KR20080045789A - Cooling plate for fuel cell including coolant flow channels of constant flow rate - Google Patents

Abstract

A cooling plate for a fuel cell is provided to cool the surface of a battery cell evenly by maintaining the constant flow rate of coolant flowing through respective coolant flow channels. A cooling plate(200) for a fuel cell including coolant flow channels of a constant flow rate has manifolds(210,220) at the inlet side and outlet side, and many coolant flow channels(230'). The length(L) of each coolant flow channel is controlled in proportion to a pressure normalization distribution function. The difference in pressure of the respective coolant flow channels is calculated by a computational fluid dynamic technique using geometric characteristic values of the cooling plate and inherent property values of a coolant.

Description

Cooling plate for fuel cell including coolant flow channels of constant flow rate

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, serve to further understand the technical spirit of the present invention. It should not be construed as limited to.

1 is a top plan view illustrating a refrigerant flow channel of a cooling plate for a fuel cell according to the prior art.

FIG. 2 is a partially enlarged perspective view of the refrigerant flow channel illustrated in FIG. 1.

3 is a top plan view illustrating a refrigerant flow channel of a cooling plate for a fuel cell according to a preferred embodiment of the present invention.

FIG. 4 shows the inlet pressure P _in , the outlet pressure P _out , and the pressure difference ΔP between the inlet and outlet sides of each refrigerant flow channel having a constant channel length shown in FIG. 1. This graph shows the results calculated using Fluid Dynamics (CFD).

FIG. 5 is a graph illustrating a pressure normalization distribution function derived to normalize the pressure difference ΔP of each refrigerant flow channel illustrated in FIG. 4 based on the average of the pressure differences.

FIG. 6 is a graph showing the length of each refrigerant flow channel converted using the pressure normalization distribution function shown in FIG. 5.

FIG. 7 shows the results of comparing the refrigerant flow rates of the case where the length of each refrigerant flow channel is adjusted and the case where the length of each refrigerant flow channel is the same as in the related art, and then comparing them with each other after calculating the computational fluid dynamics. Is a graph.

<Description of Major Reference Marks in Drawing>

200 ... Cooling plate 210 ... Inlet side manifold

220 ... outlet side manifold 230 ... parallel type refrigerant flow channel section

230 ... refrigerant flow channel

The present invention relates to a cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel, and more specifically, to each refrigerant flow by adjusting the length or width of each refrigerant flow channel by Computational Fluid Dynamics (CFD) technique. The present invention relates to a fuel cell cooling plate in which the flow rate of the refrigerant flowing through the channel is made uniform.

In general, a fuel cell electrochemically reacts hydrogen contained in a hydrocarbon-based material such as methanol, ethanol, or natural gas with oxygen to produce water and at the same time extracts electricity to the outside (ie, Developing eco-friendly power generation device. Therefore, fuel cells are continuously being researched and developed for use as electric energy sources for electric vehicles, hybrid vehicles, space aircraft, portable electronic devices, and the like.

The fuel cell includes a cell unit. The fuel cell includes a cathode plate having a flow path for flowing a hydrogen-based gaseous fuel, an anode plate having a flow path for allowing air containing oxygen to flow, the cathode plate and A membrane-electrode assembly (MEA) interposed between the anode plates and having a material film stack structure of "diffusion layer (-) / catalyst layer (-) / electrolyte membrane / catalyst layer (+) / diffusion layer (+)". Include. Referring to the operation mechanism of the fuel cell having such a structure, the gaseous fuel diffuses through the diffusion layer (-) to the catalyst layer (-) and then dissociates into hydrogen ions while releasing electrons from the catalyst layer (-). The dissociated hydrogen ions move to the catalyst layer (+) through the electrolyte membrane, and the released electrons are taken out through the conductor and used as electrical energy. Hydrogen ions transferred to the catalyst layer (+) react with oxygen diffused through the diffusion layer (+) to the catalyst layer (+) to generate water, and the generated water is discharged to the outside through a flow path formed in the negative electrode plate.

On the other hand, since the power that can be produced by one fuel cell is not large, the commercially available fuel cell includes a stack in which a plurality of fuel cell cells are stacked as many as necessary. The fuel cell stack chemically separates the stacked cells and at the same time a separator for electrically connecting the cells is interposed between the upper and lower cells, and cools the heat generated in the process of generating electricity in the unit cell of the fuel cell. Insert a cooling plate in the middle of the cell to maintain the temperature of the fuel cell properly.

1 is a top plan view illustrating a refrigerant flow channel of a cooling plate for a fuel cell according to the prior art, and FIG. 2 is a partially enlarged perspective view of the refrigerant flow channel shown in FIG. 1.

1 and 2, the conventional cooling plate 100 includes an inlet manifold 110 into which a refrigerant flows in order to cool reaction heat generated in a fuel cell reaction area LX * LY, and a fuel cell. An outlet side manifold 120 for discharging the refrigerant having a higher temperature by recovering the heat generated therefrom, and a parallel type refrigerant flow channel unit 130 for effectively securing a heat transfer area and ensuring a uniform contact time of the refrigerant. Include.

The refrigerant flow channel unit 130 is composed of a plurality of refrigerant flow channels 130 'having the same channel length, each refrigerant flow channel 130' is a predetermined width (W), as shown in FIG. Having a height H and a length L, adjacent refrigerant flow channels 130 ′ are separated from one another by partition walls having a predetermined width R.

Based on the flow rate Q (cell) of the refrigerant flowing through the inlet side manifold 110 of the cooling plate 100, the ideal refrigerant flow flow rate flowing through any one refrigerant flow channel 130 ', Q (ch ) Is as shown in Equation 1 below.

(In formula, Q (ch): refrigerant flow rate of each refrigerant flow channel, Q (cell): refrigerant inflow flow rate per cooling plate cell, N: number of partitions forming the channel.)

In practice, however, the flow rate, Q (ch), passing through each refrigerant flow channel 130 'is proportional to the pressure difference at both ends of the channel and the channel spacing and inversely proportional to the length of the channel. However, since the pressure at each end of each refrigerant flow channel depends on the relative distance from the inlet manifold 110 or the outlet manifold 120, even if the channel length and width are the same, each refrigerant flow channel 130 ' The flow rate of the refrigerant passing through will show some deviation.

In each refrigerant flow channel 130 ′, the width W and height H have sufficiently small values relative to the length L of the channel. Therefore, the flow rate of the refrigerant passing through each refrigerant flow channel 130 ′ is proportional to the pressure difference ΔP across the channel as in Equation 2 below, and is inversely proportional to the channel length L.

(In formula, Q (ch) is the refrigerant flow rate of each refrigerant flow channel, ΔP is the pressure difference across each channel, L is the length of each channel, and k is the proportional constant.)

In Equation 2, the proportional constant k is a constant obtained by fluid dynamics and is calculated through Equation 3 below.

(Wherein, W is the width of each channel, H is the height of each channel, and μ is the fluid viscosity.)

Referring to the proportional constant k, since the factors used to calculate the proportional constant are all related to the geometry of the refrigerant flow channel and the inherent properties of the refrigerant, the flow rate of the refrigerant flowing through each refrigerant flow channel 130 ' It can be seen that the pressure difference ΔP and the channel at both ends are predominantly determined by the length L.

However, looking at the structure of the conventional cooling plate 100 described above, the width (W) and the length (L) of each refrigerant flow channel 130 'is the same, and the inlet side manifold 110 and the outlet side manifold ( Since the distances between the 120 and each of the refrigerant flow channels 130 'are all different, according to Equation 2, the pressure difference ΔP of each refrigerant flow channel 130' is not equal to each other, and as a result, each refrigerant flow channel ( The flow rate of the refrigerant flowing to 130 ') shows a deviation. When the variation in the refrigerant flow rate for each refrigerant flow channel 130 'is caused, the cooling of the fuel cell is not uniform, resulting in a problem that the safety of the fuel cell is lowered.

The present invention has been made to solve the above problems of the prior art, in the fuel cell cooling plate having a parallel type flow channel to uniform the flow rate of the refrigerant flowing through each refrigerant flow channel to improve the surface of the battery cell It is an object to provide a cooling plate for a fuel cell that can be cooled uniformly.

In order to achieve the above object, a fuel cell cooling plate according to an aspect of the present invention is a fuel cell cooling plate having a refrigerant inlet and an outlet side manifold and a plurality of refrigerant flow channels, each refrigerant flow channel. It is characterized in that the length of is adjusted to be proportional to the pressure normalized distribution function.

Preferably, the length L _#n of the flow path of each of the refrigerant flow channels (#n: n-th channel) is an average value P _ave of the pressure difference ΔP _#n and the pressure difference of each refrigerant flow channel. ) Is defined as the value calculated by substituting the average value L _ave of the pressure normalization distribution function value F _#n and the length of each refrigerant flow channel (#n) calculated by substituting .

<First Equation>

(In equation, ΔP _#n : pressure difference across each channel, P _ave : average value of pressure difference across each channel, F _#n : pressure normalization distribution function for each channel.)

<Equation 2>

(In formula, L _#n : length of each channel, L _ave : average value of each channel length, F _#n : pressure normalization distribution function for each channel.)

In the present invention, the length L _#n of each flow path of each refrigerant flow channel is defined as a value calculated by repeating the flow path length calculation process using the first and second equations at least twice.

A fuel cell cooling plate according to another aspect of the present invention for achieving the above technical problem is in the fuel cell cooling plate having a refrigerant inlet and outlet side manifold, and a plurality of refrigerant flow channels, The width is characterized in that it is adjusted in inverse proportion to the pressure normalized distribution function.

Preferably, the width W _#n of the flow path of each refrigerant flow channel (#n), the pressure difference (ΔP _#n ) and the average value (P _ave ) of the pressure difference of each of the refrigerant flow channel (1) The pressure normalized distribution function value F _#n calculated by substituting into and the flow path width average value W _ave of each of the refrigerant flow channels #n are defined as values calculated by substituting the following second equation.

<First Equation>

(In equation, ΔP _#n : pressure difference across each channel, P _ave : average value of pressure difference across each channel, F _#n : pressure normalization distribution function for each channel.)

<Equation 2>

(In formula, W _{#n is the} width of each channel, W _ave is the average value of each channel width, F _#n is the pressure normalization distribution function for each channel.)

In the present invention, the width W _{# n} of each flow path of each refrigerant flow channel is defined as a value calculated by repeating the flow path width calculation process using the first and second equations at least twice.

Preferably, the pressure difference of each of the refrigerant flow channels is calculated by computational fluid dynamics techniques using the geometrical characteristic values of the cooling plate and the intrinsic properties of the refrigerant.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, it is possible to replace them at the time of the present application It should be understood that there may be various equivalents and variations.

3 is a top plan view illustrating a refrigerant flow channel of a cooling plate for a fuel cell according to a preferred embodiment of the present invention.

Referring to FIG. 3, the cooling plate 200 according to the present invention includes an inlet manifold 210 into which a refrigerant flows in order to cool reaction heat generated in a fuel cell reaction area LX * LY, and a fuel cell. The outlet-side manifold 220 for discharging the refrigerant whose temperature has risen by recovering the heat generated therefrom, and a parallel type refrigerant flow in which the refrigerant flow rate is uniform in order to effectively secure a heat transfer area and to ensure uniform contact time of the refrigerant. The channel unit 230 is included. Each refrigerant flow channel 230 ′ included in the refrigerant flow channel unit 230 has a predetermined width W, height H, and length L (see FIG. 2). The refrigerant flow channels 230 ′ are separated from each other by partition walls having a predetermined width R.

According to the present invention, the refrigerant flow channel 230 'of the cooling plate 200 is designed based on Equation 2 to uniformize the flow rate of the refrigerant flowing through each refrigerant flow channel 230'. That is, since the flow rate of the refrigerant flowing through each refrigerant flow channel 230 'is proportional to the pressure difference across the channel and inversely proportional to the channel length, the variation of the pressure difference across each refrigerant flow channel 230' is adjusted by adjusting the length of the channel. To offset.

Specifically, the present invention, first, the cooling plate 200, such as the height (H), width (W), length (L), inlet and outlet side manifold (210, 220) of each refrigerant flow channel constant channel length The pressure difference (ΔP) across each refrigerant flow channel is calculated by computational fluid dynamics using the data defining the geometry of and the inherent properties of the refrigerant (viscosity, temperature, etc.).

FIG. 4 uses computational fluid dynamics to calculate the inlet pressure P _in , the outlet pressure P _out , and the pressure difference ΔP between the inlet and outlet sides of each refrigerant flow channel having a constant channel length shown in FIG. 1. It is a graph showing the result of the calculation.

Referring to FIG. 4, the pressure difference ΔP _#n across each refrigerant flow channel having a constant channel length indicates that the refrigerant flow channel (near Y = 0.05m) located near the inlet and outlet side manifolds 210 and 220. It can be seen that the pressure difference is large compared to the refrigerant flow channels (near Y = 0 and 0.1 m) at positions spaced apart from the inlet and outlet side manifolds 210 and 220.

Next, an average (P _ave) of the pressure difference (ΔP _#n) and the pressure difference (ΔP _#n) calculated for each refrigerant flow channel by a computational fluid dynamics pressure by applying the equation (4) normalize the distribution function F _#n Obtain Here, the pressure normalization distribution function F _#n normalizes the pressure difference of each refrigerant flow channel based on the average of the pressure difference.

(In equation, ΔP _#n : pressure difference across each channel, P _ave : average value of pressure difference across each channel, F _#n : pressure normalization distribution function for each channel.)

FIG. 5 is a graph illustrating a pressure normalization distribution function derived to normalize the pressure difference of each refrigerant flow channel illustrated in FIG. 4 based on the average of the pressure differences.

Referring to FIG. 5, the pressure normalization distribution function has a distribution similar to that of FIG. 4 showing the pressure difference of the refrigerant flow channel having a constant channel length, and the refrigerant flow channel at the position closest to the inlet and outlet side manifolds 210 and 220. It can be seen that the value of the distribution function decreases as it has a peak value and moves away from the inlet and outlet manifolds 210 and 220.

After the pressure normalization distribution function is calculated using Equation 4, the length L of the refrigerant flow channel having a constant channel length is changed according to Equation 5 using the calculated distribution function F _{# n} .

(In formula, L _#n : length of each channel, L _ave : average value of each channel length, F _#n : pressure normalization distribution function for each channel.)

FIG. 6 is a graph showing the length of each refrigerant flow channel converted using the pressure normalization distribution function shown in FIG. 5.

As shown in FIG. 6, the length L of the channel in the center of the cooling plate 200 having a large pressure difference ΔP _#n across the refrigerant flow channel is long, and the pressure difference ΔP _#n across the channel. It can be seen that the length L of the channel at the periphery of the cooling plate 200 is small.

FIG. 7 shows the results of comparing the refrigerant flow rates of the case where the length of each refrigerant flow channel is adjusted and the case where the length of each refrigerant flow channel is the same as in the related art, and then comparing them with each other after calculating the computational fluid dynamics. Is a graph.

Referring to FIG. 7, when the length L of each refrigerant flow channel 230 ′ is adjusted according to the exemplary embodiment of the present invention, it can be seen that the flow rate variation of the refrigerant flowing through the channel of each channel is reduced. When the flow rate variation of the refrigerant flowing through each refrigerant flow channel 230 ′ is reduced, the refrigerant flow rate flowing through each refrigerant flow channel 230 ′ may be made uniform.

The process of calculating the pressure normalized distribution function F _#n using Equations 4 and 5 and adjusting the length L of each refrigerant flow channel 230 'by the calculated distribution function F _#n is repeated several times. Can be. That is, the pressure difference ΔP _#n of each refrigerant flow channel 230 'is calculated by computational fluid dynamics based on the changed length L of the refrigerant flow channel 230', and the calculated pressure difference for each refrigerant flow channel is calculated. Substituting the average value P _ave of (ΔP _#n ) and the pressure difference (ΔP _#n ) into Equation 4, the pressure normalized distribution function F _#n is recalculated, and the recalculated distribution function F _#n and the refrigerant flow channel The length L of each refrigerant flow channel 230 'is readjusted by substituting the average value L _ave for the length L of 230' into Equation 5. When this process is repeated once again, the uniformity of the flow rate of the refrigerant flowing through each refrigerant flow channel 230 'is further increased, and thus the flow rate of the refrigerant flowing through each refrigerant flow channel 230' is also more uniform. do.

In the above-described embodiment, the length L of each refrigerant flow channel 230 'is adjusted to make the amount of refrigerant flow through each refrigerant flow channel 230' uniform. However, it is also possible to adjust the width W of each refrigerant flow channel 230 'to equalize the refrigerant flow amount.

That is, after calculating the pressure normalization distribution function F _{# n} by applying Equation 4, the average value (W _ave ) for the width (W) of each refrigerant flow channel 230 'and the pressure corresponding to each refrigerant flow channel The width W of each refrigerant flow channel 230 ′ may be adjusted by substituting the normalized distribution function value into Equation 6 below.

(In formula, W _{#n is the} width of each channel, W _ave is the average value of each channel width, F _#n is the pressure normalization distribution function for each channel.)

When the width W of each refrigerant flow channel 230 'obtained through Equation 6 is applied to the cooling plate 200, each channel is adjusted in the same manner as in the case of adjusting the length L of each flow channel 230'. The flow rate of the refrigerant flowing through the flow path of the refrigerant can be reduced to make the refrigerant flow amount uniform.

Through the equations (4) and (6), the process of adjusting the width W of each refrigerant flow channel 230 'may be repeated several times. In this case, the flow rate variation of the refrigerant flowing through each refrigerant flow channel 230 ′ may be reduced, thereby making the refrigerant flow amount more uniform.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

According to the present invention, in the fuel cell cooling plate having the parallel refrigerant flow channel, the flow rate of the refrigerant flowing through each refrigerant flow channel can be made uniform, and thus the electric cell surface can be cooled uniformly. In addition, by using the design technique of the refrigerant flow channel employed in the present invention, it is possible to effectively reflect the changes in various shape conditions and operating conditions of the refrigerant flow channel.

Claims (7)

A fuel cell cooling plate comprising a refrigerant inlet side and an outlet side manifold and a plurality of refrigerant flow channels, The length of each refrigerant flow channel is adjusted to be proportional to the pressure normalization distribution function Cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel. The method of claim 1, The length L _#n of the flow path of each of the refrigerant flow channels (#n: n-th channel), The pressure normalization distribution function value F _{# n} calculated by substituting the pressure difference ΔP _#n of the respective refrigerant flow channels and the average value P _ave of the pressure difference into the following equation and the respective refrigerant flow channels #n Cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel, characterized in that it is defined as a value calculated by substituting the length average value L _ave of the formula into the following second equation. <Equation 1>

(In equation, ΔP _#n : pressure difference across each channel, P _ave : average value of pressure difference across each channel, F _#n : pressure normalization distribution function for each channel.) <Equation 2>

(In formula, L _#n : length of each channel, L _ave : average value of each channel length, F _#n : pressure normalization distribution function for each channel.) The method of claim 2, The length L _#n of the flow path of each refrigerant flow channel is, Cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel, characterized in that the flow rate calculated by repeating the flow path length calculation process using the first and second equations at least two or more times. A fuel cell cooling plate comprising a refrigerant inlet side and an outlet side manifold and a plurality of refrigerant flow channels, Cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel, characterized in that the width of each refrigerant flow channel is adjusted in inverse proportion to the pressure normalization distribution function. The method of claim 4, wherein The width W _#n of the flow path of each refrigerant flow channel (#n), The pressure normalization distribution function value F _{# n} calculated by substituting the pressure difference ΔP _#n of the respective refrigerant flow channels and the average value P _ave of the pressure difference into the following equation and the respective refrigerant flow channels #n Cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel, characterized in that the flow path width average value W _ave of) is defined by the value calculated by substituting the following equation. <First Equation>

(In equation, ΔP _#n : pressure difference across each channel, P _ave : average value of pressure difference across each channel, F _#n : pressure normalization distribution function for each channel.) <Equation 2>

(In formula, W _{#n is the} width of each channel, W _ave is the average value of each channel width, F _#n is the pressure normalization distribution function for each channel.) The method of claim 5, Width W _{# n} of the flow path of each of the refrigerant flow channels, Cooling plate for a fuel cell with a uniform flow rate for each refrigerant flow channel, characterized in that the flow rate calculated by repeating at least two times the flow path calculation process using the first and second equations. The method according to any one of claims 1 to 6, The pressure difference between each refrigerant flow channel is calculated by a computational fluid dynamics method using the geometric characteristics of the cooling plate and the intrinsic properties of the refrigerant, the cooling plate for fuel cells with a uniform flow rate for each refrigerant flow channel.

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