Novel water cooling screen for single crystal furnace

Abstract

The utility model provides a novel water-cooling screen for a single crystal furnace, and aims to solve the technical problems that the bottom end and the side wall near the bottom end of the conventional water-cooling screen are easy to accumulate and adsorb precipitates to influence water circulation, and the welding part of a water-cooling screen hanging wall and a furnace cover is easy to break during abnormal bearing. The outer cylinder is arranged outside the inner cylinder in a sleeving mode, a containing space is reserved between the outer cylinder and the inner cylinder, and the bottom of the outer cylinder is sealed. The flow guide unit is provided with a partition plate assembly and a plurality of flow baffles. The partition plate assembly is installed in the containing space in a matched mode so that the containing space can be divided into a plurality of water channels communicated from top to bottom. The flow baffles are installed on the outer wall of the inner cylinder at the bottom end water channel, and the distance between the top end of each flow baffle and the adjacent partition plate is smaller than the distance between the bottom end of each flow baffle and the bottom end of the outer cylinder. Circulating water entering the containing space is drained to the bottom end of the water channel from the top end of the water channel and is converted into turbulent flow under the action of the flow baffles, meanwhile, flow velocity difference is formed, and therefore upward lifting force is generated to maintain particulate matter in water to suspend and flow along with water flow, and sedimentation is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of single crystal material production, and in particular to a new type of water-cooled screen for single crystal furnaces. Background Art

[0002] A single crystal furnace is a device that first melts polycrystalline materials such as polysilicon in an inert gas atmosphere using a graphite heater, then uses the Czochralski method to pull a single crystal ingot upward. During the upward growth of the single crystal ingot, the latent heat of crystallization generated by phase transitions can disrupt the ideal equilibrium between the melt and the crystallization surface within the crucible. Therefore, a water-cooled screen is connected to the furnace lid to dissipate this latent heat through circulating water, allowing the single crystal ingot to reach its ideal crystallization state.

[0003] Currently, there are two methods for circulating water into water-cooled panels: one uses water cooled through a closed cooling tower, and the other uses water cooled through an open cooling system using air as a cooling medium. The costs of these two methods differ significantly, and some photovoltaic companies choose the lower-cost second method for providing cooling water. However, despite the inclusion of additional treatment measures for the circulating water in the second method, such as bypass filtration to remove suspended matter and the addition of biocides to inhibit microbial growth, small amounts of impurities (such as inorganic minerals, clay, organic particles, and biodetritus) can still enter the water-cooled panels through the bottom water channel before being discharged.

[0004] Due to the low flow rate in the bottom channel, the fluid forms a laminar flow state, with stratified flow and no mixing. Furthermore, the impurities mentioned above have a loose structure, large surface area, and colloidal properties. Therefore, under the action of gravity, these impurities are easily deposited and adsorbed by the metal wall. Over time, a large amount of dispersed suspended matter and floating debris accumulates in the bottom channel, forming a viscous fluid (such as a mudslide or rock flow). To reduce sediment accumulation at the bottom of the water-cooling plate and its adjacent sidewalls, common practices include increasing the purity of the circulating water to reduce particulate matter from the water column and increasing the water flow rate to carry more sediment out of the water-cooling plate. However, these practices place high demands on the quality and quantity of the circulating water, increase costs, and hinder the implementation and development of green process concepts.

[0005] Furthermore, the water-cooling screen is typically connected to the single crystal furnace roof using hanging arms. However, since the connections between the wall tubes are simply welded, and the tensile strength of the welds is limited, during the actual single crystal pulling process, when the water-cooling screen experiences abnormal loads, the welds can deform and break, causing damage and leakage to the screen, affecting its normal operation. Replacing or repairing the screen is time-consuming and labor-intensive. Utility Model Content

[0006] The utility model provides a novel water-cooling screen for a single crystal furnace to solve the problems raised in the above background technology.

[0007] A new type of water cooling screen for single crystal furnace, comprising:

[0008] The outer cylinder is sleeved outside the inner cylinder and a storage space is left between the outer cylinder and the inner cylinder. The bottom of the outer cylinder is sealed. The flow guide unit has a partition assembly and multiple baffles.

[0009] The partition assembly is matched and installed in the accommodation space to divide the accommodation space into a plurality of water channels interconnected from top to bottom;

[0010] The baffle is installed on the outer wall of the inner tube at the bottom waterway; the distance between the top of each baffle and its adjacent partition is smaller than the distance between the bottom of the baffle and the bottom of the outer tube;

[0011] The circulating water entering the accommodation space is first led from the top of the water channel to the bottom of the water channel, and after being disturbed by the baffle, is discharged from the water cooling screen along the water channel from bottom to top.

[0012] Furthermore, each baffle has an overall structure that gradually transitions from an arc-shaped head to a narrow tail, and the top of the baffle adopts a streamlined curved surface structure.

[0013] Furthermore, three baffles are provided, and the three baffles are evenly spaced and connected to the outer wall of the inner cylinder along the circumference of the inner cylinder.

[0014] Furthermore, the water channel includes a plurality of annular water channels and a drainage water channel;

[0015] A plurality of annular water channels are arranged on the outer wall of the inner cylinder from top to bottom;

[0016] The drainage water channel runs through multiple annular water channels from top to bottom and finally leads to the bottom annular water channel; starting from the bottom annular water channel and going from bottom to top, the outflow end of each annular water channel is connected to the inflow end of its adjacent annular water channel, and the outflow end of the top annular water channel is connected to the outside of the accommodation space.

[0017] Furthermore, the top end of the inner cylinder is sealed;

[0018] The new single crystal furnace water cooling screen also includes a wall-mounted tube group, which is installed through the top of the inner tube and includes a water inlet pipe and a water outlet pipe; the water outlet end of the water inlet pipe leads to the drainage waterway, and the water inlet end of the water outlet pipe is connected to the top annular waterway.

[0019] Furthermore, each arm tube includes a vertical short tube, a horizontal tube, a vertical long tube and two connecting tubes; the two ends of the horizontal tube are respectively threadedly connected to a connecting tube; the bottom end of the connecting tube at one end of the horizontal tube is threadedly connected to one end of the vertical short tube; the other end of the vertical short tube is welded to the water inlet or outlet; the top end of the connecting tube at the other end of the horizontal tube is threadedly connected to the vertical long tube, so that the vertical long tube is arranged perpendicular to the horizontal tube.

[0020] Furthermore, each threaded connection between the horizontal tube, one end of the vertical short tube, the bottom end of the vertical long tube and the connecting tube can be welded.

[0021] Furthermore, the inner cylinder is provided with a water inlet and a water outlet, wherein the water inlet is arranged on the side wall of the inner cylinder at the drainage waterway, and the water outlet is arranged on the side wall of the inner cylinder at the top annular channel; the water inlet and the water outlet are respectively arranged on the inner cylinder near the top end with the inner cylinder axis as the axis of symmetry.

[0022] Furthermore, the water outlet end of the water inlet pipe is matched with the water inlet after being beveled, welded to the water inlet and leads to the drainage waterway, and the water inlet end of the water outlet pipe is matched with the water outlet after being beveled, welded to the water outlet and communicates with the top annular waterway.

[0023] Furthermore, among the multiple annular water channels, a baffle can be matched and provided in any annular water channel except the bottom annular water channel.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) By adding a baffle to the bottom annular pipe, and the upper branch water channel formed by the top of the baffle and its adjacent partition is narrower than the lower branch water channel formed by the bottom of the baffle and the bottom of the water cooling screen, it can disrupt the flow state of the water flow at the bottom of the water cooling screen and generate an upward lifting force on the particulate matter contained in the circulating water, thereby reducing the deposition of impurities in the bottom water channel and its nearby side walls due to gravity, and maintaining the smooth water circulation of the water cooling screen.

[0026] (2) The baffle has a streamlined top surface and a relatively flat bottom surface. The side surface can be installed in contact with the outer wall of the inner tube. This is not only conducive to the firmness of the installation, but also improves the fluidity of the water flow by converting the water flow into turbulent flow without affecting the heat dissipation of the water cooling screen.

[0027] (3) By first threading and positioning the connections between the horizontal tube, one end of the vertical short tube, the bottom end of the vertical long tube and the connecting tube, and then assembling the wall-mounted tube by seamless welding, not only the load-bearing capacity is enhanced, but also the probability of damage to the water-cooling screen and the major safety risks caused by abnormal load can be effectively reduced, saving the cost of replacing or repairing the water-cooling screen. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 This is a schematic diagram of the assembly structure of the inner cylinder and the guide unit of a new type of water-cooling panel for a single crystal furnace according to an embodiment of the present application;

[0030] Figure 2 This is a front view of an inner cylinder equipped with a guide unit of a new type of water-cooling panel for a single crystal furnace according to an embodiment of the present application;

[0031] Figure 3 This is a bottom view of an inner cylinder equipped with a guide unit of a new type of water-cooling panel for a single crystal furnace according to an embodiment of the present application;

[0032] Figure 4 A top view of a baffle of a new type of water-cooled screen for a single crystal furnace according to an embodiment of the present application;

[0033] Figure 5 This is a schematic structural diagram of a new type of water-cooling screen for a single crystal furnace according to an embodiment of the present application;

[0034] Figure 6 This is a front view of a new type of water cooling screen for a single crystal furnace according to an embodiment of the present application;

[0035] Figure 7 This is a schematic cross-sectional view of portion A of a water-cooling shield used in a novel single crystal furnace according to an embodiment of the present application.

[0036] Reference numerals:

[0037] 1. Outer cylinder; 2. Inner cylinder; 21a. Water inlet; 21b. Water outlet;

[0038] 30. Baffle assembly; 31. Baffle; 31a. Top of baffle; 31b. Head of baffle; 31c. Tail of baffle; 33. Diversion channel; 34. Annular channel; 34a. Bottom annular channel; 34b. Top annular channel; 35a. Upper branch channel; 35b. Lower branch channel.

[0039] 50. Cover; 51. Wall-mounted tube; 510. Vertical long tube; 511. Horizontal tube; 512. Vertical short tube; 513. Connecting tube;

[0040] A. The connecting pipe parts where the other end of the horizontal pipe and the vertical pipe are respectively equipped. DETAILED DESCRIPTION

[0041] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0042] In the description of the present invention, it should be understood that the terms "upper", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0043] In this utility model, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0044] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0045] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but a person of ordinary skill in the art will recognize the application of other processes and / or the use of other materials.

[0046] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] The utility model embodiment provides a new type of single crystal furnace water cooling screen, please refer to Figure 1-Figure 7 The new single crystal furnace water cooling panel includes an inner tube 2, an outer tube 1, a flow guide unit and a wall tube group.

[0048] Specifically,

[0049] The outer cylinder 1 is a hollow frustum structure with a sealed bottom and an open top. The frustum structure is wide at the top and narrow at the bottom.

[0050] The inner cylinder 2 is matingly connected to the inner bottom end of the outer cylinder 1. That is, the inner cylinder 2 can also be a frustoconical structure with a wide top and a narrow bottom. A storage space for circulating water is left between the inner cylinder 2 and the outer cylinder 1. The inner cylinder 2 is provided with a water inlet 21a and a water outlet 21b. The circulating water flows into the storage space through the water inlet 21a and then out through the water outlet 21b. Preferably, the water inlet 21a and the water outlet 21b are located on the sidewall of the inner cylinder 2 near its top, symmetrically with the axis of the inner cylinder 2. The top of the inner cylinder is sealed.

[0051] The diversion unit includes a baffle assembly 30 and a baffle 31. The baffle assembly 30 is arranged in the storage space and connected to the outer wall of the inner tube 2. The baffle assembly 30 divides the storage space into multiple water channels that are interconnected from top to bottom, so that the circulating water flowing into the storage space from the water inlet 21a is first diverted to the bottom water channel through the water channel, and then diverted to the water outlet 21b for discharge. The baffle 31 is connected to the outer wall of the inner tube 2 and arranged in the bottom water channel, so that the distance between the top of the baffle and its adjacent baffle is smaller than the distance between the bottom of the baffle and the bottom of the outer tube. The baffle 31 converts the flow state of the circulating water leading to the bottom water channel into turbulent flow while forming a flow velocity difference, thereby generating an upward lifting force that can keep the particles in the water suspended and flow with the water flow, reducing sedimentation.

[0052] The partition assembly 30 separates the storage space into multiple annular water channels 34 and a drainage channel 33. The multiple annular water channels 34 are arranged from top to bottom on the outer wall of the inner tube 2. The drainage channel 33 surrounds the water inlet 21a and extends from top to bottom through the multiple annular water channels 34, ultimately leading to the bottom annular water channel 34a. This allows circulating water entering the storage space from the water inlet 21a to be quickly diverted to the bottom annular water channel 34a. Starting from the bottom annular water channel 34a, the outflow end of each annular water channel 34 communicates with the inflow end of its adjacent annular water channel 34, and the outflow end of the top annular water channel 34b communicates with the water outlet 21b. This allows the circulating water that has entered the bottom annular water channel 34a to flow toward the top of the inner tube 2 and be discharged at the water outlet 21b.

[0053] Multiple baffles 31 are provided, arranged circumferentially within the bottom annular water channel 34a of the inner tube 2. These baffles 31 can be welded to the outer wall of the inner tube 2, ensuring a tight fit. When circulating water flowing into the bottom annular water channel 34a passes through the baffles 31, the water flows in a turbulent state. Furthermore, the upper branch water channel 35a formed by the top of each baffle 31a and its adjacent partition is narrower than the lower branch water channel 35b formed by the bottom of the baffle and the bottom of the water-cooling screen. Consequently, the flow velocity above the baffle increases, while the flow velocity below the baffle slows down. According to Bernoulli's principle, under constant-height flow conditions, an increase in flow velocity leads to a decrease in pressure. Therefore, water flowing through the baffles 31 creates a pressure gradient, which exerts an upward force on particulate matter contained in the circulating water, helping to keep the particulate matter suspended in the water and maintaining smooth water circulation in the water-cooling screen.

[0054] To further enhance the fluidity of water within the bottom annular water channel 34a, each baffle 31 has an overall structure with a curved head 31b that gradually transitions to a narrower tail 31c. Furthermore, the baffle's top 31a features a streamlined curved surface, resulting in a gradually widening of the upper branch water channel 35a while maintaining a uniform width of the lower branch water channel 35b. Preferably, three baffles 31 are used, evenly spaced along the circumference of the inner tube 2 and attached to the outer wall of the inner tube 2.

[0055] When the circulating water from the diversion waterway 33 to the bottom annular waterway 34a flows through the baffle 31 and is diverted to the upward branch waterway 35a and the lower branch waterway 35b, the water flow state can be converted into turbulent flow, and an upward thrust is generated on the particulate matter contained in the circulating water, thereby preventing the particulate matter from being adsorbed in the waterway or deposited at the bottom of the water-cooling screen under the action of gravity.

[0056] The wall-mounted pipe assembly, installed throughout the top of the inner tube, includes two wall-mounted pipes, one for water inlet and one for water outlet. The outlet end of the inlet pipe is welded to the water inlet 21a and then leads to the drainage channel 33. The oblique cross-section of the inlet pipe's outlet end is the same as the shape of the water inlet 21a. The inlet end of the outlet pipe is welded to the water outlet 21b and then communicates with the top annular water channel 34b. The oblique cross-section of the outlet pipe's inlet end is the same as the shape of the water outlet 21b.

[0057] Each arm tube 51 includes a short vertical tube 512, a horizontal tube 511, a long vertical tube 510, and two connecting tubes 513. A connecting tube 513 is threadedly connected to each end of the horizontal tube 511. The bottom end of the connecting tube 513, located at one end of the horizontal tube 511, is threadedly connected to one end of the short vertical tube 512, and the other end of the short vertical tube 512 is welded to the water inlet 21a or the water outlet 21b. The top end of the connecting tube 513, located at the other end of the horizontal tube 511, is threadedly connected to the long vertical tube 510, so that the long vertical tube 510 is perpendicular to the horizontal tube 511. The threaded connections between the horizontal tube 511, one end of the short vertical tube 512, the bottom end of the long vertical tube 510, and the connecting tube 513 can be seamlessly welded. This can be achieved by inserting the melted welding rod and base metal into the thread undercut. Since the welding depth and weld width are increased compared to the original single welding, the tensile strength of the weld is also enhanced. Even if abnormal load occurs, the arm tube 51 will reduce the probability of damage due to its excellent resistance to deformation and fracture, which is beneficial to reducing the major safety risks and costs caused by cracking of the water-cooling screen.

[0058] Based on the above embodiments, the working principle of this application is as follows:

[0059] After circulating water enters the storage space through a wall-mounted pipe 51, it is directed to the bottom annular channel 34a in coordination with the diversion channel 33. The circulating water flowing in the bottom annular channel 34a flows through the baffle 31 and is divided into the upward branch channel 35a and the downward branch channel 35b. This creates a pressure gradient in the circulating water passing through the baffle 31, which lifts particulate matter contained in the circulating water upward. This allows these particulate matter, stirred by the water flow, to pass through the annular channels 34 from bottom to top before being discharged through the water outlet 21b.

[0060] Based on the above embodiments, the advantages of this application are:

[0061] (1) By adding a baffle 31 to the bottom annular pipe 34a, and the upper branch water channel 35a formed by the top end 31a of the baffle and its adjacent partition is narrower than the lower branch water channel 35b formed by the bottom end of the baffle and the bottom end of the water-cooling screen, it can disrupt the flow of water at the bottom end of the water-cooling screen and generate an upward lifting force on the particulate matter contained in the circulating water, thereby reducing the deposition and adsorption of particulate matter on the bottom water channel and its nearby side walls due to gravity, thereby maintaining the smooth water circulation of the water-cooling screen.

[0062] (2) The baffle 31 has a streamlined top surface and a relatively flat bottom surface, and the side surface can be installed in contact with the outer wall of the inner tube. This not only facilitates the firmness of the installation, but also improves the fluidity of the water flow without affecting the heat dissipation of the water-cooled screen.

[0063] (3) The connections between the horizontal tube 511, one end of the vertical short tube 512, the bottom end of the vertical long tube 510 and the connecting tube 513 are first positioned and installed by threaded connection, and then assembled into the wall-mounted tube 51 by seamless welding. This not only enhances the load-bearing capacity, but also effectively reduces the probability of damage to the water-cooling screen during abnormal load and the major safety risks it brings, thereby saving the cost of replacing or repairing the water-cooling screen.

Claims

1. A new type of water cooling screen for single crystal furnace, characterized by: The new single crystal furnace water cooling screen includes: The outer cylinder is sleeved outside the inner cylinder and a storage space is left between the outer cylinder and the inner cylinder. The bottom of the outer cylinder is sealed. The flow guide unit has a partition assembly and multiple baffles. The partition assembly is matched and installed in the accommodation space to divide the accommodation space into a plurality of water channels interconnected from top to bottom; The baffle is installed on the outer wall of the inner tube at the bottom waterway; the distance between the top of each baffle and its adjacent partition is smaller than the distance between the bottom of the baffle and the bottom of the outer tube; The circulating water entering the accommodation space is first led from the top of the water channel to the bottom of the water channel, and after being disturbed by the baffle, is discharged from the water cooling screen along the water channel from bottom to top.

2. The novel water-cooling screen for single crystal furnace according to claim 1 is characterized in that: Each baffle is in the form of a structure that gradually transitions from an arc-shaped head to a narrow tail, and the top of the baffle adopts a streamlined curved surface structure.

3. The novel water-cooling shield for single crystal furnace according to claim 1 is characterized in that: There are three baffles, which are evenly spaced and connected to the outer wall of the inner cylinder along the circumference of the inner cylinder.

4. The novel water-cooling shield for a single crystal furnace according to any one of claims 1 to 3, characterized in that: The water channel includes a plurality of annular water channels and a diversion water channel; A plurality of annular water channels are arranged on the outer wall of the inner cylinder from top to bottom; The drainage water channel runs through multiple annular water channels from top to bottom and finally leads to the bottom annular water channel; starting from the bottom annular water channel and going from bottom to top, the outflow end of each annular water channel is connected to the inflow end of its adjacent annular water channel, and the outflow end of the top annular water channel is connected to the outside of the accommodation space.

5. The novel water-cooling shield for single crystal furnace according to claim 4 is characterized in that: The top end of the inner cylinder is sealed; The new single crystal furnace water cooling screen also includes a wall-mounted tube group, which is installed through the top of the inner tube and includes a water inlet pipe and a water outlet pipe; the water outlet end of the water inlet pipe leads to the drainage waterway, and the water inlet end of the water outlet pipe is connected to the top annular waterway.

6. The novel water-cooling shield for single crystal furnace according to claim 5 is characterized in that: Each arm tube includes a short vertical tube, a horizontal tube, a long vertical tube and two connecting tubes; the two ends of the horizontal tube are respectively threadedly connected to a connecting tube; the bottom end of the connecting tube provided at one end of the horizontal tube is threadedly connected to one end of the short vertical tube; the other end of the short vertical tube is welded to the water inlet or outlet; The top end of the connecting pipe arranged at the other end of the horizontal pipe is threadedly connected with a vertical long pipe, so that the vertical long pipe is arranged perpendicular to the horizontal pipe.

7. The novel water-cooling shield for single crystal furnace according to claim 6 is characterized in that: The threaded connections between the horizontal pipe, one end of the vertical short pipe, the bottom end of the vertical long pipe and the connecting pipe can be welded again.

8. The novel water-cooling shield for single crystal furnace according to claim 5 is characterized in that: The inner cylinder is provided with a water inlet and a water outlet, wherein the water inlet is arranged on the side wall of the inner cylinder at the drainage waterway, and the water outlet is arranged on the side wall of the inner cylinder at the top annular channel; the water inlet and the water outlet are respectively arranged on the inner cylinder near the top end with the inner cylinder axis as the axis of symmetry.

9. The novel water-cooling shield for single crystal furnace according to claim 8 is characterized in that: The water outlet end of the water inlet pipe is matched with the water inlet after being beveled, welded at the water inlet and leads to the drainage waterway. The water inlet end of the water outlet pipe is matched with the water outlet after being beveled, welded at the water outlet and communicates with the top annular waterway.

10. The novel water cooling shield for single crystal furnace according to claim 4 is characterized in that: At the plurality of annular water channels, a baffle may be matched and provided in any annular water channel except the bottom annular water channel.

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