Induced condensation enhanced water management flow channel structure for a fuel cell

Abstract

The application relates to a kind of induced condensation reinforced drainage polar plate flow channel structures for fuel cell, comprising: flow channel and the protruding condensation island arranged on flow channel, flow channel includes: interval distribution contraction area and expansion area;The width of expansion area is greater than the width of contraction area;Multiple protruding condensation islands are staggered on flow channel, cooling channel is arranged in protruding condensation island, and cooling channel is used to cool the surface of protruding condensation island.Compared with prior art, the application has excellent drainage and gas transmission performance, uses airflow kinetic energy and local surface condensation and strong hydrophobicity to combine, induces two-phase flow pattern in flow channel, avoids the "water flooding" effect in flow channel and gas diffusion layer, reduces mass transfer resistance, improves fuel cell internal water management, and improves fuel cell overall performance and life.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to an induced condensation enhanced drainage electrode channel structure for fuel cells. Background Technology

[0002] Hydrogen energy, as an environmentally friendly and green renewable energy source, is a trend in international new energy development. Proton exchange membrane fuel cells (PEMFCs) are currently one of the most promising, efficient, and reliable methods for utilizing hydrogen energy. They can directly convert the chemical energy in hydrogen and oxygen into electrical energy, without being limited by the Carnot cycle, and have high energy conversion efficiency. The only emission is water, resulting in zero carbon emissions and no pollution. The basic structure of a PEMFC cell mainly includes bipolar plates and membrane electrode assemblies (gas diffusion layer, catalyst layer, and proton exchange membrane, etc.) sandwiched between the bipolar plates. The cell has no internal mechanical transmission devices, produces almost no noise, and operates rapidly at low temperatures, making it suitable for applications in transportation, power plants, and communications.

[0003] Bipolar plates, also known as flow field plates, are a crucial component of proton exchange membrane fuel cells (PEMFCs). Their main functions include uniformly distributing reactant gases, facilitating electron conduction between the anode and cathode, and promptly removing reaction product water and waste heat. The flow field consists of grooves machined onto the bipolar plates, and its structure determines the flow state of reactants and product water within it. An inappropriate flow field design increases flow resistance, hindering reactant gas transfer to the catalyst layer and reducing the cell's power density. Furthermore, the inability to promptly remove product water leads to water blockage on the plates and membrane electrode assemblies (MEAs), causing reverse polarity and ultimately resulting in MEA corrosion and shortened cell lifespan.

[0004] Commonly used direct-flow and serpentine flow channel structures in bipolar plates are prone to product water blockage within the flow channel and adjacent diffusion layer, making it difficult for the gas flow to clean it away. This can easily lead to water blockage and increase gas diffusion resistance. The bipolar plate flow channel designs disclosed in patents CN111668508B and 111200137B do not regulate the product water, resulting in highly random condensation locations for liquid water, which can easily lead to water blockage in narrower flow channel areas. More importantly, most existing fuel cell plate flow channel structures do not comprehensively consider the flow state of the gas and liquid phases within the flow channel, optimizing the structure solely from the perspective of discharging liquid water. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing an induced condensation enhanced drainage plate flow channel structure for fuel cells. This structure has excellent drainage and gas transport performance. It utilizes the combination of gas kinetic energy with local surface condensation and strong hydrophobicity to induce a two-phase flow pattern in the flow channel, avoiding the "flooding" effect in the flow channel and gas diffusion layer, reducing mass transfer resistance, improving internal water management of the fuel cell, and enhancing the overall performance and lifespan of the fuel cell.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The present invention provides an induced condensation enhanced drainage plate flow channel structure for fuel cells, comprising: a flow channel and a protruding condensation island disposed on the flow channel, wherein the flow channel includes: a contraction zone and an expansion zone spaced apart;

[0008] The width of the expansion region is greater than the width of the contraction region;

[0009] Multiple raised condensation islands are staggered along the flow channel. Each raised condensation island has a cooling channel for cooling its surface. Each raised condensation island is small in volume and has little impact on the overall gas flow in the expansion or contraction zone. It mainly affects the degree of condensation and separation of liquid water in local areas of the flow channel. The number and arrangement of raised condensation islands in each expansion or contraction zone can be the same or different.

[0010] Furthermore, the walls of the contraction zone are hydrophilic.

[0011] Furthermore, the surface of the raised condenser island is coated with a highly hydrophobic coating, which enhances its hydrophobicity. When the condensed liquid water condenses into small droplets or forms a thin liquid film on the surface of the raised condenser island, it can be quickly blown away by the airflow, preventing large droplets from causing localized water blockage.

[0012] Furthermore, the corners within the expansion zone are equipped with rounded transition edges on the inner walls of the flow channels. This reduces the resistance encountered by the liquid water flowing through the corners and prevents large amounts of liquid water from accumulating at the corners.

[0013] Furthermore, multiple raised condensation islands may be located entirely on the expansion zone, or entirely on the contraction zone, or both on the contraction and expansion zones.

[0014] Furthermore, the cooling channel is equipped with cooling air or coolant. Circulating cooling air or coolant is introduced into the cooling channel to cool the surface of the raised condensation island, making the temperature at the raised condensation island significantly lower than the surrounding flow channel. This promotes the condensation of more product gaseous water onto the surface of the raised condensation island, reduces the humidity of the gas within the flow channel, and facilitates the discharge of gaseous water from the gas diffusion layer into the flow channel, preventing excessive condensation of gaseous water within the gas diffusion layer and the formation of water blockage.

[0015] Furthermore, the pressure in the contraction zone is greater than the pressure in the expansion zone.

[0016] The flow Q through the contraction and expansion regions can be expressed as:

[0017] Q = v2A2 = v3A3,

[0018] Where v2 is the gas velocity in the contraction zone and v3 is the gas velocity in the expansion zone; A2 is the cross-sectional area of ​​the contraction zone and A3 is the cross-sectional area of ​​the expansion zone.

[0019] Since A2 < A3, then v2 > v3.

[0020] According to Bernoulli's equation, the gas velocity v2 and gas pressure p2 in the contraction zone and the gas velocity v3 and gas pressure p3 in the expansion zone can be expressed as:

[0021]

[0022] Since h2 = h3, it can be derived that...

[0023] Since v2 > v3, then p2 < p3.

[0024] The contraction zone has high flow velocity and low pressure, creating a pressure difference with the expansion zone, which drives the gas to diffuse rapidly within the gas diffusion layer below the flow channel. The low-pressure zone formed by the contraction zone facilitates the transport of product water from the gas diffusion layer (higher pressure) to the flow channel (lower pressure), improving drainage efficiency, enhancing water management in the fuel cell, preventing flooding within the diffusion layer, and ultimately improving the performance and lifespan of the fuel cell.

[0025] Common gas-liquid two-phase flow patterns in flow channels include bubbly flow, slug flow, and annular flow. When the gas fill factor and flow velocity in the flow channel are low, the gas-liquid two-phase flow is bubbly, where the liquid phase is continuous and the gas phase is discontinuous, resulting in a flooded flow channel. As the gas velocity increases, the gas-liquid two-phase flow pattern in the flow channel transitions from bubbly flow to slug flow, at which point the gas fill factor in the flow channel increases compared to bubbly flow. When the gas velocity further increases, the gas-liquid two-phase flow pattern in the flow channel becomes annular, where the gas phase merges into a gas core that flows smoothly in the center of the flow channel, while the liquid phase forms a flowing liquid ring (film) along the flow channel wall. The channel wall of the contraction zone has low hydrophobicity (becomes hydrophilic), which makes it easy for liquid water in the contraction zone to adhere to the channel wall. This leaves enough space for the airflow to pass through the central air core position, induces the development of a ring flow in the channel with smooth airflow transmission of the gas and liquid phases, enhances the effect of airflow to drive the liquid water out of the channel, and avoids water flooding in the channel.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) By designing the raised condensation island, gaseous water can be condensed into liquid on the surface of the raised condensation island, reducing the humidity of the gas in the flow channel, thereby promoting the diffusion of gaseous water in the gas diffusion layer into the flow channel, and avoiding the large amount of gaseous water condensing in the gas diffusion layer and thus blocking the pores.

[0028] (2) The structural design of combining expansion and contraction zones utilizes the pressure difference formed by the airflow velocity to drive the liquid water in the flow channel out; the formation of local low pressure in the flow channel is conducive to promoting the diffusion of product gaseous water from the gas diffusion layer to the flow channel.

[0029] (3) By changing the hydrophilicity or hydrophobicity of the wall surface in different regions of the flow channel, the flow pattern with low mass transfer resistance of the two phases in the flow channel can be induced, the gas phase velocity in the flow channel can be increased, water blockage in the flow channel can be avoided, and mass transfer resistance can be reduced. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of the flow channel of the present invention.

[0031] Figure 2 These are front views of three embodiments of the flow channel of the present invention.

[0032] Figure 3 For along Figure 2 A cross-sectional view along line AA.

[0033] Figure 4 For along Figure 2 A cross-sectional view of the BB line.

[0034] Figure 5 This is a schematic diagram of a common gas-liquid two-phase flow pattern in a flow channel.

[0035] Reference numerals: 1. Protruding condensation island; 2. Contraction zone; 3. Expansion zone; 4. Transition fillet of inner wall of flow channel; 5. Cooling channel; 6. Gas; 7. Liquid water. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0037] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. In the description of the invention, it should be understood that the terms "first," "second," and "third," etc., in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0038] Example 1

[0039] This embodiment provides an induced condensation enhanced drainage electrode channel structure for fuel cells, such as... Figure 1 , Figure 2As shown, it includes: a flow channel and a raised condensation island 1 disposed on the flow channel. The flow channel includes: a contraction zone 2 and an expansion zone 3 distributed at intervals.

[0040] The width of expansion region 3 is greater than the width of contraction region 2;

[0041] Multiple raised condensation islands 1 are staggered in the flow channel. Each raised condensation island 1 is equipped with a cooling channel 5, which is used to cool the surface of the raised condensation island 1. Each raised condensation island 1 is small in volume and has little impact on the overall gas flow 6 in the expansion zone 3 or contraction zone 2. It mainly affects the degree of condensation and separation of liquid water 7 in local areas of the flow channel. The number and arrangement of raised condensation islands 1 in each expansion zone 3 or contraction zone 2 can be the same or different.

[0042] In a specific implementation, the wall surface of the contraction zone 2 is hydrophilic.

[0043] In a specific embodiment, the surface of the raised condenser island 1 is coated with a strong hydrophobic coating to enhance its hydrophobicity. When the condensed liquid water 7 condenses into small droplets or coalesces into a thin liquid film on the surface of the raised condenser island 1, it can be quickly blown away by the airflow, avoiding large droplets from causing local water blockage.

[0044] In a specific implementation, a flow channel inner wall transition fillet 4 is provided at the corner within the expansion zone 3. This reduces the resistance encountered by the liquid water 7 as it flows through the corner, preventing the liquid water 7 from accumulating in large quantities at the corner.

[0045] In specific implementation methods, such as Figure 2 As shown, all the protruding condensation islands 1 are located on the expansion area 3 (e.g., Figure 2 (a) or multiple protruding condensation islands 1 are all located on the contraction zone 2 (as shown in (a)). Figure 2 (b) or multiple protruding condensation islands 1 are provided on the contraction zone 2 and the expansion zone 3 (as shown in the figure). Figure 2 (c) is shown.

[0046] In specific implementation methods, such as Figure 3 , Figure 4 As shown, circulating cooling air or coolant is introduced into cooling channel 5. The cooling air absorbs heat at one end of the raised condenser island 1 and releases heat at the other end. The circulating cooling air or coolant in cooling channel 5 cools the surface of the raised condenser island 1, making the temperature at the location of the raised condenser island 1 significantly lower than that of the surrounding flow channel. This promotes the condensation of more product gaseous water into liquid water 7 on the surface of the raised condenser island 1, reduces the humidity of the gas 6 in the flow channel, and promotes the discharge of gaseous water from the gas diffusion layer into the flow channel, preventing the large-scale condensation of gaseous water in the gas diffusion layer and the formation of water blockage.

[0047] In a specific implementation, the pressure in the contraction zone 2 is greater than the pressure in the expansion zone 3.

[0048] The flow rate Q through contraction zone 2 and expansion zone 3 can be expressed as:

[0049] Q = v2A2 = v3A3,

[0050] Where v2 is the gas velocity in contraction zone 2 and v3 is the gas velocity in expansion zone 3; A2 is the cross-sectional area of ​​contraction zone 2 and A3 is the cross-sectional area of ​​expansion zone 3.

[0051] Since A2 < A3, then v2 > v3.

[0052] According to Bernoulli's equation, the gas velocity v2 and gas pressure p2 in the contraction zone 2 and the gas velocity v3 and gas pressure p3 in the expansion zone 3 can be expressed as:

[0053]

[0054] Since h2 = h3, it can be derived that...

[0055] Since v2 > v3, then p2 < p3.

[0056] The high flow velocity and low pressure within the contraction zone 2 create a pressure difference with the expansion zone 3, propelling gas 6 to rapidly diffuse within the gas diffusion layer below the flow channel. The low-pressure zone formed by the contraction zone 2 facilitates the transport of product water from the gas diffusion layer (higher pressure) to the flow channel (lower pressure), improving drainage efficiency, enhancing water management in the fuel cell, preventing flooding within the diffusion layer, and ultimately improving the performance and lifespan of the fuel cell.

[0057] like Figure 5 As shown, common gas-liquid two-phase flow patterns in flow channels include bubbly flow (such as...). Figure 5 (a) shown), slug flow (as shown in) Figure 5 (b) shown) and annular flow (as shown) Figure 5 (as shown in (c)). When the gas content and flow velocity in the flow channel are low, the gas-liquid two-phase flow state is bubbly (as shown in (c)). Figure 5 (as shown in (a)), at this point, the liquid phase is continuous, the gas phase is discontinuous, and the flow channel is flooded; as the gas velocity increases, the gas-liquid two-phase flow state in the flow channel transitions from bubbly flow to slug flow (as shown in (a)). Figure 5 (b) shows that the gas content in the flow channel increases compared to the bubbly flow; when the gas velocity further increases, the gas-liquid two-phase flow in the flow channel becomes annular (as shown in the figure). Figure 5(c) As shown, at this point, the gas phase merges into a gas core that flows smoothly in the center of the channel, while the liquid phase forms a flowing liquid ring (film) along the channel wall. The channel wall of the contraction zone 2 has low hydrophobicity (is hydrophilic), which makes it easy for the liquid water 7 in the contraction zone 2 to adhere to the channel wall. This leaves enough space for the airflow to pass through the central gas core position, inducing the development of a ring flow with smooth airflow transmission in the channel, enhancing the effect of the airflow driving the liquid water out of the channel, and preventing water from flooding the channel.

[0058] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A flow channel structure for an induced condensation-enhanced drainage electrode plate in a fuel cell, characterized in that, include: The flow channel and the protruding condensation island (1) provided on the flow channel, the flow channel including: spaced contraction zone (2) and expansion zone (3); The width of the expansion region (3) is greater than the width of the contraction region (2); Multiple raised condensation islands (1) are staggered on the flow channel, and each raised condensation island (1) is provided with a cooling channel (5) for cooling the surface of the raised condensation island (1). The wall of the contraction zone (2) is hydrophilic, the surface of the protruding condensation island (1) is provided with a strong hydrophobic coating, and the pressure inside the contraction zone (2) is less than the pressure inside the expansion zone (3).

2. The induced condensation enhanced drainage electrode channel structure for fuel cells according to claim 1, characterized in that, The corner within the expansion zone (3) is provided with a transition rounded corner (4) on the inner wall of the flow channel.

3. The induced condensation enhanced drainage electrode channel structure for fuel cells according to claim 1, characterized in that, All of the protruding condensation islands (1) are located on the expansion area (3).

4. The induced condensation enhanced drainage electrode channel structure for fuel cells according to claim 1, characterized in that, All of the protruding condensation islands (1) are located on the contraction zone (2).

5. The induced condensation enhanced drainage electrode channel structure for fuel cells according to claim 1, characterized in that, Multiple raised condensation islands (1) are disposed on the contraction zone (2) and the expansion zone (3).

6. The induced condensation enhanced drainage electrode channel structure for fuel cells according to claim 1, characterized in that, Cooling air is provided in the cooling channel (5).

7. The induced condensation enhanced drainage electrode channel structure for fuel cells according to claim 1, characterized in that, The cooling channel (5) contains coolant.

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