Method and system for cooling a fuel cell

Abstract

The present development relates to a method and a system (10) for cooling a fuel cell (30) comprising: - a coolant circuit (11) which can be thermally coupled to the fuel cell (20), - a collector (28) connected to an exhaust gas line (24) of the fuel cell (20) for capturing and / or collecting a reaction product escaping from the fuel cell during operation of the fuel cell (20), - a heat exchanger (30) which can be supplied with the reaction product and which is thermally coupled to the coolant circuit (11).

Description

Technical area

[0001] The present development relates to a method and a system for cooling a fuel cell, in particular a motor vehicle fuel cell. background

[0002] To operate a fuel cell in a motor vehicle, it is typically necessary to operate the fuel cell within a specified temperature range. The electrochemical reactions occurring in fuel cells not only provide usable electrical energy, but also release waste heat, which must be removed from the fuel cell area in a controlled manner by a separate cooling circuit or cooling system.

[0003] For example, DE 198 59 504 B4 discloses a fuel cell system which, among other things, comprises a plurality of nozzle devices which are mounted on side walls of an air inlet manifold of the fuel cell and are designed to inject water into the inlet manifold.

[0004] Given the limited installation space available for a fuel cell cooling system in the automotive sector, it is desirable to provide an improved fuel cell cooling system characterized by a particularly compact design and particularly efficient operation. The particular objective of this development is to increase the cooling performance of a fuel cell cooling system without having to increase the dimensions of a radiator or heat exchanger in an existing coolant circuit. Advantageous designs

[0005] This object is achieved with a system for cooling a fuel cell, a motor vehicle, and a method for cooling a fuel cell according to the features of the independent patent claims. Advantageous embodiments are the subject of dependent patent claims.

[0006] In a first aspect, a system for cooling a fuel cell is provided. The system comprises a coolant circuit that can be thermally coupled to a fuel cell, as well as a collector connected to an exhaust line of the fuel cell for capturing and / or collecting a reaction product escaping from the fuel cell during operation. The cooling system further comprises a heat exchanger that can be supplied with the reaction product and is thermally coupled to the coolant circuit.

[0007] In this way, the reaction product inevitably generated during fuel cell operation can be used directly to cool the coolant circuit, or rather, the coolant or refrigerant flowing through the coolant circuit. Typically, the heat exchanger is fluidly coupled to the collector, so that the reaction product escaping from the fuel cell during fuel cell operation, such as water or steam, can be used to cool the coolant circuit via the heat exchanger.

[0008] The collector serves to capture and / or collect the reaction product that inevitably arises during operation of the fuel cell, such as water vapor or water. The reaction product can arise at a comparatively low temperature during operation of the fuel cell, or it can condense in the area of ​​the collector and inevitably cool down to a predetermined temperature level during operation of the fuel cell, for example due to the ambient temperature of the collector. The reaction product captured or accumulating in the collector can then be thermally coupled to the coolant circuit via the heat exchanger, in order to extract thermal energy from the coolant circuit or to transfer thermal energy from the coolant circuit to the reaction product. The reaction product can then be released from the heat exchanger into the environment, for example.

[0009] In particular, it is provided that the reaction product to be released from the collector via the heat exchanger and finally from the heat exchanger to the environment absorbs thermal energy from the coolant circuit in the area of ​​the heat exchanger and thus removes thermal energy from the coolant circuit, whereby the temperature of the coolant or refrigerant flowing through the coolant circuit can be reduced.

[0010] In this way, other heat exchangers in the coolant circuit, such as an additional heat exchanger designed as a radiator, can be dimensioned more slenderly in terms of their performance, which in particular also allows the use of heat exchangers of a smaller size than before. As a result, the cooling system for the fuel cell can be reduced in its overall dimensions or geometric dimensions and is particularly suitable for use in small cars or compact motor vehicles.

[0011] By using the reaction product arising during operation of the fuel cell to cool the fuel cell, and thus to cool the associated coolant circuit, the efficiency of the cooling system can be increased while at the same time its geometric dimensions or its geometric dimensioning can be reduced.

[0012] According to a further embodiment of the cooling system, it comprises a connecting line that connects the heat exchanger to the collector and by means of which the reaction product can be transferred or transferred from the collector to the heat exchanger. The connecting line is designed, in particular, as a fluid-connecting line. In particular, the reaction product captured or collected in the collector can be in a liquid state and can be conveyed via the connecting line in a liquid state from the collector to the heat exchanger. There, the liquid reaction product can be further heated, possibly even evaporated, for example by absorbing thermal energy from the coolant circuit.

[0013] According to a further embodiment of the cooling system, the heat exchanger is designed to evaporate the reaction product supplied via the collector. In particular, it is provided that the reaction product supplied to the heat exchanger via the collector and, if applicable, via the connecting line during operation of the fuel cell evaporates in the region of the heat exchanger. In this way, the evaporation enthalpy of the reaction product can be used, in particular, to extract thermal energy from the coolant circuit.

[0014] Utilizing the evaporation enthalpy of the reaction product proves to be extremely efficient for cooling the coolant circuit. Evaporating the reaction product from the liquid state to the gaseous state typically requires a comparatively large amount of thermal energy, which can be extracted from the coolant circuit in this way.

[0015] According to a further embodiment of the cooling system, the heat exchanger has a reservoir for the reaction product supplied via the collector. The reservoir serves, in particular, as an evaporation reservoir. The reaction product collected in the reservoir of the heat exchanger can transform from the liquid state to the gaseous state and escape from the reservoir in the gas phase or as a gaseous reaction product, typically escaping into the ambient air.

[0016] The heat exchanger reservoir is typically in thermal contact with the coolant circuit. In this way, thermal energy can be transferred from the coolant circuit to the reservoir and ultimately to the reaction product located in the heat exchanger reservoir. This energy transfer can lead to the evaporation of the reaction product located in the reservoir, which ultimately allows thermal energy to be transferred particularly efficiently from the coolant circuit into the cooling system provided here, in particular into the heat exchanger reservoir, and ultimately from there into the reaction product that is typically to be evaporated.

[0017] According to a further embodiment of the cooling system, the heat exchanger has an outlet for the vaporized reaction product. The outlet can be coupled to the ambient atmosphere or implemented as an outlet opening into the ambient atmosphere. In this way, the vaporized reaction product produced in the heat exchanger, typically in the reservoir of the heat exchanger, can escape to the environment through the outlet.

[0018] According to a further embodiment, the outlet of the heat exchanger has a valve by means of which a flow through the outlet can be regulated and / or controlled. The valve can be used to regulate and / or control the outflow rate of the gaseous reaction product through the outlet and thus out of the heat exchanger. Furthermore, the valve can be used to throttle or block the inflow of ambient air into the heat exchanger, thereby ensuring, among other things, that only gases arising from the interior of the heat exchanger reservoir or the gaseous reaction product can flow unidirectionally through the outlet toward the environment.

[0019] According to a further embodiment, the valve provided in or at the outlet has a check valve. The valve can in particular also be designed as a so-called check valve and block any inflow into the heat exchanger. In other words, the valve designed as a check valve in the region of the outlet of the heat exchanger reservoir can ensure that only a gaseous medium can flow from the interior of the heat exchanger through the outlet to the outside, but not into the heat exchanger. In this way, a unidirectional gas flow from the interior of the heat exchanger to the environment can be ensured, thus ensuring that only a gaseous medium can escape from the heat exchanger and not enter it.

[0020] According to a further embodiment, the outlet is fluidically coupled to a pump, by means of which the pressure inside the heat exchanger can be reduced relative to the ambient pressure. The pump can be implemented, in particular, as a suction pump or even as a so-called vacuum pump, so that the pressure level inside the heat exchanger, in particular inside the reservoir of the heat exchanger, can be adjusted or regulated to a range below the ambient air pressure.

[0021] The reduction of the pressure inside the heat exchanger enables the liquid reaction product to evaporate inside the heat exchanger, i.e. in the reservoir of the heat exchanger at a comparatively low temperature.

[0022] If the reaction product is water, for example, the evaporation of the water supplied to the heat exchanger via the collector can be reduced to an evaporation temperature well below 100 °C by reducing the pressure in the heat exchanger's reservoir. In this way, the cooling performance of the cooling system can be further improved.

[0023] In particular, the pump can be provided and / or implemented in combination with the check valve. The pump can reduce the vapor or gas pressure inside the heat exchanger. The check valve can ensure that only gaseous medium escapes from the reservoir or heat exchanger through the outlet toward the suction pump, but cannot flow back into the reservoir due to the higher ambient air pressure.

[0024] According to a further aspect, the present development finally relates to a motor vehicle with a fuel cell and a cooling system as described above. The cooling system's coolant circuit is thermally coupled to the fuel cell. The collector of the cooling system is connected to the fuel cell's exhaust line for capturing and / or collecting the reaction product escaping from the fuel cell during operation. Finally, the heat exchanger thermally coupled to the cooling circuit can be supplied with the reaction product that accrues in or at the collector.

[0025] The heat exchanger is typically supplied with heat via a connecting line that runs between the heat exchanger and the collector. The reaction product can be transported by gravity or by using a separate pump. The motor vehicle has the previously described cooling system for the fuel cell. Therefore, all features, advantages, and possible applications described above with regard to the cooling system also apply equally to the motor vehicle, and vice versa.

[0026] According to a further aspect, the present development further relates to a method for cooling a fuel cell, for example a fuel cell of a motor vehicle, using a previously described cooling system. The method comprises the steps of collecting the reaction product escaping from the fuel cell during operation of the fuel cell and applying the previously collected or trapped reaction product to the heat exchanger thermally coupled to the coolant circuit. In particular, the method can be implemented or carried out using a previously described cooling system and / or using a previously described motor vehicle. In this respect, all features, advantages, and possible applications previously described with regard to the cooling system and / or the motor vehicle also apply equally to the method for cooling the fuel cell; and vice versa. Short description of the characters

[0027] Further objects, features, and advantageous applications of the cooling system, the motor vehicle, and the method for cooling a fuel cell are explained in the following detailed description with reference to the drawings. Fig. 1 a schematic representation of a motor vehicle with a fuel cell, Fig. 2 a block diagram of an embodiment of a cooling system for the fuel cell, Fig. 3 is a block diagram of another embodiment of a cooling system for the fuel cell, and Fig. 4 a flow diagram of the process for cooling the fuel cell. Detailed description

[0028] The Fig. 1, the motor vehicle 1 shown only schematically comprises a self-supporting vehicle body 2 and an interior 3 functioning as a passenger cell. The motor vehicle 1 further comprises a Fig. 2 and Fig. 3 only schematically indicated fuel cell 20 as well as a cooling system 10 thermally coupled thereto, of which two different embodiments are shown in the Fig. 2 and Fig. 3 are shown using the respective block diagrams. The cooling system 10 each has a coolant circuit 11. The coolant circuit 11 comprises a pump 12, by means of which a coolant or refrigerant can be pumped or otherwise circulated through the coolant lines 14 of the coolant circuit 11. The fuel cell 20, and thus the fuel cell stack, has an inlet 21 for the coolant or refrigerant. The fuel cell 20 further has an outlet 22 for the coolant or refrigerant heated in the region of the fuel cell 20. The inlet 21 and the outlet 22 are components of the coolant line 14 forming the coolant circuit 11.

[0029] The coolant line 14 has a heat exchanger 15, configured approximately as a radiator, by means of which thermal energy can be released into the ambient air. The heat exchanger 15 can be implemented as a type of water cooler. The heat exchanger 15 can, in particular, be provided with one or more fans to effect heat exchange with the ambient air even during operating states of the motor vehicle 1 in which the motor vehicle 1 is moving at low speed or in which the motor vehicle remains stationary.

[0030] The heat exchanger 15 can be short-circuited as needed by means of a valve 17, such as a three-way valve, via a bypass line 16, thus fluidically disconnecting it from the coolant circuit 11. With the valve in the appropriate position, the refrigerant flows past the heat exchanger 15 through the bypass line 16, rather than via the heat exchanger 15.

[0031] The cooling system 10 further comprises a heat exchanger 30, the inlet 31 of which is in fluid communication with the outlet 22 of the fuel cell 20 and the outlet 32 ​​of which is in flow communication with the fluid-conveying pump 12 via the coolant line 14, possibly also via the bypass line 16, and finally is fluidly coupled again to the inlet 21 of the fuel cell 20 via the pump 12.

[0032] In addition to the inlet 31 and the outlet 32, the heat exchanger 30 has a reservoir 35 which is fluidically separated therefrom and which can be filled with a reaction product of the fuel cell 20 via an inlet 36 of the heat exchanger 30.

[0033] The reservoir 35 of the heat exchanger 30 further has an outlet 38, through which the reaction product in the reservoir can be drained from the reservoir 35 as needed, for example, via an outlet valve 39. The coolant line 14 of the coolant circuit 11 can pass through the heat exchanger 30, and in particular its reservoir 35. The inlet 31 and outlet 32 ​​are typically integral parts of the coolant line 14.

[0034] The coolant line 14 can, in particular, run through the reservoir 35 and, to this extent, be thermally coupled to the reaction product located in the reservoir 35. The reaction product can typically be removed from the fuel cell 20 via an exhaust line 24. It is a reaction product of the reaction gases supplied to the fuel cell via the two media inlets 25, 26, which react electrochemically with each other to produce the reaction product in the fuel cell 20 or in the fuel cell stack, releasing electrical energy.

[0035] The reaction product arising via the exhaust line 24 can be captured or collected via a collector 28. In the area of ​​the collector 28, the reaction product, which may flow out of the fuel cell 20 in gaseous form via the exhaust line 24, can be condensed and collected in condensed or liquid form in the collector 28.

[0036] The reaction product accumulating in or at the collector can be fed to the heat exchanger 30 via a connecting line 33, so that the reaction product, typically fed to the heat exchanger 30 in liquid form, can be heated in the heat exchanger 30, particularly in the reservoir 35 of the heat exchanger 30, and optionally re-evaporated. The connecting line 33 can also be provided with a pump 37 to enable the reaction product collected in the collector 28 to be fed to the heat exchanger 30 in a controlled manner.

[0037] The heat exchanger 30 typically has an outlet 34 through which the gaseous reaction product heated in the heat exchanger 30 can escape into the environment.

[0038] Because the heat exchanger 30 can be supplied with the liquid reaction product and because the heat exchanger 30 is thermally coupled to the coolant line 14 or to the coolant circuit 11, the evaporation enthalpy of the reaction product can be used, in particular by evaporating the reaction product in the heat exchanger 30, to extract thermal energy from the coolant circuit 11.

[0039] At the Fig. The embodiment shown in Figure 3 differs from that shown in Fig. 2, it is provided that the outlet 34 of the heat exchanger 30 is not directly connected to the ambient atmosphere, but that the outlet 34 is connected to a pump 42 via a valve 40, which can typically be designed as a check valve 41.

[0040] The pump 42 can, in particular, be implemented as a vacuum pump 43, so that a gas pressure or pressure level below atmospheric pressure can be set inside the reservoir 35 of the heat exchanger. In this way, the boiling temperature or evaporation temperature of the reaction product in the heat exchanger 30 can be lowered, thereby reducing the overall temperature level in the heat exchanger 30.

[0041] This makes it possible, for example, to cool the temperature of the coolant circulating through the coolant circuit 11 to a temperature level well below 100°C, which can be advantageous for the operation of polymer electrolyte membrane fuel cells, for example.

[0042] In particular, the temperature in the coolant circuit 11 can be adjusted to a predetermined temperature level for the respective fuel cell by appropriate pressure regulation in the reservoir 35 of the heat exchanger 30, or can be set to a predetermined temperature level or a temperature window, or regulated accordingly. In this respect, the cooling system can be implemented for a wide variety of fuel cell types, some of which operate at different temperatures. Thus, the cooling system for fuel cells provided here can be universally implemented and used for a wide variety of fuel cell types and types. It can be used, for example, for alkaline fuel cells, polymer electrolyte membrane fuel cells, direct methanol fuel cells, or phosphoric acid fuel cells.

[0043] In Fig.Finally, Figure 4 shows a flow diagram of the method for cooling a fuel cell 20. Here, in a first step 100, reaction products escaping from the fuel cell during operation of the fuel cell 20, such as water vapor or water, are collected. The reaction products generated during operation of the fuel cell can be collected, in particular, using the collector of the previously described cooling system.

[0044] In a subsequent step 102, the reaction product collected and / or generated during operation of the fuel cell is fed to the heat exchanger of the cooling system, which is thermally coupled to the coolant circuit of the fuel cell.

[0045] This allows thermal energy to be transferred from the coolant circuit to the reaction product. The reaction product can, in particular, evaporate from the liquid to the gaseous state and ultimately escape from the heat exchanger, particularly from the outlet of a reservoir of the heat exchanger, into the environment.

[0046] The illustrated embodiments merely show possible configurations of the development, for which numerous further variants are conceivable within the scope of the development. The exemplary embodiments shown are in no way to be interpreted as limiting the scope, applicability, or configuration options of the development. This description merely shows the person skilled in the art one or several possible implementations of an exemplary embodiment. Thus, a wide variety of modifications can be made to the function and arrangement of the described elements without departing from the scope of protection defined by the following claims or their equivalents. List of reference symbols 1 motor vehicle 2 Body 3 Interior 10 Cooling system 11 Coolant circuit 12 Pump 14 Coolant line 15 heat exchangers 16 Bypass line 17 Valve 20 fuel cells 21 Inlet 22 Procedure 24 exhaust pipe 25 Media supply 26 Media supply 28 collectors 30 heat exchangers 31 Inlet 32 Process 33 connecting line 34 Outlet 35 Reservoir 36 Entrance 37 Pump 38 Outlet 39 Exhaust valve 40 valve 41 Check valve 42 Pump 43 Vacuum pump QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 198 59 504 B4

[0003]

Claims

[1] System (10) for cooling a fuel cell (20) comprising: - a coolant circuit (11) which can be thermally coupled to the fuel cell (20), - a collector (28) connected to an exhaust gas line (24) of the fuel cell (20) for capturing and / or collecting a reaction product escaping from the fuel cell during operation of the fuel cell (20), - a heat exchanger (30) which can be supplied with the reaction product and which is thermally coupled to the coolant circuit (11). [2] System (10) according to claim 1, further comprising a connecting line (33) which connects the heat exchanger (30) to the collector (28) and by means of which the reaction product can be transferred from the collector (28) to the heat exchanger (30). [3] System (10) according to one of the preceding claims, wherein the heat exchanger (30) is designed to evaporate the reaction product supplied via the collector (28). [4] System (10) according to one of the preceding claims, wherein the heat exchanger (30) has a reservoir (35) for the reaction product that can be supplied via the collector (28). [5] System (10) according to any one of the preceding claims, wherein the heat exchanger (30) has an outlet (34) for the vaporized reaction product. [6] System (10) according to claim 5, wherein the outlet (34) has a valve (40) by means of which a flow through the outlet (34) can be regulated and / or controlled. [7] System (10) according to one of the preceding claims 5 or 6, wherein the valve (40) comprises a check valve (41) or is designed as a check valve (41) and blocks an inflow into the heat exchanger (30). [8] System (10) according to one of the preceding claims 5 to 7, wherein the outlet (34) is fluidically coupled to a pump (42) by means of which a pressure inside the heat exchanger (30) can be reduced compared to the ambient pressure. [9] Motor vehicle (1) with a fuel cell (20) and with a system (10) according to one of the preceding claims, the coolant circuit (11) of which is thermally coupled to the fuel cell (20) and the collector (28) of which is connected to the exhaust line (24) of the fuel cell (20) for capturing and / or collecting the reaction product escaping from the fuel cell (20) during operation of the fuel cell (20), and the heat exchanger (30) of which is capable of being supplied with the reaction product is thermally coupled to the coolant circuit (11). [10] Method for cooling a fuel cell (20) by means of a system (10) according to one of the preceding claims 1 to 8, comprising the following steps: - collecting the reaction product escaping from the fuel cell during operation of the fuel cell (20), - Applying the collected reaction product to the heat exchanger (30) thermally coupled to the coolant circuit (11).

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