A gas hydrate-based fuel cell system and method of operation

Abstract

The application provides a gas hydrate-based fuel cell system and a working method, wherein the gas hydrate can store fuel gas in a solid state, is safer and more reliable than gaseous or liquid fuel gas storage, has a higher fuel gas storage capacity per unit volume, and has a milder fuel gas storage condition; when the fuel gas is released, the gas hydrate is decomposed due to phase change to release a large amount of cold energy, which can provide an adequate and effective cold source for fuel cell thermal management; a part of water is generated after the decomposition of the gas hydrate, which can be used for humidifying the fuel cell; when the air inlet temperature is higher than the fuel cell stack temperature, the part of water can be used for cooling the air inlet due to the lower temperature; when the air inlet temperature is lower than the fuel cell stack temperature, the part of water can be used for cooling the fuel cell; after absorbing the waste heat of the fuel cell, the temperature of the part of water is increased, which can be used for preheating the air inlet, fully utilizes the system waste heat, and realizes integrated control of fuel cell fuel gas supply and storage, thermal management, air temperature adjustment and humidification.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a fuel cell system and its operating method based on gas hydrates. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] A fuel cell is an energy conversion device that converts the chemical energy of fuel into electrical energy through an electrochemical reaction. Compared with traditional power generation methods, fuel cells have many advantages such as high power generation efficiency, good environmental compatibility, small footprint, and wide availability of fuel. Currently, fuel cells have been applied in many fields such as fuel cell vehicles, aerospace, marine vessels, distributed power generation, home power, data center power, mobile power, replacement power for small-power electronic devices, and power supply for military equipment.

[0004] The inventors discovered that in order to ensure the stable and efficient operation of fuel cells, fuel cell systems often require multiple auxiliary functional modules, such as gas supply and storage modules, thermal management modules, air temperature control modules, and humidification modules. However, traditional fuel cell systems often consider implementing these functional modules separately, which leads to problems such as high system complexity, large space occupation, and low system energy efficiency, hindering the large-scale commercial application of fuel cells. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fuel cell system and operating method based on gas hydrates. Addressing the four requirements of fuel cells—fuel gas, thermal management, air temperature regulation, and humidification—this invention fully utilizes the three characteristics of gas hydrates: gas storage capacity, cooling capacity, and moisture content. This achieves integrated control of fuel cell gas supply and storage, thermal management, air temperature regulation, and humidification.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a fuel cell system based on gas hydrates.

[0008] A fuel cell system based on gas hydrates includes at least: a gas hydrate storage tank, a water bath jacket, an ejector, an ejector, a fuel cell stack, a fuel gas supply pipeline, a cryogenic liquid pipeline, a high-temperature liquid pipeline, and a water splitting pipeline;

[0009] The gas hydrate storage tank is connected to the fuel gas inlet of the fuel cell stack via a fuel gas supply pipeline. The fuel gas supply pipeline is equipped with an ejector and an ejector. The fuel gas outlet of the fuel cell stack is connected to the ejector via a first outlet pipeline.

[0010] The gas hydrate storage tank is located inside the water bath jacket. The cooling medium outlet and cooling medium inlet of the water bath jacket are connected through a cryogenic liquid pipeline. A part of the cryogenic liquid pipeline passes through the first heat exchanger.

[0011] The cooling medium outlet and cooling medium inlet of the fuel cell stack are connected by a high-temperature liquid pipeline, a part of which passes through the first heat exchanger.

[0012] The gas hydrate storage tank is connected to the cooling water inlet of the fuel cell stack via a decomposition water pipeline, and the cooling water outlet of the fuel cell stack is connected to the water outlet pipeline, which passes through the humidifier and the second heat exchanger in sequence.

[0013] The air intake duct is connected to the air intake port of the fuel cell stack, and the air intake duct passes through the air compressor, the second heat exchanger and the humidifier in sequence.

[0014] A first deionizer is installed on the water decomposition pipeline. A first pipeline switching element is installed on the pipe section between the first deionizer and the cooling water inlet of the fuel cell stack. The pipe section between the first deionizer and the first pipeline switching element is connected to the outlet pipeline through a connecting pipeline. A second pipeline switching element is installed on the connecting pipeline.

[0015] As a further limitation of the first aspect of the present invention, a third pipeline switching element is provided on the fuel gas supply pipeline between the gas hydrate storage tank and the injector.

[0016] As a further limitation of the first aspect of the present invention, the fuel gas outlet of the fuel cell stack is connected to the section between the ejector and the fuel gas inlet of the fuel cell stack via a second outlet pipeline, and a fuel gas circulation pump is provided on the second outlet pipeline.

[0017] As a further limitation of the first aspect of the invention, a first circulation pump is provided on the cryogenic liquid pipeline.

[0018] As a further limitation of the first aspect of the present invention, a second circulation pump and a second deionizer are provided on the high-temperature liquid pipeline.

[0019] As a further limitation of the first aspect of the present invention, a fourth pipeline switching element and a water pump are provided on the water decomposition pipeline, and the fourth pipeline switching element and the water pump are sequentially arranged on the pipeline section between the gas hydrate storage tank and the first deionizer.

[0020] As a further definition of the first aspect of the present invention, the first pipeline switching element is a first valve, and the second pipeline switching element is a second valve.

[0021] As a further limitation of the first aspect of the present invention, a check valve is provided on the outlet pipe at the cooling water outlet of the fuel cell stack.

[0022] As a further limitation of the first aspect of the present invention, the exhaust port of the fuel cell stack is connected to an exhaust pipe, and an exhaust valve is provided on the exhaust pipe; the water outlet pipe passes through the humidifier and the second heat exchanger in sequence, and then discharges through the drain valve.

[0023] A second aspect of the present invention provides a method for operating a fuel cell system based on gas hydrates.

[0024] A method for operating a fuel cell system based on gas hydrates includes the following steps:

[0025] The fuel gas hydrate in the gas hydrate storage tank is decomposed by heating in a water bath jacket to release fuel gas. The fuel gas flows through the fuel gas supply pipeline and enters the fuel cell stack after being pressure regulated by the injector. The unreacted fuel gas leaves the fuel cell stack and is reintroduced into the fuel gas supply pipeline through the ejector or fuel gas circulation pump, so that it can re-enter the fuel cell stack for reaction.

[0026] The fuel gas hydrate in the gas hydrate storage tank undergoes a phase change decomposition after being heated by a water bath jacket, releasing cold energy into the water bath jacket. The cooling medium in the water bath jacket flows through the cryogenic liquid pipeline under the drive of the first circulation pump and enters the first heat exchanger. At the same time, the cooling medium in the high-temperature liquid pipeline, driven by the second circulation pump, carries away the heat of the fuel cell stack and enters the first heat exchanger. The hot and cold fluids exchange heat in the first heat exchanger.

[0027] The low-temperature decomposition water produced after the decomposition of gas hydrate in the gas hydrate storage tank flows through the decomposition water pipeline and the first deionizer under the drive of the water pump. At the same time, the air is compressed by the air compressor and flows into the second heat exchanger.

[0028] If the air temperature in the second heat exchanger is lower than the fuel cell stack temperature, the first valve opens and the second valve closes. The low-temperature decomposed water in the decomposed water pipeline enters the fuel cell stack to cool it and absorb its heat. Then, the heated decomposed water flows through the check valve and humidifier and enters the second heat exchanger to exchange heat with the air intake, thereby achieving the effect of preheating the air.

[0029] If the air temperature in the second heat exchanger is higher than the fuel cell stack temperature, the first valve closes and the second valve opens. The low-temperature decomposed water in the decomposed water pipeline flows directly through the humidifier and enters the second heat exchanger to cool the air intake. After the air intake flows through the second heat exchanger, it is humidified by the decomposed water in the humidifier and then enters the fuel cell stack. Unreacted air is discharged through the exhaust valve, and the decomposed water flows through the second heat exchanger and is discharged through the drain valve.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. This invention innovatively proposes a fuel cell system and operating method based on gas hydrates. Gas hydrates can store fuel gas in a solid form, which is safer and more reliable than gaseous and liquid gas storage, and has a higher gas storage capacity per unit volume and milder gas storage conditions.

[0032] 2. This invention innovatively proposes a fuel cell system and operating method based on gas hydrates. While releasing fuel gas, the gas hydrates release a large amount of cooling energy due to phase change decomposition, which can provide a sufficient and effective cooling source for fuel cell thermal management.

[0033] 3. This invention innovatively proposes a fuel cell system and operating method based on gas hydrates. After the gas hydrates decompose, a portion of water is generated, which can be used to humidify the fuel cell. When the air intake temperature is higher than the fuel cell stack temperature, this portion of water, due to its lower temperature, can be used to cool the air intake. When the air intake temperature is lower than the fuel cell stack temperature, this portion of water can be used to cool the fuel cell. After absorbing the waste heat of the fuel cell, the temperature of this portion of water increases, which can be used to preheat the air intake, making full use of the system's waste heat.

[0034] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 This is a schematic diagram of a fuel cell system based on gas hydrates provided in Embodiment 1 of the present invention;

[0037] Among them, 1-gas hydrate storage tank, 2-water bath jacket, 3-fuel gas supply pipeline, 4-first pipeline switching element, 5-ejector, 6-ejector, 7-fuel gas circulation pump, 8-fuel cell stack, 9-cryogenic liquid pipeline, 10-first circulation pump, 11-first heat exchanger, 12-high temperature liquid pipeline, 13-second circulation pump, 14-first deionizer, 15-water splitting pipeline, 16-second pipeline switching element, 17-water pump, 18-second deionizer, 19-third pipeline switching element, 20-fourth pipeline switching element, 21-check valve, 22-humidifier, 23-second heat exchanger, 24-drain valve, 25-air compressor, 26-exhaust valve. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0042] Example 1:

[0043] like Figure 1 As shown, Embodiment 1 of the present invention provides a fuel cell system based on gas hydrates. The gas hydrate storage tank 1 is used to store fuel gas hydrates, including but not limited to hydrogen hydrates, methane hydrates and ethane hydrates.

[0044] First, gas hydrates can store fuel gas in a solid form, which is safer and more reliable than gaseous or liquid gas storage, and has a higher gas storage capacity per unit volume and milder storage conditions.

[0045] Secondly, while releasing fuel gas, the gas hydrate will release a large amount of cold energy due to phase change decomposition, which can provide a sufficient and effective cold source for fuel cell thermal management.

[0046] Finally, the decomposition of gas hydrates produces some water, which can be used to humidify the fuel cell. Furthermore, when the air intake temperature is higher than the fuel cell stack temperature, this water, due to its lower temperature, can be used to cool the air intake; when the air intake temperature is lower than the fuel cell stack temperature, this water can be used to cool the fuel cell; after absorbing waste heat from the fuel cell, this water's temperature rises, which can be used to preheat the air intake, making full use of the system's waste heat.

[0047] In this embodiment, the gas hydrate is a non-stoichiometric crystalline compound formed by certain gases (such as hydrogen, methane, ethane, carbon dioxide, etc.) and water. Macroscopically, the properties and appearance of gas hydrates are similar to ice; microscopically, water molecules (the host molecules) are bonded together by hydrogen bonds to form a cage-like structure, which uses van der Waals forces to trap gas molecules (guest molecules) at the center of the cage-like structure. Currently, gas hydrates have demonstrated their important role in many fields, such as clean energy supply, gas flow safety assurance, gas storage and transportation, cold storage, carbon dioxide sequestration, gas separation, and solution concentration.

[0048] More specifically, the system described in this embodiment includes:

[0049] The gas hydrate storage tank 1 is connected to the fuel gas inlet of the fuel cell stack 8 through the fuel gas supply pipeline 3. The fuel gas supply pipeline 3 is equipped with an injector 5 and an ejector 6. The fuel gas outlet of the fuel cell stack 8 is connected to the ejector 6 through the first outlet pipeline.

[0050] The gas hydrate storage tank 1 is located inside the water bath jacket 2. The cooling medium outlet and cooling medium inlet of the water bath jacket 2 are connected through the cryogenic liquid pipeline 9. A part of the cryogenic liquid pipeline 9 passes through the first heat exchanger 11.

[0051] The cooling medium outlet and cooling medium inlet of the fuel cell stack 8 are connected through a high-temperature liquid pipeline 12, and a part of the high-temperature liquid pipeline 12 passes through the first heat exchanger 11.

[0052] The gas hydrate storage tank 1 is connected to the cooling water inlet of the fuel cell stack 8 through the decomposition water pipeline 15, and the cooling water outlet of the fuel cell stack 8 is connected to the water outlet pipeline. The water outlet pipeline passes through the humidifier 22 and the second heat exchanger 23 in sequence.

[0053] The air intake pipe is connected to the air intake port of the fuel cell stack 8, and the air intake pipe passes through the air compressor 25, the second heat exchanger 23 and the humidifier 22 in sequence.

[0054] A first deionizer 14 is provided on the water decomposition pipeline 15. A first pipeline switch element 4 is provided on the pipeline section between the first deionizer 14 and the cooling water inlet of the fuel cell stack 8. The pipeline section between the first deionizer 14 and the first pipeline switch element 4 is connected to the water outlet pipeline through a connecting pipeline. A second pipeline switch element 16 is provided on the connecting pipeline.

[0055] As an optional implementation of this embodiment, a third pipeline switching element 19 is provided on the fuel gas supply pipeline 3 between the gas hydrate storage tank 1 and the injector 5.

[0056] As an optional implementation in this embodiment, the fuel gas outlet of the fuel cell stack 8 is connected to the section between the ejector 6 and the fuel gas inlet of the fuel cell stack 8 through a second outlet pipeline, and a fuel gas circulation pump 7 is provided on the second outlet pipeline.

[0057] As an optional implementation in this embodiment, a first circulation pump 10 is provided on the cryogenic liquid pipeline 9.

[0058] As an optional implementation of this embodiment, a second circulation pump 13 and a second deionizer 18 are provided on the high-temperature liquid pipeline 12.

[0059] As an optional implementation of this embodiment, the water decomposition pipeline 15 is provided with a fourth pipeline switch element 20 and a water pump 17, which are sequentially arranged on the pipeline section between the gas hydrate storage tank 1 and the first deionizer 14.

[0060] As an optional implementation of this embodiment, the first pipeline switching element 4 is the first valve, the second pipeline switching element 16 is the second valve, the third pipeline switching element 19 is the third valve, and the fourth pipeline switching element 20 is the fourth valve.

[0061] In this embodiment, the first valve, the second valve, the third valve, and the fourth valve are all solenoid valves. It is understood that in some other implementations, the first valve, the second valve, the third valve, and the fourth valve may also be manual valves or other valves such as pneumatic valves. Those skilled in the art can choose according to the specific working conditions, which will not be elaborated here.

[0062] As an optional implementation in this embodiment, a check valve 21 is provided on the outlet pipe at the cooling water outlet of the fuel cell stack 8.

[0063] As an optional implementation in this embodiment, the exhaust port of the fuel cell stack 8 is connected to an exhaust pipe, and an exhaust valve 26 is provided on the exhaust pipe; the water outlet pipe passes through the humidifier 22 and the second heat exchanger 23 in sequence, and then discharges through the drain valve 24.

[0064] Example 2:

[0065] Embodiment 2 of the present invention provides a method for operating a fuel cell system based on gas hydrates, comprising:

[0066] The working process for achieving gas supply and storage functions includes:

[0067] The fuel gas hydrate in the gas hydrate storage tank 1 is heated and decomposed by the water bath jacket 2 to release fuel gas. The fuel gas flows through the fuel gas supply pipeline 3 and enters the fuel cell stack 8 after being regulated by the injector 5. The unreacted fuel gas leaves the fuel cell stack 8 and is reintegrated into the fuel gas supply pipeline 3 through the ejector 6 or the fuel gas circulation pump 7, and can re-enter the fuel cell stack 8 for reaction.

[0068] The process of implementing thermal management functions includes:

[0069] The fuel gas hydrate in the gas hydrate storage tank 1 undergoes phase change decomposition after being heated by the water bath jacket 2, releasing cold energy into the water bath jacket 2. The cooling medium in the water bath jacket 2 flows through the cryogenic liquid pipeline 9 under the drive of the first circulation pump 10 and enters the first heat exchanger 11. At the same time, the cooling medium in the high temperature liquid pipeline 12 carries away the heat of the fuel cell stack 8 under the drive of the second circulation pump 13 and enters the first heat exchanger 11. The hot and cold fluids exchange heat in the first heat exchanger 11.

[0070] The working process for achieving air temperature control and humidification functions includes:

[0071] After the gas hydrate in the gas hydrate storage tank 1 decomposes, a portion of low-temperature decomposition water is generated. This portion of water flows through the decomposition water pipeline 15 and the first deionizer 14 under the drive of the water pump 17. At the same time, air is compressed by the air compressor 25 and flows into the second heat exchanger 25.

[0072] If the air temperature in the second heat exchanger 23 is lower than the temperature of the fuel cell stack 8, the first pipeline switch element 4 is opened and the second pipeline switch element 16 is closed. The low-temperature decomposed water in the decomposed water pipeline 15 enters the fuel cell stack 8, cools it and absorbs its heat. Then, the heated decomposed water flows through the check valve 21 and the humidifier 22 and enters the second heat exchanger 23 to exchange heat with the air intake, thereby achieving the effect of preheating the air.

[0073] If the air temperature in the second heat exchanger 23 is higher than the temperature of the fuel cell stack 8, the first pipeline switch element 4 is closed and the second pipeline switch element 16 is opened. The low-temperature decomposed water in the decomposed water pipeline 15 flows directly through the humidifier 22 and enters the second heat exchanger 23 to cool the air intake. After the air intake flows through the second heat exchanger 23, it can be humidified by the decomposed water in the humidifier 22 and then enters the fuel cell stack 8. The unreacted air is discharged through the exhaust valve 26, and the decomposed water is discharged through the drain valve 24 after flowing through the second heat exchanger 23.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fuel cell system based on gas hydrates, characterized in that, It includes at least: a gas hydrate storage tank, a water bath jacket, an ejector, an ejector, a fuel cell stack, a fuel gas supply pipeline, a cryogenic liquid pipeline, a high-temperature liquid pipeline, and a decomposed water pipeline; The gas hydrate storage tank is connected to the fuel gas inlet of the fuel cell stack via a fuel gas supply pipeline. The fuel gas supply pipeline is equipped with an ejector and an ejector. The fuel gas outlet of the fuel cell stack is connected to the ejector via a first outlet pipeline. The gas hydrate storage tank is located inside the water bath jacket. The cooling medium outlet and cooling medium inlet of the water bath jacket are connected through a cryogenic liquid pipeline. A part of the cryogenic liquid pipeline passes through the first heat exchanger. The cooling medium outlet and cooling medium inlet of the fuel cell stack are connected by a high-temperature liquid pipeline, a part of which passes through the first heat exchanger. The gas hydrate storage tank is connected to the cooling water inlet of the fuel cell stack via a decomposition water pipeline, and the cooling water outlet of the fuel cell stack is connected to the water outlet pipeline, which passes through the humidifier and the second heat exchanger in sequence. The air intake duct is connected to the air intake port of the fuel cell stack, and the air intake duct passes through the air compressor, the second heat exchanger and the humidifier in sequence. A first deionizer is installed on the water decomposition pipeline. A first pipeline switching element is installed on the pipe section between the first deionizer and the cooling water inlet of the fuel cell stack. The pipe section between the first deionizer and the first pipeline switching element is connected to the outlet pipeline through a connecting pipeline. A second pipeline switching element is installed on the connecting pipeline.

2. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, A third pipeline switch element is installed on the fuel gas supply pipeline between the gas hydrate storage tank and the injector.

3. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, The fuel gas outlet of the fuel cell stack is connected to the section between the ejector and the fuel gas inlet of the fuel cell stack via a second outlet pipeline, and a fuel gas circulation pump is installed on the second outlet pipeline.

4. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, A first circulation pump is installed on the cryogenic liquid pipeline.

5. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, A second circulation pump and a second deionizer are installed on the high-temperature liquid pipeline.

6. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, The decomposed water pipeline is equipped with a fourth pipeline switch element and a water pump, which are sequentially installed on the pipeline section between the gas hydrate storage tank and the first deionizer.

7. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, The first pipeline switching element is the first valve, and the second pipeline switching element is the second valve.

8. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, A check valve is installed on the outlet pipe at the cooling water outlet of the fuel cell stack.

9. The fuel cell system based on gas hydrates as described in claim 1, characterized in that, The exhaust port of the fuel cell stack is connected to an exhaust pipe, which is equipped with an exhaust valve; the water outlet pipe passes through the humidifier and the second heat exchanger in sequence, and then discharges through the drain valve.

10. A method for operating a fuel cell system based on gas hydrates, characterized in that, Includes the following processes: The fuel gas hydrate in the gas hydrate storage tank is decomposed by heating in a water bath jacket to release fuel gas. The fuel gas flows through the fuel gas supply pipeline and enters the fuel cell stack after being pressure regulated by the injector. The unreacted fuel gas leaves the fuel cell stack and is reintroduced into the fuel gas supply pipeline through the ejector or fuel gas circulation pump, so that it can re-enter the fuel cell stack for reaction. The fuel gas hydrate in the gas hydrate storage tank undergoes a phase change decomposition after being heated by a water bath jacket, releasing cold energy into the water bath jacket. The cooling medium in the water bath jacket flows through the cryogenic liquid pipeline under the drive of the first circulation pump and enters the first heat exchanger. At the same time, the cooling medium in the high-temperature liquid pipeline, driven by the second circulation pump, carries away the heat of the fuel cell stack and enters the first heat exchanger. The hot and cold fluids exchange heat in the first heat exchanger. The low-temperature decomposition water produced after the decomposition of gas hydrate in the gas hydrate storage tank flows through the decomposition water pipeline and the first deionizer under the drive of the water pump. At the same time, the air is compressed by the air compressor and flows into the second heat exchanger. If the air temperature in the second heat exchanger is lower than the fuel cell stack temperature, the first valve opens and the second valve closes, allowing the low-temperature decomposed water in the decomposed water pipeline to enter the fuel cell stack, cool it, and absorb its heat. The heated decomposed water then flows through a check valve and a humidifier, and enters the second heat exchanger to exchange heat with the air intake, thereby achieving the effect of preheating the air. If the air temperature in the second heat exchanger is higher than the fuel cell stack temperature, the first valve closes and the second valve opens. The low-temperature decomposed water in the decomposed water pipeline flows directly through the humidifier and enters the second heat exchanger to cool the air intake. After the air intake flows through the second heat exchanger, it is humidified by the decomposed water in the humidifier and then enters the fuel cell stack. Unreacted air is discharged through the exhaust valve, and the decomposed water flows through the second heat exchanger and is discharged through the drain valve.

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