A thermal management system and working method of a proton exchange membrane fuel cell

Abstract

The present invention discloses a proton exchange membrane fuel cell thermal management system and a working method thereof. The fuel cell thermal management system comprises a fuel cell stack, an ultra-thin heat spreader, a water cooling module, a thermal insulation and heating module and a control module. A slot is provided on the bipolar plate of the fuel cell stack, the heat conduction section of the ultra-thin heat spreader is embedded in the slot, and the temperature control sections of two adjacent ultra-thin heat spreaders are respectively connected to the cooling module and the thermal insulation and heating module. The fuel cell thermal management system utilizes the temperature uniformity characteristics of the ultra-thin heat spreader and the characteristics of the composite phase change material for storing latent heat, and cooperates with the control module to achieve efficient thermal management of the fuel cell stack. The fuel cell thermal management system proposed in the present invention has the advantages of reliable and flexible system, uniform and stable battery temperature distribution, and efficient and energy-saving heat regulation.

Description

Technical Field

[0001] The present invention relates to the field of thermal management of proton exchange membrane fuel cells, and in particular to a thermal management system and a working method of proton exchange membrane fuel cells based on an ultra-thin vapor chamber and a composite phase change material. Background Art

[0002] Proton exchange membrane fuel cells are devices that directly convert the chemical energy of the reactants themselves into electrical energy. They have the characteristics of high energy density, low environmental pollution, abundant and renewable fuel, and have received widespread attention. They are hailed as the ultimate energy of the 21st century and have broad application prospects. In practical applications, 40% to 60% of the chemical energy of the fuel is converted into electrical energy, and most of the remaining energy is converted into thermal energy. If the heat cannot be discharged in time, the system temperature will continue to rise, and overheating will occur locally in a single cell or in a local area of ​​the stack, seriously affecting the normal operation of the fuel cell. When the temperature of the proton exchange membrane reaches above 80°C, its thermal stability and proton conductivity will decrease. In severe cases, the membrane will dehydrate, resulting in a sharp decrease in conductivity. When the temperature of the proton exchange membrane is higher than 130°C, the membrane will be irreversibly damaged, and local hot spots will cause membrane perforation, ultimately affecting the safety of the stack operation. At the same time, excessive battery temperature will also accelerate the attenuation of the catalyst.

[0003] Current proton exchange membrane fuel cell thermal management technology, such as patent application CN201810662690.5, discloses a liquid-cooled module for heat transfer and temperature equalization of high-power fuel cells, which consists of a fuel cell stack, a coolant flow channel, an ultra-thin temperature equalizing plate, a liquid storage tank, a circulating liquid pump and a heating device; the liquid storage tank, the circulating liquid pump and the heating device are connected in series in sequence through the coolant flow channel to form a heat transfer and temperature equalization circulation loop; the coolant flow channel passes through the condensing ends of the ultra-thin temperature equalizing plates of the fuel cell stacks arranged at intervals; ultra-thin temperature equalizing plates are respectively provided on both sides of the membrane electrode, and multiple membrane electrodes and ultra-thin temperature equalizing plates are alternately arranged; the cavity of the ultra-thin temperature equalizing plate is arranged in the shell, and extends out of the shell from at least one end of the shell, and it uses the temperature equalizing plate to transfer the temperature and uses the coolant for cooling or heating. Patent application CN201820980615.9 discloses a liquid-cooled device for heat transfer and temperature equalization of high current density fuel cells. These patented technologies do not focus on low-temperature startup, or use heated coolant for indirect heating, which will lead to defects in the real-time performance of the system and fail to recycle the heat generated by the battery stack. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a proton exchange membrane fuel cell thermal management system based on an ultra-thin heat spreader and a composite phase change material, which can ensure that the proton exchange membrane fuel cell stack is evenly within a suitable temperature range during operation, store heat to achieve rapid cold start of the stack, and prevent the stack from being damaged by local overtemperature, so as to optimize the thermal management of the proton exchange membrane fuel cell and improve its performance.

[0005] The present invention is achieved by at least one of the following technical solutions.

[0006] A proton exchange membrane fuel cell thermal management system based on an ultra-thin vapor chamber and a composite phase change material comprises a fuel cell stack, an ultra-thin vapor chamber, a water cooling module, a heat preservation and heating module and a control module.

[0007] The fuel cell stack comprises a plurality of single cells connected in series, each of the single cells comprises a membrane electrode and a bipolar plate, a slot is provided in the bipolar plate, the ultra-thin heat spreader is embedded in the slot of the bipolar plate, a bipolar plate end plate is provided on the outside of the fuel cell stack, and a temperature sensor is provided in the fuel cell stack;

[0008] The water cooling module and the heat preservation and heating module are respectively located on both sides of the battery stack, and two adjacent ultra-thin heat sinks are respectively connected to the water cooling module and the heat preservation and heating module;

[0009] The heat preservation and heating module comprises a heat preservation shell, a heating rod arranged in the heat preservation shell, and a phase change material;

[0010] The control module is connected to the water cooling module and the heat preservation and heating module, and is used to control the flow rate of the cooling fluid and the power of the heating rod.

[0011] Preferably, each ultra-thin heat spreader includes a heat conduction section and a temperature control section, wherein the heat conduction section is located inside the bipolar plate, and the temperature control section is connected to a water cooling module or a heat preservation and heating module. The temperature control section accounts for 15% to 20% of the overall area of ​​the ultra-thin heat spreader.

[0012] Preferably, the ultra-thin heat spreader includes an upper shell plate, a lower shell plate, a liquid wick, a support body and a working medium. The upper shell plate and the lower shell plate are sealed and supported by the support body to form a hollow cavity, and the working medium and the liquid wick are arranged in the hollow cavity.

[0013] Preferably, the working medium is a mixture of any one or more of methanol, ethanol, acetone, deionized water, ammonia and Freon.

[0014] Preferably, the upper shell plate and the lower shell plate are made of any one of copper, aluminum, copper alloy and aluminum alloy.

[0015] Preferably, the liquid absorbent core is a sintered copper powder column wire mesh composite liquid absorbent core, a sintered copper wire mesh woven belt composite liquid absorbent core or a sintered copper powder column wire mesh woven belt liquid absorbent core.

[0016] Preferably, the thickness of the ultra-thin heat spreader is 0.6-1 mm.

[0017] Preferably, the water cooling module includes an aluminum or aluminum alloy shell and an internal water flow cavity. A water inlet and a water outlet are respectively provided at both ends of the water cooling module. A valve is provided on the water inlet, and the valve is connected to the control module. A slot for embedding a heat spreader temperature control section is provided on the shell.

[0018] Preferably, the phase change material in the thermal insulation heating module is composed of 80-90% by mass of paraffin wax and 10-20% by mass of expanded graphite, wherein the melting point of the paraffin wax is between 60 and 80°C.

[0019] Preferably, the present invention provides a working method of the above-mentioned hydrogen fuel cell thermal management system based on the ultra-thin vapor chamber and the composite phase change material, comprising the following steps:

[0020] When the stack temperature T is lower than the first preset temperature T1, the phase change material of the heat preservation and heating module releases latent heat, and the latent heat is introduced into the fuel cell stack through the ultra-thin heat spreader to be used for heat preservation of the fuel cell stack;

[0021] The temperature sensor collects the temperature T of the fuel cell stack in real time. When the temperature T of the fuel cell stack is higher than the second preset temperature T2, the control module increases the water flow rate of the water cooling module to accelerate the cooling of the temperature control section of the ultra-thin heat sink, and the phase change material in the heat preservation and heating module absorbs and stores the heat of the fuel cell stack;

[0022] When the fuel cell stack is cold started, that is, when the temperature T inside the stack is lower than the first preset temperature T1, the phase change material in the thermal insulation and heating module releases heat to increase the temperature of the fuel cell stack, and the control module increases the heating power of the heating rod in the thermal insulation and heating module to increase the temperature of the ultra-thin heat sink temperature control section, and the temperature control section transfers heat to the heat conduction section to increase the temperature of the fuel cell stack.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] 1. Reliable and flexible system: The present invention uses ultra-thin heat sinks to control the temperature of the battery stack, without the need for cooling flow fields, which can effectively improve the space utilization of the battery stack and simplify the overall structure of the battery stack. At the same time, the system adopts a modular design, which is convenient for efficient control and fault monitoring. The system has a fast startup response capability, which can effectively reduce the failure rate of system operation, and each module can be replaced and upgraded;

[0025] 2. The temperature distribution of the battery stack is uniform and stable: the present invention makes full use of the excellent temperature distribution characteristics of the ultra-thin heat spreader, arranges the heat spreader on each single battery, avoids the appearance of local high temperature points, and realizes uniform temperature distribution in the battery stack;

[0026] 3. High efficiency and energy saving in heat regulation: Based on the working mode, the excellent temperature uniformity of the ultra-thin heat spreader is used to export or import heat from the battery stack. At the same time, the heat storage characteristics of the composite phase change material are used to recover and store heat at high temperature of the battery stack and release latent heat at low temperature, thereby reducing system energy consumption and realizing efficient and real-time stable regulation of the battery stack temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0028] Figure 1 An overall diagram of the proton exchange membrane fuel cell thermal management system provided by the present invention;

[0029] Figure 2 A schematic diagram of an overall explosion of a proton exchange membrane fuel cell thermal management system provided by the present invention;

[0030] Figure 3 A schematic diagram of a water cooling module provided by the present invention;

[0031] Figure 4 Schematic diagram of the heat preservation and heating module provided by the present invention;

[0032] Figure 5 This is a flow chart of the proton exchange membrane fuel cell thermal management system control method proposed by the present invention.

[0033] Among them, 1. bipolar plate end plate, 2. membrane electrode, 3. bipolar plate, 4. ultra-thin heat sink, 5. water cooling module, 6. thermal insulation and heating module. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes, and do not specifically refer to the order or sequence, nor are they used to limit the present invention. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0036] like Figures 1 to 4 As shown, the present invention proposes a proton exchange membrane fuel cell thermal management system, which includes a fuel cell stack, an ultra-thin heat sink 4, a water cooling module 5, a heat preservation and heating module 6 and a control module.

[0037] The fuel cell stack includes a plurality of single cells connected in series, each of the single cells includes a membrane electrode 2 and a bipolar plate 3, a slot is provided in the bipolar plate 3, the ultra-thin heat spreader 4 is embedded in the slot of the bipolar plate 3, a bipolar plate end plate 1 is provided on the outside of the fuel cell stack, and a temperature sensor is provided in the fuel cell stack.

[0038] In some embodiments of the present invention, the ultra-thin heat spreader 4 includes a heat conduction section and a temperature control section, the heat conduction section is inserted in the slot, the temperature control section is exposed to the battery stack, and two adjacent ultra-thin heat spreaders 4 are respectively connected to the water cooling module 5 and the heat preservation and heating module. The water cooling module 5 is located above the battery stack, and the heat preservation and heating module 6 is located below the battery stack. The temperature control sections of the two adjacent ultra-thin heat spreaders 4 are respectively exposed to the upper and lower parts of the battery stack, and are respectively inserted into the water cooling module 5 and the heating and heat preservation module 6.

[0039] The control module is connected to the water cooling module 5 and the heat preservation and heating module 6, and is used to control the flow rate of the cooling fluid and the power of the heating rod.

[0040] In some embodiments of the present invention, the temperature control section occupies 20% of the overall area of ​​the ultra-thin heat sink 4. The area proportion of the temperature control section is determined from the perspective of temperature control effect and saving materials and space. When the temperature control section accounts for 15% to 20%, it can save materials and space while ensuring the temperature control effect.

[0041] In some embodiments of the present invention, the heat-conducting section of the ultra-thin heat spreader 4 in contact with the battery stack is coated with thermal grease to reduce thermal resistance.

[0042] In some embodiments of the present invention, the ultra-thin heat spreader 4 includes an upper shell plate, a lower shell plate, a liquid wick, a support body and a working medium. The upper shell plate and the lower shell plate are connected and sealed on all sides by high-temperature brazing and supported by the support body to form a shell structure with a hollow cavity, and the working medium and the liquid wick are arranged in the hollow cavity.

[0043] In this embodiment, the upper shell plate and the lower shell plate are made of copper. The support body is a columnar structure made of copper like the shell, and the working medium is deionized water.

[0044] In some embodiments of the present invention, the liquid absorbent core is a sintered copper powder column wire mesh woven tape composite liquid absorbent core structure. The sintered copper powder column wire mesh woven tape liquid absorbent core has high production efficiency and low cost. At the same time, the high porosity makes it have better capillary performance, is less affected by gravity when used in the direction against gravity, and is conducive to the escape of bubbles and reduces the reflux resistance of the liquid working medium.

[0045] In some embodiments of the present invention, the support columns used by the ultra-thin heat sink 4 are arranged in a square matrix of cylindrical structures. The square arrangement can effectively reduce the shell plate collapse phenomenon and reduce the movement resistance of the internal steam.

[0046] In some embodiments of the present invention, the ultra-thin heat spreader 4 has a thickness of 0.6 mm. A heat spreader that is too thick will increase the size of the battery stack. For example, some vehicle-mounted applications require reducing the volume and weight to save space.

[0047] In some embodiments of the present invention, the water cooling module 5 includes a shell, a water flow cavity is arranged inside the shell, two ends of the water flow cavity are respectively a water inlet and a water outlet, a valve is arranged on the water inlet, and the valve is connected to the control module. The control module changes the cooling water flow rate by controlling the valve.

[0048] In some embodiments of the present invention, the shell of the water cooling module 5 is made of aluminum alloy. A heat sink groove for embedding the condensing end of the heat sink is processed on the shell. The heat sink is inserted into the heat sink groove and only contacts the water cooling shell, not the water. The ultra-thin heat sink temperature control section inserted into the water cooling module is coated with thermal conductive silicone grease to reduce thermal resistance.

[0049] In some embodiments of the present invention, the heat preservation and heating module 6 includes an aluminum alloy heat preservation shell and a phase change material and a heating rod filled inside, and the heating rod is connected to the control module. The phase change material is composed of 90% paraffin wax and 10% expanded graphite by mass, wherein the melting point of the paraffin wax is 80°C, and this proportion can improve the ability of the heat preservation and heating module to store latent heat and ensure good thermal conductivity and formability. The control module can control the heating power of the heating rod.

[0050] In some embodiments of the present invention, the phase change material preparation method in the thermal insulation heating module 6 is: low melting point paraffin and expanded graphite are heated and stirred in an 80°C water bath for 1 hour until the molten paraffin is integrated into the voids of the expanded graphite, the cooled paraffin-expanded graphite mixture is placed in a thermal insulation shell and pressed into one piece with a heating rod wrapped with a graphene film, and when assembled with the battery stack, the heating rod is heated to 80°C as a whole and then inserted into the temperature control section of the heat spreader wrapped with a graphene film.

[0051] In some embodiments of the present invention, the working method of the proton exchange membrane fuel cell is:

[0052] When the stack temperature T is lower than the first preset temperature T1, the phase change material of the heat preservation and heating module 6 releases latent heat, and the latent heat is introduced into the fuel cell stack through the ultra-thin heat spreader 4 to be used for heat preservation of the fuel cell stack;

[0053] The temperature sensor collects the temperature T of the fuel cell stack in real time. When the temperature T of the fuel cell stack is higher than the second preset temperature T2, the control module increases the water flow rate of the water cooling module 5 to accelerate the cooling of the temperature control section of the ultra-thin heat sink 4, and the phase change material in the heat preservation and heating module 6 absorbs and stores the heat of the fuel cell stack;

[0054] When the fuel cell stack is cold started, that is, when the temperature T inside the stack is collected to be lower than the first preset temperature T1, the phase change material in the thermal insulation and heating module 6 releases heat to increase the temperature of the fuel cell stack, and the control module increases the heating power of the heating rod in the thermal insulation and heating module 6 to increase the temperature of the temperature control section of the ultra-thin heat sink 4, and the temperature control section transfers heat to the heat conduction section to increase the temperature of the fuel cell stack.

[0055] The first preset temperature T1 and the second preset temperature T2 are selected according to the optimal operating temperature of the fuel cell stack. In some embodiments of the present invention, the first preset temperature T1 is 60°C, and the second preset temperature T2 is 80°C.

[0056] Through the above process, the temperature of each part of the hydrogen fuel cell stack is evenly maintained in the optimal range, heat is stored to achieve rapid cold start of the stack and prevent local temperatures in the stack from being too high, thereby optimizing the thermal management of the stack to improve the stack performance.

[0057] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementations here. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A proton exchange membrane fuel cell thermal management system, characterized in that: It comprises a fuel cell stack, an ultra-thin heat sink (4), a water cooling module (5), a heat preservation and heating module (6) and a control module; The fuel cell stack comprises a plurality of single cells connected in series, each of the single cells comprises a membrane electrode (2) and a bipolar plate (3), a slot is provided in the bipolar plate (3), the ultra-thin heat spreader (4) is embedded in the slot of the bipolar plate (3), a bipolar plate end plate (1) is provided on the outside of the fuel cell stack, and a temperature sensor is also provided in the fuel cell stack; The water cooling module (5) and the heat preservation and heating module (6) are respectively located on the upper and lower sides of the fuel cell stack, and two adjacent ultra-thin heat sinks (4) are respectively connected to the water cooling module (5) and the heat preservation and heating module (6); The heat-insulating heating module (6) comprises a heat-insulating outer shell, a heating rod and a phase-change material arranged in the heat-insulating outer shell; The control module is connected to both the water cooling module (5) and the heat preservation and heating module (6) and is used to control the flow rate of the cooling fluid and the power of the heating rod; The ultra-thin heat spreader (4) comprises a heat conduction section and a temperature control section, the heat conduction section is embedded in the bipolar plate (3), and the temperature control section is connected to a water cooling module (5) or a heat preservation and heating module (6).

2. A proton exchange membrane fuel cell thermal management system according to claim 1, characterized in that: The temperature control section accounts for 15% to 20% of the overall area of ​​the ultra-thin heat spreader (4).

3. A proton exchange membrane fuel cell thermal management system according to claim 1, characterized in that: The ultra-thin heat spreader (4) comprises an upper shell plate, a lower shell plate, a liquid wick, a support body and a working medium; the upper shell plate and the lower shell plate are sealed and supported by the support body to form a hollow cavity; the working medium and the liquid wick are arranged in the hollow cavity.

4. A proton exchange membrane fuel cell thermal management system according to claim 3, characterized in that: The working medium is a mixture of any one or more of methanol, ethanol, acetone, deionized water, ammonia and freon.

5. A proton exchange membrane fuel cell thermal management system according to claim 3, characterized in that: The upper shell plate and the lower shell plate are made of any one of copper, aluminum, copper alloy and aluminum alloy.

6. A proton exchange membrane fuel cell thermal management system according to claim 3, characterized in that: The liquid absorbent core is a sintered copper powder column wire mesh composite liquid absorbent core, a sintered copper wire mesh woven belt composite liquid absorbent core or a sintered copper powder column wire mesh woven belt liquid absorbent core.

7. A proton exchange membrane fuel cell thermal management system according to claim 1, characterized in that: The thickness of the ultra-thin heat spreader (4) is 0.6-1 mm.

8. A proton exchange membrane fuel cell thermal management system according to claim 1, characterized in that: The water cooling module (5) comprises an outer shell and an internal water flow cavity, a water inlet and a water outlet are respectively provided at two ends of the water cooling module (5), a valve is provided on the water inlet, and the valve is connected to the control module, and a slot for embedding a heat spreader temperature control section is provided on the outer shell.

9. A proton exchange membrane fuel cell thermal management system according to claim 1, characterized in that: The phase change material in the heat preservation and heating module is composed of 80-90% paraffin wax and 10-20% expanded graphite by mass, and the melting point of the paraffin wax is between 60-80°C.

10. The operating method of a proton exchange membrane fuel cell thermal management system according to claim 1, characterized in that: When the temperature T of the fuel cell stack is lower than the first preset temperature T1, the phase change material of the heat preservation and heating module (6) releases latent heat, and the latent heat is introduced into the fuel cell stack through the ultra-thin heat spreader (4) to be used for heat preservation of the fuel cell stack; The temperature sensor collects the temperature of the fuel cell stack in real time, and when the stack temperature T of the fuel cell stack is higher than the second preset temperature T2, the control module increases the water flow rate of the water cooling module (5) to accelerate the cooling of the temperature control section of the ultra-thin heat sink (4), and the phase change material in the heat preservation and heating module (6) absorbs and stores the heat of the fuel cell stack; When the fuel cell stack is cold started, that is, when the temperature T inside the stack is detected to be lower than the first preset temperature T1, the phase change material in the thermal insulation and heating module (6) releases heat to increase the temperature of the fuel cell stack, and the control module increases the heating power of the heating rod in the thermal insulation and heating module (6) to increase the temperature of the temperature control section of the ultra-thin heat spreader (4), and the temperature control section transfers the heat to the heat conduction section to increase the temperature of the fuel cell stack.

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