CN103968688B - Shell-and-tube heat exchanger and plate hole machining method thereof - Google Patents

Abstract

The invention relates to a heat transfer technology, and provides a shell-and-tube heat exchanger and a processing method of plate holes of the shell-and-tube heat exchanger. The technology adopts a radial topological method to arrange the heat exchange tubes, and the shell-side fluid uniformly flows through all the heat exchange tubes along the radial direction by matching with the annular and disc-shaped baffle plates which are alternately arranged, so that the utilization rate of the heat exchange tubes is improved. The shell-and-tube heat exchanger mainly comprises a cylinder body, a tube plate, a tube box, a heat exchange tube and baffle plates, wherein the baffle plates are arranged alternately by adopting annular baffle plates and disc-shaped baffle plates, and the total number of the baffle plates is odd. The heat exchange tubes are arranged on concentric circles with different diameters and centered on the symmetry axis of the heat exchanger, and are uniformly distributed in the circumferential direction. The distance between the heat exchange tubes is not a fixed value, and the minimum distance is more than or equal to 1.25 times of the outer diameter of the heat exchange tubes.

Description

A shell-and-tube heat exchanger and its plate hole processing method

Technical field:

The invention relates to a heat transfer technology, in particular to a shell-and-tube heat exchanger. Based on the fractal theory, the radial topology is used to arrange the heat exchange tubes, and the alternately arranged disc-shaped and annular baffles maximize the uniformity of the shell-side fluid flow to improve the utilization of the heat exchange tubes .

Background technique:

Heat exchange equipment can be divided into: condenser, evaporator, reheater, superheater, etc. according to the function, and can be divided into: shell and tube heat exchanger, finned tube heat exchanger, plate heat exchanger according to the characteristics of heat exchange components Heater (including plate-fin heat exchanger and plate-fin heat exchanger).

The shell and tube heat exchanger is the most widely used heat exchanger in the process industry. It is mainly composed of shell, tube sheet, heat exchange tube, head, baffle and other components, and can use stainless steel, ordinary carbon steel, copper or other non-ferrous metals as materials. During operation, one kind of fluid enters through the connecting pipe of one end of the head, passes through the heat exchange tube, and flows out from the connecting pipe of the other end of the head, which is called the tube side; The other takes over the outflow, which is called the shell side. As a key component for heat transfer of cold and hot fluids, heat exchange tubes are constantly optimized in structure and type. With the continuous emergence of new high-efficiency heat exchange tubes, the application range of shell and tube heat exchangers continues to expand. At present, there are two types of measures to enhance the heat transfer of heat exchange tubes, namely (1) changing the flow of the fluid to increase the flow rate; (2) changing the shape and size of the heat exchange surface.

The advantage of the shell-and-tube heat exchanger is that the unit volume equipment can provide a large heat transfer area and a good heat transfer effect. Due to the solid structure and the wide range of materials that can be selected, it has strong adaptability and large operating flexibility. Especially in high temperature, high pressure and large devices, it is more common to use. However, the biggest disadvantage of the shell-and-tube heat exchangers covered by traditional design standards (such as GB151-1999 shell-and-tube heat exchangers) and currently commonly used is that the heat exchange area is not fully utilized.

The research on enhanced heat exchange technology of various heat exchangers mainly focuses on the change of fluid flow state in the heat exchanger and the optimization of the parameters of each component. The main research object of the parameters of the heat exchanger components is the heat exchanger Arrangement of heat pipes (plates) (along or fork), number of rows of heat exchange tubes (plates), spacing of heat exchange tubes (plates), spacing of fins, shape of fins, etc. In the design of the heat exchanger, the influence of the number and arrangement of the heat exchange tubes, the shape of the heat exchange tubes, the shape of the fins and the spacing on the performance of the heat exchanger cannot be ignored. In order to increase the flow rate of the shell-side fluid of the shell-and-tube heat exchanger and increase the heat transfer efficiency, a certain number of baffles perpendicular to the tube bundle are often installed in the shell, so that the fluid flow rate can be increased, and the shell-side fluid is also forced to comply with the regulations. The length of the distance, the cross-flow with the tube bundle is formed many times, which is beneficial to the increase of the heat transfer coefficient outside the tube. The form of the baffle is circular (bow), disc and ring. The baffles are circular, bow-shaped, spiral and so on. These baffles make the shell-side fluid form dead zones and stagnation zones in the upper and lower parts of the baffles, and the forced flow that really plays a role in heat exchange The region of turbulence is limited.

At present, the commonly used arrangements of heat exchange tubes include equilateral triangles, regular triangles, squares, and squares. In order to facilitate engineering applications, fixed dimensions for these arrangements are given in the design standards. From a hydrodynamic point of view, the fixed spacing of the heat exchange tubes is very unfavorable to the uniformity of the shell-side fluid flow. On the other hand, since the flow state of the shell-side fluid in the heat exchange tube gap cannot be accurately judged, such as its flow velocity and pressure distribution, it is extremely difficult to optimize the shell-side flow.

With the advantage of computer simulation, the whole field flow analysis and structural strength calculation can be carried out for a given heat exchanger. In terms of numerical analysis of heat exchangers, there are a large number of domestic literature reports, such as using the steady-state distribution parameter method to simulate the optimal length of the circuit when the condenser and evaporator are used; using the distribution parameter method to simulate the corrugated multi-channel single Simulation of heat transfer performance of process plate evaporator at small heat transfer temperature difference; simulation of cooling air dry evaporator coil under wet conditions; simulation of ship cold storage evaporator and room air conditioning evaporator; Simulation of heat transfer process in finned heat exchangers, etc.

The key to the numerical analysis of heat transfer characteristics of heat exchange tubes is the establishment of calculation models. Currently commonly used models include porous media model, solid model and periodic unit channel model. Using the porous media model oversimplifies the internal structure of the heat exchanger, and the simulation results cannot accurately reflect the detailed information of the real flow and heat transfer conditions in the local area, and some important simulation parameters are not related to the structural type, geometric size and operation of the heat exchanger. It is related to the medium, so it has certain limitations. The porous media model should not be used when studying the flow distribution and enhanced heat transfer mechanism of the local details of the flow field of the new shell-side support structure.

Numerical simulation of the flow and heat transfer characteristics of the heat exchanger by using a solid model can obtain the qualitative analysis results of the heat transfer and flow characteristics of the flow heat exchanger. However, for large shell-and-tube heat exchangers, due to the large number of heat exchange tubes , the number of grids and calculation amount of the model increase abnormally, and the existing software and hardware cannot meet the requirements. To this end, the researchers proposed a simplified calculation method for the periodic unit flow channel model, ignoring the influence of the particularity of the fluid flow and heat transfer in the piping area near the wall of the cylinder on the overall performance of the shell side flow and heat transfer. If the heat exchange tube layout is square, the fluid flow space surrounded by four heat exchange tubes can be taken as a "unit flow channel" calculation model, which can effectively reduce the difficulty of numerical simulation of the longitudinal flow shell-side heat exchanger. However, the unit channel model is suitable for some longitudinal flow shell-side heat exchangers with symmetrical distribution of heat exchange tube bundles and tube bundle support structures. For shell-and-tube heat exchangers that do not have the above structural features, such as baffle heat exchangers , spiral plate heat exchanger, etc., it cannot be simplified in this way. For a shell-and-tube heat exchanger with a small shell diameter, even if it meets the simplified requirements of the symmetry of the unit flow channel, the fluid in the tube layout area near the wall of the cylinder has a great influence on the overall performance of the shell side flow and heat transfer and cannot be ignored , the simulation results of the unit runner model deviate greatly from the actual working conditions.

Many studies have shown that according to the layout of traditional heat exchange tubes (regular triangle, regular triangle, square, and square) with bow-shaped and semicircular baffles, it is difficult to form a uniform flow of shell-side fluid, that is, not all heat exchangers Uniform shell-side fluid flows around the tubes, some areas have high velocity, some areas have low velocity, and some areas are even dead zones (fluid does not flow), so this part of the heat exchange tube does not actually work. It can be seen that optimizing the arrangement of heat exchange tubes has important engineering significance for the design and application of such heat exchangers.

Invention content:

The present invention aims at the disadvantage that the spatial distribution of heat exchange tubes in the existing shell-and-tube heat exchanger is not conducive to the uniform flow of shell-side fluid. The heat exchange tubes are arranged layer by layer, and the heat exchange tubes are evenly distributed in the circumferential direction, and the annular and disc-shaped baffles arranged at intervals are used to realize the uniform flow of the shell side fluid.

Another object of the present invention is to provide a method for processing the plate holes of the shell-and-tube heat exchanger.

Concrete technical scheme of the present invention is as follows:

A shell-and-tube heat exchanger mainly includes a cylinder body, a tube sheet, a tube box, a heat exchange tube and a baffle plate. Both sides of the cylinder body are connected to the left and right tube boxes. There is a left tube plate, a right tube plate is set at the connection between the cylinder body and the right tube box, inlets and outlets are arranged on both sides of the cylinder body, and multiple baffles are arranged at equal intervals in the cylinder body, and the baffles are parallel to the left and right tubes The baffles are arranged alternately with annular baffles and disc-shaped baffles. The total number of baffles is an odd number, and the ones adjacent to the left and right tube sheets are all circular Baffles; each baffle and the left and right tube plates are equipped with plate holes, and the diameters of each plate hole are equal;

A plurality of heat exchange tubes are arranged inside the cylinder, and each heat exchange tube is arranged parallel to the axis of the cylinder body, and each heat exchange tube passes through each baffle plate and the plate holes on the left and right tube plates at both ends and the left and right tube plates. The right tube box is connected, and the left and right tube boxes are respectively provided with a tube pass inlet and a tube pass outlet;

The outer diameter of the circular baffle is equal to that of the cylinder, and the middle part is a hollow ring; there is a circular gap between the outer diameter of the disc-shaped baffle and the cylinder.

Under the action of the ring-shaped and disk-shaped baffles, the shell-side fluid flows radially, diffuses from the center to the surroundings or converges from the surroundings to the center.

The inlet of the cylinder body is connected with an inlet nozzle, and the outlet of the cylinder body is connected with an outlet nozzle.

The inlet of the tube pass is connected with an inlet nozzle, and the outlet of the tube pass is connected with an outlet nozzle.

The area of the hollow ring of the annular baffle is equal to the void area of the disc-shaped baffle.

The radius r _i of the inner circle of the annular baffle is

${\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; Rh</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: R is the inner radius of the cylinder, determined according to the method provided by the GB151-1999 standard, h=0.2~0.45R.

The radius r _o of the disc-shaped baffle is

${\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; arccos</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; Rh</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula: R is the inner radius of the cylinder, h=0.2～0.45R.

The positions of the annular baffles and disc-shaped baffles correspond to the plate holes on the left and right tube plates, and the distance between adjacent plate holes is ≥1.25d.

A method for processing plate holes of a shell-and-tube heat exchanger, wherein, the arrangement method of the plate holes on the left and right tube plates is as follows:

When arranging the plate holes, the minimum spacing d _s of adjacent plate holes should be determined first, and the center distance d _s of adjacent plate holes should be greater than or equal to 1.25d; (d _s ≥ 1.25d); the adjacent plate holes include Adjacent plate holes and adjacent plate holes between adjacent and different adjacent layers; the center of the plate hole is located on concentric circles with different diameters centered on the center of the tube sheet, and the plate holes on each concentric circle are in the circumferential direction Evenly distributed;

(1) Set the first plate hole in the center of the left and right tube sheets as the reference plate hole; take the center of the first plate hole as the origin and d _s as the radius to draw a circle, and set 6 plate holes evenly on the circumference, It is the plate hole of the first layer; then continue to arrange the plate holes layer by layer in the order from the inside to the outside, the position of the outer layer plate hole is based on the inner layer plate hole, and the center of the outer layer plate hole is located The center line of the line connecting the centers of adjacent plate holes;

(2) When arranging the board holes according to step 1, when the distance between the board holes of the same layer on a certain layer is greater than or equal to 2d _s (twice the minimum distance), move the board holes of the inner layer radially to the Layer position, and add a plate hole between adjacent plate holes, so that the number of plate holes in this layer is twice the number of plate holes in the inner layer, and this layer is a fractal layer;

Arrange the plate holes according to the above method, starting from the second layer plate hole, the method of determining the radius of the concentric circle where the nth layer plate hole is located is as follows:

①Select any two adjacent plate holes in the n-1th layer of plate holes, and use the center points i and j of the two plate holes as the reference to determine the perpendicular line l of the line connecting the center points i and j;

② Determine a point k on the mid-perpendicular line l, this point is located outside the plate hole of the n-1th layer, and the distance from the center points i and j of the two plate holes of the n-1th layer is both d _s ;

③ Determine whether the distance between point k and the nearest plate hole in the n-2th layer plate hole is greater than or equal to d _s , if yes, the distance from point k to the center of the tube sheet is the radius of the concentric circle where the nth layer plate hole is located; If it is less than d _s , then move point k outward along the median l to point k', so that the distance from point k' to the nearest plate hole in the n-2th layer hole is equal to d _s , then point k' The distance to the center of the tube sheet is the radius of the concentric circle where the hole of the nth layer plate is located.

Among them, the processing method of the plate holes on the circular baffle plate and the disc-shaped baffle plate is the same as that of the left and right tube sheets, and the positions of the plate holes correspond to each other. The heat exchange tubes pass through the plates on the tube plate and the baffle plate. Behind the holes, a shell-side space with periodic characteristics in the circumferential direction is formed.

The shell-side flow field space formed after the heat exchange tubes pass through the plate holes arranged according to the method has the characteristics of circumferential equal flow resistance. , the shell-side fluid flows through each heat exchange tube in a radial direction (dividing from the center to the surrounding or converging from the surrounding to the center), which can ensure that the utilization rate of the heat exchange tube is 100%. At the same time, on the premise that the total flow rate of the shell-side fluid is known, the average velocity of the shell-side fluid flowing through the heat exchange tube can be estimated (average velocity = total flow rate/cross-sectional area of the gap), thereby estimating the heat transfer coefficient of the heat exchange tube .

According to the principle, the average spacing of arranged heat exchange tubes is greater than 1.25d, so the number of heat exchange tubes that can be arranged is smaller than the number of heat exchange tubes obtained (the distance between adjacent heat exchange tubes is equal to 1.25d). When d _s takes different values, the obtained lattice of center points of plate holes has geometrically similar characteristics. The smaller the d _s , the denser the plate holes.

According to the above principles, the drawing software can be used to determine the positions of the holes of each layer plate one by one from the center of the tube plate to the direction of increasing radius by using the drawing method.

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

(1) For the heat exchange tube bundles of shell and tube heat exchangers commonly used at present, the flow law of the shell side fluid is not easy to determine, so the utilization rate of the heat exchange tubes cannot be guaranteed. heat effect. However, the heat exchange tube bundles of the present invention are evenly arranged in the circumferential direction, and the shell-side fluid is evenly diffused radially or converged toward the center under the action of alternately arranged annular baffles and disk-shaped baffles. , fluid passes around each heat exchange tube, there is no dead zone in the entire flow field, and the utilization rate of the heat exchange tube is 100%, which can significantly reduce the design margin of the heat exchange area.

(2) The arrangement of the heat exchange tubes of the present invention has a periodic feature in the circumferential direction, so that the shell-side flow field has a periodic feature, so the flow direction of the shell-side fluid is predictable. The average velocity of the shell-side fluid and the heat transfer coefficient of the heat exchange tube can be estimated according to the total flow rate of the shell-side fluid and the gap size. In addition, according to the periodic characteristics of the shell-side flow field, a single-cycle numerical analysis model of the heat exchanger can be established. Compared with the overall model of the heat exchanger, it greatly reduces the difficulty of modeling and reduces the amount of calculation, which is helpful Accurately predict heat transfer performance and stress distribution in heat exchangers.

(3) When the heat exchange tubes of the present invention are arranged, a fractal method is adopted to divide one shell side fluid into two evenly at the fractal position (the shell side fluid flows in the direction of increasing radius, and vice versa), and is in the fractal position The heat exchange tubes on the top have a "rectification" effect, which promotes the uniform flow of the shell side fluid. In addition, since the order of fractal topology can reach infinity, the present invention is not limited by the outer diameter of the heat exchanger, and is especially suitable for large-scale shell-and-tube pressure vessels, such as large-scale EO reactors (diameter 8m, heat exchange tubes nearly 20,000) design.

Description of the drawings:

Figure 1 is a schematic structural view of a shell-and-tube heat exchanger.

Figure 2 is a schematic diagram of layer-by-layer arrangement of plate holes.

Fig. 3 is a schematic structural diagram of a circular baffle.

Fig. 4 is a structural schematic diagram of a disk-shaped baffle.

Figure 5 is a schematic structural view of the left and right tube sheets.

In the figure, 1-tube outlet connection; 2-left tube box; 3-left tube plate; 4-shell side inlet connection; 5-cylinder; 6-shell side outlet connection; 7-right tube plate; 8-right Tube box; 9-tube inlet connection; 10-right support; 11-circular baffle 1; 12-disc baffle 1; 13-circular baffle 2; 14-disc baffle 2; 15-annular baffle 3; 16-left support; 17-heat exchange tube.

detailed description:

Embodiment one:

Design a heat exchanger, which is mainly composed of shell, tube sheet, heat exchange tube, tube box, baffle plate and other components, and the material is not limited, as shown in Figure 1. The tube-side fluid enters from the tube-side inlet nozzle 9 on the right tube box 8, flows through the heat exchange tube bundle 17 from left to right, collects in the left tube box 2, and is discharged from the tube-side outlet nozzle 1; the shell-side fluid flows from the cylindrical The shell side inlet joint 4 of the cylinder 5 enters, and under the action of the baffle, the shell side flows radially to form a cross flow with the tube side fluid, and finally is discharged through the shell side inlet joint 7 of the cylinder 5 .

The heat exchange tube bundle is fixed by the left tube plate 3 and the right tube plate 7 welded to the cylinder body 5, and passes through each baffle. Both the tube sheet and the baffle (ring-shaped and disc-shaped) have plate holes consistent with the outer diameter of the heat exchange tubes. The structures of the ring-shaped and disc-shaped baffles are shown in Figures 3 and 4, respectively, and the structures of the left and right tube sheets are shown in Figure 5, with corresponding plate holes opened on them. The hollow ring of the annular baffle and the vacant part of the disc-shaped baffle need not be provided with plate holes.

The main parameters of the heat exchanger, such as shell diameter, length, heat exchange tube diameter and number of baffles, are determined by the process design. The number of heat exchange tubes and the number of baffles may need to be corrected according to the design method of the present invention.

The number of baffles must be an odd number, and the baffles near the two tube sheets must be annular baffles, so as to form a uniform shell-side fluid flow. When the inlet and outlet pipes of the shell side adopt the scheme shown in Figure 1, the area where the inlet and outlet of the shell side are located cannot form a uniform flow, and the method of evenly arranging multiple pipes in the circumferential direction can be used to improve the flow uniformity of these two areas Spend.

The thickness of the tube sheet is designed according to the requirements of the GB151-1999 standard, and the dimensions and tolerances of all plate holes are determined according to the requirements of the standard.

According to the arrangement of the heat exchange tubes of the present invention, the average gap between the heat exchange tubes should be greater than 1.25 times the outer diameter of the heat exchange tubes, so the total number of heat exchange tubes that can be arranged should be less than the number of heat exchange tubes designed according to the GB151-1999 standard ; and because the radial topological arrangement improves the utilization rate of the heat exchange tubes, the efficiency of the heat exchange tube bundle is improved, which can make up for the shortage of the reduction in the number of tubes. If the heat transfer calculation results show that the heat exchange area needs to be increased, the shell diameter can be increased to increase the number of heat exchange tubes.

Embodiment two:

According to the plate hole arrangement principle of the present invention, the following steps are adopted to determine the position of the plate holes.

① As shown in Figure 2, establish a polar coordinate system, the origin of the coordinate system is placed at the center of the tube sheet, the radial coordinate is r, and the circumferential coordinate is . Set the first plate hole in the center of the tube plate.

② Determine the minimum spacing d _s of the plate holes. Take (r=0) as the center and d _s as the radius to make the first concentric circle. According to the principle (3), 6 plate holes are uniformly arranged on the concentric circle, and the center of one of the plate holes is located at superior. The distance between these 6 plate holes meets the requirement of d _s ≥ 1.25d.

③According to the method for determining the radius of concentric circles, the radius of the second concentric circle is calculated to be 2d _s , and 6 plate holes are uniformly arranged on this circle. The distance between these 6 plate holes is 2d _s . According to the requirement of step (2), the number of plate holes is doubled (that is, the number of plate holes in the second layer is 12), and here is the first fractal position. Investigate the distance between the hole in the second layer and the hole in the first layer, and meet the requirement of d _s ≥ 1.25d.

④According to the method for determining the radius of concentric circles, the radius of the third concentric circle is calculated as 12 plate holes are uniformly arranged on the circle. The positions of these plate holes relative to the plate holes of the second layer meet the requirement of d _s ≥ 1.25d.

⑤According to the method for determining the radius of the concentric circles, use the drawing method to determine the radius of the concentric circles where the hole on the fourth layer is located, that is, use the point is the center of the circle (this point is the center of the plate hole marked in bold in the 4th layer plate hole on the accompanying drawing 2), d _s is the radius to make a circle, and this circle is consistent with There are two intersection points, and the vector of the intersection point away from the center of the tube sheet is used as the radius of the concentric circle where the hole in the fourth layer plate is located. Arrange 12 plate holes evenly on the concentric circle according to principle (2).

Referring to the above steps, the positions of the holes on each layer can be determined one by one. A total of 23 layers of plate holes are arranged on the tube plate shown in Figure 2, and it has experienced 4 fractals, and the fractal positions are at the 2nd, 5th, 10th, and 23rd layer holes in sequence.

Application example one:

After the mixed gas in a reactor is heat-exchanged with the feed stream, it needs to be cooled from 110°C to 60°C with circulating cooling water, and then enters the absorption tower for absorption. It is known that the flow rate of the mixed gas is 2.4×10 ⁵ kg/h, the pressure is 6.9MPa, the pressure of the circulating cooling water is 0.4MPa, the inlet temperature of the circulating water is 29°C, and the outlet temperature is 39°C. Heater design method Design a shell-and-tube heat exchanger to meet the requirements of the working conditions.

Considering that water is easy to scale at a low flow rate, and the velocity of water in the tube side is relatively high, the medium of the tube side is circulating water, and the medium of the shell side is a mixed gas. The physical parameters of circulating water at 85°C ((110+60)/2=85) are: the density is 994.3kg/m ³ , the specific heat capacity at constant pressure is 4.174kJ/(kg·K), and the thermal conductivity is 0.624W/ (m·K), the viscosity is 0.742×10 ^-3 Pa·s; the physical parameters of the mixed gas at 34°C ((29+39)/2=34) are: the density is 90kg/m ³ , and the specific heat capacity at constant pressure is 3.297kJ/(kg·K), the thermal conductivity is 0.0279W/(m·K), and the viscosity is 1.5×10 ^-5 Pa·s.

According to "GB151-1999 Shell and Tube Heat Exchanger" and related design manuals, the design calculation is carried out, and the basic parameters of the obtained heat exchanger include:

Shell inner diameter: 1450mm Heat exchange tube size: Φ25×2.5mm

Heat exchange tube spacing: 44mm Heat exchange tube length: 7000mm

Number of heat exchange tubes: 980 Number of baffles: 14

Baffle spacing: 450mm Baffle height: 360mm

The inner diameter of the shell side connection: 310mm The inner diameter of the tube connection: 370mm

Using the heat exchange tube arrangement method of the present invention, the arrangement of the designed annular baffles, disk-shaped baffles and plate holes on the tube plate is shown in Figures 3, 4 and 5, respectively. The radius r _i of the inner circle of the annular baffle is 330mm; the radius r _o of the outer circle of the disc-shaped baffle is 650mm.

After three fractals, 787 heat exchange tubes were arranged. The number of heat exchange tubes is 80% of the regular triangle arrangement, and the inlet temperature and mass flow rate of the shell side and tube side medium are used as boundary conditions, and the single shell side, tube side and heat exchange tubes are established by using the computational fluid dynamics software FLUENT. According to the periodic numerical model, the outlet temperature of the tube side (cooling water) is calculated to be 38.3°C, and the outlet temperature of the shell side (mixed gas) is 57.2°C, which meet the design requirements.

It can be seen that the heat exchange efficiency of the shell-and-tube heat exchanger of the present invention is significantly improved compared with the traditional design on the premise of meeting the design requirements, thereby reducing the number of heat exchange tubes.

Claims (4)

1. A shell-and-tube heat exchanger, characterized in that it mainly includes a cylinder body, a tube sheet, a tube box, a heat exchange tube and a baffle plate, and the left and right tube boxes are connected on both sides of the cylinder body, and the cylinder body and There is a left tube plate at the joint of the left tube box, and a right tube plate at the joint between the cylinder body and the right tube box. There are inlets and outlets on both sides of the cylinder body, and multiple baffles are arranged at equal intervals in the cylinder body. It is arranged parallel to the left and right tube sheets, and the baffles are arranged alternately with circular baffles and disc-shaped baffles, and the total number of baffles is an odd number, adjacent to the left and right tube sheets All of them are ring-shaped baffles; each baffle and the left and right tube plates are equipped with plate holes, and the diameters of each plate hole are equal; A plurality of heat exchange tubes are arranged inside the cylinder, and each heat exchange tube is arranged parallel to the axis of the cylinder body, and each heat exchange tube passes through each baffle plate and the plate holes on the left and right tube plates at both ends and the left and right tube plates. The right tube box is connected, and the left and right tube boxes are respectively provided with a tube pass inlet and a tube pass outlet; The outer diameter of the circular baffle is equivalent to that of the cylinder, and the middle part is a hollow ring; there is a circular gap between the outer diameter of the disc-shaped baffle and the cylinder; The area of the hollow ring of the annular baffle is equal to the vacant area of the disc-shaped baffle; The radius r _i of the inner circle of the annular baffle is ${\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&rsqb;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$ The radius r _o of the disc-shaped baffle is ${\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>\sqrt{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&rsqb;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ In the formula: R is the inner radius of the cylinder, h=0.2~0.45R, and d is the outer diameter of the heat exchange tube. 2. The shell-and-tube heat exchanger according to claim 1, characterized in that: the annular baffles, disk-shaped baffles correspond to the positions of the plate holes on the left and right tube plates, and the adjacent plates The hole spacing is ≥1.25d, where d is the outer diameter of the heat exchange tube. 3. The method for processing the plate holes of any one of claims 1-2, wherein the method for arranging the plate holes on the left and right tube plates has the following characteristics: When arranging the plate holes, the minimum spacing d _s of adjacent plate holes should be determined first, and the center distance d _s of adjacent plate holes should be greater than or equal to 1.25d; the adjacent plate holes include adjacent plate holes on the same layer and adjacent , Adjacent plate holes between different adjacent layers; the center of the plate hole is located on concentric circles with different diameters centered on the center of the tube sheet, and the plate holes on each concentric circle are evenly distributed in the circumferential direction; (1) Set the first plate hole in the center of the left and right tube sheets as the reference plate hole; take the center of the first plate hole as the origin and d _s as the radius to draw a circle, and set 6 plate holes evenly on the circumference, It is the plate hole of the first layer; then continue to arrange the plate holes layer by layer in the order from the inside to the outside, the position of the outer layer plate hole is based on the inner layer plate hole, and the center of the outer layer plate hole is located The center line of the line connecting the centers of adjacent plate holes; (2) When arranging the plate holes according to step 1, when the distance between the plate holes of the same layer on a certain layer is greater than or equal to 2d _s , the plate holes of the inner layer are moved radially to the position of the layer, and the adjacent Add a plate hole between the plate holes, so that the number of plate holes in this layer is twice the number of plate holes in the inner layer, and this layer is a fractal layer; Arrange the plate holes according to the above method, starting from the second layer plate hole, the method of determining the radius of the concentric circle where the nth layer plate hole is located is as follows: ①Select any two adjacent plate holes in the n-1th layer of plate holes, and use the center points i and j of the two plate holes as the reference to determine the perpendicular line l of the line connecting the center points i and j; ② Determine a point k on the mid-perpendicular line l, this point is located outside the plate hole of the n-1th layer, and the distance from the center points i and j of the two plate holes of the n-1th layer is both d _s ; ③ Determine whether the distance between point k and the nearest plate hole in the n-2th layer plate hole is greater than or equal to d _s , if yes, the distance from point k to the center of the tube sheet is the radius of the concentric circle where the nth layer plate hole is located; If it is less than d _s , then move point k outward along the median l to point k', so that the distance from point k' to the nearest plate hole in the n-2th layer hole is equal to d _s , then point k' The distance to the center of the tube sheet is the radius of the concentric circle where the hole of the nth layer plate is located. 4. according to the processing method of the plate hole of the shell-and-tube heat exchanger described in claim 3, wherein, the processing method of the plate hole on the annular baffle plate and the disk-shaped baffle plate is the same as that of the left and right tube sheets, and each The positions of the plate holes correspond to each other. After the heat exchange tubes pass through the plate holes on the tube plate and the baffle, a shell-side space with periodic characteristics in the circumferential direction is formed.