The peculiarity in heat transfer with supercritical fluids is discussed with special regard to such phenomena as the singularities of the physical properties and the pseudo-boiling near the critical point. The various expressions for the turbulent diffusivities of heat and momentum, and the empirical correlations of the heat transfer coefficient for the supercritical fluids are reviewed. It is stressed that the experimental approach should be urged at present, since the details in heat transfer, e.g. the outbreak of a local degradation and a hot-spot, are hardly predicted by existing theories of transport. A few examples of the possible problems of heat transfer and hydraulics in practical flow channels are also discussed.
Experimental resutls on enhancement of superconductivity in thin films are surveyed especially in connection with the new mechanism of the high critical temperature superconductivity. Most of experiments reviewed were made on composite thin films prepared by low temperature co-deposition of metals with other materials or by alternate deposition of two metals or metals and dielecrics. The enhancement im thin films of soft metals are ascribed mainly to the mechanism of lattice softening due to the large surface to volume ratio and the lattice disorder in thin films by low temperature deposition. There are also other mechanisms proposed; the effect of electronic density of states in transition metals, the effect of spins and the effect of electric field. Superconductivity in intercalated layer compounds are also introduced as the extreme case of thin films. In all the results mentioned, the confirmed evidence of the new mechanism of superconductivity has not been found yet.
Heat transfer to forced supercritical helium has been measured at fluid temperatures of 4.2 to 11K and pressures of 2 to 15 atm (0.2 to 1.5MN/m2). A test section is a 0.109cm i.d. ×8.5cm long stainless-steel tube through which helium flows vertically upwards. Measured results have shown that supercritical helium is similar to ordinary supercritical fluids in turbulent heat transfer. For example, an enhancement of heat transfer coefficient occurs near the transposed critical temperature and the enhancement disappears at high heat flux. The dada have been compared with the correlation proposed by Miropolskii et al. Some phenomena like “pseudo boiling” have been observed.