Abstract:
The device ( 10 ) for continuous generation of cold and heat by the magneto-calorific effect, comprises a chamber ( 11 ), divided into two adjacent compartments ( 12, 13 ), separated by a wall ( 14 ). The chamber ( 11 ) contains a rotating element ( 15 ) made from at least one magneto-calorific material, a first circuit ( 17   a ) with a first heat exchange fluid circulating therein and a second circuit ( 17   b ) with a second heat exchange fluid circulating therein. The chamber ( 11 ) is connected to magnetic device ( 16 ) for generating a magnetic field in the region of the compartment ( 12 ) in which the rotating element ( 15 ) is located. When the above is set in rotation the part thereof located in the first compartment ( 12 ) is magnetized upon undergoing an increase in temperature. On passing into the second compartment ( 13 ), the part is demagnetized upon undergoing a cooling. The heat and the cold thus generated are transmitted by the heat exchange fluids respectively to user circuits for heat ( 19 ) and cold ( 22 ) for recovery and use for ulterior purposes.

Description:
TECHNICAL DOMAIN  
       [0001]     The present invention concerns a method for continuous generation of cold and heat by means of the magneto-calorific effect using at least one heat exchanger.  
         [0002]     It further concerns a device for continuous generation of cold and heat by means of the magneto-calorific effect comprising at least one heat exchanger.  
       PRIOR ART  
       [0003]     Conventional cold generating devices usually comprise a compressor which compresses a refrigerant in order to raise its temperature and a detainment means to decompress said refrigerant in order to cool it adiabatically. Refrigerants in current use have proven to be extremely polluting and their use entails considerable atmospheric pollution. Because of this, these refrigerants no longer meet current environmental protection requirements.  
         [0004]     Devices using the magneto-calorific effect to generate cold are already known in the art. In particular, U.S. Pat. No. 4,674,288 describes a helium liquefaction device comprising a magnetizable substance moving within a magnetic field generated by a coil and a helium reservoir that is in thermal conduction with said coil. The translational movement of the magnetizable substance generates cold that is transmitted to the helium through the intermediary of conductive elements.  
         [0005]     French Publication No. FR-A-2.525.748 has as its objective a magnetic refrigeration device comprising a magnetizable material, a system for generating a variable magnetic field, and a means for transferring heat and cold comprising a chamber filled with a saturated liquid refrigerant. The magnetizable material generates cold in a position wherein the cold transfer means extract cold from the magnetizable material by condensing a refrigerant, and the magnetizable material generates heat in another position wherein the heat transfer means extract heat from the magnetizable material by boiling another refrigerant.  
         [0006]     French Publication No. FR-A-2.586.793 concerns a device comprising a substance which produces heat when it becomes magnetized and produces cold when it is demagnetized and a means for generating a variable magnetic field, said means for generating a magnetic field comprising a superconductive coil and a reservoir containing a cooling element.  
         [0007]     These systems are extremely unreliable and are therefore not competitive with current refrigeration systems.  
         [0008]     U.S. Pat. No. 3,108,444 describes a magneto-calorific refrigeration apparatus comprising a wheel composed of superconductive elements passing alternately through a hot circuit, a cold circuit, and a space subjected to a magnetic field. The object of this device is to generate extremely low temperatures, of the order of 4° Kelvin. This type of equipment is not adaptable for household use and does not function at ambient temperature or temperatures of about 0° Celsius.  
         [0009]     U.S. Pat. No. 5,091,361 has as its object a heat pump using reverse magneto-calorific effect. The heat pump comprises a paramagnetic or ferromagnetic material alternately exposed to a very highly magnetized field. Such a system cannot be used for a domestic application, for example in a conventional refrigeration system running at temperatures approximating 0° Celsius.  
       DESCRIPTION OF THE INVENTION  
       [0010]     The present invention proposes a cooling method and device to overcome the disadvantages of known systems, using no polluting liquid refrigerants and thus eliminating the drawbacks of prior art systems.  
         [0011]     This goal is achieved by the method of the invention as defined in the preamble and characterized in that a first heat-transmitting fluid is circulated in a first circuit, called the hot circuit, connected to a first compartment of an enclosure containing a rotating element and a second heat-transmitting fluid in a second circuit, called the cold circuit, connected to a second compartment of said enclosure, said compartments being juxtaposed and separated by a partition, said enclosure being associated with a magnetic means to generate a magnetic field in said first compartment, at least in the area corresponding to said rotating element, and said rotating element comprising at least one magneto-calorific material which undergoes a temperature increase when it passes through said first compartment subjected to the magnetic field, and cools down when it passes through said second compartment that is not subjected to the magnetic field, in that heat is extracted from said first circuit using a first heat exchanger located in said circuit and connected to a heat utility circuit, and in that cold is extracted from said second circuit using a second heat exchanger located in said circuit and connected to a cold utility circuit.  
         [0012]     Advantageously, the first and second heat-transmitting fluids circulate in the same direction or the reverse direction through the compartments in the enclosure.  
         [0013]     Said first and second heat-transmitting fluids may be in either the liquid or gas state. These fluids may be suspensions, mud-like, currently called “slurry,” or nanofluids, such as colloids or the like.  
         [0014]     With this method the position of the magnetic elements is reversed relative to the compartments in the enclosure in order to arbitrarily generate cold and heat in one of said compartments.  
         [0015]     This goal is also achieved by the device of the invention as defined in the preamble and characterized in that it comprises:  
         [0016]     an enclosure divided into a first and a second compartment that are juxtaposed and separated by a partition, said enclosure containing a rotating element attached transversely in relation to the compartments and turning on an axle disposed within the plane of said partition, so that it is simultaneously partially inside said first and second compartments.  
         [0017]     a first circuit called the hot circuit connected to said first compartment in said enclosure and comprising a first heat exchanger through which a first heat-transmitting fluid circulates, said first exchanger being connected to a heat utility circuit.  
         [0018]     a second circuit called the cold circuit connected to said second compartment in said enclosure and comprising a second heat exchanger through which a second heat-transmitting fluid circulates, said second exchanger being connected to a cold utility circuit; and  
         [0019]     magnetic elements which generate a magnetic field in said first compartment in at least the area corresponding to said rotating element, said rotating element comprising at least one magneto-calorific material designed to undergo a temperature increase when it passes through the first compartment subjected to the magnetic field and to cool down when it passes through the second compartment not subjected to the magnetic field.  
         [0020]     According to the preferred embodiment said magnetic elements may comprise permanent magnets, electromagnets or any other means for creating a magnetic field. They may also generate either a constant or a variable magnetic field.  
         [0021]     The device may comprise complementary magnetic elements designed to create an insulating magnetic field insulating the second compartment from the magnetic field generated by said magnetic elements.  
         [0022]     Advantageously, said magnetic elements are movable so they may be located in either a first position in which they generate a magnetic field in one of the compartments, or a second position in which they generate a magnetic field in the other of said compartments.  
         [0023]     In one embodiment said magnetic elements comprise first electromagnets for the creation of a magnetic field in said first compartment, second electromagnets for the creation of a magnetic field in said second compartment, and a control means for the respective activation of the first or second electromagnets.  
         [0024]     Preferably the first and second heat exchangers are selected from the group consisting of liquid-liquid, liquid-gas, and gas-gas heat exchangers.  
         [0025]     In the preferred form of embodiment, the first circuit comprises a first pump and the second circuit comprises a second pump, the purpose of said pumps being to circulate the first and second heat-transmitting fluids, respectively, through each of these compartments.  
         [0026]     In all the variations, a unit of passageways traverses the rotating element, said passageways being provided for the circulation of said first and second heat-transmitting fluids inside said rotating element.  
         [0027]     According to a first embodiment, said rotating element may comprise a system of stacked discs made of different magneto-calorific materials, each disc comprising a unit of passageways communicating with the passageways of the adjacent disc or discs.  
         [0028]     According to a second embodiment, said rotating element may comprise a system of nested hollow cylindrical elements made of different magneto-calorific materials, each cylindrical element being traversed by a system of passageways.  
         [0029]     In a third embodiment, said rotating element comprises a system of nested angular sectors made of different magneto-calorific materials, said angular sectors being insulated from one another by thermal insulation elements, and each angular sector being traversed by a system of passageways.  
         [0030]     Said rotating element may also consist of a single cylindrical element made of magneto-calorific material, said cylindrical element comprising a system of passageways opening onto both of its surfaces.  
         [0031]     In one particular embodiment, said rotating element comprises walled angular sectors containing generally spherical grains consisting of at least one magneto-calorific material, said traversing passageways being defined by interstices formed between the grains.  
         [0032]     The traversing passageways may be defined by an alveolar structure or by hollow tubes located along the axle of the rotating element.  
         [0033]     In one particular embodiment, said traversing passageways are formed of a porous supporting structure with pores that are open and connected. 
     
    
     DESCRIPTIVE SUMMARY OF THE DRAWINGS  
       [0034]     The advantages of the present invention will be more apparent from the following description of various embodiments of the invention with reference to the attached drawings, wherein:  
         [0035]      FIG. 1  is a schematic view of one advantageous embodiment of the device of the invention;  
         [0036]      FIG. 2A  is a longitudinal cross-section of a portion of the device of  FIG. 1 ;  
         [0037]      FIGS. 2B and 2C  respectively illustrate transverse cross-sections of a portion of the device of  FIG. 1 ;  
         [0038]      FIGS. 3A and 3B  respectively illustrate variations in embodiments of the device of the invention;  
         [0039]      FIGS. 4 through 10  are axial cross-sections showing several embodiments of the rotating element of the device of the invention;  
         [0040]      FIG. 11  is a schematic longitudinal cross-section depicting another embodiment of the device of the invention; and  
         [0041]      FIG. 12  is a schematic view depicting an installation consisting of several of the devices of the invention connected in a cascading arrangement. 
     
    
     HOW TO ACHIEVE THE INVENTION  
       [0042]     With reference to  FIG. 1 , device  10  comprises an enclosure  11  comprising a first compartment  12  and a second compartment  13  that are juxtaposed and separated by a partition  14 . This enclosure houses a rotating element  15  consisting of a wheel turning on an axle  9  located generally within the plane of said partition  14 . A first circuit  17   a , called the hot circuit, is connected to first compartment  12  of the enclosure and comprises a first heat exchanger  18 , through which the heat-transmitting fluid circulates, said first exchanger  18  possibly being connected to a heat utility circuit  19  or simply designed to evacuate heat. A second circuit  17   b , called the cold circuit, is connected to second compartment  13  in the enclosure and comprises a second heat exchanger  21  through which a second heat-transmitting fluid circulates and which may be connected to a cold utility circuit  22  or combined with a refrigerated enclosure. Device  10  is equipped with magnetic elements  16  to generate a magnetic field in first compartment  12 , at least in the area corresponding to rotating element  15 . A first pump  23  is connected to the first circuit  17   a  and circulates the first heat-transmitting fluid through said first circuit, and a second pump  24 , connected to the second circuit  17   b , circulates the second heat-transmitting fluid through said second circuit.  
         [0043]     Rotating element  15  which consists, in this embodiment, of a single cylindrical element, is attached transversely in relation to the two compartments  12  and  13  so as to be simultaneously partially inside said first compartment  12  and said second compartment  13 . This rotating element  15  consists at least partially of at least one magneto-calorific material and comprises traversing passageways  25  opening onto its two surfaces and allowing the two portions of each compartment  12  and  13  situated on either side of rotating element  15  to communicate with each other. Rotating element  15  is rotated by means of a suitable drive motor. It rotates at a slower speed than the speed at which the heat-transmitting fluids circulate in the two circuits and in traversing passageways  25 . Because of this, only a very small portion of heat-transmitting fluid cooled in the portion of rotating element  15  that is outside the magnetic field penetrates the area subjected to the magnetic field, and vice-versa. The “loss” due to the transfer of fluid from one circuit to another by means of the rotating element is infinitesimal.  
         [0044]      FIGS. 2A, 2B  and  2 C illustrate in more detail the positioning of magnetic elements  16 . Enclosure  11  is provided with a partition  11   a  and comprises a central wall  14  that serves to define the two compartments  12  and  13  made of thermally insulating material, located in the median plane of enclosure  11 . This wall  14  is discontinuous and located in the plane of the rotation axle  9  of rotating element  15 . Each extremity of the two compartments  12  and  13  is open for connection to a conduit on the corresponding circuit of heat-conducting fluid. Magnetic elements  16 , which may consist of either permanent magnets or electromagnets, are located on either side of rotating element  15 , which is situated in first compartment  12 . For this reason, these magnetic elements  16  are preferably located below and in abutment with the median plane passing through wall  14 .  
         [0045]     Rotating element  15  is coaxially connected inside enclosure  11  to axle  9  passing through the median plane separating the two compartments  12  and  13 . This axle  9  is disposed to allow rotating element  15  to rotate using a drive motor (not shown). The diameter of rotating element  15  and the interior diameter of enclosure  11  are defined so that the two organs are separated by only a small space. This limits the volume of heat-transmitting fluid that can flow through this space while device  10  is operating. To accomplish this, rotating element may have on its periphery a seal, such as a gasket. Gaskets may also be placed on the interior edges of partition  14  to seal the two compartments  12  and  13 . Traversing passageways  25  in rotating element  15  open at their extremities onto each surface of element  15  so that its passageways communicate with each of the two portions of each compartment  12 ,  13  situated on either side of said rotating element  15 . These passageways  25  may be defined by an alveolar structure such as a honeycomb, or formed of hollow tubes parallel to axle  9  of rotating element  15 . They may also be defined by a porous structure made of the material of rotating element  15 .  
         [0046]      FIGS. 2B and 2C  show different constructions for device  10 . Magnetic elements  16  are either integral with wall  11   a , as shown in  FIG. 2B , or located outside this wall, as shown in  FIG. 2C .  
         [0047]     The operation of device  10  is based on the method wherein rotating element  15 , having been caused to rotate by means of a drive motor (not shown), the portion of said rotating element  15  situated in the magnetic field generated by magnetic elements  16  loses its entropy as it undergoes a temperature increase. At the same time the first heat-transmitting fluid in circuit  17   a , put into motion by first pump  19  and circulating in the opposite direction from the second heat-transmitting fluid in second circuit  17   b , enters the first compartment  12  at a given temperature T c1  and through the intermediary of traversing passageways  25 , crosses the portion of rotating element  15  subjected to the increase in temperature. The first heat-transmitting fluid in this portion of rotating element  15  undergoes a temperature increase due to heat transfer. At the outlet of first compartment  12 , the temperature T c2  of said heat-transmitting fluid is then higher than T c1 . The heat-transmitting fluid from heat utility circuit  19  enters first heat exchanger  18  at a temperature T cs1  and in turn undergoes a temperature increase due to heat exchange with the first heat-transmitting fluid that has traversed enclosure  11  and has been heated by passing through compartment  12 . The fluid from heat utility circuit  19  leaves said first heat exchanger  18  at a temperature T cs2  that is higher than temperature T cs1 . The heat stored in this heat-transmitting fluid can be used for any application. It can also be simply evacuated into the ambient atmosphere.  
         [0048]     While a first portion of rotating element  15  is subjected to rotation and undergoes a temperature increase when passing through the magnetic field generated by magnetic elements  16 , a second portion of rotating element  15  situated outside said magnetic field becomes demagnetized as it cools. When said first portion leaves the magnetic field due to rotation by the rotating element as it becomes demagnetized and cools, this second portion is in turn exposed to the magnetic field, loses its entropy, and undergoes a temperature increase. The portion previously subjected to a temperature increase leaves the magnetic field generated by magnetic elements  16  and becomes demagnetized as it cools down to a given temperature. At the same time, the second heat-transmitting fluid circulating in second circuit  17   b  called the cold circuit, which is circulated by second pump  24 , enters second compartment  13  at a given temperature T f1  and by means of traversing passageways  25  in rotating element  15 , crosses said portion of the element that is subjected to cooling. Said second heat-transmitting fluid undergoes cooling in this portion of rotating element  15  and leaves compartment  13  at a temperature T f2  that is lower than temperature T f1 . Additionally, the fluid in cold utility circuit  22  enters second heat exchanger  21  at temperature T fs1  and in turn undergoes cooling by means of heat exchange with the second heat-transmitting fluid which has traversed enclosure  11  and cooled down due to its passage through compartment  13 . This fluid leaves said second heat exchanger  21  at a temperature T fs2  that is lower than temperature T fs1  destined for some purpose. The cold stored in this fluid can be used in any cold application whatsoever, particularly for cooling a cold storage unit, an air conditioning circuit, or the like.  
         [0049]     The rotation of rotating element  15  alternately renews this operating cycle by generating heat in first heat exchanger  18  and cold in second heat exchanger  21 . To obtain continuous operation, rotating element  15  is driven at a rotation speed defined by the application as well as the amplitude of the magnetic field and the flow of heat-transmitting fluid traversing said rotating element  15 .  
         [0050]     First heat-transmitting fluid circulating in first circuit  17   a  and second heat-transmitting fluid circulating in second circuit  17   b  may be different or identical. Additionally, they may be either liquid, gas, or in some other state depending upon the application. Furthermore, the fluids circulating in heat and cold utility circuits  19  and  22  may be either gas or liquid, depending upon the application. For this reason heat exchangers  18  and  21  in device  10  may be any known type depending upon the state of the heat-transmitting fluid. They may be either liquid-liquid, liquid-gas, or gas-gas type heat exchangers. Instead of each of these exchangers  18  and  21 , any type of device that generates cold or heat, respectively, may be used, such, for example as a radiator, a heat pump, a refrigerator, or an air conditioning unit. It is also possible to circulate the fluid from heat utility circuit  19  through hot circuit  17   a  in place of the first heat-transmitting fluid to be heated directly in the hot portion of rotating element  15 , and to circulate the fluid from cold utility circuit  22  through cold circuit  17   b  in place of the second heat-transmitting fluid to be cooled directly in the cold portion of rotating element  15 . In this case the device does not comprise any heat exchangers.  
         [0051]      FIGS. 3A and 3B  are schematic representations of a variation of the device of  FIG. 1 . This device differs from device  10  of  FIG. 1  in that it comprises movable magnetic elements  16  which, when placed in a first position P 1 , that is, integral with compartment  13  ( FIG. 3A ) or in a second position P 2 , that is, integral with compartment  12  ( FIG. 3B ), allow the reversal of cold- and heat-generating circuits at will. The two positions P 1  and P 2  are symmetrical with each other relative to the plane of partition  14 . In this variation, magnetic elements  16  are equipped with attachment means  26 , such as a U-shaped axle, which can be made to pivot 180° or to move translationally by a control means known in the art and change from one position to the other. In this way a circuit generating cold when magnetic elements  16  are in position P 1  generates heat when these magnetic elements  16  are placed in position P 2 , and a circuit generating heat when magnetic elements  16  are in position P 1  generates cold when these magnetic elements  16  are placed in position P 2 .  
         [0052]     When magnetic elements  16  are placed in position P 1 , the portion of rotating element  15  subjected to a temperature increase due to the magnetic effect is situated in second compartment  13 . The first heat-transmitting fluid circulating in second circuit  17   b  becomes heated. Heat exchanger  21  then functions as a heat source and delivers heat to any fluid passing through it. At the same time, the portion of rotating element  15  that becomes demagnetized by cooling is situated in first compartment  12 . The first heat-transmitting fluid circulating in first circuit  17   a  cools. Heat exchanger  18  then functions as a cold-generating source and can deliver cold at its outlet.  
         [0053]     Conversely, when magnetic elements  16  are placed in position P 2 , for example, by pivoting 180°, the portion of rotating element  15  that becomes demagnetized by cooling is situated in second compartment  13 . The second heat-transmitting fluid circulating in second circuit  17   b  cools down. The heat exchanger then functions as a cold-generating source and delivers cold to any fluid passing through it. However, at the same time, the portion of rotating element  15  that is subjected to a temperature increase due to magnetic effect is situated in first compartment  12 . The first heat-transmitting fluid circulating in first circuit  17   a  heats up. Heat exchanger  18  then functions as a source of heat and can deliver heat at its outlet.  
         [0054]     When magnetic elements  16  are electromagnets, the same magnetic elements  16  attached for generating a magnetic field in first compartment  12  can also be attached in double and symmetrical relative to the plane separating the two compartments  12  and  13  in order to generate a magnetic field in second compartment  13 . These magnetic elements  16  can be separately activated by a single control that generates a magnetic field in one or the other of compartments  12  or  13  depending upon the position of the control. It is also possible to provide magnetic elements that generate a variable magnetic field in order to vary the temperatures of the heat-transmitting fluids passing through it.  
         [0055]      FIGS. 4 through 10  are schematic illustrations of variations of rotating element  15  of the device of the invention.  
         [0056]     In the form of embodiment shown in  FIG. 4 , rotating element  15  consists of several coaxially connected discs  30 . These discs are the same diameter and may be of the same thickness or different thicknesses. They are either attached at their surface or joined by any other suitable method. Each disc comprises a unit of traversing passageways  25  that communicate with the passageways in the adjacent disc or discs to open onto each surface of rotating element  15  thus formed. Each disc consists of a different magneto-calorific material. The number of discs depends on the number of magneto-calorific materials necessary to constitute rotating element  15 . These materials are defined according to the application of cold-generation and heat-generation device  10 . For a given application, the magneto-calorific materials are selected according to their Curie temperatures. These temperatures actually correspond to certain parameters required to attain the temperatures necessary for the application. Magneto-calorific materials with a Curie temperature ranging from 0° C. to −5° C., for example, are suitable for air conditioning applications; those with a Curie temperature ranging from 40° C. to 70° C., and preferably magneto-calorific materials with a Curie temperature of approximately 60° C., are suitable for heating applications; and magneto-calorific materials with a Curie temperature ranging from −10° C. to 70° C. are suitable for energy storage.  
         [0057]     In the form of embodiment shown in  FIG. 5 , rotating element  15  consists of several hollow cylindrical elements  40 , each made of a different magneto-calorific material and connected concentrically. These cylindrical elements are the same height and their interior and exterior diameters are defined so that each element overlaps the adjacent element. The exterior diameter of the largest hollow cylindrical element  40  constitutes the diameter of the resulting rotating element and the hole inside the smallest hollow cylindrical element corresponds to the bore passageway for axle  9  to which rotating element  15  is attached. Traversing passageways  25  are formed in the mass of each cylinder.  
         [0058]     Rotating element  15 , shown in  FIG. 6 , consists of several angular sectors  50  each made of a different magneto-calorific material. These elements, all with equal angles at the top, have the same radius and are the same height as rotating element  15 . Each sector  50  comprises traversing passageways  25  that may be obtained by using a fine grid structure. Thermally insulating elements  26  may be attached between the different sectors for improved insulation between the portion of rotating element  15  that undergoes cooling and the portion that undergoes a temperature increase. The reason for this is to increase the efficiency of the device of the invention by preventing the escape of the cold and heat it respectively generates.  
         [0059]     In the form of embodiment shown in  FIG. 7 , rotating element  15  consists of cavities  60  filled with grains  27  of a magnetic-calorific material. These cavities may take the form of angular sectors separated by thermally insulating elements  26 . Traversing passageways  25  are defined by the interstices formed between grains  27 . These interstices communicate with one another to open onto the two surfaces of rotating element  15 . These two surfaces are covered by a thin wall (not shown) of mesh with openings smaller than the smallest of grains  27 . This wall is not necessary if grains  27  are assembled with a connector. Grains  27  may be any shape and size. Their average size preferably ranges from 0.4 mm to 0.9 mm. They may be the same size and shape or different shapes and sizes. They may also consist of the same magneto-calorific material or different magneto-calorific materials. Each cavity may contain grains of the same magneto-calorific material, with the materials varying from one cavity to another, or a mixture of grains of different magneto-calorific materials, with the mixtures also varying from one cavity to another. It is very obvious that discs  30  and hollow elements  40  in the previously described embodiments could also consist of cavities filled with grains  27 .  
         [0060]     In the embodiment illustrated in  FIG. 8 , rotating element  15  is composed of a unit of coaxial tubular elements  70  that are spaced apart, with the spaces containing a pleated structure  71  that defines a multitude of traversing passageways. This structure may be made of a magneto-calorific material or it may serve as a support for such materials.  
         [0061]      FIG. 9  shows another form of embodiment wherein rotating element  15  comprises an interior annular element  15   a  and an exterior annular element  15   b  that are coaxial. The enclosure is defined by an interior channel  80   a  disposed between the two elements and by an exterior channel  80   b  formed on the periphery of element  15   b . The magnetic elements consist of a pair of interior magnets  81   a  cooperating with interior element  15   a  and a pair of exterior magnets  81   b  cooperating with exterior element  15   b . This arrangement improves penetration by the magnetic field and its action on the magneto-calorific materials, thereby increasing the effectiveness of the device.  
         [0062]     Another form of embodiment is shown in  FIG. 10 . The magnetic elements consist of angular segments, interior angular segments  90   a  and exterior angular segments  90   b , respectively. The magnetic field is not limited to a semicircular sector, but is localized in angular sectors all around the rotating element.  
         [0063]      FIG. 11  illustrates a variation in which the magnetic elements are housed in enclosure  11 , more specifically, inside first compartment  12 . They consist of at least one pair of magnets  100  equipped with orifices  101  for the passage of heat-transmitting fluid.  
         [0064]      FIG. 12  is a schematic representation of a complex arrangement consisting of a unit of devices of the invention connected in a cascade. In the example shown this arrangement comprises four devices  110 ,  120 ,  130  and  140 , each respectively comprising rotating elements  115 ,  125 ,  135  and  145  made of magneto-calorific material. The heat-transmitting fluid in the cold circuit  17   b  is moved to the cold inlet of rotating element  115  and then at the outlet of this element, it is broken down into two streams:  17   b   1 , which is moved to the cold inlet of the second rotating element  125 , and  17   b   2  which is moved to the hot inlet of the second rotating element  125 . The same steps occur with all the other rotating elements. However, the reverse circulation may be produced when the appropriate temperatures are attained. It is shown by the dotted arrows  125   e ,  135   e  and  145   e.    
         [0065]     Such an arrangement improves the efficiency of the device considerably and increases the thermal output of a cold-generation installation using the magnetic-calorific effect.