EP3039373B1 - Heat exchanger for exchanging heat between two fluids, use of the exchanger with liquid metal and gas, application to a fast neutron nuclear reactor cooled with liquid metal - Google Patents

Description

Technical area

The present invention relates to heat exchangers between two fluids.

The invention relates more particularly to the realization of a new type of compact heat exchanger and high thermal power.

The invention thus relates to a heat exchanger integrating one or more plate type heat exchanger modules in a pressure shell.

The main use of the exchanger between two fluids according to the invention is its use with liquid metal and gas. It may be advantageously liquid sodium and nitrogen.

The main application targeted by the exchanger according to the invention is the exchange of heat between a liquid metal, such as liquid sodium, of the secondary loop and nitrogen as gas in the tertiary loop of a reactor with fast neutrons cooled with the liquid metal, such as the liquid sodium called RNR-Na or SFR (acronym for " Sodium Fast Reactor ") and which is part of the family of so-called fourth generation reactors.

Although described in connection with this main application, a heat exchanger according to the invention can also be implemented in any other application requiring exchange between two fluids, such as a liquid and a gas, preferably when it is necessary to have a compact exchanger and high thermal power.

In the context of the invention, the term "primary fluid" means the usual thermal meaning, namely the hot fluid which transfers its heat to the secondary fluid which is the cold fluid,

In contrast, by "secondary fluid" is meant in the context of the invention, the usual thermal sense, namely the cold fluid to which is transferred the heat of the primary fluid.

In the main application, the primary fluid is the sodium that circulates in the so-called secondary loop of the thermal conversion cycle of a reactor RNR-Na, while the secondary fluid is the nitrogen that circulates in the tertiary loop of said cycle.

State of the art

The heat exchangers, known as plate heat exchangers, have significant advantages over heat exchangers, known as tube heat exchangers, in particular their thermal performance and their compactness thanks to a ratio of the surface area to the heat exchange volume favorably. high. Compact plate heat exchangers are used in many industrial fields.

The known tube exchangers are, for example, tube and shell exchangers, in which a bundle of upright or bent U-shaped or helical tubes is fixed on pierced plates and disposed inside a chamber waterproof called calender. In these tube and shell exchangers, one of the fluids circulates inside the tubes while the other fluid circulates inside the shell. These tube and shell exchangers have a large volume and are therefore of low compactness.

It has already been described in the literature the production of heat exchangers comprising compact plate heat exchanger modules arranged in a pressurized shell.

We can mention here the patent FR 2733823 which discloses the pressurized calender consisting of a sealed enclosure, a corrugated plate bundle which allows the operation of said plates at higher pressures than their intrinsic mechanical strength could allow. The implementation of such an exchanger is very dependent on the manufacturing technology of the corrugated plate bundle and it is limited to a single bundle of plates, which has the disadvantage of limiting the unit heat power of the exchanger.

Compact plate heat exchangers are not currently implemented in the nuclear field and no nuclear dimensioning code integrates them.

However, AREVA has proposed, in the context of studies on high- or high-temperature gas reactors, called HTR or VHTR (for " High Temperature Reactor " or " Very High Temperature Reactor "), a design solution. in a calender of a series of plate heat exchanger modules by pooling a portion of the fluid supply and distribution manifolds. This solution, for example described in the patent FR 2887618 , is advantageous insofar as the unit heat power of the exchanger can be increased by increasing the number of heat exchanger modules in series. On the other hand, the radial orientation of the exchanger modules and the relative arrangement of the collectors with respect to the sealed enclosure forming the calender, on the one hand, limit the use of the exchanger to an exchange between gas and gas because, the emptying of a liquid is not possible and, on the other hand do not allow to have a really compact exchanger. Thus, the volume occupied by the structures (sealed enclosure, support, etc.) and the collectors is much greater than the intrinsic volume of the exchanger modules.

In addition to the problems of exchanger compactness and high unit thermal power, the inventors of the present invention were faced with the need to find a heat exchanger between a liquid metal, such as liquid sodium, and a gas, with the need to be able to perform a gravity drain of the liquid metal circuit and thus an elimination of the retention zones in this circuit.

In the context of his studies for a fast neutron nuclear reactor prototype cooled with liquid sodium, the inventors have already proposed a heat exchanger design solution between liquid sodium and a gas which uses exchanger modules. compact plates. This solution is for example described in the publication [1].

We reproduced Figures 1 to 1C , the views of the heat exchanger as disclosed in this publication [1].

The heat exchanger 1 is intended to transfer heat between a first fluid, which is nitrogen (N ₂ ) (cold fluid) and a second fluid which is liquid sodium (Na).

It has also been indicated on these Figures 1 to 1C , the characteristic temperatures and pressures respectively of nitrogen and of sodium as they are provided at their inlet and at their outlet from exchanger 1. In particular, the pressure of 180 bar (18 MPa) is that of the nitrogen and therefore, that prevailing inside the sealed enclosure 2.

The heat exchanger 1 of central axis X comprises a sealed enclosure 2 in which is housed a plurality of 3 exchanger modules 3.1, 3.2, 3.3, 3.4, arranged vertically and parallel to the axis X. As better illustrated in Figure 1A the number of identical exchanger modules is equal to four.

The sealed enclosure 2 is of substantially cylindrical general shape and consists essentially of a cover 20 assembled with a bottom 21. The cover 20 has no opening.

Thus, the sealed enclosure 2 comprises at one of its longitudinal ends, both an inlet 10 and an outlet 11 of the nitrogen and an inlet 12 and an outlet 13 of the liquid sodium.

Each exchanger module 3.1, 3.2, 3.3, 3.4 integrates two fluid circuits including one dedicated to the circulation of sodium (Na) coming from a nuclear reactor RNR-Na, as the primary fluid of the exchanger module, and the other dedicated to the circulation of nitrogen (N2) as a secondary fluid.

The plurality of exchanger modules 3.1, 3.2, 3.3, 3.4 is supported by a support structure 4.

As explained below, the support structure 4 is flexibly fixed in the sealed enclosure 2. For this purpose, the exchanger modules 3.1, 3.2, 3.3, 3.4 are placed on a perforated support plate 40 which is suspended in the enclosure 2 by means of flexible arms 40a, 40b, 40c ( figure 1C ).

A nitrogen inlet chamber 5 is formed axially on top of the enclosure 2, at its upper longitudinal end 2b, between the exchanger modules 3.1 to 3.4 and the cover 20 of the enclosure 2.

As illustrated in figure 1 using the curved arrows, this chamber 5 communicates with each unrepresented input of the integrated nitrogen circuit in one of the exchanger modules 3. 1 to 3.4.

Opposite the chamber 5, a first central collector 6 is arranged axially around the central axis (X). This first central collector 6 has the function of recovering the hot nitrogen to which the heat of the sodium has been transferred in the exchanger modules 3.1 to 3.4.

This central collector 6 therefore communicates upstream with each unrepresented output of the integrated nitrogen circuit in one of the exchanger modules 3.1 to 3.4. Downstream, this central collector 6 communicates with the outlet 11 of the nitrogen of the enclosure 2.

An annular collector 7 is arranged around the central collector 6 and exchanger modules 3.1 to 3.4 forming a nitrogen guide space. This annular collector 7 serves to bring the cold nitrogen into the chamber 5.

More precisely, this annular manifold 7 consists essentially of a flared deflector 70 and a cylindrical shell 71. Thus, the nitrogen guiding space is delimited from upstream to downstream, at the outside by the chamber 2 and inside, by the first central collector 6 and then by the deflector 70 and the ferrule 71. The annular collector 7 is arranged coaxially around the first central collector 6.

The annular collector 7 thus communicates upstream with the inlet 10 of the nitrogen of the enclosure 2 and downstream with the chamber 5.

A plurality 8 of inlet pipes 81, 82, 83, 84 is arranged to bring the hot sodium into each of the unrepresented inputs of the sodium circuit integrated in one of the exchanger modules 3.1 to 3.4.

Thus, each inlet pipe 81 to 84 communicates upstream with the inlet 12 of the sodium of the enclosure 2, and downstream with each inlet 31 to 34 of the sodium circuit integrated in one of the exchanger modules 3.1 to 3.4 .

As best illustrated in Figure 1A , each inlet 31 to 34 is formed on a lateral side of the bottom of a module 3.1 to 3.4: the plurality 8 of inlet pipes 81 to 84 is curved so as to be able to lead to these lateral inlets 31 to 34.

A plurality 9 of outlet pipes 91, 92, 93, 94 is arranged to extract the cold sodium from each of the outputs of the sodium circuit integrated in one of the exchanger modules 3.1 to 3.4.

Thus, each outlet pipe 91 to 94 communicates upstream with an output of the sodium circuit integrated in one of the exchanger modules 3.1 to 3.4 and downstream with the outlet 13 of the sodium of the enclosure 2. The outlet 13 of the sodium cold takes place laterally and upwards of the enclosure 2.

As best illustrated in Figure 1A each sodium outlet is made on a lateral side of the top of a module 3.1 to 3.4: the plurality of 9 output pipes 91 to 94 is curved to be able to lead to these lateral outlets.

Also, as best illustrated in Figure 1A , the plurality 8 of inlet pipes 81 to 84 communicate with a second central collector 14 which thus brings the hot liquid sodium through the inlet 12 of the enclosure 2. The first central collector 6 is coaxial with the second central collector 14 and disposed between the annular collector 7 and the second central collector 14.

The operation of the heat exchanger 1 which has just been described will now be briefly explained in relation to the path of nitrogen and sodium.

The cold nitrogen arrives, at a temperature of the order of 330 ° C. and at a pressure of the order of 180 bar (18 MPa), through the inlet 10 and is then fed through the annular manifold 7 at the top of the enclosure 2 and is redirected to the inlet chamber 5 by the cover 20, as illustrated by the rising and descending lateral arrows in figure 1 .

The nitrogen then flows through the heat exchanger modules 3.1 to 3.4 in which heat from the hot sodium is transferred thereto.

The nitrogen, which has become hot at a temperature of the order of 515 ° C., emerges from the modules 3.1 to 3.4 and is extracted from the enclosure through the outlet 11 via the first central collector 6.

The hot sodium is brought, at a temperature of the order of 530 ° C, by the second central collector 14 through the inlet 12 and is distributed in each exchanger module 3.1 to 3.4 by the pipes 81 to 84.

The hot sodium then passes through the heat exchanger modules 3.1 to 3.4 in which it transfers its heat to the nitrogen.

Sodium, which has become cold at a temperature of the order of 345 ° C., emerges from modules 3.1 to 3.4 and is then withdrawn from enclosure 2 through outlet 13 through outlet pipes 91 to 94.

The heat exchanger 1 which has just been described has the advantages of being able to be of high unit thermal power and of being compact. In addition, the arrangement of the exchanger modules 3.1 to 3.4, the plurality of inlet and outlet pipes 9 and the second central manifold 14 allows gravity drainage of sodium but only hot sodium. Indeed, with regard to cold sodium, given the curved shape of the outlet pipes, it is very likely that there is a retention of cold sodium.

However, this heat exchanger has the major drawback that the distribution of fluids can be difficult to guarantee industrially given the temperature levels required for operation. Thus, in essence, it is first necessary to ensure the perfect sliding seal between the supply manifold 14 of the sodium and the output manifold 6 of the nitrogen which is coaxial, with the aid of a bellows 15. On the other hand, the hot nitrogen coming out of the modules Exchanger 3.1 to 3.4 is recovered by the deflector 70, as shown by the downward curved arrows, which therefore thermally urges the suspended support structure 4, 40 of the exchanger modules 3.1 to 3.4. The support part itself 40 must also seal between the hot nitrogen present in the chamber 5 and the cold nitrogen recovered downstream. Thus, it is necessary to ensure both the good mechanical and thermal strength of the flexibility of the arms 40a to 40c and good flexibility in the inlet pipes 81 to 84 of the sodium passing through the support 40 by means of metal bellows 16 .

The patent FR 2 898 404 A1 discloses a heat exchanger, in particular for high temperature (HTR) or very high temperature (VHTR) nuclear reactors, and constitutes the state of the art closest to the subject of claim 1.

There is therefore a need to further improve the heat exchangers of the type comprising compact plate heat exchanger modules arranged in a calender under pressure, in particular in order to confer a high unit thermal power and a high compactness, while at the same time guaranteeing an industrial realization.

The object of the invention is to at least partially meet this need.

Presentation of the invention

• une enceinte étanche présentant un axe central et comprenant, à l'une de ses extrémités longitudinales, au moins une entrée et une sortie du premier fluide et, à l'autre de ses extrémités longitudinales, au moins une entrée et une sortie du deuxième fluide, l'enceinte étanche étant adaptée pour être mise sous pression,
• au moins un module d'échangeur de chaleur intégrant un premier et deuxième circuits de fluide, s'étendant parallèlement à l'axe central et agencé à l'intérieur de l'enceinte,
• une structure de support et de maintien du au moins un module d'échangeur, fixée de manière rigide à l'enceinte,
• une chambre d'entrée ou de sortie du premier fluide, ménagée axialement entre le support et l'enceinte, et communiquant avec l'une de l'entrée et la sortie du premier circuit de fluide,
• un premier collecteur central s'étendant autour de l'axe central, agencé axialement à l'opposé de la chambre et, communiquant d'une part avec l'une de l'entrée et de la sortie du premier fluide de l'enceinte et d'autre part avec l'autre de l'entrée et la sortie du premier circuit de fluide,
• un collecteur annulaire agencé autour du premier collecteur central et du au moins un module d'échangeur jusqu'au moins le support en formant un espace de guidage du premier fluide et, communiquant d'une part avec l'autre de l'entrée et de la sortie du premier fluide de l'enceinte et d'autre part avec la chambre,
• au moins une tuyauterie d'entrée communiquant d'une part avec l'entrée du deuxième fluide de l'enceinte, et d'autre part avec l'entrée du deuxième circuit de fluide,
• au moins une tuyauterie de sortie communiquant d'une part avec la sortie du deuxième fluide de l'enceinte, et d'autre part avec la sortie du deuxième circuit de fluide, les tuyauteries n'étant pas supportées par la structure de support et de maintien.

To do this, the subject of the invention is a heat exchanger between a first and a second fluid, comprising:

• a sealed enclosure having a central axis and comprising, at one of its longitudinal ends, at least one inlet and an outlet of the first fluid and, at the other of its longitudinal ends, at least one inlet and one outlet of the second fluid , the sealed enclosure being adapted to be pressurized,
• at least one heat exchanger module incorporating a first and second fluid circuit, extending parallel to the central axis and arranged inside the enclosure,
• a structure for supporting and holding the at least one exchanger module, rigidly fixed to the enclosure,
• an inlet or outlet chamber of the first fluid, arranged axially between the support and the enclosure, and communicating with one of the inlet and the outlet of the first fluid circuit,
• a first central collector extending around the central axis, arranged axially opposite the chamber and communicating on the one hand with one of the inlet and the outlet of the first fluid of the enclosure and on the other hand with the other of the inlet and the outlet of the first fluid circuit,
• an annular collector arranged around the first central collector and the at least one exchanger module to at least the support forming a guiding space of the first fluid and communicating on the one hand with the other of the inlet and the output of the first fluid of the enclosure and secondly with the chamber,
• at least one inlet pipe communicating on the one hand with the inlet of the second fluid of the enclosure, and on the other hand with the inlet of the second fluid circuit,
• at least one outlet pipe communicating with the outlet of the second fluid of the enclosure and with the outlet of the second fluid circuit, the pipes being not supported by the support structure maintenance.

By "collector" means here and in the context of the invention a device for dispensing or collecting a fluid, respectively to or from one or more channels.

By "piping" is meant here and in the context of the invention, a conduit for dispensing or collecting a fluid to and from a single channel.

By "the pipes not being supported by the supporting and holding structure" is meant here and in the context of the invention that the support structure does not serve to support the pipes and that it receives no mechanical stress or adverse thermal stress through the pipes. In other words, the pipes are arranged at a distance from the support and holding structure. In other words, the pipes and the supporting and holding structure are mechanically and thermally decoupled from each other.

In other words, the invention consists first and foremost in defining a heat exchanger structure that makes it possible to bring and recover the primary fluid, such as sodium, at the same longitudinal end and away from the longitudinal end through which the secondary fluid, such as nitrogen, is fed and recovered. This makes it possible to have a physical separation between the paths of the two fluids in the exchanger with the possibility of having in particular a regulated access for one of the fluids, such as sodium and not regulated for the other fluids, such as than nitrogen.

Thus, compared to the heat exchanger according to the publication [1], it eliminates the slippery seal to ensure between hot nitrogen recovery collector and hot sodium supply collector.

In addition, the invention consists in rigidly fixing the support structure of the exchanger modules to the sealed enclosure and in bringing the coldest fluid (secondary fluid) to the support side. Thanks to this, the support structure is subjected to relatively low temperatures, and therefore it is less thermally constrained.

In the vertical operating configuration, the heat exchanger allows gravity draining of the primary fluid from the bottom of the sealed enclosure, opposite the first central manifold through which the secondary fluid, which is disposed in the upper part of the sealed enclosure, is extracted.

Another advantage with respect to the heat exchanger according to the publication [1] is that it avoids the flexibility of the support structure of the exchanger modules and pipes.

In summary, by virtue of the invention, a compact heat exchanger with a high unit thermal power is obtained for a liquid-gas metal exchange and whose industrial production can be guaranteed easily and reliably.

• une pluralité de modules d'échangeur de chaleur, s'étendant chacun parallèlement à l'axe central (X) et agencés chacun à l'intérieur de l'enceinte externe,
• une pluralité de tuyauteries d'entrée communiquant chacune d'une part avec l'entrée du deuxième fluide de l'enceinte, et d'autre part avec l'entrée du deuxième circuit de fluide d'un des modules d'échangeur,
• une pluralité de tuyauteries de sortie communiquant d'une part avec la sortie du deuxième fluide de l'enceinte, et d'autre part avec la sortie du deuxième circuit de fluide. La puissance thermique unitaire d'un tel échangeur est élevée.

According to an advantageous embodiment, the heat exchanger comprises:

• a plurality of heat exchanger modules, each extending parallel to the central axis (X) and each arranged inside the outer enclosure,
• a plurality of inlet pipes communicating each on the one hand with the inlet of the second fluid of the enclosure, and on the other hand with the inlet of the second fluid circuit of one of the exchanger modules,
• a plurality of output pipes communicating on the one hand with the output of the second fluid of the chamber, and on the other hand with the output of the second fluid circuit. The unit thermal power of such an exchanger is high.

Preferably, especially for reasons of compactness and distribution of the fluids, the plurality of inlet pipes communicates with a second central collector.

Preferably, especially for reasons of compactness and distribution of the fluids, the plurality of outlet pipes communicates with a third central collector.

In an advantageous embodiment, the third central collector is arranged coaxially around the second central collector.

According to an advantageous variant, the inlet of the first and / or second fluid circuit of each exchanger module is arranged at a longitudinal end of each module.

According to an advantageous variant, the output of the first and / or the second fluid circuit being arranged at a longitudinal end of each module.

Advantageously, the inlet of the first fluid circuit and the outlet of the second fluid circuit of each exchanger module being arranged at the same longitudinal end and the inlet of the second fluid circuit and the outlet of the first fluid circuit of each exchanger module being arranged at the same opposite longitudinal end.

The invention also relates, in another of its aspects, to a method of operating the heat exchanger which has just been described, the sealed chamber being arranged substantially vertically with the inlet and the outlet of the first fluid. top and the inlet and the outlet of the second fluid at the bottom.

The invention also relates to the use of the heat exchanger which has just been described, the first fluid being a secondary fluid being a gas or a mixture of gases and the second fluid as the primary fluid being a liquid metal.

According to an advantageous embodiment, the first fluid mainly comprises nitrogen and the second fluid is liquid sodium.

The first or the second fluid can come from a nuclear reactor.

Finally, the invention relates to a nuclear installation comprising a fast neutron nuclear reactor cooled with liquid metal, especially liquid sodium said RNR-Na or SFR and a heat exchanger described above.

detailed description

• la figure 1 est une vue en coupe longitudinale et en perspective d'un échangeur de chaleur selon l'état de l'art;
• la figure 1A est une vue en perspective et en écorché de l'échangeur de chaleur selon la figure 1;
• les figures 1B et 1C sont des vues de détail de l'échangeur de chaleur selon la figure 1 ;
• la figure 2 est une vue en perspective et en écorché d'un échangeur de chaleur selon l'invention ;
• la figure 2A est une vue en perspective et en écorché de la partie supérieure d'un échangeur de chaleur selon la figure 2 ;
• la figure 2B est une vue en perspective et en écorché de la partie inférieure d'un échangeur de chaleur selon la figure 2 ;
• la figure 3 est une vue en perspective de la pluralité de modules d'échangeur et d'une partie de la structure support de l'échangeur de chaleur selon la figure 2 ;
• la figure 4 est une vue en perspective de la pluralité de modules d'échangeur et d'une partie supplémentaire de la structure support de l'échangeur de chaleur selon la figure 2 ;
• la figure 5 est une vue en perspective de la pluralité de modules d'échangeur et d'une partie encore supplémentaire de la structure support de l'échangeur de chaleur selon la figure 2 ;
• la figure 5A est une vue de détail de la figure 5 ;
• la figure 6 reprend la figure 5 et illustre en outre en perspective le premier collecteur central de l'échangeur de chaleur selon l'invention ;
• la figure 7 reprend la figure 6 et illustre en outre en perspective les tuyauteries d'entrée et de sortie d'un des fluides ainsi que leurs collecteurs centraux de l'échangeur de chaleur selon l'invention ;
• la figure 8 est une vue isolée en perspective des tuyauteries d'entrée et de sortie d'un des fluides ainsi que de leurs collecteurs centraux montrés en figure 7 ;
• la figure 8A reprend la figure 7 et illustre en outre en perspective l'agencement d'une partie du collecteur annulaire ainsi que l'agencement des tuyauteries d'entrée et de sortie et de leurs collecteurs centraux dans le fond de l'enceinte étanche de l'échangeur selon l'invention;
• la figure 9 est une vue en perspective et en écorché de l'agencement relatif entre le couvercle de l'enceinte étanche et une autre partie du collecteur annulaire.

Other advantages and characteristics of the invention will emerge more clearly on reading the detailed description of exemplary embodiments of the invention, given by way of nonlimiting illustration and with reference to the following figures among which:

• the figure 1 is a longitudinal sectional view in perspective of a heat exchanger according to the state of the art;
• the Figure 1A is a perspective and cutaway view of the heat exchanger according to the figure 1 ;
• the Figures 1B and 1C are detailed views of the heat exchanger according to the figure 1 ;
• the figure 2 is a perspective and cutaway view of a heat exchanger according to the invention;
• the Figure 2A is a perspective and cutaway view of the upper part of a heat exchanger according to the figure 2 ;
• the Figure 2B is a perspective and cutaway view of the lower part of a heat exchanger according to the figure 2 ;
• the figure 3 is a perspective view of the plurality of exchanger modules and a part of the support structure of the heat exchanger according to the figure 2 ;
• the figure 4 is a perspective view of the plurality of exchanger modules and an additional portion of the support structure of the heat exchanger according to the figure 2 ;
• the figure 5 is a perspective view of the plurality of exchanger modules and an additional portion of the support structure of the heat exchanger according to the figure 2 ;
• the Figure 5A is a detail view of the figure 5 ;
• the figure 6 resumes figure 5 and further illustrates in perspective the first central collector of the heat exchanger according to the invention;
• the figure 7 resumes figure 6 and further illustrates in perspective the inlet and outlet pipes of one of the fluids and their central collectors of the heat exchanger according to the invention;
• the figure 8 is an isolated perspective view of the inlet and outlet pipes of one of the fluids and their central collectors shown in FIG. figure 7 ;
• the figure 8A resumes figure 7 and further illustrates in perspective the arrangement of a portion of the annular collector and the arrangement of the inlet and outlet pipes and their central collectors in the bottom of the sealed enclosure of the exchanger according to the invention ;
• the figure 9 is a perspective and cutaway view of the relative arrangement between the lid of the sealed enclosure and another portion of the annular manifold.

Throughout the present application, the terms "vertical", "lower", "upper", "lower", "high", "below" and "above" are to be understood by reference relative to a heat exchanger according to the invention with its sealed enclosure as it is in vertical configuration of operation. Thus, in an operating configuration, the central axis X of the sealed enclosure 2 is vertical and the cover 20 is at the top.

Likewise, throughout the present application, the terms "inlet", "outlet", "downstream" and "upstream" are to be understood with reference to the direction of flow of one or other of the two fluids. through the heat exchanger according to the invention.

For the sake of clarity, the same references designate the same elements for both a heat exchanger 1 according to the state of the art already described with reference to the Figures 1 to 1C , and for a heat exchanger 1 according to the invention described with reference to Figures 2 to 9 .

The Figures 1 to 1C of the heat exchanger 1 according to the state of the art, as disclosed in the publication [1] have already been commented in the preamble. They are therefore not detailed below.

The inventors of the present invention have sought to retain the advantages of the heat exchanger 1 according to this publication [1], namely essentially a good compactness and a high unit thermal power, while avoiding its major drawback. In this way, they sought to guarantee the distribution of fluids industrially.

So, they proposed the heat exchanger 1 illustrated in Figures 2 to 9 which is intended to transfer heat between a first fluid, which is nitrogen (N ₂ ) (cold fluid) and a second fluid which is liquid sodium (Na).

The heat exchanger 1 is shown in its vertical operating configuration with the lid 20 of the sealed enclosure on top.

The heat exchanger 1 of central axis X comprises a sealed enclosure 2 in which is housed a plurality of 3 exchanger modules 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8 arranged vertically and parallel to the X axis. In the embodiment illustrated in Figures 2 to 10 , the number of identical exchanger modules is equal to eight.

The sealed enclosure 2 is of substantially cylindrical general shape and consists essentially of a cover 20, a bottom 21 and a side shell 22 in the form of a ferrule. The lid 20 and the ferrule 22 are assembled together at means of a first group of bolts 23. The bottom 21 and the ferrule 22 are also assembled together by means of a second group of bolts 23.

The sealed enclosure 2 has at one of its longitudinal ends, an inlet 10 and an outlet 11 of the nitrogen

At the other 2b of the longitudinal ends of the chamber 2 are provided an inlet 12 and an outlet 13 of the liquid sodium.

Each exchanger module 3.1 to 3.8 integrates two fluid circuits, one of which is dedicated to the circulation of sodium (Na) coming from a nuclear reactor RNR-Na, as the primary fluid of the exchanger module, and the other dedicated to the circulation of nitrogen (N2) as a secondary fluid.

The plurality of heat exchanger modules 3.1 to 3.8 is supported by a supporting and holding structure 4. The support and holding structure 4 is thus fixed rigidly to the external enclosure 2.

A nitrogen inlet chamber 5 is formed axially on the underside of the enclosure 2, at its lower longitudinal end 2b, between the support structure 4 and the bottom 21 of the enclosure 2. In other words, this chamber 5 is the space available between the support structure 4 and the bottom 21 of the enclosure 2.

This chamber 5 communicates with each unrepresented input of the integrated nitrogen circuit in one of the exchanger modules 3.1 to 3.8.

A. opposite the chamber 5, a first central collector 6 is arranged axially around the central axis (X). This first central collector 6 has the function of recovering the hot nitrogen to which the heat of the sodium has been transferred in the exchanger modules 3.1 to 3.8. This hot collector 6 is thus common to the modules 3.1 to 3.8 but each of them independently supplies this collector through the outlet 30.

This central collector 6 thus communicates upstream with each output 30 of the integrated nitrogen circuit in one of the exchanger modules 3.1 to 3.4. Downstream, this central collector communicates with the outlet 11 of the nitrogen of the enclosure 2, i.e. through the cover 20.

An annular collector 7 is arranged coaxially around the central collector 6 and exchanger modules 3.1 to 3.8 forming a nitrogen guide space. This annular collector 7 serves to bring the cold nitrogen into the chamber 5.

More specifically, this annular manifold 7 consists essentially of a deflector of flared shape 70 and a cylindrical shell 71. The annular collector 7 can be constituted in one piece made by boiler.

A relative arrangement between the baffle 70 and the enclosure lid 20 is shown in FIG. figure 9 .

The guiding space 72 of the cold nitrogen coming from the inlet 10 is delimited from upstream to downstream, outside by the enclosure 2 and inside, only by the annular collector 7, it is that is to say by the deflector 70 and the shell 71. Thus, the function of the shell 71 is to guide the cold nitrogen along the wall of the sealed enclosure 2, in order to distribute it through the lower ends of the modules 3.1 to 3.8. In other words, the cold nitrogen distributed in the annular space 72 sets the temperature of the wall of the sealed enclosure 2, typically at about 330 ° C.

The annular collector 7 thus communicates upstream with the inlet 10 of the nitrogen of the enclosure 2 and downstream with the chamber 5.

A plurality 8 of inlet pipes 81, 82, 83, 84, 85, 86, 87, 88 is arranged to bring the hot sodium into each of the inlets 31, 32, 33, 34, 35, 36, 37, 38 of the integrated sodium circuit in one of the exchanger modules 3.1 to 3.8.

Thus, each inlet pipe 81 to 88 communicates upstream with the inlet 12 of the sodium of the enclosure 2, and downstream with each inlet 31 to 38 of the sodium circuit integrated in one of the exchanger modules 3.1 to 3.8 . Advantageously, the plurality 8 of inlet pipes communicates with a second central collector 14.

As best illustrated in figure 2 , each input 31 to 38 is made on the top of a module 3.1 to 3.8: the plurality 8 of inlet pipes 81 to 88 is curved so as to lead to these longitudinal inlets 31 to 38.

As a variant not shown, it can be provided that each input 31 to 38 is made on a longitudinal side in the upper part of a module 3.1 to 3.8.A plurality 9 of outlet pipes 91, 92, 93, 94, 95, 96, 7, 98 is arranged to extract the cold sodium from each of the outputs of the integrated sodium circuit in one of the exchanger modules 3.1 to 3.8.

Thus, each outlet pipe 91 to 98 communicates upstream with an output of the sodium circuit integrated in one of the exchanger modules 3.1 to 3.8 and downstream with the outlet 13 of the sodium of the enclosure 2. The outlet 13 of the sodium cold is towards the bottom of the chamber 2 through the bottom 21. Advantageously, the plurality 9 of output pipes communicates with a third central collector 17.

An advantageous embodiment of the plurality of inlet and outlet pipes 9 and their relative arrangement is shown in FIG. Figure 7A it is clearly seen the coaxial arrangement of the third central collector 17 around the second central collector 14.

As best illustrated in figure 3 the supporting and holding structure 4 comprises a support platform 40 which bears against a peripheral shoulder inside the bottom 21 of the enclosure 2. According to the invention, no relative sealing function between the feed cold nitrogen and the recovery of hot nitrogen is not to be made for the platform 40. Thus, as it emerges better later, no flexibility by metal bellows between the inlet pipe 8 and outlet 9 of the sodium is not to be realized.

The platform 40 can thus be perforated, in particular to reduce the weight. When it is desired to clear access to the lower surfaces of the exchanger modules 3.1 to 3.8, large openings can be made. Thus, for example, the platform 40 may be a beam assembly made in welded mechanics. The modules 3.1 to 3.8 are placed on the platform 40 and are held in position by means of brackets fixed on the platform 40 ( figure 3 ).

The supporting and holding structure 4 also comprises means 41 for lateral retention of the exchanger modules 3.1 to 3.8, also fixed on the platform 40 (FIG. figure 4 ), For example, the lateral holding means 41 may be a beam assembly made of welded mechanics which matches the outer shape of the modules. It may be two groups of beams at 90 ° to one another and dividing the modules 3.1 to 3.8 into four equal groups ( figure 4 ).

A sealing plate 42 is screwed onto the holding structure 41 ( figure 5 ). Its function is to seal the cold nitrogen fed into the heat exchanger and the hot nitrogen leaving each exchanger module 3.1 to 3.8 is recovered by the first central collector 6.

The first central collector 6 or hot nitrogen collector is attached directly to the sealing plate 42.

An advantageous embodiment of realization of the sliding sealing system between central collector 6 and modules 3.1 to 3.8 is shown in FIG. Figure 5A a flange 43 is fixed to the sealing plate 42 by means of screws 44 and segment joints 45 between the outlet 30 of the modules and the collector 6 are arranged. Seals 46 are also arranged between flange 43 and sealing plate 42. Alternatively, metal bellows could be provided.

The operation of the heat exchanger 1 which has just been described will now be briefly explained in relation to the path of nitrogen and sodium.

The cold nitrogen arrives, at a temperature of the order of 330 ° C. and at a pressure of the order of 180 bar (18 MPa), through the inlet 10 and is then fed through the annular collector 7 at the bottom of the chamber. chamber 2 to the inlet chamber 5 above the bottom 21, as illustrated by the lateral arrows in figure 2 .

The nitrogen then flows through the heat exchanger modules 3.1 to 3.8 in which the heat from the hot sodium is transferred thereto.

The nitrogen, which has become hot at a temperature of the order of 515 ° C., emerges from the modules 3.1 to 3.8 and is then withdrawn from the enclosure through the outlet 11 via the first central collector 6.

The hot sodium is brought, at a temperature of the order of 530 ° C, by the second central collector 14 through the inlet 12 and is distributed in each exchanger module 3.1 to 3.8 by the pipes 81 to 88, as illustrated by the rising vertical arrows in figure 2 .

The sodium then passes through the heat exchanger modules 3.1 to 3.8 in which it transfers its heat to the nitrogen.

The sodium, which has become cold at a temperature of the order of 345 ° C., emerges from the modules 3.1 to 3.8 at their lower ends and is then extracted from the enclosure 2 through the outlet 13 via the outlet pipes 91 to 98. .

In a heat exchanger 1 according to the invention, the cold gas (cold N2) flows from top to bottom and counteracts with the hot sodium. So, as better illustrated in Figures 2A and 2B , the cold gas (N2 cold) reaches the chamber 5, enters the lower part of the modules 3.1 to 3.8 and hot spring through the outputs 30 of modules to feed the collector 6 and finally leaves the heat exchanger by the outlet 11. As illustrated in Figure 2A in the heat exchanger 1 according to the invention, there is no gas inlet manifold by module: the gas channels delimited between the deflector 7 and the chamber 2 open directly into the latter, at the chamber 5. Thus, the chamber 5 defined by the chamber 2 acts as the inlet manifold of gas.

The circulation of the fluids is compatible with a circulation in natural convection.

In practice a forced convection is provided for the nominal operation, ie to initiate the movement of the gas and the liquid sodium in the exchanger 1. Then, in case of incident (stopping pumps for example), the circulation can continue with natural convection. Indeed, the cooling sodium tends to go down naturally and when it cools in a heat exchanger module 3.1 to 3.8, its extraction is facilitated by gravity. Thus, the sodium becomes cold is removed at the bottom of the device which improves its gravity drain.

The cold gas (N ₂ ) meanwhile descends along the wall of the sealed chamber 2 and it rises at the same time as it is heated to be extracted by the central collector 6. The heat promotes its progression upwards of the exchanger 1.

Other variants and improvements may be provided without departing from the scope of the invention.

REFERENCE CITEE

1. [1]: " Innovative power conversion system for the French SFR prototype, ASTRID ", L.Cachon et al., Proceeding of ICAPP'12, Chicago, USA, June 24-28, 2012 , Paper 12300.

Claims (13)

1. A heat exchanger (1) between a first (N₂) and a second (Na) fluid, comprising:

   - a sealed enclosure (2) having a central axis (X) and comprising, at one (2a) of its longitudinal ends, at least one inlet (10) and one outlet (11) for the first fluid and, at the other of its longitudinal ends (2b), at least one inlet (12) and one outlet (13) for the second fluid, the sealed enclosure being adapted to be pressurized,

   - at least one heat exchanger module (3.1 to 3.8) incorporating a first and a second fluid circuit, extending parallel to the central axis (X) and arranged inside the enclosure,

   - a structure (4, 40) for supporting and holding the at least one exchanger module, rigidly fixed to the enclosure (2),

   - an inlet or outlet chamber (5) for the first fluid, formed axially between the support and the enclosure, and communicating with one of the inlet and the outlet (30) of the first fluid circuit,

   - a first central manifold (6) extending around the central axis (X), arranged axially opposite the chamber and communicating, on the one hand, with one of the inlet (10) and the outlet (11) for the first fluid of the enclosure and, on the other hand, with the other of the inlet and the outlet (30) of the first fluid circuit,

   - an annular manifold (7) arranged around the first central manifold (6) and the at least one exchanger module at least to the support (4, 40), forming a guiding space (72) for the first fluid and communicating, on the one hand, with the other of the inlet (10) and the outlet (11) for the first fluid of the enclosure and, on the other hand, with the chamber (5),

   - at least one inlet conduit (8, 81 to 88) communicating on the one hand with the inlet (12) for the second fluid of the enclosure, and, on the other hand, with an inlet (31 to 38) of the second fluid circuit,

   - at least one outlet conduit (9, 91 to 98) communicating on the one hand with the outlet (13) for the second fluid of the enclosure, and, on the other hand, with an outlet of the second fluid circuit, the conduits (8, 81 to 88; 9, 91 to 98) not being supported by the support and holding structure.
2. The heat exchanger (1) as claimed in claim 1, comprising:

   - a plurality (3) of heat exchanger modules (3.1 to 3.8), each extending parallel to the central axis (X) and each arranged inside the outer enclosure,

   - a plurality (8) of inlet conduits (81 to 88) each communicating on the one hand with the inlet (12) for the second fluid of the enclosure, and on the other hand with the inlet (31 to 38) of the second fluid circuit of one of the exchanger modules,

   - a plurality (9) of outlet conduits (91 to 98) communicating on the one hand with the outlet (13) for the second fluid of the enclosure, and on the other hand with the outlet of the second fluid circuit.
3. The heat exchanger (1) as claimed in claim 2, the plurality (8) of inlet conduits communicating with a second central manifold (14).
4. The heat exchanger (1) as claimed in claim 2 or 3, the plurality (9) of outlet conduits communicating with a third central manifold (17).
5. The heat exchanger (1) as claimed in claim 3 in combination with claim 4, the third central manifold (17) being arranged coaxially around the second central manifold (14).
6. The heat exchanger (1) as claimed in one of the preceding claims, the inlet of the first (31 to 38) and/or of the second fluid circuit of each exchanger module (3.1 to 3.8) being arranged at a longitudinal end of each module.
7. The heat exchanger (1) as claimed in one of the preceding claims, the outlet of the first (30) and/or of the second fluid circuit being arranged at a longitudinal end of each module.
8. The heat exchanger (1) as claimed in claim 6 in combination with claim 7, the inlet of the first fluid circuit and the outlet of the second fluid circuit of each exchanger module being arranged at a same longitudinal end and the inlet of the second fluid circuit and the outlet of the first fluid circuit of each exchanger module being arranged at a same opposite longitudinal end.
9. A method for operating the heat exchanger (1) as claimed in one of the preceding claims, the sealed enclosure being arranged substantially vertically with the inlet and the outlet for the first fluid at the top and the inlet and the outlet for the second fluid at the bottom.
10. The use of the heat exchanger (1) as claimed in any one of claims 1 to 8, the first fluid, as secondary fluid, being a gas or a gas mixture, and the second fluid, as primary fluid, being a liquid metal.
11. The use of the assembly as claimed in claim 10, the first fluid primarily comprising nitrogen and the second fluid being liquid sodium.
12. The use as claimed in claim 10 or 11, the first or the second fluid originating from a nuclear reactor.
13. A nuclear installation comprising a fast neutron nuclear reactor cooled with liquid metal, notably liquid sodium, called RNR-Na or SFR, and a heat exchanger as claimed in one of claims 1 to 8.

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