CN103427098A - Fluid field plate with lyophilic and lyophobic passages in nesting arrangement - Google Patents

Abstract

The invention relates to a flow field plate with nested arrangement of lyophilic channels and lyophobic channels, which belongs to the field of fuel cells and water electrolysis cells, and relates to a flow field plate with nested arrangement of lyophilic channels and lyophobic channels, which is applicable to Flow field plate structures for proton exchange membrane fuel cells and electrolyzers. The flow field plate includes a flow field plate body, a first fluid channel and a second fluid channel for gas supply and liquid transport, and a ridge separating the first and second fluid channels. The flow field plate includes at least one lyophilic channel opposite to the surface of the membrane electrode assembly and one lyophobic channel opposite to the surface of the membrane electrode assembly. The channels are nested and arranged on the flow field plate body, and the channels are separated by ridges. open. The flow field plate structure with nested arrangement of lyophilic channels and lyophobic channels of the present invention has an obvious effect on the phase-separated transport of two-phase fluids, reduces the transport resistance of reactants and products in the flow field, and improves the reaction rate. The uniform distribution of the fluid can effectively improve the working performance of the fuel cell or electrolytic cell.

Description

A flow field plate with nested arrangement of lyophilic channels and lyophobic channels

technical field

The invention belongs to the field of fuel cells and water electrolysis cells, and relates to a flow field plate with nested arrangement of lyophilic channels and lyophobic channels, which is suitable for the flow field plate structure of proton exchange membrane fuel cells and electrolytic cells.

Background technique

Fuel cell is a kind of clean energy that directly converts chemical energy into electric energy. It has the advantages of high specific energy, high efficiency, clean and environmental protection, etc. It has broad application prospects in many fields of national economy. A fuel cell is mainly composed of a membrane electrode assembly (Membrane Electrode Assembly, MEA) and a pole plate. The MEA is the core area of the electrochemical reaction of the fuel cell. It is usually composed of a proton exchange membrane and porous electrochemical electrodes on both sides; the plate has the dual functions of collecting current and distributing the reaction material, and is generally processed on the surface of a flat plate-shaped conductor. The fluid distribution channels covering the entire electrochemically active area of the fuel cell are obtained. During the working process of the fuel cell, the reactant flows in from the inlet port of the flow field as the first fluid, passes through the active area of the MEA and undergoes an electrochemical reaction, and the generated second fluid is discharged from the active area of the MEA into the flow field channel, and finally reacts with the remaining fluid The substances are discharged from the outlet of the flow field channel together. An electrolyzer is actually a fuel cell in reverse, where electricity splits water into hydrogen and oxygen.

During the actual working process of the fuel cell, the first fluid and the second fluid in the same flow field will mix and exist in the form of gas and liquid in many cases. For example, the anode flow field of a fuel cell using liquid hydrocarbon fuel will generally release gaseous carbon dioxide along with the catalytic oxidation of the fuel; similarly, the cathode flow field of a fuel cell using gaseous oxidants (such as pure oxygen, air) will also usually release Liquid water is produced following the catalytic reduction reaction of the oxidizing agent. It can be seen that the gas-liquid two-phase fluid is a common flow pattern in the fuel cell flow field. The adverse effect of this two-phase flow on the fuel cell is mainly reflected in 1) species crosstalk and mutual restriction: the first fluid and the second fluid of different phases are transported in the same channel, which will cause the species of different phases to crowd out the activity of each other 2) Uneven distribution and performance fluctuation: due to the existence of competitive constraints in gas-liquid transportation, a certain Some local areas will only be occupied by one of the phase species, forming an uneven distribution of the first fluid and the second fluid and periodic fluctuations in the fluid form, which limits the further improvement of battery performance; 3) High parasitic power consumption of the system: in the channel The mixed transmission of gas-phase and liquid-phase fluids needs to overcome great capillary resistance, which increases the power consumption of the auxiliary feeding system and reduces the specific power and specific energy of the system.

Aiming at the problems of gas-liquid two-phase fluid transport in the fuel cell flow field, domestic and foreign research institutions have successively proposed related solutions. Literature C Litterst, Nils Paust, et.al, Increasing μ DMFC efficiency by passive CO ₂ bubble removal and discontinuous operation.

J.Micromech.Microeng.16(2006)S248–S253Aiming at the problem of direct methanol fuel cell anode fuel transfer, a technical solution was proposed to increase the "inverted T-shaped" foam removal structure in the parallel flow field to promote the spontaneous and directional removal of carbon dioxide bubbles ; Literature T.Metz, N.Paust, et.al, Microstructured flow field for passive water management in miniaturized PEM fuelcells.Sensors and Actuators A: Physical, 143,1(2008) 49–57 is to solve the problem of PEM fuel cell cathode water Flooded, developed a double-layer cathode flow field, by adding a second layer of trapezoidal channels in the cathode air flow channel, the collection and removal of the cathode water was realized. Patent No. CN101459246B Invention Patent Name: Vein-shaped fuel cell flow field plate, inventor: Wang Lianbang et al. Invented a solution to solve the problem of large flow resistance of the flow field plate, uneven distribution of fluid and difficulty in gas-liquid two-phase separation, and designed a A vein-shaped fuel cell flow field plate. The liquid flows in along the direction of the main vein, and after passing through the branch veins at an angle of 45° to the main vein, it merges with the fluid in the main vein and flows out at the outlet. This scheme improves the uniformity of reactant distribution, but the gas-liquid two-phase fluid still remains Flowing in the same channel, the flow resistance in the flow field has not been fundamentally improved; patent number CN201812887U, invention patent name: a portable direct methanol fuel cell anode flow field plate, inventor: Wang Xindong et al., disclosed the use of two sets of independent The hollowed-out flow channels are used as the technical solution of the gas flow channel and the liquid flow channel respectively. It is hoped that the gas generated in the flow field will be discharged through the dedicated gas channel. The gas diffuses into the gas-specific channel and blocks it, resulting in an increase in the pressure in the flow field, thereby affecting the stability of the fuel cell.

Contents of the invention

The present invention aims at problems such as the obstruction or uneven distribution of the first fluid caused by the accumulation of the second fluid in the flow field of the fuel cell or electrolytic cell, and the difficulty in the separation of the two-phase fluids, etc., and invents a nested arrangement of lyophilic channels and lyophobic channels The flow field plate realizes the orderly transportation and management of the two-phase fluid in the fuel cell or electrolytic cell. The invention utilizes the lyophilic channel and the lyophobic channel to selectively separate the two-phase fluid, thereby ensuring smooth transmission and uniform distribution of the first fluid in the flow field.

The technical solution adopted in the present invention is a flow field plate with nested arrangement of lyophilic channels and lyophobic channels, characterized in that the flow field plate includes a flow field plate body 1, the first fluid for gas supply and liquid transport Channel 3, second fluid channel 2, and ridge 5 separating the first and second fluid channels 3, 2; the flow field plate includes at least one lyophilic channel opposite to the surface of the membrane electrode assembly and one opposite to the surface of the membrane electrode assembly The opposite liquid-repellent channels, the above-mentioned channels are nested and arranged on the flow field plate body 1, and the channels are separated by ridges 5; the channels respectively have a first fluid inlet, an outlet 7, 4, and a second fluid outlet 6, The first fluid inlet, the outlets 7, 4 and the second fluid outlet 6 are all through holes.

A flow field plate with nested arrangements of lyophilic channels and lyophobic channels, characterized in that the sum of the projected areas of the lyophilic channels and lyophobic channels in the normal direction of the flow field plane in contact with the membrane electrode assembly is the membrane electrode assembly 20% to 80% of the active area; the contact angle of the liquid phase fluid on the surface of the lyophilic channel is <90°, and the contact angle on the surface of the lyophobic channel is ≥90°.

A flow field plate with nested arrangement of lyophilic channels and lyophobic channels is characterized in that the lyophilic and lyophobic structures nested in the flow field plate are serpentine flow field, parallel flow field, spiral flow field or compound flow field.

The remarkable effect of the present invention is that the flow field plate structure with nested arrangement of lyophilic channels and lyophobic channels has an obvious effect on the phase-separated transport of two-phase fluids, reducing the transport resistance of reactants and products in the flow field , improve the distribution uniformity of the reaction fluid, and effectively improve the working performance of the fuel cell or electrolytic cell.

Description of drawings

Figure 1 is a schematic diagram of the structure of a serpentine flow field plate with nested arrangement of lyophilic and lyophobic channels, Figure 2 is a schematic diagram of the structure of a parallel flow field plate with nested arrangement of lyophilic and lyophobic channels, and Figure 3 is Schematic diagram of the structure of a helical flow field plate with nested arrangement of lyophilic and lyophobic channels. Figure 4 is a side sectional view of a serpentine flow field plate with nested arrangement of lyophilic and lyophobic channels. Among them: in the drawings, 1 is the body of the flow field plate, 3 is the first fluid channel, 2 is the second fluid channel, 5 is the ridge, 7 is the first fluid inlet, 4 is the first fluid outlet, and 6 is the second fluid outlet .

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. However, the scope of the present invention is not limited by these examples. A flow field plate in which lyophilic channels and lyophobic channels are nested, when the contact angle of the liquid in the channel is <90°, the channel is a lyophilic channel; when the contact angle of the liquid in the channel is ≥90° , the channel is a lyophobic channel. The flow field plate includes a flow field plate body 1 , a first fluid channel 3 and a second fluid channel 2 for gas supply and liquid transport, and a ridge 5 separating the first and second fluid channels 3 and 2 . When the first fluid is a liquid and the second fluid is a gas, channel 3 is a lyophilic channel, and channel 2 is a lyophobic channel; when the first fluid is a gas and the second fluid is a liquid, channel 3 is a lyophobic channel, and channel 2 is a lyophobic channel. 2 is the lyophilic channel. The processing depth of the lyophilic channel and the lyophobic channel is less than the thickness of the flow field plate, the inlet and outlet of the liquid and gas are through holes, and the lyophilic channel and the lyophobic channel are separated by ridges, so that the liquid and gas are not in the flow field. Mixed streams in the same channel. The lyophilic channels and the lyophobic channels are alternately nested and arranged in the same plane of the flow field plate, so that the generated second fluid is discharged through the shortest path. The width and depth of the channel should be designed to prevent the porous electrodes on the MEA from being pressed into the channel to block the fluid transport when the battery is packaged, and the sum of the normal projected area of the lyophilic channel and the lyophobic channel in the flow field plane in contact with the MEA is the MEA activity 20% to 80% of the area. In order to realize the phase-separated transport of the two-phase fluid more efficiently, the present invention modifies the surface of the flow field channel so that it has lyophilic and lyophobic capabilities respectively, wherein the contact angle of the liquid-phase fluid on the surface of the lyophilic channel is less than 90° , the contact angle on the surface of the lyophobic channel is ≥90°, so that the gas phase fluid and the liquid phase fluid can be selectively transported separately by the channel itself. The above-mentioned flow field structure is applicable to flow fields such as serpentine flow field, spiral flow field and parallel flow field.

When the fuel cell or the electrolytic cell is working, the first fluid flows in the flow field along the first fluid channel after entering the flow field, and penetrates the catalytic layer through the diffusion layer inside the fuel cell to react to generate the second fluid. In the design scheme of the present invention, the second fluid channel nested with the first fluid channel can lead the second fluid generated by the reaction out of the flow field from the MEA reaction area in the shortest path, thereby reducing the transport resistance of the first fluid , Improve the working efficiency of fuel cells or electrolytic cells.

Specific implementation mode 1: In this embodiment, an anode flow field plate of a direct methanol fuel cell with nested arrangement of lyophilic channels and lyophobic channels is taken as an example. The flow field plate consists of a flow field plate body 1, a first fluid channel 3 for methanol solution transport, a second fluid channel 2 for carbon dioxide transport, a ridge 5 separating the first fluid channel and the second fluid channel, Methanol solution inlet 7, methanol solution outlet 4 and carbon dioxide outlet 6 are composed. The length, width, and thickness of the flow field plate are 40 mm, 40 mm, and 1.5 mm, respectively; the width of the first fluid channel 3 is 1.0 mm, and the depth is 0.4 mm; the width of the second fluid channel 2 is 0.5 mm, and the depth is 0.2 mm. mm. The sum of the projected areas of the first fluid channel and the second fluid channel in the normal direction of the flow field plane in contact with the MEA is 20% of the active area of the MEA. In this embodiment, the methanol solution is the first fluid, and the gaseous carbon dioxide produced by the anode is the second fluid. The contact angle of the methanol solution on the surface of the first fluid channel is 40°, and the contact angle on the surface of the second fluid channel is 150°. Therefore, for the methanol solution, the first fluid channel 3 is a lyophilic channel, and the second fluid channel 2 is a lyophobic channel.

In this embodiment, the methanol solution enters the first fluid channel 3 through the inlet 7 and flows along the channel 3. During the flowing process, the methanol solution penetrates the diffusion layer and enters the catalytic layer to react to generate carbon dioxide gas. Since the surface of the second fluid channel 2 is lyophobic to the methanol solution, the methanol solution will not infiltrate the second fluid channel 2 . The carbon dioxide produced by the reaction enters the second fluid channel 2 along the shortest path, and is quickly discharged from the carbon dioxide outlet 6, while the incompletely reacted methanol solution is discharged from the methanol solution outlet 4 under the action of external pressure, so as to realize the separation of methanol solution and carbon dioxide in the flow field. Transport in phases.

Specific implementation mode 2: In this embodiment, a proton exchange membrane fuel cell cathode flow field plate with lyophilic channels and lyophobic channels nested in arrangement is taken as an example. The flow field plate consists of a flow field plate body 1, a first fluid channel 3 for oxygen transport, a second fluid channel 2 for liquid water transport, a ridge 5 separating the first fluid channel and the second fluid channel, Oxygen inlet 7, oxygen outlet 4 and liquid water outlet 6 are composed. The length, width, and thickness of the flow field plate are 40 mm, 40 mm, and 1.5 mm, respectively; the width of the first fluid channel 3 is 0.8 mm, and the depth is 0.3 mm; the width of the second fluid channel 2 is 0.4 mm, and the depth is 0.2 mm. mm. The sum of the projected areas of the first fluid channel and the second fluid channel in the normal direction of the flow field plane in contact with the MEA is 20% of the active area of the MEA. In this embodiment, oxygen is the first fluid, and cathode product liquid water is the second fluid. The contact angle of water on the surface of the first fluid channel is 170°, and the contact angle of water on the surface of the second fluid channel is 30°. Therefore, for liquid water, the first fluid channel 3 is a lyophobic channel, and the second fluid channel 2 is a lyophilic channel.

In this embodiment, oxygen enters the first fluid channel 3 through the inlet 7 and flows along the channel 3. During the flow process, the oxygen passes through the diffusion layer and enters the catalytic layer to react to generate liquid water, and the generated liquid water enters the second fluid channel 2 along the shortest path. , and quickly discharged from the liquid water outlet 6, thereby reducing the flow resistance of oxygen in the flow field and improving the mass transfer efficiency.

Embodiments 1 and 2 can adopt different forms of flow field, such as serpentine flow field, parallel flow field and spiral flow field.

Because the present invention adopts the flow field plate structure in which the lyophilic channel and the lyophobic channel are nested and arranged, the phase separation transport effect of the two-phase fluid is obvious, and the working performance of the fuel cell or the electrolytic cell is effectively improved.

Claims (3)

1. A flow field plate with a nested arrangement of lyophilic channels and lyophobic channels, characterized in that the flow field plate includes a flow field plate body (1), the first fluid channel 3 for gas supply and liquid transportation, The second fluid channel 2, and the ridge (5) separating the first and second fluid channels (3, 2); the flow field plate includes at least one lyophilic channel opposite to the surface of the membrane electrode assembly and a lyophilic channel opposite to the surface of the membrane electrode assembly Liquid-repellent channels with opposite surfaces, the above-mentioned channels are nested and arranged on the flow field plate body (1), and the channels are separated by ridges (5); the channels have first fluid inlets and outlets (7, 4) respectively . The second fluid outlet (6), the first fluid inlet, the outlets (7, 4) and the second fluid outlet (6) are all through holes. 2. A flow field plate with nested arrangement of lyophilic channels and lyophobic channels as claimed in claim 1, characterized in that, the lyophilic channels and lyophobic channels are in contact with the membrane electrode assembly in the flow field plane method The sum of the projected areas is 20% to 80% of the active area of the membrane electrode assembly; the contact angle of the liquid phase fluid on the surface of the lyophilic channel is less than 90°, and the contact angle on the surface of the lyophobic channel is ≥90°. 3. A flow field plate with nested arrangement of lyophilic channels and lyophobic channels as claimed in claim 1 or 2, characterized in that the lyophilic and lyophobic structures nested in the flow field plate are snakes Shaped flow field, parallel flow field, helical flow field or composite flow field.

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