properties - 1 Characteristics of a cryogenic fluid 1....

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Unformatted text preview: 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 1 atm Normal Boiling Temp 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 low critical and boiling points Remains a liquid even at absolute zero (unless external pressure is applied) In whose laboratory was helium first liquefied? A. Sir James Dewar B. Cailletet C. Wroblewski D. Onnes E. Van der Waals Name that man 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. 2 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 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 some casual passers-by: Niels Bohr (visiting from Kopenhagen), Hendrik Lorentz, and Paul Ehrenfest ( far left ). Why Not A Solid? Zero-Point Energy E = (3h^2)/(8mV^(2/3)) energy of a free particle in a small box E decreases as V increases the effect of the Zero-Point is to raise molar volume Kinetic energy exceeds the interaction potential energy Heike Kamerlingh Onnes discovered superconductivity, the total lack of electrical resistance in certain materials when cooled to a temperature near absolute zero. Superconductivity-1911 Phase Diagrams 4 He 3 He Regular substance 3 Superfluidity occurs in 4 He at about 4.2 K but only below about 0.002 K in 3 He. Why? A. 3 He is rarer than 4 He in nature B. 3 He is always in smaller containers than is 4 He C....
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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 - 1 Characteristics of a cryogenic fluid 1....

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