KR101051726B1 - Separator for fuel cell with rotating flow induction path of fluid, manufacturing method thereof and fuel cell using same - Google Patents

Abstract

Provided are a separator for a fuel cell equipped with a rotating flow guide path of a fluid, a method of manufacturing the same, and a fuel cell using the same. According to the separator for fuel cells, it is possible to improve the flow characteristics of reactants and products. This can lead to increased material transfer and improved fuel cell performance.

Fuel Cell, Separator, Flow Path, Fluid Rotating Flow, Spiral Groove

Description

Separator for fuel cell with fluid flow induction path, manufacturing method and fuel cell using same

The present invention relates to a separator for a fuel cell equipped with a rotary flow induction path of a fluid which is a reactant or a product, a method of manufacturing the same, and a technology for a fuel cell using the same.

In general, in the anode of a polymer electrolyte fuel cell, an oxidation reaction of a fuel such as hydrogen or methanol occurs to generate carbon dioxide, electrons, and ions.

The generated ions move to the reduction electrode through the electrolyte membrane and meet with oxygen to cause an electrochemical reaction to generate water, and the generated electrons move through an external circuit to perform electrical work.

The fuel cell using the polymer electrolyte membrane can solve the problems such as the limitation of the capacity of the secondary battery or the inconvenience caused by the charging time because of the advantage that the use time can be increased by supplying only fuel such as hydrogen or methanol.

Based on these advantages, a fuel cell using hydrogen may be used as an automobile power source or a home generator. In addition, in the case of a fuel cell using methanol as a fuel, methanol can be easily stored and transported and used as a battery replacement for portable electronic devices such as mobile phones, PDAs, and notebook PCs.

The basic structure of the polymer electrolyte fuel cell includes a cathode and an anode in which catalysts are disposed on both sides of the polymer electrolyte membrane, and a separator is located outside.

The separator is a passage for supplying a fuel such as hydrogen or methanol to the anode or an oxygen or air as an oxidant to the cathode, that is, a passage for supplying a reactant. In addition, the separator serves to collect electrons generated from the anode, and serves as a passage for removing a product such as water or carbon dioxide generated by battery operation.

By improving the flow path of the separator for fuel cells, the reactants are smoothly supplied to the catalyst layer while the smooth discharge of the products is induced to improve the flow characteristics (flow characteristics) of the reactants or products. Accordingly, it is possible to increase the material transfer and improve the performance of the overall fuel cell.

In an exemplary embodiment of the present invention, as a separator for a fuel cell, the separator has a valley that is a convex portion and a valley that is a recess that is relatively recessed with respect to the convex portion, and a valley portion, which is an area between the mountains and the acid, serves as a flow path. The flow path is provided with a separation plate for a fuel cell including at least one rotational flow induction path for guiding the fluid flow to proceed while rotating, a manufacturing method thereof and a fuel cell using the same. The rotating flow guide path of the fluid may be, for example, a spiral groove formed in the flow path.

Exemplary embodiments of the present invention may induce the fluid to proceed in rotation in the flow path of the separator plate for the fuel cell. This fluid rotational flow induction allows the reactant to be smoothly supplied to the catalyst bed, induces a smooth discharge of the product, and increases the fluid velocity in the flow path. As a result, the mass transfer rate at the electrode can be improved and the performance of the fuel cell can be improved.

In addition, in the exemplary embodiments of the present invention, it is possible to facilitate the adjustment of the flow characteristics by forming a fine fluid rotational flow induction path in the separator plate flow path for the fuel cell.

Hereinafter, a separator for a fuel cell equipped with a rotary flow induction furnace according to an exemplary embodiment of the present invention, a manufacturing method thereof, and a fuel cell using the same will be described in detail.

The separator consists of a region of convex portions (typically referred to as "mountains") and relatively recessed recesses (usually referred to as "corrugations") between the convex portions, wherein the region of the valleys between the acids is fluid This flow becomes the flow path, and reactants and products flow along this flow path.

When the reactant or the product flows through the flow path, it is possible to improve the flow characteristics of the reactant or the product and to adjust it easily by rotating. Rotational flow induction of the fluid as described above enables an increase in mass transfer rate of reactants and products between the flow path and the electrode and improvement of cell performance.

1A is a schematic diagram illustrating a separator for a fuel cell according to an exemplary embodiment of the present invention.

Referring to FIG. 1A, a fuel cell separator 200 according to an exemplary embodiment of the present invention induces a flow of fluid in a valley region between an acid and a valley of a separator plate (for example, a general howitzer separator plate) to proceed while rotating. For example, it has a structure in which one or more spiral grooves are repeatedly formed.

FIG. 1B conceptually shows that the flow of fluid is rotated by a helical groove which is a rotational flow guide path of the fluid in the separator 200. That is, according to the helical groove, the reactant or the product may proceed along the X direction (vertical direction in FIG. 1B) while rotating (S), and this rotating flow may be performed by the gas diffusion layer adjacent to the separator plate. It is possible to better feed the reactants to the adjacent catalyst layer.

In addition, as will be described in more detail below, by controlling the formation of the spiral grooves such as the number and height of the spiral grooves, the angle of rotation within the limited flow path, it is possible to easily control the flow characteristics of the fluid in the flow path, and furthermore the flow rate Can be increased, and the smooth supply of the reactants and the case where the discharge of the product is stagnant can be reduced, thereby improving the flow characteristics.

FIG. 2 is a conceptual diagram for analyzing flow characteristics when, for example, a spiral groove is formed in a flow path between an acid and an acid in a separator for a fuel cell according to an exemplary embodiment of the present invention. In FIG. 2, for example, the rotational direction of the spiral is set to the right, but the rotational direction of the spiral may be left or right.

The flow process in the case of fluid flowing along the spiral groove is analyzed in more detail as follows. However, for ease of analysis, a perfect tube-shaped flow path is assumed instead of the half-shaped flow path schematically shown in FIGS. 1 and 2. That is, the model is simplified through assumptions to intuitively consider the fluid flow due to the spiral groove.

Referring to FIG. 2, R is the inner radius of the tube in the case of assuming a tube, θ is the angle of the helical groove to the direction of progress of the tube (that is, the angle of rotation of the helical groove), r is the rib of the linear groove ) (The height of the helical groove), n is the number of helical grooves, w is the width of the helical groove.

Fluid flow characteristics in a tube having a spiral groove may be represented by Equation 1 below (Chem. Eng. Sci., 62, 4202, 2007).

Where u is the velocity of the fluid, ㅿ P is the pressure drop across the tube, f is the friction factor, ρ is the fluid density, A _c is the cross-sectional area of the tube, and A _w is the internal wetting area.

If the height (r) of the spiral groove is small enough relative to the radius (R) of the tube, the tube-side pressure drop (ㅿ P), the cross-sectional area of the tube (A _c ) and the internal wetting area ( The difference of A _w ) can be ignored. That is, ㅿ PA _c / A _w can be represented by a constant.

In this case, the speed change of the fluid depending on the presence or absence of the spiral groove may be expressed as follows. That is, for any type A tube with or without a helical groove to another type B tube with or without a helical groove, the ratio of the velocity of the fluid is frictional as shown in Equation 2 below. Can be influenced by coefficients.

In a spiral grooved tube, the coefficient of friction can be derived as shown in Equation 3 below (R. L. Webb, R. Narayanamurthy, P. Thors, J. Heat Transfer, 122, 134, 2000).

Where Re is the number of Reynolds, n is the number of spiral grooves, r is the height of the spiral groove, R is the radius of the tube (the radius of the euro), and θ is the angle of the spiral groove.

From Equations 2 and 3, the following Equation 4 can be derived.

As can be seen from Equation 4, when introducing a spiral groove, n (number of spiral grooves) in order to adjust the flow rate (increase u _B / u _A > 1, ie, u _B > u _A ), It is possible to determine the design of the spiral groove by changing r (height of the spiral groove) and θ (rotation angle of the spiral groove), thereby manufacturing a separator plate having a spiral groove.

As a non-limiting example, when n = 5, r = 0.1mm, θ = 45 ^o [substitute in [Equation 4] with n _A = 5, r _A = 0.1 mm, θ _A = 45 ^o ] and n = 4, when r = 0.05mm, θ = 30 ^o [n _B = 4, r _B = 0.05 mm, θ _B = 30 ^o and substituted in [Equation 4]], the latter (type B) fluid velocity It is faster than the former (type A).

On the other hand, the coefficient of friction applied to the tube of the smooth shape without the spiral groove can be expressed as shown below (J. O. Wilkes, Fluid Mechanics for Chemical Engineer).

Therefore, when there are spiral grooves (type B in [Equation 6] below) and when there are no spiral grooves by using [Equation 2], [Equation 3] and [Equation 5], and there is no spiral groove (Equation 6 below) A type) is as follows.

As a non-limiting example, the number of spiral grooves (n) is 6 (n = 6), the height of the spiral grooves is 1/100 of the flow path width (diameter) (r / 2R = 1/100), and When the rotation angle is 30 ^o (θ = 30 ^o ), it can be seen that the flow velocity increases (u _B / u _A > 1, that is, u _B > u _A ) by the formation of the spiral groove.

As described above, it can be seen that the flow characteristics can be easily adjusted by changing the number of the spiral grooves, the rotation angle of the spiral grooves, and the height of the spiral grooves when the spiral grooves are formed to induce the rotational flow of the fluid. .

In addition, as can be seen in Equation 4, the adjustment of the flow characteristics is generally influenced more by the height of the spiral groove and the angle of the spiral groove than by the number of spiral grooves. Therefore, in the adjustment (increase) of the flow characteristic, it is desirable to perform the height adjustment of the spiral groove and / or the angle of the spiral groove.

In this regard, in the manufacture of a separator plate in which the actual spiral groove is formed, the spiral groove is finely formed in the flow path, and since the separation plate itself is made of a carbon material such as graphite, the formation of the spiral groove in the flow path requires very precise work. .

Therefore, in forming the spiral groove by forming the spiral groove in the flow path, if the shape parameters of the spiral groove related to the flow characteristics are minimized and simplified, the manufacturing process of the separator may be very easy while improving the flow characteristics. There is this.

Therefore, in exemplary embodiments, the flow rate is adjusted by adjusting any one or more of the number of spiral grooves, the height of the spiral grooves, the angle of the spiral grooves, more preferably the height of the spiral grooves and / or the angle of the spiral grooves. Do it.

On the other hand, the analysis based on the above model makes it easier to adjust (increase) the flow rate based on a simplified model such as assuming a flow path in the form of a tube for an intuitive consideration of fluid flow characteristics and not considering a pressure drop. This is an analysis made from the point of view.

In any case, however, the formation of at least a helical groove to induce rotational flow of the fluid is advantageous for mass exchange with the catalyst layer in the electrode as shown in FIG. A structure can be obtained.

Even in the case of not neglecting the pressure drop, the tube cross-sectional area, etc. in a real flow passage other than the simplified model as described above, the width of the helical groove (in reference to FIG. Referring to 2, denoted by w ) and height (referenced to FIG. 2, denoted by r) refer to the width of the passage (reference, W1 or W2, referring to FIG. 4) and the depth of the passage (reference). As shown in FIG. 2, it was confirmed that it is preferable to adjust the amount to more than 0% and about 66.7% or less (2/3 or less) with respect to R, which is the radius of the flow path, respectively. For reference, the width of the spiral groove may reflect information on the number of spiral grooves. Since the number of spiral grooves in the actual flow path may vary depending on the size of the flow path, information about the number of spiral grooves may be reflected by setting the width of the spiral groove as a ratio to the width of the flow path.

Here, the angle of the spiral groove is preferably to be 1 degree to 90 degrees.

1 and 2, the spiral grooves are formed in the valleys of the curved partition plate, but the ridges, parallel, and island-shaped mountains and mountains, that is, the recesses formed between the convex portions and the convex portions, that is, the valleys are formed. It will be apparent to those skilled in the art that helical grooves may be formed in the region.

Thus, in exemplary embodiments of the present disclosure, a pattern of a separator plate in which, for example, a spiral groove is formed by the fluid rotational flow induction as described above may be, for example, serpentine, interdigited, parallel ( It can be either parallel or island, or can be a composite separator in which two or more forms are combined.

The pattern of the flow path may be formed in two or more patterns than in a single pattern such as serpentine, interdigited, parallel or island, but in an area adjacent to the inlet side of the separator plate. If the pattern is compounded to increase the number of inflection points, the point where the flow direction of the flow path changes toward the area adjacent to the outlet side, the contact area between the fuel and the electrode can be increased and the reactants and products can be increased, rather than using a single flow path shape. Has the advantage of further improving the flow characteristics. It is further described below.

As the separator goes from the inlet to the outlet, the performance of the fuel cell may decrease. This is due to the decrease in the electrochemically active area and the increase in resistance due to the degradation of the catalyst. The amount of reactants decreases toward the outlet of the separator, and a local potential difference may occur due to flooding caused by the accumulation of generated water, thereby causing degradation of the catalyst. As such, if the delivery of the reactants or the removal of the product is not performed smoothly, the concentration overpotential increases. Therefore, a decrease in performance may be seen in the separator plate region adjacent to the outlet direction rather than the separator plate region adjacent to the inlet direction.

As a result of the study of the present inventors, it was confirmed that the fuel cell performance increases locally at the inflection point which is the point where the flow direction of the separator flows. This local performance increase is thought to be realized by local vortex formation at the inflection point.

Therefore, in the exemplary embodiments of the present specification, the inflection point, which is a point at which the flow direction of the fluid changes while inducing the rotational flow of the fluid in the region of the flow path, becomes more and more from the inlet to the outlet of the separator plate of the fuel cell. Configure to increase. According to this, in the separator of the fuel cell, the performance of the fuel cell decreases from the inlet to the outlet of the separator in an efficient manner, thereby improving the flow characteristics of the reactants and products and further improving the performance of the fuel cell.

One non-limiting example of increasing the inflection point is to use the pattern of the separator as a composite pattern. For example, by dividing an area of a separator plate of a fuel cell and using different patterns of flow paths (first flow path and second flow path) in two adjacent areas (first area and second area) among the partitioned areas. It can be configured as a pattern. At this time, in order to improve the flow characteristics, the number of inflection points in the second flow path of the second area is increased rather than the number of inflection points in the first flow path of the first area.

As such an example, the flow path pattern of the separator plate may be curved-> island, pod-> island, parallel-> island, parallel-> pod, parallel-> bowl, howitz-> pod. can do. This is because the inflection points in the flow path pattern are many in the order of island shape, pod shape, howitzer shape, and parallel type.

As another example, the composite pattern may be configured by forming the first region, the second region, and the third region and forming different patterns in each region. For example, it can be parallel-> curved-> pod, parallel-> pod-> island, curved-> pod-> island. In addition, it is possible to form a composite pattern by forming different patterns in the four areas, for example, it may be configured to be parallel-> curved-> pod-> island.

As described above, particularly when the island-like pattern is disposed in the outlet side region, it is advantageous in terms of increasing the contact area between the fuel and the electrode, improving flow characteristics and improving water discharge. In addition, the formation of the island-like flow path has a structure capable of increasing the generation of vortices to improve the flow characteristics as described above.

For reference, Figure 3 is a schematic diagram showing a separator for a fuel cell having a composite pattern in an exemplary embodiment of the present invention. Referring to FIG. 3, in the fuel cell separator 200 according to an exemplary embodiment of the present invention, the composite pattern 230 of the flow path is an curved pattern 231 in the first region (the inlet side region) and the second region. It is an island pattern 232 (outlet side region).

In addition to the rotational flow of the fluid is basically formed by the spiral groove in such a separator plate, in particular, the generation of vortex is facilitated in the outlet side flow path of the separator plate to further improve the flow characteristics of the outlet side flow path, thereby Emissions can be made easier.

Here, it is preferable to limit the formation rate of an island channel. That is, the battery performance increases as the island-shaped flow path is formed to a certain level at a point close to the outlet side, but when it exceeds a certain level, the battery performance may not increase further. Therefore, it is desirable to limit the ratio of forming the island-like flow paths. It is preferable that the formation rate of an island flow path is the ratio of more than 0 to 1/3 of the area of all the separating plates. The ratio may vary depending on the size of the separator, such as the size of the separator, the ratio of the width and length.

The widths of the peaks and valleys formed in the above curved, pod, parallel, island, or two or more composite pattern flow paths of the pattern can be variously formed.

By way of non-limiting example, the width of the mountain may be 0.2 to 3.0 millimeters, the width of the valley may be 0.2 to 3.0 millimeters, and the depth of the valley may be 0.1 to 2.0 millimeters. In addition, the cross-sectional shape of the mountain portion may be formed in a triangle, trapezoid, semi-circle, etc. in addition to the rectangular, square.

In another exemplary embodiment of the present disclosure, by changing one or more selected from the width or depth of the flow path from the inlet side to the outlet side of the separator plate can adjust the linear velocity and increase the possibility of forming the vortex. For example, the width of the flow path, i.e., the width between the mountains can be narrowed or the depth of the flow path can be reduced.

4 is a schematic view showing that the width of the flow passage narrows from the inlet side to the outlet side in an exemplary embodiment of the present specification. For reference, in FIG. 4, in order to prevent ambiguity in the drawing, the spiral grooves are omitted in the corresponding flow path without being separately indicated.

Referring to FIG. 4, in the fuel cell separator 200 having a spiral groove, the flow paths 231 and 232 of the first area and the flow paths 231 and 232 of the second area are connected to the second flow path in the first flow path 231. Towards 232), the width of the flow path decreases.

Therefore, the width W2 of the second flow path 232 is formed to be smaller than the width W1 of the first flow path 231. As such, by decreasing the width of the second flow path 232 adjacent to the outlet of the separator 200, the linear velocity can be increased, thereby facilitating the discharge of unreacted reactants and products.

Of course, by decreasing the depth of the flow passage from the first flow passage to the second flow passage, the flow characteristics of the first flow passage and the second flow passage can be different from each other, which also increases the linear velocity, thereby increasing the amount of unreacted reactants and products. Emissions can be facilitated.

On the other hand, in addition to adjusting the width or depth of the flow path for each region (eg, the first region and the second region) of the separator from the viewpoint of increasing the fluid velocity, as shown in Equation 4 above, n By changing the number of the spiral grooves, the height of the spiral grooves, and the rotation angle of the spiral grooves, the fluid velocity can be adjusted in each area of the separation plate.

For example, n (the number of spiral grooves), r (height of the spiral grooves) in the first region and the second region according to Equation 4 to increase the fluid velocity in the second region rather than the first region, θ (the rotation angle of the spiral groove) can be determined.

By partitioning the area of the separator as above, and adjusting the number, height, and rotation angle of the spiral grooves for each area, the speed of the fluid can be easily adjusted (increased) from the first region to the second region of the separator. have.

In order to manufacture the above separator, methods such as machining, injection or molding, stamping, and etching may be used. The material of the separator is preferably graphite, metal, composite graphite, ceramic, and a material having a corrosion resistant coating formed on these materials.

As described above, by inducing a rotating flow of the fluid by forming a spiral groove in the flow path of the separator, for example, the reactant can be smoothly supplied to the catalyst layer, and the product can be smoothly discharged. . As a result, mass transfer can be improved and fuel cell performance can be improved.

Furthermore, by controlling the shape variables such as changing the pattern or width of the fluid flow in the separator plate, and the direction of the flow of the fluid, the flow characteristics of the reactants and products having the above-described rotational flow are further controlled. It can further improve and further improve the performance of the fuel cell.

1A is a schematic diagram illustrating a separator for a fuel cell according to an exemplary embodiment of the present invention.

FIG. 1B conceptually illustrates the flow of fluid by a spiral groove which is a rotational flow guide path of the fluid in the separator shown in FIG. 1A.

FIG. 2 is a conceptual diagram for analyzing flow characteristics when, for example, a spiral groove is formed in a flow path between an acid and an acid in a separator for a fuel cell according to an exemplary embodiment of the present invention.

3 is a schematic view showing a separator for a fuel cell having a composite pattern in an exemplary embodiment of the present invention.

4 is a schematic view showing that the width of the flow passage narrows from the inlet side to the outlet side in an exemplary embodiment of the present specification.

Claims (12)

As a separator for a fuel cell, The separating plate has a convex portion and a concave portion, and a flow path is formed by the valley that is an area between the mountains. The flow path includes a rotational flow guide path of the fluid to induce the fluid flow to proceed while rotating, Separation plate for a fuel cell, characterized in that one or more selected from the width or depth of the flow path is reduced from the inlet side to the outlet side of the separation plate. The method of claim 1, Separation plate for a fuel cell, characterized in that the rotating flow guide path of the fluid is a spiral groove. The method of claim 2, The width and the height of the spiral groove is a fuel cell separator, characterized in that more than 0% and 66.7% or less with respect to the width and depth of the flow path, respectively. The method of claim 3, wherein Separation plate for a fuel cell, characterized in that the rotation angle of the spiral groove is 1 degree to 90 degrees. The method according to any one of claims 1 to 4, The separator has two or more regions having different flow path patterns, The number of inflection points, which is a point where the flow direction of the flow path in the region increases from the region adjacent to the inlet side of the separation plate of the region toward the region adjacent to the outlet side increases. The method of claim 5, The flow pattern of the separator is a fuel cell, characterized in that the serpentine (interdigited), parallel (parallel) or island (island) pattern. The method of claim 6, The separator includes a first flow path pattern formed in an area adjacent to the inlet side of the separator and a second flow path pattern formed in an area adjacent to the outlet side of the separator, The first flow path pattern is any one of serpentine, interdigitated, or parallel. The second flow path pattern is a separator for a fuel cell, characterized in that the island pattern (island) pattern. The method of claim 7, wherein The area of the region in which the second flow path is formed has a ratio of more than 0 1/3 of the total area of the separator plate. delete A fuel cell comprising the separator for fuel cell according to any one of claims 1 to 4. As a method of manufacturing a separator for a fuel cell, The convex portion and the concave portion are formed in the separator so that the flow path is formed by the valley that is the region between the mountains. At least one helical groove is formed in the flow path to guide the flow of the fluid as it rotates, And at least one selected from the width or the depth of the flow path from the inlet side to the outlet side of the separator plate. The method of claim 11, Method of manufacturing a separator for a fuel cell, characterized in that for controlling the flow rate of the fluid one or more of the number of the spiral groove, the height of the spiral groove or the rotation angle of the spiral groove.

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