Liquid helium

Belostotskii VF, Bemkin VM (1988) Ordre dans les solutions solides au cours de la deformation par les ultrasons aux temperatures de l helium liquide Ordering in solid solution during ultrasonic deformation at liquid helium temperatures. Metallokfizika 10(6) 99-101... 

Fig. 6. Rhenium image (helium, liquid hydrogen temperature).

Nevertheless, the simplest way to produce low temperature is still the use of cryoliquids (e.g. nitrogen, helium). It must be considered that most low-temperature equipments existing in a laboratory are designed for the use with cryoliquids, and the change to the new technologies is definitely expensive. Also for this reason, we shall briefly describe the properties and the use of cryoliquids used in low-temperature experiments and in particular helium (liquid or gas as used in pulse tubes) which practically intervenes in all refrigeration processes below 10 K. 

Cryogenic Gases, usually liquefied, that induce freezing temperatures of -150 degrees F and below such as liquid oxygen, liquid helium, liquid natural gas, and liquid hydrogen. 

MSE.12. 1. Prigogine et J. Philippot, Theorie moleculaire du point lambda de I helium liquide, (Molecular theory of the lambda point of liquid helium), Physica 18, 729—748 (1952). 

Liquid helium Liquid hydrogen Liquid-inj ection-molded Liquid-mj ec tion moldmg Liquid inks Liquid invert Liquid level measurement... 

The story gets better. C. H. Anderson and E. S. Sabisky, "The absence of a solid layer of helium on alkaline earth fluoride substrates," J. Low Temp. Phys., 3, 235-8 (1970), reported the thickness of helium liquid condensed from vapor onto ceramic substrates. Van der Waals attraction nicely explains film thickness vs. the chemical potential of helium in the vapor. 

Kamerlingh Onnes had only a thimbleful of helium liquid, but it was to be the grand overture to his explorations in a vast new temperature region, a place of intense cold where the physical properties of many substances changed remarkably. Even at the temperature of liquid air, one could perform strange tricks. One can, for example, mold... 

In general, the requirements of this section apply to all large Category A reactors which use a circulating fluid (light water, heavy water, helium, liquid metal, etc.) to cool the reactor core. 

Column diameter, 0.152m dispersion height, 2-3m gas phase, air, O, COy and helium liquid phase, water, aqueous glycol, NaCl, Na SOj,... 

No ordinary electrical conductor is perfect. Even metals have some resistance to the flow of electrons. which wastes energy in the form of heat. Superconductors have no resistance to the flow of electrons and thus could be very useful for the transmission of electricity over the long distances between power plants and cities and towns. The first superconductor was discovered in 1911 by the Dutch physicist H. Kamerlingh-Onnes. He received the 1913 Nobel Prize in Physics for showing that mercury was a superconductor at 4 K. the temperature of liquid helium. Liquid helium is very expensive, however, so there were few feasible applications of a mercury superconductor. 

In physics, the field of cryogenics is loosely defined as the study of physical phenomena that occur at very low temperatures. A cryogenic liquid is therefore defined as a substance which exists as a liquid at extremely cold temperatures and a gas at room temperatures. However, low and cold are relative words since all substances can be evaporatively cooled into a liquid and then solid state, with the exception of helium. Liquid nitrogen (LNa) is generally used as the standard reference cryogenic liquid, since nitrogen exists in abundance on Earth, and because the normal boiling point (NBP) of 77.4 K is very low relative to many substances which exist as liquids at room temperature. 

FIGURE 10.11 Comparison of 325 x 2300 Gaseous Helium/Liquid Methane Subcooled Gain as a Function of Liquid Pressure and Temperature at the Screen between the (a) Data and (b) Model. The black line is the saturation curve. 

Unlike water, sodium, or helium, liquid fluoride salts are a family of coolants with similar general properties. The choice of a specific molten salt for a specific application is determined by functional requirements and costs. Many salts have been examined. Table XXVI-3 shows the properties for several different liquid salts and traditional reactor coolants under typical conditions. Table XXVI-4 lists leading candidates for various nuclear liquid salt applications and their key physical properties. The remainder of this Appendix discusses the various salts and the constraints that limit the choice of salt. 

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