Active magnetic regenerator

Claim 1

A method of refrigeration approximating a Stirling Cycle from an initial state of partial magnetization and utilizing two, two-phase external heat transfer fluids at temperatures about T C and about T H , the method comprising the steps of (a) magnetizing a body comprising one or more porous magnetic materials near but above their Curie temperatures, each at a temperature between about T C and about T H , flowing an internal heat transfer fluid at an initial temperature substantially T C through the porous material during a relatively higher magnetization of the body, any temperature increase caused by magnetization being compensated by temperature decrease due to thermal wave movement through the material, causing the internal heat transfer fluid to exit the body at a temperature slightly above about T H , which approximates isothermal magnetization; (b) continuing the internal heat transfer fluid flow into the body at about T C and decreasing the magnetic field slightly as average temperature within the body decreases, magnetization remaining essentially constant, approximating an isomagnetization temperature decrease within the body, the internal heat exchange fluid exiting the body at slightly above about T H ; (c) reversing the flow of the internal heat exchange fluid at about T H through the body as demagnetization is compensated by temperature increase due to thermal wave motion in the body, the fluid exiting the body at slightly less than about T C , approximating isothermal demagnetization; and (d) continuing the reverse flow of internal heat exchange fluid through the body and increasing slightly the magnetic field therein to maintain constant magnetization as the average temperature of the body increases, the fluid exiting at slightly less than about T C , approximating an isomagnetization temperature increase; and (e) transferring heat from the internal heat exchange fluid to the two, two-phase external heat exchange fluids appropriately during the cycle to accomplish refrigeration.

Claim 2

A method of refrigeration approximating a Stirling Cycle from an initial state of partial magnetization and utilizing two, two-phase external heat transfer fluids at temperatures about T C and about T H , the method comprising the steps of (a) magnetizing a body comprising one or more porous magnetic materials near but above their Curie temperatures, each at a temperature between about T C and about T H , flowing an internal heat transfer fluid at an initial temperature substantially T C through the porous material during a relatively higher magnetization of the body, any temperature increase caused by magnetization being compensated by temperature decrease due to thermal wave movement through the material, causing the internal heat transfer fluid to exit the body at a temperature slightly above about T H , which approximates isothermal magnetization; (b) continuing the internal heat transfer fluid flow into the body at about T C and decreasing the magnetic field slightly as average temperature within the body decreases, magnetization remaining essentially constant, approximating an isomagnetization temperature decrease within the body, the internal heat exchange fluid exiting the body at slightly above about T H ; (c) reversing the flow of the internal heat exchange fluid at about T H through the body as demagnetization is compensated by temperature increase due to thermal wave motion in the body, the fluid exiting the body at slightly less than about T C , approximating isothermal demagnetization; and (d) continuing the reverse flow of internal heat exchange fluid through the body and increasing slightly the magnetic field therein to maintain constant magnetization as the average temperature of the body increases, the fluid exiting at slightly less than about T C , approximating an isomagnetization temperature increase; and (e) transferring heat from the internal heat exchange fluid to the two, two-phase external heat exchange fluids appropriately during the cycle to accomplish refrigeration.

Claim 4

A method of refrigeration approximating an Ericsson Cycle from an initial state of demagnetization and temperature between about T C and about T H utilizing an internal heat transfer fluid and two, two-phase external heat transfer fluids, the method comprising the steps of: (a) flowing the internal heat transfer fluid through a body comprising one or more porous magnetic materials near their Curie temperatures, each at a temperature between about T C and T H during magnetization of the body to temperature increase caused by magnetization being compensated by temperature decrease caused by thermal wave motion within the body, the fluid exiting at slightly above about T H approximately isothermal magnetization; (b) flowing the internal heat transfer fluid at T C continuously after magnetization to cool material in the body by fluid flow while in a constant magnetic field, the fluid exiting at slightly above about T H , approximating an isofield temperature change; (c) reversing the internal heat transfer fluid flow, the fluid initially passing through the body at T H as demagnetization commences, temperature decrease due to demagnetization being compensated by temperature increase due to thermal wave movement, the fluid exiting at slightly below about T C , approximating an isothermal demagnetization; (d) continuing the fluid flow after demagnetization is complete, the body warming the fluid exiting the body at slightly less than about T C approximating an isofield temperature change; and (e) transferring heat from the internal heat transfer fluid at the end of steps (a), (b), (c), and (d) in the cycle to transfer heat.

Claim 5

A method of refrigeration approximating an Ericsson Cycle from an initial state of demagnetization and temperature between about T C and about T H utilizing an internal heat transfer fluid and two, two-phase external heat transfer fluids, the method comprising the steps of: (a) flowing the internal heat transfer fluid through a body comprising one or more porous magnetic materials near their Curie temperatures, each at a temperature between about T C and T H during magnetization of the body to temperature increase caused by magnetization being compensated by temperature decrease caused by thermal wave motion within the body, the fluid exiting at slightly above about T H approximately isothermal magnetization; (b) flowing the internal heat transfer fluid at T C continuously after magnetization to cool material in the body by fluid flow while in a constant magnetic field, the fluid exiting at slightly above about T H , approximating an isofield temperature change; (c) reversing the internal heat transfer fluid flow, the fluid initially passing through the body at T H as demagnetization commences, temperature decrease due to demagnetization being compensated by temperature increase due to thermal wave movement, the fluid exiting at slightly below about T C , approximating an isothermal demagnetization; (d) continuing the fluid flow after demagnetization is complete, the body warming the fluid exiting the body at slightly less than about T C approximating an isofield temperature change; and (e) transferring heat from the internal heat transfer fluid at the end of steps (a), (b), (c), and (d) in the cycle to transfer heat.

Claim 7

A method of refrigeration approximating a Carnot Cycle from an initial state of partial magnetization utilizing two, two-phase external heat transfer fluids at temperatures of about T C and about T H , the method comprising as steps of: (a) fully magnetizing a body comprising one or more porous magnetic materials near but above their Curie temperatures, each at a temperature between about T C and about T H , flowing an internal heat transfer fluid at a temperature T C into the body, temperature increase due to magnetization being compensated by temperature decrease due to thermal wave movement within the body, the fluid exiting at slightly above about T H which approximates isothermal magnetization; (b) stopping the fluid flow during partial demagnetization at a selected midpoint field, thereby approximating an adiabatic temperature decrease; (c) completing the demagnetization as the fluid flows into the body at substantially T H such that temperature decrease due to demagnetization is compensated by temperature increase due to thermal wave movement within the body, the fluid exiting the body at slightly less than about T C which approximates isothermal demagnetization; (d) stopping fluid flow as magnetic field increases to a low value, approximating an adiabatic temperature increase; (e) repeating the sequences of steps (a) through (d), the fluid exiting at slightly above about T H being cooled by an external two-phase fluid heat exchanger during step (a), the fluid exiting at slightly less than about T C being heated in an external load two-phase heat exchanger during step (c).

Claim 8

A method of refrigeration approximating a Carnot Cycle from an initial state of partial magnetization utilizing two, two-phase external heat transfer fluids at temperatures of about T C and about T H , the method comprising as steps of: (a) fully magnetizing a body comprising one or more porous magnetic materials near but above their Curie temperatures, each at a temperature between about T C and about T H , flowing an internal heat transfer fluid at a temperature T C into the body, temperature increase due to magnetization being compensated by temperature decrease due to thermal wave movement within the body, the fluid exiting at slightly above about T H which approximates isothermal magnetization; (b) stopping the fluid flow during partial demagnetization at a selected midpoint field, thereby approximating an adiabatic temperature decrease; (c) completing the demagnetization as the fluid flows into the body at substantially T H such that temperature decrease due to demagnetization is compensated by temperature increase due to thermal wave movement within the body, the fluid exiting the body at slightly less than about T C which approximates isothermal demagnetization; (d) stopping fluid flow as magnetic field increases to a low value, approximating an adiabatic temperature increase; (e) repeating the sequences of steps (a) through (d), the fluid exiting at slightly above about T H being cooled by an external two-phase fluid heat exchanger during step (a), the fluid exiting at slightly less than about T C being heated in an external load two-phase heat exchanger during step (c).

Claim 26

A method of refrigeration approximating a Brayton Cycle from an initial state of demagnetization utilizing an internal heat exchange fluid and two single phase external heat transfer fluids at temperatures about T C and about T H , respectively, the method comprising the steps of: (a) magnetizing a body comprising one or more porous magnetic materials near but above their Curie temperatures, increasing the average temperature of the body at ΔT, approximating an adiabatic magnetization; (b) flowing the internal fluid at a temperature substantially T C +ΔT through the body so that the fluid flows out of the body at T H +ΔT, approximating an isofield temperature change; (c) demagnetizing the body to accomplish an adiabatic demagnetization so that the average temperature of the body decreases by ΔT; and (d) flowing the internal fluid through the body at about T H so that the fluid flows out of the body at about T C ; and (e) transferring heat from the fluid during steps (b) and (d) to cycle the external heat transfer fluids for refrigeration.

Claim 27

A method of refrigeration approximating a Brayton Cycle from an initial state of demagnetization utilizing an internal heat exchange fluid and two single phase external heat transfer fluids at temperatures about T C and about T H , respectively, the method comprising the steps of: (a) magnetizing a body comprising one or more porous magnetic materials near but above their Curie temperatures, increasing the average temperature of the body at ΔT, approximating an adiabatic magnetization; (b) flowing the internal fluid at a temperature substantially T C +ΔT through the body so that the fluid flows out of the body at T H +ΔT, approximating an isofield temperature change; (c) demagnetizing the body to accomplish an adiabatic demagnetization so that the average temperature of the body decreases by ΔT; and (d) flowing the internal fluid through the body at about T H so that the fluid flows out of the body at about T C ; and (e) transferring heat from the fluid during steps (b) and (d) to cycle the external heat transfer fluids for refrigeration.