A double-layer plate-tube type heat exchanger

Abstract

The present invention provides a double-layer tube-sheet heat exchanger. The heat exchange tubes are divided into two layers. The first layer of heat exchange tubes is in the first chamber of the first head, and the first layer of heat exchange tubes communicates with the first chamber of the second head. Among them, the second chamber of the first head communicates with the second layer of heat exchange tubes, and the second layer of heat exchange tubes communicates with the second chamber of the second head; the first chamber and the second chamber of the first head are respectively provided with a first inlet and a first outlet for the shell-side fluid, and the first chamber and the second chamber of the second head are respectively provided with a second inlet and a second outlet for the shell-side fluid. By arranging two layers of heat exchange tubes in the present invention, the fluid flow directions of the two layers of heat exchange tubes are opposite, so that the heat exchange is uniform in the overall flow direction of the heat exchange tubes, thereby strengthening the heat transfer.

Description

Technical Field

[0001] The present invention relates to a heat exchanger, belonging to the technical field of heat exchangers, and in particular to a double-layer plate-tube plate heat exchanger. Background Art

[0002] Heat exchangers are extremely common in industrial production. For example, they play very important roles in various industrial sectors such as chemical industry, power, metallurgy, construction, machinery manufacturing, food, medicine, and aerospace. Therefore, it is necessary for industries using heat exchangers to optimize the design of heat exchangers to improve heat transfer efficiency. For the automotive industry, it is also an urgent problem to optimize the design of the exhaust gas recirculation cooler of the automotive engine, improve the heat transfer efficiency to reduce the emissions of nitrogen oxides, and make the exhaust gas emissions meet the increasingly stringent exhaust gas emission standards.

[0003] Due to the limitations of manufacturing processes and technical levels, early heat exchangers could only adopt simple structures, with small heat transfer areas, large volumes, and being bulky, such as coil heat exchangers. With the development of manufacturing processes, the shell-and-tube heat exchanger has a relatively large heat transfer area per unit volume and good heat transfer effects, and has long been a typical heat exchanger in industrial production. Plate heat exchangers emerged in the 1920s and were applied to the food industry. The heat exchanger made of plates instead of tubes has a compact structure and good heat transfer effects. After the 1980s, a large number of enhanced heat transfer elements were introduced to the market, and the manufacturing processes of heat exchangers such as plate-and-shell heat exchangers were further improved, thus promoting the vigorous development and wide application of compact heat exchangers.

[0004] In the existing plate heat exchangers, the fluid in the shell side always flows horizontally through the flat surface of the flat tube, so it flows perpendicular to the fluid in the flat tube. Compared with the countercurrent heat transfer method, the heat transfer capacity of the above heat transfer method is insufficient. Therefore, in order to enhance heat transfer, for the plate side, generally, the method of setting baffles is adopted to realize the U-shaped flow of the fluid on the plate side. For example, Chinese Patent Publication No. CN101040163A discloses such a structure. For example, the structure of a U-shaped tube can also be adopted, or baffles can be set in the plate side head to realize the multi-pass flow of the fluid on the plate side to enhance heat transfer. In the above structures, the fluid on the plate side directly flows from the plate side inlet to the plate side outlet. During the fluid flow process, the heat transfer capacity of the cold fluid also gradually decreases, and the degree of decrease becomes larger and larger. Although there is a certain improvement in enhancing heat transfer, overall, there are still differences in the heat transfer capacity in the flow directions of the fluid in the shell side and the fluid in the plate side, resulting in uneven heat transfer along the flow direction of the fluid in the tube, causing uneven heat transfer of the overall heat exchange tube along the flow direction of the fluid in the tube and leading to a decrease in heat transfer efficiency. Therefore, the present invention designs a new type of double-layer plate-tube plate heat exchanger to improve the structure of the traditional plate heat exchanger to achieve the purpose of enhancing heat transfer. Summary of the Invention

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A double-layer tube-sheet heat exchanger, the heat exchanger comprising a tube side and a shell side, the tube side comprising a first head, a second head, a tube sheet and heat exchange tubes, the two ends of the heat exchange tubes being fixedly installed on the tube sheet, and the heat exchange tubes being arranged inside the tube-side shell; characterized in that the heat exchange tubes inside the shell are divided into two layers, namely a first layer and a second layer, a partition wall is arranged inside the first head and the second head, dividing the first head into a first chamber and a second chamber, and dividing the second head into a first chamber and a second chamber, wherein the first chamber of the first head is connected to the first-layer heat exchange tubes, the first-layer heat exchange tubes are connected to the first chamber of the second head, wherein the second chamber of the first head is connected to the second-layer heat exchange tubes, and the second-layer heat exchange tubes are connected to the second chamber of the second head; a first inlet and a first outlet of the tube-side fluid are respectively arranged in the first chamber and the second chamber of the first head, and a second inlet and a second outlet of the tube-side fluid are respectively arranged in the first chamber and the second chamber of the second head.

[0007] As an improvement, the heat exchange tubes are plate-type tube sheets, and the heat exchange tubes of the first layer and the second layer are in a one-to-one correspondence relationship. The plate-type tube sheet comprises a long side and a short side, and the short sides of the first-layer heat exchange tubes are opposite to the short sides of the second-layer heat exchange tubes.

[0008] As an improvement, a shell-side fluid inlet and an outlet are arranged on the shell side, and the connection line between the shell-side fluid inlet and the outlet forms an angle of 30-150° with the flow direction inside the heat exchange tubes, wherein the connection line between the shell-side fluid inlet and the outlet is the connection line between the central points of the openings of the shell-side fluid inlet and the outlet on the shell.

[0009] As an improvement, the connection line between the shell-side fluid inlet and the outlet forms an angle of 90° with the flow direction inside the heat exchange tubes.

[0010] As an improvement, the first-layer heat exchange tubes are provided with a plurality of mutually parallel first plate-type tube sheets, the second-layer heat exchange tubes are provided with a plurality of mutually parallel second plate-type tube sheets, and one row of heat exchange tubes is arranged in each layer.

[0011] As an improvement, the short sides of the first-layer heat exchange tubes are close to the tube-side inlet, and the long sides of the second-layer heat exchange tubes are close to the tube-side outlet.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] In the present invention, the plate-type plate-and-tube heat exchange tubes are divided into a first layer and a second layer, and the short sides of the plate-type plate-and-tube heat exchange tubes in each layer correspond one by one. Thus, in the inlet and outlet directions of the shell-side fluid, one plate-type plate-and-tube heat exchange tube of the first layer and one plate-type plate-and-tube heat exchange tube of the second layer are arranged in each row. These two plate-type plate-and-tube heat exchange tubes can be regarded as one plate-type plate-and-tube heat exchange tube. The two end heads are also divided into two parts, and the tube-side fluid is divided into two parts. One part enters from the first end head and flows out from the second end head, and the other part enters from the second end head and flows out from the first end head. The two parts of the fluid are separated from each other and form a countercurrent structure. Because the upper and lower tube-side fluids flow in opposite directions, the heat transfer capacity of the upper part is strong, and correspondingly, the heat transfer capacity of the lower part is weak. Similarly, if the heat transfer capacity of the upper part is weak, the heat transfer capacity of the lower part is strong. In this way, along the length direction of the overall heat exchange tubes, the average heat transfer amount per unit length is basically the same, the heat transfer capacity is basically uniform, and there will be no problem of uneven heat transfer capacity in the length direction locally. Thus, a heat transfer effect similar to overall countercurrent is achieved, and the purpose of enhancing heat transfer is realized. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the overall structure of the heat exchanger of the present invention;

[0015] Figure 2 is a schematic diagram of the sectional structure of the heat exchanger of the present invention;

[0016] Figure 3 is a schematic diagram of the cross-sectional structure of the plate-type plate-and-tube heat exchange tube of the present invention;

[0017] Figure 4 is a schematic diagram of the arrangement structure of the inner fins in the flat tubes of the heat exchanger of the present invention. Detailed Embodiment

[0018] In this article, if not otherwise specified, for formulas, " / " represents division, and "×", "*" represent multiplication.

[0019] In the description of the present invention, the expressions of the terms "left" and "right" are based on the position or orientation relationship shown in the drawings, and do not indicate or imply the specific installation and operation orientations that the described device or component must have. Therefore, it cannot be understood as a limitation to the present invention.

[0020] Next, the technical solutions in the embodiments of the present invention will be supplemented with reference to the drawings in the embodiments of the present invention.

[0021] Figures 1-3 A heat exchanger with double-layer tubes is disclosed. The shell-and-tube heat exchanger includes a tube side (i.e., the tube pass) and a shell side, and the shell side includes a shell 1. The tube side includes a first end head 2, a second end head 3, a tube sheet 4, and heat exchange tubes 5. The two ends of the heat exchange tubes 5 are fixedly installed on the tube sheet 4. The tube-side fluid enters the heat exchange tubes 5 from the inlet end head and then flows out from the outlet end head.

[0022] As an improvement, the heat exchange tube 5 is a plate-type tube 5, the plate-type tube 5 includes a long side 51 and a short side 52, the heat exchange tubes in the shell are divided into two layers, namely the first layer 53 and the second layer 54, partition walls 21 and 31 are respectively arranged inside the first head 2 and the second head 3, the first head 2 is divided into a first chamber 22 and a second chamber 23, the second head 3 is divided into a first chamber 32 and a second chamber 33, wherein the first chamber 22 of the first head 2 communicates with the first layer of plate-type tubes 53, the first layer of plate-type tubes 53 communicates with the first chamber 32 of the second head, wherein the second chamber 23 of the first head communicates with the second layer of plate-type tubes 54, the second layer of plate-type tubes 54 communicates with the second chamber 33 of the second head; a first inlet 34 and a first outlet 45 of the shell-side fluid are respectively arranged in the first chamber and the second chamber of the first head, and a second outlet 44 and a second outlet 35 of the shell-side fluid are respectively arranged in the first chamber and the second chamber of the second head.

[0023] The heat exchange tube is a plate-type tube, see Figure 3 , the heat exchange tubes of the first layer and the second layer are in a one-to-one correspondence relationship, the plate-type tube includes a long side and a short side, and the short sides of the heat exchange tubes of the first layer are opposite to the short sides of the heat exchange tubes of the second layer. That is, one heat exchange tube of the first layer faces one heat exchange tube of the second layer, and the short sides of these two heat exchange tubes are opposite to each other.

[0024] In the present invention, the plate-type tube heat exchange tubes are divided into a first layer and a second layer, and the short sides of the plate-type tubes in each layer correspond one by one. Thus, one plate-type tube of the first layer and one plate-type tube of the second layer are arranged in each row in the inlet and outlet directions of the shell-side fluid. These two plate-type tubes can be regarded as one plate-type tube, the two heads are also divided into two parts, the shell-side fluid is divided into two parts, one part enters from the first head and flows out from the second head, and the other part enters from the second head and flows out from the first head. The two parts of the fluid are separated from each other and form a countercurrent structure. Because the upper and lower shell-side fluids flow in opposite directions, the heat exchange capacity of the upper part is strong, and correspondingly, the heat exchange capacity of the lower part is weak. Similarly, when the heat exchange capacity of the upper part is weak, the heat exchange capacity of the lower part is strong. In this way, the average heat exchange amount per unit length of the heat exchange tubes is basically the same along the length direction as a whole, the heat exchange capacity is basically uniform, and there will be no problem of uneven local heat exchange capacity in the length direction, thus achieving a heat exchange effect similar to that of overall countercurrent and realizing the purpose of strengthening heat transfer.

[0025] Whether the shell-side fluid and the plate-side fluid of the present invention are in co-current or counter-current, the technical effect of counter-current is achieved. Therefore, it can meet a variety of different flow directions as a whole and has a wide application range.

[0026] As an improvement, a shell-side fluid inlet 6 and an outlet 7 are provided on the shell side, and the connecting line between the shell-side fluid inlet and the outlet forms an angle of 30-150° with the flow direction in the plate-type tube. Since the present invention is a cross flow rather than a pure countercurrent flow, the plate-type tube heat exchange tubes are divided into a first layer and a second layer of heat exchange tubes, and the technical effect of approaching countercurrent heat exchange can be achieved.

[0027] As an improvement, the connecting line between the shell-side fluid inlet and the outlet is the connecting line between the center points of the openings of the shell-side fluid inlet and the outlet on the shell.

[0028] As an improvement, the connecting line between the shell-side fluid inlet and the outlet forms an angle of 90° with the flow direction in the plate-type tube. The advantage of the above setting can be more reflected through the vertical flow, and the technical effect of achieving countercurrent heat exchange regardless of the flow type can be realized.

[0029] See Figure 3 , a plurality of mutually parallel first plate-type tubes are provided in the first layer of heat exchange tubes, and a plurality of mutually parallel second plate-type tubes are provided in the second layer of heat exchange tubes, and one row of heat exchange tubes is provided in each layer. The short side of the first layer of heat exchange tubes is close to the plate-side inlet, and the long side of the second layer of heat exchange tubes is close to the outlet of the plate side. Through the above setting, two heat exchange tubes can be arranged in the fluid flow direction along the plate-side inlet and outlet directions, so that the heat exchange tubes can be regarded as a whole tube on the whole. Compared with the case of setting too many tubes, the heat exchange effect can be improved as a whole.

[0030] As an improvement, the heat exchanger is a horizontal shell-and-tube heat exchanger, and the long side of the plate-type tube is arranged along the vertical direction. The above setting can realize the flow of the horizontal heat exchanger.

[0031] As an improvement, the first layer of heat exchange tubes is located above the second heat exchange tubes, and the first chambers of the first and second heads are located above the second chambers. Through the above setting, the heat exchange effect of the horizontal heat exchanger can be further improved.

[0032] As an improvement, the heat exchanger is a vertical shell-and-tube heat exchanger, and the long side of the plate-type tube is arranged along the horizontal direction. The above setting can realize the flow of the vertical heat exchanger.

[0033] As an improvement, the first layer of heat exchange tubes is located on the left of the second heat exchange tubes, and the first chambers of the first and second heads are located on the left of the second chambers.

[0034] As an improvement, the internal flow volumes of the first layer and the second layer of heat exchange tubes are the same. The dividing wall divides the first and second heads equally. By evenly distributing the chamber volume, heat transfer enhancement can be further achieved.

[0035] As an improvement, the plate-type tube is a flat tube.

[0036] The shell-side fluid passes through the shell-side inlet and is then distributed into the gaps between adjacent plate-type tubes to exchange heat with the heat transfer surface where the long sides of the plate-type tubes are located. Preferably, the short sides of the plate-type tubes are connected to the inner wall of the shell of the shell side, preventing the fluid from flowing away from the inner wall side of the shell and causing fluid short-circuiting.

[0037] Preferably, the cross-section of the shell is rectangular to match the arrangement of the plate-type tubes.

[0038] As an improvement, as Figure 3 shown, the shell-side inlet is connected to the inlet header 21. The inlet header is installed on the shell, and an inlet through-hole 22 is provided on the shell. Preferably, the through-hole is arranged between adjacent plate-type tubes and is preferably a strip-shaped through-hole that extends along the gap between the plate-type tubes. The shell-side outlet is connected to the outlet header 23. The outlet header is installed on the shell, and an outlet through-hole 24 is provided on the shell. Preferably, the outlet through-hole is arranged between adjacent plate-type tubes and is preferably a strip-shaped through-hole that extends along the gap between the plate-type tubes. The fluid enters the inlet header through the shell-side inlet, then enters the gaps between the plate-type tubes in the shell through the through-hole. Then it enters the outlet header and finally flows out from the outlet to complete heat exchange.

[0039] As an improvement, the fluid in the plate side is a gas and the fluid in the shell side is a gas.

[0040] As an improvement, the shell-side fluid is waste gas. Waste heat is realized through the waste gas.

[0041] As an improvement, referring to Figure 1 , the fluids in both the first heat exchange tube and the second heat exchange tube are provided by a fluid source 8. After heat exchange in the inner cavity of the heat exchange tube and the second heat exchange tube, they converge and enter the fluid source 8.

[0042] As an improvement, as Figure 4 shown, fins 56 are arranged inside the plate-type tubes. The first fins extend from one long side 51 of the plate-type tube towards the other long side, and the second fins extend from the other long side towards one long side. These two types of fins are arranged alternately at intervals, so that the fluid inside the plate-type tubes forms a curved flow direction. Fluid flow short-circuiting can be avoided, and at the same time, the fins are arranged to increase the heat transfer area, further achieving the technical effect of enhancing heat transfer.

[0043] As an improvement, in a horizontal heat exchanger, the long sides of the plate-type tubes are arranged along the horizontal direction, and the partition wall is arranged in the horizontal direction. The fluid in the plate side is a gas. Along the flow direction of the gas inside the plate-type tubes, the extension length of the first fins gradually increases, and the extension length of the second fins gradually decreases.

[0044] During the research process, it was found that the heat transfer on the cross-section of the plate-type tube in the fluid flow direction was uneven. As the distance from the inlet increased, the gas density in the plate pass was small, so the gas flowed upward, resulting in a significant increase in the upper gas. Therefore, it was necessary to design a heat exchange structure for improvement. Along the gas flow direction of the present invention, the lengths of the first fin and the second fin change, so that the gas in the plate-type tube gradually decreases in upward movement as it flows, and more time is retained in the middle and lower parts, strengthening the heat transfer in the center and lower part of the plate-type tube, changing the past heat exchange method, enhancing the heat exchange efficiency at different positions, making the overall heat transfer uniform, and further achieving the purpose of strengthening heat transfer.

[0045] As an improvement, along the gas flow direction in the plate-type tube, the increasing amplitude of the extended length of the first fin gradually increases, and the decreasing amplitude of the extended length of the second fin gradually increases. Through the change of the above amplitude, the overall heat transfer can be made more uniform, and the purpose of strengthening heat transfer is further achieved.

[0046] As an improvement, along the fluid flow direction in the plate-type tube, from the inlet 57 of the plate-type tube to the middle position of the plate-type tube ( Figure 4 the middle position of the long side in ), the spacing between adjacent fins continuously increases. Then from the middle position of the heat exchange tube to the outlet 58 of the plate-type tube, the spacing between adjacent fins continuously decreases. Because during the heat exchange process, the heat exchange amount between the hot and cold fluids is relatively evenly arranged in the flow direction, the overall heat exchange effect is the best. However, it was found in experiments and simulations that the heat exchange amount in the middle is significantly greater than that at the inlet and outlet. Therefore, by changing the fin tube spacing, the increased internal heat exchange area also changes regularly, so that the uneven heat exchange amount is compensated by the area change, thereby further improving the heat exchange efficiency.

[0047] As an improvement, from the inlet of the plate-type tube to the middle position of the heat exchange tube, the increasing amplitude of the spacing between adjacent fins continuously increases. Then from the middle position of the heat exchange tube to the outlet of the plate-type tube, the decreasing amplitude of the spacing between adjacent fins continuously decreases. The change of the above amplitude can make the heat exchange amount per unit area of the entire fluid movement more uniform and further improve the heat exchange efficiency.

[0048] A central heating system, the system includes a boiler, the hot water heated in the boiler enters the plate heat exchanger in the heat exchange station, exchanges heat with the cold source in the plate heat exchanger, and then returns to the boiler; the cold source is heated and then enters user heating. The plate heat exchanger is the plate heat exchanger described above.

[0049] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples. The protection scope of the present invention is defined by the appended claims. Without departing from the principle and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but such changes and modifications all fall within the protection scope of the present invention.

Claims

1. A double-layer plate-tube type heat exchanger, the heat exchanger comprising a tube side and a shell side, the tube side including a first head, a second head, a tube sheet and heat exchange tubes, the two ends of the heat exchange tubes being fixedly installed on the tube sheet, the shell side including a shell body, and the heat exchange tubes being arranged inside the shell body; characterized in that, The heat exchange tubes inside the shell are divided into two layers, namely the first layer and the second layer. Partition walls are arranged inside the first head and the second head, dividing the first head into a first chamber and a second chamber, and dividing the second head into a first chamber and a second chamber. The first chamber of the first head is connected to the heat exchange tubes of the first layer, and the heat exchange tubes of the first layer are connected to the first chamber of the second head. The second chamber of the first head is connected to the heat exchange tubes of the second layer, and the heat exchange tubes of the second layer are connected to the second chamber of the second head. The first chamber and the second chamber of the first head are respectively provided with a first inlet and a first outlet for the shell-side fluid, and the first chamber and the second chamber of the second head are respectively provided with a second inlet and a second outlet for the shell-side fluid. A shell-side flow channel of the first layer is formed between the first inlet and the second outlet, and a shell-side flow channel of the second layer is formed between the second inlet and the first outlet. A countercurrent structure is formed between the shell-side fluid of the first layer and the shell-side fluid of the second layer. The heat exchange tubes are plate-type tubes. A shell-side fluid inlet and a shell-side fluid outlet are arranged on the shell. The connecting line between the shell-side fluid inlet and the shell-side fluid outlet forms an angle of 30-150° with the flow direction inside the plate-type tubes. The cross-section of the inner cavity of the plate-type tubes includes a long side and a short side. Fins are arranged inside the plate-type tubes. The first fins extend from one long side of the plate-type tubes towards the other long side, and the second fins extend from the other long side towards one long side. These two types of fins are arranged alternately at intervals, so that the fluid inside the plate-type tubes forms a curved flow direction. The heat exchanger is a horizontal heat exchanger. The long sides of the plate-type tubes are arranged along the horizontal direction, and the partition walls are arranged in the horizontal direction. The fluid inside the shell-side is a gas. Along the flow direction of the gas inside the plate-type tubes, the extension length of the first fins gradually increases, and the extension length of the second fins gradually decreases. Along the flow direction of the gas inside the plate-type tubes, the increasing amplitude of the gradually increasing extension length of the first fins continuously increases, and the decreasing amplitude of the gradually decreasing extension length of the second fins continuously increases.

2. The heat exchanger according to claim 1, wherein, The heat exchange tubes of the first layer and the second layer are in a one-to-one correspondence relationship. The plate-type tubes include a long side and a short side. The short side of the heat exchange tubes of the first layer is opposite to the short side of the heat exchange tubes of the second layer.

3. The heat exchanger according to claim 1, characterized in that, A shell-side fluid inlet and a shell-side fluid outlet are arranged on the shell. The connecting line between the shell-side fluid inlet and the shell-side fluid outlet forms an angle of 30-150° with the flow direction inside the heat exchange tubes, where the connecting line between the shell-side fluid inlet and the shell-side fluid outlet is the connecting line between the center points of the openings of the shell-side fluid inlet and the shell-side fluid outlet on the shell.

4. The heat exchanger according to claim 2, characterized in that, The connecting line between the shell-side fluid inlet and the shell-side fluid outlet forms a 90° angle with the flow direction inside the heat exchange tubes.

5. The heat exchanger according to claim 1, characterized in that, The heat exchange tubes of the first layer are provided with a plurality of mutually parallel first plate-type tubes, and the heat exchange tubes of the second layer are provided with a plurality of mutually parallel second plate-type tubes. Each layer of heat exchange tubes is arranged in a row.

6. A central heating system, the system includes a boiler. The hot water heated in the boiler enters the plate heat exchanger in the heat exchange station, exchanges heat with the cold source in the plate heat exchanger, and then returns to the boiler. The cold source is heated and then enters user heating. The plate heat exchanger is the heat exchanger according to any one of claims 1-5.

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