HK1180031B - Method for generating a thermal flow, and magnetocaloric thermal generator - Google Patents

Description

Method for generating a heat flow and magnetocaloric heat generator

Technical Field

The invention relates to a method for generating a heat flow from at least one thermal module comprising at least two magnetocaloric elements fluidically connected in pairs, crossed by a heat transfer fluid and subjected to a variable magnetic field that alternately generates in each magnetocaloric element a different magnetization phase corresponding to a heating phase and a cooling phase in succession, through which the heat transfer fluid flows simultaneously in synchronism with the magnetic field variations.

The invention also relates to a heat generator for implementing said method, said heat generator comprising: at least one thermal assembly comprising at least two associated magnetocaloric elements in fluid connection with each other, arranged to be crossed by a heat transfer fluid; a magnetizing device for subjecting each magnetocaloric element to a variable magnetic field which alternately generates in each magnetocaloric element two successive magnetization phases corresponding to a heating phase and a cooling phase, the heat transfer fluid flowing through said magnetocaloric elements being obtained by means of a circulation means synchronized with the variation of the magnetic field.

Background

Magnetic cooling techniques at ambient temperature have been known for more than twenty years and are known to have advantages in terms of ecology and sustainable development. It is also known to have limitations in its effective thermal power and its efficiency. Therefore, the research carried out in this field is totally intended to improve the performance of such generators by exploiting different parameters, such as the magnetizing power, the performance of the magnetocaloric elements, the heat exchange area between the heat transfer fluid and the magnetocaloric elements, the performance of the heat exchangers, etc.

The choice of magnetocaloric material determines and directly affects the performance of the magnetocaloric heat generator. In order to improve these properties, one solution consists in joining several magnetocaloric materials with different curie temperatures in order to increase the temperature gradient between the ends of the pack.

The known heat generators therefore comprise at least one thermal module M, such as that shown in fig. 1A and 1B, and comprise magnetocaloric materials, aligned in parallel, and means for circulating a heat transfer fluid, such as pistons P, for driving the heat transfer fluid in a reciprocating motion through the group of magnetocaloric materials MC, on both sides of the magnetocaloric materials MC, between a cold side F and a hot side C of the assembly (assembly) of magnetocaloric materials MC, in synchronism with a variation of the magnetic field (not shown). As shown in fig. 1A and 1B, these pistons P are arranged on both sides of the pack of magnetocaloric material MC, moving alternately first in one direction and then in the other direction, the pistons being shown in their two extreme positions in fig. 1A and 1B.

As shown in fig. 1A and 1B, the fluid moves either in one direction towards hot end C (the direction of movement of the heat transfer fluid is shown by the dotted arrows, see fig. 1A) when the magnetocaloric materials are subjected to a heating cycle, or in the other direction towards cold end F (the direction of movement of the heat transfer fluid is shown by the solid arrows, see fig. 1B) when the magnetocaloric materials are subjected to a cooling cycle.

This thermal module M has drawbacks because, in order to reach a temperature gradient, it is necessary to make the heat transfer fluid flow through all the materials. The use of a plurality of magnetocaloric elements MC increases the length of the material traversed by the heat transfer fluid. Therefore, in order not to reduce the number of cycles (one cycle being defined by the heating and cooling of the magnetocaloric elements), it is necessary to increase the speed of the heat transfer fluid. However, the increase in speed results in an increase in pressure, which increases the pressure losses and reduces the effectiveness of the heat exchange between the heat transfer fluid and the magnetocaloric elements, causing a reduction in the thermal efficiency of the magnetocaloric generator.

It is also known that, in order to increase the thermal power of a magnetocaloric generator, one possibility consists in increasing the number of cycles per second. However, as a result, the speed increases, which also leads to the aforementioned drawbacks.

Due to the variety of materials used, a generator comprising a thermal module M such as that shown in fig. 1A and 1B requires a non-negligible preparation time in order to achieve an available temperature gradient between the two ends.

The applicant has proposed, in the unpublished patent application FR08/05901, a magnetocaloric heat generator that can increase the thermal efficiency of the known generator with the same amount or length of material.

The applicant also proposed in patent applications WO2007/026062 and WO2008/012411 magnetocaloric heat generators with a block structure having two distinct hot and cold circuits in contact with the magnetocaloric material.

Object of the Invention

The present invention aims to remedy the aforementioned drawbacks of the prior art or, as a variant of the subject of patent application FR08/05901, to propose a method for generating a thermal flow which is easy to implement by a magnetocaloric heat generator, has an improved thermal efficiency, and also allows a large temperature gradient to be rapidly achieved between the hot and cold ends of said generator, in order to improve its effectiveness for the same quantity or length of magnetocaloric material.

To this end, the invention relates to a method of the type described in the preamble, characterized in that it further comprises:

connecting the magnetocaloric elements two by means of two different fluid circuits,

-subjecting the magnetocaloric elements alternately to oppositely changing magnetic fields so as to simultaneously generate opposite magnetization phases in each magnetocaloric element,

-simultaneously circulating a heat transfer fluid in said magnetocaloric elements in pairs in two opposite directions, so that, on the one hand, after the end of a magnetization heating phase, a quantity of heat transfer fluid flowing out of one of said magnetocaloric elements through one of said fluid circuits circulates in the next magnetocaloric element, which is then subjected to a magnetization heating phase, during the next magnetization phase; on the other hand, after the end of the magnetization cooling phase, a quantity of heat transfer fluid flowing out of one of the magnetocaloric elements through the other of the fluidic circuits circulates during the next magnetization phase in the next magnetocaloric element subjected to the magnetization cooling phase and vice versa, and

-between two opposite magnetization phases, the heat transfer fluid flowing out of one of said magnetocaloric elements is stored in an intermediate receiving region.

The invention also has for its object a heat generator, such as described in the previous section, characterized in that said magnetocaloric elements are fluidically connected in two places by two distinct fluid circuits, each comprising at least one compartment capable of receiving, during a magnetization phase, a defined quantity of heat transfer fluid flowing out of one of said magnetocaloric elements and of delivering, during the next magnetization phase, said defined quantity of heat transfer fluid to the next magnetocaloric element.

The method according to the invention consists in particular in causing the heat transfer fluid to flow simultaneously through each magnetocaloric element subjected to a cooling phase in the direction of a first end, called cold end, of the thermal assembly and through each magnetocaloric element subjected to a heating phase in the direction of a second end, called hot end, of the thermal assembly.

The method according to the invention also consists in fluidically connecting the magnetocaloric elements two by means of two distinct circuits, respectively: a cooling fluid circuit, called cold circuit, and a heating fluid circuit, called hot circuit, each comprising a compartment forming an intermediate receiving zone, said compartment being arranged between two adjacent magnetocaloric elements and being arranged to receive a heat transfer fluid flowing out of the magnetocaloric elements, said heat transfer fluid being reinjected into the next magnetocaloric element.

In order to increase the temperature range in which it is used (for example-25 ℃ to +65 ℃), the method of the invention may consist in arranging magnetocaloric elements in said thermal assembly, each having a different curie temperature, according to a curie temperature that increases progressively towards the magnetocaloric elements towards the hot end of the thermal assembly.

In this arrangement, the method also consists in implementing the magnetocaloric element from a plurality of magnetocaloric materials, the magnetocaloric materials being set with curie temperatures that increase progressively towards the hot end of the thermal module.

In the heat generator for carrying out the method of the invention, the circulation means may comprise, in each compartment, a piston for sucking and pumping the defined quantity of heat transfer fluid.

Furthermore, the magnetocaloric elements may be fluidically connected to each other by two different circuits in parallel, respectively: a cooling fluid circuit, called cold circuit, and a heating fluid circuit, called hot circuit, which are equipped with control means for controlling the direction of circulation of the heat-carrying fluid, so that the circulation of the heat-carrying fluid in the circuits takes place in opposite directions.

Drawings

The invention and its advantages will be better understood in the following description of an embodiment given as a non-limiting example with reference to the accompanying drawings, in which:

FIGS. 1A and 1B are schematic diagrams of a thermal assembly of the prior art;

fig. 2A to 2C are schematic views of a thermal assembly made up of four magnetocaloric elements, respectively in three successive phases of the method according to the invention, showing the flow of a heat transfer fluid through said four magnetocaloric elements;

FIG. 3 is a perspective view of one embodiment of a thermal assembly of the present invention;

FIG. 4 is a front view of a portion of the thermal assembly shown in FIG. 3;

FIGS. 5A and 5B are cross-sectional views of the thermal assembly of FIG. 3 taken along planes C-C and D-D, respectively, of FIG. 4, showing the thermal assembly in a first magnetization phase;

FIG. 6 is a front view of a portion of the same thermal assembly shown in FIG. 3 as FIG. 4; and

figures 7A and 7B are cross-sectional views of the thermal assembly of figure 3 taken along planes a-a and B-B of figure 6, respectively, showing the thermal assembly in a second magnetization phase.

Detailed Description

In the illustrated embodiment, like components or parts have like reference numerals.

The thermal module 1 shown in fig. 2 to 7 comprises four magnetocaloric elements 21, 22, 23, 24 defining a cold end 3 on the left side of the figure and a hot end 4 on the right side of the figure, these elements being connected to each other two by two, i.e. between adjacent magnetocaloric elements 21 and 22, 22 and 23, and 23 and 24. These magnetocaloric elements 21, 22, 23, 24 are connected to each other by two different fluid circuits 8 and 9, one cold circuit 8 and one hot circuit 9 at a time. The magnetocaloric elements 21, 22, 23, 24 are connected in series in two different fluid circuits 8 and 9 connected in parallel. Each fluid circuit 8, 9 comprises a piston 61, 62, 63; 71. 72, 73 forming heat transfer fluid circulation means, the chamber of each piston forming a compartment 81, 82, 83 or 91, 92, 93 in fluid connection with the respective magnetocaloric element 21, 22, 23, 24. The compartments 81, 82, 83, 91, 92, 93 form an intermediate receiving zone for the heat transfer fluid, which is pumped and forced between the two magnetization phases. Furthermore, circuits 8, 9 also comprise control means (see fig. 5A and 5B), for example check valves, which control the direction of circulation of the heat transfer fluid. These means for controlling the heat transfer fluid are intended to force the circulation direction of the heat transfer fluid in circuits 8, 9, for example from right to left, i.e. from hot end 4 to cold end 3, for circuit 8 and from left to right, i.e. from cold end 3 to hot end 4, for circuit 9, with reference to the figures.

The magnetocaloric elements 21, 22, 23 and 24 have curie temperatures that increase progressively from the cold end 3 towards the hot end 4, the magnetocaloric element 24 with the highest curie temperature being arranged at the hot end 4 of the thermal module 1. In a variant, each magnetocaloric element 2 can be implemented by assembling a plurality of magnetocaloric materials also arranged according to their increasing curie temperature. These magnetocaloric elements comprise communicating fluid channels (not shown) which can be constituted by micro-holes of porous material, micro-channels machined on a solid body, or obtained by assembly, for example, of superimposed slotted plates.

The cold 3 and hot 4 ends of the thermal module 1 coincide with the cold and hot ends of the two magnetocaloric elements 21 and 24 arranged at the ends of said thermal module 1. It is, of course, also connected to one or more heat transfer fluid circulation means, such as a piston, or any other equivalent means not shown on figures 2A to 2C. It may also be connected to a heat exchanger or any equivalent component that allows heat and/or negative large cards to be dissipated to one or more external application devices.

The thermal module 1 shown in fig. 3, 5A, 5B, 7A and 7B comprises a linear structure in which four magnetocaloric elements 21, 22, 23 and 24 are arranged in a row. Of course, any other suitable form may be used.

Fig. 3, 5A, 5B, 7A and 7B do not show the magnetization means 5 that can subject the magnetocaloric elements 21 to 24 to a variable magnetic field. However, the magnetizing means 5 is schematically shown in fig. 2A to 2C. It can be constituted by a permanent magnet that moves relatively with respect to the magnetocaloric elements 21 to 24 or by any other similar component.

Each magnetocaloric element 21, 22, 23, 24 can be formed by a piston 61, 62, 63; 71. 72, 73 and subjected to a varying magnetic field by the magnetizing means 5 which generate alternating heating and cooling phases, a magnetization cycle consisting of two magnetization phases coinciding with a cooling phase and a heating phase of the respective magnetocaloric element 21, 22, 23, 24. Pistons 61, 62, 63; 71. 72, 73 are synchronized with the magnetic field variations so that the heat transfer fluid flows in the direction of hot end 4 through each magnetocaloric element 21 and 23 or 22 and 24 subjected to a heating cycle and in the direction of cold end 3 through each magnetocaloric element 22 and 24 or 21 and 23 subjected to a cooling cycle. This movement is possible thanks to the two different fluid circuits 8 and 9, each connecting the magnetocaloric elements 21, 22, 23, 24 in series. In fact, the first fluid circuit 8, called cold circuit, is dedicated to the passage of the heat transfer fluid from right to left through the magnetocaloric elements 21, 22, 23, 24 as shown only when they are subjected to a cooling cycle, and the second fluid circuit 9, called hot circuit, is dedicated to the passage of the heat transfer fluid from left to right through the magnetocaloric elements 21, 22, 23, 24 as shown only when they are subjected to a heating cycle. For chambers 81, 82, 83; 91. 92, 93, wherein the first portion 81, 82, 83 corresponds to the first fluid circuit 8 and receives the heat transfer fluid cooled by passing through the magnetocaloric elements 21, 22, 23, 24 only when they are subjected to a cooling cycle, and the second portion 91, 92, 93 corresponds to the second fluid circuit 9 and receives the heat transfer fluid reheated by passing through the magnetocaloric elements 21, 22, 23, 24 only when they are subjected to a heating cycle.

As already described, control means of the heat transfer fluid are integrated in each circuit 8, 9 to force the circulation direction of the heat transfer fluid. In other words, between the two magnetocaloric elements, one circuit 8, called the hot circuit, is used to circulate the heat transfer fluid in one direction, and the other circuit 9, called the cold circuit, is used to circulate the heat transfer fluid in the opposite direction. The direction of circulation in said circuits 8, 9 is not changed, each of said circuits being intended to allow the circulation of the heat transfer fluid in a single direction, i.e. from one magnetocaloric element to the magnetocaloric element connected thereto by said circuits 8, 9. Therefore, if it is considered that the thermal circuit 9 and the cold circuit 8 connect the magnetocaloric elements 21 and 22, the thermal circuit 9 is configured to transfer the heat transfer fluid flowing out of the magnetocaloric element 21 after the end of the heating phase to the magnetocaloric element 22 by temporarily storing it in or passing through one of the receiving areas 91, and the cold circuit 8 is configured to transfer the heat transfer fluid flowing out of the magnetocaloric element 22 after the end of the cooling phase to the magnetocaloric element 21 by temporarily storing it in or passing through one of the receiving areas 81. Hot circuit 9 circulates the heat transfer fluid towards hot end 4, and cold circuit 8 circulates the heat transfer fluid towards cold end 3. The intermediate receiving areas 81, 91 can store the heat transfer fluid between the two magnetization phases.

Fig. 2A to 2C show the thermal assembly 1 in three successive magnetization phases of the method. Fig. 2A, 2C, 5A and 5B show a thermal module 1 in which the magnetocaloric elements 21, 22, 23, 24 are in the same magnetization state, namely: the first and third magnetocaloric elements 21 and 23, starting from the left on these figures, are subjected to a magnetic field generated by the magnetizing means 5 or to an increasing magnetic field and are in the heating phase, the other two magnetocaloric elements 22 and 24 of the thermal module 1 are subjected to a zero magnetic field or to a decreasing magnetic field and are in the cooling phase.

In the case of an inverse effect magnetocaloric material, it is subjected to a magnetic field or a gradually increasing magnetic field, causing it to cool and escape from the magnetic field, or it is subjected to a weak magnetic field or a gradually decreasing magnetic field, causing it to heat. Thus, the method of the invention remains the same, except that the phase of the cycle is reversed with respect to the magnetic field change.

Fig. 2B, 7A and 7B show a thermal assembly 1 in which the first and third magnetocaloric elements 21 and 23 are in the cooling phase, since they are no longer subjected to the magnetic field, and the other two magnetocaloric elements 22 and 24 are subjected to the magnetic field generated by the magnetizing means 5 and are in the heating phase. The heat transfer fluid is circulated by pistons 61, 62, 63; 71. 72, 73.

Fig. 2A, 5A and 5B show a first magnetization phase in which the pistons 61, 71 and 63, 73, respectively between the first magnetocaloric element 21 in operation (subjected to a magnetic field or to a gradually increasing magnetic field) and the second magnetocaloric element 22 not in operation (not subjected to a magnetic field or to a gradually decreasing magnetic field) and between the third magnetocaloric element 23 in operation and the fourth magnetocaloric element 24 not in operation, move downwards in a suction manner so that their chambers or compartments 81, 91 and 83, 93 suck the heat transfer fluid, and the other two pistons 62 and 72 move upwards in a pressure-feed manner so that their chambers or compartments 82, 92 expel the heat transfer fluid contained therein.

Fig. 2B, 7A and 7B show a second magnetization phase, in which the pistons 61, 71 and 63, 73 respectively between the now inactive first magnetocaloric element 21 and the active second magnetocaloric element 22 and between the inactive third magnetocaloric element 23 and the active fourth magnetocaloric element 24 are moved upwards in a pumping manner so that their chambers or compartments 81, 91 and 83, 93 are evacuated of the heat transfer fluid contained therein, and the other two pistons 62 and 72 are moved downwards in a suction manner so that their chambers or compartments 82, 92 are evacuated of the heat transfer fluid.

Fig. 2C shows a third magnetization phase, which corresponds to the first magnetization phase shown in fig. 2A.

With reference to fig. 2A, 2B, 2C, 5A, 5B, 7A and 7B, it can be noted that the heat transfer fluid flowing through the first magnetocaloric element 21 subjected to heating and directed towards the chamber 91 during the first magnetization phase shown in fig. 2A, flows through the second magnetocaloric element 22 also subjected to heating and directed towards the chamber 92 during the second magnetization phase shown in fig. 2B, and then flows through the third magnetocaloric element 23 subjected to heating and directed towards the chamber 93 during the third magnetization phase shown in fig. 2C. Similarly, the heat transfer fluid which flows through the fourth magnetocaloric element 24 subjected to cooling and is directed towards the chamber 83 during the first magnetization phase shown in fig. 2A, flows through the third magnetocaloric element 23 also subjected to cooling and is directed towards the chamber 82 during the second magnetization phase shown in fig. 2B, and then flows through the second magnetocaloric element 22 subjected to cooling and is directed towards the chamber 81 during the third magnetization phase shown in fig. 2C.

The heat transfer fluid flowing from cold end 3 to hot end 4 from left to right as shown in the figure is therefore heated as it approaches said hot end 4, since it passes through the magnetocaloric elements, being heated successively by each of said magnetocaloric elements 21 to 24, by reheating of each of said magnetocaloric elements. At the same time, the heat transfer fluid flowing from hot end 4 to cold end 3 from right to left as shown cools as it approaches said cold end 3, as it passes through the magnetocaloric elements, being cooled successively by each of said magnetocaloric elements 24 to 21 by the cooling of said magnetocaloric elements. Furthermore, the cold fluid circuit 8 and the hot fluid circuit 9 are separated so that the quantity of heat transfer fluid that flows through the magnetocaloric elements when it heats up never mixes with the quantity of heat transfer fluid that flows through the same magnetocaloric elements 21 to 24 when it cools down. In particular, this configuration of the magnetocaloric elements 21 to 24 arranged according to their increasing curie temperature and this method make it possible to increase the temperature gradient between the hot and cold ends of the thermal module 1 and to reach it quickly. In other words, the present invention allows to obtain rapidly large temperature gradients and consequently a large effective thermal power taken from such a thermal assembly 1.

The method of the invention allows to generate a temperature gradient between the hot end 4 and the cold end 3 of the thermal module 1 and to maintain this temperature gradient while extracting or exchanging thermal energy with the application system or with an external circuit. The heat generator of the invention is in fact intended to exchange thermal energy with one or more external use circuits (heating, air conditioning, thermoregulation, etc.), optionally connected by a heat exchanger at least at one of the cold end 3 or hot end 4 of each thermal module 1. The hot or cold chambers may also be associated with or fluidly connected to the hot or cold ends 4, 3 of the thermal module 1.

Furthermore, the stepwise driving of the heat transfer fluid, i.e. the driving of the heat transfer fluid by means of the circulation means between two adjacent magnetocaloric elements, has numerous advantages with respect to the known generators in which the fluid flows simultaneously through all the magnetocaloric elements MC from the first to the last magnetocaloric element in a first direction and then through the same magnetocaloric elements MC in a direction opposite to the first direction (see fig. 1A and 1B).

A first advantage is that the pressure loss is dispersed and reduced, as measured by the pistons 61, 62, 63; 71. 72, 73, the heat transfer fluid, during each magnetization phase, passes through only one magnetocaloric element 2, and not through all the magnetocaloric elements 2 that make up the thermal module 1.

To this end, with reference to fig. 2A to 2C, the arrows show the direction of movement of the heat transfer fluid, the dashed arrows corresponding to the movement towards the hot end 4, and the solid arrows showing the movement towards the cold end 3.

A second advantage is obtained with the system according to the invention with magnetocaloric materials of the same length compared to the systems known from the prior art shown in fig. 1A and 1B. It can be seen that for the same speed of the heat transfer fluid through the magnetocaloric elements MC, the frequency of the cycles is multiplied by four in the generator of the invention comprising the thermal module 1. The thermal power of such a heat generator is therefore also increased in the same proportion.

As an illustrative example, for each magnetocaloric element with a heat transfer fluid speed of 100mm/s and a length of 100 mm:

the time required to pass through all the magnetocaloric elements MC of the systems known in the prior art shown in fig. 1A and 1B is (4 × 100) ÷ 100 ═ 4 seconds, which corresponds to a frequency of 0.25 hertz,

the time required to pass through all the magnetocaloric elements 21 to 24 of the heat generator 1 of the invention is (1 × 100) ÷ 100 ═ 1 second, which corresponds to a frequency of 1 hertz, i.e. three times faster.

Also, with the system known in the prior art in comparison with the thermal module 1 of the invention, it can be seen that for the same frequency of the cycles (demagnetization and magnetization), the speed of movement of the heat transfer fluid is divided by four in the heat generator of the invention. The effect of the invention is to reduce the pressure loss, which corresponds to a reduction in the energy required to move the heat transfer fluid, increasing the heat exchange time and thus the heat exchange power.

As an illustrative example, for each magnetocaloric element with a frequency of 0.5 hz corresponding to a heating (or magnetization) phase of one second and a cooling (or demagnetization) phase of one second and a length of 100 mm:

in order to pass through all the magnetocaloric elements MC of the systems known in the prior art shown in fig. 1A and 1B during one second, the speed of the heat transfer fluid must be (4 x 0.100) ÷ 1 ═ 0.4m/s,

and the speed of the heat transfer fluid driven at each common chamber is (1 × 0.100) ÷ 1 ═ 0.1m/s in order to pass through all the magnetocaloric elements 21, 22, 23, 24 of the heat generator 1 of the invention.

The figures do not show the pistons 81, 82, 83; 71. 72, 73, respectively. These operating members may be implemented by means of corresponding control cams or any equivalent member mounted on a rotating shaft, for example, rotating itself.

In this arrangement, it is also possible to arrange a plurality of thermal modules 1 in a star shape, for example angularly offset from each other by 90 °, forming a control cam comprising respective blades (lobes) also angularly offset from each other by 90 °, so that said thermal modules are arranged radially around an axis, each blade operating a piston of each thermal module of said thermal modules 1.

In a second embodiment, not shown, the pistons 81, 82, 83; 71. the manipulation of 72, 73 can be carried out by a manipulation carriage which moves along the thermal module 1 according to a reciprocating translational movement and comprises guide slots in which the respective connections of each piston are guided. The guide groove may have a saw-tooth shape, and the piston may be arranged substantially opposite the steering carriage.

Advantageously, the method consists in causing the heat transfer fluid to flow through all the magnetocaloric elements 21 to 24 so as to rapidly establish a large temperature gradient between the two ends, cold 3 and hot 4, of the magnetocaloric element 1. In this method, a first portion of the heat transfer fluid circulates in the direction of cold end 3 and passes through the magnetocaloric elements 24 to 21 only when they are in the cooling phase, and a second portion of the heat transfer fluid circulates in the direction of hot end 4 and passes through the magnetocaloric elements 21 to 24 only when they are in the heating phase. Thus, the fluid circulating in cold circuit 8 cools as it approaches cold end 3, passes through magnetocaloric elements 24 to 21 arranged according to their progressively lower curie temperatures, exchanging heat with them, while the fluid circulating in hot circuit 9 heats as it approaches hot end 4, passes through magnetocaloric elements 21 to 24 arranged according to their progressively higher curie temperatures, exchanging heat with them.

Of course, the invention is not limited to the embodiments described, but can be adapted to operate the pistons 81, 82, 83; 71. 72, 73, respectively.

The generator of the invention may comprise one or more thermal modules 1. The number and spatial arrangement of these thermal assemblies depends on the available space and the required thermal power.

Possibility of industrial application

The present description clearly shows that the invention achieves the intended aim, namely to propose a heat generator comprising one or more thermal modules 1, of simple structure and improved efficiency.

Such heat generators may find industrial and domestic application in heating, air conditioning, temperature regulation, refrigeration or other fields at competitive costs and with reduced space requirements.

In addition, all the components constituting the heat generator can be implemented according to reproducible industrial processes.

The invention is not limited to the described embodiments but comprises any modifications and variants that are obvious to a person skilled in the art, while remaining within the scope of protection defined in the appended claims.

Claims (8)

1. Method of generating a thermal flow from at least one thermal assembly (1) comprising at least one pair of magnetocaloric elements (21, 22, 23, 24) crossed by a heat transfer fluid and subjected to a variable magnetic field that alternately generates in each of said magnetocaloric elements (21, 22, 23, 24) a different magnetization phase corresponding to a heating phase and a cooling phase in succession, said heat transfer fluid flowing simultaneously through said magnetocaloric elements (21, 22, 23, 24) in synchronism with the variation of the magnetic field, and said magnetocaloric elements (21, 22, 23, 24) being subjected alternately to a magnetic field of opposite phase so as to simultaneously generate in each of said magnetocaloric elements an opposite magnetization phase,

said method is characterized in that it further comprises:

-connecting the magnetocaloric elements (21, 22, 23, 24) two by means of two different fluid circuits (8, 9) so that the magnetocaloric elements (21, 22, 23, 24) are connected in series in the fluid circuits (8, 9), which are themselves connected in parallel,

-circulating said heat transfer fluid simultaneously in pairs in two opposite directions in said magnetocaloric elements (21, 22, 23, 24), so that, on the one hand, after the end of a magnetization heating phase, a quantity of heat transfer fluid flowing through one of said fluid circuits (9) and exiting from one of said magnetocaloric elements (21, 23; 22) circulates during the next magnetization phase in the next magnetocaloric element (22, 24; 23) which is then subjected to a magnetization heating phase; on the other hand, after the end of the magnetization cooling phase, an amount of heat transfer fluid flowing out of one of the magnetocaloric elements (22, 24; 23) through the other one of the fluid circuits (8) flows during the next magnetization phase in the next magnetocaloric element (21, 23; 22) subjected to the magnetization cooling phase and vice versa, and

-between two opposite magnetization phases, storing the heat transfer fluid between said magnetocaloric elements (21, 22, 23, 24) connected two by two in at least two intermediate receiving areas (81, 82, 83, 91, 92, 93) arranged in different and parallel fluid circuits (8, 9).

2. A method according to claim 1, characterized in that it consists in causing said heat transfer fluid to flow simultaneously through each magnetocaloric element (21, 22, 23, 24) undergoing a cooling phase in the direction of a first end of the thermal assembly, called cold end (3), and through each magnetocaloric element (21, 22, 23, 24) undergoing a heating phase in the direction of a second end of the thermal assembly, called hot end (4).

3. A method according to any one of the preceding claims, characterised in that the magnetocaloric elements are fluidically connected two by means of two different fluidic circuits (8, 9) respectively: a cooling fluid circuit, called cold circuit (8), and a heating fluid circuit, called hot circuit (9), said two fluid circuits (8, 9) each comprising a compartment (81, 82, 83; 91, 92, 93) forming an intermediate receiving zone, said compartments being arranged between two adjacent magnetocaloric elements and being arranged to receive a heat transfer fluid flowing out of the magnetocaloric elements (21, 22, 23, 24) and to be reinjected into the next magnetocaloric element (22; 21, 23; 22, 24; 23).

4. A method according to claim 1, characterized in that it consists in arranging magnetocaloric elements (21, 22, 23, 24) in said thermal module (1), each having a different curie temperature, according to their curie temperature increasing progressively towards the hot end (4) of said thermal module (1).

5. A method according to claim 4, characterized in that it consists in implementing said magnetocaloric elements (21, 22, 23, 24) with a plurality of magnetocaloric materials arranged with Curie temperatures that increase progressively towards the hot end (4) of said thermal module (1).

6. Heat generator for implementing the method according to any one of the preceding claims, comprising: at least one thermal assembly (1) comprising at least one pair of magnetocaloric elements (21, 22, 23, 24) arranged to be crossed by a heat transfer fluid; a magnetization device (5) for subjecting each of said magnetocaloric elements (21, 22, 23, 24) to a variable magnetic field that alternately generates two successive magnetization phases in each of said magnetocaloric elements (21, 22, 23, 24), said two successive magnetization phases corresponding to a heating phase and a cooling phase, said heat transfer fluid flowing through said magnetocaloric elements (21, 22, 23, 24) being realized by means of circulation means (61, 62, 63; 71, 72, 73) synchronized with the magnetic field variations,

the heat generator is characterized in that the magnetocaloric elements (21, 22, 23, 24) are fluidically connected two by means of two different fluid circuits (8, 9) which are themselves connected in parallel and each of which comprises at least one compartment (81, 82, 83; 91, 92, 93) capable of receiving a defined quantity of heat transfer fluid flowing out of one of the magnetocaloric elements (21, 22, 23, 24) during a magnetization phase and of conveying said defined quantity of heat transfer fluid to the next magnetocaloric element (22; 21, 23; 22, 24; 23) during the next magnetization phase.

7. Heat generator according to claim 6, characterised in that said circulating means (61, 62, 63; 71, 72, 73) comprise in each compartment (81, 82, 83; 91, 92, 93) a piston arranged for sucking and pumping said limited quantity of heat transfer fluid.

8. Heat generator according to either of claims 6 and 7, characterized in that the magnetocaloric elements (21, 22, 23, 24) are fluidically connected to each other by two different fluid circuits (8, 9) in parallel, respectively: a cooling fluid circuit, called cold circuit (8), and a heating fluid circuit, called hot circuit (9), which are equipped with control means for controlling the direction of circulation of the heat transfer fluid, so that the circulation of the heat transfer fluid in the two fluid circuits (8, 9) takes place in opposite directions.