Vertical heat exchanger with double inlet headers

Abstract

A lower header of an inlet is divided into a left header and a right header through a partition plate, a left heat exchange tube is communicated with the left header, a right heat exchange tube is communicated with the right header, and the left header and the right header are provided with a left inlet and a right inlet respectively. The fluid flow of the left inlet and the right inlet can be independently controlled, and the fluid entering the left header and the right header is pulsating flow with continuously changing flowing speed. The pulsating flow continuously impacts the fluid in the cavity of the baffle plate, so that the fluid is continuously disturbed, and heat transfer is further enhanced.

Description

Technical Field

[0001] The invention relates to a shell and tube heat exchanger, in particular to a vertical heat exchanger with an annular cavity baffle. Background Art

[0002] Heat exchangers are indispensable equipment for heat exchange and transfer in chemical production. In the fields of petrochemicals, cryogenic refrigeration, air separation, seawater desalination, etc., it is often necessary to heat low-temperature fluids or cool high-temperature fluids, vaporize liquids into steam, or condense steam into liquids. These processes are closely related to heat transfer, and can therefore be completed through 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 as heat exchanger tubes. This traditional shell and tube heat exchanger has many disadvantages compared with various new plate heat exchangers, such as low heat transfer efficiency and large heat exchanger volume; however, shell and tube heat exchangers also have many advantages of their own, such as simple manufacturing, high temperature and high pressure resistance, and easy maintenance. Therefore, it is urgent to develop a double-sided enhanced high-efficiency heat exchanger based on the traditional shell and tube heat exchanger. At present, some high-efficiency heat exchangers based on smooth tubes have appeared in China for secondary development, but they are not ideal in terms of enhanced heat transfer effect.

[0004] At present, vertical heat exchangers are widely used in industrial fields such as energy, power, chemical industry, metallurgy, and environmental protection. They are a very common heat exchange equipment. At the same time, due to the characteristics of small footprint, easy manufacturing, low cost, strong adaptability, large processing capacity, reliable operation, wide range of material selection, and suitable for high temperature and high pressure conditions, vertical heat exchangers occupy a certain position in the field of heat exchanger use. The baffle structure of the existing vertical heat exchanger mainly includes two types: arched baffles and spiral baffles. Among them, the traditional vertical heat exchanger with arched baffles, while having the advantages of vertical heat exchangers, also has some defects, such as shell-side flow dead zone, large shell-side pressure loss, easy scaling, and easy tube bundle induced vibration. Although the traditional vertical heat exchanger with spiral baffles makes the flow form of the shell-side fluid more reasonable, increases the effective flow area, and reduces the flow resistance, due to the complex arrangement of the spiral baffles, the processing process of the baffles is relatively complicated, the installation process of the heat exchange tube is also very difficult, the accuracy 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 heat exchanger causes a large amount of short-circuit flow, resulting in a significant decrease in its heat exchange efficiency.

[0005] At present, the existing technology adopts the upper header or the lower header separately, and the fluids in the header are mixed together without being distinguished according to the specific situation. The heat exchange tubes are also connected to an inlet header. Therefore, it can be improved to improve its heat exchange performance.

[0006] Therefore, it is necessary to improve the vertical heat exchanger, especially the inlet header and baffle, in order to further improve the heat exchange efficiency. Summary of the invention

[0007] In order to overcome the defects and shortcomings in the prior art, the present invention provides a vertical heat exchanger with double inlet headers, in which the baffle is set as a hollow cavity, and the contact area between the two fluids is increased through the cavity, thereby increasing the heat exchange area. Different pulsating flows from different headers continuously impact the fluid in the baffle cavity, thereby causing the fluid to be continuously disturbed, further enhancing heat transfer and improving the convective heat transfer coefficient of the shell side of the heat exchanger, thereby effectively improving the heat transfer efficiency.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows: A double-header vertical heat exchanger, the shell and tube heat exchanger includes 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 composed 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 the upper header, and the lower end of the lower tube sheet is connected to the lower header; the inlet lower header is divided into a left header and a right header by a partition, wherein 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 header and the right header are respectively provided with a left inlet and a right inlet, and the fluid flow of the left inlet and the right inlet can be controlled separately.

[0009] As an improvement, the fluid entering the left and right headers is a pulsating flow with a constantly changing flow velocity. The pulsating flow continuously impacts the fluid in the cavity of the baffle, thereby causing the fluid to be constantly disturbed.

[0010] As an improvement, within a cycle T, 0-T / 2, the flow velocity of the left header continues to increase from 0 to V, and the velocity of the right header continues to decrease from V to 0; within T / 2-T, the flow velocity of the right header continues to increase from 0 to V, and the velocity of the left header continues to decrease from V to 0.

[0011] As an improvement, within 0-T / 2, the flow velocity of the left header increases continuously and the velocity of the right header decreases continuously and the velocity of the right header decreases continuously and the velocity of the left header decreases ... right header decreases continuously and the velocity of the right header decreases continuously and the velocity of the right

[0012] As an improvement, within T / 2-T, the flow velocity of the right header increases at an increasing rate, while the velocity of the left header decreases at an increasing rate.

[0013] As an improvement, the period T may be 30-50 minutes.

[0014] As an improvement, a baffle is arranged in the shell, and the heat exchange tube passes through the baffle; the baffle includes 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 arranged at intervals, and is characterized in that the baffle is provided with a hollow cavity, and 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 the upper tube plate, and the lower end is connected to the cavity of the baffle, the lower end of the lower tube section is connected to the lower tube plate, and the upper end is connected to the cavity of the baffle, and the upper and lower ends of the middle tube section are respectively connected to the cavities of the upper and lower baffles.

[0015] As an improvement, 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.

[0016] Compared with the prior art, the present invention has the following advantages: 1) The present invention divides the inlet header into two parts by setting. The fluid entering the left header and the right header is a pulsating flow with a constantly changing flow velocity. The pulsating flow constantly impacts the fluid in the cavity of the baffle, thereby causing the fluid to be constantly disturbed. The fluid passing through the left and right headers constantly changes its flow velocity, thereby causing the fluid to constantly change its disturbance direction, thereby promoting further heat exchange; 2) The heat transfer area of ​​the baffle cavity is continuously changed along the height direction of the fluid flow, which further enhances the heat transfer and improves the overall heat transfer efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a shell and tube heat exchanger provided with a hollow cavity baffle according to the present invention; Figure 2 is a schematic diagram of an improved shell and tube heat exchanger of the present invention; Figure 3 A schematic diagram of the structure of the annular baffle of the present invention; Figure 4 It is a schematic diagram of the circular baffle structure of the present invention. DETAILED DESCRIPTION

[0018] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0019] In this article, unless otherwise specified, “ / ” represents division, and “×” and “*” represent multiplication.

[0020] It should be noted that, unless otherwise specified, the two-phase flow mentioned in the present invention is a gas-liquid two-phase flow, where the gas is an insoluble or poorly soluble gas, that is, during the heat exchange process, the gas will not dissolve in the liquid.

[0021] Figure 1 The shell and tube heat exchanger with a vertically arranged annular cavity baffle of the present application is shown, and the shell and tube heat exchanger includes a vertically arranged shell 1, a heat exchange tube 2, a tube side inlet tube 3, a tube side outlet tube 4, a shell side inlet pipe 5 and a shell side outlet pipe 6; a heat exchange tube bundle composed of a plurality of 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 is arranged in the shell 1, and the heat exchange tube 2 passes through the baffle; the baffle includes a circular baffle 9 located in the center of the shell (for specific structure, see Figure 4 ) and an annular baffle 10 located around the shell (for specific structure, see 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, wherein the upper end of the upper tube section 21 is connected to the upper tube plate, and the lower end is connected to the cavity of the baffle, the lower end of the lower tube section 23 is connected to the lower tube plate, and the upper end is connected to the cavity of the baffle, and the upper and lower ends of the middle tube section 22 are respectively connected to the cavities of the upper and lower baffles.

[0022] The present invention sets the baffle as a cavity, so that the baffle can be filled with tube-side fluid, increasing the heat exchange area between the tube-side fluid and the shell-side fluid, further enhancing heat transfer. At the same time, because the cavity of the present invention increases the flow space of the tube side, the flow resistance is further reduced.

[0023] As an improvement, Figure 1 As shown, the cavity in the baffle is a whole continuous connected cavity, so that the heat exchange tubes connected to the cavity are also connected to each other. Figure 1 The middle baffle is a cavity in the horizontal direction, and the heat exchange tubes are connected to the baffle cavity, so that the heat exchange tubes connected to the cavity are also connected to each other. Through the above-mentioned overall connected cavity, the fluid pressure inside the heat exchange tube can be redistributed, so that the internal fluid pressure is balanced, further improving the heat exchange effect.

[0024] Preferably, 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.

[0025] Preferably, along the flow direction of the gas in the tube, the volume (or height) of the cavity of the annular baffle and / or the circular baffle continuously decreases from the tube inlet to the middle position of the tube, and then the volume (or height) of the cavity of the annular baffle and / or the circular baffle continuously increases from the middle position of the tube to the tube outlet.

[0026] Because in the countercurrent process, the heat exchange of the shell side and the tube side per unit length along the flow process of the fluid is relatively uniform, so that the overall heat exchange effect is the best. However, in experiments and simulations, it is found that the heat exchange in the middle is significantly greater than the heat exchange at the inlet and outlet of the tube side. Therefore, the volume change of the middle cavity causes the heat exchange area between the tube side fluid and the shell side fluid in the middle cavity to change. The heat exchange area also increases and decreases with the increase and decrease of the volume. Therefore, the uneven heat exchange is compensated by the change of the area, thereby further improving the heat exchange efficiency.

[0027] Preferably, along the flow direction of the gas in the tube, from the tube entrance to the middle of the tube, the volume (or height) of the middle cavity of the annular baffle and / or circular baffle is continuously reduced and the amplitude is continuously increased, and then from the middle of the tube to the tube exit, the volume (or height) of the middle cavity of the annular baffle and / or circular baffle is continuously increased and the amplitude is continuously reduced. The above amplitude change can make the heat exchange per unit length of the entire fluid movement more uniform, and further improve the heat exchange efficiency.

[0028] Preferably, the tube-side inlet pipe is arranged on the lower header; the tube-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.

[0029] Preferably, the heat exchange tubes are connected to the baffles by brazing.

[0030] As an improvement, along the height direction, from the tube entrance to the middle of the tube, the number of baffles distributed per unit length decreases continuously, and then from the middle of the tube to the tube exit, the number of baffles distributed per unit length increases continuously.

[0031] As an improvement, along the height direction, from the tube inlet to the middle of the tube, the number of baffles distributed per unit length decreases and the amplitude increases. Then, from the middle of the tube to the tube outlet, the number of baffles distributed per unit length increases and the amplitude decreases.

[0032] The technical effect of the change in the number of baffle distribution mentioned above can be referred to the technical effect of the change in the volume of the baffle mentioned above.

[0033] As an improvement, Figure 2As shown, the inlet header 8 is divided into two parts 81 and 82 by a partition 11, wherein 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 provided with a left inlet 31 and a right inlet 32, and the fluid flow of the left inlet 31 and the right inlet 32 ​​can be controlled separately, preferably by a controller. As an improvement, the fluid flow of the left header 81 and the right header 82 is different, so that the fluid flow entering the left heat exchange tube and the right heat exchange tube is different.

[0034] By setting up upper and lower headers, the fluid flow rates in the upper and lower headers are different, so that the heat exchange tubes with more fluid can have a greater impact on the inside of the cavity, causing the fluid in the baffle cavity to form an upward or downward disturbance, thereby forming a circulating flow inside and further enhancing heat transfer.

[0035] As an improvement, within a cycle T, within 0-T / 2, the flow rate of the left header is V1, and the flow rate of the right header is V2, where V1 is greater than V2, so that the fluid flow rate in the left heat exchange tube is greater than that in the right heat exchange tube, and within T / 2-T, the flow rate of the right header is V1, and the flow rate of the left header is V2, so that the fluid flow rate in the right heat exchange tube is greater than that in the left heat exchange tube. The fluid flow rates of the upper and lower headers are changed regularly, so that the fluid of the baffle forms a cyclic disturbance, and the cyclic disturbance regularly changes the cyclic impact direction, thereby further enhancing heat transfer.

[0036] Preferably, the period T may be 30-50 minutes.

[0037] Preferably, V1 is 3-5 times greater than V2.

[0038] As an improvement, the fluid entering the left and right headers is a pulsating flow with a constantly changing flow velocity. The pulsating flow continuously impacts the fluid in the cavity of the baffle, thereby causing the fluid to be constantly disturbed.

[0039] Preferably, within a period T, within 0-T / 2, the flow velocity of the left header increases continuously from 0 to V, and the velocity of the right header decreases continuously from V to 0; within T / 2-T, the flow velocity of the right header increases continuously from 0 to V, and the velocity of the left header decreases continuously from V to 0. The fluids passing through the left and right headers continuously change their flow velocities, thereby causing the fluids to continuously change their disturbance directions, thereby promoting further heat exchange.

[0040] As an improvement, within 0-T / 2, the flow velocity of the left header increases continuously, and the velocity of the right header decreases continuously. As an improvement, within T / 2-T, the flow velocity of the right header increases continuously, and the velocity of the left header decreases continuously. By continuously changing the amplitude of the flow velocity of the fluid in the left and right headers, the enhanced heat exchange can be further promoted.

[0041] As an improvement, the tube-side inlet pipe is arranged on the lower header; the tube-side outlet pipe is arranged on the upper header; the shell-side inlet pipe and the shell-side outlet pipe are both arranged on the shell, and the heat exchange tube is connected to the baffle by brazing.

[0042] 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 first gradually decreases and then gradually increases.

[0043] During the research process, it was found that the heat transfer of the baffles of the traditional heat exchanger is uneven in the cross-section in the direction of gas upward flow, and the heat transfer effect is better in the parts around the bottom inlet and outlet, and the heat transfer effect is better in the middle center than in the surrounding edges. In the present invention, the area of ​​the circular baffle and the cavity volume ratio of the annular baffle change along the upward flow direction of the gas. The fluid in the shell side gradually moves closer to the center in the middle, so that the heat exchange tubes around the shell at the center of the fluid strengthen the heat exchange, and then the heat exchange tubes in the center of the shell at the upper and lower ends strengthen the heat exchange, strengthening the heat exchange at the bottom inlet center and the top outlet. It changes the previous single heat exchange method from top to bottom, strengthens the heat exchange efficiency at different positions, makes the heat exchange uniform on the whole, and further achieves the purpose of strengthening heat transfer.

[0044] Preferably, at the center position in the vertical direction of the shell, the ratio of the cavity volume of the circular baffle plate to the cavity volume of the adjacent annular baffle plate reaches a maximum.

[0045] As an improvement, along the upward flow direction of the gas, the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle gradually decreases and the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle gradually increases and the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle gradually increases and the ratio of the cavity volume of the circular baffle to the cavity volume of the adjacent annular baffle gradually increases and the ratio of the cavity volume of the circular baffle increases and the ratio of ...

[0046] 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.

[0047] Although the present invention has been disclosed as above with preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A vertical heat exchanger with double inlet headers, the shell and tube heat exchanger comprising 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 composed of a plurality of 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 inlet lower header is divided into a left header and a right header by a partition, wherein 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 header and the right header are respectively provided with a left inlet and a right inlet, and the fluid flow of the left inlet and the right inlet can be controlled separately.

2. The vertical heat exchanger with annular cavity baffles according to claim 1, characterized in that: The fluid entering the left and right headers is a pulsating flow with a constantly changing flow velocity. The pulsating flow continuously impacts the fluid in the cavity of the baffle, thereby causing the fluid to be constantly disturbed.

3. The vertical heat exchanger with annular cavity baffles according to claim 2, characterized in that: Within a cycle T, within 0-T / 2, the flow velocity of the left header continues to increase from 0 to V, and the velocity of the right header continues to decrease from V to 0; within T / 2-T, the flow velocity of the right header continues to increase from 0 to V, and the velocity of the left header continues to decrease from V to 0.

4. The vertical heat exchanger with an annular cavity baffle as claimed in claim 3, characterized in that: Within 0-T / 2, the flow velocity of the left header increases continuously at an increasing rate, while the velocity of the right header decreases continuously at an increasing rate.

5. The vertical heat exchanger with annular cavity baffles according to claim 3, characterized in that: Within T / 2-T, the flow velocity of the right header increases continuously and the velocity of the left header decreases ...

6. The vertical heat exchanger with annular cavity baffles according to claim 2, characterized in that: The period T may be 30-50 minutes.

7. The vertical heat exchanger with annular cavity baffles according to claim 1, characterized in that: A baffle is arranged in the shell, and the heat exchange tube passes through the baffle; the baffle includes 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 arranged at intervals, and is characterized in that the baffle is provided with a hollow cavity, and 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 the upper tube plate, and the lower end is connected to the cavity of the baffle, the lower end of the lower tube section is connected to the lower tube plate, and the upper end is connected to the cavity of the baffle, and the upper and lower ends of the middle tube section are respectively connected to the cavities of the upper and lower baffles.

8. The vertical heat exchanger with annular cavity baffles according to claim 1, characterized in that: 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.

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