The motion of boiling nitrogen (LN2) and its surface profile between parallel plate electrodes and the behavior of bubbles in a nonuniform electric field in a microgravity environment are observed. The dynamic behavior is analyzed in consideration of the following forces: the Maxwell stress, gradient force, buoyancy, capillary force (surface tension), and viscosity. This behavior is explained consistently by a theory that includes these forces. It is confirmed that the liquid in a uniform electric field is driven by the Maxwell stress and that the bubbles in a nonuniform electric field are driven by the gradient force.
“IEV Chapter 815: Superconductivity, ” which will be the international standard of the glossary of terms relating to superconductors, is now in the stage of Committee Draft for Vote (CDV). This activity to prepare Chapter 815 of IEV (International Electrotechnical Vocabularies) is being carried out through the collaboration of IEC/TC90/WG1 and IEC/TC1. In Chapter 815, a total of 300 terms and their definitions are classified into eight sections and placed in logical order. They will be used in the international standards of test methods that are now being prepared by IEC/TC90 and in future international standards of materials and their applications in the field of superconductivity. The contents and the history of IEV Chapter 815 are discussed.
JAERI has developed 50kA current leads for the International Thermonuclear Experimental Reactor (ITER). The Center Solenoid (CS) Model Coil program is under way by means of international collaboration in ITER-EDA. The CS model coil is being developed for ITER CS coil and is for demonstration for ITER construction. The performance test of the CS model coil will be carried out at the JAERI ITER common test facility (CTF). The current lead consists of the vertical lead and the connection lead. The vertical lead is a vapor-cooled type and has a cable-in-conduit geometry. The vertical lead was designed with a heat leak of 1.2W/kA at a helium flow rate of 0.06g/(s·kA). The measured heat leak satisfied the designed value. The connection lead was made from copper pipe soldered with NbTi supreconducting wires. The pipe was stabilized by the supreconducting wires and a cooling channel. The current lead was operated up to 60kA. The design and the performance test results of 50kA current leads are reported. The results meet the specifications for the CS model coil test and for the ITER real machine.
Heat transfer characteristics in a pressurized He II channel, including a copper wall, were investigated experimentally and numerically. Temperature distributions in the channel and the wall were measured when the copper wall was heated. It was confirmed that the wall temperature increased remarkably in occurrences of a phase transition of helium in the channel. The value of stored energy in the copper wall when its upper or lower portion are heated locally are smaller than when the center portion of the wall is heated locally. Heat conduction through the copper heat transfer across interfaces (Kapitza conductance) and heat transport by internal convection of He II were all considered in the present two-dimensional time dependent numerical analyses. The numerical results were in qualitative agreement with the experimental results when the channel was filled with He II.
In a 4K regenerative refrigerator, high heat-exchange effectiveness in the regenerator is an important factor for improving the refrigeration capacity. The heat capacity of magnetic regenerative materials in the regenerator must be larger than that of pressurized He gas. However, the heat capacity curve of a single magnetic material is sharper in comparison with that of He gas. To obtain heat capacity comparable with that of He gas over the whole temperature range when the magnetic materials with different peak heat capacity are arranged in multilayers in the regenerator, the regenerative effectiveness, i.e., the heat exchange effectiveness, was calculated by means of a computer. The results clearly showed that a multilayer regenerator is very effective in composing a regenerator capable of covering the specific heat range of He gas. Previous experimental data also indicate that a multilayer regenerator packed with the most suitable regenerative materials can provide a very high refrigeration capacity.