Heat pipe heat exchanger for turbomachinery in a motor vehicle

Abstract

A heat exchanger for a turbomachine, configured to heat a first fluid from a second fluid, comprising a shell delimiting an internal volume with a first internal circulation space configured to convey the first fluid, a second internal circulation space configured to convey the second fluid, the heat exchanger comprising a plurality of tubes, the first internal circulation space comprising an inner area of ​​the plurality of tubes (2), characterized in that the tubes are each surrounded by a heat exchange sleeve, the second internal circulation space comprising an outer area of ​​the heat exchange sleeves. Figure 5

Description

Title of the invention: HEAT PIPE HEAT EXCHANGER FOR TURBOMACHINE IN A MOTOR VEHICLE

[0001] This disclosure generally relates to the field of gas turbine cycle type turbogenerator devices and systems, otherwise known as "turbomachines." Here, we are in the context of a motor vehicle, where the turbomachine is involved in a range extender system for an electric or hybrid vehicle.

[0002] The present invention generally relates to a heat exchanger architecture for such turbomachinery. More particularly, the invention relates to a heat exchanger known as a recuperative heat exchanger, which allows intake air to be heated by means of hot exhaust gases.

[0003] This recuperative exchanger makes it possible to improve the overall efficiency of the turbomachine, particularly but not exclusively, in the case of a two-stage compression turbomachine.

[0004] Furthermore, during the start-up phase of the turbomachine, the efficiency of the turbomachine is degraded, until the temperatures have reached their nominal operating values.

[0005] The inventors sought to improve the efficiency of the turbomachine, both for the start-up phase and for the established operating regime of the turbomachine.

[0006] To achieve this objective, the invention proposes a heat exchanger for turbomachinery, configured to heat a first fluid from a second fluid, comprising a shell delimiting an internal volume with a first internal circulation space configured to convey the first fluid, a second internal circulation space configured to convey the second fluid, the heat exchanger comprising a plurality of tubes, the first internal circulation space comprising an internal area of ​​the plurality of tubes, characterized in that the tubes are each surrounded by a heat exchange sleeve, the second internal circulation space comprising an external area of ​​the heat exchange sleeves.

[0007] Each heat exchange sleeve forms a local heat pipe function and promotes heat exchange between the second fluid and the first fluid.

[0008] Thanks to these arrangements, the heat exchange sleeves improve the heat transfer coefficient and increase the performance of the heat exchanger.

[0009] It is noted that each sleeve surrounding a tube shares a common axis with said tube, in other words each tube and its associated sleeve are coaxial.

[0010] According to an advantageous option, an internal space in the heat exchange sleeve is provided to hermetically contain a quantity of heat transfer fluid, the heat transfer fluid being two-phase under nominal operating conditions, over a temperature range of the tubes between an inlet of the first fluid and an outlet of the first fluid.

[0011] The temperature range in question can go from 100°C up to 700°C.

[0012] The heat transfer fluid undergoes vaporization in the hottest portion of the sleeve and liquefaction / condensation in the cooler portion of the sleeve. This phase change allows for the transport of a greater quantity of heat energy than in the case of conventional convection.

[0013] The return of the liquid to the hottest portion of the sleeve can be achieved by gravity, in which case we have a thermosiphon principle, or by capillary pumping. When the thermosiphon principle is used, a lower portion of the heat exchange sleeve is filled with liquid and an upper portion of the heat exchange sleeve is filled with vapor.

[0014] According to one embodiment, the second fluid bathes a lower portion of the heat exchange sleeve, and does not lick an upper portion of the heat exchange sleeve.

[0015] We thus have a temperature differential between the lower portion of the sleeve and the upper portion of the sleeve which generates the phase changes beneficial to heat exchanges.

[0016] According to one embodiment, the tubes are organized in superimposed layers and for each layer a layer separation wall and an intermediate separation wall can be provided to confine the second fluid to contact with a lower portion of the heat exchange sleeve.

[0017] The layer separation walls separate the different layers, a layer separation wall separates in particular two adjacent tube layers.

[0018] According to one embodiment, the heat exchange sleeve includes a porous material forming a capillary trap to retain the heat transfer fluid in a part bathed by the second fluid.

[0019] It is noted that the tubes and sleeves are all aligned along an axis corresponding substantially to the longitudinal axis of the vehicle.

[0020] Thanks to the presence of the porous material, in the event of a slope of the ground or in the case of longitudinal acceleration of the vehicle, it is prevented from the liquid being poorly distributed with a lot of liquid either at the front or at the rear of the sleeve and no liquid at all on the opposite side.

[0021] According to one embodiment, the second internal space comprises a cellular or mesh material having an average void ratio of between 25% and 85%, preferably with an average void ratio of between 40% and 75%. The cellular or mesh material is preferably located near the lower portion of the sleeve.

[0022] The cellular or mesh material has significant porosity and acts as a thermal sponge. The material stores energy in the form of heat while the second fluid circulates in the second internal circulation space. In practice, the gas temperature rises more rapidly during a turbomachine restart because the cellular or mesh material has retained heat from the previous cycle, which it can release into the new cycle about to start. The transient effects of such a restart are shorter, and the temperatures reach their nominal operating values ​​more quickly compared to the case of the first start-up, or their nominal values ​​compared to the known art.

[0023] Because of its function, the alveolar or mesh material can also be called a "thermal sponge effect material".

[0024] It should be noted that the thermal sponge material can occupy all or part of the second interior space. Only the second fluid bathes the thermal sponge material, but not the first fluid.

[0025] Moreover, advantageously, the alveolar or mesh material acts as a sound damper, which reduces the noise generated at the exhaust of the second fluid of the turbomachine system.

[0026] However, thanks to the high void ratio, the presence of a material with a thermal sponge effect does not significantly degrade the flow of gases to the outside and does not cause a significant loss of aerodynamic pressure in the path of the second fluid to the outside.

[0027] It is noted that the addition of the thermal sponge effect material is considered for a turbomachine with a single compression stage as well as for a turbomachine with two or more compression stages.

[0028] In this document, the term "average void ratio" represents the proportion of space not occupied by the material. In other words, the "average void ratio" is complementary to an average fill ratio. The sum of the "average void ratio" and the average fill ratio equals 1. The concept of average is assessed over a volume where the material configuration is similar, for example, 5 to 10 mm³.

[0029] According to an advantageous option, the cellular or mesh material is a metallic material. It withstands very high temperatures, for example up to 800°C, without melting, deteriorating, or degrading over the long term.

[0030] According to one embodiment, the cellular or mesh material is steel wool or iron wool. This material is available as a semi-finished product and therefore the cost price of this solution is competitive.

[0031] According to one embodiment, the heat exchanger is of the counter-current type. This maximizes the heat transfer between the second fluid and the first fluid.

[0032] According to one embodiment, the first fluid enters at a temperature between 100°C and 200°C, the first fluid exits at a temperature between 600°C and 700°C, the second fluid enters at a temperature between 750°C and 820°C, and the second fluid exits at a temperature between 200°C and 300°C. Consequently, the thermal sponge material operates over a wide temperature range, exhibiting a temperature gradient of several hundred degrees along the fluid path.

[0033] According to one embodiment, the tubes are arranged parallel to each other, either as a single group or as several groups arranged in cascade, that is to say, in series. For example, there may be four groups of tubes, each group forming a cascaded stage relative to the other groups.

[0034] According to one embodiment, the flows are generally perpendicular.

[0035] Indeed, in the heat exchange zones, at the level of the tubes, the path of the first fluid is substantially perpendicular to the path of the second fluid.

[0036] According to one embodiment, the first fluid is provided with: a first inlet orifice for the first fluid, an upstream collector zone serving all or part of the plurality of tubes, a downstream collector zone, and a first outlet orifice.

[0037] The first internal circulation space may include one or more distribution spaces at the ends of the tubes, allowing the first fluid to be directed from the interior of one subset of tubes to the interior of another subset of tubes. The distribution spaces are located between the upstream collector zone and the downstream collector zone along the path of the first fluid.

[0038] According to one embodiment, a second inlet port for the second fluid and transfer ports, a second outlet port are provided for the second fluid.

[0039] The present invention also relates to a turbomachine system configured to provide electrical power in a motor vehicle, as a range extender, comprising a heat exchanger as defined above.

[0040] According to one option, the turbomachine system comprises two or more compression stages.

[0041] The present invention also relates to a motor vehicle comprising a turbomachine system as defined above.

[0042] 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 a turbomachine system for a motor vehicle; - [Fig.2] schematically illustrates an example of a heat exchanger, seen in perspective ; - [Fig.3] schematically illustrates an example of a heat exchanger, in front view in cross-section, with only about fifteen tubes represented per heat exchange zone, the others not being represented; - [Fig.4] schematically illustrates an example of a heat exchanger, in top view cross-section, with only a few tubes represented per heat exchange zone; - [Fig.5] illustrates a first example of a configuration with heat exchange tubes and sleeves; - [Fig.6] illustrates in more detail the first example of configuration with the heat exchange tubes and sleeves; - [Fig.7] illustrates in more detail a second example of configuration with heat exchange tubes and sleeves, as well as a thermal sponge-like material; - [Fig.8] illustrates a cross-sectional view of a tube with its heat exchange sleeve.

[0043] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale.

[0044] Gas turbine-type energy converters are currently being studied as range extenders in electric or hybrid vehicles. They are also more simply called "turbomachines".

[0045] This type of converter can operate in APU (Auxiliary Power Unit) mode, where its role is to recharge the batteries of an electric vehicle. It is thus mechanically decoupled from the powertrain and operates at its maximum efficiency point.

[0046] Several cycles are studied, including simple regenerative cycles (RGT for Regenerative Gas Turbine), but also regenerative cycles with a cooler (IRGT) and cycles with a cooler, recuperator and reheat or "Intercooled Regenerative Reheat Gas Turbine" in English).

[0047] The gas turbine cycle with cooler, recuperator and reheater (IRReGT) is a cycle with high potential for automotive applications. This cycle makes it possible to achieve high efficiency as well as high power density (high specific net work).

[0048] This technology has the following advantages: low emission levels, low emission noise levels, ability to operate with several types of fuels.

[0049] Heat exchangers exist on the market and several types are offered: a tube and fin exchanger, a plate and fin exchanger, a plate exchanger, and a 3D printed metallic microchannel exchanger.

[0050] Figure 1 shows a system diagram of a turbomachine of interest according to the present invention.

[0051] A first stage called low pressure comprises a low pressure compressor CLP and a low pressure turbine TLP, these two entities being linked together via a first shaft AL. This first shaft Al drives a first electric machine MGLP, which is used essentially as a generator and secondarily as a motor for the start-up phase of the first stage.

[0052] A second stage, referred to as the high-pressure stage, comprises a high-pressure compressor CHP and a high-pressure turbine THP, these two entities being linked together via a second shaft A2. This second shaft A2 drives a second electrical machine MGHP, which is used primarily as a generator and secondarily as a motor for the start-up phase of the second stage.

[0053] In addition, an AF air filter is located upstream of the low-pressure compressor. Furthermore, a cooling heat exchanger IC cools the air taken from the outlet of the low-pressure compressor and supplied to the inlet of the high-pressure compressor.

[0054] A first CCLP combustion chamber supplies hot gases to the low-pressure turbine TLP. The first CCLP combustion chamber is supplied with air by the high-pressure turbine outlet THP.

[0055] A second CCHP combustion chamber supplies hot gases to the high-pressure turbine THP1. The second CCHP combustion chamber is supplied with air by the high-pressure compressor CHP via a heat exchanger which is the main object of the present invention.

[0056] The first combustion chamber and the second combustion chamber are each supplied with a hydrocarbon fuel. The hydrocarbon fuel is, for example, methanol or ethanol.

[0057] The air exiting the high-pressure compressor CHP passes through a heat exchanger designated 1, before reaching the second combustion chamber CCHP to supply air to said second combustion chamber CCHP. This airflow forms the first fluid Fl which will be discussed in relation to the heat exchanger described in detail below.

[0058] Furthermore, the heat exchanger 1 receives as a second fluid F2 air from the outlet of the low pressure turbine TLP via the pipe 18.

[0059] As can be seen in figures 2 to 5, the heat exchanger 1 includes a shell 6 delimiting an internal volume denoted E0.

[0060] A coordinate system XYZ is defined for the heat exchanger. The X direction corresponds to the longitudinal direction of the vehicle. The Y direction corresponds to the transverse direction of the vehicle. The Z direction can be substantially vertical.

[0061] In the example shown, the heat exchanger 1 is the largest component of the turbomachinery system. The heat exchanger 1 has a generally parallelepiped shape, which facilitates good integration into the vehicle architecture, particularly in the lower part of the chassis. The longest dimension LY extends along the transverse direction Y. In one example, the length LY extends across almost the entire width of the vehicle, for example, at least 100 cm. The dimensions LX and LZ can typically be between 10 cm and 20 cm.

[0062] The envelope 6 comprises a front wall 10, a back wall 15, a bottom wall 13, a top wall 11, a left side wall 12 and a right side wall 14. These walls delimit the internal volume E0, in a hermetically sealed manner, except for the fluid inlets and outlets provided for this purpose.

[0063] Arranged on the front wall 10 of the heat exchanger 1 are: the inlet of the first fluid EF1, the outlet of the first fluid SF1, and the inlet of the second fluid EF2.

[0064] The outlet of the second fluid SF2 is located on one or both side walls. Curved return outlets may be provided on the sides of the front face, so that all fluid inlets and outlets are located on the same side of the heat exchanger 1, for optimal integration into the vehicle architecture.

[0065] Inside the exchanger, there is provided a first heat exchange zone Z1, a second heat exchange zone Z2, a third heat exchange zone Z3 and a fourth heat exchange zone Z4.

[0066] The order of the heat exchange zones follows the path of the second fluid F2, namely the hot gases exiting the exhaust of the first stage, i.e., the low-pressure stage, via the low-pressure turbine TLP and then through pipe 18

[0067] By contrast, the path of the first fluid passes first through the fourth heat exchange zone Z4, then the third heat exchange zone Z3, then the second heat exchange zone Z2 and finally the first heat exchange zone Zl.

[0068] Therefore, the heat exchanger considered here is a so-called counter-current exchanger or a so-called cross-flow exchanger.

[0069] The path of the first fluid Fl zigzags as illustrated by the arrowed path PI in dashed line shown in [Fig.4].

[0070] Inside the heat exchange zones, the first fluid circulates in tubes 2. Here the tubes 2 are of round cross-section but they could have another cross-sectional shape.

[0071] The tubes 2 are arranged parallel to each other. The axes of the tubes are parallel to the longitudinal direction X.

[0072] More specifically, the heat exchanger 1 comprises a plurality of tubes, the first internal circulation space El is defined which comprises the internal area of ​​the plurality of tubes 2.

[0073] The number of tubes can range from 1000 tubes to 3000 tubes.

[0074] The tubes 2 are formed of copper, aluminum or alloy resistant to temperatures of 800°C.

[0075] The inner diameter of the tubes 2 is between 1 millimeter and 3 millimeters.

[0076] According to the illustrated example, we have here four cascaded stages for the path of the fluid FL. Of course, the number of cascaded stages could be different: less than four or even more than four.

[0077] A first group of tubes is arranged in the first heat exchange zone ZL. A second group of tubes is arranged in the second heat exchange zone Z2. A third group of tubes is arranged in the third heat exchange zone Z3. A fourth group of tubes is arranged in the fourth heat exchange zone Z4.

[0078] Partitions are provided to delimit the distinct heat exchange zones.

[0079] A first partition 51 comprises four faces (as seen in [Fig. 3]) and delimits the first heat exchange zone ZL. A second partition 52 also comprises four faces and delimits the second heat exchange zone Z2, with the first partition 51. A third partition 53 also comprises four faces and delimits the third heat exchange zone Z3 with the second partition 52.

[0080] In these partitions are arranged lights 8 which allow the second fluid F2 to flow from one heat exchange zone to the next (from Z1 to Z2, from Z2 to Z3 and from Z3 to Z4).

[0081] The internal volume 6 includes a first internal circulation space denoted El configured to convey the first fluid Fl, and a second internal circulation space denoted E2 configured to convey the second fluid F2.

[0082] For the first fluid Fl, a first inlet port EF1, an upstream collector zone 42 serving all or part of the plurality of tubes, a downstream collector zone 41, and a first outlet port SF1 are provided.

[0083] Along the PI path of the first fluid Fl, between the upstream collector zone and the downstream collector zone, one or more distribution spaces at the ends of the tubes, as illustrated in the example shown in the figures, can be found, allowing the first fluid to be directed from the interior of one subset of tubes to the interior of another subset of tubes. The distribution spaces act as plenums that collect the output of one group of tubes and distribute the first fluid to another group of tubes.

[0084] A first distribution space D34 connects the tubes of the fourth heat exchange zone Z4 with the tubes of the third heat exchange zone Z3. A second distribution space D23 connects the tubes of the third heat exchange zone Z3 with the tubes of the second heat exchange zone Z2.

[0085] A third distribution space D12 connects the tubes of the second heat exchange zone Z2 with the tubes of the first heat exchange zone ZI.

[0086] In the illustrated architecture for the changer exchanger, a front perforated plate 71 and a rear perforated plate 72 are provided.

[0087] The front and rear perforated plates support and hold the tubes 2 and act as a sealed separation between the heat exchange areas and the distribution spaces.

[0088] It is noted that the second fluid does not circulate in the distribution spaces, the second fluid F2 only circulates in the heat exchange zones and passes from one to the other through the lights 8.

[0089] The second internal circulation space, denoted E2, comprises the external area of ​​the plurality of tubes, for their part located in the heat exchange zones Z1 to Z4.

[0090] Advantageously, according to the invention, each tube 2 is surrounded by a heat exchange sleeve 5, or simply referred to as a 'sleeve' hereafter. Each heat exchange sleeve extends along an axis Al which coincides with the axis Al of the tube 2 that it surrounds.

[0091] Here the sleeve 5 is cylindrical of revolution. The tube and the sleeve together define an annular space E9 whose inner diameter corresponds to the diameter external DI of the tube and whose external diameter corresponds to the internal diameter of the sleeve 5. The external diameter of the sleeve is noted D2.

[0092] The second fluid F2 circulates around the sleeves. The second internal circulation space E2 conveying the second fluid F2 includes an external zone of the heat exchange sleeves 5.

[0093] The annular space E9 forms a space which hermetically encloses a quantity of heat transfer fluid 9. The heat transfer fluid is chosen to be a fluid which is two-phase under nominal operating conditions, over a temperature range of the tubes between an inlet of the first fluid and an outlet of the first fluid.

[0094] For example, water or mercury can be chosen as the heat transfer fluid 9.

[0095] The annular space E9 has a thickness between 1 and 2 mm.

[0096] As illustrated in [Fig. 8], the sleeve 5 comprises a cylindrical body 50 and two discoidal end walls 51, 52. Furthermore, the annular space E9 is delimited by the tube 2 itself. A first discoidal end wall 51 hermetically seals the annular space E9 at one axial end. A second discoidal end wall 52 hermetically seals the annular space E9 at the other axial end.

[0097] Annular welds 54 can be provided between the two discoid end walls and the tube.

[0098] The heat transfer fluid 9 undergoes vaporization in the hottest portion of the sleeve (here the lower portion 42) and liquefaction in the least hot portion of the sleeve (here the upper portion 43).

[0099] As illustrated in [Fig.6], vaporization generates a vapor flow 45 towards the upper portion 43, whereas conversely, liquefaction generates a liquid flow 46 towards the lower portion 42.

[0100] Thanks to the heat capacity of the material, the phase change makes it possible to transport a greater quantity of heat energy than in the case of conventional convection.

[0101] Thus, each heat exchange sleeve 5 forms a local heat pipe and promotes heat exchange between the second fluid and the first fluid.

[0102] In the illustrated example, the return of the liquid to the hottest portion of the sleeve is done by gravity according to the thermosiphon principle.

[0103] In an unshown variant, the return of the liquid to the hottest portion of the sleeve can be done by a capillary pumping principle using a porous material forming a capillary wick.

[0104] The tubes 2 and sleeves 5 are arranged in superimposed layers. A layer separation wall 40 is provided for each layer.

[0105] Furthermore, an intermediate separation wall 41 allows the second fluid F2 to be confined to the contact of a lower portion of the heat exchange sleeve 5.

[0106] The second fluid F2 bathes the sleeve 5 over a height Hl.

[0107] Said height Hl is approximately between one third and one half of H2 separating two neighbouring strata.

[0108] According to an example of a turbomachine for range extender application, the inlet of the first fluid occurs at a temperature between 100°C and 200°C, the outlet of the first fluid Fl occurs, after heating by the second fluid F2, at a temperature between 600°C and 700°C.

[0109] According to this same example, the entry of the second fluid occurs at a temperature between 750°C and 820°C, the exit of the second fluid occurs at a temperature between 200°C and 300°C.

[0110] It is noted that the flows are generally perpendicular, more precisely in each heat exchange zone, the path PI of the first fluid Fl and substantially perpendicular to the path P2 of the second fluid F2.

[0111] According to one option, the second interior space is not empty but contains a cellular or mesh material generically denoted by the marker 3, also called a thermal sponge effect material.

[0112] Generally, the thermal sponge material is in contact with the tubes, which promotes a good heat exchange coefficient between the thermal sponge material and the first fluid via the tube material.

[0113] According to one illustrated option, the thermal sponge material 3 is a metallic material. According to one illustrated option, the thermal sponge material 3 may be steel wool or iron straw. The steel wool or iron straw may be made of stainless steel wire or Inconel alloy (registered trademark). Advantageously, this material has high thermal capacity.

[0114] This material stores thermal energy in the form of calories. The thermal sponge material has an average void ratio of between 25% and 85%. A high average void ratio of between 40% and 75%, for example around 60 to 70%, prevents substantial air pressure loss.

[0115] It is not necessary for the thermal sponge effect material 3 to fill all the interstitial space between the tubes.

[0116] According to a particular option, when the tubes have their axes oriented horizontally, the heat exchange sleeve includes in the lower part a porous material forming a capillary trap to retain the heat transfer fluid in a part bathed by the second fluid F2.

[0117] Thanks to the presence of the porous material, in the event of a slope of ground (garage or driving on a slope for example), it is prevented from the liquid being poorly distributed with a lot of liquid either at the front or at the rear of the sleeve and no liquid at all on the opposite side.

[0118] Similarly, in dynamics, in cases of longitudinal or lateral acceleration of the vehicle, the porous material forming a capillary trap prevents the liquid from ending up at one axial end of the sleeve, with, conversely, a lack of liquid at the opposite end.

[0119] The first fluid Fl is air in the illustrated example, but the first fluid could be any gas or any mixture of gases. Similarly, the second fluid F2 is air in the illustrated example, but it could be any gas or any mixture of gases, hence the generic term "fluid" in this document.

[0120] It is noted that in the illustrated turbomachine, the first stage is started a few moments before the second stage, i.e., the high-pressure stage, is started, so that the second fluid is preheated before the second stage starts. The fluid exiting the low-pressure compressor is already hot and heats the first fluid via the heat exchanger, so that the start-up of the high-pressure stage is already closer to nominal operating conditions.

[0121] Thanks to the present invention concerning the heat exchanger and its improved efficiency, the optimal nominal operating conditions of the turbomachine are reached more quickly after its start-up and its performance is very satisfactory.

Claims

Demands

1. Heat exchanger (1) for turbomachinery, configured to heat a first fluid (Fl) from a second fluid (F2), comprising a shell (6) delimiting an internal volume (EO) with a first internal circulation space (E1) configured to convey the first fluid (Fl), a second internal circulation space (E2) configured to convey the second fluid (F2), the heat exchanger comprising a plurality of tubes, the first internal circulation space comprising an internal area of ​​the plurality of tubes (2), characterized in that the tubes are each surrounded by a heat exchange sleeve (5), the second internal circulation space comprising an external area of ​​the heat exchange sleeves, the tube and the sleeve (5) together delimiting an annular space (E9) whose internal diameter corresponds to the external diameter of the tube and whose external diameter corresponds to the internal diameter of the sleeve (5),this annular space (E9) hermetically enclosing a quantity of heat transfer fluid (9), the heat transfer fluid being two-phase under nominal operating conditions, over a temperature range of the tubes between an inlet of the first fluid and an outlet of the first fluid, the second fluid (F2) circulating around the sleeves and the first fluid (Fl) circulating in the tubes.

2. Heat exchanger according to claim 1, characterized in that the second fluid bathes a lower portion (42) of the heat exchange sleeve, and does not lick an upper portion (43) of the heat exchange sleeve.

3. Heat exchanger according to claim 1 or 2, characterized in that the heat exchange sleeve comprises a porous material forming a capillary trap to retain the heat transfer fluid in a part bathed by the second fluid.

4. Heat exchanger according to any one of claims 1 to 3, characterized in that the second internal space comprises a cellular or mesh material (3) having an average void ratio of between 25% and 85%, preferably with an average void ratio of between 40% and 75%.

5. Heat exchanger according to any one of claims 1 to 3, characterized in that the heat exchanger is of the counter-current type.

6. Heat exchanger according to any one of claims 1 to 4, characterized in that the inlet of the first fluid occurs at a temperature between 100°C and 200°C, the outlet of the first fluid occurs at a temperature between 600°C and 700°C, the inlet of the second fluid occurs at a temperature between 750°C and 820°C, the outlet of the second fluid occurs at a temperature between 200°C and 300°C.

7. Heat exchanger according to any one of claims 1 to 5, characterized in that it is provided for the first fluid: a first inlet port (EF1) of the first fluid, an upstream collector zone serving all or part of the plurality of tubes, a downstream collector zone, and a first outlet port (SF1) and in that it is provided for the second fluid: a second inlet port (EF2) of the second fluid and transfer ports, a second outlet port (SF2).

8. Turbomachine system (8) configured to provide electrical power in a motor vehicle, as a range extender, comprising a heat exchanger according to any one of claims 1 to 7.

9. Motor vehicle comprising a turbomachine system according to claim 8.