HEAT EXCHANGER COMPRISING SECTIONS OF VARIABLE SIZES, PARTICULARLY FOR A TURBOMACHINE IN A MOTOR VEHICLE

Abstract

The invention relates to a heat exchanger comprising: - first heat exchange sections (TP, S1) upstream of a first fluid passage circuit (F2), the first sections (TP, S1) comprising first circulation tubes of a second fluid; and - second heat exchange sections (TP, S2) downstream of said first sections (TP, S1) of said first fluid passage circuit (F2), the second sections (TP, S2) comprising second circulation tubes of said second fluid, characterized in that the size of said first heat exchange sections (S1) is different from the size of said second heat exchange sections (S2), and in that it comprises a counter-current heat exchange architecture. The invention also relates to a vehicle and a method based on such a heat exchanger. Figure 2

Description

Title of the invention: HEAT EXCHANGER COMPRISING SECTIONS OF VARIABLE SIZES, IN PARTICULAR FOR A TURBOMACHINE OF A MOTOR VEHICLE

[0001] The invention relates to the field of gas turbine cycle type turbogenerator devices and systems for motor vehicles. The invention relates more generally to a heat exchanger architecture for such turbogenerators.

[0002] Gas turbine type energy converters are currently being widely studied as range extenders in series hybrid vehicles.

[0003] This converter can operate in APU mode (for Auxiliary Power Unit) where its role is to recharge the batteries of an electric vehicle. It is thus mechanically decoupled from the drivetrain and operates at its maximum efficiency point.

[0004] Several cycles are under investigation, including simple recuperative cycles (RGT for recuperative gas turbine or "Recuperative Gas Turbine"), but also recuperative cycles with cooler (IRGT) and cycles with cooler, recuperator and reheater or "Intercooled Recuperative Reheat Gas Turbine" in English).

[0005] The refrigerated, recuperated and reheated gas turbine (IRReGT) cycle is a cycle with high potential for automotive applications. This cycle allows for high efficiency and high power density (high net specific work).

[0006] This technology promises the following advantages: - Low level of emissions; - Low noise level of emissions; - No emission vibrations; - No maintenance (apart from changing the air filter); - Ability to operate with multiple fuel types.

[0007] 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 metal micro-channel exchanger.

[0008] The interest of this invention application lies in the fact that a modular, high-performance design is proposed, while reducing the integration complexities. The problems encountered with heat exchangers are as follows:

[0009] Unfortunately, the architectures of the prior art are not easily integrated into a motor vehicle.

[0010] In addition, the 3D printed micro-channel exchanger involves complex, time-consuming technology and cannot be industrialized on a large scale.

[0011] In addition, the plate exchanger with external collectors requires specific insulation to reduce heat losses. This exchanger also requires specific brazing at the plates and collectors.

[0012] Thus, one objective of the invention is to overcome the defects of the prior art, in particular to propose a solution that is easily integrated into a motor vehicle and has good energy efficiency.

[0013] To achieve this objective, the invention proposes a heat exchanger comprising: - first heat exchange sections upstream of a circuit for passing a first fluid, the first sections comprising first tubes for circulating a second fluid; and - second heat exchange sections downstream of said first sections of said first fluid passage circuit, the second sections comprising second circulation tubes of said second fluid, characterized in that the size of said first heat exchange sections is different from the size of said second heat exchange sections, and in that it comprises a counter-current heat exchange architecture.

[0014] Indeed, to reduce the pressure drop, it is better to have larger passage and heat exchange sections (of increasing size). However, a larger section implies more volume and less exchange coefficient. Thus, this implies a loss of efficiency. In other words, an efficient exchanger has more pressure drop. To overcome this, the invention proposes variable sections to have a good compromise between efficiency, pressure drop and total volume.

[0015] In particular, the invention is valid for any turbomachine comprising at least one heat recovery unit (RGT, RReGT, IRGT, IRReGT, etc.). This proposed invention is also valid for any type of application requiring the use of a heat exchanger.

[0016] Advantageously, the invention makes it possible to have an exchanger with a low pressure drop due to the variation in sizes, which is a very important criterion, particularly in the case of a turbogenerator application. In this case, the flow passes through the heat exchanger twice (once at the compressor outlet and once at the turbine outlet). In addition, this makes it possible to increase the expansion rate of the turbine and consequently, to increase the power generated by the turbine and therefore the net mechanical and electrical power.

[0017] In addition, a heat exchanger with a counter-current heat exchange architecture makes it possible to improve the efficiency of the recuperator.

[0018] According to a variant, the heat exchanger further comprises third heat exchange sections downstream of said second sections of said circuit for passing the first fluid, said third sections comprising third tubes for circulating said second fluid, characterized in that the size of said third heat exchange sections is different from the size of said first and / or second heat exchange sections.

[0019] This allows for greater modulation between efficiency and pressure drop.

[0020] According to a variant, the number and / or the section of the first circulation tubes is different from those of the second and / or third circulation tubes. This makes it possible to modulate between efficiency and pressure loss within each section.

[0021] According to a variant, the heat exchanger comprises a hot inlet upstream of the first heat exchange sections, the walls of the hot inlet are arranged inside the heat exchanger, so as to limit the contact between the walls of the hot inlet and the outside.

[0022] This makes it possible to limit heat losses at the walls towards the outside of the heat exchanger.

[0023] According to one variant, the heat exchanger comprises at least one inlet and at least one outlet, and the heat exchanger has a modular architecture so that said inlet and said outlet can be arranged at different locations in the functional volume of the heat exchanger.

[0024] This allows the inlets / outlets to be arranged at any location within the functional volume of the exchanger, or to change them according to said functional volume of the exchanger. Thus, the exchanger is adaptable to different motor vehicle configurations. The exchanger is also adaptable to other applications outside the automotive field.

[0025] According to a variant, the heat exchanger has a composite structure comprising aluminum in a hot gas section, copper in a heat transfer section of less than 600°C, and metal or steel alloys in a thermal stress section of more than 650°C.

[0026] This makes it possible to adapt the type of materials to increase the heat exchange performance and minimize the mass of the exchanger.

[0027] According to one variant, the heat exchanger is single-flow or double-flow.

[0028] According to one variant, the heat exchanger can be connected to at least three different fluid circuits.

[0029] Advantageously, in the context of a turbogenerator, having an exchange with a third (or even a fourth) working fluid makes it possible to recover the energy remaining in the flow of hot fluid, and to increase the overall efficiency of thermal recovery. More generally, this makes it possible to ensure thermal exchanges with other fluids and to recover a maximum of energy.

[0030] According to one variant, the heat exchanger is connectable to a fuel circuit comprising a tank.

[0031] This makes it possible to preheat the fuel and vaporize it before entering the combustion chamber of the turbogenerator in the case of a liquid fuel such as gasoline or diesel or ethanol.

[0032] According to one variant, the heat exchanger can be connected to an organic Rankine cycle machine.

[0033] This makes it possible to transform part of the recovered energy into mechanical or electrical work and consequently to increase the overall efficiency of the system.

[0034] Another subject of the invention relates to a motor vehicle comprising at least one turbomachine equipped with at least one heat exchanger according to the invention.

[0035] The invention further relates to a method of manufacturing a heat exchanger for a motor vehicle according to the invention, characterized in that it comprises the following steps: - making said first heat exchange sections of a different size from said second heat exchange sections, and - create a counter-current heat exchange architecture.

[0036] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates a view in space of a recuperator of a turbogenerator for a vehicle according to a preferred embodiment of the invention; - [Fig.2] schematically illustrates a cross-sectional view of the recuperator of [Fig.l]; - [Fig.3] illustrates a functional diagram of a turbogenerator for a vehicle according to one embodiment of the invention; - [Fig.4] illustrates a functional diagram of a turbogenerator for a vehicle according to another preferred embodiment of the invention; - [Fig.5] illustrates a functional diagram of a turbogenerator for a vehicle according to another preferred embodiment of the invention; - [Fig.6] illustrates a functional diagram of a turbogenerator for a vehicle according to another preferred embodiment of the invention; - [Fig.7] schematically illustrates a view in space of a cylindrical type recuperator; - [Fig.8] schematically illustrates a cross-sectional view of the recuperator of [Fig.7]; - [Fig.9] schematically illustrates a view in space of a parallelepiped type recuperator; - [Fig. 10] schematically illustrates a slightly oblique sectional view of the recuperator of [Fig.l], showing sections of circular secondary tubes; and - [Fig.l 1] schematically illustrates a sectional view similar to that of [Fig.10], for a recuperator equipped with square secondary tubes.

[0037] The invention relates to a motor vehicle comprising a turbogenerator which comprises: - at least one current generator Gl, G2; - at least one compressor Cl, C2; - at least one turbine T1, T2; and - at least one recuperator R being in particular a heat exchanger; - at least one cooler I which may in particular be a heat exchanger (as illustrated in [Fig.4]).

[0038] The reference HE schematically designates, for each heat exchanger R, I (figures 3 to 6), an accessory heat exchange circuit with a first circuit.

[0039] The cooler I (or "Intercooler" in English), and the recuperator R are heat exchangers. They can have the same internal architecture as illustrated in [Fig.5]. In this case, the hot fluid is pressurized air arriving from the first compressor C1, the cold fluid is ambient air or water circulating in the tubes. The architecture of the heat exchange remains the same.

[0040] The challenges for heat exchangers are presented below:

[0041] The first challenge is to have a high exchange efficiency between the hot source (the high temperature fluid) and the cold source (the low temperature fluid); this exchange efficiency is represented by an overall exchange coefficient (H [W / m2.K]).

[0042] To achieve high efficiency, it is preferable to have high exchange coefficients and a counter-current type heat exchange architecture. With a counter-current exchanger, the outlet temperature of the cold fluid can exceed the outlet temperature of the hot fluid, which is not possible in the case of an exchanger with a co-current architecture.

[0043] The second challenge is to have a low pressure drop. This is a very important criterion, particularly in the case of an application to turbogenerators. The flow passes in the heat exchanger twice (once at the compressor outlet and once at the turbine outlet). Minimizing pressure losses increases the turbine expansion rate and therefore increases the power generated by the turbine.

[0044] To minimize pressure losses, it is interesting to adapt the sections of the exchanges SI, S2, S3 according to the position in the exchanger. Indeed, the more the fluid (case of a gas) cools and the more the density decreases and the more the sections can be reduced to optimize the volume. Similarly; the more the fluid heats up, the more the volume flow increases and the more the passage sections must be increased. This is not possible with plate exchangers (possible with 3D printed exchangers but this is not currently industrializable on a large scale and at high speed as in the automotive industry).

[0045] The third challenge is that the heat exchanges at the walls must be controlled: If the collectors are external, there will be significant heat exchanges at the walls and this complicates the thermal insulation of the exchanger. Indeed, in the case of the turbogenerator, the hot inlet of the exchanger can be at temperatures above 750°C. If the collector is external, the surface temperature will be high and significant heat losses will have to be managed.

[0046] To minimize heat losses at the walls, it is advantageous for the hot exchange surface in contact with the outside to be minimized. Consequently, it will be advantageous for the hot inlet E2C to be inside the recuperator R.

[0047] The E1F, E2C inputs and S1F, S2C outputs of the exchanger have an impact on the volume and physical architecture of the machine. If the inputs / outputs are difficult to "move", we will be constrained by the design.

[0048] It is interesting to have a modular design where the inputs / outputs can be placed anywhere in the functional volume of the exchanger.

[0049] The choice of materials and sections is essential. The type of materials has an impact on the heat exchange coefficient. However, certain types of materials, such as copper or aluminum, have very high heat exchange coefficients, but poor high temperature resistance characteristics. Similarly, some materials are lighter than others and allow the total mass of the exchanger to be reduced. Of course, materials other than aluminum, copper and the alloys mentioned can be used.

[0050] Having a heat exchanger design where the type of materials can be adapted makes it possible to increase heat exchange performance and minimize the mass of the exchanger.

[0051] In certain applications and in particular in the case of the turbogenerator application, the gases leaving the recuperator R remain hot. This is due to the fact that the air temperature at the outlet of compressor C2 is high, and therefore the outlet temperature of the gases towards the ambient air on the hot side of the recuperator R, is necessarily higher than the inlet temperature (see second principle of thermodynamics: a heat exchange always goes from hot to cold). For example, the temperature of the gases at the outlet of the recuperator R of a turbogenerator application is of the order of 300°C. These gases still contain energy that can no longer be recovered in the thermodynamic cycle of the turbogenerator.

[0052] Having an exchange with a third (or even a fourth) working fluid, to recover the remaining energy, makes it possible to increase the overall efficiency of the system. Thus the possibility of exchanging with a third fluid is important in several types of applications. This makes it possible to reduce the complexity of the system (instead of having two exchangers, we can have just one for example).

[0053] The invention further proposes coupling the heat exchanger with an organic Rankine cycle RK machine (or ORC ball for "Organic Rankine Cycle" in English). The heat exchanger for the ORC loop is the same as the recuperator R of the turbogenerator cycle (figures 3 and 5). This makes it possible to save a heat exchanger (other architectures with the cooler I can also be envisaged).

[0054] We can even consider using this same recuperator R to preheat a fuel (tank FR). Indeed, in the case of liquid fuel (type Gasoline, Diesel, Ethanol, Methanol, E85, etc.) it is necessary to evaporate the fuel before entering the combustion chamber CCI, CC2 ([Fig.5]). The use of the energy available in the recuperator R makes it possible to vaporize the fuel and then inject it into the combustion chamber CCI, CC2. This therefore makes it possible to use the lost energy to carry out this evaporation (without costing electrical resistors). The circuit is presented in [Fig.5]. The fuel pump P pressurizes the fuel, which passes into the tubes of the recuperator R at the last section before being injected into the combustion chambers CCI, CC2.

[0055] So finally, this exchanger can be used to exchange with several fluids, we can therefore imagine having an architecture which combines both an ORC RK cycle with a fuel evaporator. Or even an architecture where we add tubes where a refrigerant fluid circulates to heat the passenger compartment from the thermal / gas discharges at the outlet of the recuperator R.

[0056] The heat exchanger can contain two paths:

[0057] A path of a first fluid Fl: In the case of the turbogenerator application, this first fluid Fl is pressurized air at the outlet of the compressor C2. This pressurized fluid circulates in tubes TS.

[0058] A path of a second fluid F2: in the case of the turbogenerator application, this fluid corresponds to the hot gases at the outlet of the turbine T2. This fluid F2 is channeled using sections in the form of TP channels which have the role of routing the gases and maintaining a counter-current exchanger architecture. The counter-current exchange means that the two fluids Fl and F2 always circulate in the opposite direction - The TP channels have the role of guiding the hot fluid F2. The cold fluid Fl is guided by the TS tubes. The cold fluid Fl changes direction at the level of the VT plenum volumes. The cooler I when it is based on the same architecture as the recuperator R, is also a counter-current exchanger. The gas in the TP tubes circulates in the opposite direction to the gases in the TS pipe sections. The role of the channels is to guide the hot source in the exchanger. This ensures counter-current operation.The heat exchange in the exchanger is counter-current.

[0059] The first fluid F1 and the second fluid F2 move back and forth. The first fluid F1 passes through a settling volume on both sides of the heat exchanger to change direction. The second fluid F2 changes direction by passing through slots FF which allow the second fluid F2 to return in the opposite direction (figures 2 and 10).

[0060] The second fluid F2 can be collected to escape at the outlet of the heat exchanger at different locations. Thus, the exhaust can be located at different locations on the external part of the heat exchanger.

[0061] The inlets and outlets of the heat exchanger can all be on the same side, or on opposite sides (figures 7 and 9).

[0062] The applicant opted for a counter-current exchanger design. The pressurized cold fluid circulates inside the TS pipes (circular or square). The hot flow from the turbine T2 circulates around these TS tubes in counter-current.

[0063] The external shape of the exchanger can be cylindrical or parallelepipedal. In all configurations, the pressurized fluid F1 arriving from the compressor C2 passes through the tubes TS. [Fig. 10] illustrates a sectional view showing how the tubes TS inside the exchanger are positioned.

[0064] This pressurized air circulating in the TS tubes is heated by the hot gases coming from the T2 turbine circulating around the TP tubes in a counter-current manner. The number of passes (round trip) is variable (we can have 1 pass, 2 passes, 3 passes, etc... depending on the heat exchange that we wish to implement).

[0065] The total number of TS tubes in each section is variable. The cross-section of the TS tubes in each section is also variable. The number of TS tubes and the cross-section of the TS tubes can be adapted according to the characteristics of the fluids (temperature reached) at each section. This is an important parameter that allows us to optimize the exchanger and to have an exchanger behavior close to 3D printed variable section exchangers.

[0066] The materials can also be adapted in each section. For example, on a three-pass round-trip exchanger, aluminum can be used, which has good heat exchange characteristics and is not heavy, in the last hot gas section (or a first compressed air preheating section). Copper can be used in a second section, knowing that copper has good heat transfer coefficients (but which begins to lose its mechanical strength characteristics at 700°C). Finally, inconel or steel can be used in a third section (the hottest on the gas side) where there are high thermal constraints. This is an interesting characteristic allowing the optimization of heat exchanges and the weight of the exchanger. Of course, other materials than aluminum, copper and the alloys mentioned can be used.

[0067] The length of the TS tubes is variable and depends on the calculated thermal exchanges.

[0068] The compressed air leaving compressor C2 enters the peripheral tubes. This isolates the peripheral zone of the exchanger and reduces heat losses.

[0069] The hot air leaving the turbine enters in the middle. Any diffusion and heat loss will be recovered by the surrounding flows. By choosing this architecture, we can reduce losses at the walls and recover heat losses internal to the exchanger.

[0070] The gases leaving the turbine T2 and entering the exchanger are channeled inside by TP sheets which will give the direction of the flow. The difference between the section of the TP sheets and the total surface area of ​​the TS tubes gives the passage section and consequently defines the passage speed in each stage. The hot inlet E2C and the cold outlet S1F positioned in the middle are illustrated by figures 1, 7 and 9.

[0071] The heat exchanger may be single-flow, double-flow, or any other known type of fluid path. The number of passages in the recuperator is variable and the size of the latter is variable.

[0072] One objective is to integrate the CCI combustion chamber inside and to be able to channel air so as to enter the CCI combustion chamber after preheating.

[0073] As regards the preferred manufacturing method, a part called a flange can be produced, with the different holes, then the TS tubes can be assembled and positioned in the holes.

[0074] In particular, the sides are cut on both sides (sides 3 mm thick for example) / we can do fast laser cutting or with high pressure water injection; we put the tubes (materials depending on the levels), on both sides on the sides; copper washers are added and then the assembly is placed in an oven (under vacuum down to 0.1 mbar) with a temperature-controlled atmosphere.

[0075] The furnace is preheated to 750°C at a temperature increase rate of the order of 10°C / min (temperature rise ramp).

[0076] Then a second temperature increase ramp at 5°C / min and up to 1100°C is carried out.

[0077] The brazing process is carried out for 15 min, then the furnace is cooled to 900°C still under vacuum, then to room temperature with an argon atmosphere.

[0078] Another method consists of welding the ends of the tubes onto the plate; the welding can be done by laser welding, for example.

[0079] The shape of the exchanger can be cylindrical (figures 7 and 8) or rectangular ([Fig.9]).

[0080] The sides allow the tubes TS to be fixed in which the fluid F1 circulates (in the case of the turbogenerator cycle, this would be the pressurized air at the outlet of the compressor C2). Guide sections allow the fluid F2 to circulate in the counter-current direction relative to the fluid FL

[0081] Two VT plenum volumes are located on both sides of the exchanger (figures 2, 8). The fluid Fl circulating in the tubes (pressurized) arrives in these volumes to change direction and re-enter other tubes TS in another section.

[0082] These volumes also have the role of thermally insulating the two sides of the exchanger.

[0083] The position of the inputs and outputs can be changed. As shown in [Fig.l] (with the output in broken lines), with the modular design, the positions of the outputs and inputs can be changed.

[0084] For example, the fluid outlet 2 (hot gas in the case of the turbogenerator) can be placed on the left, right, top or bottom of the recuperator R.

[0085] The position of the fluid outlet F1 is also variable. For example, on the exchanger, an outlet can be placed coaxially with the inlet E2C of the hot fluid F2.

[0086] In addition, the TS tubes can be of rectangular sections as illustrated in [Fig.11].

[0087] The internal sections that make the passage can be circular or rectangular.

[0088] The exchanger is not necessarily symmetrical. The position of the hot inlet E2C can be changed, thus placing more tubes on one side than the other.

[0089] The technical advantages of the invention are in particular the following: - Improving the efficiency of the recuperator by proposing a counter-current exchanger; - Reduce heat loss to the exterior via walls and external surfaces; - Offer a modular and adaptable design depending on the application; - Allow to modify the positions of the exchanger inputs / outputs; - Allow to modify the number of passage sections (TS tubes) in each stage of the exchanger; - Allow the section of each passage to be modified in each floor of the exchanger; - Allow to modify the materials in each passage section; - Allow you to modify the number of passages (round trip) in the interchange; - Allow to use different type of working fluid (Air-Air / Air-Water / Air-ORC / Water-Water / Water-ORC or any other possible combination); - Allow the use of several working fluids (for example, use the recuperator in Air - Air mode and also preheat another ORC type fluid for a Rankine loop, or use the energy to preheat a heat transfer circuit to ensure the thermal needs of the vehicle, especially in winter; - Allow the exchanger to be produced using several types of processes such as laser welding or brazing.

Claims

Claims

1. Heat exchanger (R, I) comprising: - first heat exchange sections (TP, SI) upstream of a circuit for passing a first fluid (F2), the first sections (TP, SI) comprising first circulation tubes (TS) for a second fluid (F1); and - second heat exchange sections (TP, S2) downstream of said first sections (TP, SI) of said circuit for passing the first fluid (F2), the second sections (TP, S2) comprising second circulation tubes (TS) for said second fluid (F1), characterized in that it comprises a counter-current heat exchange architecture further comprising third heat exchange sections (TP, S3) downstream of said second sections (TP, S2) of said circuit for passing the first fluid (F2), said third sections (TP, S3) comprising third circulation tubes (TS) for said second fluid (F1),the size of said first heat exchange sections (SI) being different from the size of said second heat exchange sections (S2), the size of said third heat exchange sections (TP, S3) being different from the size of said first and / or second heat exchange sections (TP, SI, S2), the number and / or the section of the first circulation tubes (TS) being different from those of the second and / or third circulation tubes (TS).,

2. Heat exchanger according to claim 1, characterized in that it comprises a hot inlet upstream of the first heat exchange sections (TP, SI), the walls of the hot inlet are arranged inside the heat exchanger (R, I), so as to limit the contact between the walls of the hot inlet and the outside.

3. Heat exchanger according to any one of claims 1 to 2, characterized in that it comprises at least one inlet and at least one outlet, and the heat exchanger (R, I) has a modular architecture so that said inlet and said outlet can be arranged at different locations in the functional volume of the heat exchanger (R, I).

4. Heat exchanger according to any one of claims 1 to 3, characterized in that it has a composite structure comprising aluminum in a hot gas section, copper in a heat transfer section of less than 600°C, and metal alloys or steel in a thermal stress section of more than 650°C.

5. Heat exchanger according to any one of claims 1 to 4, characterized in that it is connectable to at least three different fluid circuits.

6. Heat exchanger according to any one of claims 1 to 5, characterized in that it is connectable to a fuel circuit comprising a fuel tank (FR) and / or to an organic Rankine cycle machine (RK).

7. Motor vehicle comprising at least one turbomachine equipped with at least one heat exchanger according to any one of claims 1 to 6.

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