Double-inlet header vertical heat exchanger

Abstract

This invention provides a vertical heat exchanger with dual inlet headers. The lower header at the inlet is divided into a left header and a right header by a partition. The left heat exchange tube is connected to the left header, and the right heat exchange tube is connected to the right header. The left and right headers are respectively equipped with left and right inlets, and the fluid flow rates at the left and right inlets can be controlled independently. The fluid entering the left and right headers is a pulsating flow with constantly changing velocity. This invention uses the pulsating flow to continuously impact the fluid within the baffle cavity, thereby causing continuous fluid agitation and further enhancing heat transfer.

Description

Technical Field

[0001] This invention relates to a shell-and-tube heat exchanger, and more particularly to a vertical heat exchanger with an annular cavity baffle. Background Technology

[0002] Heat exchangers are indispensable equipment for heat exchange and transfer in chemical production processes. In fields such as petrochemicals, cryogenic refrigeration, air separation, and seawater desalination, it is often necessary to heat cryogenic fluids or cool high-temperature fluids, and to vaporize liquids into steam or condense steam into liquids. These processes are all closely related to heat transfer and can therefore be accomplished using heat exchangers.

[0003] Commonly used heat exchangers include shell-and-tube heat exchangers and plate heat exchangers. Traditional shell-and-tube heat exchangers mostly use smooth tubes. Compared with various new plate heat exchangers, this traditional type has many disadvantages, such as low heat transfer efficiency and large size. However, shell-and-tube heat exchangers also have many advantages, such as simple manufacturing, resistance to high temperature and pressure, and convenient maintenance. Therefore, it is urgent to develop a double-sided enhanced high-efficiency heat exchanger based on the traditional shell-and-tube heat exchanger. Currently, some high-efficiency heat exchangers based on smooth tubes have been developed in China, but their heat transfer enhancement effect is not ideal.

[0004] Currently, vertical heat exchangers are widely used in energy, power, chemical, metallurgical, and environmental protection industries, making them a very common type of heat exchange equipment. They hold a significant position in the heat exchanger market due to their advantages such as small footprint, ease of manufacturing, low cost, strong adaptability, large throughput, reliable operation, wide range of material selection, and suitability for high-temperature and high-pressure conditions. Existing vertical heat exchangers mainly employ two types of baffle structures: arc-shaped baffles and spiral baffles. While traditional vertical heat exchangers with arc-shaped baffles offer the advantages of vertical heat exchangers, they also have some drawbacks, such as dead zones in the shell side, significant shell-side pressure loss, susceptibility to fouling, and a tendency for tube bundle-induced vibration. Traditional vertical heat exchangers with spiral baffles, while providing a more rational flow pattern for the shell-side fluid, increasing the effective flow area, and reducing flow resistance, suffer from complex baffle arrangement, making baffle manufacturing more complicated, heat tube installation more difficult, and compromising product precision. Furthermore, the overall rigidity of the tube bundle is relatively poor. In addition, the triangular space unique to spiral baffle heat exchangers results in a large number of short-circuit flows, which leads to a significant decrease in their heat exchange efficiency.

[0005] Currently, existing technologies typically employ separate upper or lower headers, where the fluids are mixed together without differentiation based on specific conditions. Furthermore, the heat exchange tubes are all connected to a single inlet header. Therefore, improvements are needed to enhance the heat exchange performance of these technologies.

[0006] Therefore, improvements are needed to the vertical heat exchanger, especially to the inlet header and baffles, in order to further improve the heat exchange efficiency. Summary of the Invention

[0007] To overcome the defects and shortcomings of existing technologies, this invention provides a vertical heat exchanger with dual inlet headers. The baffles are configured as hollow cavities, which increase the contact area between the two fluids and the heat exchange area. Different pulsating flows from different headers continuously impact the fluids inside the baffle cavities, causing continuous fluid disturbance and further enhancing heat transfer. This can improve the convective heat transfer coefficient of the heat exchanger shell side, thereby effectively improving the heat transfer efficiency.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A dual-header vertical heat exchanger, comprising a shell-and-tube heat exchanger including a vertically arranged shell, heat exchange tubes, tube-side inlet tubes, tube-side outlet tubes, shell-side inlet pipes, and shell-side outlet pipes; a heat exchange tube bundle consisting of multiple parallel heat exchange tubes 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, and the lower end of the lower tube sheet is connected to a lower header; the lower header at the inlet is divided into a left header and a right header by a partition, wherein the left heat exchange tubes are connected to the left header, and the right heat exchange tubes are connected to the right header; the left header and the right header are respectively provided with a left inlet and a right inlet, and the fluid flow rates of the left inlet and the right inlet can be controlled independently.

[0010] As an improvement, the fluid entering the left and right headers is a pulsating flow with constantly changing velocity. The pulsating flow continuously impacts the fluid inside the baffle cavity, thus causing continuous disturbance to the fluid.

[0011] As an improvement, within a cycle T, from 0 to T / 2, the flow velocity of the left container continuously increases from 0 to V, while the velocity of the right container continuously decreases from V to 0; within T / 2 to T, the flow velocity of the right container continuously increases from 0 to V, while the velocity of the left container continuously decreases from V to 0.

[0012] As an improvement, within 0-T / 2, the rate of increase in the flow velocity of the left header continuously increases, while the rate of decrease in the velocity of the right header continuously increases.

[0013] As an improvement, within T / 2-T, the rate of increase in the flow velocity of the right-side header continuously increases, while the rate of decrease in the velocity of the left-side header continuously increases.

[0014] As an improvement, the period T can be 30-50 minutes.

[0015] As an improvement, a baffle plate is provided inside the shell, and the heat exchange tube passes through the baffle plate; the baffle plate includes a circular baffle plate located at the center of the shell and an annular baffle plate located around the shell, with the circular baffle plate and the annular baffle plate spaced apart, characterized in that the baffle plate is provided with 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, wherein the upper end of the upper tube segment is connected to the upper tube sheet and the lower end is connected to the cavity of the baffle plate, the lower end of the lower tube segment is connected to the lower tube sheet and the upper end is connected to the cavity of the baffle plate, and the upper and lower ends of the middle tube segment are respectively connected to the cavities of the upper and lower baffle plates.

[0016] As an improvement, the tube-side fluid is a liquid, and the shell-side fluid is a gas, with the gas flowing from bottom to top and the liquid flowing from top to bottom.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1) This invention divides the inlet header into two parts, with the fluid entering the left and right headers being a pulsating flow with constantly changing velocity. This pulsating flow continuously impacts the fluid within the baffle cavity, causing constant fluid agitation. The continuous changes in fluid velocity between the left and right headers further promote heat transfer by altering the direction of the agitation.

[0019] 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

[0020] Figure 1 This is a schematic diagram of the shell-and-tube heat exchanger structure with hollow cavity baffles according to the present invention;

[0021] Figure 2 This is a schematic diagram of the improved shell-and-tube heat exchanger of the present invention;

[0022] Figure 3 Schematic diagram of the annular baffle structure of the present invention;

[0023] Figure 4 This is a schematic diagram of the circular baffle structure of the present invention. Detailed Implementation

[0024] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] Unless otherwise specified, in this article, " / " represents division, and "×" and "*" represent multiplication.

[0026] 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.

[0027] 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. As an improvement, the baffle is provided with a hollow cavity. Each heat exchange tube is divided into multiple sections, including an upper tube section 21, a middle tube section 22 and a lower tube section 23. The upper tube section 21 is connected to the upper tube sheet at the upper end and to the cavity of the baffle at the lower end. The lower tube section 23 is connected to the lower tube sheet at the lower end and to the cavity of the baffle at the upper end. The upper and lower ends of the middle tube section 22 are connected to the cavities of the upper and lower baffles, respectively.

[0028] This invention configures the baffle as 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. Simultaneously, because the cavity increases the flow space in the tube side, it further reduces flow resistance.

[0029] As an improvement, such as Figure 1 As shown, the cavity within the baffle is a continuous, interconnected cavity, thus ensuring that the heat exchange tubes within this interconnected cavity are also interconnected. For example... Figure 1 The baffle plate forms a cavity in the horizontal direction, and all the heat exchange tubes are connected to this cavity, thus ensuring that the heat exchange tubes within the connected cavity are also interconnected. This interconnected cavity allows for a redistribution of the fluid pressure inside the heat exchange tubes, resulting in a more balanced internal fluid pressure and further improving the heat exchange efficiency.

[0030] Preferably, the tube-side fluid is a liquid, and the shell-side fluid is a gas, with the gas flowing from bottom to top and the liquid flowing from top to bottom.

[0031] Preferably, along the flow direction of the gas in the tube, from the tube inlet to the middle position of the tube, the volume (or height) of the cavity of the annular baffle and / or circular baffle continuously decreases, and then from the middle position of the tube to the tube outlet, the volume (or height) of the cavity of the annular baffle and / or circular baffle continuously increases.

[0032] Because during counter-current flow, the heat transfer per unit length along the fluid flow path is relatively uniform in both the shell and tube sides, resulting in the best overall heat transfer effect. However, experiments and simulations have shown that the heat transfer in the middle section is significantly greater than that at the tube inlet and outlet. Therefore, by changing the volume of the middle cavity, the heat transfer area between the tube-side and shell-side fluids within the middle cavity also changes. This heat transfer area increases and decreases with increasing and decreasing volume, thus compensating for the uneven heat transfer through area variation, thereby further improving heat transfer efficiency.

[0033] 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.

[0034] 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.

[0035] Preferably, the heat exchange tubes are connected to the baffle plate by brazing.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] As an improvement, such as Figure 2As 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.

[0040] 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.

[0041] As an improvement, within a cycle T, from 0 to T / 2, the flow rate V1 in the left header and V2 in the right header, where V1 is greater than V2, results in a higher fluid velocity in the left heat exchanger tube than in the right heat exchanger tube. From T / 2 to T, the flow rate V1 in the right header and V2 in the left header, again results in a higher fluid velocity in the right heat exchanger tube than in the left heat exchanger tube. Periodically changing the fluid flow rates in the upper and lower headers creates circulating disturbances in the baffles, and these disturbances periodically change the direction of the circulating impact, further enhancing heat transfer.

[0042] Preferably, the period T can be 30-50 minutes.

[0043] As a preferred option, V1 is 3-5 times that of V2.

[0044] As an improvement, the fluid entering the left and right headers is a pulsating flow with constantly changing velocity. The pulsating flow continuously impacts the fluid inside the baffle cavity, thus causing continuous disturbance to the fluid.

[0045] Preferably, within a period T, from 0 to T / 2, the flow velocity in the left header continuously increases from 0 to V, while the velocity in the right header continuously decreases from V to 0; from T / 2 to T, the flow velocity in the right header continuously increases from 0 to V, while the velocity in the left header continuously decreases from V to 0. This continuous change in fluid velocity between the left and right headers causes a constant change in the direction of fluid disturbance, promoting further heat transfer.

[0046] As an improvement, within the range of 0-T / 2, the rate of increase in the flow velocity in the left header continuously increases, while the rate of decrease in the velocity in the right header continuously increases. As an improvement, within the range of T / 2-T, the rate of increase in the flow velocity in the right header continuously increases, while the rate of decrease in the velocity in the left header continuously increases. By continuously varying the flow velocities in the left and right headers, heat transfer can be further enhanced.

[0047] As an improvement, 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 pipe and shell-side outlet pipe are both located on the shell, and the heat exchange tubes are connected to the baffles by brazing.

[0048] Along the upward flow direction of the gas, the ratio of the volume of the cavity of the circular baffle to the volume of the cavity of the adjacent annular baffle gradually decreases first, and then gradually increases.

[0049] During the research, it was found that the baffles in traditional heat exchangers exhibit uneven heat transfer across their cross-section in the upward gas flow direction. The heat transfer is better around the bottom inlet and outlet, and better at the center than at the edges. This invention changes the ratio of the area of ​​the circular baffle to the volume of the annular baffle along the upward gas flow direction. This causes the fluid in the shell-side to gradually move towards the center, enhancing heat transfer in the heat exchange tubes around the fluid center, then further enhancing heat transfer in the heat exchange tubes at the top and bottom of the shell, and strengthening heat transfer at the bottom inlet center and top outlet. This changes the previous top-to-bottom single heat transfer method, enhancing heat transfer efficiency at different locations, resulting in overall uniform heat transfer and further achieving the goal of enhanced heat transfer.

[0050] Preferably, at the center position of the shell in the vertical direction, the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle reaches its maximum.

[0051] As an improvement, along the upward flow direction of the gas, the ratio of the volume of the circular baffle cavity to that of the adjacent annular baffle gradually decreases with increasing amplitude. Conversely, the ratio of the volume of the circular baffle cavity to that of the adjacent annular baffle gradually increases with decreasing amplitude. Through these variations in amplitude, the overall heat transfer can be further made more uniform, thus further enhancing the heat transfer effect.

[0052] As an improvement, the ratio of the volume of the circular baffle cavity to the volume of the cavity of the adjacent annular baffle is 0.8-1.2.

[0053] While the present invention has been disclosed above with reference to preferred embodiments, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A vertical shell-and-tube heat exchanger with dual inlet headers, the shell-and-tube heat exchanger comprising a vertically arranged shell, heat exchange tubes, tube-side inlet pipes, tube-side outlet pipes, shell-side inlet pipes, and shell-side outlet pipes; a heat exchange tube bundle consisting of multiple parallel heat exchange tubes 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; the lower header at the inlet is divided into a left header and a right header by a partition, wherein the left heat exchange tubes are connected to the left header, and the right heat exchange tubes are connected to the right header; the left header and the right header are respectively provided with a left inlet and a right inlet, and the fluid flow rates of the left inlet and the right inlet can be controlled independently; baffles are provided inside the shell, and the heat exchange tubes pass through the baffles; the baffles include a circular baffle located at the center of the shell and an annular baffle located around the shell, and the circular baffle and the annular baffle are connected between... The baffle plate is configured with a hollow cavity. Each heat exchange tube is divided into multiple sections, including an upper section, a middle section, and a lower section. The upper section is connected to the upper tube sheet at its upper end and to the cavity of the baffle plate at its lower end. The lower section is connected to the lower tube sheet at its lower end and to the cavity of the baffle plate at its upper end. The middle section is connected to the cavities of the upper and lower baffle plates at its upper and lower ends, respectively. The fluid entering the left and right headers is a pulsating flow with constantly changing velocity. This pulsating flow continuously impacts the fluid within the cavity of the baffle plate, causing continuous fluid disturbance. Within one cycle T, from 0 to T / 2, the flow velocity in the left header continuously increases from 0 to V, while the velocity in the right header continuously decreases from V to 0. From T / 2 to T, the flow velocity in the right header continuously increases from 0 to V, while the velocity in the left header continuously decreases from V to 0.

2. The shell-and-tube heat exchanger as described in claim 1, characterized in that, Within 0-T / 2, the flow velocity of the left-side header continuously increases, while the velocity of the right-side header continuously decreases.

3. The shell-and-tube heat exchanger as described in claim 1, characterized in that, Within T / 2-T, the rate of increase in the flow velocity of the right-side header continuously increases, while the rate of decrease in the velocity of the left-side header continuously increases.

4. The shell-and-tube heat exchanger as described in claim 1, characterized in that, The cycle T is 30-50 minutes.

5. The shell-and-tube heat exchanger as described in claim 1, characterized in that, The tube-side fluid is liquid, and the shell-side fluid is gas. Gas flows from bottom to top, while liquid flows from top to bottom.

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