A heat exchanger and a design method thereof

Abstract

The present invention belongs to the technical field of heat exchangers, and in particular, relates to a heat exchanger and a design method thereof, including a shell and a tube bundle, wherein the tube bundle includes: a plurality of tube units arranged in parallel, the tube unit including a plurality of straight tube sections, and each straight tube section is connected in sequence to form a curved tube section of a corrugated tube body, and a circulation space with both ends open is formed inside the tube unit; two annular tubes, an annular space is formed inside, the annular space is connected to one end of the circulation space of each tube unit, and the two annular tubes are respectively connected to the tube inlet and outlet of the heat exchanger; the medium flow direction in the shell of the heat exchanger is perpendicular to the length direction of the straight tube section in the tube unit. In the present invention, the processing difficulty of tube sheet welding in the traditional heat exchanger is solved through the design of the annular tube and the corrugated tube unit, and a more flexible fixing method is realized. By optimizing the flow path, the shell and tube media flow vertically, which increases the heat exchange surface area and flow time, and significantly improves the heat exchange efficiency.

Description

Technical Field

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

[0002] Shell and tube heat exchanger is a common heat exchange equipment, widely used in chemical, petroleum, energy, pharmaceutical, food and other fields. Its structure includes a shell with a tube bundle installed inside. The tube bundle consists of several parallel tubes. The tube body can be in the form of smooth tubes, threaded tubes, corrugated tubes, etc. The two ends of the tube bundle are fixed by tube sheets respectively, and the tube sheets are fixed relative to the shell; it also includes a head, which is installed at both ends of the shell to form a cavity between the tube sheet, and the cavity is connected to the internal space of the tube bundle. The working principle of the shell and tube heat exchanger is to transfer heat through the temperature difference between the shell side medium and the tube side medium. For example, the hot medium flows in the shell side, and the cold medium flows in the tube side. The heat is transferred from the hot medium to the cold medium through the tube wall, thereby achieving the purpose of heat exchange.

[0003] For the shell and tube heat exchanger with the above-mentioned structural form, the welding of the tube sheet and the tube bundle is a very critical step in the manufacturing process of the shell and tube heat exchanger. This process has a direct impact on the sealing, pressure resistance and service life of the equipment. Due to the high requirements on welding quality, the welding difficulty of the tube sheet and the tube bundle is relatively large. For example, the tube bundle and the tube sheet are usually made of different materials, and the thermal expansion coefficients of different materials are different. Stress is easily generated during the welding process, resulting in cracking or deformation of the weld; during the welding process, the tube sheet is usually thicker, and a large amount of heat input is required during the welding process, which easily leads to stress concentration in the weld area, thereby increasing the risk of welding cracks. In order to reduce welding stress and deformation, the welding sequence must be carefully designed. The wrong welding sequence may cause warping of the tube sheet or displacement of the tube bundle.

[0004] In addition, during the heat exchange process of the above-mentioned equipment, the hot and cold media often flow in parallel and countercurrently in the heat exchanger. In the heat exchanger, the efficiency of heat transfer depends to a large extent on the contact area between the hot medium and the cold medium. Under the parallel flow mode, the heat exchange efficiency is difficult to improve due to the limited heat exchange area displayed by the tube bundle in the shell. Summary of the invention

[0005] The present invention provides a heat exchanger and a design method thereof, which can effectively solve the problems in the background technology.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A heat exchanger comprises a shell having a cavity, and a tube bundle located in the cavity, wherein the tube bundle comprises:

[0008] A plurality of tube units arranged in parallel, the tube units comprising a plurality of straight tube sections arranged in parallel along the length direction of the shell, and a curved tube section of a corrugated tube body formed by sequentially connecting the straight tube sections, and a flow space with two ends open is formed inside the tube units;

[0009] Two annular tubes are fixedly connected to the inner wall of the cavity through a connector, an annular space is formed inside the annular tube, the annular space is connected to one end of the flow space of each tube unit, and the two annular tubes are respectively connected to the tube inlet and outlet of the heat exchanger;

[0010] The medium flow direction in the shell side of the heat exchanger is perpendicular to the length direction of the straight pipe section in the pipe body unit.

[0011] Furthermore, the straight pipe sections in the pipe body unit are arranged in a row.

[0012] Furthermore, the straight pipe sections in the pipe body unit include two situations: arranged in one row and arranged in at least two rows;

[0013] In the pipe body unit in which the straight pipe sections are arranged in at least two rows, the straight pipe sections are arranged in series through the connection of the curved pipe sections.

[0014] Furthermore, the tube units are distributed in parallel into several levels, and the number of the tube units in each level includes one, or more than one.

[0015] Furthermore, the distribution density and pipe body cross-section of the straight pipe sections in different rows are the same.

[0016] Furthermore, the deviation of the path lengths for the medium to flow in different tube units is within a set range.

[0017] Furthermore, between different tube units, and / or within the same tube unit, the following structures are included:

[0018] One side of the two rows of straight pipe sections is connected respectively, and the two adjacent rows of curved pipe sections are inserted into the gaps between the two adjacent rows of straight pipe sections one by one.

[0019] Furthermore, the connector is an annular space connecting the annular tube body and the tube body structure outside the heat exchanger.

[0020] A method for designing a heat exchanger as described above comprises:

[0021] Determining the heat exchange efficiency range of the heat exchanger and the size of the shell;

[0022] In the shell, the distribution mode of the straight pipe section and the pipe size in the pipe unit are comprehensively determined according to the heat exchange efficiency, the design scheme of the pipe unit is obtained, and the design scheme of the annular pipe and the connector is completed accordingly;

[0023] The pipe unit design scheme satisfies:

[0024] The deviation of the circulation time of the medium in each of the tube units is within a set time range, and / or the deviation of the temperature of the medium flowing out of each of the tube units is within a set temperature range.

[0025] Furthermore, it also includes designing the connection position between each of the tube units and the annular tube according to the tube unit design scheme to form a connection point design scheme:

[0026] The connection point design of the annular tube on both sides meets the following requirements:

[0027] In different annular regions of the annular tube body, the arrangement density deviation of the connection points is within a set range.

[0028] The technical solution of the present invention can achieve the following technical effects:

[0029] The present invention solves the processing problem of tube sheet welding in traditional heat exchangers through the design of annular tube body and corrugated tube body units, realizes a more flexible fixing method, and optimizes the flow path so that the shell side and tube side media flow vertically, thereby increasing the heat exchange surface area and flow time, and significantly improving the heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a schematic diagram of the assembly process of the heat exchanger in the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of the tube bundle;

[0033] Figure 3 It is a local schematic diagram of the tube unit;

[0034] Figure 4 It is a schematic diagram of the flow of shell-side medium relative to the tube bundle;

[0035] Figure 5This is a schematic diagram of the first method of connecting different rows of straight pipe sections in series;

[0036] Figure 6 It is a schematic diagram of the second method of connecting different rows of straight pipe sections in series;

[0037] Figure 7 It is a schematic diagram of the third method of connecting different rows of straight pipe sections in series;

[0038] Figure 8 It is a schematic diagram of the fourth method of connecting different rows of straight pipe sections in series;

[0039] Fig. 9 is a schematic diagram of a first partial cross section inside the shell;

[0040] Fig.10 is a second partial cross-sectional schematic diagram inside the shell;

[0041] Fig.11 is a third partial cross-sectional schematic diagram inside the shell;

[0042] Fig.12 It is a schematic diagram of two rows of curved pipe sections being inserted into the gaps between two adjacent rows of straight pipe sections one by one;

[0043] Reference numerals: 01, shell; 02, tube bundle; 03, first unit; 04, second unit;

[0044] 1. Pipe body unit; 11. Straight pipe section; 12. Bend pipe section; 2. Annular pipe body; 3. Connector. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0047] Embodiment 1

[0048] like Figure 1 and 2 As shown, a heat exchanger includes a shell 01 having a cavity, and a tube bundle 02 located in the cavity, wherein the tube bundle 02 includes:

[0049] A plurality of tube units 1 are arranged in parallel, and the tube units 1 include a plurality of straight tube sections 11 arranged in parallel along the length direction of the shell 01, and the straight tube sections 11 are connected in sequence to form a curved tube section 12 of a corrugated tube body, and a flow space with two ends open is formed inside the tube unit 1; Figure 1 and Figure 2 In the figure, a schematic diagram of setting three tube body units 1 is shown. In order to make the attached figure able to show the structure more clearly, the number of tube body units 1 is appropriately reduced. In actual use, the number of tube body units 1 will be more than that shown in the figure, and they will often be relatively evenly distributed in the shell 01.

[0050] The two annular tube bodies 2 are fixedly connected to the inner wall of the cavity through a connector 3. An annular space is formed inside the annular tube body 2. The annular space is connected to one end of the flow space of each tube body unit 1. The two annular tube bodies 2 are respectively connected to the tube inlet and outlet of the heat exchanger; the medium flow direction in the shell side of the heat exchanger is perpendicular to the length direction of the straight tube section 11 in the tube body unit 1.

[0051] The present invention provides a new type of heat exchanger, through the use of the heat exchanger can mainly achieve the following two technical effects:

[0052] Firstly, the use of the annular tube body 2 effectively solves the processing difficulty caused by the welding of the tube sheet and the tube bundle. The annular tube body 2 directly participates in the circulation process of the medium as a part of the tube process, replaces the internal space between the original head and the tube sheet, and realizes the effective fixation of the ends of each tube unit 1; the fixing form of the annular tube body 2 relative to the shell 01 is more flexible, and the specific connector 3 structure can be selected according to actual needs; the tube unit 1 is set as a corrugated tube body, so that the tube unit 1 itself can obtain appropriate stress buffering. The buffering direction here mainly refers to the buffering along the length direction of the shell 01, which is extremely beneficial to reducing the difficulty of connecting the tube unit 1 and the annular tube body 2. When different tube units 1 have slight deviations in the length direction due to processing and other reasons, the structural characteristics brought by the corrugation can ensure the smooth installation of different tube units 1 on the one hand, and on the other hand, it can also reduce the probability of structural problems of the annular tube body 2 due to uneven force after different tube units 1 are connected to the annular tube body 2.

[0053] Secondly, by optimizing the structure of the tube unit 1, the original working mode of parallel and reverse flow of cold and hot media is changed, and a flow path with a vertical relationship is obtained; see Figure 4, the surface area of ​​each tube unit 1 in the tube bundle 02 located in the shell 01 for heat exchange is greatly increased, and the heat exchange efficiency is effectively improved when the volume of the shell 01 remains the same; in the process of parallel reverse flow, there is no collision between the shell-side medium and the tube-side medium, and the flow process is often relatively stable. In the present invention, the shell 01 medium will inevitably collide with the straight tube section 11 of the tube unit 1 during the flow process, see Figure 3 This collision will change the flow direction of the shell-side medium. On the one hand, this process will extend the flow time of the shell-side medium. On the other hand, when the shell-side medium flows along the side wall of the straight tube section 11, more sufficient heat exchange will be carried out, thereby further improving the heat exchange efficiency.

[0054] In summary, the present invention solves the processing difficulties of tube sheet welding in traditional heat exchangers through the innovative design of the annular tube body 2 and the corrugated tube body unit 1, realizes a more flexible fixing method, and optimizes the flow path so that the shell and tube media flow vertically, thereby increasing the heat exchange surface area and circulation time, and significantly improving the heat exchange efficiency.

[0055] As a preference of the above embodiment, the pipe unit 1 may have the following structure: the straight pipe sections 11 in the pipe unit 1 are arranged in a row. Figure 2 This situation is shown in FIG. 1 , where the straight pipe sections 11 in the three pipe body units 1 are arranged in a row.

[0056] As another embodiment, the straight pipe sections 11 in the pipe body unit 1 include two situations: arranged in one row and arranged in at least two rows; in the pipe body unit 1 in which the straight pipe sections 11 are arranged in at least two rows, the straight pipe sections 11 are arranged in series through the connection of the curved pipe sections 12.

[0057] In this preferred embodiment, the straight pipe sections 11 are arranged in one row, as described above, and will not be repeated here; and for the case where the straight pipe sections 11 are arranged in at least two rows, such as Figure 5 As shown, the straight pipe sections 11 in different columns are connected in series to form an independent pipe unit 1. The figure shows a series connection form, in which the straight pipe sections 11 connected in series are distributed in the same plane, and the ends of adjacent columns are connected through a common straight pipe section 11 with a properly lengthened length; Figure 6 As shown, another form of series connection is shown, in which the straight pipe sections 11 after series connection are distributed in different planes, and the ends of each column are connected by a common curved pipe section 12; the above two forms can be used independently or together, such as Figure 7 As shown, Figure 5 and Figure 6The series form commonly used in the structure includes the situation where different columns of straight pipe sections 11 are distributed in the same plane or in different planes, all of which are within the protection scope of the present invention; in order to ensure that the inlet and outlet of the pipe body unit 1 are respectively located on both sides, the straight pipe sections 11 need to be set to an odd number of 3 or more columns.

[0058] As a structural optimization form in which the straight pipe section 11 is arranged in two rows, and the outlet and the inlet are located on both sides, such as Figure 8 As shown, the straight pipe sections 11 are connected one by one across the rows through the curved pipe sections 12; in contrast, Figure 5 In the case of the curved pipe section 12, the straight pipe section 11 is connected in the same column. Figure 6 Only one curved pipe section 12 is connected to the straight pipe section 11 across the row, and the remaining curved pipe sections 12 are connected to the straight pipe sections 11 in the same row.

[0059] In this embodiment, the tube units 1 are connected in parallel, while the tube units 1 are partially connected in series. This solution can at least play an advantage in the following situations: Fig. 9 As shown:

[0060] In the actual production process, the shell 01 structure of the heat exchanger often adopts a cylindrical barrel form, and the tube unit 1 needs to be relatively evenly distributed in the shell 01 to ensure the uniformity of heat exchange, such as Fig. 9 As shown, a local cross-section inside the shell 01 is shown. In the figure, each row of straight pipe sections 11 is distributed in the same plane, and when the planes of different rows are distributed in parallel, the row of straight pipe sections 11 closer to the diameter position of the shell 01 (the tube body unit 1 in which it is located is named as the first unit 03 here) will obtain a longer length due to the larger distribution space, while the row of straight pipe sections 11 farther away from the diameter position of the shell 01 (the tube body unit 1 in which it is located is named as the second unit 04 here) will obtain a shorter length due to the limited distribution space. In this case, there are often the following problems: the medium flowing inside the first unit 03 will obtain a longer flow path, while the medium flowing inside the second unit 04 will obtain a shorter flow path. Due to the large difference in the flow paths, the time for the internal medium to participate in heat exchange will be greatly different. Therefore, when the medium flows into the tube pass at the same temperature, the temperature of the medium flowing out of the tube pass will be greatly different. This situation will inevitably cause differences in the temperature of the medium flowing into different positions of the annular tube body 2, thereby posing a threat to the structural stability of the annular tube body 2.

[0061] In this embodiment, the straight pipe sections 11 in the pipe unit 1 can be arranged in one row or in two or more rows in series. Fig.10In the local cross-section inside the shell 01 shown in the figure, the three columns of straight pipe sections 11 in the dotted frame are connected in series to obtain the pipe body unit 1, and the straight pipe sections 11 in the other columns are independently used as the pipe body unit 1, so that the flow path length deviation of the medium in different pipe body units 1 can be within the set range, thereby ensuring that the temperature deviation of the medium entering each part of the annular pipe body 2 is within the set range, thereby ensuring the structural stability of the annular pipe body 2 during use and the connection effectiveness of each connection.

[0062] As a preferred embodiment of the above, Fig.11 In the local cross section of the shell 01 shown in FIG. 1 , the pipe units 1 are distributed in parallel in several levels, and the number of pipe units 1 in each level includes one, or more than one.

[0063] Through this preferred solution, the internal space of the shell 01 can be more effectively utilized, and through reasonable arrangement, the connection points between each tube unit 1 and the annular tube 2 can be more evenly distributed, thereby effectively ensuring the structural stability of the annular tube 2; Fig.11 Five levels are shown in the figure, the top level includes one tube unit 1, the three middle levels each include two tube units 1, and the bottom level includes three tube units 1.

[0064] In the specific implementation process, the above-mentioned hierarchical division and the division of the tube body units 1 within the hierarchical levels can be comprehensively selected under various circumstances, taking into account that the deviation range of the flow paths between different tube body units 1 should not be too large, that different tube body units 1 in the shell 01 need to be relatively evenly distributed, and comprehensively considering the tube cross-sectional size and the length of the tube flow path. However, even if a variety of different distribution forms are obtained, they are all within the protection scope of the present invention; it should be noted here that the straight pipe sections 11 in each tube body unit 1 located in the same level can be distributed along the same plane, or there can be a certain height misalignment. The hierarchical limitation represents a certain range, and the height misalignment referred to here can be between the straight pipe sections 11 of different tube body units 1, or between the straight pipe sections 11 of the same tube body unit 1.

[0065] In order to reduce the difficulty of design and processing, the distribution density and pipe cross-section of the straight pipe sections 11 in different columns are the same. This situation is obviously the best for design calculation and processing material preparation. However, this situation is not the only one. When there are special needs and the distribution density of the pipe body at different positions and / or the pipe body cross-section need to be changed, it is also within the protection scope of the present invention.

[0066] As a preferred embodiment of the above, the path length deviation of the medium flowing in different tube units 1 is within a set range. Fig. 9 The technical effects of this optimization scheme have been explained in the description and will not be repeated here.

[0067] As a preferred embodiment of the above, Fig.12 As shown, different tubular body units 1, and / or the same tubular body unit 1, include the following structures:

[0068] The two rows of straight pipe sections 11 are connected to one side and the two adjacent rows of curved pipe sections 12 are connected to one side. Fig.12 The two boxes on the left side are inserted into the gaps between the two straight pipe sections 11 in the adjacent rows one by one, so as to form a Fig.12 The twist structure shown in the right frame in the middle. In this way, the pipe units 1 in different rows can be kept in a more stable use state, so that the pipe bundle 02 forms a more stable whole, and the connection stability between the pipe bundle 02 and the annular pipe body 2 is improved.

[0069] In the implementation process, a bracket-like structure can be used for the selection of the connector 3 to ensure the fixed connection between the annular tube 2 and the inner wall of the cavity. As another better way, the connector 3 is an annular space connecting the annular tube 2 and the tube structure outside the heat exchanger, which can effectively simplify the structural form of the heat exchanger. The tube structure here realizes multifunctionality, on the one hand, it allows the medium to circulate, and on the other hand, it realizes the support and fixation of the structure. Of course, in the implementation process, in order to further ensure the stability of the structure, an additional bracket structure can be used on the basis of the above-mentioned connector 3.

[0070] Embodiment 2

[0071] A specific design method for the heat exchanger includes:

[0072] S1: Determine the heat exchange efficiency range of the heat exchanger and the size of the shell 01; this step is the design condition in this specific design method. The heat exchange efficiency and the size of the shell 01 often need to be determined based on the actual working conditions of the heat exchanger, so as to ensure the effective implementation of the complete process flow;

[0073] S2: In the shell 01, the distribution mode and the size of the straight pipe section 11 in the pipe unit 1 are comprehensively determined according to the heat exchange efficiency, and the design scheme of the pipe unit 1 is obtained, and the design scheme of the annular pipe 2 and the connector 3 is completed accordingly; the distribution mode in this step includes but is not limited to the length of the straight pipe sections 11 in different columns, the distribution density of the straight pipe sections 11 in each column, the selection of different column groupings when multiple columns are connected in series, and the selection of different column positions when different columns are connected in parallel, etc., and the pipe size mainly includes the cross-sectional size of the pipe body; when the design of the pipe unit 1 is completed, the difficulty of the design scheme of the annular pipe 2 and the connector 3 is relatively low. For the annular pipe 2, it is necessary to ensure that the medium can smoothly and fluently enter each pipe unit 1 as a buffer space, and ensure that the medium of each path is collected and then flows out in a centralized manner;

[0074] Among them, the design scheme of the pipe unit 1 meets the following requirements:

[0075] Condition 1: The deviation of the circulation time of the medium in each tube unit 1 is within the set time range, and / or, Condition 2: The deviation of the temperature of the medium flowing out of each tube unit 1 is within the set temperature range. In the implementation process, if one of the above conditions is met, or both are met, it is within the protection scope of the present invention.

[0076] The above conditions are limited to ensure that the temperature of the medium flowing out of each pipe unit 1 is relatively uniform, thereby avoiding the internal stress of the equipment caused by the temperature, which may lead to local structural failure.

[0077] During the implementation process, the structural stress changes brought about by the temperature changes are mainly caused by the problem of thermal expansion and contraction. Further comprehensive processing considerations, as a preferred embodiment of the above embodiment, also include designing the connection position of each tube unit 1 and the annular tube 2 according to the tube unit 1 design scheme to form a connection point design scheme: the connection point design scheme of the annular tube 2 on both sides meets:

[0078] In different annular regions of the annular tube body 2, the arrangement density deviation of the connection points is within a set range.

[0079] In this preferred embodiment, the different areas referred to can be obtained by partitioning the annular range, such as dividing the annular range into three equal parts, four equal parts, etc., all within the protection scope of the present invention; in the process of determining the area, the number of equal parts can be determined according to the total number of connection points determined by the design scheme of the pipe body unit 1, and the number of connection points in each area is guaranteed to be an integer as much as possible, so that the comparison of density deviation is easier. Because in actual working conditions, it is difficult to ensure that the distribution density of the connection points is completely uniform, although this is an optimal ideal state, so in this application, the distribution form of the connection points is guaranteed by density deviation. Through this optimization method, the stress deviation of the annular pipe body 2 caused by welding can be within the set range, and the distribution density of different pipe body units 1 in the shell 01 can also be determined to a certain extent. The comprehensive design scheme of the pipe body unit 1 can ultimately ensure that the two media in the shell side and the tube side can obtain more uniform heat exchange, and can also ensure that the stress of the equipment caused by the work is equivalent to uniform.

[0080] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A heat exchanger, characterized in that: The invention comprises a shell having a cavity, and a tube bundle located in the cavity, wherein the tube bundle comprises: A plurality of tube units arranged in parallel, the tube units comprising a plurality of straight tube sections arranged in parallel along the length direction of the shell, and a curved tube section of a corrugated tube body formed by sequentially connecting the straight tube sections, and a flow space with two ends open is formed inside the tube units; Two annular tubes are fixedly connected to the inner wall of the cavity through a connector, an annular space is formed inside the annular tube, the annular space is connected to one end of the flow space of each tube unit, and the two annular tubes are respectively connected to the tube inlet and outlet of the heat exchanger; The medium flow direction in the shell side of the heat exchanger is perpendicular to the length direction of the straight tube section in the tube unit; The straight pipe sections in the pipe body unit include two situations: arranged in one row and arranged in at least two rows; in the pipe body unit in which the straight pipe sections are arranged in at least two rows, the straight pipe sections are arranged in series through the connection of the curved pipe sections; The following structures are included between different tubular body units and / or within the same tubular body unit: One side of the two rows of straight pipe sections is connected respectively, and the two adjacent rows of curved pipe sections are inserted into the gaps between the two adjacent rows of straight pipe sections one by one.

2. The heat exchanger according to claim 1, characterized in that: The tube units are distributed in parallel into several levels, and the number of the tube units in each level includes one, or more than one.

3. The heat exchanger according to claim 1, characterized in that: The distribution density and pipe body cross-section of the straight pipe sections in different rows are the same.

4. The heat exchanger according to claim 3, characterized in that The path length deviations for the medium to flow through different tube units are within a set range.

5. The heat exchanger according to claim 1, characterized in that: The connector is an annular space connecting the annular tube body and the tube body structure outside the heat exchanger.

6. A method for designing a heat exchanger according to claim 1, characterized in that: include: Determining the heat exchange efficiency range of the heat exchanger and the size of the shell; In the shell, the distribution mode of the straight pipe section and the pipe size in the pipe unit are comprehensively determined according to the heat exchange efficiency, the design scheme of the pipe unit is obtained, and the design scheme of the annular pipe and the connector is completed accordingly; The pipe unit design scheme satisfies: The deviation of the circulation time of the medium in each of the tube units is within a set time range, and / or the deviation of the temperature of the medium flowing out of each of the tube units is within a set temperature range.

7. The method for designing a heat exchanger according to claim 6, characterized in that: The method further includes designing the connection position between each of the tube units and the annular tube according to the tube unit design scheme to form a connection point design scheme: The connection point design of the annular tube on both sides meets the following requirements: In different annular regions of the annular tube body, the arrangement density deviation of the connection points is within a set range.

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