the invention comprises a “ rotating magnet ” magnetic refrigerator ( rmmr ) which uses rotary disk valves to control flow to and from the beds where these valves are located coaxially with the shaft rotating the magnet assembly , and where a compression mechanism on the valve disks is adjustable after assembly of the valves , and maintains sealing as the disks wear . an overview of the arrangement of components of a first embodiment of this invention is shown in fig2 . fig2 shows a cross section of a two - bed system 1 , where a first bed 2 ( magnetized ) is within the gap 8 of the magnet assembly 6 while a second bed 4 ( demagnetized ) is outside the gap 8 of the assembly . a motor 10 ( which may be an electric motor ) rotates the central shaft 12 , which is mounted to bearings 102 , 104 , 106 and 108 , and passes through rotary seals 122 , 124 , 126 and 128 . this central shaft 12 also drives the rotors 14 , 16 , 18 , 20 in each of the coaxial valves 22 , 24 , 26 , 28 . a pump 30 drives fluid flow through the system 1 . in the configuration shown in fig2 , the rotor 14 in the hot inlet ( hi ) valve 22 uncovers the hole 32 connected to the hot inlet port 42 of the demagnetized ( lower ) bed 4 . at the same time , the rotor 16 in the cold outlet ( co ) valve 24 uncovers the hole 34 connected to the cold outlet port 44 of the bed 4 . thus , pressurized fluid emerging from the hot - side heat exchanger ( hhex ) 40 at temperature t hi is carried by a pipe 62 into a chamber 52 at one end of the hot inlet valve 22 , through the uncovered hole 32 in stator 88 of the hot inlet valve 22 and is driven into a hot inlet pipe 64 b and through the bed 4 from its hot inlet port 42 to its cold outlet port 44 . after passing through the cold ( demagnetized bed ) 4 , this fluid , now at temperature t co , is carried by a cold outlet pipe 66 b and collected by the open cold outlet valve 24 through the hole 34 in the stator 90 , and directed via the chamber 54 at one end of the valve 24 through pipe 92 to the cold - side heat exchanger ( chex ) 60 where the fluid absorbs heat from the refrigerated environment and rises in temperature to t ci . the cold inlet port 68 and cold inlet pipe 72 b of the demagnetized bed 4 are blocked by the rotor 16 position in the cold inlet ( ci ) valve 26 covering the hole 38 b , and the hot outlet port 70 and hot outlet pipe 82 b of the demagnetized bed 4 are also blocked by the rotor 20 position in the hot outlet ( ho ) valve 28 covering the hole 94 b . fluid at temperature t ci emerging from the other end of the cold - side heat exchanger 60 enters the single port 36 in the chamber 56 at one end of the cold inlet valve 26 . this fluid is directed through the cold inlet rotor 18 and through the hole 38 a in the stator 86 into a cold inlet pipe 72 a and to the cold inlet port 74 of the magnetized ( upper ) bed 2 . the fluid passes through the magnetized bed 2 from the cold inlet port 74 to the hot outlet port 78 and rises in temperature to t ho . flow through the cold outlet port 76 and cold outlet pipe 66 a of the bed 2 is blocked by the cold outlet valve 24 . flow through the hot inlet port 80 and hot inlet pipe 64 a of the bed 2 is blocked by the hot inlet valve 22 . hot outlet fluid at temperature t ho from the port 78 of the bed 2 is carried by a hot outlet pipe 82 a through a hole 94 a in the stator 96 into the hot outlet valve 28 , exits the valve 28 via the chamber 58 and returns via a pipe 84 to the pump 30 , where it gets directed through the other end of the hhex 40 , completing the flow circuit . although the figures show pipes that carry the fluid flow between components of the invention , any suitable conduits that carry the fluid between the components might be used . for example , the conduits might be fluid passages in an injection - molded assembly , or the conduits might be fluid passages in an assembly made by additive manufacturing , or the conduits could be pipes as shown in the drawings . the improvements to the valves of the first embodiment of this invention are shown in the detailed view of the hot side valves in fig3 . both the hot inlet valve 22 and hot outlet valve 28 are of similar construction . the hot outlet valve 28 contains a stator 96 that is fixed in position and sealed against the valve housing 210 . the hot outlet valve also contains a rotor 20 that rotates with the magnet 6 about the axis of the shaft 12 . the rotor 20 is centered by an o - ring 228 between its inner diameter ( id ) and a bushing 214 , and is mounted to a rigid valve cup 212 . the bushing 214 is individually assembled on the drive shaft 12 , and held in place by a pin 216 that extends through the shaft 12 , bushing 214 and into a slot 213 in the rigid cup 212 . the pin 216 provides precise axial location of the bushing 214 , and also transfers rotary torque from the shaft 12 to the rotating components of the valve . a threaded nut 218 supports springs 220 that apply compression force against the rigid cup 212 . the rigid cup can move along the axis of the shaft 12 and bushing 214 as the pin 216 slides in the slot 213 and thus transmit compressive force to the rotor 20 , but the engagement of the pin 216 in the slot 213 and in the shaft 12 ensures that rotary torque is transmitted from the shaft 12 to the rigid cup 212 and the rotor 20 . an external access port 222 allows adjustment of compression without disassembly of the valve . external access ports 222 and slots 221 in the threaded nut 218 allow adjustment of compression without disassembly of the valves . the adjustment is done by rotation of the shaft 12 while the threaded nut 218 is held fixed by a tool inserted through the access port 222 . bearings 102 and 104 are incorporated into the valve housings . this allows a compact design , allows compression loading of the outer nut 224 against the outer bearing 102 and guarantees alignment in the valve bodies . the inner bearing 104 is seated against a retaining ring 226 that is attached to the shaft 12 . as the valve rotor 20 and valve stator 96 of the valve 28 wear during operation of the valve , their combined thickness will be reduced . however , the springs 220 will accommodate this change in thickness and maintain sealing of the valve disks without need for external adjustment . an overview of the arrangement of components of a second embodiment of this invention is shown in fig4 . the valves perform the same time - sequenced flow allocation between the same conduits as the first embodiment . the difference is that the stator 86 and rotor 18 of the cold inlet valve 26 are inverted left to right , and the stator 88 and rotor 14 of the hot inlet valve 22 are inverted left to right , allowing the stator 88 for the hot inlet valve 22 and the stator 96 for the hot outlet valve 28 to be mounted to a common assembly 98 ; the stator 86 for the cold inlet valve 26 and the stator 90 for the cold outlet valve 24 also can be mounted to a common assembly 100 . the magnet assembly 6 , the beds 2 , 4 , and the pump 30 are in similar positions in the first and second embodiments . by mounting the stators 88 and 96 on opposed walls , the forces needed to compress the rotors 14 and 20 to their stators 88 and 96 are counter - acting , and the forces needed to compress the rotors 16 and 18 to their stators 90 and 86 are counteracting , thus reducing loads on the shaft 12 and simplifying the design . an overview of the component arrangement of another embodiment of this invention is shown in fig5 . the third embodiment has the same components as the second embodiment , and the components such as the motor 10 perform the same functions in the same manner as the second embodiment . the difference is that magnet assembly 6 and beds 2 , 4 in the first and second embodiments are located between the hot inlet valve 22 and cold inlet valve 26 at a similar radius , while the magnet assembly 6 and beds 2 and 4 of the third embodiment are located outside the valves 22 , 26 at a larger radius , allowing the length of the assembly 1 to be reduced . note that in fig5 , the hot outlet pipes 82 a , 82 b are each the same length and shape , and the cold inlet pipes 72 a , 72 b are also each the same length and shape , although the hot outlet pipe 82 a is a different length and shape from the cold inlet pipe 72 a . in fig2 , 4 and 5 , all the pipes of the same function , such as hot outlet , are the same length , although pipes of different function , such as hot outlet and cold inlet , may be of different length . more generally , conduit pairs , such as cold inlet pipe 72 a in series with and hot outlet pipe 82 a , and cold inlet pipe 72 b in series with hot outlet pipe 82 b ( first conduit pairs ), or being hot inlet pipe 64 a in series with cold outlet pipe 66 a and hot inlet pipe 64 b in series with cold outlet pipe 66 b ( second conduit pairs ), are configured for equal or balanced flow among all similar conduit pairs . this is provided by ensuring that the conduit pairs provide equal steady - state flow resistance , but also by addressing dynamic factors such as flow inductance by setting equal the total internal volume of the conduit pairs , and flow capacitance by ensuring that the change in internal volume with changes in pressure is equal for the conduit pairs . these values may also be identical but need not be identical when the first conduit pairs are compared to the second conduit pairs . the improvements to the valves of the second embodiment of this invention are shown in the detailed view of the hot side valves in fig6 . both the hot inlet valve 22 and hot outlet valve 28 are of similar construction . the hot outlet valve 28 contains a stator 96 that is fixed in position and sealed against the valve housing 210 . each port in the stator is mated with a stub - tube 205 protruding from the floor of the valve housing . each stub tube has an o - ring seal 204 to the stator . the hot outlet valve also contains a rotor 20 that rotates with the magnet 6 about the axis of the shaft 12 . the rotor 20 is centered by an o - ring 228 between its id and an inner rotating assembly 201 , and is mounted to a rigid valve cup 212 . the drive shaft 12 passes coaxially through the inner assembly 201 that is connected to the rotor 20 and the compression assembly 230 . the compression assembly 230 is comprised of a threaded nut 218 that supports springs 220 that apply compression force against the rigid cup 212 and rotor 20 . the rigid cup 212 may be a carbon composite material . external access ports 222 allow adjustment of compression without disassembly of the valves . the inner rotatable assembly 201 has commercial ceramic ( or other material ) rotary face seals 202 mounted at each end to seal the fluid inside the valve body comprised of valve housing 210 and end plate 310 and prevent fluid from reaching the drive shaft 12 . in this way the driveshaft remains ‘ dry ’ and can be separated from the valve without breaking the seal in the bodies . this feature allows the hot inlet and outlet valves to be assembled , or removed and replaced without disturbing the cold inlet and outlet valves , or the bed and magnet assembly . the inner rotating assembly consists of two pieces , sealed in the center by an o - ring 232 and held in place by threaded screws 203 . a special key 208 is fitted into a slot of the driveshaft and mates with a slot in the inner bore of the inner rotatable assembly 201 . the key 208 provides torque transfer from the driveshaft 12 to the inner rotatable assembly 201 . the key 208 also provides precise axial position control of the inner rotatable assembly 201 relative to the driveshaft 12 . the shank of the key 208 is designed so that it fits flush in its slot ( within the diameter of the shaft 12 ). this allows the seals 202 to run adjacent to the key 208 without interference . the key 208 is co - threaded with the drive shaft 12 , so that its axial position is rigidly locked when the outer nut 209 is assembled . the key 208 rigidly couples the inner rotatable assembly 201 to the drive shaft 12 . this allows the inner rotatable assembly 201 position to be accurately determined . it also allows unbalanced compression forces on the opposing valve surfaces while maintaining correct axial positions . bearings 102 and 104 are incorporated into the valve housings . this allows a compact design , allows compression loading of the outer nut 209 against the outer bearing 102 and guarantees alignment in the valve bodies . the inner bearing 104 is seated against a retaining ring 226 that is attached to the shaft 12 . as the valve rotor 20 and valve stator 96 of the valve 28 wear during operation of the valve , their combined thickness will be reduced . however , the springs 220 will accommodate this change in thickness and maintain sealing of the valve disks without need for external adjustment . even as the valves wear and potentially accumulate damage , leakage that bypasses the heat exchanger 40 would require both valves 22 and 28 and optional auxiliary seals 234 to leak , as can be seen in fig6 . another embodiment of this invention is shown in fig7 . the fourth embodiment has the same components as the third embodiment , and the components such as the motor 10 perform the same functions in the same manner as the third embodiment . the difference is that the stators 88 , 86 of the hot inlet 22 and cold inlet 26 valves are mounted to a common assembly 101 , allowing for shorter hot inlet piping 64 a , 64 b and cold inlet piping 72 a , 72 b to the beds 2 , 4 than is possible for the first three embodiments . additional variants for the above embodiments may be created by replacing the cold side inlet and outlet valves by one - way valves . examples of one - way valves that might be used in the invention are check valves and reed valves . a one - way valve , also known as a check valve , allows fluid flow in only one direction and blocks fluid flow in the opposite direction . for example , a ball check valve uses a spherical ball to block the flow of fluid in one direction . a conically tapered seat will place the ball within the valve opening to prevent flow in one direction , but allow flow in the opposite direction when the ball is displaced from its seat . placement of the ball within the seat may be aided by a spring . other types of one - way valves include diaphragm check valves , swing check valves , tilting disc check valves , stop - check valves , lift - check valves , in - line check valves , duckbill valves , pneumatic non - return valves , etc . one - way valves can be smaller and less expensive than rotary disk valves . an example of another embodiment using one - way valves is shown in fig8 , where the cold side valves 24 , 26 of embodiment 2 in fig4 have been replaced by check valves 120 , 121 , 125 , and 127 in fig8 . fig9 shows details on how the connection might be made between one end of a bed and the inlet and outlet pipes coming from a valve . the cold inlet pipe 72 b and cold outlet pipe 66 b come in from the top of the figure and enter a bed plenum assembly 110 . the cold inlet pipe 72 b terminates at a cold inlet port 68 and the cold outlet pipe 66 b terminates in a cold outlet port 44 that connect at a rectangular opening 112 that can be attached to one side of a bed , such as the bed 4 of fig2 . the bed is not shown in fig9 . although two - bed embodiments are shown in fig2 through 8 , it is usually advantageous to fit additional beds in the path swept by the magnet gap . the additional beds increase the cooling power and can make more efficient use of the magnet assembly . the valves may be designed to allow flow in a given direction to multiple beds at the same time . for example , an eight - bed version of the first embodiment is shown as an end view from the cold end in fig1 . not shown are the cold inlet pipes , the hot inlet and outlet pipes , the valve housings and seals , the hex &# 39 ; s , the pump , the motor , and the bearings . the magnet assembly 6 and the cold outlet valve rotor 16 are connected to the shaft 12 and rotate with it . the magnet assembly is shown over two magnetized beds 2 a , 2 b , which are both under flow from their cold ends to their hot ends . two demagnetized beds 4 a , 4 b are in the lowest field region and both are under flow from their hot ends to their cold ends , and four remaining beds 3 a , 3 b , 3 c , and 3 d at intermediate fields are not under flow . each bed is attached to a cold side plenum assembly 110 and a hot side plenum assembly 111 . together these plenums create a manifold about the bed . the cold outlet valve rotor 16 is shown exposing two holes 34 a , 34 b in the cold outlet valve stator 90 , allowing flow to leave the demagnetized beds 4 a , 4 b through the cold outlet ports 44 a , 44 b and the cold outlet pipes 66 a , 66 b which are attached to the cold side plenum assemblies 110 a , 110 b . meanwhile , the cold outlet valve rotor 16 is blocking the holes 34 c , 34 d , 34 e , 34 f , 34 g and 34 h , thereby blocking flow from the cold outlet ports of beds 2 a , 2 b , 3 a , 3 b , 3 c , and 3 d . note that the flow situation of fig1 can be implemented using cold inlet , cold outlet , hot inlet and hot outlet valve rotors that each exposes two holes in their matching stator at a time . although fig1 shows a situation where two beds are simultaneously under flow from cold to hot and two beds are under flow from hot to cold , there are four beds that are not under flow and thus are not contributing to the cooling of the device . if the cold outlet and hot inlet valve rotors expose more holes in their matching stators than the cold inlet and hot outlet valves , then more beds will be subjected to hot to cold flow than will be subjected to cold to hot flow . fig3 and 6 show improved valve assemblies where the hot inlet and hot outlet flow control functions are controlled by two distinct valve assemblies that are driven by a single shaft . use of separate valve assemblies for hot inlet and outlet flows minimizes the possibility of thermal heat leakage or fluid leakage that bypasses the hot heat exchanger . however , use of two separate valve assemblies doubles the parts count and increases the cost of manufacture , and also increases the length of the system along the shaft axis . fig1 shows an improved valve configuration that combines the switching of hot inlet and hot outlet flows in a single hot inlet / outlet valve assembly 270 . the hot valve 28 contains a stator 96 that is fixed in position and sealed against the valve housing 210 . the hot valve also contains a rotor 20 that rotates with the magnet 6 about the axis of the shaft 12 . the rotor 20 is centered by an o - ring 228 between its id and a bushing 214 , and is mounted to a rigid valve cup 212 . the bushing 214 is assembled on the drive shaft 12 , and held in place by a pin 216 that extends through the shaft 12 , bushing 214 and into a slot 213 in the rigid cup 212 . the pin 216 provides precise axial location of the bushing 214 , and also transfers rotary torque from the shaft 12 to the rotating components of the valve . a threaded nut 218 supports springs 220 that apply compression force against the rigid cup 212 . the rigid cup can move along the axis of the shaft 12 and bushing 214 as the pin 216 slides in the slot 213 and thus transmit compressive force to the rotor 20 , but the engagement of the pin 216 in the slot 213 and in the shaft 12 ensures that rotary torque is transmitted from the shaft 12 to the rigid cup 212 and the rotor 20 . an external access port 222 allows adjustment of compression without disassembly of the valve . bearings 102 and 104 are incorporated into the valve housing . this allows a compact design , allows compression loading of the outer nut 224 against the outer bearing 102 and guarantees alignment in the valve body . the inner bearing 104 is seated against a retaining ring 226 that is attached to the shaft 12 . as the valve rotor 20 and valve stator 96 of the valve 28 wear during operation of the valve , their combined thickness will be reduced . however , the springs 220 will accommodate this change in thickness and maintain sealing of the valve disks without need for external adjustment . a motor ( not shown ) rotates the central shaft 12 . in the position shown in fig1 , hot outlet fluid at temperature t ho from the port 78 of the bed 2 that is inside the magnet 6 is carried by a hot outlet pipe 82 a at an intermediate radius through a hole 94 a in the stator 96 into the hot outlet valve 28 , flows through a slot 264 in the rotor 20 to a hole 266 in the inner radius of the stator 96 , and flows just outside the shaft 12 into an inner plenum 272 . the fluid exits the inner plenum 272 through a pipe 84 to the inlet of the pump 30 , which pumps the fluid through the hot hex 40 and through a pipe 62 into the outer plenum 52 of the valve 28 . the fluid in the outer plenum 52 can enter the slot 262 in the rotor 20 and proceed through a hole 32 a at an outer radius in the stator disk 96 and through a pipe 254 to the hot inlet 42 of the bed 4 that is outside the magnet 6 . in the rotational position shown in fig1 , flow through the hot inlet port 80 and hot inlet pipe 64 a of the magnetized bed 2 is blocked by the hot valve rotor 20 covering the hole 32 b . the hot outlet port 70 and hot outlet pipe 82 b of the demagnetized bed 4 are also blocked by the rotor 20 position covering the hole 94 b . fig1 a and 13a shows plan views of a rotor disk 20 and stator disk 96 , respectively , that can be used in the hot inlet / outlet valve assembly 270 shown in fig1 . slots 264 and 266 in the rotor disk are shown . also shown are holes 32 a , 94 b , and 266 in the stator disk . fig1 b shows a cross section of the rotor disk 20 taken at the line a - a shown in fig1 a , and fig1 b shows a cross section of the stator disk 96 taken at the line b - b shown in fig1 a . slots 264 and 266 in the rotor disk are shown in fig1 b . holes 32 a , 94 b , and 266 in the stator disk are also shown in fig1 b . fig1 shows in an end view how the rotor disk 20 and stator disk 96 can be stacked with their surfaces in contact , allowing flow to be directed between the slots and different holes as the rotor 20 rotates with respect to the stator 96 . fig1 shows details of a bushing , pin and valve cup that can be used in the improved valve assemblies of fig3 or 11 . the bushing 214 is assembled on the drive shaft 12 ( not shown in fig1 ), and held in place by a pin 216 that extends through the shaft 12 , bushing 214 and into a slot 213 in the rigid cup 212 . the pin 216 provides precise axial location of the bushing 214 with respect to the shaft 12 , and also transfers rotary torque from the shaft 12 to valve cup 212 and other rotating components of the valve . fig1 shows an exploded view of the compression assembly that can be used in the improved valve assemblies of fig3 or 11 . the valve compression assembly 230 is comprised of a threaded nut 218 ( or spring support ) that supports springs 220 that apply compression force against the rigid cup 212 ( or contacted valve plate ) connected to rotor 20 ( not shown ). the springs 220 are held in place by the ring 215 which fits inside the rim 211 on the rigid cup 212 . it is understood that the ring 2015 could be moved to the opposite side of the springs 220 while performing a similar function . referring also to fig1 , the springs 220 , which may be compression springs , are positioned between the ring 215 on one side and the threaded nut 218 on the opposite side , and the position of the threaded nut 218 may be adjustable to control a force of the springs 220 on the rigid cup 212 applied via the ring 215 . it is understood that the springs 220 may be replaced with any elastic object used to store mechanical energy as is known in the art . the rigid cup 212 may be held within the plenum receiving a fluid controlled by the valve and where the springs 220 may be adjustable by rotation on a threaded element coaxial about the shaft 12 . the plenum may include a sealable opening allowing access to the threaded nut 218 for rotation of the threaded nut 218 with respect to the threaded element to move the threaded nut 218 axially along the shaft 12 . the rigid cup 212 may cooperate to , in a first position present a passage of fluid to a first plenum communicating with an outer periphery of at least one rigid cup 212 and in a second position to present a fluid passage to a fluid and a second plenum separated from the first plenum communicating with an inner periphery of at least one rigid cup 212 . referring also to fig1 , a joint between the drive shaft 12 and the rigid cup 212 may provide an interengaging axial slot 213 and radial pin 216 . the bushing 214 is individually assembled on the drive shaft 12 , and held in place by a pin 216 inserted in the hole 217 in the bushing 214 . the pin extends through the shaft 12 , bushing 214 and into a slot 213 in the rigid cup 212 . the pin 216 provides precise axial location of the bushing 214 , and also transfers rotary torque from the shaft 12 to the rotating components of the valve . the rigid cup 212 can move along the axis of the shaft 12 and bushing 214 as the pin slides in the slot 213 and thus transmit compressive force to the rotor 20 , but the engagement of the pin in the slot 213 and in the shaft 12 ensures that rotary torque is transmitted from the shaft 12 to the rigid cup 212 and the rotor 20 . an external access port 222 ( not shown ) allows adjustment of compression without disassembly of the valve . slots 221 in the threaded nut 218 allow adjustment of compression without disassembly of the valves . the adjustment is done by rotation of the shaft 12 while the threaded nut 218 is held fixed by a tool inserted through the access port 222 . the rigid cup 212 may attach to the drive shaft 12 through the joint allowing angulation of the rigid cup 212 in addition to axial movement of the rigid cup 212 while preventing relative motion of the rigid cup 212 and shaft 12 in rotation about an axis of the shaft 12 . it s also possible to construct an improved valve assembly that combines the switching of hot inlet and hot outlet flows in a single hot valve and the switching of cold inlet and cold outlet flows in a single cold valve , for which the driveshaft remains ‘ dry ’. a detailed view of this improved dry shaft combined inlet and outlet valve assembly 280 is shown in fig1 . both the hot valve 28 and cold valve 24 are of similar construction . the hot valve 28 contains a stator 96 that is fixed in position and sealed against the valve housing 210 . each outer circle port 32 in the stator is mated with a tube 205 protruding from the floor of the valve housing . each inner circle port 94 in the stator is mated with a tube 295 protruding from the floor of the valve housing . each tube has an o - ring seal 204 to the stator and an o - ring seal 284 to the housing 210 . the hot valve also contains a rotor 20 that rotates with the magnet 6 about the axis of the shaft 12 . the rotor 20 is centered by an o - ring 228 in a clearance 223 between the id of the rotor 20 and the od of an inner rotating assembly 201 , and is mounted to a rigid valve cup 212 . the drive shaft 12 passes coaxially through the inner assembly 201 that is connected to the rotor 20 and the compression assembly 230 . the compression assembly 230 is comprised of a threaded nut 218 that supports springs 220 that apply compression force against the rigid cup 212 and rotor 20 . external access ports 222 and slots 221 in the threaded nut 218 allow adjustment of compression without disassembly of the valves . the adjustment is done by rotation of the shaft 12 while the threaded nut 218 is held fixed by a tool inserted through the access port 222 . the centering action of the o - ring 228 in the clearance 223 and the application of axial force by the springs 220 keeps the rotor 20 sealed against the stator 96 even if the valve components were constructed with eccentricities or wear during operation . the inner rotatable assembly 201 has two commercial ceramic rotary face seals 202 and 282 mounted at each end to seal the fluid inside the valve body and prevent it from reaching the drive shaft 12 . in this way the driveshaft remains ‘ dry ’ and can be separated from the valve without breaking the seal in the bodies . this feature allows the hot inlet and outlet valves to be assembled , or removed and replaced without disturbing the cold inlet and outlet valves , or the bed and magnet assembly . the shaft 12 may communicate with the rigid cup 212 by means of a special key 208 joining a key way and key seat on the shaft 12 and rigid cup 212 . the special key 208 is fitted into a slot of the driveshaft and mates with a slot in the inner bore of the inner rotatable assembly 201 . the key 208 provides torque transfer from the driveshaft 12 to the inner rotatable assembly 201 . the key 208 also provides precise axial position control of the inner rotatable assembly 201 relative to the driveshaft 12 . the shank of the key 208 is designed so that it fits flush in its slot ( within the diameter of the shaft 12 ). this allows the seal 202 to run adjacent to the key 208 without interference . the key 208 is co - threaded with the drive shaft 12 , so that its axial position is rigidly locked when the outer nut 209 is assembled . the key 208 rigidly couples the inner rotatable assembly 201 to the drive shaft 12 . this allows the position of the inner rotatable assembly 201 to be accurately determined . it also allows unbalanced compression forces on the opposing valve surfaces while maintaining correct axial positions . removal of the valve assembly 28 from the shaft 12 can be accomplished by unscrewing the nut 224 from the shaft 12 , then sliding the housing 210 with the key 208 and the valve internal components along the shaft 12 in a direction away from the retaining ring 226 , with the tubes 205 and 295 sliding out of the o - rings 286 and 296 . the key 208 extends to an end of the shaft 12 to allow extraction of the key 208 in a first direction from a first end of the shaft 12 and extraction of the shaft 12 in a second direction opposite the first direction . bearings 102 and 104 are incorporated into the hot valve housing . this allows compact design , allows compression loading of the outer nut 209 against the outer bearing 102 and guarantees alignment in the valve body . the inner bearing 104 is seated against a retaining ring 226 that is attached to the shaft 12 . the outer circle of tubes 205 connect to inlet ports 288 of the beds , and are sealed by o - rings 286 . the inner circle of tubes 295 connect to outlet ports 298 of the beds , and are sealed by o - rings 296 . the cold valve 24 can use the same method of construction as the hot valve , as is shown in fig1 . a motor 10 drives the rotation of the shaft 12 , which in turn drives the rotation of both the rotor 20 of the hot valve 28 and the rotor 18 of the cold valve 24 . the motor also drives the rotation of the magnet 6 . alternately , the cold flows can be controlled by one - way valves in a manner similar to that shown in fig8 . an advantage of the flow configuration shown in fig1 is that all of the tubes ( such as 205 and 295 ) carrying flow from the valves to the individual beds can be short and of equal length and shape . this feature of the tubes reduces pressure drop and aids in achieving uniform flow timing and distribution between the beds . the design configuration of fig1 that combines the inlet and outlet valve functions in a single coaxial assembly will allow the construction of cooling units with a shorter overall length than that achievable with separate inlet and outlet valves in a coaxial assembly . the same advantage applies to the design configuration shown in fig1 . a shorter length cooling unit is more easily incorporated in products that need to fit in locations with limited space . referring to fig6 , 17 and 18 , the shaft 12 may pass through a plenum receiving fluid from a valve and may be separated from the plenum by a rotary seal 202 or sleeve assembly . the rotary seal 202 may include a first and second sleeve portion over different axial portions of the shaft each portion including a sliding seal communicating with a corresponding sliding seal of the other portion allowing relative rotational movement of the first sleeve portion with respect to the second sleeve portion about the axis . the sliding seal may include a spring 306 biasing the first and second seal portion into engagement to prevent leakage therebetween . fig1 shows details of a rotary seal 202 that can he used in the dry shaft improved valve assemblies of fig6 or 17 . the seal 202 contains of a fixed cup 302 that is glued to the fixed end plate 310 ( fig6 ) of the valve . the fixed cup 302 is also connected by a bellows seal 307 and spring 306 to a fixed seal ring 304 . the fixed seal ring 304 engages and seals with a rotating seal ring 308 that is sealed to a rotary seal gasket 312 that seals against the rotating assembly 201 ( fig6 ) of the valve . this sealing arrangement keeps fluid inside the valve from leaking from the interior of the valve body or reaching the dry shaft 12 ( fig6 ) of the valve . the seal 282 of fig1 is of identical construction to seal 202 . the magnet assemblies shown in the above embodiments are a single lobe design , with one high field region , and an opposite low field region . however , it may be advantageous to employ magnet assemblies with multiple high field regions and multiple low field regions . for such cases , co - axial disk valves could be implemented with additional slots that direct cold to hot flow simultaneously to beds in multiple high field regions , and direct hot to cold flow simultaneously to beds in multiple low field regions . by placing the valves in rotational sliding communication and coaxially with the main drive shaft , the need for connecting belts and pulleys between this shaft and the valve shafts is eliminated . these belts and pulleys waste energy provided by the motor , so their elimination improves the energy - efficiency of the mr system . the belts and pulleys take up space , so their elimination also results in a smaller , more compact system . moreover , the coaxial valve placement reduces the length of the fluid conduits ( commonly called pipes ) connecting the valves and the fixed beds . note that this invention allows the use of separate inlet and outlet pipes on both the cold and hot sides for each bed . by using separate inlet and outlet pipes with unidirectional flow in each pipe , all the fluid that enters the pipe eventually will reach the destination bed or destination heat exchanger . thus the fluid contained in the pipes will contribute to the operation of the amr cycle and not represent “ dead volume ”. however , even with separate inlet and outlet pipes , the shorter pipe lengths possible with the coaxial valves still offer two advantages . first , the shorter length reduces the pressure drop experienced by the fluid as it flows through the pipe through the conduit , that is , the fluid resistance of the pipe to steady flow is reduced . this reduces the load on the pump and further improves the energy efficiency of the system . second , the shorter pipe lengths reduce the magnitude of bypass flow , a phenomenon in which fluid bypasses the beds and proceeds directly from the hot inlet valve to the hot outlet valve . bypass flow does not contribute to refrigeration and therefore wastes energy provided by the pump ; its reduction therefore improves the energy efficiency of the mr system . bypass flow is caused , in part , by periodic expansion of a deformable plumbing element under pressurization , followed by fluid expulsion under depressurization , a form of fluid capacitance for the plumbing element . to explain this bypass flow mechanism , we refer to fig2 . the hot inlet fluid is at the highest pressure in the fluid circuit . under this pressure , the pipe 64 b connecting the hot inlet valve 22 to the hot inlet port 42 of the demagnetized bed 4 will expand slightly , storing some fluid that would otherwise pass through the bed 4 . after the cold blow is completed , the hi and co valves 22 , 24 seal off the hot inlet pipe 64 b of this bed 2 , preventing the stored fluid from leaving the hot inlet pipe 64 b . when the valves rotate for the hot blow , the hot outlet pipe 82 b connected to the bed 4 can now carry flow , so the pressurized fluid stored in the hot inlet pipe 64 b can be expelled through the hot outlet pipe 82 b and into the hot outlet valve 28 , allowing the hot inlet pipe 64 b to return to its original shape . this cyclical process of pressurization , expansion , and fluid storage during the cold blow , followed by fluid expulsion and depressurization during the following hot blow , produces bypass flow . the amount of fluid that can be stored during the cold blow increases with the length of pipe connecting the hot inlet valve to the hot inlet port of a bed . the coaxial valve placement minimizes this conduit length , minimizing the increase in fluid volume during pressurization , thus minimizing bypass flow and improving system performance . for best operation of an amr system , the change in internal fluid volume of a conduit to a bed when subjected to the increase from the minimum to the maximum fluid pressures during the amr cycle should be less than 5 % of the total fluid volume delivered to a single bed during the time interval in one amr cycle that the conduit pair is delivering flow to that bed . an additional advantage of the coaxial valve arrangement is that it allows the conduits of a similar flow function connecting the beds to the valves to be symmetrically placed around the shaft axis and to be of identical shape and length . there are four flow functions for conduits connecting the beds to the valves : hot inlet , hot outlet , cold inlet , and cold outlet . two pipes that each conduct hot inlet flow both have a similar function , although they might be connected to different beds . for an example of symmetrical placement and identical shape , in fig2 , if the two beds 2 and 4 shown in the figure are located at a 180 degree rotational angle from each other around the axis of the shaft 12 , and the ports 38 a and 38 b in the cold inlet valve are also located at a 180 degree angle from each other around the same axis , then the two cold inlet pipes 72 a and 72 b can be identical components of identical shape and length , but mounted at a 180 degree angle from each other around the axis of the shaft 12 . in addition to saving fabrication cost , the identical shape and length of conduits of a similar flow function ensures that the resistance of the conduits to steady flow will be equal . in addition , if the conduits of a similar flow function are of identical shape and length and wall thickness , then the conduits of similar function will have equal change in internal fluid volume when subjected to the increase from the minimum to the maximum fluid pressures during the amr cycle . finally , if the conduits of a similar flow function have the same internal cross section as well as identical shape and length , the conduits will have equal internal fluid volume , the mass of fluid stored in the conduits will be identical , and thus the dynamic pressure drop needed to accelerate fluid flow at the start of the fluid blow will be equal . the equivalent characteristics of conduits of a similar flow function thus ensure that the pressure drop due to flow friction , and the flow transient effects due to conduit expansion and fluid inertia , will be identical for all the beds . this helps ensure that all the beds get similar flow versus time profiles during an amr cycle , which can improve efficiency and temperature span . the flow from the hot outlet valve to the pump in the first three embodiments ( fig2 , 4 , and 5 ) only occurs in one direction , from the valve to the pump , and is thus unidirectional flow . although this invention enables conduits of a similar flow function to be of equal length , conduits of dissimilar flow function , such as hot outlet and hot inlet , may be of different length . the flow from an outlet valve to the pump in the embodiments described above only occurs in one direction , from the valve to the pump , and is thus unidirectional flow . this means that the fluid contained in the pipe 84 between the hot outlet valve 28 and the pump 30 in fig2 , for example , does not contribute to dead volume losses , and thus the pump 30 can be located outside the coaxial valve and bed assembly . this allows the use of any convenient type of pump . in particular , positive displacement pumps , such as gear pumps , screw pumps , piston pumps , diaphragm pumps , rotary vane pumps and scroll pumps can be used . positive displacement pumps produce a flow that is nearly constant over a wide range of operating pressures . the use of a positive displacement pump allows the flow rate to quickly reach intended levels as the flow is switched between different amr beds . in addition , efficient positive displacement pumps can be made over a wide range of flow capacity and pressure capacity , while centrifugal pumps , a common form of non - positive displacement pump , are only efficient at relatively large flow capacity or low pressure capacity . efficient heat transfer in amr beds requires a large internal heat transfer area , which tends to lead to high operating pressures , which are not well suited to efficient operation of centrifugal pumps for small to medium scale systems . if hot to cold flow or cold to hot flow occurs to only one bed at a time , the use of a positive displacement pump may require either precise valve timing to ensure flow is not blocked for a period of time , or alternately , the use of a fluid accumulator at the pump outlet . although the description of the present invention above has been based on the use of rotary disk valves , it is clear that other valve types that also rely on rotary motion to open and close desired fluid paths could be used and fall within the scope of the present invention . certain terminology is used herein for purposes of reference only , and thus is not intended to be limiting . for example , terms such as “ upper ”, “ lower ”, “ above ”, and “ below ” refer to directions in the drawings to which reference is made . terms such as “ front ”, “ back ”, “ rear ”, “ bottom ” and “ side ”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion . such terminology may include the words specifically mentioned above , derivatives thereof , and words of similar import . similarly , the terms “ first ”, “ second ” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context . when introducing elements or features of the present disclosure and the exemplary embodiments , the articles “ a ”, “ an ”, “ the ” and “ said ” are intended to mean that there are one or more of such elements or features . the terms “ comprising ”, “ including ” and “ having ” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted . it is further to be understood that the method steps , processes , and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated , unless specifically identified as an order of performance . it is also to be understood that additional or alternative steps may be employed . it is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims . all of the publications described herein , including patents and non - patent publications , are hereby incorporated herein by reference in their entireties .