liquefaction-31 - Refrigeration Techniques and Liquefaction...

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1 Refrigeration Techniques and Liquefaction of Gases Hydrogen and Helium as an example Read Flynn Ch. 6 T H T L Q H Q L W Fundamentals of refrigeration • Work (W) – transport of energy only • Heat (Q) – transport of energy and entropy • 1st law of thermodynamics • 2nd law of thermodynamics • COP (Coefficient Of Performance) H L Q Q W = + H L H L Q Q T T 1 / 1 L L L H L H L H L Q Q T COP W Q Q T T T T = = - - - Refrigerator System Work Heat Work is transformed to elastic energy, or potential energy, or kinetic energy, or magnetic energy, quantum energy, etc. Internal energy is increased. Heat is transferred to environment with entropy transfer along with it. Principle of refrigeration Removing Heat As T L decreases more work per unit refrigeration ( W/Q L ) is required > 6000 299 1 700 ~ 1500 74 4 100 ~ 200 14 20 10 ~ 20 2 100 0.3 ~ 0.5 0.11 270 Actual Carnot (minimum) Work / Refrigeration W/Q L (W/W) Ref. Temp T L (K) As T L decreases, the Carnot efficiency goes down. Usual method to obtain low temperature b Throttling Process J-T coefficient > 0 for cooling effect JT h T P μ = Joule-Thomson Coefficient Note: The maximum T to begin hydrogen liquefaction is 202 K at 0 atm. Since expansion must
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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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liquefaction-31 - Refrigeration Techniques and Liquefaction...

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