METHOD FOR PRODUCING A HEAT EXCHANGER BY BRAZING AND BRAZING TOOLING

Abstract

The invention relates to a method for brazing a heat exchanger from a bundle (50) of tubes with end surfaces, comprising a first brazing operation of a first material (1) onto the bundle (50) to form a first sacrificial layer of the first material (1), a second brazing operation of a second material (2) onto the bundle (50) and onto the first layer to form a second layer of the second material (2) at a predetermined non-zero distance from the end surfaces, a cooling step of the second layer to form a heat exchanger plate bonding the bundle (50), and a step of removing the first material (1) separating it from the heat exchanger plate and the bundle (50), and relates to brazing tooling for implementing the method, and to a motor vehicle comprising a heat exchanger thus produced. Figure 5

Description

Title of the invention: METHOD FOR MAKING A HEAT EXCHANGER BY BRAZING AND BRAZING TOOLING

[0001] The invention relates to a method for producing by brazing an exchanger from a bundle of tubes comprising tubes with end surfaces.

[0002] The invention further relates to brazing tools for implementing this process.

[0003] The invention further relates to a motor vehicle comprising at least one heat exchanger made according to this process.

[0004] The invention relates to the field of thermodynamic machines, in particular for the automotive industry.

[0005] Document FR3120571 describes a reheated and recirculated gas turbine-type turbomachinery device with intercooling, particularly for motor vehicles. The turbomachinery device comprises a first turbocharger, a second turbocharger, two combustion chambers or an exhaust line, an intercooler, and a heat exchanger. The device is configured to send a fluid flow from the first compressor to the intercooler, to the second compressor, to the heat exchanger, and to the turbines. The performance is closely related to the capacity of the heat exchanger(s).

[0006] Document FR3141723B1 describes a motor vehicle comprising a turbogenerator system which includes: multiaxial turbochargers comprising compressors and turbines; a cooler; a recuperator; two combustion chambers; a turbomachine comprising so-called power turbines; and an electric generator. The invention simplifies the architecture by using an electric machine and reduces the overall size by separating the turbocharger shafts.

[0007] In both cases, the design requires the use of a heat exchanger of the recuperator type and takes into account several criteria: improving the efficiency of the recuperator by proposing a counter-flow exchanger, reducing heat losses to the outside via the walls and external surfaces, the modularity of the recuperator adaptable to the application, the possibility of modifying the positions of the inlet / outlet of the exchanger, the possibility of modifying the number of passage sections (tubes) in each stage of the exchanger, the possibility of modifying the cross-section of each passage in each stage of the exchanger, the possibility of modifying the materials in each passage section, the possibility of modifying the number of passes (supply and return) in the exchanger, and the possibility of using different types of working fluid (Air-Air / Air-Water / Air-ORC / Water-Water / Water-ORC), the possibility of using several working fluids (for example, using the recuperator in Air-Air mode and also preheating another ORC type fluid for a Rankine loop, or using the energy to preheat a heat transfer circuit to ensure the thermal needs of the vehicle especially in winter, or other.

[0008] These constraints which condition optimal performance lead to the design of particular exchangers, often more complex than conventional exchangers, but it is essential to ensure the quality of the brazing of the exchanger tubes with the structure of the exchanger, while controlling production costs as closely as possible, and reducing the manufacturing cycle time.

[0009] The objective of the present invention is to overcome these constraints by proposing a manufacturing method for the heat exchanger, and in particular for brazing the tubes onto the plates. A new brazing method is proposed, with a new technique, allowing each series of tubes to be brazed with different types of brazing materials.

[0010] To achieve this objective, the invention proposes a method for producing by brazing an exchanger from a bundle of tubes comprising tubes with end surfaces.

[0011] According to the invention, said process comprises a first operation of brazing a first material onto said tube bundle for the formation of a first sacrificial layer of said first material, a second operation of brazing a second material onto said tube bundle and onto said first layer for the formation of a second layer of said second material at a predetermined and non-zero distance from said end surfaces, and a step of cooling said second layer for the formation of a heat exchanger plate securing said tube bundle, followed by a step of removing said first material to separate said first material from said heat exchanger plate and said tube bundle.

[0012] Thus the invention makes it possible to do away with the prior manufacturing by machining of a costly exchanger plate, to eliminate the delicate operations of brazing the exchanger tubes onto such a machined plate, and guarantees a perfect fit of the exchanger thus produced.

[0013] Advantageously, the process comprises a first step of selecting said first material with a first melting temperature and a first density, and said second material with a second melting temperature and a second density, with said second melting temperature higher than said first melting temperature and with said second density lower than said first density, said first step comprising placing said tube bundle at an ambient temperature below 40°C on a brazing tool comprising a receptacle fitted with a flat bottom receiving said bundle of tubes in support at said end surfaces, and the preparation of a first quantity of said first material intended for the formation of said first sacrificial layer according to a thickness equal to said predetermined distance, and of a second quantity of said second material intended for the formation of said second layer for the formation of an exchanger plate.

[0014] Thus, a first volume of the first sacrificial layer of said first material is determined in advance, as is a second volume of the second layer of said second material intended to constitute the heat exchanger plate. Choosing a second melting temperature higher than said first melting temperature ensures the coexistence of two liquid phases above the second melting temperature, when the first and second materials are in contact with each other in the same container, and choosing a second density lower than the first density then allows the separation of a liquid phase of the second material floating on a liquid phase of the first material.

[0015] Advantageously, the process comprises, after the said first step, a second step of heating to a temperature greater than or equal to the said first melting temperature and strictly less than the said second melting temperature, the said second step comprising the said first brazing operation by pouring the entirety of the said first quantity of the said first material into the said receptacle in contact for brazing with the said bundle of tubes.

[0016] Thus the first material forms a first layer which is in contact both with the bottom of the material and with the bundle of tubes, from the bottom of the receptacle up to a certain level defined by the shape of the receptacle and by the first volume of the first material, this level being distant from the bottom of the receptacle by the predetermined distance.

[0017] Advantageously, the process comprises, after the second step, a third heating step to a temperature greater than or equal to the second melting temperature, the third step comprising the second brazing operation by pouring the entire second quantity of the second material into the receptacle above the first quantity of the first material in brazing contact with the tube bundle and the first layer of the first material.

[0018] Thus the second material forms a second layer which is in contact both with the sides of the receptacle, with the first layer of the first material which it covers, and with the bundle of tubes.

[0019] Advantageously, the process comprises, after the third step, a fourth step of hardening the second layer of the second material at a hardening temperature lower than the second melting temperature and higher than said first melting temperature for the formation of said heat exchanger plate.

[0020] Thus the heat exchanger plate is solidified, while the first layer of the first material is still in a liquid state.

[0021] Advantageously, said process comprises, after said fourth step, a fifth step of removing said first material to separate said first material from said exchanger plate and said tube bundle and to decouple said second material from said first material at an intermediate temperature lower than said second melting temperature and higher than said first melting temperature, by mechanical removal and / or by draining said first liquid material.

[0022] Thus takes place the complete separation of the first material and the second material, which alone remains in contact with the exchanger tubes with which the exchanger plate thus formed by the solidified second material is perfectly brazed.

[0023] Advantageously, the process comprises, after the said fifth step, a sixth step of returning to the said ambient temperature and solidifying the said second material in the said exchanger plate.

[0024] The exchanger is then ready for use, and requires no further machining.

[0025] The invention further relates to brazing tools for implementing this process.

[0026] According to the invention, said brazing tooling comprises a receptacle having a flat bottom receiving said tube bundle in support at said end surfaces of said tubes of said tube bundle, and comprises, on the one hand, a first reservoir arranged to contain a first quantity of said first material in solid state at said ambient temperature, and which is arranged to pour it in liquid state by gravity into said receptacle through a first conduit, and on the other hand, a second reservoir containing a second quantity of said second material in solid state at said ambient temperature, and which is arranged to pour it in liquid state by gravity into said receptacle through a second conduit.

[0027] This tooling is simple, easy to make, and guarantees, on the one hand, the predetermined distance between the end of the tubes and the exchanger plate, and on the other hand, the thickness of the exchanger plate.

[0028] Advantageously, said receptacle constitutes a mold defining the shape and edge of said exchanger plate.

[0029] Thus, the manufacture, easy to machine or produce thanks to the flat bottom of the receptacle, of a receptacle suitable for a particular shape of exchanger plate allows obtaining any shape of exchanger plate, without particular complexity, and at a modest production cost.

[0030] The invention further relates to a motor vehicle comprising at least one heat exchanger made according to this process.

[0031] Such an exchanger can thus be of the recuperative type, and ensure the proper functioning of an energy converter in the form of a turbogenerator, which makes it possible to ensure the vehicle a low level of emissions, a low level of noise, the absence of vibrations, very low maintenance, the ability to operate with several types of fuels, and a high efficiency.

[0032] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates in the form of a flowchart the successive steps of a process for producing by brazing an exchanger from a bundle of tubes comprising tubes with end surfaces, according to the invention; - [Fig.2] schematically illustrates in cross-section by the axes of a row of tubes, like the figures that follow, a bundle of tubes prepared for the first step of the process; - [Fig.3] schematically illustrates the setup, for the execution of the first step of the process, of a brazing tool comprising a flat-bottomed receptacle receiving in support the end surfaces of the bundle of tubes of [Fig.2], and comprising a first reservoir containing a first quantity of a first material in a solid state at room temperature, and which is arranged to discharge it in a liquid state by gravity into the receptacle through a first conduit, and a second reservoir containing a second quantity of a second material in a solid state at room temperature, and which is arranged to discharge it in a liquid state by gravity into the receptacle through a second conduit; the first material and the second material are chosen suitable for brazing with the tube bundle, the first material with a first melting temperature and a first density, the second material with a second melting temperature and a second density, with the second melting temperature higher than the first melting temperature, and with the second density lower than the first density; . - [Fig.4] schematically illustrates the first step of the process, at room temperature, with a first quantity of the first material in solid state in the first tank, and a second quantity of the second material in the second tank; - [Fig. 5] schematically illustrates the second stage of the process, at a temperature greater than or equal to the first melting temperature of the first material and strictly lower than the second melting temperature of the second material, this second step comprising the first brazing operation of the first material by pouring the entirety of the prepared first material into the brazing receptacle in contact with the tube bundle; - [Fig.6] schematically illustrates the third step of the process, at a temperature higher than the second melting temperature of the second material, this third step comprising the second brazing operation by pouring the entire second material into the receptacle above the first layer of the first material, in brazing contact with the tube bundle and the first layer of said first material; - [Fig.7] schematically illustrates the fourth step of the process, at a curing temperature lower than the second melting temperature and higher than the first melting temperature, for curing the second layer of the second material and forming the heat exchanger plate; - [Fig.8] schematically illustrates a first variant of the fifth step of removing the first material, at an intermediate temperature lower than the second melting temperature and higher than the first melting temperature, to separate this first material from the heat exchanger plate and the tube bundle, and to decouple the second material from the first material, by mechanical removal, in particular by extracting the tube bundle and its heat exchanger plate from the receptacle; - [Fig.9] schematically illustrates a second variant of the fifth step of removing the first material, by draining the first liquid material through an orifice of the receptacle; - [Fig. 10] schematically illustrates the sixth step of the process, at room temperature, for the complete solidification of the second material in the exchanger plate; - [Fig. 11] schematically illustrates a motor vehicle comprising a converter in the form of a turbogenerator including an exchanger made according to this process.

[0033] The invention relates to the technological field of heat exchangers, and in particular the brazing process dedicated to this type of exchanger.

[0034] Brazing consists of joining two surfaces together using a material that melts between the two surfaces. For example, it is known to braze a tube onto a plate, by using copper washers which, at high temperature, will melt and penetrate the material of the tube and the plate.

[0035] The invention proposes a new technique that allows tubes to be brazed onto plates using different types of materials, depending on the thermal conditions experienced by the tubes. For example, when tubes in certain areas of the heat exchanger are subjected to high temperatures, the alloys used are modified accordingly. This makes it possible to target a specific type of brazing in each section and reduce the cost of the process.

[0036] The materials used are chosen according to the brazing temperatures. The choice of the brazing material and the appropriate temperature depends on several factors, such as the materials being joined, the operating conditions, and the final application.

[0037] Soft soldering uses tin-based (Sn) alloys, often with lead (Pb), or lead-free alloys (e.g., tin-silver, tin-copper) as soldering materials, with a soldering temperature between 150°C and 250°C. The advantages are low cost and ease of application. The disadvantages are low mechanical strength and low resistance to high temperatures.

[0038] Hard soldering (or brazing) uses copper (Cu), silver (Ag), nickel (Ni), or zinc (Zn) alloys as brazing materials, with a brazing temperature between 450°C and 900°C. Common applications include mechanical components, pipe fittings, aircraft parts, and joints subjected to high temperatures or mechanical loads. The advantages consist of stronger joints capable of withstanding higher temperatures than soft soldering. The disadvantages are related to the process, which requires more heat and specialized equipment.

[0039] Silver soldering uses silver (Ag) alloys mixed with copper (Cu), zinc (Zn), or cadmium (Cd) as soldering materials, with a soldering temperature between 600°C and 800°C. Applications include jewelry making, the manufacture of precision instruments, and demanding metal assemblies. Advantages include high mechanical strength and good electrical and thermal conductivity. Disadvantages are related to the high cost of the silver-containing filler materials.

[0040] High-temperature brazing uses nickel (Ni), cobalt (Co), or titanium (Ti) alloys as brazing materials, at a brazing temperature exceeding 1000°C. Applications include aircraft engine components, aerospace applications, and equipment exposed to extreme temperatures. Advantages include corrosion resistance and High temperatures and high mechanical strength are required. The disadvantages are the need for special equipment and strict temperature control.

[0041] Different types of heat exchangers are known: tube and fin heat exchangers, plate and fin heat exchangers, 3D printed metallic microchannel heat exchangers (“Inconel ®”), plate heat exchangers.

[0042] These heat exchangers are made using several types of processes.

[0043] Brazing melts material at high temperature to couple two components of the recovery unit (for example tubes and plates).

[0044] Welding joins two components by welding without the addition of material.

[0045] 3D or three-dimensional printing makes it possible to print all the channels of an exchanger in metal.

[0046] The shrinkage, also called "entry-tight", with the installation of opposing components, at least one of which is heated, and tightening by returning to ambient temperature, with a dimensioning that takes into account the shrinkage.

[0047] These processes are costly and time-consuming.

[0048] Furthermore, on this type of heat exchanger, one is constrained by the use of high-quality brazing throughout, even in areas where the temperature is low. This makes the process expensive, and the process may not be well-suited to the temperature zones within the exchanger. To save time and reduce costs, the invention proposes an original process for brazing the heat exchanger.

[0049] Furthermore, the different sections in a heat exchanger are often not identical in terms of temperature. In current processes, all sections are brazed with the same material, which forces the use of the most expensive brazing material for all areas, even though this is unnecessary. The invention aims to save brazing materials by targeting each brazing material to each section of the heat exchanger.

[0050] The invention consists of proposing a method for brazing tubes onto plates for the design of a modular, high-efficiency heat exchanger with a variable flow area and minimized heat losses. This exchanger is suitable for applications where both fluids are gases, liquids or two-phase fluids, or a gas and a liquid or two-phase fluid. The exchanger can operate with two, three, or even more fluids. This heat exchanger can serve as a heat recovery unit or as an intercooler (air-to-air or air-to-water heat exchanger: a device for cooling the air exiting a compressor and used in turbocharged internal combustion engines), for a turbogenerator application, or any other type of application.

[0051] The constraints of heat exchangers are numerous and summarized below.

[0052] To have high heat exchange efficiency between the hot source (the high-temperature fluid) and the cold source (the low-temperature fluid). To achieve high efficiency, large heat transfer coefficients and a counter-current heat exchange architecture are required. With a counter-current heat exchanger, the outlet temperature of the cold fluid can exceed the outlet temperature of the hot fluid, which is not possible with a counter-current heat exchanger.

[0053] Having a low pressure drop. This is a very important criterion in the case of a turbogenerator application. The flow passes twice through the heat exchanger (once at the compressor outlet and once at the turbine outlet). Minimizing pressure drops increases the turbine's expansion ratio and, consequently, increases the power generated by the turbine. To minimize these pressure drops, it is advantageous to adapt the cross-sectional areas of the heat exchangers according to their position within the exchanger. Indeed, as the fluid (in the case of a gas) cools, its density decreases, and the cross-sectional areas can be reduced. Similarly, as the fluid heats up, its volumetric flow rate increases, and the cross-sectional areas must be increased. This is not possible with plate heat exchangers (possible with 3D-printed heat exchangers, but we have already discussed the limitations of these exchangers in the case of high-volume production applications).

[0054] Heat exchange at the walls must be controlled: if the collectors are external, there is significant heat exchange at the walls, which complicates the thermal insulation of the heat exchanger. Indeed, in the case of the turbogenerator, the hot inlet of the heat exchanger can be at temperatures exceeding 750°C. If the collector is external, the surface temperature is high, and significant heat losses must be managed. To minimize heat losses at the walls, it is advantageous to minimize the hot exchange surface in contact with the outside. Consequently, it is advantageous for the hot inlet to be located inside the heat exchanger.

[0055] The inlets / outlets of the heat exchanger have an impact on the volume and physical architecture of the machine. If the inlets / outlets are difficult to relocate, the design is constrained. It is advantageous to have a modular design where the inlets / outlets can be placed anywhere within the functional volume of the heat exchanger.

[0056] The choice of materials and cross-sections is paramount. The type of material has an impact on the heat transfer coefficients. However, some types of materials, such as copper or aluminum, have very high heat transfer coefficients, but poor high-temperature resistance characteristics. Similarly, some materials are lighter than others and allow for a reduction in weight. the total mass of the exchanger. Having a heat exchanger design where the type of materials can be adapted allows for increased heat exchange performance and minimized exchanger mass.

[0057] In certain applications, particularly in the case of turbogenerators, the gases exiting the heat exchanger remain hot. This is due to the high air temperature at the compressor outlet, and therefore the temperature of the gases exiting the hot side of the heat exchanger towards the ambient air is necessarily higher than the inlet temperature, which is the compressor outlet temperature (according to the second law of thermodynamics: heat exchange always flows from hot to cold). For example, the temperature of the gases exiting the heat exchanger in a turbogenerator application is around 300°C. These gases still contain energy that can no longer be recovered in the turbogenerator's thermodynamic cycle. Using a third (or even a fourth) working fluid to recover the remaining energy increases the overall efficiency of the system.Thus, the possibility of exchanging heat with a third fluid is important in several types of applications. This allows for a reduction in system complexity (instead of having two exchangers, one can be used, for example).

[0058] It is necessary to develop a process that allows for the large-scale industrialization of a heat exchanger, and in particular a heat recovery unit. This new process must allow the type of brazing to be adapted for each application.

[0059] The brazing process of the heat exchanger aims to secure the tubes to a plate that will be formed by brazing. Each series of tubes (called a stage) can be brazed with a specific type of material.

[0060] Thus, instead of creating a costly pre-formed plate to hold the tubes, the process directly constructs this plate from the brazing material by immersing the tubes in the solution with the molten brazing material. It is then no longer necessary to fabricate a flange with the various holes to which the tubes are subsequently assembled and positioned.

[0061] The steps of a process according to the invention are schematically illustrated in [Fig. 1].

[0062] This process is a brazing process for producing an exchanger 70 from a tube bundle 50 comprising tubes 51 with end surfaces 52, as shown in [Fig. 2].

[0063] According to the invention, this method comprises a first brazing operation of a first material 1 onto this bundle of tubes 50 to form a first sacrificial layer of the first material 1. This method then comprises a second brazing operation of a second material 2 onto the bundle of tubes 50 and onto the first layer, to form a second layer of the second material 2 at a predetermined and non-zero distance from the end surfaces 52. And the method includes a cooling step of the second layer for the formation of a heat exchanger plate 60 bonding the tube bundle 50, followed by a first material removal step 1 to separate the first material 1 from the heat exchanger plate 60 and the tube bundle 50.

[0064] More particularly, this process includes a first step 100 of selecting the first material 1 with a first melting temperature MT1 and a first density, and the second material 2 with a second melting temperature MT2 and a second density, this first material 1 and this second material 2 being both suitable for brazing with the material of the tube bundle 50.

[0065] This first material 1 and this second material 2 are chosen with the second melting temperature MT2 higher than the first melting temperature MT1 and with the second density lower than the first density.

[0066] This first step 100 involves placing the tube bundle 50 onto a brazing tool 90, visible in [Fig. 3], at an ambient temperature TA below 40°C, for example close to 20°C. This brazing tool 90 includes a receptacle 30 with a flat bottom 31 that supports the tube bundle 50 at the end surfaces 52 of the tubes 51.

[0067] More particularly and without limitation, the brazing tool 90 comprises, in addition to this receptacle 30, on the one hand a first reservoir 10 arranged to contain a first quantity of the first material 1 in the solid state at ambient temperature, as seen in [Fig.4], and which is arranged to pour this first material in the liquid state by gravity into the receptacle 30, in particular through a first conduit 11, and on the other hand a second reservoir 20 containing a second quantity of the second material 2 also in the solid state at said ambient temperature as seen in [Fig.4], and which is arranged to pour this second material in the liquid state by gravity into the receptacle 30, in particular through a second conduit 21. The transition from the solid state to the liquid state is obtained by an appropriate temperature rise for each of these two materials.

[0068] Preferably, the receptacle 30 constitutes a mold defining the shape and edge of the exchanger plate 60 which is formed by brazing during the process according to the invention.

[0069] The first step 100 further involves the preparation of a first quantity of the first material 1 intended for the formation of the first sacrificial layer with a thickness equal to the predetermined distance, and of a second quantity of the second material 2 intended for the formation of the second layer for the formation of an exchanger plate 60.

[0070] [Fig.4] illustrates the end of the preparations carried out during the first step 100, with, at room temperature, the two tanks 10 and 20 each containing respectively the first quantity of first material 1 and second quantity of second material 2, and receptacle 30 being empty.

[0071] More specifically, after the first step 100, the process includes a second step 200, illustrated in [Fig. 5], of heating to a temperature greater than or equal to the first melting temperature MT1 and strictly less than the second melting temperature MT2. This second step 200 thus includes the first brazing operation, by pouring the entire first quantity of the first material 1 into the receptacle 30, to form the first layer of the first material 1, in brazing contact with the tube bundle 50, and in contact with the bottom 31 of the receptacle 30.

[0072] More particularly, after the second step 200, the process includes a third step 300, illustrated in [Fig.6], of heating to a temperature greater than or equal to the second melting temperature MT2. This third step 300 includes the second brazing operation by pouring the entire second quantity of the second material 2 into the receptacle 30, resting on the sides of the receptacle, above the first layer formed by the first quantity of the first material 1, in brazing contact with the tube bundle 50 and the first layer of the first material 1, on which the second layer floats due to the difference in density.

[0073] More particularly, after the third step 300, the process includes a fourth step 400, illustrated in [Fig.7], of hardening the second layer of the second material 2 at a hardening temperature HT lower than the second melting temperature MT2 and higher than the first melting temperature MT1 for the formation of the exchanger plate 60. For example, if the first material is a silver alloy, and the second material is a copper alloy, the hardening temperature HT is close to 1000°C: the copper alloy hardens in the solid phase, and the silver alloy remains in the liquid phase.

[0074] More specifically, after the fourth step 400, the process includes a fifth step 500 for removing the first material 1 to separate this first material 1, on the one hand from the heat exchanger plate 60 formed during the fourth step 400, and on the other hand from the tube bundle 50, and to decouple the second material 2 from the first material 1, at an intermediate temperature IT lower than the second melting temperature MT2 and higher than the first melting temperature MT1. The first material 1 is thus fully recoverable and is not incorporated into the final product, which is advantageous in the case of an expensive alloy such as the silver alloy in the example.

[0075] [Fig.8] illustrates a first variant of this fifth step 500 of elimination of the first material 1, carried out by mechanical removal, for example by extraction of the tube bundle 50 and its exchanger plate 46 out of the receptacle 30.

[0076] [Fig.9] illustrates a second variant of this fifth step 500 of elimination of the first material 1, carried out by emptying the first material 1 in liquid state, through an orifice 32 of the receptacle 30, and collecting it in a container 12.

[0077] More particularly, after the fifth step 500, the process includes a sixth step 600 of returning to ambient temperature and solidification of the second material 2 in the exchanger plate 60, to form the exchanger 70 in its final state, as seen in [Fig.9].

[0078] The invention is presented here with the case of brazing the heat exchanger plate onto the tube bundle; it is naturally understood that the principle is usable for brazing other components onto the heat exchanger, if necessary with a third material, or more, having different melting temperature characteristics, for example for brazing such other components at the other end of the heat exchanger, or for forming a second heat exchanger plate at the other end of the tube bundle, or for brazing several tube bundles onto the same heat exchanger.

[0079] The heat exchanger is compatible with a turbogenerator application or any other type of application, and is also compatible with any other application where heat exchange between two or more fluids is required. The described brazing process is compatible with different types of materials.

[0080] The invention thus makes it possible to braze different series of tubes on the same exchanger, using different types of brazing materials.

[0081] The invention further relates, as shown in [Fig. 11], to a motor vehicle 1000 comprising at least one heat exchanger 70 manufactured according to this method. More particularly, this motor vehicle 1000 comprises at least one energy converter in the form of a turbogenerator, itself comprising at least one such heat exchanger 70. More particularly, this motor vehicle 1000 is a PHEV (plug-in electric vehicle) with a series hybrid architecture. The proposed turbogenerator technology is very promising for replacing the internal combustion engine in highly electrified powertrains, particularly for such PHEVs with a series hybrid architecture, and combines the advantages of low emissions, low noise, no vibrations, very low maintenance, the ability to operate on several types of fuel, and high efficiency.

[0082] The invention finds advantageous application on a regenerative gas turbine (RGT) type energy converter. "), or gas turbine cycle (with cooled compression, regenerator and reheat during expansion IRReGT (from the English "intercooled recuperative reheat gas turbine"), or any other thermodynamic cycle including a heat exchanger (a recuperator).

[0083] The innovation also targets any type of application where a need for an exchanger is required.

[0084] The brazing process according to the invention for the manufacture of an exchanger is also usable in other technical fields than the automotive field.

[0085] The technology proposed by the invention makes it possible to overcome the problems encountered on exchangers, and which were identified during tests on several types of exchangers.

[0086] The industrial process for brazing the heat recovery unit according to the invention makes it possible to produce the exchanger at a low cost.

[0087] In summary, the invention provides various technical advantages: improvement of the manufacturing process of the exchanger, reduction of production time, the possibility of offering a modular and adaptable design depending on the application, the possibility of modifying the type of material according to the sections / parts of the exchanger (therefore according to the maximum temperature reached), the possibility of modifying the number of passage sections (tubes) in each stage of the exchanger and consequently modifying the type of brazing, and the possibility of modifying the materials in each passage section to be compatible with the brazing material.

Claims

1.

2. Demands A method for producing a heat exchanger (70) by brazing from a tube bundle (50) comprising tubes (51) with end surfaces (52), characterized in that said method comprises a first brazing operation of a first material (1) on said tube bundle (50) for the formation of a first sacrificial layer of said first material (1), in that said method comprises a second brazing operation of a second material (2) on said tube bundle (50) and on said first layer for the formation of a second layer of said second material (2) at a predetermined and non-zero distance from said end surfaces (52), and in that said method comprises a cooling step of said second layer for the formation of a heat exchanger plate (60) bonding said tube bundle (50),followed by a step of removing said first material (1) to separate said first material (1) from said heat exchanger plate (60) and said tube bundle (50). A method for producing a heat exchanger (70) according to claim 1 by brazing, characterized in that said method comprises a first step (100) of selecting said first material (1) with a first melting temperature (MT1) and a first density, and said second material (2) with a second melting temperature (MT2) and a second density, with said second melting temperature (MT2) higher than said first melting temperature (MT1) and with said second density lower than said first density, said first step (100) comprising placing said tube bundle (50) at an ambient temperature (TA) below 40°C on a brazing tool (90) comprising a receptacle (30) having a flat bottom (31) receiving said tube bundle (50) in support at said end surfaces (52),and the preparation of a first quantity of said first material intended for the formation of said first sacrificial layer with a thickness equal to said predetermined distance, and of a second quantity of said second material intended for the formation of said second layer for the formation of a heat exchanger plate (60).

3. A method for producing an exchanger (70) according to claim 2 by brazing, characterized in that said method comprises, after said first step (100), a second step (200) of heating to a temperature greater than or equal to said first melting temperature (MT1) and strictly less than said second melting temperature (MT2), said second step (200) comprising said first brazing operation by pouring all of said first quantity of said first material (1) into said receptacle (30) in brazing contact with said tube bundle (50).

4. A method for producing an exchanger (70) according to claim 3 by brazing, characterized in that said method comprises, after said second step (200), a third step (300) of heating to a temperature greater than or equal to said second melting temperature (MT2), said third step (300) comprising said second brazing operation by pouring all of said second quantity of said second material (2) into said receptacle (30) above said first quantity of said first material (1) in brazing contact with said tube bundle (50) and said first layer of said first material (1).

5. A method for producing a heat exchanger (70) according to claim 4 by brazing, characterized in that said method comprises, after said third step (300), a fourth step (400) of hardening said second layer of said second material (2) at a hardening temperature (HT) lower than said second melting temperature (MT2) and higher than said first melting temperature (MT1) for the formation of said heat exchanger plate (60).

6. A method for producing a heat exchanger (70) according to claim 5 by brazing, characterized in that said method comprises, after said fourth step (400), a fifth step (500) of removing said first material (1) to separate said first material (1) from said heat exchanger plate (60) and said tube bundle (50) and to decouple said second material (2) from said first material (1) at an intermediate temperature (IT) below said second melting temperature (MT2) and above said first melting temperature (MT1), by mechanical removal and / or by draining said first liquid material (1).

7. A method for producing a heat exchanger (70) by brazing according to claim 6, characterized in that said method comprises, after said fifth step (500), a sixth step (600) of returning to said ambient temperature and solidifying said second material (2) in said heat exchanger plate (60).

8. Brazing tooling (90) for carrying out the process according to any one of claims 1 to 7, characterized in that said brazing tooling (90) comprises a receptacle (30) having a flat bottom (31) supporting said tube bundle (50) at the end surfaces (52) of said tubes (51) of said tube bundle (50), and comprises, on the one hand, a first reservoir (10) arranged to contain a first quantity of said first material (1) in solid form at said ambient temperature, and which is arranged to discharge it in liquid form by gravity into said receptacle (30) through a first conduit (11), and on the other hand, a second reservoir (20) containing a second quantity of said second material (2) in solid form at said ambient temperature, and which is arranged to discharge it in liquid form by gravity into said receptacle (30) through a second conduit (21).

9. Brazing tooling (90) according to claim 8, characterized in that said receptacle (30) constitutes a mold defining the shape and edge of said exchanger plate (60).

10. Motor vehicle (1000) comprising at least one heat exchanger (70) made according to the method according to any one of claims 1 to 7.

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