Cooling below 4K-100204

Cooling below 4K-100204 - Cooling Below 4.2 K 1. 2. 3. 4....

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1. 1. Evaporative Cooling 2. 2. Dilution Refrigeration 3. 3. Heat exchangers 4. 4. Pomeranchuk Cooling 5. 5. Adiabatic Demagnetization Refrigeration 6. 6. Acoustic/Pulse Tube Refrigeration 7. 7. Laser Cooling Cooling Below 4.2 K Refrigeration Methods for Very Low Temperatures b Latent heat (also known as enthalpy change of vaporization) Change in energy as system particle goes from liquid state to vapor state p * is the vapor pressure Δ H is the heat of vaporization (kJ/mole) R is the gas constant T is the temperature (Kelvin) B depends on the substance s Responsible for cooling by sweating s Building AC s Power Plant Cooling Evaporative Cooling Sprinklers ln v v H p B RT = - + Energy Distribution of Atoms in Equilibrium at Two Temperatures Phase Diagram of H 2 O Vapor Pressure of Water Temperature (C) -20 0 20 40 60 80 100 120 Vapor Pressure (Torr) 0.1 1 10 100 1000 10000 "Normal boiling point"
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Evaporation Cryostats s Principle of Operation s Technical Realization s Cooling Power Evaporation Cryostat-Principle of Operation Continuous Filling pot 4 He Evaporation Cryostats 4 He Single-Shot Continuous H va p Pumping on Bulk Liquid 3 He 4 He b Capable of reaching temperatures of b about 300mK in 3 He and approx 1K in 4 He b Main disadvantage is that the amount of liquid 4 He is
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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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Cooling below 4K-100204 - Cooling Below 4.2 K 1. 2. 3. 4....

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