Heat pump with magneto caloric materials and variable magnetic field strength

A heat pump system is provided that uses MCM for heating or cooling. A magnetic field of decreasing flux intensity is used to decrease power consumption and reduce e.g., the size of one or more magnetic devices associated with creating the magnetic field. In one exemplary embodiment, the heat pump is constructed from a continuously rotating regenerator where MCM is cycled in and out of a magnetic field in a continuous manner and a heat transfer fluid is circulated therethrough to provide for heat transfer in a cyclic manner. The magneto caloric material may include stages having different Curie temperature ranges. An appliance using such a heat pump system is also provided. The heat pump may also be used in other applications for heating, cooling, or both.

FIELD OF THE INVENTION

The subject matter of the present disclosure relates generally to a heat pump that uses magneto caloric materials in a magnetic field of variable strength to provide for heat transfer.

BACKGROUND OF THE INVENTION

Conventional refrigeration technology typically utilizes a heat pump that relies on compression and expansion of a fluid refrigerant to receive and reject heat in a cyclic manner so as to effect a desired temperature change or i.e. transfer heat energy from one location to another. This cycle can be used to provide e.g., for the receiving of heat from a refrigeration compartment and the rejecting of such heat to the environment or a location that is external to the compartment. Other applications include air conditioning of residential or commercial structures. A variety of different fluid refrigerants have been developed that can be used with a heat pump in such systems.

Certain challenges exist with these conventional heat pump systems. While improvements have been made, at best heat pump systems that rely on the compression of fluid refrigerant can still only operate at about 45 percent or less of the maximum theoretical Carnot cycle efficiency. Also, some fluid refrigerants have been discontinued due to environmental concerns. The range of ambient temperatures over which certain such refrigerant-based systems can operate may be impractical for certain locations. Other challenges with heat pumps that use a fluid refrigerant exist as well.

Magneto caloric materials (MCMs)—i.e. materials that exhibit the magneto caloric effect—provide a potential alternative to fluid refrigerants for heat pump applications. In general, the magnetic moments of a normal MCM will become more ordered under an increasing, externally applied magnetic field and cause the MCM to generate heat. Conversely, decreasing the externally applied magnetic field will allow the magnetic moments of the MCM to become more disordered and allow the MCM to absorb heat. Some MCMs exhibit the opposite behavior—i.e. generating heat when a magnetic field is removed and becoming cooler when placed into the magnetic field. This latter type can be referred to as inverse or para-magneto caloric material. Both normal and inverse MCM are referred to collectively herein as magneto caloric material or MCM. The theoretical Carnot cycle efficiency of a refrigeration cycle based on an MCM can be significantly higher than for a comparable refrigeration cycle based on a fluid refrigerant. As such, a heat pump system that can effectively use an MCM would be useful.

Challenges exist to the practical and cost competitive use of an MCM, however. In addition to the development of suitable MCMs, equipment that can attractively utilize an MCM is still needed. In certain constructions, one or magnets are used to create the magnetic field that causes the MCM to exhibit the magneto caloric effect. Although necessary, such magnets contribute substantially to the overall costs of a heat pump that uses an MCM.

Additionally, as stated above, the ambient conditions under which a heat pump may be needed can vary substantially. For example, for a refrigerator appliance placed in a garage or located in a non-air conditioned space, ambient temperatures can range from below freezing to over 90° F. Some MCMs are capable of accepting and generating heat only within a much narrower temperature range than presented by such ambient conditions. Also, different MCMs may exhibit the magneto caloric effect more prominently at different temperatures.

As further described below, one approach for providing the cooling needed in e.g., refrigerator applications can be to use multiple different MCMs having different response temperatures in a manner that provides the overall temperature change needed. However, as the contents of e.g., the refrigerator are lowered in temperature, subjecting all of the MCM to the same magnetic field strength can be unnecessary and inefficient.

Accordingly, a heat pump system that can address certain challenges such as those identified above would be useful. Such a heat pump system that can also be used in e.g., a refrigerator appliance would also be useful.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a heat pump system that uses MCM to provide for heating or cooling. A magnetic field of decreasing flux intensity is used to decrease power consumption and reduce the size of one or more magnetic devices (such as e.g., magnets) that are associated with creating the magnetic field. In one exemplary embodiment, the heat pump is constructed from a continuously rotating regenerator where MCM is cycled in and out of a magnetic field in a continuous manner and a heat transfer fluid is circulated therethrough to provide for heat transfer in a cyclic manner. The MCM may include stages having different Curie temperature ranges. An appliance using such a heat pump system is also provided. The heat pump may also be used in other applications for heating, cooling, or both. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In one exemplary embodiment, the present invention provides a heat pump. The heat pump includes a plurality of stages arranged sequentially along a predetermined direction. Each stage includes magneto caloric material having a Curie temperature range. The plurality of stages is arranged so that the Curie temperature ranges of the plurality of stages increase along the predetermined direction. A magnetic device is positioned adjacent to the plurality of stages. The magnetic device is configured to subject the plurality of stages to a magnetic field of decreasing magnetic flux along the predetermined direction.

In another exemplary embodiment, the present invention provides a heat pump system that includes a regenerator housing defining a circumferential direction and rotatable about an axial direction. The axial direction extends between a first end and a second end of the regenerator housing. The regenerator housing includes a plurality of chambers with each chamber extending longitudinally along the axial direction between a pair of openings. The plurality of chambers is arranged proximate to each other along the circumferential direction.

A plurality of working units are provided with each working unit positioned within one of the plurality of chambers and extending along the axial direction. Each working unit includes a plurality of stages arranged sequentially along the axial direction. Each stage includes magneto caloric material having a Curie temperature range. The plurality of stages is arranged so that the Curie temperature ranges of the plurality of stages increase along the axial direction.

A pair of valves is provided. This pair includes a first valve attached to the first end of the regenerator housing and a second valve attached to the second end of the regenerator housing. The first valve and the second valve each include a plurality of apertures spaced apart from each other along the circumferential direction with each aperture positioned adjacent to one of the pair of openings of one of the plurality of chambers. A magnetic device is positioned proximate to the regenerator housing and extends along the axial direction. The magnetic device creates a magnetic field of decreasing magnetic flux along the axial direction as the Curie temperature ranges increase. The magnetic device is positioned so that one or more of the plurality of working units are moved in and out of the magnetic field as the regenerator housing is rotated about the axial direction.

A pair of seals is provided and includes a first seal positioned adjacent to the first valve and a second seal adjacent to the second valve such that the regenerator housing and the pair of valves are rotatable relative to the pair of seals. The first seal and the second seal each includes a pair of ports positioned in an opposing manner relative to each other and also positioned so that each port can selectively align with at least one of the pair of openings of the plurality of chambers as the regenerator housing is rotated about the axial direction.

In other embodiments, the present invention includes an appliance such as e.g., a refrigerator having the heat pump or heat pump system as set forth above.

DETAILED DESCRIPTION OF THE INVENTION

Referring now toFIG. 1, an exemplary embodiment of an appliance refrigerator10is depicted as an upright refrigerator having a cabinet or casing12that defines a number of internal storage compartments or chilled chambers. In particular, refrigerator appliance10includes upper fresh-food compartments14having doors16and lower freezer compartment18having upper drawer20and lower drawer22. The drawers20,22are “pull-out” type drawers in that they can be manually moved into and out of the freezer compartment18on suitable slide mechanisms.

Refrigerator10is provided by way of example only. Other configurations for a refrigerator appliance may be used as well including appliances with only freezer compartments, only chilled compartments, or other combinations thereof different from that shown inFIG. 1. In addition, the heat pump and heat pump system of the present invention is not limited to appliances and may be used in other applications as well such as e.g., air-conditioning, electronics cooling devices, and others. Thus, it should be understood that while the use of a heat pump to provide cooling within a refrigerator is provided by way of example herein, the present invention may also be used in other applications to provide for heating and/or cooling as well.

FIG. 2is a schematic view of another exemplary embodiment of a refrigerator appliance10including a refrigeration compartment30and a machinery compartment40. In particular, machinery compartment30includes an exemplary heat pump system52of the present invention having a first heat exchanger32positioned in the refrigeration compartment30for the removal of heat therefrom. A heat transfer fluid such as e.g., an aqueous solution, flowing within first heat exchanger32receives heat from the refrigeration compartment30thereby cooling its contents. A fan38may be used to provide for a flow of air across first heat exchanger32to improve the rate of heat transfer from the refrigeration compartment30.

The heat transfer fluid flows out of first heat exchanger32by line44to heat pump100. As will be further described herein, the heat transfer fluid receives additional heat associated with the magneto caloric effect provided by MCM in heat pump100and carries this heat by line48to pump42and then to second heat exchanger34. Heat is released to the environment, machinery compartment40, and/or other location external to refrigeration compartment30using second heat exchanger34. A fan36may be used to create a flow of air across second heat exchanger34and thereby improve the rate of heat transfer to the environment. Pump42connected into line48causes the heat transfer fluid to recirculate in heat pump system52. Motor28is in mechanical communication with heat pump100as will be further described.

From second heat exchanger34the heat transfer fluid returns by line50to heat pump100where, as will be further described below, due to the magneto caloric effect, the heat transfer fluid loses heat to the MCM in heat pump100. The now colder heat transfer fluid flows by line46to first heat exchanger32to receive heat from refrigeration compartment30and repeat the cycle as just described.

Heat pump system52is provided by way of example only. Other configurations of heat pump system52may be used as well. For example, lines44,46,48, and50provide fluid communication between the various components of the heat pump system52but other heat transfer fluid recirculation loops with different lines and connections may also be employed. For example, pump42can also be positioned at other locations or on other lines in system52. Still other configurations of heat pump system52may be used as well.

FIGS. 3, 4, 5, and 6depict various views of an exemplary heat pump100of the present invention. Heat pump100includes a regenerator housing102that extends longitudinally along an axial direction between a first end118and a second end120. The axial direction is defined by axis A-A about which regenerator housing102rotates. A radial direction R is defined by a radius extending orthogonally from the axis of rotation A-A (FIG. 5). A circumferential direction is indicated by arrows C.

Regenerator housing102defines a plurality of chambers104that extend longitudinally along the axial direction defined by axis A-A. Chambers104are positioned proximate or adjacent to each other along circumferential direction C. Each chamber104includes a pair of openings106and108positioned at opposing ends118and120of regenerator housing102.

Heat pump100also includes a plurality of working units112that each include MCM. Each working unit112is located in one of the chambers104and extends along axial direction A-A. For the exemplary embodiment shown in the figures, heat pump100includes eight working units112positioned adjacent to each other along the circumferential direction as shown and extending longitudinally along the axial direction A-A. As will be understood by one of skill in the art using the teachings disclosed herein, a different number of working units112other than eight may be used as well.

A pair of valves114and116are attached to regenerator housing102and rotate therewith along circumferential direction C. More particularly, a first valve114is attached to first end118and a second valve116is attached to second end120. Each valve114and116includes a plurality of apertures122and124, respectively. For this exemplary embodiment, apertures122and124are configured as circumferentially-extending slots that are spaced apart along circumferential direction C.

Each aperture122is positioned adjacent to a respective opening106of a chamber104. Each aperture124is positioned adjacent to a respective opening108of a chamber104. Accordingly, a heat transfer fluid may flow into a chamber104through a respective aperture122and opening106so as to flow through the MCM in a respective working unit112and then exit through opening108and aperture124. A reverse path can be used for flow of the heat transfer fluid in the opposite direction through the working unit112of a given chamber104.

Regenerator housing102defines a cavity128that is positioned radially inward of the plurality of chambers104and extends along the axial direction between first end118and second end120. A magnetic device126is positioned within cavity128and, for this exemplary embodiment, extends along the axial direction between first end118and second end120. Magnetic device126provides a magnetic field M that is directed radially outward as indicated by arrows M inFIG. 5.

The positioning and configuration of magnetic device126is such that only a subset (e.g., one, two, or more) of the plurality of working units112is/are within or subjected to magnetic field M at any one time. For example, as shown inFIG. 5, working units112aand112eare partially within the magnetic field while units112b,112c,and112dare fully within the magnetic field M created by magnetic device126. Conversely, the magnetic device126is configured and positioned so that working units112f,112g,and112hare completely or substantially out of the magnetic field created by magnetic device126. However, as regenerator housing102is continuously rotated along circumferential direction C as shown by arrow W, the subset of working units112within the magnetic field will continuously change as some working units112will enter magnetic field M and others will exit.

A pair of seals136and138is provided with such seals positioned in an opposing manner at the first end118and second end120of regenerator housing102. First seal136has a first inlet port140and a first outlet port142and is positioned adjacent to first valve114. As shown, ports140and142are positioned 180 degrees apart about the circumferential direction C of first seal114. However, other configurations may be used. For example, ports140and142may be positioned within a range of about 170 degrees to about 190 degrees about the circumferential direction C as well. First valve114and regenerator housing102are rotatable relative to first seal136. Ports140and142are connected with lines44and46(FIG. 1), respectively. As such, the rotation of regenerator housing102about axis A-A sequentially places lines44and46in fluid communication with at least two working units112of MCM at any one time as will be further described.

Second seal138has a second inlet port144and a second outlet port146and is positioned adjacent to second valve116. As shown, ports144and146are positioned 180 degrees apart about the circumferential direction C of second seal116. However, other configurations may be used. For example, ports144and146may be positioned within a range of about 170 degrees to about 190 degrees about the circumferential direction C as well. Second valve116and regenerator housing102are rotatable relative to second seal138. Ports144and146are connected with lines50and48(FIG. 1), respectively. As such, the rotation of regenerator housing102about axis A-A sequentially places lines48and50in fluid communication with at least two working units112of MCM at any one time as will be further described. Notably, at any one time during rotation of regenerator housing102, lines46and50will each be in fluid communication with at least one working unit112while lines44and48will also be in fluid communication with at least one other working unit112located about 180 degrees away along the circumferential direction.

FIG. 7illustrates an exemplary method of the present invention using a schematic representation of a working unit112of MCM in regenerator housing102as it rotates in the direction of arrow W between positions 1 through 8 as shown inFIG. 6. During step200, working unit112is fully within magnetic field M, which causes the magnetic moments of the material to orient and the MCM to heat (when a normal MCM is used) as part of the magneto caloric effect. Ordering of the magnetic field is created and maintained as working unit112is rotated sequentially through positions 2, 3, and then 4 (FIG. 6) as regenerator housing102is rotated in the direction of arrow W. During the time at positions 2, 3, and 4, the heat transfer fluid dwells in the MCM of working unit112and, therefore, is heated. More specifically, the heat transfer fluid does not flow through working unit112because the openings106,108,122, and124corresponding to working unit112in positions 2, 3, and 4 are not aligned with any of the ports140,142,144, or146.

In step202, as regenerator housing102continues to rotate in the direction of arrow W, working unit112will eventually reach position 5. As shown inFIGS. 3 and 6, at position 5 the heat transfer fluid can flow through the MCM as first inlet port140is now aligned with an opening122in first valve114and an opening106at the first end118of working unit112while second outlet port146is aligned with an opening124in second valve116at the second end120of working unit112.

As indicated by arrow QH-OUTinFIGS. 3 and 7, heat transfer fluid in working unit112, now heated by the MCM, can travel out of regenerator housing102and along line48to the second heat exchanger34. At the same time, and as indicated by arrow QH-IN, heat transfer fluid from first heat exchanger32flows into working unit112from line44when working unit112is at position 5. Because heat transfer fluid from the first heat exchanger32is relatively cooler than the MCM in working unit112, the MCM will lose heat to the heat transfer fluid.

Referring again toFIG. 7and step204, as regenerator housing102continues to rotate in the direction of arrow W, working unit112is moved sequentially through positions 6, 7, and 8 where working unit112is completely or substantially out of magnetic field M. The absence or lessening of the magnetic field is such that the magnetic moments of the MCM become disordered and the MCM absorbs heat as part of the magneto caloric effect for a normal MCM. During the time in positions 6, 7, and 8, the heat transfer fluid dwells in the MCM of working unit112and, therefore, is cooled by losing heat to the MCM as the magnetic moments disorder. More specifically, the heat transfer fluid does not flow through working unit112because the openings106,108,122, and124corresponding to working unit112when in positions 6, 7, and 8 are not aligned with any of the ports140,142,144, or146.

Referring to step206ofFIG. 7, as regenerator housing102continues to rotate in the direction of arrow W, working unit112will eventually reach position 1. As shown inFIGS. 3 and 6, at position 1 the heat transfer fluid in working unit112can flow through the MCM as second inlet port144is now aligned with an opening124in second valve116and an opening108at the second end120while first outlet port142is aligned with an opening122in first valve114and opening106at first end118. As indicated by arrow QC-OUTinFIGS. 3 and 7, heat transfer fluid in working unit112, now cooled by the MCM, can travel out of regenerator housing102and along line46to the first heat exchanger32. At the same time, and as indicated by arrow QC-IN, heat transfer fluid from second heat exchanger34flows into working unit112from line50when working unit112is at position 5. Because heat transfer fluid from the second heat exchanger34is relatively warmer than the MCM in working unit112at position 5, the MCM will lose some of its heat to the heat transfer fluid. The heat transfer fluid now travels along line46to the first heat exchanger32to receive heat and cool the refrigeration compartment30.

As regenerator housing102is rotated continuously, the above described process of placing each working unit112in and out of magnetic field M is repeated. Additionally, the size of magnetic field M and regenerator housing102are such that a subset of the plurality of working units112is within the magnetic field at any given time during rotation. Similarly, a subset of the plurality of working units112are outside (or substantially outside) of the magnetic field at any given time during rotation. At any given time, there are at least two working units112through which the heat transfer fluid is flowing while the other working units112remain in a dwell mode. More specifically, while one working unit112is losing heat through the flow of heat transfer fluid at position 5, another working unit112is receiving heat from the flowing heat transfer fluid at position 1, while all remaining working units112are in dwell mode. As such, the system can be operated continuously to provide a continuous recirculation of heat transfer fluid in heat pump system52as working units112are each sequentially rotated through positions 1 through 8.

As will be understood by one of skill in the art using the teachings disclosed herein, the number of working units for housing102, the number of ports in valve114and116, and/or other parameters can be varied to provide different configurations of heat pump100while still providing for continuous operation. For example, each valve could be provided within two inlet ports and two outlet ports so that heat transfer fluid flows through at least four working units112at any particular point in time. Alternatively, regenerator housing102, valves122and124, and/or seals136and138could be constructed so that e.g., at least two working units are in fluid communication with an inlet port and outlet port at any one time. Other configurations may be used as well.

As stated, working unit112includes MCM extending along the axial direction of flow. The MCM may be constructed from a single MCM or may include multiple different MCMs having e.g., different temperature ranges over which each MCM exhibits the magneto caloric effect. By way of example, appliance10may be used in an application where the ambient temperature changes over a substantial range. However, a specific MCM may exhibit the magneto caloric effect over only a much narrower temperature range. As such, it may be desirable to use a variety of MCMs within a given working unit to accommodate the wide range of ambient temperatures over which appliance10and/or heat pump100may be used.

Accordingly, as shown inFIG. 7, each working unit112can be provided with stages152,154,156,158,160, and162of different MCMs that are arranged sequentially along a predetermined direction—e.g., along axial direction A-A in this exemplary embodiment. Each such stage includes an MCM that exhibits the magneto caloric effect at a different temperature or a different temperature range than an adjacent stage along the axial direction A-A. The range of temperature over which the MCM (normal or inverse) in each stage exhibits the desired magneto caloric response to provide heating or cooling is referred to herein as the “Curie temperature range.”

The stages can be arranged so that e.g., the Curie temperature ranges of the plurality of stages increases along a predetermined direction such as axial direction A-A. For example, stage152may exhibit the magnet caloric effect at a temperature less than the temperature at which stage154exhibits the magnet caloric effect, which may be less than such temperature for stage156, and so on. Other configurations may be used as well. By configuring the appropriate number and sequence of stages of MCM, heat pump100can be operated over a substantial range of ambient temperatures.

In one exemplary embodiment, the Curie temperature ranges of stages152,154,156,158,160, and162are also selected to overlap in order to facilitate heat transfer along direction HT. For example, in the embodiment shown inFIG. 7, stage162could have a Curie temperature range of 20° C. to 10° C.; stage160could have a Curie temperature range of 17.5° C. to 7.5° C.; stage158could have a Curie temperature range of 15° C. to 5° C.; stage156could have a Curie temperature range of 12.5° C. to 2.5° C.; stage154could have a Curie temperature range of 10° C. to 0° C.; and stage152could have a Curie temperature ranges of 5° C. to −2. These ranges are provided as examples; other Curie temperature ranges may be used as well in still other exemplary embodiments of the invention.

At stated, different types or e.g., alloys of MCMs can have different Curie temperature ranges over which the MCM will substantially exhibit a magneto caloric effect. In addition, the magnitude of the magneto caloric effect can also be different for different MCMs. For example,FIG. 8provides a plot of the amount of temperature change per a unit of material of different MCMs (ΔT/MCM) as a function of operating temperature T. As shown, for these particular MCMs, the amount of temperature change each stage of MCM can provide decreases as the temperature decreases. Also, the amount of the magneto caloric effect that can be obtained from a given stage is also dependent upon the strength—i.e., the amount of magnetic flux—of the magnetic field that is applied to the MCM. With a given MCM, for example, the magnitude of the magneto caloric effect will be less as the magnitude of the magnetic flux decreases.

During operation of a heat pump100having stages152,154,156,158,160, and162as shown inFIG. 8, the stages having a higher Curie temperature range become less important as e.g., cooling takes place and the compartments of the refrigerator approach 0° C. As the temperature is lowered, the stages having lower Curie temperature ranges (e.g., stages152and154) provide the cooling required to maintain the desired temperature. However, because the stages having a higher Curie temperature range (e.g.,160and162) are still being subjected to the field of changing magnetic flux provided by magnetic device126as previously described, heat pump100is still consuming the power needed to cycle these stages.

Accordingly, as shown inFIG. 7, magnetic device126is positioned adjacent to the plurality of stages152,154,156,158,160, and162and is configured to subject those stages to a magnetic field M of decreasing flux along a predetermined direction, which for this example is along axial direction A-A. As shown by arrows M inFIG. 7, the magnetic flux decreases as the Curie temperature range associated with each stage152through162increases. For this exemplary embodiment, magnetic device126can be constructed from one or more magnets. Magnet(s)126have a thickness T along a direction O that is orthogonal to the predetermined direction—i.e. axial direction A-A. Moving along axial direction A-A, the thickness T of magnet(s)126decreases so that the corresponding magnetic flux is also decreased along axial direction A.

Other constructions can also be used to provide for a decrease in magnetic flux. For example, magnetic device126may be configured as an electromagnet or a combination of an electromagnet and one or more magnets—each of which can be configured to decrease the magnetic flux along a predetermined direction.

A variety of configurations can be used to determine the amount or, more particularly, the rate of decrease in the magnetic flux provided by magnetic device126along the predetermined direction. For example, in one exemplary embodiment as shown inFIG. 7, the decrease is substantially linear along axial direction A. The rate or slope of this decrease can be matched to the absolute value of the slope of line127inFIG. 8. In another embodiment, for example, the rate of decrease could be calculated as
Rate of decrease=(ΔT/stage 152)−(ΔT/stage 162)/(ΔT/stage 152)  Eqn 1

Other methods may be used for calculating the rate of decrease as well. In addition, the rate of decrease can also include e.g., a non-linear rate of decrease.

By decreasing the magnetic flux provided by magnetic element126as described above, the amount of work associated with cycling working units112through the magnetic field can be decreased—resulting in more efficiency in the operation of heat pump100. In addition, where magnetic element126is constructed from one or more magnets, the cost of manufacturing heat pump100and, therefore, appliance10can be substantially reduced.

Returning toFIGS. 4, 5, and 6, for this exemplary embodiment magnetic element126is constructed in the shape of an arc from a plurality of magnets130arranged in a Halbach array. More specifically, magnets130are arranged so that magnetic device126provides a magnetic field M located radially outward of magnetic device126and towards regenerator housing102while minimal or no magnetic field is located radially-inward towards the axis of rotation A-A. Magnetic field M may be aligned in a curve or arc shape. In addition, the thickness T of magnetic element decreases along a predetermined direction—axial direction A-A in this example—as also shown inFIG. 4.

A variety of other configurations may be used as well for magnetic device126and/or its resulting magnetic field. For example, magnetic device126could be constructed from a first plurality of magnets positioned in cavity128in a Halbach array that directs the field outwardly while a second plurality of magnets is positioned radially outward of regenerator housing102and arranged to provide a magnetic field that is located radially inward to the regenerator housing102. In still another embodiment, magnetic device128could be constructed from a plurality of magnets positioned radially outward of regenerator housing102and arranged to provide a magnetic field that is located radially inward towards the regenerator housing102. Other configurations of magnetic device128may be provided as well. For example, coils instead of magnets may be used to create the magnetic field desired.

For this exemplary embodiment, the arc created by magnetic device128provides a magnetic field extending circumferentially about 180 degrees. In still another embodiment, the arc created by magnetic device128provides a magnetic field extending circumferentially in a range of about 170 degrees to about 190 degrees.

A motor28is in mechanical communication with regenerator housing102and provides for rotation of housing102about axis A-A. By way of example, motor28may be connected directly with housing102by a shaft or indirectly through a gear box. Other configurations may be used as well.

In the description above, normal MCM was used to describe the operation of heat pump100. As will be understood by one of skill in the art using the teachings disclosed herein, inverse MCMs could also be used as well. The direction of flow of fluid through heat pump100would be reversed, accordingly.