A vertical heat exchanger with ring cavity baffle

Abstract

This invention provides a vertical heat exchanger with an annular cavity baffle. The baffle has a hollow cavity, and each heat exchange tube is divided into multiple segments, including an upper tube segment, a middle tube segment, and a lower tube segment. The upper tube segment is connected to the upper tube sheet at its upper end and to the cavity of the baffle at its lower end. The lower tube segment is connected to the lower tube sheet at its lower end and to the cavity of the baffle at its upper end. The middle tube segment is connected to the cavities of the upper and lower baffles at its upper and lower ends, respectively. This invention replaces the baffle with a cavity, allowing the baffle to be filled with tube-side fluid, increasing the heat exchange area between the tube-side and shell-side fluids, and further enhancing heat transfer.

Description

TECHNICAL FIELD

[0001] The present application relates to a shell-and-tube heat exchanger, in particular to a vertical heat exchanger with ring-shaped cavity baffle plates. BACKGROUND

[0002] Heat exchangers are indispensable equipment for heat exchange and transfer in chemical production processes. In the fields of petrochemical industry, low-temperature refrigeration, air separation, seawater desalination, etc., low-temperature fluids are often heated or high-temperature fluids are often cooled, and liquids are often vaporized into steam or steam is often condensed into liquid. These processes are closely related to heat transfer, and therefore can be completed through heat exchangers.

[0003] Common heat exchangers include shell-and-tube heat exchangers and plate heat exchangers. Traditional shell-and-tube heat exchangers mostly use smooth tubes as heat exchanger tubes. Compared with various new plate heat exchangers, such traditional shell-and-tube heat exchangers have many disadvantages, such as low heat transfer efficiency, large heat exchanger volume, etc. However, shell-and-tube heat exchangers also have many advantages of their own, such as simple manufacturing, high temperature and pressure resistance, and convenient maintenance. Therefore, it is urgent to develop a double-sided enhanced high-efficiency heat exchanger on the basis of traditional shell-and-tube heat exchangers. At present, some high-efficiency heat exchangers based on secondary development of smooth tubes have appeared in China, but the effect of heat transfer enhancement is not ideal.

[0004] At present, vertical heat exchangers are widely used in the fields of energy, power, chemical industry, metallurgy, environmental protection, etc. and are a kind of heat exchange equipment with very common applications. At the same time, vertical heat exchangers have certain positions in the field of heat exchanger use due to their characteristics of small occupied area, easy manufacturing, low cost, strong adaptability, large processing capacity, reliable work, wide material selection range, and suitability for high temperature and high pressure working conditions. The baffle plate structure of the existing vertical heat exchangers mainly includes two types of bow-shaped baffle plates and spiral baffle plates. The traditional vertical heat exchanger with bow-shaped baffle plates has some defects in addition to the advantages of vertical heat exchangers, such as shell-side flow dead zones, large shell-side pressure loss, easy fouling, and easy occurrence of tube bundle induced vibration, etc. Although the traditional vertical heat exchanger with spiral baffle plates makes the flow form of the shell-side fluid more reasonable, increases the effective flow area, and reduces the flow resistance, the complex arrangement form of the spiral baffle plates makes the processing of the baffle plates more complex, the installation process of the heat exchange tubes is very difficult, the precision of the product is difficult to guarantee, and the overall rigidity of the tube bundle is poor. In addition, the unique triangular space of the spiral baffle plate type heat exchanger causes a large amount of short circuit flow to exist, resulting in a significant decrease in heat exchange efficiency.

[0005] Therefore, it is necessary to improve the vertical heat exchanger, especially the baffle plate, in order to further improve the heat exchange efficiency. SUMMARY

[0006] In order to overcome the defects and deficiencies in the prior art, the vertical heat exchanger with annular cavity baffle plate is provided, the baffle plate is arranged as a hollow cavity, the contact area of two fluids is increased by the cavity, the heat exchange area is increased, the convective heat transfer coefficient of the shell side of the heat exchanger can be improved, and the heat transfer efficiency is effectively improved.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] The vertical heat exchanger with annular cavity baffle plate, the tube-shell heat exchanger comprises a vertically arranged shell, heat exchange pipes, a pipe-side inlet pipe, a pipe-side outlet pipe, a shell-side inlet connecting pipe and a shell-side outlet connecting pipe; a plurality of parallel arranged heat exchange pipe bundles are connected on the upper tube plate and the lower tube plate; the upper end of the upper tube plate is connected with the upper header, and the lower end of the lower tube plate is connected with the lower header; the shell is provided with a baffle plate, and the heat exchange pipes pass through the baffle plate; the baffle plate comprises a circular baffle plate located at the center of the shell and an annular baffle plate located around the shell, and the circular baffle plate and the annular baffle plate are arranged at intervals, characterized in that the baffle plate is provided with a hollow cavity, each heat exchange pipe is divided into a plurality of sections, including an upper pipe section, a middle pipe section and a lower pipe section, wherein the upper end of the upper pipe section is connected with the upper tube plate, and the lower end is communicated with the cavity of the baffle plate; the lower end of the lower pipe section is connected with the lower tube plate, and the upper end is communicated with the cavity of the baffle plate; the upper end and the lower end of the middle pipe section are respectively communicated with the cavities of the upper baffle plate and the lower baffle plate.

[0009] Preferably, the pipe-side fluid is liquid, and the shell-side fluid is gas, and the gas flows from bottom to top, and the liquid flows from top to bottom.

[0010] Preferably, along the flow direction of the gas in the pipe side, the volume of the cavity of the annular baffle plate and / or the circular baffle plate continuously decreases from the pipe-side inlet to the middle position of the pipe side, and then continuously increases from the middle position of the pipe side to the pipe-side outlet.

[0011] Preferably, along the flow direction of the gas in the pipe side, the volume of the cavity of the annular baffle plate and / or the circular baffle plate continuously decreases from the pipe-side inlet to the middle position of the pipe side, and then continuously increases from the middle position of the pipe side to the pipe-side outlet.

[0012] Preferably, the pipe-side inlet pipe is arranged on the lower header, the pipe-side outlet pipe is arranged on the upper header, the shell-side inlet is arranged on the upper part of the shell, and the shell-side outlet is arranged on the lower part of the shell.

[0013] Preferably, the heat exchange pipes are connected to the baffle plate by brazing.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] 1) The present invention replaces the horizontally arranged annular baffle and circular baffle with a cavity, so that the baffle can be filled with tube fluid, increasing the heat exchange area between tube fluid and shell fluid, and further enhancing heat transfer;

[0016] 2) The heat transfer is further enhanced and the overall heat transfer efficiency is improved by the continuous change of the heat transfer area of ​​the baffle cavity along the height direction of the fluid flow. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the shell-and-tube heat exchanger structure with hollow cavity baffles according to the present invention;

[0018] Figure 2 This is a schematic diagram of the improved shell-and-tube heat exchanger of the present invention;

[0019] Figure 3 Schematic diagram of the annular baffle structure of the present invention;

[0020] Figure 4 This is a schematic diagram of the circular baffle structure of the present invention. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] Unless otherwise specified, in this article, " / " represents division, and "×" and "*" represent multiplication.

[0023] It should be noted that, unless otherwise specified, the two-phase flow mentioned in this invention is a gas-liquid two-phase flow, where the gas is an insoluble or sparingly soluble gas, meaning that the gas will not dissolve in the liquid during the heat exchange process.

[0024] Figure 1 The diagram shows a shell-and-tube heat exchanger with a vertically arranged annular cavity baffle plate according to this application. The shell-and-tube heat exchanger includes a vertically arranged shell 1, heat exchange tubes 2, tube-side inlet pipes 3, tube-side outlet pipes 4, shell-side inlet pipe 5, and shell-side outlet pipe 6. A heat exchange tube bundle composed of multiple parallel heat exchange tubes 2 is connected to an upper tube sheet and a lower tube sheet. The upper end of the upper tube sheet is connected to an upper header 7, and the lower end of the lower tube sheet is connected to a lower header 8. A baffle plate is arranged inside the shell 1, and the heat exchange tubes 2 pass through the baffle plate. The baffle plate includes a circular baffle plate 9 located at the center of the shell (see details for the specific structure). Figure 4 ) and the annular baffle 10 located around the shell (see details). Figure 3), the circular baffle 9 and the annular baffle 10 are arranged at intervals, and as an improvement, the baffles are provided with hollow cavities, each heat exchange pipe is divided into multiple sections, including an upper pipe section 21, a middle pipe section 22 and a lower pipe section 23, wherein the upper end of the upper pipe section 21 is connected to the upper tube plate, and the lower end is communicated with the cavity of the baffle, the lower end of the lower pipe section 23 is connected to the lower tube plate, and the upper end is communicated with the cavity of the baffle, and the upper end and the lower end of the middle pipe section 22 are respectively communicated with the cavities of the upper end baffle and the lower end baffle.

[0025] The baffles are provided with cavities, so that the baffles can be filled with tube-side fluid, the heat exchange area of the tube-side fluid and the shell-side fluid is increased, and the heat transfer is further strengthened. Meanwhile, the cavities increase the flow space of the tube-side, and further reduce the flow resistance.

[0026] As an improvement, as shown in Figure 1 The cavities in the baffles are integrally and continuously communicated with one cavity, so that the heat exchange pipes communicated with the cavity are also in a structure of being communicated with each other. For example Figure 1 The horizontal direction of the middle baffle is a cavity, and the heat exchange pipes are communicated with the cavity of the baffle, so that the heat exchange pipes communicated with the cavity are also in a structure of being communicated with each other. Through the integrally and continuously communicated cavity, the fluid pressure inside the heat exchange pipes can be redistributed, so that the internal fluid pressure is balanced, and the heat exchange effect is further improved.

[0027] Preferably, the tube-side fluid is liquid, and the shell-side fluid is gas, the gas flows from bottom to top, and the liquid flows from top to bottom.

[0028] Preferably, along the flow direction of the gas in the tube-side, the volume (or height) of the cavity of the annular baffle and / or the circular baffle is continuously reduced from the inlet of the tube-side to the middle position of the tube-side, and then the volume (or height) of the cavity of the annular baffle and / or the circular baffle is continuously increased from the middle position of the tube-side to the outlet of the tube-side.

[0029] Because in the countercurrent process, the heat exchange amount per unit length of the shell-side and the tube-side along the flow process of the fluid is relatively uniform, so that the overall heat exchange effect is best. However, it is found in experiments and simulations that the heat exchange amount in the middle is obviously larger than that at the inlet and the outlet of the tube-side, so that by changing the volume of the middle cavity, the heat exchange area of the tube-side fluid and the shell-side fluid in the middle cavity also changes, and the heat exchange area increases and decreases along with the increase and decrease of the volume, so that the non-uniformity of the heat exchange amount is compensated by the area change, so as to further improve the heat exchange efficiency.

[0030] Preferably, along the gas flow direction within the tube, from the tube inlet to the middle of the tube, the rate of decrease in the volume (or height) of the central cavity of the annular baffle and / or circular baffle gradually increases, and then from the middle of the tube to the tube outlet, the rate of increase in the volume (or height) of the central cavity of the annular baffle and / or circular baffle gradually decreases. This variation in magnitude makes the heat transfer per unit length of the entire fluid flow more uniform, further improving heat transfer efficiency.

[0031] Preferably, the tube-side inlet pipe is located on the lower header; the tube-side outlet pipe is located on the upper header; the shell-side inlet is located on the upper part of the shell, and the shell-side outlet is located on the lower part of the shell.

[0032] Preferably, the heat exchange tubes are connected to the baffle plate by brazing.

[0033] As an improvement, the number of baffles per unit length decreases continuously along the height direction from the tube inlet to the middle of the tube. Then, from the middle of the tube to the tube outlet, the number of baffles per unit length increases continuously.

[0034] As an improvement, along the height direction, from the tube inlet to the middle of the tube, the rate of decrease in the number of baffles per unit length continuously increases. Then, from the middle of the tube to the tube outlet, the rate of increase in the number of baffles per unit length continuously decreases.

[0035] The technical effects of the aforementioned changes in the number of baffles are described in the previous section on the technical effects of changes in the volume of baffles.

[0036] As an improvement, such as Figure 2 As shown, the inlet header 8 is divided into left and right parts 81 and 82 by a partition 11. The left heat exchange tube is connected to the left header 81, and the right heat exchange tube is connected to the right header 82. The left header 81 and the right header 82 are respectively equipped with a left inlet 31 and a right inlet 32. The fluid flow rates of the left inlet 31 and the right inlet 32 ​​can be controlled independently, preferably by a controller. As an improvement, the fluid flow rates of the left header 81 and the right header 82 are different, thus resulting in different fluid flow rates entering the left heat exchange tube and the right heat exchange tube.

[0037] By setting up upper and lower headers, the fluid flow rates in the upper and lower headers are different. This allows the heat exchange tube with more fluid to create a greater impact on the cavity, causing the fluid in the baffle cavity to turbulent upwards or downwards, thus forming an internal circulation flow and further enhancing heat transfer.

[0038] As an improvement, in a cycle T, in 0-T / 2, the flow rate V1 of the left header tank, the right header tank flow rate V2, wherein V1 is greater than V2, so that the left side of the heat exchange tube fluid flow rate is greater than the right side of the heat exchange tube, T / 2-T, the right side of the header tank flow V1, left header tank flow V2, so that the right side of the heat exchange tube fluid flow rate is greater than the left side of the heat exchange tube. Periodic changes in the flow rate of the upper and lower header tank, so that the baffle plate fluid circulation disturbance, and the cycle disturbance periodically changes the direction of the cycle impact, so as to further strengthen the heat transfer.

[0039] As a preferred, cycle T can be 30-50 minutes.

[0040] As a preferred, V1 is 3-5 times V2.

[0041] As an improvement, the fluid into the left header tank and the right header tank is the flow velocity of the pulsatile flow, by the pulsatile flow of the baffle plate cavity fluid impact, so that the fluid is constantly disturbed.

[0042] As a preferred, in a cycle T, in 0-T / 2, the flow velocity of the left header tank is constantly increasing, from 0 to V, the right side of the header tank speed is constantly decreasing, from V to 0; in T / 2-T, the flow velocity of the right side of the header tank is constantly increasing, from 0 to V, the left side of the header tank speed is constantly decreasing, from V to 0. By the left and right header tank fluid flow rate constantly changes, so that the fluid constantly changes the disturbance direction, promote further heat transfer.

[0043] As an improvement, the pipe way inlet pipe is provided on the lower header tank; the pipe way outlet pipe is provided on the upper header tank; the shell side inlet pipe and the shell side outlet pipe are provided on the shell, and the heat exchange tube is connected to the baffle plate by brazing.

[0044] Along the direction of the upward flow of the gas, the volume of the cavity of the circular baffle plate is gradually reduced, and then gradually increased, compared with the volume of the cavity of the adjacent annular baffle plate.

[0045] In the research process, it is found that the baffle plate of the traditional heat exchanger is not uniform in cross section in the direction of the upward flow of the gas, and the heat exchange effect is good around the bottom inlet and outlet, and the heat exchange effect is good in the middle center than the surrounding edge. Along the direction of the upward flow of the gas, the area of the circular baffle plate and the volume of the cavity of the annular baffle plate change. The fluid in the shell side gradually converges to the center in the middle, so that the fluid center of the shell side heat exchange tube is strengthened, and then the heat exchange of the heat exchange tube at the top and bottom of the shell is strengthened, the heat exchange of the bottom inlet center is strengthened, and the heat exchange of the top outlet is strengthened. Change the past single heat exchange mode from top to bottom, strengthen the heat exchange efficiency at different positions, make the overall heat exchange uniform, and further achieve the purpose of strengthening heat transfer.

[0046] As a preferred, in the center position of the shell vertical direction, the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle reaches the maximum.

[0047] As an improvement, along the direction of the upward flow of the gas, the gradually decreasing range of the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle is getting larger and larger. The gradually increasing range of the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle is getting smaller and smaller. Through the change of the range, the overall heat exchange can be further made uniform, and the purpose of strengthening the heat transfer is further achieved.

[0048] As an improvement, the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle is 0.8-1.2.

[0049] Although the present application has been disclosed with reference to the preferred embodiments, the present application is not limited to the above. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and the scope of protection of the present application should be subject to the scope defined by the claims.

Claims

1. A vertical shell-and-tube heat exchanger with ring-shaped baffle, comprising a vertically arranged shell, heat exchange tubes, a tube-side inlet pipe, a tube-side outlet pipe, a shell-side inlet pipe and a shell-side outlet pipe; a plurality of parallel arranged heat exchange tubes form a heat exchange tube bundle connected to an upper tube sheet and a lower tube sheet; the upper end of the upper tube sheet is connected to an upper header, and the lower end of the lower tube sheet is connected to a lower header; a baffle is arranged in the shell, and the heat exchange tubes pass through the baffle; the baffle comprises a circular baffle located at the center of the shell and a ring-shaped baffle located around the shell, and the circular baffle and the ring-shaped baffle are arranged at intervals, characterized in that, The baffle plate is provided with a hollow cavity, each heat exchange tube is divided into multiple sections, including an upper tube section, a middle tube section and a lower tube section, wherein the upper end of the upper tube section is connected to an upper tube plate, the lower end is communicated with the cavity of the baffle plate, the lower end of the lower tube section is connected to a lower tube plate, and the upper end is communicated with the cavity of the baffle plate, and the upper end and the lower end of the middle tube section are respectively communicated with the cavities of the upper and lower baffle plates.

2. The vertical shell-and-tube heat exchanger with ring-cavity baffles of claim 1, wherein, The tube-side fluid is liquid, the shell-side fluid is gas, the gas flows from bottom to top, and the liquid flows from top to bottom.

3. The vertical shell-and-tube heat exchanger with ring-cavity baffles of claim 2, wherein, Along the flow direction of the tube-side fluid, the volume of the middle cavity of the annular baffle plate and / or the circular baffle plate continuously decreases from the tube inlet to the middle position of the tube, and then continuously increases from the middle position of the tube to the tube outlet.

4. The vertical shell-and-tube heat exchanger of the ring-cavity baffle type according to claim 3, characterized in that, Along the flow direction of the tube-side fluid, the volume of the middle cavity of the annular baffle plate and / or the circular baffle plate continuously decreases from the tube inlet to the middle position of the tube, and then continuously increases from the middle position of the tube to the tube outlet.

5. The vertical shell-and-tube heat exchanger of the annular-cavity baffle type as claimed in claim 1, characterized in that, The tube inlet is arranged on the lower header, the tube outlet is arranged on the upper header, the shell inlet is arranged on the upper part of the shell, and the shell outlet is arranged on the lower part of the shell.

6. The vertical shell-and-tube heat exchanger of the annular-cavity baffle type as claimed in claim 1, characterized in that, The heat exchange tube is connected to the baffle plate by brazing.

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