Aircraft having a fuel-cell propulsion system

Abstract

The invention relates to an aircraft (1) having a fuel-cell propulsion system (2), wherein the fuel-cell propulsion system (2) comprises - a fuel cell (3) for supplying electricity to an electric propulsion apparatus (4) of the aircraft (1), - a fuel store (5) for storing fuel for the fuel cell (3), and - a cooling apparatus (6) for cooling the fuel cell (3), wherein - a main heat exchanger (7) of the cooling apparatus (6) and the fuel store (5) are arranged on a top side (8) of a fuselage (9) of the aircraft (1), and - the main heat exchanger (7) is arranged in front of the fuel store (5) toward the aircraft nose.

Description

[0001] Aircraft with a fuel cell propulsion system

[0002] Description

[0003] The invention relates to an aircraft with a fuel cell propulsion system. The fuel cell propulsion system comprises a fuel cell, a fuel storage unit, and a cooling device.

[0004] The design of innovative propulsion systems based on fuel cells differs significantly from conventional aircraft turbomachinery. Fuel cells convert chemically bound energy from a fuel, particularly hydrogen, into electrical energy. As a byproduct, large amounts of waste heat are generated at low temperatures, which must be dissipated into the environment via a heat exchanger. The integration of these innovative propulsion systems, such as the fuel cell propulsion system, also differs significantly from conventional propulsion systems. The two aspects mentioned above—fuel storage and heat dissipation from the aircraft—represent the greatest integration challenges for the aircraft. Due to the large dimensions of the heat exchangers, the integration is aerodynamically complex and generates significant flow resistance (drag).

[0005] The invention is based on the object of providing an aircraft with a fuel cell propulsion system which integrates the components of the fuel cell propulsion system in such a way that a flow resistance of the aircraft is optimized with a high usable volume of the aircraft.

[0006] The problem is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are described by the dependent patent claims, the following description, and the figures.

[0007] The invention provides an aircraft with a fuel cell propulsion system. The fuel cell propulsion system has at least one fuel cell for electrically supplying an electric drive device of the aircraft, at least one fuel storage device for storing fuel for the fuel cell, and at least one cooling device for cooling the fuel cell. It is provided that a main heat exchanger of the cooling device and the fuel storage device are arranged on an upper side of a fuselage of the aircraft, and the main heat exchanger is arranged on the bow side in front of the fuel storage device.

[0008] An aircraft can be understood, in particular, as an airplane. Furthermore, the aircraft can also be designed as a rotary-wing aircraft. In particular, the aircraft is heavier than air and has an electric propulsion system.

[0009] The fuel cell of the fuel cell propulsion system is designed to convert chemically bound energy of the fuel into electrical energy and thus supply the electric drive device, which may in particular comprise at least one electric machine, for example, an electric motor. Furthermore, the fuel cell can supply other systems of the aircraft with electrical energy. The electric machine can, in turn, drive at least one drive means, for example, a propeller, a fan, a rotor, or the like, to generate propulsion and / or lift.

[0010] The fuel, in particular hydrogen, can be stored in a fuel storage unit, which can comprise at least one pressure tank, preferably of cylindrical shape. The fuel storage unit can be designed to be large enough to accommodate a desired maximum range of the aircraft. Furthermore, a diameter and / or length of the pressure tank can be designed depending on the flow resistance of a particular aircraft configuration.

[0011] The fuel can be supplied to the fuel cell via appropriate fuel lines connecting the fuel storage and the fuel cell. Furthermore, the fuel cell may require oxygen, which can be supplied to the fuel cell from the ambient air by means of an air supply device. In addition to electrical energy, the fuel cell drive system, in particular the fuel cell, generates a large amount of waste heat at a low temperature level, for example, between 80°C and 100°C. This waste heat must be dissipated to the environment via the cooling device so that the fuel cell drive system can be maintained at a desired operating temperature.

[0012] The cooling device has at least one main heat exchanger. The main heat exchanger is provided and designed to dissipate the waste heat of the fuel cell drive system to the environment, in particular to the ambient air. For example, the waste heat can be conducted into the cooling fins or cooling plates of the main heat exchanger. The cooling fins can then be cooled by the ambient air, preferably by forced convection.

[0013] In particular, the ambient air can have a temperature level of -50°C to 35°C, so that the main heat exchanger is preferably designed such that even at an ambient air temperature level of 35°C, the main heat exchanger can provide appropriate cooling capacity. In particular, due to a small difference in the temperature level of the fuel cell system compared to the ambient air, it may be necessary for the main heat exchanger to be designed to be sufficiently large in order to be able to provide the required cooling capacity.

[0014] It is envisaged that the main heat exchanger and the fuel storage tank are arranged on the upper side of the aircraft's fuselage. The upper side can be understood as the side of the fuselage which is at the top of the fuselage when the aircraft is stationary or in stationary horizontal flight. For example, the upper side can also be understood as the roof of the fuselage. In particular, with a round or oval cross-section of the fuselage, the upper side can be designed as an upper circular arc section, for example with an opening angle of the circular arc section in a range of 90° to 180°, preferably 120°.

[0015] Furthermore, it is provided that the main heat exchanger is arranged on the bow side in front of the fuel storage unit. In other words, the main heat exchanger is arranged closer to a bow or aircraft nose of the aircraft in relation to the fuel storage unit, with the fuel storage unit being arranged closer to a rear of the aircraft. The bow represents in particular a front part of the aircraft in a primary flight direction of the aircraft, whereas the rear represents a rear part of the aircraft in the primary flight direction. In other words, the main heat exchanger is arranged further forward or in front of the fuel storage unit in relation to the fuel storage unit. In principle, the fuel storage unit is arranged “in the slipstream” of the main heat exchanger.

[0016] The invention offers, among other advantages, the significant reduction in flow resistance through the combined integration of the main heat exchanger and the fuel storage unit on the roof. This advantageously increases the overall efficiency of the aircraft.

[0017] Furthermore, it can be considered advantageous that the present invention essentially occupies no space within the fuselage. Since the fuselage essentially represents the aircraft's usable space, it can be used without restriction and with maximum utilization for a payload or passengers.

[0018] A further advantage of the present invention is that the main heat exchanger and the energy storage unit on the upper side of the fuselage can be dimensioned and configured variably and, apart from aerodynamic and flight-mechanical properties of the aircraft, essentially without restrictions, according to the design, since they do not conflict spatially with other systems of the aircraft on the upper side of the fuselage.

[0019] Compared to arranging the heat exchanger on an aircraft wing, particularly within an engine nacelle, the engine nacelle can be significantly reduced in size. From an aerodynamic perspective, this advantageously improves airflow around the wing.

[0020] Furthermore, the invention improves the integration of the cooling device. Both the fuel storage tank and the heat exchanger must be connected via coolant lines. The spatial proximity of both components allows the overall length of the coolant lines used to be reduced, thus reducing the structural weight of the fuel cell drive system.

[0021] Another advantage is that the original structure of the aircraft can remain largely unchanged, significantly simplifying the integration of the fuel cell propulsion system into the aircraft. The integration of the fuel cell propulsion system can be achieved solely by modifying the upper surface of the fuselage or the wing. Accordingly, it can be provided that the fuel cell propulsion system can be integrated into an existing aircraft design.

[0022] By locating the fuel storage unit on the roof, most of the fuel lines can also be located on top of the aircraft. In the event of a fuel leak, especially hydrogen, a safe leak path is ensured, as the hydrogen can escape upwards. This significantly increases the safety of the overall system.

[0023] One embodiment provides that the main heat exchanger and the fuel storage unit are arranged compactly next to one another as an aerodynamic unit, in particular compactly in a longitudinal direction of the aircraft. An aerodynamic unit can be understood as an arrangement in which the main heat exchanger and the fuel storage unit are externally dimensioned as closely as possible and coordinated with one another so that they can fit together. In other words, an overall height and / or overall width of the main heat exchanger essentially corresponds to an overall height and / or overall width of the fuel storage unit. A space between the main heat exchanger and the fuel storage unit is preferably minimized so that the fuel storage unit is located virtually in the slipstream of the main heat exchanger.

[0024] This compact design is particularly advantageous for the aerodynamics of the aircraft, as the ambient air flowing around it can only cause minimal turbulence between the main heat exchanger and the energy storage unit. Furthermore, the frontal area exposed to airflow and the wetted surface of the aircraft can be advantageously reduced. One embodiment provides for the aircraft to comprise a streamlined fairing that jointly encloses the main heat exchanger and the fuel storage unit. In other words, the fairing forms a housing for the main heat exchanger and the fuel storage unit on the top, front, and rear sides, so that the main heat exchanger and the fuel storage unit are arranged in a space enclosed by the top side of the fuselage and the fairing. The fairing has a streamlined design.This means that the fairing has a shape such that its aerodynamic drag relative to the surrounding ambient air is minimized. In particular, the fairing can be arranged on the fuselage in such a way that the flow resistance in a transition region between the fuselage and the fairing is minimized. In other words, an upper side of the fairing can be substantially convex and fit snugly against the fuselage. Preferably, the main heat exchanger can be structurally integrated into a front of the fairing.

[0025] Among other things, the cladding offers the advantage of significantly reducing the flow resistance of the main heat exchanger and the fuel storage tank. Furthermore, the cladding can protect the main heat exchanger and the fuel storage tank from external influences, such as weather.

[0026] One embodiment provides that the fairing has an inlet opening on the bow side for admitting ambient air into the main heat exchanger. Preferably, the fairing has an outlet opening for discharging the ambient air from the fairing. In particular, the inlet opening of the fairing and the inlet of the main heat exchanger can be formed as a common unit.

[0027] In this context, "nose side" can be understood in particular as a front part of the fairing in the primary flight direction of the aircraft, in particular a front of the fairing. Accordingly, it can be provided that the front of the fairing has the inlet opening. In particular, the ambient air can flow into the main heat exchanger via the inlet opening and absorb heat. The ambient air can flow out of the main heat exchanger via an outlet of the main heat exchanger and preferably leave the fairing via the outlet opening. The fairing preferably has a plurality of outlet openings.

[0028] A nose-side inlet opening proves to be advantageous during aircraft flight, particularly in the main flight direction, since the ambient air flowing around the aircraft can flow into the inlet opening in a main flow direction of the ambient air in an aerodynamically favourable manner.

[0029] One embodiment provides for the outlet opening to be arranged in a separation zone of a surrounding ambient air flowing around the fairing. A separation zone can also be understood as a so-called "dead water zone." In the separation zone, the surrounding ambient air travels or lifts off a surface of the fairing that is flowed around. As a result, the ambient air swirls in the separation zone. This can have a negative impact on the aerodynamics of the fairing, particularly due to increased flow resistance. In particular, the separation zone can be located in a rear region of the fairing.

[0030] Preferably, a separation zone(s) on the fairing is known, for example, through testing in a flow channel. An outlet opening can be specifically positioned in the known separation zone. Air flowing out of the outlet opening can specifically enrich or energize the separation zone, thus counteracting the separation of the surrounding ambient air. This advantageously reduces flow resistance and improves the aerodynamics of the fairing.

[0031] One embodiment provides that the outlet is configured such that the discharged ambient air promotes airflow around the aircraft's tail unit. In particular, the tail unit can be arranged behind the fuselage, or behind the main heat exchanger and the fuel storage unit, as viewed in the main flight direction. The favorable airflow around the tail unit can advantageously enhance the stability and maneuverability of the aircraft.

[0032] One embodiment provides that an air duct of the aircraft, in particular of the cooling device within the fairing, fluidically connects an outlet of the main heat exchanger to the outlet opening of the fairing. In particular, the air duct or multiple air ducts can be configured to guide the outflowing ambient air from the outlet of the main heat exchanger specifically to the outlet opening(s) of the fairing, so that the air can be guided past the fuel reservoir in a directed manner. This can prevent the heated air flowing from the outlet of the main heat exchanger from swirling within the fairing and / or the heated air from releasing heat within the fairing. Thus, the air can exit the fairing by means of the at least one air duct at high energy, i.e. with high kinetic and thermal energy.

[0033] One embodiment provides that the fuel storage unit comprises two cylindrical pressure tanks, each of whose main extension direction is substantially parallel to a longitudinal axis of the aircraft. The two cylindrical pressure tanks are preferably arranged side by side along the longitudinal axis. The main extension direction can, in particular, extend along a geometric height of the cylindrical shape of the pressure tank. In other words, the cylindrical pressure tanks can be arranged side by side in a horizontal position.

[0034] Two cylindrical pressure tanks for the fuel storage system can be advantageous compared to a single fuel storage system of the same total capacity in that flow resistance is reduced. This can increase the efficiency of the aircraft.

[0035] One embodiment provides for the cooling device to have a secondary heat exchanger arranged in a downwash region of an aircraft propeller. In particular, the secondary heat exchanger can be dimensioned and designed several times smaller than the main heat exchanger. The secondary heat exchanger can be configured to provide the required cooling capacity during stationary operation of the aircraft with an active fuel cell propulsion system and an active propulsion device.

[0036] For example, the main heat exchanger can only provide a low cooling capacity during stationary operation, since the cooling fins or cooling plates of the main heat exchanger cannot be forced to cool convectively due to the lack of ambient airflow. According to this example, the bypass heat exchanger can provide a cooling capacity using the downwash from the propulsion means, in particular the propeller, which can be designed for stationary operation for the fuel cell propulsion system. This has the advantage that the cooling device can provide sufficient cooling capacity in every operating situation of the aircraft.

[0037] One embodiment provides that a liquid cooling medium of the cooling device is configured to absorb waste heat from the fuel cell and dissipate it into the ambient air within the main heat exchanger. This has the advantage that the fuel cell and the main heat exchanger can be arranged and operated spatially separated from one another. Thus, the arrangement of the fuel cell can be selected independently of the arrangement of the main heat exchanger, and vice versa.

[0038] The invention also includes combinations of the features of the described embodiments.

[0039] Exemplary embodiments of the invention are described below. These are shown in:

[0040] FIG. 1 is a perspective view of an aircraft with a fuel cell propulsion system according to a preferred embodiment;

[0041] FIG. 2 is a side view of an aircraft with a fuel cell propulsion system according to a preferred embodiment.

[0042] The exemplary embodiment explained below is a preferred embodiment of the invention. In the exemplary embodiment, the described components of the embodiment each represent individual, independently considered features of the invention, which also further develop the invention independently of one another and are thus also to be considered as components of the invention, either individually or in a combination other than that shown. Furthermore, the described embodiment can also be supplemented by further features of the invention already described.

[0043] In the figures, the same reference symbols designate elements with the same function.

[0044] FIG. 1 shows a perspective view of an aircraft 1 with a fuel cell propulsion system 2 according to a preferred embodiment. FIG. 2 shows a side view of the aircraft 1. The following description of the figures applies to both figures.

[0045] The aircraft 1 can, for example, be designed as an airplane 1, in particular as a conventional aircraft 1 with a fuselage 9, a wing 12, and a tail unit 16 at a tail 11 of the aircraft 1. For example, the aircraft 1 is designed as a twin-engine, high-wing aircraft. Accordingly, the aircraft 1 can also be designed as a mid-wing, low-wing, flying wing, rotary-wing, or the like.

[0046] The fuel cell propulsion system 2 of the aircraft 1 can have at least one fuel cell 3 for supplying electrical power to an electric drive device 4 of the aircraft 1. For example, the fuel cell 3 can be arranged together with the electric drive device 4, in particular an electric motor, which can drive, for example, a propeller 22 (see FIG. 2) or a fan, in a nacelle below one of the wings 12.

[0047] The fuel cell drive system 2 can further comprise a fuel storage unit 5 for storing fuel for the fuel cell 3. The fuel can in particular be hydrogen, which can be stored under high pressure, in particular in liquid form, in the fuel storage unit 5. The fuel storage unit 5 can in particular comprise at least one pressure tank, for example a first pressure tank 18 and a second pressure tank 19. The pressure tanks 18, 19 can be cylindrical and each have a main extension direction 20, wherein the main extension direction 20 can represent a geometric height of the cylindrical shape of the cylindrical pressure tanks 18, 19. In particular, the pressure tanks 18, 19 can be arranged parallel to one another in a horizontal plane and essentially parallel to a longitudinal axis X of the aircraft 1.

[0048] The fuel storage unit 5 is arranged, in particular, on an upper side 8 of the fuselage 9 of the aircraft 1. In other words, in this example, the pressure tanks 18, 19 of the fuel storage unit 5 are located on a roof of the fuselage 9, so that a usable space within the fuselage 9 is not restricted by the fuel storage unit 5.

[0049] The fuel cell drive system 2 may further comprise a cooling device 6 for cooling the fuel cell 3. The cooling device 6 may, for example, comprise a main heat exchanger 7, at least one secondary heat exchanger 21, a coolant tank 24, a coolant pump 26, and coolant lines.

[0050] The main heat exchanger 7 is arranged on the upper side 8 of the fuselage 9 of the aircraft 1, as well as on the bow side in front of the fuel storage 5. "Bow side" means that the main heat exchanger 7 is arranged closer to a bow 10 of the aircraft 1 than the fuel storage 5. In particular, it can be provided that the main heat exchanger 7 of the fuel cell drive system 2 must be large in size compared to a heat exchanger of a conventional drive system with a heat engine, since a temperature level of the fuel cell 3 is significantly lower than a temperature level of a heat engine. Due to the required size of the main heat exchanger 7, positioning it on a roof of the aircraft 1 is particularly advantageous from an aerodynamic perspective.

[0051] For example, the main heat exchanger 7 and the fuel storage 5 are arranged compactly next to one another as an aerodynamic unit, so that the aircraft aerodynamics can be improved. In particular, a fairing 13 of the main heat exchanger 7 and the fuel storage 5 can thus be designed as a common fairing 13. The streamlined fairing 13, together with the upper side 8 of the fuselage 9, forms a space within which the main heat exchanger 7 and the fuel storage 5 are arranged. In particular, the fairing 13 has an aerodynamically advantageous shape. Further components, for example the coolant pump 26, coolant lines, fuel lines, and the like, can be arranged within the fairing 13.

[0052] Preferably, the fairing 13 forms an inlet opening 14 at its front, i.e., on the bow side, which can correspond to an inlet 25 of the main heat exchanger 7. During flight or forward travel of the aircraft 1, the ambient air can thus flow into the inlet 25, aided by the flow of the ambient air, and in particular, by forced convection, extract heat from the cooling fins or cooling plates of the main heat exchanger 7.

[0053] The air flowing into the inlet 25 can flow out of an outlet 17 of the main heat exchanger 7. In particular, the outflowing air can be guided through air ducts within the fairing 13 around the pressure tanks 18, 19 to one or more outlet openings of the fairing 13. The outlet openings are preferably arranged in a separation region 15 so that the outflowing air can enliven a so-called dead water area of ​​the separation region 15. Alternatively or additionally, the outlet openings can be designed in such a way that a flow around the tail unit 16 can be promoted.

[0054] Overall, the example shows how the invention can be used to integrate a main heat exchanger and a fuel storage unit in an aircraft in an aerodynamically advantageous manner.

[0055] The invention can provide a combined integration variant for the fuel storage tank and a main heat exchanger on the roof of the aircraft. The combined integration of the two subsystems can significantly reduce the aircraft's flow resistance and increase its overall efficiency. The voluminous pressure tanks are conceptually positioned in the "slipstream of the main heat exchanger."

[0056] Unlike traditional integration variants, the fuel storage is not located in the fuselage or on the wing, but on the roof of the aircraft. The cylindrical shape of the pressure tanks can be retained. Depending on the flow resistance of the configuration, various diameters and lengths of the fuel storage are conceivable. Furthermore, it is conceivable to divide a large pressure tank into two smaller pressure tanks. The diameter of these smaller pressure tanks can be significantly smaller, which reduces storage efficiency. From an aerodynamic perspective, however, the division could result in significant advantages in flow resistance, which could increase the efficiency of the overall aircraft.

[0057] To further reduce the flow resistance of this configuration, a fairing for the entire roof installation can be provided. The main heat exchanger, cooling device, or thermal system, is structurally integrated into the front of this fairing. By locating the main heat exchanger on the roof, the engine nacelle on the wing can be significantly reduced in size. From an aerodynamic perspective, this can improve the flow around the wing. Combining the fuel storage and main heat exchanger in a fairing can reduce both the frontal area exposed to airflow and the wetted surface of the aircraft. As a result, the aircraft's flow resistance can be optimized.

[0058] Further advantages of the combined integration of tank and heat exchanger on the roof are the following: First, the integration of the cooling system is improved. Both the tank and the heat exchanger must be connected via coolant lines. The spatial proximity of both components allows the overall length of the coolant lines used to be reduced, thereby reducing the structural weight of the propulsion system. Second, the original structure of the aircraft can remain largely unchanged, which significantly simplifies aircraft integration. Propulsion system integration can be achieved solely through modifications to the roof or wing, which may even allow a retrofit to an existing aircraft type. Third, by placing the H2 tank on the roof, most of the hydrogen-carrying lines can also be located on top of the aircraft.In the event of a hydrogen leak, a safe leak path can be ensured because the hydrogen rises upwards. This increases the safety of the entire system.

[0059] Installing the fuel storage and the main heat exchanger on the underside of the fuselage may be disadvantageous compared to the present invention due to FOD (Foreign Object Damage) risks, i.e. particles thrown from the nose gear.

[0060] Furthermore, the air can be directed through targeted air ducts through the fairing and around the pressure tanks, and then exhausted at the end of the fairing. Various integration goals can be pursued here, such as the aerodynamic optimization of the airflow around the fairing (enlivening "dead water areas") or the targeted influencing of the airflow around the tail unit.

[0061] List of reference symbols:

[0062] 1 aircraft

[0063] 2 Fuel cell drive system

[0064] 3 Fuel cell

[0065] 4 Electric drive device

[0066] 5 fuel storage

[0067] 6 Cooling device

[0068] 7 main heat exchangers

[0069] 8 Top

[0070] 9 Hull

[0071] 10 bugs

[0072] 11 Rear

[0073] 12 Wing

[0074] 13 Cladding

[0075] 14 Inlet opening of the fairing

[0076] 15 Detachment area

[0077] 16 tail unit

[0078] 17 Outlet of the main heat exchanger

[0079] 18 pressure tank

[0080] 19 Pressure tank

[0081] 20 Main direction of extension

[0082] 21 secondary heat exchangers

[0083] 22 propellers

[0084] 23 Air supply device

[0085] 24 Coolant tank

[0086] 25 Inlet of the main heat exchanger

[0087] 26 Coolant pump

[0088] X Longitudinal axis of the aircraft

Claims

Patent claims 1. Aircraft (1) with a fuel cell propulsion system (2), wherein the fuel cell propulsion system (2) - at least one fuel cell (3) for supplying electricity to an electric drive device (4) of the aircraft (1), - at least one fuel storage unit (5) for storing fuel for the fuel cell (3), and - at least one cooling device (6) for cooling the fuel cell (3), characterized in that - a main heat exchanger (7) of the cooling device (6) and the fuel storage (5) are arranged on an upper side (8) of a fuselage (9) of the aircraft (1), and - the main heat exchanger (7) is arranged on the bow side in front of the fuel storage tank (5).

2. Aircraft (1) according to claim 1, wherein the main heat exchanger (7) and the fuel storage (5) are arranged compactly next to one another as an aerodynamic unit.

3. Aircraft (1) according to claim 1 or 2, characterized by a streamlined fairing (13) which jointly encloses the main heat exchanger (7) and the fuel storage (5).

4. Aircraft (1) according to claim 3, characterized in that the fairing (13) has, on the bow side, an inlet opening (14) for admitting ambient air into the main heat exchanger (7) and an outlet opening for discharging the ambient air from the fairing (13).

5. Aircraft (1) according to claim 4, characterized in that the outlet opening is arranged in a separation region (15) of a flowing ambient air on the fairing (13).

6. Aircraft (1) according to claim 4 or 5, characterized in that the outlet opening is arranged such that ambient air discharged from the outlet opening promotes a flow around a tail unit (16) of the aircraft (1).

7. Aircraft (1) according to one of claims 4 to 6, characterized by an air duct which fluidically connects an outlet (17) of the main heat exchanger (7) with the outlet opening of the fairing (13) within the fairing (13).

8. Aircraft (1) according to one of the preceding claims, characterized in that the fuel storage (5) has two cylindrical pressure tanks (18, 19), the respective main extension direction (20) of which is substantially parallel to a longitudinal axis (X) of the aircraft (1), wherein the two cylindrical pressure tanks (18, 19) are arranged next to one another along the main extension direction (20).

9. Aircraft (1) according to one of the preceding claims, characterized in that the cooling device (6) has a secondary heat exchanger (21) which is arranged in a downwash region of a propeller (22) of the aircraft (1).

10. Aircraft (1) according to one of the preceding claims, characterized in that a liquid cooling medium of the cooling device (6) is designed to absorb waste heat from the fuel cell (3) and to dissipate it to ambient air within the main heat exchanger (7).

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