Apparatus and methods for performing switching in magnetic refrigeration systems using inductively coupled thermoelectric switches

• US 6,588,215 B1
• Filed: 04/19/2002
• Issued: 07/08/2003
• Est. Priority Date: 04/19/2002
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Ghoshal, Uttam Shyamalindu
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US10/127,063
• Time in Patent Office: 445 Days
• Field of Search: 62/31, 62/37, 623/35
• US Class Current: 62/3.1
• CPC Class Codes: F25B 21/00 Machines, plants or systems, using electric or magnetic effects
• CPC Class Codes: F25B 21/02 using Peltier effect; using Nernst-Ettinghausen effect
• CPC Class Codes: F25B 2321/002 by using magneto-caloric effects
• CPC Class Codes: F25B 2321/0021 with a static fixed magnet
• CPC Class Codes: F25B 2321/0022 with a rotating or otherwise moving magnet
• CPC Class Codes: F25D 19/006 Thermal coupling structure or interface
• CPC Class Codes: H10N 10/00 Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects integrated devices or assemblies of multiple devices H10N19/00
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]

Abstract

Apparatus and methods for performing switching of heat flow in magnetic refrigeration systems are provided. In one embodiment, microelectromechanical (MEM) switches are provided for switching from a heat absorption phase and a heat rejection phase of a magnetic refrigeration cycle. In other embodiments, these MEM switches are replaced by thermoelectric switches. The thermoelectric switches operate such that an “on” state is defined as heat flow being allowed by virtue of the thermal conductivity of the thermoelectric switch. An “off” state is defined as a net zero heat flow through the thermoelectric switch obtained by providing a current that is just sufficient to offset the heat flow through the thermoelectric switch due to its thermal conductivity. In some embodiments, the thermoelectric switches are “directly coupled” thermoelectric switches, meaning that they are energized by a direct electrical coupling to a current source. In other embodiments, one or more of the thermoelectric switches are “inductively coupled” thermoelectric switches, meaning that they are energized indirectly by a magnetic coupling. The magnetic refrigeration system may be cascaded or paralleled to provide greater cooling.

Claims

1. A magnetic cooling system comprising:

a magnetocaloric material; and

at least one thermoelectric switch that is energized indirectly by a magnetic coupling, for switching between a heat rejection and heat absorption phase of a magnetic cooling cycle, wherein when the magnetocaloric material is heated by the presence of a magnetic field, the at least one thermoelectric switch operates to allow heat rejection from the magnetocaloric material to a heat sink, and wherein when the magnetic field is removed from the magnetocaloric material, the at least one thermoelectric switch operates to allow heat absorption from a heat source.

2. The magnetic cooling system of claim 1, wherein the at least one thermoelectric switch is a thermoelectric cooler.

3. The magnetic cooling system of claim 1, wherein the at least one thermoelectric switch comprises:

a first thermoelectric switch positioned between a cold end and the magnetocaloric material; and

a second thermoelectric switch positioned between a hot end and the magnetocaloric material.

4. The magnetic cooling system of claim 3, wherein, during heat rejection, a first current generated by the indirect magnetic coupling enables the first thermoelectric switch.

5. The magnetic cooling system of claim 3, wherein, during heat absorption, the second thermoelectric switch is enabled by a second current.

6. The magnetic cooling system of claim 1, wherein the at least one thermoelectric switch is thermally conductive in the absence of an enabling current.

7. The magnetic cooling system of claim 1, further comprising an electromagnet that generates the magnetic field to cause the magnetocaloric material to generate heat.

8. The magnetic cooling system of claim 7, wherein a current is applied to the at least one thermoelectric switch to change an operation of the thermoelectric switch, and wherein the application of the current to the at least one thermoelectric switch is synchronized with the supplying or removal of a current to the electromagnet.

9. The magnetic cooling system of claim 1, wherein the at least one thermoelectric switch includes one or more redundant thermoelectric switches provided such that the one or more redundant thermoelectric switches assumes the operation of a thermoelectric switch in the event of a failure of the thermoelectric switch.

10. The magnetic cooling system of claim 1, wherein a control system is programmed to provide a particular switching rate for the at least one thermoelectric witches.

11. The magnetic cooling system of claim 1, wherein the magnetic cooling system is part of a cascaded system having a plurality of magnetic cooling systems.

12. The magnetic cooling system of claim 11, wherein the cascaded system is a stacked cascaded system.

13. The magnetic cooling system of claim 11, wherein the system also comprises a parallel cascaded system.

14. The magnetic cooling system of claim 1, further comprising:

at least one permanent magnet; and

a mechanism for moving the permanent magnet into and out of functional proximity to the magnetocaloric material.

15. The magnetic cooling system of claim 14, wherein the mechanism for moving the permanent magnet into and out of functional proximity to the magnetocaloric material is a motor driven rotating mechanism.

16. A method of making a magnetic cooling system comprising:

providing a magnetocaloric material; and

providing at least one thermoelectric switch that is energized indirectly by a magnetic coupling, for switching between a heat rejection and heat absorption phase of a magnetic cooling cycle, wherein when the magnetocaloric material is heated by the presence of a magnetic field, the at least one thermoelectric switch operates to allow heat rejection from the magnetocaloric material to a heat sink, and wherein when the magnetic field is removed from the magnetocaloric material, the at least one thermoelectric switch operates to allow heat absorption from a heat source.

17. The method of claim 16, wherein the at least one thermoelectric switch is a thermoelectric cooler.

18. The method of claim 16, wherein providing the at least one thermoelectric switch comprises:

providing a first thermoelectric switch positioned between a cold end and the magnetocaloric material; and

providing a second thermoelectric switch positioned between a hot end and the magnetocaloric material.

19. The method of claim 18, further comprising generating a first current by indirect magnetic coupling to enable the first thermoelectric switch during heat rejection.

20. The method of claim 18, further comprising enabling the second thermoelectric switch by generating a second current during heat absorption.

21. The method of claim 16, wherein the at least one thermoelectric switch is thermally conductive in the absence of an enabling current.

22. The method of claim 16, further comprising providing an electromagnet that generates the magnetic field to cause the magnetocaloric material to generate heat.

23. The method of claim 22, further comprising applying a current to the at least one thermoelectric switch to change an operation of the thermoelectric switch, and wherein the application of the current to the at least one thermoelectric switch is synchronized with the supplying or removal of a current to the electromagnet.

24. The method of claim 16, wherein providing the at least one thermoelectric switch includes providing one or more redundant thermoelectric switches such that the one or more redundant thermoelectric switches assumes the operation of a thermoelectric switch in the event of a failure of the thermoelectric switch.

25. The method of claim 16, further comprising providing a control system that is programmed to provide a particular switching rate for the at least one thermoelectric switches.

26. The method of claim 16, wherein the magnetic cooling system is provided as part of a cascaded system having a plurality of magnetic cooling systems.

27. The method of claim 26, wherein the cascaded system is a stacked cascaded system.

28. The method of claim 26, wherein the system also comprises a parallel system.

29. The method of claim 16, further comprising:

providing at least one permanent magnet; and

providing a mechanism for moving the permanent magnet into and out of functional proximity to the magnetocaloric material.

30. The magnetic cooling system of claim 29, wherein the mechanism for moving the permanent magnet into and out of functional proximity to the magnetocaloric material is a motor driven rotating mechanism.

31. A method of cooling in a magnetic refrigeration system, comprising:

applying a magnetic field to a magnetocaloric material;

applying a current to a first thermoelectric switch provided between the magnetocaloric material and a cold end of the magnetic refrigeration system;

removing the magnetic field from the magnetocaloric material;

applying a current to a second thermoelectric switch provided between the magnetocaloric material and a hot end of the magnetic refrigeration system; and

stopping the application of the current to the first thermoelectric switch.

32. The method of claim 31, wherein the current is applied to the first thermoelectric switch indirectly by a magnetic coupling.

33. The method of claim 31, wherein the current is applied to the second thermoelectric switch by a direct electrical coupling.

34. The method of claim 31, wherein the current is applied to the second thermoelectric switch indirectly by a magnetic coupling.

35. The method of claim 31, wherein the magnetic field is applied using an electromagnet.

36. The method of claim 31, wherein the magnetic field is applied using at least one permanent magnet and a mechanism for moving the permanent magnet into and out of functional proximity to the magnetocaloric material.

37. The method of claim 36, wherein the mechanism for moving the permanent magnet into and out of functional proximity to the magnetocaloric material is a motor driven rotating mechanism.