Horizontal heat exchanger

Abstract

A horizontal heat exchanger comprises a horizontal shell pass barrel, the axial direction of the shell pass barrel is recorded as the left-right direction, the upper portion of the shell pass barrel is provided with a shell pass inlet connecting pipe and a shell pass gas phase outlet connecting pipe, and the lower portion of the shell pass barrel is provided with a shell pass liquid phase outlet connecting pipe; the two tube plates are respectively arranged at the two ends of the shell pass cylinder; the two tube boxes are provided with tube pass connecting tubes and are respectively arranged on the corresponding tube plates; the heat exchange core body is provided with a plurality of heat exchange pipes extending in the left-right direction and a jacket arranged on the periphery of the whole heat exchange pipes in a sleeving mode; the at least two heat exchange core bodies are arranged in the upper side space and the lower side space in the shell pass cylinder body, the two ends of the heat exchange tube of each heat exchange core body are supported on the corresponding tube plates respectively and are communicated with the tube boxes on the tube plates, and a plurality of through holes are distributed in a jacket of each heat exchange core body so that a shell pass medium can flow through the through holes. The heat exchanger is suitable for heat exchange with gas and liquid two-phase flow as a shell pass, and temperature crossing of a tube pass medium in a heat exchange tube of a single heat exchange core body is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of heat exchangers, and in particular relates to a horizontal heat exchanger. Background Art

[0002] As a highly efficient and energy-saving heat exchanger, the wound tube heat exchanger usually includes a shell-side cylinder, tube sheets and tube boxes at both ends of the shell-side cylinder, and heat exchange tubes spirally wound in the shell-side cylinder. Both ends of the heat exchange tubes are supported on the corresponding tube sheets and connected to the corresponding tube boxes. During heat exchange, the tube-side medium enters the heat exchange tube through the tube box and exchanges heat with the shell-side medium in the shell-side cylinder.

[0003] For horizontal wound tube heat exchangers, and the shell-side medium is gas-liquid two-phase flow heat exchange (after the shell-side medium heat exchange, part of the shell-side medium will be liquefied, and the liquefied shell-side medium will be in the lower space of the shell-side cylinder, while the upper space of the shell-side cylinder is the unliquefied gas phase medium), since the spirally wound heat exchange tubes are in the upper space and the lower space of the shell-side cylinder at the same time, the tube-side medium forms a temperature cross in the heat exchange tubes, resulting in inaccurate heat transfer calculations. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a horizontal heat exchanger suitable for gas-liquid two-phase heat exchange in the shell side so that the medium in the tube side can obtain the required heat exchange temperature in view of the current status of the prior art.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a horizontal heat exchanger, comprising:

[0006] A horizontal shell-side cylinder, with the axial direction of the shell-side cylinder being the left-right direction, a shell-side inlet pipe and a shell-side gas phase outlet pipe are arranged at the upper part of the shell-side cylinder, and a shell-side liquid phase outlet pipe is arranged at the lower part;

[0007] Two tube sheets are respectively arranged at two ends of the shell-side cylinder;

[0008] Two pipe boxes with pipe-pass nozzles are respectively arranged on the corresponding tube sheets;

[0009] A heat exchange core body, comprising a plurality of heat exchange tubes extending in the left-right direction and a jacket sleeved on the entire outer periphery of the plurality of heat exchange tubes;

[0010] The feature is that: there are at least two heat exchange cores.

[0011] At least two heat exchange cores are arranged in the upper space and the lower space inside the shell-side cylinder. The two ends of the heat exchange tubes of each heat exchange core are respectively supported on their corresponding tube sheets and connected to the tube box on the tube sheet, and a plurality of through holes are distributed on the jacket of each heat exchange core for the circulation of shell-side medium.

[0012] The design of at least two heat exchange cores in the present invention, which are respectively arranged in the upper space and the lower space inside the shell-side cylinder, allows the liquefied part of the shell-side medium to exchange heat with the heat exchange core in the lower space, and the unliquefied shell-side medium to exchange heat with the heat exchange core in the upper space. After heat exchange, the gas phase shell-side medium is output from the shell-side gas phase outlet pipe, and the liquid phase shell-side medium is output from the shell-side liquid phase outlet pipe. At the same time, the tube-side medium entering one of the tube boxes is divided into at least two streams and then enters the heat exchange tubes of the respective heat exchange cores to exchange heat with the shell-side medium. The tube-side medium after heat exchange is mixed in the other tube box to reach the outlet temperature calculated by the process.

[0013] The heat exchange cores may be two, three, four or even more. To improve the heat exchange efficiency, preferably, there are four heat exchange cores, and two heat exchange cores are divided into two groups, one above the other, and the two heat exchange cores in the first group are respectively arranged in the upper space and the lower space inside the shell cylinder, and the two heat exchange cores in the second group are arranged between the two heat exchange cores in the first group, one before the other. In this way, the present invention can effectively utilize the space inside the shell cylinder to ensure the heat exchange effect.

[0014] Preferably, the cross-section of each heat exchange core is circular, and the outer diameter of each heat exchange core in the second group is greater than the outer diameter of each heat exchange core in the first group;

[0015] Or, the cross-section of each heat exchange core in the second group is circular, and the cross-section of each heat exchange core in the first group is elliptical, the area of ​​the ellipse is smaller than the area of ​​the circle, and the major axis of the ellipse extends front to back, and the minor axis of the ellipse extends up and down.

[0016] The cooperation between the elliptical heat exchange core and the circular heat exchange core in the present invention can better utilize the space inside the shell-side cylinder.

[0017] In the above solution, preferably, each tube sheet includes:

[0018] A large tube sheet is arranged at the end of the shell-side cylinder, and the large tube sheet is provided with mounting holes penetrating the thickness of the sheet at positions corresponding to each heat exchange core;

[0019] The number of small tube sheets is the same as that of the heat exchange core, and each small tube sheet is respectively arranged at the corresponding mounting hole to close the mounting hole, and the small tube sheet is used to support the heat exchange tubes in the corresponding heat exchange core.

[0020] At this time, the small tube sheet is part of the heat exchange core. During assembly, the heat exchange core is moved into the shell cylinder, the small tube sheet on the heat exchange core is aligned with the mounting hole on the large tube sheet, and then the two are connected by welding or other means, which is convenient for assembly.

[0021] Preferably, the small tube sheet is embedded in the mounting hole, and the edge of the small tube sheet is welded to the edge of the corresponding mounting hole.

[0022] The above-mentioned solution of embedding and welding has the following difficulties: 1. The tube sheet of the heat exchanger is generally thick, and the welding deformation is large when welding the small tube sheet to the large tube sheet, and the welding difficulty is also large; 2. Due to the thick thickness of the tube sheet, it is difficult to detect the weld after welding.

[0023] In order to overcome the above difficulties, preferably, the small tube sheet is arranged on the inner side of the large tube sheet, and the edge portion of the outer plate surface of the small tube sheet is opposite to the edge of the mounting hole and welded to each other.

[0024] Preferably, the through holes on the jacket of the heat exchange core located in the upper space are arranged at intervals in the circumferential direction, and the through holes arranged at intervals in the circumferential direction form a group, and there are at least two groups arranged at intervals in the left-right direction.

[0025] The through holes can be circular holes, oblong holes, etc. The function of the through holes arranged at intervals in the circumferential direction is to ensure the outflow of the liquefied shell-side medium and the flow of the gas-phase medium.

[0026] Preferably, the through holes on the jacket of the heat exchange core located in the lower space are in a C-shape extending in the circumferential direction, with the C-shaped opening facing upward, and the through holes are arranged at intervals in the left-right direction.

[0027] The functions of the C-shaped through hole are: 1. To ensure the circulation of the liquefied shell-side medium in the heat exchange core in the lower space of the shell-side cylinder; 2. To ensure that the gas phase medium flows upward through the C-shaped through hole and exchanges heat with the heat exchange core on the upper side.

[0028] In the above schemes, preferably, at least two baffles are further included, which are arranged in the shell-side cylinder at intervals along the left-right direction, and each baffle is provided with a through hole for the heat exchange core to pass through, and the jacket located between two adjacent baffles is provided with the above-mentioned through hole. The cooperation between the baffle and the through hole allows the liquefied shell-side medium to flow downward in time and enter the lower space of the shell-side cylinder without affecting the flow of the gas phase medium.

[0029] Furthermore, the number of the through holes is consistent with the number of the heat exchange cores, so that each through hole is used for a corresponding heat exchange core to pass through, and the shape of the through hole is consistent with the cross-sectional shape of the heat exchange core passing through the through hole.

[0030] Furthermore, the edge of the perforation is welded to the jacket of the heat exchange core passing through the perforation, and the periphery of the baffle is fixed relative to the shell-side cylinder, thereby improving the stability of the overall structure.

[0031] In the above schemes, the heat exchange tube can be an existing straight tube structure, or a spirally wound tube structure, or a combination of the two. Preferably, the heat exchange tube has straight tube sections extending left and right at both ends, and a spirally wound spiral section located between the two straight tube sections, and the jacket is sleeved on the outer periphery of the spiral section; at least one of the straight tube sections is sleeved on the outer periphery with a guide tube, and a plurality of guide holes are distributed on the tube wall of the guide tube. Preferably, the guide tube is arranged corresponding to the shell side inlet side to achieve uniform distribution of the shell side medium.

[0032] Compared with the prior art, the advantages of the present invention are as follows: the design of at least two heat exchange cores in the present invention, which are respectively arranged in the upper space and the lower space inside the shell-side cylinder, enables the liquefied part of the shell-side medium to exchange heat with the heat exchange core in the lower space, and the unliquefied shell-side medium to exchange heat with the heat exchange core in the upper space. The gas phase shell-side medium after heat exchange is output from the shell-side gas phase outlet pipe, and the liquid phase shell-side medium is output from the shell-side liquid phase outlet pipe. At the same time, the tube-side medium entering one of the tube boxes is divided into at least two streams and then enters the heat exchange tubes of the respective heat exchange cores to exchange heat with the shell-side medium. The tube-side medium after heat exchange is mixed in another tube box to reach the outlet temperature calculated by the process, that is, the tube-side medium with the required temperature can be obtained at the outlet, thereby meeting the needs of the heat exchange process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a longitudinal cross-sectional view of the first embodiment of the present invention;

[0034] Figure 2 for Figure 1 Transverse section view at AA;

[0035] Figure 3 is a transverse cross-sectional view of a baffle according to Embodiment 1 of the present invention;

[0036] Figure 4 for Figure 1 Enlarged view of the middle part I;

[0037] Figure 5 for Figure 1 Another enlarged view of the middle part I;

[0038] Figure 6 It is a longitudinal cross-sectional view of a single heat exchange core in the first embodiment of the present invention;

[0039] Figure 7 for Figure 6 Transverse section view at the middle BB;

[0040] Figure 8 It is a longitudinal cross-sectional view of the second embodiment of the present invention;

[0041] Fig. 9is a transverse cross-sectional view of the baffle in the third embodiment of the present invention;

[0042] Fig.10 It is a transverse cross-sectional view of the heat exchanger in the third embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the accompanying drawings.

[0044] Embodiment 1:

[0045] like Figures 1 to 7 As shown, a preferred embodiment 1 of a horizontal heat exchanger of the present invention is shown, and the horizontal heat exchanger includes a shell-side cylinder 1, a tube sheet 2, a tube box 3, a heat exchange core 4 and a baffle 5.

[0046] The shell-side cylinder 1 is arranged horizontally, and its axial direction is left and right. A shell-side inlet pipe 11 is provided at the upper left part of the shell-side cylinder 1, a shell-side gas phase outlet pipe 12 is provided at the upper right part, a shell-side liquid phase outlet pipe 13 is provided at the lower right part, and a shell-side inlet drain port 14 is provided at the lower left part.

[0047] There are two tube sheets 2, which are respectively arranged at the left and right ends of the shell-side cylinder 1. There are also two tube boxes 3, which are respectively arranged on the corresponding tube sheets 2. Each tube box 3 is provided with a tube-side pipe 31 for the tube-side medium to pass through. And each tube box 3 is provided with a vent 32 at the top and a drainage outlet 33 at the bottom.

[0048] The heat exchange core 4 has a plurality of heat exchange tubes 41 extending in the left-right direction. In the present embodiment, the heat exchange tubes 41 are of a winding tube structure, having a straight tube section 411 extending in the left-right direction at the left and right ends, and a spiral section 412 spirally wound between the two straight tube sections 411. The heat exchange core 4 also has a jacket 42 sleeved on the entire outer periphery of the spiral section 412 of the plurality of heat exchange tubes 41, and a guide tube 6 sleeved on the entire outer periphery of the left straight tube section 411 of the plurality of heat exchange tubes 41. The jacket 42 is provided with a plurality of through holes 420 for the circulation of shell-side media, and the wall of the guide tube 6 is provided with a plurality of guide holes 60 for the circulation of shell-side media. In the present embodiment, a plurality of guide holes 60 spaced apart in the circumferential direction are grouped together, and there are a plurality of groups spaced apart in the left-right direction, and the guide holes 60 of two adjacent groups are staggered in the left-right direction. For details, please refer to Figure 6 The design of the guide tube 6 can ensure that the fluid entering a single heat exchange core does not flow in a biased manner, thereby affecting the heat transfer calculation.

[0049] In this embodiment, there are four heat exchange cores 4, and they are divided into two groups, two by two. The two heat exchange cores in the first group 4a are arranged in the upper space and the lower space inside the shell cylinder 1, respectively, and the two heat exchange cores in the second group 4b are arranged between the two heat exchange cores 4 in the first group 4a, one in front and one in the back. Figure 2As shown, the cross-section of each heat exchange core 4 in this embodiment is circular, and the outer diameter of each heat exchange core 4 in the second group 4b is larger than the outer diameter of each heat exchange core 4 in the first group 4a. The left and right ends of the heat exchange tube 41 of each heat exchange core 4 are respectively supported on the corresponding tube sheet 2 and communicated with the tube box 3 on the tube sheet 2. In this embodiment, Figure 1 , 6 As shown, each tube sheet 2 includes a large tube sheet 21 and four small tube sheets 22. The large tube sheet 21 is arranged at the end of the shell-side cylinder 1, and the large tube sheet 21 is provided with mounting holes 210 (that is, there are also four mounting holes 210) penetrating the plate thickness at positions corresponding to each heat exchange core 4; each small tube sheet 22 is respectively arranged at the corresponding mounting hole 210 to close the mounting hole 210, and the small tube sheet 22 is supported by the heat exchange tube 41 in the corresponding heat exchange core 4. Specifically, the small tube sheet 22 is arranged on the inner side of the large tube sheet 21, and the edge of the outer plate surface of the small tube sheet 22 is opposite to the edge of the corresponding mounting hole 210 and welded to each other, so that the large tube sheet 21 and the small tube sheet 22 are arranged one outside and one inside.

[0050] At the same time, if Figure 1 , 6 As shown in Figures 7 and 8, the through holes 420 on the jacket 42 of the two heat exchange cores in the second group 4b and the heat exchange core in the upper space in the first group 4a are arranged at intervals in the circumferential direction, and the through holes 420 arranged at intervals in the circumferential direction form a group, and there are multiple groups arranged at intervals in the left-right direction; the through holes 420 on the jacket 42 of the heat exchange core 4 located in the lower space are in a C-shape extending in the circumferential direction, and the C-shaped opening faces upward, and the through holes 420 are arranged at intervals in the left-right direction.

[0051] There are a plurality of baffles 5, which are arranged in the shell-side cylinder 1 at intervals along the left-right direction, and each baffle 5 is provided with a through hole 50 for each heat exchange core 4 to pass through. The number of the through holes 50 is consistent with the number of the heat exchange core 4, so that each through hole 50 is for each corresponding heat exchange core 4 to pass through, and the shape of the through hole 50 is consistent with the cross-sectional shape of the heat exchange core 4 passing through the through hole 50. For details, please refer to Figure 3 The edge of the through hole 50 is welded to the jacket 42 of the heat exchange core 4 passing through the through hole 50, and the periphery of the baffle 5 is fixed relative to the shell-side cylinder 1. The jacket 42 located between two adjacent baffles 5 is provided with the above-mentioned through hole 420 to ensure the shell-side medium flow between the two adjacent baffles 5.

[0052] In this embodiment, the outer peripheral sleeve of the whole formed by the four heat exchange cores 4 is provided with an outer jacket 7, and the periphery of each baffle 5 is constrained together with the outer jacket 7. Specifically, Figure 4As shown, the inner wall surface of the outer jacket 7 is provided with an elastic sealing sheet 71 extending inwardly, and the plate surface of the baffle 5 close to the peripheral portion is in contact with one side surface of the elastic sealing sheet 71, and the two are connected by fasteners 72 such as screws; it can also be as shown Figure 5 As shown, the peripheral portion of the baffle plate 5 is inserted into the corresponding insertion hole 73 on the outer jacket 7, and the two are connected by welding.

[0053] When the heat exchanger is working, the shell-side medium enters the shell-side cylinder 1 through the shell-side inlet pipe 11, and the tube-side medium enters the heat exchange tubes 41 of each heat exchange core 4 through the pipe box 3 on the left side of the heat exchanger and exchanges heat with the shell-side medium. The liquefied part of the shell-side medium flows downward and exchanges heat with the heat exchange core in the lower space, and the unliquefied shell-side medium exchanges heat with the heat exchange core in the upper space and the heat exchange core in the second group 4b. After heat exchange, the gas phase shell-side medium is output from the shell-side gas phase outlet pipe 12, and the liquid phase shell-side medium is output from the shell-side liquid phase outlet pipe 13. At the same time, the tube-side medium after heat exchange is mixed in the pipe box 3 on the right side of the heat exchanger to reach the outlet temperature calculated by the process.

[0054] Embodiment 2:

[0055] like Figure 8 As shown, a preferred embodiment 2 of a horizontal heat exchanger of the present invention is shown. This embodiment is basically the same as the embodiment 1, except that in this embodiment, the small tube sheet 22 is embedded in the corresponding mounting hole 210, and the edge of the small tube sheet 22 is welded to the edge of the corresponding mounting hole 210 so that the large tube sheet 22 and the small tube sheet 22 as a whole form a vertically arranged plate-like body.

[0056] Embodiment three:

[0057] like Fig. 9 , 10 As shown, it is a preferred embodiment 3 of a horizontal heat exchanger of the present invention. This embodiment is basically the same as the embodiment 1, except that in this embodiment, the cross-section of each heat exchange core 4 in the second group 4b is circular, and the cross-section of each heat exchange core 4 in the first group 4a is elliptical, the area of ​​the ellipse is smaller than the area of ​​the circle, and the major axis of the ellipse extends forward and backward, and the minor axis of the ellipse extends up and down, so as to better utilize the space inside the shell cylinder. In this embodiment, as in the prior art, the heat exchange tube is spirally wound from the inside to the outside to form a multi-layer spiral tube, and a heat exchange core with a circular or elliptical cross-section can be wound by controlling the spacing between the inner and outer adjacent layers of the spiral tube.

[0058] In the specification and claims of the present invention, terms indicating directions, such as "front", "rear", "up", "down", "left", "right", "side", "top", "bottom", etc., are used to describe various exemplary structural parts and elements of the present invention, but these terms are used here only for the purpose of convenience of description and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in the present invention can be arranged in different directions, these terms indicating directions are only used as explanations and should not be regarded as limitations. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0059] The term "vertical" is also used in the specification and claims of the present invention, which means basically along the up and down direction, and is not limited to the vertical direction only, and can also be slightly inclined relative to the vertical direction.

Claims

1. A horizontal heat exchanger, comprising: A horizontal shell-side cylinder (1), wherein the axial direction of the shell-side cylinder (1) is the left-right direction, the upper part of the shell-side cylinder (1) is provided with a shell-side inlet pipe (11) and a shell-side gas phase outlet pipe (12), and the lower part is provided with a shell-side liquid phase outlet pipe (13); Two tube sheets (2) are respectively arranged at two ends of the shell-side cylinder (1); Two tube boxes (3) with tube-side connecting pipes are respectively arranged on the corresponding tube sheets (2); The heat exchange core (4) comprises a plurality of heat exchange tubes (41) extending in the left-right direction and a jacket (42) sleeved on the entire outer periphery of the plurality of heat exchange tubes (41); Features: The heat exchange core (4) has at least two parts. At least two heat exchange cores (4) are arranged in the upper space and the lower space inside the shell-side cylinder (1), and the two ends of the heat exchange tube (41) of each heat exchange core (4) are respectively supported on the corresponding tube sheet (2) and connected to the tube box (3) on the tube sheet (2), and a plurality of through holes (420) are distributed on the jacket (42) of each heat exchange core (4) to allow the shell-side medium to flow.

2. The horizontal heat exchanger according to claim 1, characterized in that: There are four heat exchange cores (4), which are divided into two groups of two. The two heat exchange cores in the first group (4a) are arranged one above and one below in the upper space and the lower space inside the shell cylinder (1), respectively. The two heat exchange cores in the second group (4b) are arranged one before and one after between the two heat exchange cores (4) in the first group (4a).

3. The horizontal heat exchanger according to claim 2, characterized in that: The cross-section of each heat exchange core (4) is circular, and the outer diameter of each heat exchange core (4) in the second group (4b) is greater than the outer diameter of each heat exchange core (4) in the first group (4a); Alternatively, the cross-section of each heat exchange core (4) in the second group (4b) is circular, and the cross-section of each heat exchange core (4) in the first group (4a) is elliptical, the area of ​​the ellipse is smaller than the area of ​​the circle, and the major axis of the ellipse extends forward and backward, and the minor axis of the ellipse extends upward and downward.

4. The horizontal heat exchanger according to claim 1, characterized in that: Each tube sheet (2) comprises: A large tube sheet (21) is arranged at the end of the shell-side cylinder (1), and mounting holes (210) penetrating the thickness of the tube sheet are arranged at positions corresponding to each heat exchange core (4) on the large tube sheet (21); The number of small tube sheets (22) is the same as that of the heat exchange core (4), and each small tube sheet (22) is respectively arranged at a corresponding mounting hole (210) to close the mounting hole (210), and the small tube sheet (22) is supported by the heat exchange tube (41) in the corresponding heat exchange core (4).

5. The horizontal heat exchanger according to claim 4, characterized in that: The small tube sheet (22) is embedded in the mounting hole (210), and the edge of the small tube sheet (22) is welded to the edge of the corresponding mounting hole (210); or, the small tube sheet (22) is arranged on the inner side of the large tube sheet (21), and the edge portion of the outer plate surface of the small tube sheet (22) is opposite to the edge of the mounting hole (210) and is welded to each other.

6. The horizontal heat exchanger according to claim 1, characterized in that: The through holes (420) on the jacket (42) of the heat exchange core (4) located in the upper space are arranged at intervals in the circumferential direction, and the through holes (420) arranged at intervals in the circumferential direction form a group, and there are at least two groups arranged at intervals in the left-right direction; the through holes (420) on the jacket (42) of the heat exchange core (4) located in the lower space are C-shaped extending in the circumferential direction, and the C-shaped opening faces upward, and the through holes (420) are arranged at intervals in the left-right direction.

7. The horizontal heat exchanger according to any one of claims 1 to 6, characterized in that: It also includes at least two baffles (5) which are arranged in the shell-side cylinder (1) at intervals along the left-right direction, and each baffle (5) is provided with a through hole (50) for the heat exchange core (4) to pass through, and the jacket (42) located between two adjacent baffles (5) is provided with the above-mentioned through hole (420).

8. The horizontal heat exchanger according to claim 7, characterized in that: The number of the through holes (50) is consistent with the number of the heat exchange core (4), so that each through hole (50) is used for a corresponding heat exchange core (4) to pass through, and the shape of the through hole (50) is consistent with the cross-sectional shape of the heat exchange core (4) passing through the through hole (50).

9. The horizontal heat exchanger according to claim 8, characterized in that: The edge of the through hole (50) is welded to the jacket (42) of the heat exchange core (4) passing through the through hole (50), and the periphery of the baffle (5) is fixed relative to the shell-side cylinder (1).

10. The horizontal heat exchanger according to any one of claims 1 to 6, characterized in that: The heat exchange tube (41) comprises straight tube sections (411) extending left and right at two ends, and a spiral section (412) spirally wound between the two straight tube sections (411); the jacket (42) is sleeved on the outer circumference of the spiral section (412); a flow guide tube (6) is sleeved on the outer circumference of at least one of the straight tube sections (411), and a plurality of flow guide holes (60) are distributed on the tube wall of the flow guide tube (6).

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