MAGNETOCALORIC CASCADE AND METHOD FOR FABRICATING A MAGNETOCALORIC CASCADE

• US 20180005735A1
• Filed: 12/07/2015
• Published: 01/04/2018
• Est. Priority Date: 12/18/2014
• Status: Active Grant

• Current Assignee: Astronautics Corporation of America, BASF SE
• Original Assignee: BASF SE
• Inventors: SCHARF, Florian, SCHWIND, Markus, VAN ASTEN, David, JACOBS, Steven Alan
• Granted Patent: US 10,229,775 B2
• Time in Patent Office: Days
• CPC Class Codes: F25B 21/00 Machines, plants or systems, using electric or magnetic effects
• CPC Class Codes: H01F 1/012 adapted for magnetic entropy change by magnetocaloric effect, e.g. used as magnetic refrigerating material refrigeration systems using magnetic effects F25B21/00
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]

Abstract

A magnetocaloric cascade contains a sequence of magnetocaloric material layers having different Curie temperatures T_C, wherein the magnetocaloric material layers include a cold-side outer layer, a hot-side outer layer and at least three inner layers between the cold-side outer layer and the hot-side outer layer, and each pair of next neighboring magnetocaloric layers of the magnetocaloric cascade has a respective Curie-temperature difference amount ΔT_C between their respective Curie temperatures, wherein the hot-side outer layer or the cold-side outer layer or both the hot-side and cold-side outer layer exhibits a larger ratio mΔS_max/ΔT_C in comparison with any of the inner layers, m denoting the mass of the respective magnetocaloric material layer and ΔS_max denoting a maximum amount of isothermal magnetic entropy change achievable in a magnetic phase transition of the respective magnetocaloric material layer.

Claims

1. A magnetocaloric cascade, comprising:

a sequence of magnetocaloric material layers having different Curie temperatures T_C, wherein

the magnetocaloric material layers include a cold-side outer layer, a hot-side outer layer and at least three inner layers between the cold-side outer layer and the hot-side outer layer, and each pair of next neighboring magnetocaloric layers of the magnetocaloric cascade has a respective Curie-temperature difference amount Δ

T_C between their respective Curie temperatures, wherein

the hot-side outer layer or the cold-side outer layer or both the hot-side and cold-side outer layer exhibits a larger ratio mΔ

S_max/Δ

T_C in comparison with any of the inner layers, m denoting the mass of the respective magnetocaloric material layer and Δ

S_max denoting a maximum amount of isothermal magnetic entropy change achievable in a magnetic phase transition of the respective magnetocaloric material layer.

2. The magnetocaloric cascade of claim 1, wherein the hot-side outer layer or the cold-side outer layer exhibits an amount of the ratio mΔ

S_max/Δ

T_C that is at least 1% larger in comparison with any of the inner layers.

3. The magnetocaloric cascade of claim 1, wherein one of the hot-side and cold-side outer layers has a higher amount of the ratio mΔ

S_max/Δ

T_C than the other, and wherein the other of the hot-side and cold-side outer layers has a higher amount of the ratio mΔ

S_max/Δ

T_C than any of inner layers.

4. The magnetocaloric cascade of claim 1, wherein the hot-side outer layer or the cold-side outer layer exhibits an amount of a product mΔ

S_max of its mass and Δ

S_max, the amount of mΔ

S_max being larger by at least 10% in comparison with any of the inner layers.

5. The magnetocaloric cascade of claim 1, wherein the hot-side layer or the cold-side layer exhibits a smaller amount of Δ

T_C in comparison with any of the inner layers.

6. The magnetocaloric cascade of claim 5, wherein the hot-side layer or the cold-side layer exhibits an amount of Δ

T_C that is no less than 0.5 K.

7. The magnetocaloric cascade of claim 1, wherein the hot-side outer layer or the cold-side outer layer or both the hot-side and cold-side outer layer comprises a sublayer sequence of at least two hot-side sublayers or cold-side sublayers, respectively.

8. The magnetocaloric cascade of claim 1, wherein

for each pair of next neighboring magnetocaloric material layers of the magnetocaloric cascade there exists a respective crossing temperature, at which an entropy parameter mΔ

S of both respective neighboring magnetocaloric material layers assumes the same crossing-point value, the entropy parameter mΔ

S being defined as a product of the mass m of the respective magnetocaloric material layer and an amount of its isothermal magnetic entropy change Δ

S in a magnetic phase transition of the respective magnetocaloric material layer; and

wherein

all crossing-point values of an entropy parameter mΔ

S of all pairs of next neighboring inner layers are equal, either exactly or within a margin of ±

15%, to a mean value of all crossing-point values of all pairs of next neighboring inner layers of the magnetocaloric cascade.

9. The magnetocaloric cascade of claim 8, wherein different inner layers exhibit respective materials and respective masses which in combination provide the respective crossing-point values of the entropy parameter mΔ

S at no less than 70% of a global maximum of the entropy parameter mΔ

S assumed in any of the inner layers across the magnetocaloric cascade.

10. A magnetocaloric regenerator, comprising:

the magnetocaloric cascade according to claim 1.

11. A heat pump, comprising:

a magnetocaloric regenerator according to claim 10.

12. The heat pump of claim 11, further comprising:

a hot-side interface in thermal communication with the hot-side outer layer,

a cold-side interface in thermal communication with the cold-side outer layer, and

a heat transfer system, which is configured to provide a flow of a heat-transfer fluid between the hot-side interface and the cold side interface through the magnetocaloric cascade, wherein

the Curie temperature of the hot-side outer layer is selected to be higher than a temperature of the hot-side interface in operation of the heat pump, or the Curie temperature of the cold-side outer layer is selected to be lower than a temperature of the cold-side interface in operation of the heat pump.

14. A heat-pumping method, comprising:

performing a heat-pumping sequence using a magnetocaloric regenerator comprising a magnetocaloric cascade according to claim 1.

15. The heat-pumping method of claim 14, wherein

the heat-pumping sequence includes a temperature increase of the magnetocaloric regenerator and—

the heat-pumping sequence is performed in thermal communication with a heat sink, which is operated at a temperature that is between 0.5 K and 5 K higher than a Curie temperature of the hot-side outer layer.

13. A method for fabricating a magnetocaloric cascade, comprising:

fabricating a sequence of different magnetocaloric material layers having different Curie temperatures T_C, wherein the magnetocaloric material layers include a cold-side outer layer, a hot-side outer layer and at least three inner layers between the cold-side outer layer and the hot-side outer layer and each pair of next neighboring magnetocaloric layers of the magnetocaloric cascade has a respective Curie-temperature difference amount Δ

T_C between their respective Curie temperatures, wherein

the hot-side outer layer or the cold-side outer layer or both the hot-side and cold-side outer layer are fabricated so as to exhibit a larger ratio mΔ

S_max/Δ

T_C in comparison with any of the inner layers, m denoting the mass of the respective magnetocaloric material layer and Δ

S_max denoting a maximum amount of isothermal magnetic entropy change achievable in a magnetic phase transition of the respective magnetocaloric material layer.