properties of cryogens

properties of cryogens - Characteristics of a cryogenic...

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1 Characteristics of a cryogenic fluid 1. Critical, normal boiling, and triple point temperatures of cryogenic fluids 2. Vapor pressure of liquids 3. Liquid Helium 4. Superfluids Critical, normal boiling, and triple point temperatures of cryogenic fluids Note log temperature scale Figure adapted from Cryogenic Engineering by Thomas M. Flynn, Dekker:NY (1997), p. 80 Vapor pressure of liquids Figure adapted from Cryogenic Engineering by Thomas M. Flynn, Dekker:NY (1997), p. 81 Helium • Spherical shape • Two isotropic forms: 3 He and 4 He • Low mass • Van der Waals forces b low critical and boiling points • Remains a liquid even at absolute zero (unless external pressure is applied) How do you spell the word for making a gas into a liquid? A. liquify B. liquefy C. liquafy D. liquifi E. liquiphy Spelling Bee In whose laboratory was helium first liquefied? A. Sir James Dewar B. Cailletet C. Wroblewski D. Onnes E. Van der Waals Name that man
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1882-Helium liquefied at Leiden University H. Kamerlingh Onnes was one of the first professors in experimental physics at Leiden University. His lab first to liquefy helium (1908), for which he was awarded the Nobel prize in 1913, and he discovered superconductivity in 1911. He liquefied hydrogen to pre-cool the helium gas in his liquefier. • In 1882, Onnes was appointed Professor of Experimental Physics at Leiden University. In 1895, he established Leiden Laboratory • His researches were mainly based on the theories of J.D. van der Waals and H.A. Lorentz • Was able to bring the temperature of helium down to 0.9 °K, justifying the saying that the coldest spot on earth was situated at Leiden. Heike Kamerlingh Onnes (left) and Van der Waals in Leiden at the helium 'liquefactor' (1908) Who would have ever thought… Heike Kamerlingh Onnes , his stamp, and ( right ) showing his helium liquefier to passers-by: Niels Bohr (visiting from Kopenhagen), Hendrik Lorentz, and Paul Ehrenfest ( far left ). Why Not A Solid? • Zero-Point Energy • E decreases as V increases b the effect of the Zero-Point to raise molar volume • Kinetic energy exceeds the interaction potential energy 3 2 8 3 2 mV h E = energy of a free particle in a small box Heike Kamerlingh Onnes discovered superconductivity, the total lack of dc electrical resistance in certain materials when cooled to a
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This note was uploaded on 10/22/2011 for the course PHY 4550 taught by Professor Ihas during the Spring '08 term at University of Florida.

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properties of cryogens - Characteristics of a cryogenic...

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