The fundamental structure as well as several important success in modern fluid mechanics were described briefly in relation to the future advances in engineering use of cryogenic fluids to be accomplished by sophisticated techniques of the transfer, the distribution and the storage of cryogenic fluids. The problems mentioned include pressure-drop, hydrodynamic instability, critical flow, thermal stratification, sloshing and thermal explosion.
Experimnents were made on pressure drop of liquid nitrogen flow in concentric annuli. The Reynolds number based on hydraulic diameter and mean velocity ranged from 200 to 18, 000. As a result it was found that the relation between Reynolds number and friction factor showed good agreement with the data previously obtained for newtonian fluid at room temperature.
Losses in single- and multi-core superconducting composite conductors were studied experimentally in the range from 20 to 500Hz and below the current of 100A. Composites consist of Nb-60.8 Ti-2.8 Zr ternary superconducting alloy embedded in Cu matrix. Volume of He gas evaporated by the loss when sinusoidal current was passed through the wire was measured. A mechanism of the loss was investigated using a frequency dependence. The single-core composite generates the hysteresis loss in the superconductor and the eddy current loss in Cu matrix. The loss in the multi-core composite is expressed in terms of the hysteresis in an equivalent superconductor which has same volume of superconducting filaments involved and the eddy current loss in an outer region of Cu matrix.
The purification of recovery helium gas is a much annoyed problem for an operator of liquefier. The purity of feed helium gas is one of the most important factors for a long-term stable running of liquefier. Accordingly much care is necessary for a purification process. We previously made adsorption measurements and reported “The Problem of Separating Air from Recovery Helium Gas”. But the recovery helium gas generally contains Ar, CO2, H2, and Ne besides air as undesirable impurities. It seems we don't pay attention to the problem of separating such impurities, especially H2, in a commercially available purifier. We shouldn't forget the air contains 100ppm volume of H2, moreover the difficulty of separatingout H2 in a purification process owing to the very low boiling and freezing point. Actually we were confronted with a trouble of blocking JT-heat exchanger by traces of H2. The traces of H2 in feed helium gas concentrated on JT-cycle in a long-term running. Therefore we have made H2-He gas adsorption measurements on charcoal, Molecular Sieves 13X, 5A, 4A and natural zeolite in the pressure range of 5-120atm and at liquid nitrogen temperature. The results show that the cocoanut shell charcoal adsorbs 100ml of H2 per gram, the possibility of separating out 0.5 volume % of H2 in recovery helium gas in a usual purifier with a help of small Deoxo unit.