Helium refrigerators and liquefiers Outline Air Liquide range

Helium refrigerators and liquefiers

Outline ■ Air Liquide range of cryogenic plants at 4. 5 K and below ■ Few thermodynamical concepts ■ Refrigerators and Liquefiers main equipments 2 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Helium refrigerators and Liquefiers Why ? ■ Why to use helium refrigerators and liquefiers ? ¦ Supraconductivity (magnets, fusion, light sources, …) ¦ Industrial market (gas transportation, …) ¦ Cavities for particles linear accelerators (2 K) ¦ Cold neutron sources (20 K) ¦ Space activities 3 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Air Liquide range of cryogenic plants Standard Liquefiers ■ Standard liquefiers range from 15 L/hr to 650 L/hr ■ Fully automatic operation 4 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Air Liquide range of cryogenic plants Standard Refrigerators ■ Standard refrigerators range from 100 W to 1000 W @ 4. 5 K ■ Fully automatic operation 5 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Air Liquide range of cryogenic plants Specific refrigerators and liquefiers ■ Specific customized liquefiers and refrigerators above 650 L/hr and 1000 W @ 4. 5 K ■ Example: SCL 2 - Korea - 4. 2 k. W @ 2 K - ~4 MW of installed power 20 m 3. 6 m 6 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement 4. 2 k. W @2 K CB

Air Liquide range of cryogenic plants Specific refrigerators and liquefiers ■ Specific customized liquefiers and refrigerators above 650 L/hr and 1000 W @ 4. 5 K ■ Example: ITER - France – 3 x 25 k. W @ 4. 5 K with pulses operation ~24 MW of installed power 110 k. Weq. @ 4. 5 K Loads variation of 65% in 30 min. 40 k. Weq. @ 4. 5 K 7 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Few thermodynamical concepts General principle Power injection which will be transformed into cold Recovery of not used power Insulation against heat inleaks Transfer of power to a colder temperature level Heat load cooling 8 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Helium properties Helium particular properties… ■ Problem: during expansion in a valve, helium warms-up above ~40 K ■ A valve can be used to cool-down helium only below ~40 K. Above ~40 K, energy needs to be extracted with turbines 9 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Few thermodynamical concepts General principle ■ Turbines are used to extract energy ■ Increasing the number of turbines steps increases the efficiency 10 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Few thermodynamical concepts TS Diagram ■ A simple brayton cycle 11 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Global view 12 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Global view 13 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Standard Liquefier process scheme 14 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Helium screw compressors ■ Main Characteristics : ¦ ¦ ¦ ¦ 15 Oil lubricated screw compressor High pressure up to 25 bar Special oil is used to avoid contamination of cryogenic circuits Variable Frequency Drive (VFD) can be used to reduce electric power when capacity reduction is required Volumetric compressors: mass flow m a Pin/Tin Power: Pid = m. R. Tin. Ln(Pout/Pin) Yield ~ 50% 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Helium screw compressors ■ Ideal adiabatic compression of helium to 15 bar would lead to a temperature of 585°C. ■ Oil is used to keep compressor outlet temperature around 80°C. ■ To compress 1 g/s of helium to 15 bar, ~40 g/s of oil is required to limit temperature increase to 80°C 20% of cooling 80% of cooling 16 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Helium screw compressors ■ Helium "standard" Compressors ■ Up to 100 g/s and 300 k. W 17 04/10/2019 Helium refrigerators and liquefiers ■ Specific compressors skids ■ Above 300 k. W and when number of machines decreases reliability and generates too much maintenance Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Oil Removal System (ORS) ■ Oil Removal System (ORS) is used to remove traces of oil in helium ■ Coalescing cartridges remove oil aerosols (liquid droplets of µm size) ■ Charcoal adsorber remove oil vapours ■ ORS efficiency is crucial to avoid cryogenic heat exchangers clogging and turbines damage 18 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Oil Removal System (ORS) ■ Oil Removal System (ORS) is used to remove traces of oil in helium ■ Coalescing cartridges remove oil aerosols (liquid droplets of µm size) ■ Charcoal adsorber remove oil vapours ■ ORS efficiency is crucial to avoid cryogenic heat exchangers clogging and turbines damage 19 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Helium Buffers ■ Gaseous helium storage is necessary to manage helium inventory during cooldown or warm-up. ■ Characteristics: ¦ 3 bar abs <Poperation< 13 bar ¦ At room temperature ¦ Volume: from 5 m 3 (for HELIAL SL) to 400 m 3 (large cryoplants) 20 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Plate fin heat exchangers ■ Brazed aluminium plate fin heat exchangers are used in cold boxes to transfer heat from low pressure circuits to high pressure circuits. ■ High compacity => limit the size of vacuum vessels ■ Design with multi-streams ■ Sensibles to thermal stresses Helium flow Picture from Fives Cryo 21 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Turbines ■ ■ ■ 22 Turbines are used to cool down helium (extract power from the gas) High speed turbines (up to 4 000 Hz) based on static gas bearings Large range of power: from 200 W to 200 k. W Efficiency between 70 and 85% High reliability : MTBF > 100 000 hrs 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Turbines ■ Power extracted proportional to mass flow rate Journal and thrust gas Bearing for shaft guidance High pressure flow Fluid enthalpy extraction by centripetal turbine impeller 23 04/10/2019 Centrifugal compressor driven by turbine mechanical energy transmission through the shaft Kinetic energy production on fixed Inlet Guide Vanes And flow calibration Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Turbines ■ A complete management of the production chain : from design up to test 24 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Adsorbers ■ Adsorbers are used at ~80 K and ~20 K to remove small traces of impurities ■ Molecular sieve or activated charcoal traps air impurities in the ppm range ■ 1 single adsorber : stop of the plant for regeneration or 2 adsorbers operating in push-pull for regeneration on-line 25 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Insulation system ■ A vacuum vessel is used to install cryogenic component ■ Multilayer Insulation (MLI) is used to stop radiations ■ Vacuum pumps are used to stop convection (vacuum < 10 -5 mbar) ■ Material with low conductivity and long thermal path are used to reduce conduction 26 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Cryogenic plants main components Cold Compressors ■ High efficiency cryomachines manufactured by AL-a. T since 80's with new developments in 2009 ■ Technology based on magnetic bearings for high reliability (MTBF > 100 000 hrs) ■ More than 40 cryomachines produced since new developments with flow rates from 10 g/s up to 220 g/s 27 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Helium properties A light gas Gas density (1 bar, 300 K) Boiling temperature (1 bar) Liquid density at saturation (1 bar) Vapor density at saturation (1 bar) 28 Helium Nitrogen 0. 16 kg/m 3 1. 12 kg/m 3 4. 2 K x 780 125 kg/m 3 16. 6 kg/m 3 77. 3 K 809 kg/m 3 x 7. 5 4. 6 kg/m 3 Cp 5. 2 J/(g. K) 1. 0 J/(g. K) Latent heat (1 bar) 20. 7 J/g 199 J/g Sensible heat (liq -> 300 K) 1543 J/g 04/10/2019 Helium refrigerators and liquefiers x 720 x 74 x 178 x 1. 2 234 J/g Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement Risk of Anoxia

Few thermodynamical concepts Refrigerator vs. liquefier ■ Refrigerator ■ Liquefier Cold production Power is necessary at cold temperature 29 04/10/2019 Helium refrigerators and liquefiers Continuous power is necessary between ambiant temperature and cold temperature Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Refrigeration vs. Liquefaction ¢Liquefaction : To liquefy helium, extraction of specific heat from ambient temperature to 4. 4 K is necessary, then extraction from latent heat is GHe necessary to liquefy the gas. 300 K 1573 J/g COLD BOX Energy to extract = 1563 J/g Large turbines are required to produce the cold required in all the temperature range 31 J/g L He 4. 4 K 10 J/g 30 Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Refrigeration vs. Liquefaction ■ Réfrigeration at 4. 5 K: Extraction of latent heat at cold temperature COLD BOX Large heat exchangers are required to transfer energy from vapour returns to helium supply a. Cold vapours returns LHe 4. 4 K a. Re-liquefaction Energy to extract = 21 J/g@4. 4 K 31 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Helium properties Particular properties… 32 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Helium properties Keep in mind ! ■ Liquid Helium: ■ 1 g/s of Helium ~20 W @ 4. 4 K 20 W of heat inleak at 4. 4 K vaporises 30 L/hr of liquid helium ■ 1 g/s of Helium ~30 L/hr ~20 Nm 3/hr ■ Gaseous Helium: ■ 1 g/s of Helium ■ Cp = 5. 2 J/(g. K) 33 04/10/2019 Helium refrigerators and liquefiers 20 W of heat inleak warm up 1 g/s of ~4 K Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Specific power or Carnot efficiency ■ Ideally, 70 W at 300 K are necessary to produce 1 W at 4. 2 K. ■ In practical, between 250 and 400 W are necessary to produce 1 W at 4. 2 K. The larger the installation, the higher the efficiency. 34 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Summary Helium refrigerators and liquefiers ■ Standard helium liquefiers available from 15 L/hr to 650 L/hr ■ Standard helium refrigerators available from 100 W to 1000 W @ 4. 5 K ■ Specific customized plants for helium liquefiers larger than 650 L/hr and refrigerators larger than 1000 W @ 4. 5 K ■ Several references at 1. 8 K or 2. 0 K with state of the art cold compressor technology. 35 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

End of the presentation

Back-up slides

Quizz Questions ■ A liquid helium dewar is full of liquid helium. What would be the pressure in the dewar if all the liquid vaporizes up to ambiant temperature ? ■ A 1000 L liquid helium dewar has 10 W of heat inleaks. What is the autonomy of the dewar ? ■ A thermal shield requires 1 g/s of helium at 35 K. The cryogenic line to thermal shield has 20 W of heat inleaks. What will be the temperature at thermal shield inlet after the cryogenic line ? 38 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Quizz Answers ■ A liquid helium dewar is full of liquid helium. What would be the pressure in the dewar if all the liquid vaporizes up to ambiant temperature ? ■ 125/0. 16 ~780 bar ■ A 1000 L liquid helium dewar has 10 W of heat inleaks. What is the autonomy of the dewar ? ■ 10 W = 0. 5 g/s = 15 L/hr Autonomy = 1000/15 ~ 67 hrs ■ A thermal shield requires 1 g/s of helium at 35 K. The cryogenic line to thermal shield has 20 W of heat inleaks. What will be the temperature at thermal shield inlet after the cryogenic line ? ■ Q = m. Cp. ΔT => ΔT = 20/5. 2 ~ 4 K => Temperature inlet = 39 K 39 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Thermodynamical concepts Latent heat ■ The LATENT HEAT (Lv) is the quantity of heat absorbed or released by a fluid undergoing a change of state, such as ice changing to water or water to steam, at constant temperature and pressure. Also called heat of transformation. ¦ Applied to vaporisation, condensation, melting, solidification etc. . ¦ For pure component, the process is isothermal ¦ Examples: ■ ■ Water : Liq to Gas @ 373 K : 2300 k. J/kg Water : Solid to Liq @ 273 K : 330 k. J/kg LN 2 to GN 2 at 77 K : 200 k. J/kg LHe to Ghe at 4. 2 K : 20. 7 k. J/kg ■ The SPECIFIC HEAT (Cp) is the quantity of heat necessary to warm-up 1 g from 1 K. ¦ Examples: ■ Water : 4. 18 k. J/kg. K-1 ■ Nitrogen : 1 k. J/kg. K-1 ■ Helium : 5. 2 k. J/kg. K-1 40 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Thermal Shields utility: limit the radiation heat loads Stefan-Boltzmann law : Q = k. A x (Tw 4 -Tc 4) Un simple calcul : Tw = 300 K, Tc = 4 K 3004 = 8. 10 x 109 44 = 256 (Tw 4 -Tc 4) = 8. 10 x 109 Tw = 300 K, Tc = 80 K 3004 = 8. 1 x 109 80 4 = 4. 09 x 107 (Tw 4 -Tc 4) = 8. 06 x 109 Remark: Radiation is driven by the warm temperature whatever the cold temperature. Tc = 80 K, Tf = 4 K 804 = 4. 09 x 107 44 = 256 (Tc 4 -Tf 4) = 4. 09 x 107 Thermal shields can thus allow to decrease radiation heat at 4 K by a factor of 200. (4 W sur les Gardner !) 41 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement

Helium properties But not so particular… ■ During an isenthalpic expansion in a valve, does helium cool down or warm-up ? 42 04/10/2019 Helium refrigerators and liquefiers Air Liquide, leader mondial des gaz pour l’industrie, la santé et l’environnement