A horizontal shell and tube heat exchanger for shell-side gas

Abstract

The present invention provides a horizontal shell-and-tube heat exchanger for shell-side gas, the shell-and-tube heat exchanger comprises a shell and tube, a heat exchange tube, a shell-side inlet pipe and a shell-side outlet pipe; the shell-side inlet pipe and the shell-side outlet pipe are respectively located at two ends of the heat exchanger; the heat exchange tube is arranged in the shell and tube, and the heat exchange tube is fixedly connected to the tube sheet; the fluid in the shell is gas, and a plurality of baffle groups are arranged in the shell and tube, and the baffle group comprises a lower baffle located at the lower part of the shell and tube and an upper baffle located at the upper part of the shell and tube; along the flow direction of the gas in the shell, the area ratio of the lower baffle in the baffle group to the upper baffle is gradually reduced. The present invention can improve the local heat exchange coefficient and further enhance the heat transfer by changing the change of the area of ​​the upper baffle and the lower baffle.

Description

Technical Field

[0001] The invention relates to a shell and tube heat exchanger, in particular to a horizontal shell and tube heat exchanger. Background Art

[0002] Shell and tube heat exchangers are widely used in industries such as chemical, petroleum, refrigeration, nuclear energy and power. Due to the global energy crisis, in order to reduce energy consumption, the demand for heat exchangers in industrial production is increasing, and the quality requirements for heat exchangers are also getting higher and higher. In recent decades, although compact heat exchangers (plate, plate-fin, press-welded plate heat exchangers, etc.), heat pipe heat exchangers, direct contact heat exchangers, etc. have developed rapidly, shell and tube heat exchangers still dominate production and usage due to their high reliability and wide adaptability. According to relevant statistics, the use of shell and tube heat exchangers in industrial devices still accounts for about 70% of all heat exchangers.

[0003] For medium and high pressure, toxic, flammable gas and liquid or phase change heat transfer occasions, the gas side needs to be pressurized or sealed. In this case, shell and tube heat exchangers are widely used, especially horizontal shell and tube heat exchangers. Most of these horizontal shell and tube heat exchangers use enhanced heat transfer tubes with micro ribs, corrugated tubes, spiral tubes, etc. to enhance heat transfer. For gas and liquid or phase change occasions, the heat transfer coefficient between the gas side and the other side is very different, often reaching more than 100 times. The surface expansion rate of heat transfer tubes such as micro ribs, corrugated tubes, spiral tubes, etc. is low, and the heat exchangers on both sides cannot be effectively brought closer. At this time, the use of finned tubes is a very effective means.

[0004] In a shell and tube heat exchanger, heat exchange tubes and baffles or baffle rods together constitute the shell-side flow channel. Heat exchange tubes are basic heat transfer elements. The function of baffles is to change the flow direction of shell-side fluids so that the cold and hot media can fully exchange heat. At the same time, they play the role of supporting the tube bundle to prevent damage caused by fluid-induced vibration of the tube bundle. For a long time, the shell-side fluid flow and heat transfer characteristics of shell and tube heat exchangers have been a hot topic and difficulty in research. The traditional baffle form in the heat exchanger is the bow baffle. The bow baffle heat exchanger has the characteristics of high heat transfer coefficient and simple manufacturing and assembly. Due to the frequent changes in the flow direction of the shell-side fluid, it flows in a Z-shaped shape, but it also causes the shell-side fluid pressure loss to be high, the pump power load consumption is large, and there is a flow dead zone. At the same time, the fluid between the adjacent baffles in the shell side vertically scours the tube bundle, and the fluid induces the vibration and damage of the tube bundle, affecting the safe operation of the heat exchanger equipment.

[0005] However, the traditional baffle heat exchanger also has some shortcomings, such as large flow resistance, a large number of flow dead zones, low heat transfer efficiency, etc. Therefore, under the new energy conservation and emission reduction situation, its development is greatly restricted. Therefore, in view of these shortcomings, a baffle and shell and tube heat exchanger with simple structure and mature technology is developed to effectively improve its heat exchange area and heat exchange efficiency, which is of great significance to industrial production and energy conservation and emission reduction. Summary of the invention

[0006] In order to overcome the defects and shortcomings in the prior art, the present invention provides a shell and tube heat exchanger with a new layout of baffles, which can improve the convective heat transfer coefficient of the shell side of the heat exchanger, thereby effectively improving the heat transfer efficiency.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] A horizontal shell and tube heat exchanger, comprising a shell and tube, heat exchange tubes, a shell-side inlet pipe and a shell-side outlet pipe; the shell-side inlet pipe and the shell-side outlet pipe are respectively located at two ends of the heat exchanger; the heat exchange tubes are arranged in the shell and tube, and the heat exchange tubes are fixedly connected to the tube sheet; it is characterized in that the fluid in the shell is gas, a plurality of baffle groups are arranged in the shell and tube, the baffle group comprises a lower baffle located at the lower part of the shell and tube, and an upper baffle located at the upper part of the shell and tube; along the flow direction of the gas in the shell, the area ratio of the lower baffle in the baffle group to the upper baffle in the baffle group gradually decreases.

[0009] As an improvement, along the flow direction of the gas in the shell side, the ratio of the area of ​​the lower baffle plate to the area of ​​the upper baffle plate in the baffle plate group gradually decreases.

[0010] As an improvement, the sum of the projected areas of the lower baffle and the upper baffle of the baffle group on the shell cross section is 140-180% of the shell cross section area.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1) In the present invention, the area ratio of the lower baffle to the upper baffle in the baffle group changes along the flow direction of the gas, so that the gas in the shell can be closer to the center, so that the center of the fluid is around the heat exchange tube of the shell to strengthen the heat exchange, avoid the problem that the upper heat exchange effect is greater than the lower part due to the rise of the gas, strengthen the heat exchange efficiency at different positions, make the heat exchange uniform as a whole, and further achieve the purpose of strengthening heat transfer.

[0013] 2) By changing the spacing between the baffles, the heat exchange area between the tube-side fluid and the shell-side fluid in the baffles also changes. Therefore, the uneven heat exchange amount is compensated by the change in area, thereby further improving the heat exchange efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of a shell and tube heat exchanger of the prior art;

[0015] Figure 2 It is a schematic diagram of the heat exchange tube structure of the shell and tube heat exchanger of the horizontal baffle group arranged in the present invention. DETAILED DESCRIPTION

[0016] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0017] In this article, unless otherwise specified, “ / ” represents division, and “×” and “*” represent multiplication.

[0018] It should be noted that, unless otherwise specified, the gas here is an insoluble or poorly soluble gas, that is, the gas will not dissolve in the liquid during the heat exchange process.

[0019] A horizontal shell and tube heat exchanger, such as Figure 1 As shown, the shell and tube heat exchanger is arranged horizontally, including a tube shell 1, a heat exchange tube 8, a shell-side inlet pipe 2 and a shell-side outlet pipe 3; the shell-side inlet pipe 2 and the shell-side outlet pipe 3 are respectively located on the left side of the upper end and the right side of the lower end of the tube shell 1; the heat exchange tube 8 is arranged in the tube shell 1, and the heat exchange tube is fixedly connected to the left tube sheet and the right tube sheet; the front end of the left tube sheet is connected to the left header 4, and the rear end of the right tube sheet is connected to the right header 5; the tube-side outlet pipe 10 is arranged on the left header 4; the tube-side inlet pipe 9 is arranged on the right header 5; the shell-side inlet pipe 2 and the shell-side outlet pipe 3 are both arranged on the tube shell 1; the gas enters from the shell-side inlet pipe 2, exchanges heat through the heat exchange tubes, and exits from the shell-side outlet pipe 3.

[0020] The fluid in the shell side is gas. Figure 2 As shown, a plurality of baffle groups 11 are arranged in the tube shell, and the baffle group 11 includes a lower baffle 111 located at the lower part of the tube shell and an upper baffle 112 located at the upper part of the tube shell; as an improvement, the area of ​​the lower baffle 111 is V1, and the area of ​​the upper baffle is V2, and along the flow direction of the gas in the shell, the ratio V1 / V2 of the area of ​​the lower baffle 111 in the baffle group to the area of ​​the upper baffle 112 gradually decreases.

[0021] The above area is the area projected onto the cross section of the tube shell, or the area projected onto the vertical plane.

[0022] 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 flow. As the distance from the inlet increases, the heat transfer effect of the upper part of the shell becomes better and better, while the heat transfer effect of the lower part of the shell becomes worse and worse. The main reason is that as the gas continues to flow. Because the gas density is small, the gas flows upward, which significantly increases the heat exchange gas in the upper part, so it is necessary to design the heat exchange structure for improvement. In the present invention, along the flow direction of the gas, the area ratio of the area of ​​the lower baffle 111 to the area of ​​the upper baffle 112 in the baffle group changes. As the gas in the shell flows, it gradually moves closer to the center, so that the center of the fluid strengthens the heat exchange around the heat exchange tubes of the shell and tube, which changes the previous heat exchange method, enhances the heat exchange efficiency at different positions, makes the heat exchange uniform on the whole, and further achieves the purpose of enhancing heat transfer.

[0023] As an improvement, along the flow direction of the gas in the shell, the area ratio of the lower baffle to the upper baffle in the baffle group is gradually reduced. Through the above-mentioned change in amplitude, the overall heat exchange can be further uniform, further achieving the purpose of enhancing heat transfer.

[0024] As an improvement, the sum of the projected areas of the lower baffle and the upper baffle of the baffle group on the shell cross section is 140-180% of the shell cross section area, preferably 160-170%.

[0025] As an improvement, the ratio of the area of ​​the lower baffle plate of the baffle plate group to the area of ​​the upper baffle plate is 0.9-1.3, preferably 1.0-1.2 times.

[0026] As an improvement, the baffle is a segmented baffle.

[0027] As an improvement, the shell side and the tube side flow in countercurrent, and along the flow direction of the fluid in the tube side, the spacing of the baffle group increases continuously from the tube side inlet to the middle of the tube side. Then from the middle of the tube side to the tube side outlet, the spacing of the baffle group decreases continuously. 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, it was found in experiments and simulations that the heat exchange in the middle is significantly greater than the heat exchange at the tube side inlet and outlet. Therefore, by changing the spacing between the baffles, the heat exchange area between the tube side fluid and the shell side fluid in the baffle also changes. Therefore, the uneven heat exchange is compensated by the change in area, thereby further improving the heat exchange efficiency.

[0028] As an improvement, along the flow direction of the fluid in the tube, from the tube entrance to the middle of the tube, the distance between the baffles increases. Then, from the middle of the tube to the tube exit, the distance between the baffles decreases. The above changes in the range can make the heat transfer per unit length of the entire fluid movement more uniform, further improving the heat transfer efficiency.

[0029] As an improvement, the shell side contains hot air, flue gas or waste heat gas.

[0030] The tube inlet pipe 9 is connected with a flow control valve to control the flow rate of the tube. The tube outlet pipe 10 is provided with a first temperature sensor. Multiple second temperature sensors are equidistantly arranged in the shell to detect the temperature of each section of the heat exchange tube. The controller is data-connected with the flow control valve, the first temperature sensor, and the second temperature sensor to form a control system.

[0031] In the shell and tube heat exchanger, the first temperature sensor and the second temperature sensor are used to detect the temperature of the tube-side fluid and the shell-side fluid. After comparing the temperature difference, the flow rate of the tube-side fluid is automatically adjusted through the flow control valve to maximize the heat utilization of the internal heat source per unit space and avoid the phenomenon of too low heat exchange temperature of the cold source.

[0032] When the difference between the shell-side fluid temperature and the tube-side fluid temperature is greater than the preset data, the flow rate is controlled to increase. The flow control valve is automatically controlled by the controller to control the flow, which has a high degree of intelligence and can achieve automatic adjustment and control.

[0033] 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 horizontal shell-and-tube heat exchanger for shell-side gas, the shell-and-tube heat exchanger comprising a tube shell, a heat exchange tube, a shell-side inlet pipe and a shell-side outlet pipe; the shell-side inlet pipe and the shell-side outlet pipe are respectively located at both ends of the heat exchanger; the heat exchange tube is arranged in the tube shell, and the heat exchange tube is fixedly connected to the tube sheet; characterized in that: The fluid in the shell side is gas, and a plurality of baffle groups are arranged in the tube shell, the baffle group including a lower baffle located at the lower part of the tube shell and an upper baffle located at the upper part of the tube shell; along the flow direction of the gas in the shell side, the area ratio of the lower baffle to the upper baffle in the baffle group is gradually reduced; the shell side and the tube side are countercurrent flows, and along the flow direction of the fluid in the tube side, from the tube side inlet to the middle position of the tube side, the spacing of the baffle groups increases continuously; and then from the middle position of the tube side to the tube side outlet, the spacing of the baffle groups decreases continuously; Along the flow direction of the gas in the shell side, the ratio of the area of ​​the lower baffle plate to the area of ​​the upper baffle plate in the baffle plate group gradually decreases to a smaller and smaller extent.

2. The shell and tube heat exchanger according to claim 1, characterized in that: The sum of the projected areas of the lower baffle and the upper baffle of the baffle group on the shell cross section is 140-180% of the shell cross section area.

3. The shell and tube heat exchanger according to claim 2, characterized in that: The sum of the projected areas of the lower baffle and the upper baffle of the baffle group on the shell cross section is 160-170% of the shell cross section area.

4. The shell and tube heat exchanger according to claim 1, characterized in that: The ratio of the area of ​​the lower baffle plate to the area of ​​the upper baffle plate of the baffle plate group is 0.9-1.

3.

5. The shell and tube heat exchanger according to claim 4, characterized in that: The ratio of the area of ​​the lower baffle plate to the area of ​​the upper baffle plate of the baffle plate group is 1.0-1.2.

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