1. Refrigeration and cryogenics Zakład Kriogeniki i Technologii Gazowych Dr hab. inż. Maciej Chorowski, prof. PWr

2. Methods of lowering the temperature Isentropic expansion Isentropic expansion Joule-Thomson expansion Joule-Thomson expansion Free expansion – gas exhaust Free expansion – gas exhaust

3. Gas isentropic expansion with external work

4. Drop of the gas temperature: Entropy is a function of pressure and temperature S= S(p, T) Total differential must be equal to zero: Differential effect of isentropic expansion  s shows the change in temperature with respect to the change of pressure:

5. Gas isentropic expansion with external work We know from thermodynamics We get where:  is coefficient of cubical expansion

6. Gas isentropic expansion with external work For the ideal gas: After integration

7. Piston expander

8. Cryogenic turboexpander

9. Isenthalpic – Joule-Thomson - expansion When gas, vapour or liquid expands adiabatically in an open system without doing any external work, and there is no increment in velocity on the system reference surface, the process is referred to as throttle expansion. In practice, this process is implemented by installing in the gas stream some hydraulic resistance such as throttling valve, gate, calibrated orifice, capillary, and so on.

10. Isenthalpic – Joule-Thomson - expansion

11. Temperature drop in Isenthalpic – Joule-Thomson - expansion Enthalpy is a function of pressure and temperature: h= h(p, T) Total differential must be equal to zero: Differential throttling effect μ h : Isenthalpic – Joule-Thomson - expansion

13. Gas Maximal inversion temperature, K eksperyment z równania van der Walsa Argon765----- Azot604837 Hel – 3 39----- Hel – 4 4634,3 Neon230----- Powietrze650895 Metan953----- Tlen7711090 Wodór204,6223

14. Free expansion (exhaust)

15. 1. Adiabatic process 2. Non equilibrium process – gas pressure and external pressure are not the same 3. Constant external pressure (p f = const.) 4. External work against pressure p f Free expansion (exhaust)

16. Final gas temperature: I Law of Thermodynamics where: u 0, u f – initial and final gas internal energy v 0, v f – initial and final gas volume Free expansion (exhaust)

17. For ideal gas: We get: Free expansion (exhaust)

18. Comparison of the processes for air

19. Cryogenic gas refrigerators

20. Heat exchangers RecuperativeRegenerative

21. Comparison of coolers

22. Refrigerators with recuperative heat exchangers Joule – Thomson refrigerators Joule – Thomson refrigerators

23. Examples of miniature Joule-Thomson refrigerator

24. Claude refrigerators

25. Stirling coolers

27. Stirling cooler

28. Stirling cycle is realized in four steps : 1. Step 1-2: Isothermal gas compression in warm chamber 2. Step 2-3: Isochoric gas cooling in regenerator 3. Step 3-4:Isothermal gas expansion with external work 4. Step 4-1: Isochoric gas heating in regenerator In Stirling refrigerator a cycle consists of two isotherms and two isobars

29. Stirling split cooler

30. Stirling cooler with linear motor

31. Efficiency of Stirling cooler filled with ideal gas Work of isothermal compression Work of isothermal expansion Heat of isothermal expansion

32. Stirling cooler configuration: Stirling cooler configuration:

33. Stirling cooler used for air liquefact -ion

34. Stirling cooler used for air liquefaction

35. Two stage Stirling refrigerator

36. Gifforda – McMahon cooler Gifforda – McMahon cooler

37. Four steps of McMahon cycle: 1. Filling. 2. Gas displacement 3. Free exhaust of the gas 4. Discharge of cold chamber Efficiency of McMahon cooler: Gifforda – McMahon cooler Gifforda – McMahon cooler

38. McMahon refrigerator

39. Combination of McMahon and J-T cooler, 250 mW at 2,5 K

40. Pulse tube – free exhaust

41. Scheme of pulse tube cooler

42. Development of pulse tube coolers Gifford, 1963, rather curiosity that efficient cooler Kittel, Radebaugh, 1983 orifice pulse tube Dr. Zhu et. al., 1994, multiply by-pass pulse tube

43. Comparison of Stirling and orifice pulse tube cooler

44. Pulse tube cooler for 77 K applications Weight:2.4 kg Dimensions (l x w x h):11.4 x 11.4 x 22 cm Capacity:2.5W @ 65K Ultimate low temperature:35K Input power2kW

45. Pulse tube

46. Two stage pulse tube

47. Pulse tube configuration

48. Adiabatic demagnetization of paramagnetic

49. Paramagnetic salts

50. Magnetic coolers

51. Magnetic cooler

52. Magnetic cooler with moving paramagnetic

53. Three stage magnetic cooler with magnetic regenerator Ceramic magnetic regenerator material Gd2O2S with an average diameter of 0.35 mm for G-M and pulse tube cryocoolers.

54. Cooler efficiency at 80 K

55. „Family” of cryocoolers