DEVELOPMENT OF A NEW COOLING DESIGN DATABASE FOR SUPERCONDUCTING MAGNETS OF FUSION EXPERIMENTAL FACILITY

在较宽的实验条件范围内，对直径0.08~1.2 mm的单根水平钢丝的稳态和非稳态换热特性进行了实验和理论研究，建立了新的二维冷却设计数据库。主要研究成果如下：1.研制了特殊合金(Au-Mn，0.9原子%；铂-钴，0.5原子%)制成的试验筒，该试验筒与电阻温度计相结合。系统地研究了饱和和过冷条件下的稳态换热和阶跃热输入引起的非稳态换热。结果1)稳态换热结果饱和条件下He II中的临界热流密度与主体液体温度和液头有关，H：对于固定的液体温度，液头越高，临界热流密度越大，对于固定的液体…，临界热流密度越大从波长点开始，随着液体温度的降低，更多的水头增加。当液体温度在2K左右时，它有一个最大值，并随着液体温度的进一步降低而逐渐减小。给出了基于Gorter-Mellink方程解的CHF关联式。这个关联式是基于这样的假设，即钢丝附近的液体由于钢丝表面的压力P_L(=P+RhogH)而最初处于过冷状态时，其临界热流密度已达到波长温度的饱和温度。结果表明，该关联式可以在较宽的工况范围内(压力、液体过冷度和圆筒直径)预测CHF。2)膜沸腾换热理论建立了水平圆筒的气膜沸腾换热理论关联式。无论是作者的实验数据，还是其他工作人员对不同圆柱体直径的实验数据，都与理论值相吻合。3.阶跃热输入引起的非稳态换热首先由作者阐明，当实验圆柱体受到高度高于稳态临界热流密度的阶跃热输入时，根据稳态Kapitza电导曲线的外推，准稳态持续一段时间，然后跳跃到膜沸腾。在较宽的压力、液体过冷度和圆柱体直径范围内的实验结果基础上，提出了一个可以估算不同热输入波形下准稳态寿命的通用关联式。在此基础上，给出了磁体绕组的绝对稳定极限。较少

Steady and unsteady heat transfer characteristics on single horizontal wires with the diameters ranged over 0.08 to 1.2 mm were studied experimentally and theoretically for wide ranges of experimental conditions to develop a new two dimensional cooling design database. Major results are as follows :1.Development of Test Cylinders Made of Special AlloyTest cylinders made of special alloys (Au-Mn, 0.9 atomic % ; Pt-Co, 0.5 atomic %) were developed to use the iestcylinder as well as the resistance thermometer. Steady-state heat transfer and unsteady heat tranfer caused by step heat input under saturated and subcooled conditions were obtained systematically by using these cylinders with the diameters ranged over 0.08 to 1.2 mm.2.Steady-state Heat Transfer Resultsa)Critical Heat Flux (CHF)The CHF in He II under saturated conditions are dependent on bulk liquid temperature and liquid head, H : for a fixed liquid temperature, CHF is higher for higher liquid, head, and that for a fixed liquid … More head increases with decreasing liuqid temperature from lambda point. It has a maximum at liquid tempreture of around 2 K and gradually decreases with further decreasing liquid temperature. The authors have presented the CHF correlation based on the solution for Gorter-Mellink equations. This correlation was based on the assumptions that the critical heat flux was determined by the condition that liquid in the vicintiy of the wire which was initially under a subcooled conditon due to pressure P_L(=P+rhogH) at the wire surface had reached the saturation temperature of lambda temperature. It was confirmed that this correlation predicts the CHF under wide range of conditions (pressure, liquid subcooling and cylinder diameter).b)Film Boiling Heat TransferTheoretical film boiling heat transfer correlation for horizontal cylinder was presented. Not only the experimental data by the authors but also the data by other workers for different cylinder diameters are in agreement with the theoretical values.3.Unsteady Heat Tranfer caused by Step Heat InputIt was first clarified by the authors that, when the stepwise heat input with the height higher than that corresponding to the steady-state critical heat flux is given to the test cylinder, quasi-steady state last a period of time on the extrapolation of steady-state Kapitza conductance curve and then jumps to film boiling. A general correlation which can evaluate the lifetime of the quasi-steady state for various wave for of the heat inputs was presented based on the experimental results for wide ranges of pressure, liquid subcooling and cylinder diameter. An absolute stability limit for magnet windings was given based on the correlation. Less