Abstract: The apparatus for the expansion of fluid in the gaseous or liquid state or in double phase is characterized in that it has an expansion compartment comprising:a first spiral (72),a second spiral (70) located within said first spiral,means (52, 63) to permit a circular translation movement without self-rotation of the second spiral within the first spiral during the expansion of a fluid.

Abstract: Application of a positive displacement pump to the pumping of helium at very low temperatures. Positive displacement pumps, formed from mobile components (35, 36), which deliver gas volumes to pumping chambers, have the advantage of operating under satisfactory conditions for significant temperature, pressure and gas flow rate variations. They are therefore preferred as compared with the hitherto used centrifugal pumps and have means enabling them to operate at very low temperatures.

Abstract: It comprises a first cylinder (102), a displacement piston (104) sliding in the first cylinder (102), a conduit in which a thermal regenerator is included, a second cylinder (202), a second displacement piston (204) sliding in the second cylinder (202), means for displacing the first cylinder and the second cylinder in phase relation. A gas bearing (104a) is provided at the hot end of the first piston (104) and a gas bearing (104b) is provided at the intermediate temperature end of the first piston. A gas bearing (204b) is also provided at the intermediate temperature end of the second piston (204) and a gas bearing (204a) is provided at the cold end of the second piston (204).

Abstract: The device comprises in the tank above the liquid:a pipe for supplying the tank with superfluid helium;a member for removing the superfluid helium by spontaneously producing on its surface a so-called Rollin film, which is essentially located at the horizontal level to which it is desired to regulate the free surface of the helium in the tank and whereof the removing perimeter, which is a variable as a function of the altitude, increases over a height equal to the tolerance in the evolution of the level from its base to a maximum value at its upper junction point with a superleak associated therewith and which is then traversed by the thus removed superfluid helium;a heated chamber into which issues the superleak and which is linked, on the one hand, with an outlet having a controlled flow rate to the atmosphere of the tank and, on the other hand, to a chamber having flexible deformable walls and a variable volume, said walls causing, during their extension or retraction, the displacement of a rod, whose posi

Abstract: The invention relates to a refrigerating or heat pumping process, as well as to an apparatus for performing this process.The apparatus comprises a toroidal cryostat, provided with first and second pipes for supplying fluid at temperature T.sub.1 from a heat source and a pipe for discharging this fluid, a paramagnetic substance support rotating in the cryostat, means for inducing a magnetic field in the cryostat, a fourth pipe for supplying fluid and a fifth pipe for discharging fluid at temperature T.sub.2 relative to a cold source. The magnetic field applied makes it possible, during the rotation of the support, to lower the temperature of the cold source and increase the temperature of the hot source.Application to refrigeration and heat pumping.

Abstract: A bath of helium-4 is cooled to a temperature below the .lambda. point so as to convert the lower portion of the bath to a superfluid-helium zone. A narrow stream between a top and a bottom portion of the zone is subjected to a critical heat flux corresponding to a temperature gradient by cooling the bath in the bottom portion of the superfluid-helium zone, the temperatures thus attainable being considerably lower than the .lambda. transition point.