Battery pack

Abstract

The present invention relates to a battery pack. More specifically, the battery pack of the present invention, which houses a cell stack assembly including a plurality of cells, includes a pack case in which the cell stack assembly is mounted, the pack case including a lower plate supporting a lower portion of the mounted cell stack assembly, a hollow side wall coupled to the lower plate to support a side of the cell stack assembly and including a gas exhaust passage therein, and an auxiliary partition coupled to the lower plate and the side wall to define an internal space of the pack case, the auxiliary partition including a gas passage therein communicating with the gas exhaust passage of the side wall.

Description

[Technical Field]

[0001] The present invention relates to a battery pack, and more specifically, the battery pack of the present invention is characterized in that it can block the influence of the gas on adjacent cell stack assemblies by discharging high-temperature gas generated in any one cell stack assembly to the outside using an auxiliary partition wall interposed between cell stack assemblies and having a gas flow path formed therein.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0068268, filed June 3, 2022, and Korean Patent Application No. 10-2023-0049566, filed April 14, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference. [Background technology]

[0003] Types of secondary batteries include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel metal hydride batteries, and nickel zinc batteries. The operating voltage of such a unit secondary battery cell, i.e., a unit battery cell, is approximately 2.5V to 4.2V. Therefore, if a higher output voltage is required, a battery pack may be configured by connecting a plurality of battery cells in series. Alternatively, a battery pack may be configured by connecting a number of battery cells in parallel depending on the required charge / discharge capacity of the battery pack. Therefore, the number of battery cells included in the battery pack may be variously set depending on the required output voltage or charge / discharge capacity.

[0004] For example, when a battery pack is constructed by connecting a plurality of battery cells in series or parallel, a common method is to first construct a battery module consisting of a plurality of battery cells, and then use the plurality of battery modules to construct the battery pack by adding other components. That is, a battery module refers to a component in which a plurality of secondary batteries are connected in series or parallel, and a battery pack refers to a component in which a plurality of battery modules are connected in series or parallel to increase capacity, output, etc.

[0005] Meanwhile, in such a battery pack with a multi-battery module structure, it is important to easily release high-temperature gases generated in each battery module. If the high-temperature gases generated during the charge and discharge process are not effectively removed, heat accumulation occurs, which can accelerate deterioration of the battery modules and, in some cases, cause fires or explosions. Furthermore, the heat from the gases can be transferred to other battery modules that are still operating normally, which can cause problems such as deterioration or explosion of all battery modules housed inside the battery pack. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 10-2018-0112617 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a battery pack that can quickly discharge high-temperature gas to the outside when deterioration occurs in one of a plurality of cell stack assemblies and the gas is released.

[0008] Another object of the present invention is to provide a battery pack that can prevent the heat of a cell stack assembly from being transferred to another adjacent cell stack assembly when deterioration occurs in one of a plurality of cell stack assemblies and high-temperature gas is released.

[0009] Other objects and advantages of the present invention can be understood from the following description and will become more apparent from the embodiments of the present invention. Also, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof as claimed. [Means for solving the problem]

[0010] According to the present invention, there is provided a battery pack comprising: a pack case in which a cell stack assembly is mounted; and an auxiliary partition wall coupled to the pack case to define an internal space of the pack case, wherein the pack case comprises a lower plate supporting a lower portion of the mounted cell stack assembly; and a hollow side wall coupled to the lower plate to support a side of the cell stack assembly and including a gas exhaust channel therein; and the auxiliary partition wall is coupled to the lower plate and the side wall of the pack case and includes a gas channel therein that communicates with the gas exhaust channel of the side wall.

[0011] The auxiliary partition wall may have an open surface coupled to the side wall such that the gas passage is connected to the gas discharge passage of the side wall.

[0012] The auxiliary partition may include an intake hole on a side surface corresponding to the gas flow path.

[0013] At least one suction hole may be formed on a side surface of the auxiliary partition.

[0014] The pack case may further include a main partition wall extending across a center of the lower plate, and both ends of the auxiliary partition wall may be connected to the main partition wall and the side wall, respectively.

[0015] The auxiliary partitions may be disposed on the lower plate at predetermined intervals along the main partition.

[0016] The auxiliary partition may include a partition wall formed inside the auxiliary partition to extend along a longitudinal direction of the auxiliary partition and to partition the gas flow path, the partition wall may include a main partition portion formed inside the auxiliary partition to extend in a thickness direction of the auxiliary partition and to partition the gas flow path, and the gas flow path may include a pair of first gas flow paths formed by being partitioned by the main partition portion of the partition wall.

[0017] The partition wall may include a sub-partition portion extending from the main partition portion to an inner surface of the auxiliary partition wall and partitioning the first gas passage in a thickness direction of the auxiliary partition wall.

[0018] The first gas flow path may include a plurality of second gas flow paths formed by being partitioned by sub-separation portions of the partition wall.

[0019] The suction holes may be formed on one side of the auxiliary partition wall to be connected to all of the second gas passages.

[0020] The second gas flow path may be connected to the gas exhaust path of the side wall.

[0021] The pack case may include an exhaust hole on at least one of the front and rear surfaces, the exhaust hole being open to the outside to allow gas to enter and exit.

[0022] The gas exhaust path may be formed to extend along a longitudinal direction of the sidewall and connected to the exhaust hole.

[0023] The cross-sectional area of ​​the gas discharge passage may be larger than the cross-sectional area of ​​the gas passage. [Effects of the Invention]

[0024] According to the present invention, even if deterioration occurs in the cell stack assembly and high-temperature gas is generated, the cell stack assembly can be prevented from catching fire or exploding.

[0025] Furthermore, the present invention can prevent the phenomenon of heat transfer caused by high-temperature gas generated in a cell stack assembly being transferred to another adjacent cell stack assembly. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a plan view of a battery pack according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a side wall of a battery pack according to a first embodiment of the present invention. [Figure 3] 1 is a partial perspective view of a battery pack according to a first embodiment of the present invention. [Figure 4] 3 is a perspective view of an auxiliary partition included in the battery pack according to the first embodiment of the present invention. FIG. [Figure 5] FIG. 2 is a side view of an auxiliary partition wall of the battery pack according to the first embodiment of the present invention. [Figure 6] 3 is a cross-sectional view of an auxiliary partition wall of the battery pack according to the first embodiment of the present invention. FIG. [Figure 7] 1 illustrates the movement direction of gas generated in a module space located adjacent to both sides of an auxiliary partition included in a battery pack according to a first embodiment of the present invention. [Figure 8] 3 is a partial cross-sectional view of an auxiliary partition wall of the battery pack according to the first embodiment of the present invention. [Figure 9] 1 illustrates a portion of a side wall included in a battery pack according to a first embodiment of the present invention. [Figure 10] 1 is a simplified diagram illustrating the connection between an auxiliary partition wall and a side wall of a battery pack according to a first embodiment of the present invention. [Figure 11] 10 shows a modified example of a side wall of the battery pack according to the first embodiment of the present invention. [Figure 12]1 is a partially enlarged view of a battery pack according to a first embodiment of the present invention. [Figure 13] FIG. 10 is a perspective view of an auxiliary partition included in a battery pack according to a second embodiment of the present invention. [Figure 14] FIG. 10 is a partial perspective view of a battery pack to which an auxiliary partition wall of a battery pack according to a second embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Before that, the terms and words used in the specification and claims should not be interpreted as being limited to their general or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to best describe his / her own invention.

[0028] Therefore, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can replace them at the time of this application.

[0029] Furthermore, in the description of the present invention, if it is determined that a detailed description of related publicly known structures or functions may obscure the gist of the present invention, the detailed description will be omitted.

[0030] The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and therefore the shapes and sizes of components in the drawings may be exaggerated, omitted, or illustrated schematically for clearer explanation. Therefore, the sizes and proportions of each component do not completely reflect the actual sizes and proportions.

[0031] The battery pack (1000) of the present invention accommodates a plurality of cell stack assemblies, and the accommodated cell stack assemblies are electrically connected in series and / or parallel so that the battery pack (1000) has one output.

[0032] The cell stack assembly includes a plurality of cells electrically connected to each other. Specifically, the cell stack assembly includes a cell stack including a plurality of cells stacked in one direction, and bus bar frames each including a bus bar electrically connected to an electrode lead of the cell stack, the bus bar frames being coupled to the front and rear surfaces of the cell stack, respectively.

[0033] If necessary, the cell stack assembly may further include end plates coupled to the bus bar frame to protect the bus bar frame from external impact.

[0034] The cell stack assembly may further include a module frame that surrounds the cell stack to protect the sides of the cell stack and is coupled to the bus bar frame or the end plate.

[0035] 1 to 12 relate to a battery pack (1000) according to a first embodiment of the present invention, and FIGS. 13 and 14 relate to a battery pack (1000) according to a second embodiment of the present invention.

[0036] Hereinafter, the battery pack 1000 of the present invention will be described in each embodiment with reference to the above drawings.

[0037] (First embodiment) FIG. 1 shows a plan view of a battery pack (1000) of the present invention.

[0038] Referring to FIG. 1, the battery pack (1000) of the present invention includes a pack case and an auxiliary partition (200).

[0039] The pack case provides a space in which the cell stack assembly is seated, and includes a bottom plate (110) and a side wall (130).

[0040] The lower plate (110) corresponds to the bottom of the battery pack (1000) and serves to support the lower portion of the cell stack assembly accommodated in the battery pack (1000).

[0041] The side walls 130 serve to support the sides of the cell stack assembly located on the lower plate 110. Specifically, the side walls 130 extend along the edges of the lower plate 110 and are connected to the ends of the lower plate 110.

[0042] The side wall (130) has a hollow structure including a gas discharge channel (131) therein.

[0043] FIG. 2 shows a cross section of a portion of the side wall (130) included in the battery pack (1000) of FIG.

[0044] As shown in FIG. 2, the side wall (130) includes a gas discharge passage (131) that is open inside and through which gas can move.

[0045] The pack case may further include a main partition wall (120) extending across the center of the lower plate (110).

[0046] The main partition wall 120 divides the space in which the cell stack assembly is housed into two halves.

[0047] The auxiliary partition (200) is coupled to the pack case so as to define an internal space of the pack case.

[0048] Specifically, the auxiliary partitions 200 partition the internal space of the pack case and are connected to the lower plate 110. Therefore, each cell stack assembly is separated and seated in the space partitioned by the auxiliary partitions 200.

[0049] The auxiliary partitions (200) serve to separate the cell stack assemblies and also to support the cell stack assemblies from both sides.

[0050] The auxiliary partition (200) is coupled to the bottom plate (110) and the side wall (130) of the pack case.

[0051] When the main partition wall 120 is not used, both ends of the auxiliary partition wall 200 are coupled to the side walls 130 provided at positions opposite to each other. When the main partition wall 120 is used, both ends of the auxiliary partition wall 200 are coupled to the main partition wall 120 and the side walls 130, respectively.

[0052] Two adjacent cell stack assemblies are separated from each other by the auxiliary partition wall (200) and housed in the battery pack (1000).

[0053] As shown in FIG. 1, the auxiliary partition walls (200) are arranged on the lower plate (110) at a predetermined interval along the main partition wall (120), and it is preferable that the interval between the pair of spaced auxiliary partition walls (200) is equal to or longer than the width of the cell stack assembly.

[0054] The battery pack (1000) of the present invention is finally partitioned by combining the pack case and the auxiliary partition (200), and includes a plurality of module spaces (300) partitioned by the main partition (120), side walls (130), and auxiliary partition (200) of the pack case.

[0055] FIG. 3 is a partial perspective view of the battery pack (1000) of FIG.

[0056] Referring to FIG. 3, the module space (300) is surrounded by the main partition wall (120), the side wall (130), and the auxiliary partition wall (200).

[0057] The plurality of cell stack assemblies can be separated from one another, with one cell stack assembly accommodated in each module space (300).

[0058] The auxiliary partition (200) of the present invention includes therein a gas flow passage (230) which communicates with the gas discharge passage (131) of the side wall (130).

[0059] FIG. 4 is a perspective view of an auxiliary partition (200) included in a battery pack (1000) according to the first embodiment of the present invention, FIG. 5 is a side view of the auxiliary partition (200) of FIG. 4, and FIG. 6 is a cross-sectional view of the auxiliary partition (200) of FIG. 4.

[0060] As shown in the figure, the auxiliary partition wall (200) has a hollow structure including a gas flow passage (230) therein.

[0061] The auxiliary partition wall 200 has an intake hole 210 formed through the side wall 130 of the auxiliary partition wall 200 so as to connect the gas flow passage 230 to the module space 300 adjacent to the auxiliary partition wall 200. That is, the auxiliary partition wall 200 has an intake hole 210 on the side surface corresponding to the internal gas flow passage 230.

[0062] The intake hole (210) can connect the module space (300) to the gas flow path (230) of the auxiliary partition wall (200) adjacent to the module space (300), and when gas is generated in the cell stack assembly housed in the module space (300), the gas can flow into the gas flow path (230) through the intake hole (210).

[0063] A plurality of the suction holes (210) may be formed on one side of the auxiliary partition wall (200).

[0064] Preferably, the suction holes (210) are formed on both sides of the auxiliary partition (200).

[0065] 7 shows the movement direction of gas generated in the module spaces 300 located adjacent to both sides of the auxiliary partition 200. Since each module space 300 is sealed except for the intake holes 210, when gas is generated in the cell stack assembly housed in the module space 300, the gas released from the cell stack assembly flows into the intake holes 210 of the adjacent auxiliary partition 200 and moves along the gas movement path Gpth shown in FIG.

[0066] The gas flow passages (230) included in the auxiliary partition wall (200) are connected to different module spaces (300) through suction holes (210) formed on both sides of the auxiliary partition wall (200).

[0067] As shown in FIGS. 4 and 6, the auxiliary partition wall (200) includes a separation wall (220) extending along the longitudinal direction of the auxiliary partition wall (200) and defining the gas flow path (230).

[0068] The separation wall (220) includes one main separation section (220a) and a plurality of sub-separation sections (220b).

[0069] Specifically, the main separator (220a) extends in the thickness direction of the auxiliary partition (200) so that the gas passage (230) is divided into two parts with the main separator (220a) at the center.

[0070] The gas flow passage (230) includes a pair of first gas flow passages (230a) defined by the main separating portion (220a) of the separating wall (220).

[0071] Therefore, even if gas generated in one of the module spaces (300) flows into the first gas flow path (230a) of the auxiliary partition wall (200), it is blocked by the main separation part (220a) of the separation wall (220) and does not flow back into the adjacent module space (300).

[0072] The sub-separator (220b) is formed to extend from the main separator (220a) to the inner surface of the auxiliary partition (200) and includes a sub-separator (220b) that divides the first gas flow path (230a) in the thickness direction of the auxiliary partition (200).

[0073] The sub-separator 220b may be formed on both sides of the main separator 220a, and it is preferable that at least one sub-separator 220b is included on one side of the main separator 220a.

[0074] The first gas flow passage (230a) includes a plurality of second gas flow passages (230a1) formed by being partitioned by the sub-separation portions (220b) of the partition wall (220).

[0075] That is, the gas flow path (230) inside the auxiliary partition (200) of the present invention may be divided into a pair of first gas flow paths (230a) by the main separation portion (220a) of the partition wall (220), and the divided first gas flow paths (230a) may be further divided into a plurality of second gas flow paths (230a1) by the sub-separation portions (220b) of the partition wall (220).

[0076] The plurality of second gas passages (230a1) formed on one side of the main separation part (220a) are preferably connected to the same suction hole (210).

[0077] FIG. 8 shows a partial cross section of the auxiliary partition wall (200) of FIG.

[0078] 8, a cross section of the auxiliary partition wall 200 at the portion where the suction hole 210 is formed shows that a plurality of second gas flow passages 230a1 are connected to one suction hole 210. That is, gas generated in the module space 300 flows into the auxiliary partition wall 200 through the suction hole 210 of the auxiliary partition wall 200 adjacent to the module space 300, and the flowed-in gas simultaneously travels through a plurality of second gas flow passages 230a1 formed by the separation walls 220 inside the auxiliary partition wall 200. However, as shown in the figure, the flowed-in gas is prevented from flowing into the gas flow passage 230 located on the opposite side by the main separation part 220a, and is not transmitted to the adjacent module space 300.

[0079] As shown in FIG. 4, the auxiliary partition wall (200) has an open surface coupled to the side wall (130) so that the gas passage (230) is connected to the gas discharge passage (131) of the side wall (130).

[0080] 9 shows a portion of the side wall 130 without the auxiliary partition 200. As shown in FIG. 9, an insertion hole 132 into which the auxiliary partition 200 is inserted is formed on the inner surface of the side wall 130.

[0081] The auxiliary partition 200 is coupled to the side wall 130 such that the opening on the side is inserted into the insertion hole 132 of the side wall 130. That is, the opening on the side of the auxiliary partition 200 is inserted into the insertion hole 132 of the side wall 130 such that the gas passage 230 is connected to the gas discharge passage 131 of the side wall 130.

[0082] 10 shows a simplified view of the connection between the auxiliary partitions (200) and the side walls (130), in which a plurality of auxiliary partitions (200) are connected to one side wall (130). In this case, each auxiliary partition (200) is joined to the side wall (130) such that the gas flow path (230) is connected to the gas discharge path (131) of the side wall (130).

[0083] Referring to the gas transfer path (Gpth) in Figure 10, the gas generated in the module space (300) moves through the gas flow path (230) of the auxiliary partition (200), then flows into the gas discharge path (131) of the side wall (130) connected to the auxiliary partition (200), and moves along the side wall (130).

[0084] The cross-sectional area of ​​the gas discharge passage 131 of the side wall 130 is preferably larger than the cross-sectional area of ​​the gas passage 230 of the auxiliary partition 200 so that gas generated in the module space 300 and moving through the gas passage 230 can move more smoothly to the gas discharge passage 131. That is, the gas moving into the gas passage 230 can move more smoothly toward the gas discharge passage 131, which has a larger spatial volume than the gas passage 230 and is therefore under lower pressure.

[0085] The spatial volume of the gas discharge passage 131 is larger than the spatial volume of the second gas passage 230a1 inside the auxiliary partition 200. Therefore, the gas that flows through the second gas passage 230a1 and enters the gas discharge passage 131 may not flow back into the second gas passage 230a1.

[0086] FIG. 11 shows a modification of the side wall (130).

[0087] Referring to FIG. 11, the side wall (130) includes an auxiliary suction hole (133) that opens to the inner surface facing the module space (300).

[0088] The auxiliary intake hole (133) connects the gas discharge passage (131) inside the side wall (130) to the module space (300), and allows the gas generated in the module space (300) to directly flow into the gas discharge passage (131).

[0089] The battery pack 1000 of the present invention includes an exhaust hole 400 connected to the gas exhaust passage 131 of the side wall 130 and open to the outside. That is, the gas exhaust passage 131 extends along the length of the side wall 130 and opens to the outside through at least one of the front and rear surfaces of the pack case.

[0090] FIG. 12 is a partially enlarged view of the battery pack (1000) according to the first embodiment of the present invention.

[0091] 12, gas moving along the gas flow passage 230 of the auxiliary partition 200 and the gas discharge passage 131 of the side wall 130 is discharged to the outside of the battery pack 1000 through the exhaust hole 400. Therefore, gas generated in the module space 300, moving through the gas flow passage 230, and flowing into the gas discharge passage 131 can move along the gas discharge passage 131 and then be discharged to the outside of the battery pack 1000 through the exhaust hole 400.

[0092] (Second embodiment) FIG. 13 is a perspective view of an auxiliary partition (200) included in a battery pack (1000) according to a second embodiment of the present invention.

[0093] 13, the suction holes 210 may be formed to extend longitudinally along the longitudinal direction of the auxiliary partition wall 200. That is, the suction holes 210 are formed to extend longitudinally along the longitudinal direction of the auxiliary partition wall 200, so that the second gas flow passages 230a1 are all widely open to the module space 300.

[0094] FIG. 14 is a partial perspective view of a battery pack (1000) to which the auxiliary partition (200) of FIG. 13 is applied.

[0095] In Figures 13 and 14, the intake holes (210) formed extending long along the auxiliary partition (200) allow the high-temperature gas generated in the module space (300) to flow into and move through the gas flow path (230) of the auxiliary partition (200) in a shorter time than in the first embodiment.

[0096] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations described in the drawings or embodiments in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, so it should be understood that there may be various equivalents and modifications that can replace them at the time of filing this application. [Explanation of symbols]

[0097] 1000: Battery pack 110: Lower board 120: Main bulkhead 130: Side wall 131: Gas exhaust channel 132: Insertion hole 133: Auxiliary intake hole 200: Auxiliary bulkhead 210: Intake hole 220: Separation wall 220a: Main separation section 220b: Sub-separation section 230: Gas flow path 230a: first gas flow path 230a1: second gas flow path 300: Module Space 400: Exhaust hole G pth : Gas transfer path

Claims

1. A battery pack containing a cell stack assembly including a plurality of cells, a pack case in which the cell stack assembly is seated; an auxiliary partition wall coupled to the pack case to partition an internal space of the pack case; Including, The pack case is a lower plate supporting a lower portion of the seated cell stack assembly; a hollow sidewall connected to the lower plate to support a side of the cell stack assembly and including a gas exhaust channel therein; Including, the auxiliary partition wall is coupled to a bottom plate and a side wall of the pack case and includes a gas flow path therein communicating with the gas exhaust path of the side wall, a separation wall formed inside the auxiliary partition wall and extending along a longitudinal direction of the auxiliary partition wall to divide the gas flow path, the partition wall includes a main partition portion extending in a height direction of the auxiliary partition wall and partitioning the gas flow path, the gas flow path includes a pair of first gas flow paths defined by a main separation portion of the separation wall, the partition wall includes a sub-separation portion extending from the main separation portion to an inner surface of the auxiliary partition wall and dividing the first gas flow path in a height direction of the auxiliary partition wall. Battery pack.

2. The battery pack of claim 1 , wherein the auxiliary partition has an open surface coupled to the side wall such that the gas passage is connected to the gas exhaust passage of the side wall.

3. The battery pack according to claim 1 , wherein the auxiliary partition includes an intake hole on a side corresponding to the gas flow passage.

4. The battery pack according to claim 3 , wherein at least one intake hole is formed on a side surface of the auxiliary partition.

5. The pack case further includes a main partition wall extending across a center of the lower plate, The battery pack according to claim 1 , wherein both ends of the auxiliary partition are respectively connected to the main partition and the side wall.

6. The battery pack according to claim 5 , wherein the auxiliary partitions are disposed on the lower plate at predetermined intervals along the main partition.

7. The battery pack according to claim 3 , wherein the first gas flow passage includes a plurality of second gas flow passages formed by being partitioned by sub-separation portions of the partition wall.

8. The battery pack of claim 7 , wherein the suction hole is formed on one side of the auxiliary partition wall so as to be connected to all of the second gas channels.

9. The battery pack according to claim 7 , wherein the second gas flow path is connected to the gas exhaust path of the side wall.

10. 2. The battery pack according to claim 1, wherein the pack case includes an exhaust hole that is open to the outside and allows gas to enter and exit on at least one of a front surface and a rear surface based on an extending direction of the side wall.

11. The battery pack according to claim 10 , wherein the gas discharge path is formed to extend along a longitudinal direction of the side wall and is connected to the exhaust hole.

12. The battery pack according to claim 1 , wherein a cross-sectional area of ​​the gas discharge channel is larger than a cross-sectional area of ​​the gas flow channel.

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