Micro-tube solid oxide fuel cell stack with uniform gas distribution

Abstract

The present application relates to the technical field of fuel cell, in particular to a micro-tube solid oxide fuel cell stack with uniform gas distribution, which comprises an outer shell and a plurality of solid oxide fuel cell tubes; the outer shell is provided with a fuel distributor and a fuel outlet cavity at two ends respectively, and a fluid cavity is formed between the outer shell, the fuel distributor and the fuel outlet cavity; the fuel distributor is provided with a fuel gas inlet and a fuel cavity; the two ends of the solid oxide fuel cell tube are connected with the fuel distributor and the fuel outlet cavity respectively; the solid oxide fuel cell tube is provided with a flow guide plate; the micro-tube solid oxide fuel cell stack with uniform gas distribution realizes the uniform distribution of fuel gas and the uniform flow of air side gas by optimizing the structure of fuel gas side and air side, which solves the problem of the influence of the poor gas distribution and the poor gas flowability in the solid oxide fuel cell stack on the performance of the stack and the long-term operation stability.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a microtubular solid oxide fuel cell stack with uniform gas distribution. Background Technology

[0002] In the operation of solid oxide fuel cell stacks, uniform gas distribution plays a decisive role in their performance. However, currently, many fuel cell stacks suffer from uneven gas distribution. This problem can lead to a series of serious consequences. From the perspective of electrochemical reaction kinetics, uneven gas concentration distribution disrupts the ideal ratio of reactant gases at each reaction site, preventing the reaction from proceeding according to the optimal stoichiometric ratio. Insufficient fuel gas distribution limits the anodic oxidation reaction rate and inhibits electron generation; while uneven air distribution weakens the cathodic reduction reaction, resulting in an overall reduction in the power output and energy conversion efficiency of the fuel cell stack.

[0003] Regardless of whether it's the anode or cathode, uneven gas distribution leading to differences in electrochemical reaction intensity ultimately results in varying heat generation within the battery, creating a significant temperature gradient. Since battery stacks are typically composed of various materials, such as ceramic electrolytes, metal electrodes, and connectors, these materials have different coefficients of thermal expansion. Therefore, when a large temperature gradient exists within the stack, the different degrees of thermal expansion in different temperature regions create constraint stresses, i.e., thermal stress. Prolonged exposure to this thermal stress can easily cause deformation and cracking of the battery assembly, especially at material interfaces where thermal stress concentration is more pronounced. This severely compromises the structural integrity of the battery assembly, reducing the reliability and lifespan of the battery stack. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a microtubular solid oxide fuel cell stack with uniform gas distribution, which realizes uniform distribution of fuel gas and uniform flow of air-side gas, thereby solving the impact of uneven gas distribution and poor gas flow on the stack performance and long-term operational stability caused by the uneven gas distribution and poor gas flow inside the solid oxide fuel cell stack.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A microtubular solid oxide fuel cell stack with uniform gas distribution includes: a shell and multiple solid oxide fuel cell tubes;

[0007] A fuel distributor and a fuel outlet are respectively provided at both ends of the outer shell, and a fluid cavity is formed between the outer shell, the fuel distributor and the fuel outlet;

[0008] The fuel distributor is provided with a fuel gas inlet and a fuel chamber, and the fuel gas inlet is connected to the fuel chamber.

[0009] The two ends of the solid oxide fuel cell tube are connected to the fuel distributor and the fuel outlet, respectively, and the solid oxide fuel cell tube is not in communication with the fluid cavity;

[0010] The outer casing is provided with at least one air inlet and at least one air outlet at each end, and both the at least one air inlet and at least one air outlet are in communication with the fluid cavity;

[0011] The solid oxide fuel cell tube is disposed inside the outer casing, and a flow guide plate is provided on the solid oxide fuel cell tube.

[0012] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein the fuel distributor includes: an arc-shaped plate and an anti-backflow structure;

[0013] The arc-shaped plate is used to achieve uniform distribution of fuel gas. The arc-shaped plate is located behind the anti-backflow structure and is fixedly connected to the anti-backflow structure.

[0014] The backflow prevention structure is located behind the fuel gas inlet;

[0015] The arc-shaped plate has a first air port, which is connected to the fuel chamber, and the first end of the solid oxide fuel cell tube is connected to the first air port.

[0016] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein the guide plate includes: a guide portion and a connecting portion;

[0017] The multiple solid oxide fuel cell tubes are connected to each other via the connecting portion.

[0018] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein a double-layer sealing structure is provided between the outer shell and the fuel distributor.

[0019] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein at least three guide plates are provided, and the at least three guide plates are spaced apart.

[0020] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein the fuel outlet is arranged in a funnel shape;

[0021] A connector is provided inside the fuel outlet chamber, and a second air port is provided on the connector. The end of the solid oxide fuel cell tube is connected to the second air port.

[0022] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein a sealing gasket is provided between the end of the solid oxide fuel cell tube and the second gas port, and the solid oxide fuel cell tube and the second gas port are sealed by the sealing gasket.

[0023] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein the fuel chamber is formed between the arcuate plate and the anti-backflow structure.

[0024] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein the convex surface of the arc-shaped plate is located within the fuel chamber, and the concave surface of the arc-shaped plate is located within the fluid chamber.

[0025] In at least one embodiment of the present disclosure, a microtubular solid oxide fuel cell stack with uniform gas distribution is provided, wherein there is a gap between adjacent solid oxide fuel cell tubes;

[0026] The central axis of the solid oxide fuel cell tube is parallel to the central axis of the outer casing.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. By incorporating a fuel distributor, uniform gas distribution can be achieved. The convex surface of the arc-shaped plate faces the fuel gas inlet, which causes most of the gas to flow along the arc to both sides after the airflow impacts the arc-shaped plate, preventing the fuel gas from concentrating in the central tube bundle and resulting in a more uniform gas distribution.

[0029] 2. The fuel distributor is equipped with an anti-backflow structure. The structure guides the airflow path and prevents gas backflow, which greatly improves safety. It not only prevents fuel gas from mixing with the outside air and causing danger, but also prevents back mixing, ensuring orderly gas flow in the fuel cell stack and improving the performance and reliability of the fuel cell stack.

[0030] 3. The airflow is guided by the baffle plate, which allows the airflow to pass through the entire tube bundle, avoiding performance differences and large temperature gradients caused by uneven flow between different battery tube bundles. In addition, the baffle plate can also make the air flow back and forth in multiple paths between the battery tube bundles, promote the contact between the air and the battery tube bundle, enhance the battery electrochemical reaction, and ultimately improve the performance of the battery stack.

[0031] 4. The air deflector can also guide airflow and promote battery heat transfer efficiency, reduce battery temperature gradient, thereby reducing battery thermal stress and improving battery long-term working stability.

[0032] 5. The baffle plate adopts a partitioned design. The part that contacts the solid oxide fuel cell tube is the connection part, which serves to connect the solid oxide fuel cell tube in series. The outer part of the connection part is the baffle section. This partitioned design makes use of the connection part between the baffle plate and the solid oxide fuel cell tube, avoiding the cost loss and space waste caused by adding an additional battery connector. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a perspective view of a microtubular solid oxide fuel cell stack with uniform gas distribution according to the present invention.

[0035] Figure 2 This is a cross-sectional view of a microtubular solid oxide fuel cell stack with uniform gas distribution according to the present invention.

[0036] Figure 3 This is a cross-sectional view of the fuel distributor.

[0037] Figure 4 This is a cross-sectional view of the fuel outlet.

[0038] Figure 5 This is a schematic diagram showing the connection between the tube and the guide plate of a solid oxide fuel cell.

[0039] Figure 6 This is a 3D view of the air deflector.

[0040] Figure 7 The velocity vector distribution at the inlet of the microtubular solid oxidation fuel cell stack (left) with uniform gas distribution and the stack without anti-backflow structure (right) are shown in the Fluent numerical simulation results.

[0041] Figure 8 The pressure contour plots at the inlet of the microtubular solid oxidation fuel cell stack (left) with uniform gas distribution and the stack without anti-backflow structure (right) are Fluent numerical simulation results.

[0042] Figure 9 The velocity contour plots are Fluent numerical simulation results of the air-side center section of the microtubular solid oxide fuel cell stack (left) with uniform gas distribution and the stack structure without baffles (right) in the embodiment.

[0043] Figure 10The Fluent numerical simulation results show the temperature contour plots of the air-side center section of the microtubular solid oxide fuel cell stack (left) with uniform gas distribution and the stack structure without baffles (right) in the embodiment.

[0044] In the picture:

[0045] 10. Outer shell; 11. Fuel distributor; 12. Fuel outlet chamber; 13. Fluid chamber; 14. Air inlet; 15. Air outlet; 111. Fuel gas inlet; 112. Fuel chamber; 113. Arc plate; 114. Anti-backflow structure; 115. First air port; 121. Connector; 122. Second air port;

[0046] 20. Solid oxide fuel cell tube;

[0047] 30. Deflector plate; 31. Deflector section; 32. Connecting section. Detailed Implementation

[0048] The technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments, not all embodiments.

[0049] Example 1

[0050] like Figure 1-4 As shown, a microtubular solid oxide fuel cell stack with uniform gas distribution includes a shell 10 and a plurality of solid oxide fuel cell tubes 20.

[0051] Specifically, a fuel distributor 11 and a fuel outlet chamber 12 are respectively provided at both ends of the outer casing 10, and a fluid cavity 13 is formed between the outer casing 10, the fuel distributor 11 and the fuel outlet chamber 12. The fuel distributor 11 is provided with a fuel gas inlet 111 and a fuel cavity 112, and the fuel gas inlet 111 and the fuel cavity 112 are connected.

[0052] Fuel gas inlet 111 is made of pipe, and a sealing gasket (not shown) is used to seal the fuel gas inlet 111 and the fuel distributor 11. The sealing gasket is made of silicon carbide ceramic material, which has high hardness and high strength, and can withstand the high-speed impact of fuel gas and the test of high-temperature environment. Its good thermal conductivity helps to dissipate heat evenly during the sealing process, avoiding the performance degradation of the sealing material due to local overheating. Under long-term actual operating conditions, the sealing gasket can maintain stable physical and chemical properties, ensuring the sealing of fuel chamber 112 and effectively preventing fuel gas leakage.

[0053] Specifically, the two ends of the solid oxide fuel cell tube 20 are connected to the fuel distributor 11 and the fuel outlet chamber 12, respectively, and the solid oxide fuel cell tube 20 is not connected to the fluid chamber 13.

[0054] Specifically, air inlets 14 and air outlets 15 are respectively provided at both ends of the outer casing 10, and both air inlets 14 and air outlets 15 are connected to the fluid cavity 13. Multiple air inlets 14 and air outlets 15 can be provided, and the number of air inlets 14 and air outlets 15 is determined according to actual conditions.

[0055] Specifically, the solid oxide fuel cell tube 20 is disposed inside the outer casing 10, and a flow guide plate 30 is disposed on the solid oxide fuel cell tube 20.

[0056] Specifically, a double-layer sealing structure (not shown) is provided between the housing 10 and the fuel distributor 11 to ensure the sealing performance between the housing 10 and the fuel distributor 11. The connection between the housing 10 and the fuel distributor 11 adopts a double-layer sealing structure (not shown), with the inner layer filled and sealed by high-temperature sealant, and the outer layer wrapped with a nickel-based alloy sealing sleeve to further enhance the sealing effect.

[0057] Specifically, there is a gap between adjacent solid oxide fuel cell tubes 20, and the central axis of the solid oxide fuel cell tube 20 is parallel to the central axis of the outer shell 10. Gaps are left between adjacent tubes to allow air to flow through; the solid oxide fuel cell tubes 20 are connected by guide plates to achieve series connection; the solid oxide fuel cell tubes 20 are connected to the fuel gas outlet, and the two are tightly fitted together by a sealing gasket (not shown) to form a closed cavity. The sealing gasket is also made of silicon carbide ceramic material.

[0058] For example, there are twenty solid oxide fuel cell tubes 20, which are arranged in a rectangular array.

[0059] In use, fuel gas enters through fuel gas inlet 111 and is evenly distributed by fuel distributor 11 to multiple solid oxide fuel cell tubes 20. Then, the fuel gas is discharged from multiple solid oxide fuel cell tubes 20 to fuel outlet 12 for further processing.

[0060] The structure of the fuel distributor will be further explained below with reference to the accompanying drawings.

[0061] like Figure 2 and 3 As shown, the fuel distributor 11 includes an arc-shaped plate 113 and an anti-backflow structure 114. After the fuel gas enters the fuel distributor, it is evenly distributed through the arc-shaped plate 113; in this process, the anti-backflow structure serves to reduce backflow.

[0062] The arc-shaped plate 113 is located behind the anti-backflow structure 114, and the arc-shaped plate 113 is fixedly connected to the anti-backflow structure 114; the anti-backflow structure is located behind the fuel gas inlet 111.

[0063] The arc plate 113 has a first air port 115, which is connected to the fuel chamber 112. The first end of the solid oxide fuel cell tube 20 is connected to the first air port 115.

[0064] The fuel chamber 112 is formed between the arc-shaped plate 113 and the anti-backflow structure 114.

[0065] The convex surface of the arc plate 113 is located inside the fuel chamber 112, and the concave surface of the arc plate 113 is located inside the fluid chamber 13.

[0066] During use, after the fuel gas enters the fuel distributor 11, it is evenly distributed to each solid oxide fuel cell tube 20 by the arc plate 113. During this process, the airflow collides with the arc plate 113, which will cause some gas to flow back. This part of the gas will be blocked by the anti-backflow structure 114. This not only prevents the fuel gas from flowing back and mixing with the outside air, thus avoiding danger, but also prevents the back mixing phenomenon caused by gas backflow, thereby improving the performance and reliability of the fuel cell stack.

[0067] The arc plate 113 is made of cordierite ceramic, which has a low coefficient of thermal expansion. This allows it to maintain good dimensional stability in the fuel cell stack environment with large temperature variations, preventing deformation of the orifice plate due to thermal expansion and contraction, which would affect the distribution of fuel gas. The anti-backflow structure is made of nickel-based alloy, which has excellent high-temperature strength and corrosion resistance, ensuring the long-term stable operation of the structure.

[0068] The structure of the deflector will be further explained below with reference to the accompanying drawings.

[0069] like Figure 5 and 6 As shown, the guide plate 30 includes a guide portion 31 and a connecting portion 32; multiple solid oxide fuel cell tubes 20 are connected to each other through the connecting portion 32. The various solid oxide fuel cell tubes 20 are connected through the connecting portion 32, thus achieving series connection of the solid oxide fuel cell tubes 20.

[0070] The connecting part 32 connects each solid oxide fuel cell tube 20, realizing the series connection of the cells. The flow guiding part 31, located on the outer periphery of the connecting part 32, guides the gas flow and realizes the gas reversal flow.

[0071] At least three deflectors 30 are provided, and the at least three deflectors 30 are distributed at intervals.

[0072] A flow guide plate 30 is used within the fluid cavity 13 to guide gas flow, thereby reducing dead zones and improving gas flow uniformity. Furthermore, the flow guide plate 30 can guide air to flow in multiple paths and periodically back and forth between the solid oxide fuel cell tubes 20, enhancing the battery's electrochemical reaction and improving the overall performance of the fuel cell stack.

[0073] The structure of the fuel outlet chamber will be further explained below with reference to the accompanying drawings.

[0074] like Figure 4 As shown, the fuel outlet chamber 12 is funnel-shaped; a connector 121 is provided inside the fuel outlet chamber 12, and a second gas port 122 is provided on the connector 121. The end of the solid oxide fuel cell tube 20 is connected to the second gas port 122.

[0075] A sealing gasket (not shown) is provided between the end of the solid oxide fuel cell tube 20 and the second gas port 122. The solid oxide fuel cell tube 20 and the second gas port 122 are also sealed with a sealing gasket, and the two are tightly fitted together by the sealing gasket. The sealing gasket is also made of silicon carbide ceramic material.

[0076] The effectiveness of the anti-backflow structure in the embodiments will be verified using computational fluid dynamics methods.

[0077] The model was built using SpaceClaim software. To simplify the calculation, only the inlet was modeled simply and scaled up proportionally to better demonstrate the structural effect. The model was then imported into Fluent Meshing to generate a mesh, which used a combination of polyhedral and hexahedral meshes. The generated mesh was then imported into Fluent for numerical simulation.

[0078] Fuel gas flow velocity: V = 10 m / s, using the k-ω model of turbulence equations. The flow within the fuel gas flow field is simulated. The fuel gas inlet is a uniformly distributed velocity inlet boundary, and the fuel gas outlet is a pressure outlet boundary with an outlet gauge pressure of 0 Pa and an operating pressure of 101325 Pa.

[0079] The model has an overall height of 370mm, a width of 420mm, an inlet diameter of 80mm, a backflow prevention structure height of 68mm, a width of 232mm, and a perforated arc plate height of 82mm, a width of 380mm, and a thickness of 5mm.

[0080] Available from Figure 7 This demonstrates that the anti-backflow structure plays a role in guiding gas flow. The anti-backflow structure is constructed using the anti-backflow principle of a Tesla valve. By guiding the backflow path, it causes the backflow branch to collide with the main backflow, thereby reducing backflow. Figure 8 The pressure distribution shows that compared to the original inlet without an anti-backflow structure, the internal pressure of the structure is significantly reduced after using the anti-backflow structure. This indicates that its flow stability is stronger, backflow is greatly reduced, and losses caused by backflow are significantly reduced.

[0081] The following section will use computational fluid dynamics to verify the effect of the guide vane structure in the embodiment on improving flow uniformity.

[0082] By modeling a real 100-watt 4×5 tubular fuel cell stack, the fluid flow characteristics were studied. To simplify calculations, only the air-side fluid domain of the stack was extracted and scaled up proportionally to better demonstrate the structural effect. The model was built using SpaceClaim software and then meshed in Fluent Meshing using a combination of polyhedral and hexahedral meshes. The meshed data was then imported into Fluent for numerical simulation.

[0083] Air velocity: V = 30 m / s, using the k-ω model of turbulence equations. The airflow field is simulated and calculated. The air inlet is a uniformly distributed velocity inlet boundary, and the air outlet is a pressure outlet boundary with an outlet gauge pressure of 0 Pa and an operating pressure of 101325 Pa.

[0084] The model has an overall height of 2000mm, a length × width of 400mm × 400mm, an inlet / outlet diameter of 50mm, and a guide vane that is 360mm long and 5mm thick.

[0085] Available from Figure 9 This shows that the deflector plays a role in guiding gas flow. By guiding the gas flow path, the deflector reduces gas flow unevenness. Figure 9 The velocity distribution shows that, compared to the fuel cell stack without a deflector, the low-velocity region (the dark blue area less than 1 m / s) is significantly reduced after the deflector is added, the velocity distribution of the fuel cell stack is more uniform, and it can be seen that the deflector enables the gas to flow back and forth periodically in the fuel cell stack.

[0086] The following section will use computational fluid dynamics to verify the effect of the baffle structure in the embodiment on reducing the temperature gradient.

[0087] By modeling a real 100-watt 4×5 tubular fuel cell stack, the fluid flow and heat conduction characteristics were studied. To simplify calculations, the battery tube bundle was simplified to a hollow tube, and the entire stack was scaled up proportionally to better demonstrate the structural effect. The model was built using SpaceClaim software and then meshed in Fluent Meshing using a combination of polyhedral and hexahedral meshes. The meshed data was then imported into Fluent for numerical simulation.

[0088] Air velocity: V = 30 m / s, using the k-ω model of turbulence equations. The airflow field was simulated. The air inlet was a uniformly distributed velocity inlet boundary, and the air outlet was a pressure outlet boundary with an outlet gauge pressure of 0 Pa. The operating pressure was 101325 Pa, and the temperature was set to 973 K. Each pipe was equipped with an 8.5 W heat source to simulate actual battery heating.

[0089] The model has an overall height of 2000mm, a length × width of 400mm × 400mm, an inlet / outlet diameter of 50mm, a guide plate length of 360mm, and a thickness of 5mm. The pipe has an outer diameter of 30mm and an inner diameter of 20mm.

[0090] Available from Figure 10 This shows that the guide vane plays a role in reducing the temperature gradient of the battery bundle. Through... Figure 9 The temperature distribution comparison shows that, compared with the stack without the deflector, the temperature gradient of each battery bundle is reduced (from the original 20K temperature gradient to 13K) after the deflector is added, and the temperature distribution is more uniform (the color is more uniform compared with the original stack).

[0091] Although embodiments of this application have been shown and described above, the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be conceived without inventive effort should be covered within the scope of protection of this invention. Unless expressly stated otherwise, no element, action or instruction used herein should be construed as critical or necessary.

Claims

1. A microtubular solid oxide fuel cell stack with uniform gas distribution, characterized in that, include: The outer casing and multiple solid oxide fuel cell tubes; A fuel distributor and a fuel outlet are respectively provided at both ends of the outer shell, and a fluid cavity is formed between the outer shell, the fuel distributor and the fuel outlet; The fuel distributor is provided with a fuel gas inlet and a fuel chamber, and the fuel gas inlet is connected to the fuel chamber. The two ends of the solid oxide fuel cell tube are connected to the fuel distributor and the fuel outlet, respectively, and the solid oxide fuel cell tube is not in communication with the fluid cavity; The outer casing is provided with at least one air inlet and at least one air outlet at each end, and both the at least one air inlet and at least one air outlet are in communication with the fluid cavity; The solid oxide fuel cell tube is disposed inside the outer casing, and a flow guide plate is provided on the solid oxide fuel cell tube; The fuel dispenser includes: Curved plate and anti-backflow structure; The arc-shaped plate is used to achieve uniform distribution of fuel gas. The arc-shaped plate is located behind the anti-backflow structure and is fixedly connected to the anti-backflow structure. The backflow prevention structure is located behind the fuel gas inlet; The arc-shaped plate has a first air port, which is connected to the fuel chamber, and the first end of the solid oxide fuel cell tube is connected to the first air port. The guide vane includes: Guide section and connecting section; The multiple solid oxide fuel cell tubes are connected to each other via the connecting portion; At least three guide vanes are provided, and the at least three guide vanes are distributed at intervals. The fuel chamber is formed between the arc-shaped plate and the anti-backflow structure; The convex surface of the arc-shaped plate is located inside the fuel chamber, and the concave surface of the arc-shaped plate is located inside the fluid chamber; There is a gap between adjacent solid oxide fuel cell tubes; The central axis of the solid oxide fuel cell tube is parallel to the central axis of the outer casing.

2. The microtubular solid oxide fuel cell stack with uniform gas distribution according to claim 1, characterized in that, A double-sealed structure is provided between the outer casing and the fuel distributor.

3. The microtubular solid oxide fuel cell stack with uniform gas distribution according to claim 1, characterized in that, The fuel outlet is funnel-shaped. A connector is provided inside the fuel outlet chamber, and a second air port is provided on the connector. The end of the solid oxide fuel cell tube is connected to the second air port.

4. A microtubular solid oxide fuel cell stack with uniform gas distribution according to claim 3, characterized in that, A sealing gasket is provided between the end of the solid oxide fuel cell tube and the second gas port, and the solid oxide fuel cell tube and the second gas port are sealed by the sealing gasket.

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