Three dimensional heat transfer characteristics of superfluid helium and its mechanism

本研究的主要结果如下：1)在较宽的实验条件下，测量了He II中不同尺寸平板的稳态传热及其临界热流密度。阐明了试验板尺寸对试验结果的影响，并给出了描述试验数据的方程。2)调查发病传热的扩大或shrinkingheat流从他二世,加热表面的测量传热为下列情形:(1)热流从测试扩展板位于一个矩形的一端ductcontaining他二横截面积比表面积测试其他开放的管板,(2)管突然增加的横截面积,(3)管孔。3)此外，测量了一个管道，受热面位于管道中间的墙壁上，热量流向管道的两个开口端。更多t.澄清了从测试加热器到对面墙壁的间隙长度的影响。给出了可以表示2)和3)实验数据的方程。(4)在上述(2)、(3)、(4)的情况下，测量了高度高于稳态临界热流密度的阶跃热输入所产生的测试板的瞬态换热。阶阶热输入的瞬态换热是这样的：准稳态存在并具有一定的寿命，然后跃迁到膜沸腾状态。阐明了热流膨胀和升华对寿命和台阶高度关系的影响。5)基于He II紊流条件下的双流体模型，开发了He II的二维热流计算机代码SUPER-2D。阶跃热输入产生的稳态临界热流密度和瞬态传热的数值解与相应条件下的实验数据吻合较好。结果表明，该数值代码可以描述He II的稳态和瞬态传热现象。通过计算，阐明了He II的二维换热机理

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