WATER-BASED, COMBINED COOLING AND HUMIDIFICATION SYSTEM FOR A FUEL CELL SYSTEM

Abstract

A combined cooling and humidifying system for a fuel cell system includes a first line strand, second line strand, gas separator, and water feed device. The first line strand has a supply line for feeding water to a heat exchanger of the fuel cell system and a return line for receiving a water-steam mixture from the fuel cell system. The gas separator is in the return line to at least partially separate the steam from the water-steam mixture and provide it at a steam connection. The second line strand has a fluid inlet for feeding a gaseous fluid to the fuel cell system. The steam connection is coupled to the second line strand downstream of the fluid inlet to admix steam with the fluid. The water feed device is coupled to the supply line to compensate for a separating mass flow of steam in the first line strand.

Claims

1. A cooling and humidifying system for a fuel cell system, comprising: a first line strand; a second line strand; a gas separator; a water feed device; the first line strand having a supply line for feeding water to a heat exchanger of the fuel cell system and a return line for receiving a water-steam mixture from the fuel cell system; the gas separator being disposed in the return line and configured to at least partially separate steam from the water-steam mixture and provide the steam at a steam connection; the second line strand having a fluid inlet for feeding a gaseous fluid to the fuel cell system; the steam connection being coupled to the second line strand downstream of the fluid inlet to admix steam with the fluid; and the water feed device for feeding water being coupled to the supply line to compensate for a separating mass flow of steam from the first line strand.

2. The cooling and humidifying system according to claim 1, further having a third line strand for removing exhaust gas of the fuel cell system, wherein the third line strand is connected to an exhaust-gas connection, and wherein the water feed device has a condenser to condense steam from the fuel cell system.

3. The cooling and humidifying system according to claim 1, wherein the second line strand has an air inlet and is configured for feeding air to a cathode path of the fuel cell system.

4. The cooling and humidifying system according to claim 3, wherein the second line strand has a first compressor for compressing air downstream of the air inlet, downstream of which an air intercooler is connected, and wherein the steam connection is coupled to the second line strand downstream of the intercooler.

5. The cooling and humidifying system according to claim 1, wherein the second line strand has a hydrogen inlet and is configured for feeding hydrogen to an anode path of the fuel cell system.

6. The cooling and humidifying system according to claim 2, further having a control unit which is coupled to the condenser and is configured to regulate an output of the condenser such that a total mass of water in the first line strand is regulated to a predetermined value.

7. The cooling and humidifying system according to claim 1, wherein a second compressor is connected downstream of the steam connection and compresses the steam to a pressure which substantially corresponds to or exceeds a pressure in the second line strand.

8. The cooling and humidifying system according to claim 1, wherein an absolute pressure in the first line strand is 1 bar.

9. The cooling and humidifying system according to claim 6, wherein the second line strand has an air inlet and is configured for feeding air to a cathode path of the fuel cell system, wherein the second line strand has a first compressor for compressing air downstream of the air inlet, downstream of which an air intercooler is connected, wherein the steam connection is coupled to the second line strand downstream of the intercooler, and wherein the air intercooler is thermally coupled to the second line strand downstream of a water feed unit and upstream of a water supply connection of the second line strand.

10. A vehicle having a fuel cell system with at least one fuel cell and a cooling and humidifying system according to claim 1.

11. The vehicle according to claim 10, wherein the vehicle is an aircraft, wherein the fuel cell system and the cooling and humidifying system are arranged in a pressurized region of the aircraft, and a hydrogen tank which can be coupled to the fuel cell system is arranged in a non-pressurized region of the aircraft.

12. A method for cooling a fuel cell system, comprising: feeding water to a heat exchanger of the fuel cell system in a supply line of a first line strand; receiving a water-steam mixture from the fuel cell system in a return line of the first line strand; separating at least some of the steam from the water-steam mixture by a gas separator in the return line and providing the steam at a steam connection; feeding steam from the steam connection into a second line strand with which a gaseous fluid is guided to the fuel cell system; and feeding water from a water feed device into the supply line for compensating for the separated steam.

13. The method according to claim 12, further comprising condensing steam from an exhaust-gas flow of the fuel cell system by a condenser for feeding to the first line strand.

14. The method according to claim 12, wherein the gaseous fluid is air as oxidant for a cathode path or hydrogen as fuel for an anode path.

15. The method according to claim 13, wherein the condensing is carried out by a condenser whose output is regulated such that a total mass of water in the first line strand is kept constant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further features, advantages and possible uses of the disclosure herein emerge from the following description of the exemplary embodiments and from the figures. Here, all of the features described and/or illustrated in the figures form the subject matter of the disclosure herein individually and in any desired combination, even independently of the combination of the features in the individual claims or the back-references thereof. Furthermore, in the figures, the same reference signs are used for identical or similar objects.

[0030] FIG. 1 shows a schematic illustration of a fuel cell system and of a cooling system.

[0031] FIG. 2 shows an aircraft.

[0032] FIG. 3 shows a method as a schematic block diagram.

DETAILED DESCRIPTION

[0033] FIG. 1 shows a fuel cell system 2 which is coupled to a combined cooling and humidifying system 4. The system 4 has a first line strand 6, a second line strand 8, a third line strand 9, a gas separator 10 and a water feed device 12. The latter is designed as a condenser, as stated further below.

[0034] The first line strand 6 has a supply line 14 which is connected to a heat exchanger 16 of the fuel cell system 2. In the first line strand 6 there is situated pure water which is guided via the first line strand 6 into a heat exchanger 16 of the fuel cell system 2 in order to absorb heat there. The thermal heat power of the fuel cell system 2 causes the water to be at least partially evaporated. With an absolute pressure of 1 bar in the first line strand 6, the water evaporates at 100° C. By virtue of the continuous replenishment of water and the continuous evaporation at the heat exchanger 16, the operating temperature of the fuel cell system 2 can therefore be set to the evaporation temperature of 100° C. Via the pressure level in the evaporator, the temperature of the fuel cell system 2 can be regulated within certain limits.

[0035] A mixture of water and steam leaves the heat exchanger 16 as a two-phase flow and passes into the return line 18. The flow flows there through the gas separator 10 which is designed to remove at least some of the steam from the two-phase flow. In the supply line 14 there is also situated a pump 20 which is operated, for example, via an electric motor 22. This could be supplied with electrical power from the fuel cell system 2, optionally via a buffer battery, or from another current source.

[0036] The second line strand 8 has an air inlet 24 through which air or oxygen-containing gas flows in. This is conveyed into the second line strand 8 by a first compressor 26 which can be driven by an electric motor 28. There is passage through an air filter 30 here. The compressed air passes into an air intercooler 32 and is then fed to a cathode path 34 of the fuel cell system 2. Separated steam from the gas separator 10 is provided at a steam connection 36 which is coupled to the second line strand 8. A corresponding admixing connection 38 is provided between the air intercooler 32 and the cathode path 34. It is possible to provide here a second compressor 40 for introducing the steam into the air mass flow. By admixing the steam, the air mass flow is therefore humidified directly before reaching the cathode path 34.

[0037] Exhaust air or exhaust gas from the fuel cell system 2 is provided at an exhaust-gas connection 42. In this example, the exhaust gas passes via the third line strand 9 into the water feed device 12, which is configured as a condenser, and condenses out water by cooling the exhaust gas below the dew point, for example to approximately 80° C. or somewhat lower. The cooling temperature is set in such a way that enough condensed water accumulates to set the water quantity in the cooling circuit to a desired level. The condensed water accumulates at a condensate connection 44 and is fed to the first line strand 6 at a water feed connection 45, with the result that the loss of steam caused by the humidification can be compensated for again. Before entering the first line strand 6, the water can be used for heating the introduced gas in an air intercooler 32. The condenser 12 can be coupled to a control unit 46 which is designed to regulate the output of the condenser 12 in such a way that the total mass of the water in the second line strand 6 corresponds to a predeterminable total mass and/or is constant.

[0038] At an operating temperature of the fuel cell system 2 of 100° C. and 2 bar gas pressure in the line strand 8, the quantity of the evaporated cooling water can result in a humidification degree of the supply air flow of approximately 78% RH, with a gas stoichiometry of 1.8 (the ratio of provided air quantity to consumed air quantity). At the exhaust-gas connection, the air moisture can be approximately 96% RH as a result of the additionally produced water. A temperature of approximately 79° C. is theoretically necessary to recover a sufficient water quantity. At these operating points, an efficient operation of the fuel cell system 2 with high conversion efficiencies can be made possible.

[0039] The fuel cell system 2 is connected here to a DC converter 48 which is designed to provide a DC voltage of predetermined level at a voltage connection 50. This can be passed to a voltage bus (not shown here). Consequently, the electric motors 22 and 28 can be connected to operate the cooling and humidifying system 4.

[0040] FIG. 2 shows an aircraft 52 which is equipped with a fuel cell system 2 and with a cooling and humidifying system 4. The fuel cell system 2 is arranged in a rear region of the aircraft 52, for example below a floor and in front of a pressure bulkhead, that is to say in a pressurized region of a fuselage 54.

[0041] Finally, FIG. 3 shows a schematic illustration of a method for cooling the fuel cell system 2 and comprises the steps of feeding 56 water to the heat exchanger 16 of the fuel cell system 2 in the supply line 14 of a first line strand 8, receiving 58 a water-steam mixture from the fuel cell system 2 in the return line 18 of the first line strand 8, separating 60 at least some of the steam from the water-steam mixture by the gas separator 10 in the return line 18 and providing 62 it at the steam connection 36, feeding 64 steam from the steam connection 36 into the second line strand 8 with which a gaseous fluid is guided to the fuel cell system 2, and feeding 66 water from the water feed device 12 into the supply line 14 to compensate for the separated steam. The feeding 66 can be preceded by the condensing 68 of steam from an exhaust-gas flow of the fuel cell system 2 by the condenser 12. Its output can be regulated 70 in such a way that the total mass of the water in the first line strand 6 is set to a predetermined value and is in particular kept constant.

[0042] While at least one example embodiment of the invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

REFERENCE SIGNS

[0043] 2 Fuel cell system

[0044] 4 Cooling system

[0045] 6 First line strand

[0046] 8 Second line strand

[0047] 9 Third line strand

[0048] 10 Gas separator

[0049] 12 Water feed device/condenser

[0050] 14 Supply line

[0051] 16 Heat exchanger

[0052] 18 Return line

[0053] 20 Pump

[0054] 22 Electric motor

[0055] 24 Air inlet/fluid inlet

[0056] 26 First compressor

[0057] 28 Electric motor

[0058] 30 Air filter

[0059] 32 Air intercooler

[0060] 34 Cathode path

[0061] 36 Steam connection

[0062] 38 Admixing connection

[0063] 40 Second compressor

[0064] 42 Exhaust-gas connection

[0065] 44 Condensate connection

[0066] 45 Water feed connection

[0067] 46 Control unit

[0068] 48 DC converter

[0069] 50 Voltage connection

[0070] 52 Aircraft

[0071] 54 Fuselage

[0072] 56 Feeding

[0073] 58 Receiving

[0074] 60 Separating

[0075] 62 Providing

[0076] 64 Feeding

[0077] 66 Feeding

[0078] 68 Condensing

[0079] 70 Regulating