scholarly journals The viscosity of liquid helium

1935 ◽  
Vol 151 (873) ◽  
pp. 342-347 ◽  
Author(s):  
J. O. Wilhelm ◽  
A. D. Misener ◽  
A. R. Clark ◽  
John Cunningham McLennan
Keyword(s):  
Liquid Helium ◽  
Vapour Pressure ◽  
Boiling Point ◽  
Fine Particles ◽  
Apparent Difference ◽  
Reduced Pressure ◽  
Helium Ii ◽  
Λ Point

It is a well-known fact that liquid helium changes from one form of liquid to another at a temperature of 2.19º K, under its own vapour pressure at that temperature. The liquid above this temperature is spoken of as helium I, and below it, as helium II. This temperature is known as the λ point. The apparent difference between these two forms of the liquid is that helium I visibly boils as it is being evaporated in a way similar to ordinary liquids, but immediately this temperature is passed boiling stops and the liquid appears to be absolutely quiescent, although the temperature is progressively reduced by continued evaporation. Many properties of these two forms of liquid helium have been studied, but apparently up to the present the viscosity has not been determined. In order to keep the liquid helium at a given temperature below 4.2º K, its boiling point, it is necessary to allow it to boil under reduced pressure, consequently the formation of bubbles excludes any possibility of using a capillary viscosimeter method. The necessity of operating the liquefying system under reduced pressure also allows small amounts of impurity to leak in; these traces of impurity condense over the liquid helium and drop as fine particles through the liquid. This has to be considered in designing the apparatus.

NON-CLASSICAL FILM FREE CONVECTION IN SUPERFLUID LIQUID HELIUM II NEAR THE λ-POINT

1974 ◽  
Author(s):  
R. C. Amar ◽  
S. C. Soloski ◽  
Traugott H. K. Frederking
Keyword(s):  
Free Convection ◽  
Liquid Helium ◽  
Helium Ii ◽  
Λ Point

XXVII.—A Common Thermometric Error in the Determination of Boiling-Points under Reduced Pressure

1910 ◽  
Vol 30 ◽  
pp. 436-436
Author(s):  
Alexander Smith ◽  
Alan W. C. Menzies
Keyword(s):  
Linear Function ◽  
Vapour Pressure ◽  
Boiling Point ◽  
Thermal Equilibrium ◽  
Reduced Pressure ◽  
Considerable Error ◽  
Boiling Points

When the bulb of a thermometer is enclosed in an evacuated vessel, the dilatation of the bulb introduces a considerable error in the temperature readings. This fact may be well known, but in the literature of boiling-point and vapour-pressure determinations we have observed no reference to it, and no corrections on account of it. Yet, except in the roughest work, this effect cannot be ignored. Thus, a test carried out with eleven thermometers showed that when the pressure round the bulb was lowered from 748 mm. to 20 mm. and thermal equilibrium with the bath had been recovered, the readings were from 0·10° to 0·17° lower. In all but one case, when there was a slight permanent dilatation, the change was constant and was a linear function of the change in pressure. The change bore no relation to the sizes of the bulbs. The thickness of the glass varied considerably, but could not, of course, be measured.

The detection of single quanta of circulation in liquid helium II

1961 ◽  
Vol 260 (1301) ◽  
pp. 218-236 ◽  
Keyword(s):  
Liquid Helium ◽  
Present Form ◽  
Quantized Vortices ◽  
Free Vortex ◽  
Helium Ii ◽  
Vortex Lines ◽  
Fine Wire ◽  
The Wire ◽  
Λ Point ◽  
Made In

An apparatus is described for detecting single quanta of superfluid circulation round a fine wire in liquid helium II. The wire is stretched down the centre of a cylindrical vessel containing helium, and the circulation may be established by rotating the whole apparatus about the axis of the wire and cooling from above the λ-point. The wire can be set into transverse vibration, and the circulation round it can then be obtained from the rate of precession of the plane of vibration. The technique proves to be sufficiently sensitive for the measurement of circulations of order h/m with an accuracy of about 3%. The method in its present form measures only an average of the circulation along the length of the wire, and it is found that this average is not quantized. Apparent circulations equal to a fraction of a quantum are attributed to quantized vortices that are attached to only a fraction of the length of the wire, and this interpretation has been confirmed by showing that an apparent circulation of exactly h/m has much greater stability than any other value. In this way the quantization of superfluid circulation in units of h/m has been experimentally verified. Observations made in the course of this work show clearly that superfluid circulations (including free vortex lines) can persist indefinitely even when the rotation of the apparatus is stopped. Values have also been obtained for the circulation round the wire as a function of the angular velocity of rotation, and it is shown from these that the energy of a free vortex line in the helium surrounding the wire may perhaps be considerably smaller than has hitherto been supposed.

scholarly journals On the Mechano-Caloric Effect in Liquid Helium II

1950 ◽  
Vol 5 (6) ◽  
pp. 1010-1013 ◽  
Author(s):  
S. Nakajima ◽  
M. Shimizu
Keyword(s):  
Liquid Helium ◽  
Helium Ii ◽  
Caloric Effect

scholarly journals The liquefaction of helium by an adiabatic method

1934 ◽  
Vol 147 (860) ◽  
pp. 189-211 ◽  
Keyword(s):  
Liquid Helium ◽  
High Pressures ◽  
Scientific Work ◽  
Liquid Hydrogen ◽  
Thermal Capacity ◽  
Liquid Oxygen ◽  
Reduced Pressure ◽  
External Work ◽  
Adiabatic Principle ◽  
Continuous Output

The liquefaction of helium by Kammerlingh Onnes has led in the past thirty years to discoveries of the greatest importance to the study of the solid state. In spite of this, very few laboratories are now equipped with the apparatus necessary for the production of liquid helium. It is therefore very desirable that the complicated technique necessary for its production should be simplified to allow of its more extensive use. In this paper we shall describe a more efficient liquefier, based on an adiabatic principle, which we hope will considerably simplify the production of liquid helium for scientific work. At present two principal methods are used for the cooling and liquefying of gases. The first method is based on cooling produced by adiabatic expansion where the expanding gas is cooled by doing external work. This phenomenon was observed by Clèment and Desormes in 1819 when they discovered the cooling of a gas in a container when its pressure was reduced by letting out some of the gas through a tap. It can be shown that on expanding, the gas remaining in the container has done work in communicating kinetic energy to the escaped gas, and therefore has been cooled adiabatically. Olszewski in 1895 applied this method to the liquefaction of hydrogen; he compressed the gas to 190 atmospheres and pre-cooled it with liquid oxygen boiling at reduced pressure (-211°C); on releasing the pressure, he observed a fog of liquid hydrogen drops. From this experiment he was able to determine the critical data for hydrogen. This method has also been used recently by Simon for liquefying helium. Simon took advantage of the fact that at very low temperatures the thermal capacity of the container is so small that it practically absorbs no cold from the liquefied helium. The limitations of this method are that it can only conveniently be applied for obtaining small amounts of liquid helium; it is not suited for a continuous output of helium, and also there is necessarily a loss of cold due to the gas which leaves the container. The method is also complicated by the fact that high pressures are required, and that pre-cooling with liquid hydrogen boiling at reduced pressure is necessary.

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