steady-stateKapitza conductance curve and then jumps to film boiling regime. Effects of expansion or sublimation of heat flow on the relation of the lifetime and step height was clarified.5) The computer code of two-dimensional heat and fluid flow in He II named SUPER-2D was developed based on the two-fluid model for He II in turbulent flow condition. The numerical solutions of the steady-state critical heat flux and transient heat transfer produced by a step heat input are in good agreement with the experimental data for the corresponding conditions. It was confirmed that the numerical code can describe the steady-state and transient heat transfer phenomena in He II. Mechanism of two-dimensional heat transfer in He II was clarified through the calculation Less