Method for measuring and calculating the air permeability of a double-layered porous sheet

Abstract

The application relates to a kind of double-layer porous sheet air permeability measurement and calculation method, comprising the following steps: cutting double-layer porous sheet into ring disc sample and disc sample;Adopt the way of gas from inner ring to outer ring flow, measure the total air permeability R s Of ring disc sample;Adopt the way of gas from one disc to another disc flow, measure the total air permeability R d Of disc sample;Calculate the air permeability of each layer of double-layer sheet.Compared with prior art, the application has the advantages that by measuring two different shape samples by different methods and then calculating, the air permeability value of each layer can be obtained without delaminating the sheet; by measuring double-layer porous sheet including porous layer and carbon paper layer, the influence of porous layer on the air permeability of carbon paper body can be effectively distinguished.

Description

Technical Field

[0001] This invention relates to a method for measuring porous sheets, and more particularly to a method for measuring and calculating the air permeability of double-layer porous sheets. Background Technology

[0002] Carbon fiber paper (hereinafter referred to as carbon paper) is made from chopped carbon fibers and has a porous fibrous structure at the microscopic level, which can establish effective channels for the conduction of gas and water. Carbon paper also has advantages such as light weight, smooth surface, corrosion resistance, and uniform porosity. Furthermore, the high strength of carbon paper provides protection for the installation and use of PEMFC batteries, stabilizing the electrode structure and improving battery life. In addition, the manufacturing process of carbon paper is mature and its performance is stable; therefore, carbon paper has become the mainstream choice for gas diffusion layer materials in membrane electrodes. Current measurements of the permeability of carbon paper with porous layers obtain the combined effect of the porous layer and the carbon paper itself, but cannot obtain the permeability of the porous layer alone, nor can they effectively distinguish the influence of the porous layer on the permeability of the carbon paper itself.

[0003] A search revealed that application publication number CN218885319U discloses an apparatus for testing the permeability of carbon paper in fuel cells. Specifically, the apparatus includes an upper pressure plate and a lower pressure plate, with the upper pressure plate covering the lower pressure plate. The lower surface of the upper pressure plate and the upper surface of the lower pressure plate each have a recessed cavity, and each cavity contains a permeable plate that allows gas to flow. The carbon paper to be tested is sandwiched between the upper and lower pressure plates. An air inlet channel is provided on the side wall of the upper pressure plate, and an air outlet channel is provided on the side wall of the lower pressure plate. The air inlet channel communicates with the recessed cavity of the upper pressure plate, and the air outlet channel communicates with the recessed cavity of the lower pressure plate. The upper pressure plate has an upper vent hole, and the lower pressure plate has a lower vent hole, both of which are connected to a differential pressure gauge. The differential pressure gauge is configured to measure the gas pressure difference between the upper and lower pressure plates after the gas passes through the carbon paper.

[0004] However, this existing technology also does not disclose a method for measuring the air permeability of each layer of a double-layer sheet. Therefore, how to measure the air permeability of a double-layer carbon paper with porous layers is a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art in that it is impossible to measure the air permeability of double-layer porous carbon paper, and to provide a method for measuring and calculating the air permeability of double-layer porous sheets.

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

[0007] According to one aspect of the present invention, a method for measuring and calculating the air permeability of a double-layer porous sheet is provided, the method specifically including the following steps:

[0008] Step S1: Cut the double-layer porous sheet into ring-shaped samples and disc-shaped samples;

[0009] Step S2: Measure the total permeability R of the annular disc sample by allowing gas to flow from the inner ring to the outer ring. s ;

[0010] Step S3: Measure the total air permeability R of the disc-shaped sample by allowing gas to flow from one side of the disc to the other. d ;

[0011] Step S4: Calculate the air permeability of each layer of the double-layer sheet. The formulas for calculating the air permeability R1 and R2 of each layer of the double-layer sheet are as follows:

[0012]

[0013] As a preferred technical solution, step S2 specifically includes the following steps:

[0014] Step S201: Place the annular disc sample between two plates with holes, with the projection surface of the inner circle of the sample completely covering the holes.

[0015] Step S202: Measure the thickness of the sample when it is clamped;

[0016] Step S203: Ventilate through the hole and measure the pressure drop or flow rate of the gas passing through the sample.

[0017] Step S204: Calculate the total air permeability of the annular disc sample.

[0018] As a preferred technical solution, in step S203, the controlled variable is to fix the gas flow rate when measuring the gas pressure drop generated when the gas passes through the sample; and to keep the gas pressure drop generated when the gas passes through the sample constant when measuring the gas flow rate.

[0019] As a preferred technical solution, the thickness of the double-layer porous sheet is h; the inner radius of the annular disc sample is r. i The outer radius is r o .

[0020] As a preferred technical solution, the relationship between the inner radius and the outer radius is r. o >r i The relationship between the inner radius and the thickness is r. i >h; the relationship between the outer radius and the thickness is r o >h.

[0021] As a preferred technical solution, the total air permeability of the annular disc sample in step S204 Where Q is the gas flow rate, μ is the gas viscosity coefficient, ΔP is the gas pressure drop, and δ is the thickness of the annular sample sandwiched between two plates.

[0022] As a preferred technical solution, step S3 specifically includes the following steps:

[0023] Step S301: Place the disc-shaped sample in the fixture;

[0024] Step S302: Gas is introduced into the disc-shaped sample side inside the fixture, and the gas pressure drop or gas flow rate generated when the gas passes through the sample is measured.

[0025] Step S303: Calculate the total air permeability of the disc-shaped sample.

[0026] As a preferred technical solution, the thickness of the double-layer porous sheet is h; the radius of the disk-shaped sample is r. d The relationship between the radius and the thickness is r d >h.

[0027] As a preferred technical solution, in step S302, the controlled variable is to fix the gas flow rate when measuring the gas pressure drop generated when the gas passes through the sample; and to keep the gas pressure drop generated when the gas passes through the sample constant when measuring the gas flow rate.

[0028] As a preferred technical solution, in step S4, the double-layer sheet includes a porous layer and a carbon paper layer.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) This invention measures two samples of different shapes using different methods and then calculates the air permeability values ​​of each layer without having to peel the sheet into layers.

[0031] 2) This invention measures a double-layer porous sheet comprising a porous layer and a carbon paper layer, and can effectively distinguish the influence of the porous layer on the air permeability of the carbon paper body.

[0032] 3) This invention uses a controlled variable method to fix the gas flow rate when measuring the gas pressure drop generated when the gas passes through the sample; and keeps the gas pressure drop generated when the gas passes through the sample constant when measuring the gas flow rate. This method can be selected according to the actual equipment conditions and has a wide range of applications.

[0033] 4) The present invention places the annular disc sample between two plates with holes in one of them to conduct an air permeability test, which can effectively avoid the problem of inaccurate air permeability measurement caused by air leakage on the side of the sheet. Attached Figure Description

[0034] Figure 1 This invention provides a method for measuring and calculating the air permeability of a double-layer porous sheet. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] like Figure 1 As shown, this invention provides a method for measuring and calculating the air permeability of a double-layer porous sheet, the steps of which are as follows:

[0037] 1) Cut the double-layer porous sheet into ring-shaped and disc-shaped samples, wherein the thickness of the double-layer porous sheet is h; and the inner radius of the ring-shaped sample is r. i The outer radius is r o The relationship between the inner radius and the outer radius is r o >r i The relationship between the inner radius and the thickness is r. i >h; the relationship between the outer radius and the thickness is r o >h; the radius of the disk-shaped sample is r d The relationship between radius and thickness is r d >h;

[0038] 2) Measure the total air permeability R of the annular disc sample. s :

[0039] (1) Place the annular disc sample between two plates with holes, so that the projection surface of the inner circle of the sample completely covers the holes.

[0040] (2) Measure the thickness of the sample when it is clamped;

[0041] (3) Ventilate through the hole and measure the pressure drop or flow rate of the gas passing through the sample.

[0042] (4) Calculate the total air permeability R of the annular disc sample. s , Where Q is the gas flow rate, μ is the gas viscosity coefficient, ΔP is the gas pressure drop, and δ is the thickness of the annular sample sandwiched between two plates.

[0043] 3) Measure the total air permeability R of the disc-shaped sample. d :

[0044] (1) Place the disc-shaped sample in the fixture;

[0045] (2) Pour air into the disc-shaped sample side inside the fixture and measure the pressure drop or flow rate of the gas passing through the sample.

[0046] (3) Calculate the total air permeability of the disc-shaped sample;

[0047] 4) Calculate the air permeability of each layer of the double-layer sheet. The formulas for calculating the air permeability R1 and R2 of each layer of the double-layer sheet are as follows:

[0048]

[0049] When measuring annular and disc-shaped samples, a controlled variable method is used: when measuring the gas pressure drop generated when the gas passes through the sample, the gas flow rate is kept constant; when measuring the gas flow rate when the gas passes through the sample, the gas pressure drop generated when the gas passes through the sample is kept constant.

[0050] The aforementioned double-layer porous sheet includes a porous layer and a carbon paper layer.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring and calculating the air permeability of a double-layer porous sheet, characterized in that, The method specifically includes the following steps: Step S1: Cut the double-layer porous sheet into ring-shaped samples and disc-shaped samples; Step S2: Measure the total permeability R of the annular disc sample by allowing gas to flow from the inner ring to the outer ring. s ; Step S3: Measure the total air permeability R of the disc-shaped sample by allowing gas to flow from one side of the disc to the other. d ; Step S4: Calculate the air permeability of each layer of the double-layer sheet. The formulas for calculating the air permeability R1 and R2 of each layer of the double-layer sheet are as follows:

2. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 1, characterized in that, Step S2 specifically includes the following steps: Step S201: Place the annular disc sample between two plates with holes, with the projection surface of the inner circle of the sample completely covering the holes. Step S202: Measure the thickness of the sample when it is clamped; Step S203: Ventilate through the hole and measure the pressure drop or flow rate of the gas passing through the sample. Step S204: Calculate the total air permeability of the annular disc sample.

3. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 2, characterized in that, In step S203, the controlled variables are: when measuring the gas pressure drop generated when the gas passes through the sample, the flow rate of the gas is fixed; when measuring the gas flow rate when the gas passes through the sample, the gas pressure drop generated when the gas passes through the sample is kept constant.

4. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 2, characterized in that, The thickness of the double-layer porous sheet is h; the inner radius of the annular disc sample is r. i The outer radius is r o .

5. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 4, characterized in that, The relationship between the inner radius and the outer radius is r o >r i The relationship between the inner radius and the thickness is r. i >h; the relationship between the outer radius and the thickness is r o >h.

6. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 5, characterized in that, The total air permeability of the annular disc sample in step S204 Where Q is the gas flow rate, μ is the gas viscosity coefficient, ΔP is the gas pressure drop, and δ is the thickness of the annular sample sandwiched between two plates.

7. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 1, characterized in that, Step S3 specifically includes the following steps: Step S301: Place the disc-shaped sample in the fixture; Step S302: Gas is introduced into the disc-shaped sample side inside the fixture, and the gas pressure drop or gas flow rate generated when the gas passes through the sample is measured. Step S303: Calculate the total air permeability of the disc-shaped sample.

8. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 7, characterized in that, The thickness of the double-layer porous sheet is h; the radius of the disk-shaped sample is r. d The relationship between the radius and the thickness is r d >h.

9. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 7, characterized in that, In step S302, the controlled variables are: when measuring the gas pressure drop generated when the gas passes through the sample, the flow rate of the gas is fixed; when measuring the gas flow rate when the gas passes through the sample, the gas pressure drop generated when the gas passes through the sample is kept constant.

10. The method for measuring and calculating the air permeability of a double-layer porous sheet according to claim 1, characterized in that, In step S4, the double-layer sheet includes a porous layer and a carbon paper layer.

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