Active magnetic regenerator method and apparatus

Active magnetic regenerator apparatus comprising:

• (a) first and second stage regenerator beds, the bed of each stage composed of two parts, each bed part formed of material that exhibits the magnetocaloric effect and is porous to allow the flow of heat transfer fluid therethrough, each bed part having a higher temperature hot side and a lower temperature cold side;
• (b) two superconducting solenoidal magnets having internal bores such that the magnets can surround 14 the bed parts of the first and second stages and selectively apply a magnetic field thereto;
• (c) means for mounting the magnets with respect to the regenerator beds of the first and second stage such that the bed parts and the magnet can be moved relative to one another from a position in which a first magnet is over the first bed part of the first stage to a position in which it is over the second bed part of the first stage, and for moving the second magnet and the second stage beds relative to one another from a position in which the magnet is over a first bed part of the second stage to a position wherein the magnet is over the second bed part of the second stage;
• (d) drive means for selectively driving the magnets and the bed parts relative to one another between a first position in which each magnet is over a first bed part of the first and second stages and a second position in which each magnet is over a second bed part of the first and second stages;
• (e) lines establishing a path for heat transfer fluid from the cold side of the first bed part of the first stage to the hot side of the first bed part of the second stage, from the hot side of the second bed part of the second stage to the cold side of the second bed part of the first stage, from the cold side of the first bed part of the first stage to the cold side of the second bed part of the first stage, and from the cold side of the first bed part of the second stage to the cold side of the second bed part of the second stage;
• (f) a heat exchanger having a path therethrough for heat transfer fluid and a path for fluid to be cooled such that heat can be transferred from the fluid to be cooled to the heat transfer fluid passing through the heat exchanger;
• (g) a pump for heat transfer fluid having an input and an output;
• (h) lines establishing a path for heat transfer fluid from the cold side of the first and second bed parts of the second stage through the heat exchanger to the input of the pump, from the hot sides of the first and second bed parts of the first stage to the input of the pump, and from the output of the pump to the hot sides of the first and second bed parts of the first stage, and switching valves in the lines between the hot sides of the first and second bed parts of the first stage and the input and the output of the pump, the switching valves switchable to a position in which heat transfer fluid is supplied from the hot side of the first bed part of the first stage to the input of the pump and from the output of the pump to the hot side of the second bed part of the first stage, and the valves switchable to a second position in which heat transfer fluid is supplied through the lines from the hot side of the second bed part of the first stage to the input of the pump and the output of the pump is supplied through the lines to the hot side of the first bed part of the first stage, the switching of the valves coordinated with the position of the magnets with respect to the bed parts so that heat transfer fluid is supplied from the first bed part or the second bed part of the first stage to the input of the pump depending on which bed part has a magnet applying a magnetic field to it.

Active magnetic regenerator apparatus comprising:

• (a) a wheel mounted for rotation about an axis and having a rim;
• (b) a plurality of porous regenerator bed units formed of material that exhibits the magnetocaloric effect, each bed unit having a higher temperature hot side and a lower temperature cold side, the bed units mounted in the rim of the wheel to allow axial flow of heat transfer fluid therethrough;
• (c) radial channels formed in the wheel to provide a path for heat transfer fluid from openings near the axis of rotation of the wheel to the hot side of each of the bed units and from the cold side of each of the bed units to openings in the wheel near the axis;
• (d) a magnet mounted to apply a magnetic field to a portion of the regenerator bed units on the rim of the wheel so that the bed units have the magnetic field applied thereto as the wheel rotates to bring the bed units into the magnetic field of the magnet, and such that the magnetic field from the magnet is removed from the bed units as the wheel continues to rotate so that the bed units have a magnetic field applied thereto cyclically as the wheel rotates;
• (e) a manifold having ports with sliding seals in engagement with the wheel to supply heat transfer fluid to an input port and receive fluid from an output port, the seals providing selective communication of heat transfer fluid with the radial channels in the wheel to direct fluid to and from selected regenerator bed units, the manifold cooperating with the channels in the wheel to provide heat transfer fluid from the cold side to the hot side of the bed units which are outside of the magnetic field of the magnet and from the cold side to the hot side of the bed units that are in the magnetic field of the magnet.

Active magnetic regenerator apparatus comprising:

• (a) at least two regenerator stages, each stage having a porous regenerator bed formed of two parts of material which exhibits the magnetocaloric effect, each part of the bed having a higher temperature hot side and a lower temperature cold side, a heat transfer fluid which can pass through the beds between the hot and cold sides to effect heat transfer with the material of the bed, a magnet for each stage producing a magnetic field, means for causing the magnetic field of the magnet for each stage to be applied alternately to one of the bed parts and removed from one of the bed parts;
• (b) lines establishing a path for heat transfer fluid from the cold side of each of the bed parts of a first stage to the hot side of a corresponding one of the bed parts of a second stage, establishing a path for fluid between the cold side of each of the bed parts of the first stage to divert a portion of a first volume of fluid passing from the hot side to the cold side of a bed part of the first stage to the cold side of the other bed part of the first stage to pass therethrough to the hot side thereof, for establishing a path between the cold sides of each of the bed parts of a second stage to allow flow therebetween and for establishing a path from the cold sides of each of the bed parts of the second stage back to the hot sides of the bed parts of the first stage for a portion of the fluid passing from the cold side of a bed part of the second stage.

A method of providing regenerative cooling of a heat transfer fluid comprising the steps of:

• (a) providing a porous regenerator bed of material which exhibits the magnetocaloric effect, the bed having two sides;
• (b) alternately applying a magnetic field to and removing the magnetic field from the regenerator bed;
• (c) passing heat transfer fluid through the bed in one direction with no magnetic field applied to the bed and passing heat transfer fluid through the bed in the other direction with a magnetic field applied to the bed, such that one side of the bed is a higher temperature hot side and the other side of the bed is a lower temperature cold side, the heat transfer fluid being passed through the bed from the hot side to the cold side when no magnetic field is applied to the bed and from the cold side to the hot side when a magnetic field is applied to the bed;
• and
• (d) diverting a portion of the volume of heat transfer fluid passed through the bed from the hot side to the cold side back to the hot side of the bed such that the volume of fluid passed through the bed from the hot side to the cold side is greater than the volume of fluid passed back through the bed from the cold side to the hot side.

A regenerator bed structure for an active magnetic regenerator apparatus, comprising:

• (a) an elongated tubular housing;
• (b) two bed parts mounted in the housing, each bed part formed of plural bed sections having two sides mounted in the housing in stacked relation, each bed part formed of a material which exhibits the magnetocaloric effect and which is porous to the flow of heat transfer fluid therethrough;
• (c) first and second ports formed in the housing for one of the bed parts and first and second ports formed in the housing for the other of the bed parts;
• (d) channels in the housing extending from the first port for each of the bed parts to one side of each section in the bed part, and channels extending from the second port for each of the bed parts to the other side of each section in the bed part, such that heat transfer fluid flowing into the first port for each of the bed parts flows through the channels to one side of each section in the bed part through the sections in parallel and out the other sides of each section and through the channels leading to the second port for each bed part.

Active magnetic regenerator apparatus comprising:

• (a) a first stage comprising a porous regenerator bed of material that exhibits the magnetocaloric effect selected from the group consisting of GdNi.sub.2, GdNi, and a mixture of the two with cobalt substituted for a portion of the nickel, the bed having a higher temperature hot side and a lower temperature cold side, heat transfer fluid which can pass through the bed between the hot and cold sides to effect heat transfer with the material of the bed, a magnet for producing a magnetic field, and means for causing the magnetic field of the magnet to be applied alternately to the bed of the first stage and removed from the bed of the first stage;
• (b) a second stage comprising a porous regenerator bed of material that exhibits the magnetocaloric effect selected from the group consisting of GdPd, GdPd.sub.0.75 Ni.sub.0.25 and Er.sub.0.8 La.sub.0.2, the bed having a higher temperature hot side and a lower temperature cold side, heat transfer fluid which can pass through the bed between the hot and cold sides to effect heat transfer with the material of the bed, a magnet producing a magnetic field, and means for causing the magnetic field of the magnet to be applied alternately to the bed of the second stage and removed from the bed of the second stage;
• (c) transfer means for providing a path for the fluid to and from the regenerator beds of the first and second stages, wherein the transfer means establishes a path for heat transfer fluid from the cold side of the bed of the first stage to the hot side of the bed of the second stage, and for establishing a path from the cold side of the bed of the second stage to the hot side of the bed of the first stage for at least a portion of the fluid passing from the cold side of the bed of the second stage, and for driving a first volume of the fluid through the beds of each stage from the hot side to the cold side of each when the magnetic field is removed from the beds and for driving a second volume of the fluid through the beds of each stage from the cold side to the hot side of each when the magnetic field is applied to the beds.