A heat exchanger and a heat exchange tube arrangement optimization method thereof

Abstract

The present invention provides a heat exchanger and a method for optimizing the arrangement of heat exchange tubes thereof, wherein four adjacent heat exchange tubes in a tube bundle are arranged in a square, wherein the outer diameter of the heat exchange tube is d, the center distance between adjacent heat exchange tubes is P, and the angle between the square edge and the water flow direction is the inflow angle α, α≤90°; for the above arrangement: firstly obtain the effect of P / d, α and inlet flow rate U on the shell resistance C D and turbulence C L The response relationship between them; then C D Minimum, C L The maximum is the goal, and multi-objective optimization is performed; finally, according to the optimization results, C is selected D and C L , and the values ​​of P / d and α are inferred based on the response relationship. The tube bundle arrangement optimized by the above method can achieve a balance between shell resistance and turbulence, while reducing shell resistance and increasing turbulence as much as possible to maintain a high heat exchange efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchangers, and in particular relates to a heat exchanger and a method for optimizing the arrangement of heat exchange tubes thereof. Background Art

[0002] At present, ordinary shell and tube heat exchangers are composed of tube boxes, shells, tube sheets, heat exchange tubes, etc. The heat exchange tube bundles are arranged compactly, the shell resistance of the entire heat exchanger is large, the heat exchange efficiency of the heat exchange tubes is not high, and the temperature difference range of material heat exchange is small. In order to improve the heat exchange efficiency, fins are added to the heat exchange tubes, but this will increase the flow resistance of the shell side, which will lead to increased vibration of the heat exchange tubes and reduce the service life of the heat exchanger.

[0003] In response to the above problems, the Chinese patent "A fixed tube sheet heat exchanger" with application number CN201920963907.6 adopts heat exchange tubes made of non-metallic materials and tube sheets made of metal materials, and further improves the connection and sealing structure between the two, so as to avoid direct contact between the heat exchange tubes and the tube sheets, thereby preventing damage to the heat exchange tube structure caused by vibration and improving the service life of the heat exchanger. However, this solution also increases the processing difficulty of the existing heat exchanger by one level, and the measures to reduce vibration have failed to reduce the shell flow resistance, so the operating performance range is narrow. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a heat exchanger and a method for optimizing the arrangement of heat exchange tubes thereof, so as to solve the problem of optimizing the balance between the flow resistance and the heat exchange efficiency in the shell side.

[0005] The present invention achieves the above technical objectives through the following technical means.

[0006] A heat exchange tube arrangement optimization method: four adjacent heat exchange tubes in a tube bundle are arranged in a square, wherein the outer diameter of the heat exchange tube is d, the center distance between adjacent heat exchange tubes is P, and the angle between the square edge and the shell-side material flushing direction is the inflow angle α, α≤90°; for the above arrangement: first obtain the effect of P / d, α and the shell-side material inlet flow rate U on the shell-side resistance C D and turbulence C L The response relationship between them; then C D Minimum, C L The maximum is the goal, and multi-objective optimization is performed; finally, according to the optimization results, C is selected D and C L , and infer the values ​​of P / d and α based on the response relationship.

[0007] Furthermore, the response relationship was obtained by using Box-Behnken Design and Response Surface Method analysis.

[0008] Furthermore, a Nondominated Sorting Genetic Algorithm II genetic algorithm is used to perform the multi-objective optimization.

[0009] Furthermore, the surface of the heat exchange tube is densely covered with ellipsoidal protrusions, and the front and rear protrusions are arranged in a spiral shape.

[0010] Furthermore, the height of the protrusion is 0.15d, the center distance between the front and rear protrusions is 2.4d, and the deflection angle between the front and rear protrusions is 45°.

[0011] Furthermore, when the design value of the inlet flow velocity U is 0.1 m / s, the center spacing P between the heat exchange tubes (3) is 2.1 d, and the inflow angle α is 22°; when the design value of the inlet flow velocity U is 0.3 m / s, the center spacing P between the heat exchange tubes (3) is 1.25 d, and the inflow angle α is 14°; when the design value of the inlet flow velocity U is 0.5 m / s, the center spacing P between the heat exchange tubes (3) is 1.25 d, and the inflow angle α is 7°.

[0012] A heat exchanger comprises a tube box, a cylinder and heat exchange tubes, wherein the tube box is respectively connected to two ends of the cylinder, a tube sheet is provided between the tube box and the cylinder, and a baffle is provided in the cylinder; the heat exchange tubes are fixed in the cylinder through the tube sheet, and the two ends are respectively connected to the tube boxes on both sides, and the heat exchange tubes are arranged and set using the above-mentioned heat exchange tube arrangement optimization method.

[0013] Furthermore, the heat exchanger is a single-shell-pass and double-tube-pass structure.

[0014] Furthermore, the baffles are arcuate baffles, the spacing between adjacent baffles is 0.3D, and the height of the circular segment of the baffle is 0.25D, wherein D is the inner diameter of the cylinder.

[0015] Furthermore, the heat exchange tube is made of steel, and the baffle is made of polypropylene.

[0016] The beneficial effects of the present invention are:

[0017] (1) The present invention provides a method for optimizing the arrangement of heat exchange tubes, in which the common triangular arrangement is improved into a square arrangement. On this basis, the relationship between the spacing and the inlet angle on the shell resistance and turbulence is studied, and then the optimal arrangement parameter value scheme is given to achieve a balance between the shell resistance and turbulence, so as to reduce the shell resistance as much as possible on the one hand, and increase the turbulence as much as possible on the other hand to maintain a high heat exchange efficiency.

[0018] (2) The present invention adopts a heat exchange tube with elliptical protrusions on the surface to change the flow field of the shell-side material, thereby further reducing the shell-side flow resistance and the lateral vibration of the heat exchange tube.

[0019] (3) The present invention also provides a heat exchanger that arranges the heat exchange tube bundle using the above-mentioned optimization method, wherein corresponding optimal heat exchange tube arrangement parameters are given for different shell-side inlet flow rates. Compared with arbitrarily set arrangement parameters, the shell-side resistance can be reduced and the heat exchange efficiency can be greatly improved at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the heat exchanger of the present invention;

[0021] Figure 2 The diagram is a dimension diagram of the baffle in the heat exchanger of the present invention;

[0022] Figure 3 It is a side view of the heat exchange tube of the present invention;

[0023] Figure 4 This is a cross-sectional view of the heat exchange tube of the present invention;

[0024] Figure 5 This is a schematic diagram of the arrangement of heat exchange tubes of the present invention;

[0025] FIG6( a ) is a surface diagram showing the relationship between the inflow angle and the heat exchange tube spacing for the shell side resistance;

[0026] FIG6( b ) is a surface diagram of the relationship between the inlet flow rate and the heat exchange tube spacing for the shell side resistance;

[0027] Figure 6(c) is a surface diagram of the relationship between the inlet angle and the inlet flow velocity for the shell side resistance;

[0028] FIG7( a ) is a surface diagram showing the relationship between the inflow angle and the distance between heat exchange tubes and the turbulence;

[0029] FIG7( b ) is a surface diagram of the relationship between the inlet flow rate and the distance between the heat exchange tubes with respect to the turbulence;

[0030] Figure 7(c) is a surface diagram of the relationship between the inlet angle and the inlet velocity for turbulence;

[0031] Figure 8 It is the optimization curve between shell resistance and turbulence.

[0032] Reference numerals:

[0033] 1-pipe box; 11-pipe pipe; 12-tube sheet; 2-cylinder;

[0034] 21- baffle; 22- tie rod; 23- distance tube; 24- shell side pipe;

[0035] 25- bracket; 3- heat exchange tube. DETAILED DESCRIPTION

[0036] Embodiments of the present invention are described in detail below, examples of the illustrated embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0037] like Figure 1 The shell and tube heat exchanger shown is a single-shell double-tube structure, specifically including a tube box 1, a cylinder 2 and a heat exchange tube 3; wherein the bottom of the cylinder 2 is placed on the ground through a bracket 25, and the tube box 1 is connected to both ends of the cylinder 2, and a tube sheet 12 is provided between the tube box 1 and the cylinder 2, wherein the tube sheet 12 can be connected to the end of the cylinder 2 by welding, and the tube sheet 12 and the tube box 1 can be connected by bolts. In the figure, the upper and lower sides of the left tube box 1 are respectively provided with tube-pass pipes 11, and a partition plate is also provided inside the left tube box 1, and the partition plate divides the inner cavity of the tube box 1 into upper and lower parts through the axis of the tube box 1, wherein the upper inner cavity is connected to the upper tube-pass pipe 11, and the lower inner cavity is connected to the lower tube-pass pipe 11.

[0038] Two shell-side pipes 24 are provided on the side wall of the cylinder 2, and the two shell-side pipes 24 are located at both ends of the cylinder 2. A plurality of baffles 21 are evenly distributed inside the cylinder 2 and between the two shell-side pipes 24, and the baffles 21 are specifically arched baffles, and the baffles 21 are fixed by tie rods 22 and distance tubes 23; Figure 2 As shown, the spacing between adjacent baffles 21 is 0.3D, the height of the rounded portion of the baffle 21 is 0.25D, and D is the inner diameter of the cylinder 2. A plurality of heat exchange tubes 3 are evenly and densely distributed in the inner cavity of the cylinder 2, and both ends of the heat exchange tubes 3 are respectively fixed on the tube sheets 12 at both ends, and the two ends of the heat exchange tubes 3 are respectively connected to the left and right side tube boxes 1. When in use, the tube-side material enters the left tube box 1 through a tube-side pipe 11, and is then transported to the right tube box 1 by half the number of heat exchange tubes 3. After turning 180° in the right tube box 1, it is reversely transported back to the left tube box 1 by the other half of the heat exchange tubes 3 (the total distance traveled by the tube-side material is twice the tube pass, so it is called double tube pass), and finally output to the outside through another tube-side pipe 11; the shell-side material flows into the cylinder 2 through a shell-side pipe 24, and flows out through another shell-side pipe 24 (the distance traveled by the shell-side material is one shell pass, so it is called single shell pass). When the shell-side material flows in the cylinder 2, it flows in a serpentine manner under the action of the baffle 21, thereby forming a vertical flushing of the surface of the heat exchange tube 3, and realizing heat exchange with the tube-side material in the heat exchange tube 3 during the flushing process.

[0039] like Figure 3 , Figure 4The heat exchange tube 3 shown has elliptical protrusions on its surface, and the front and rear protrusions are arranged in a spiral shape along the surface of the heat exchange tube 3. The height of each protrusion is 0.15d, and the center distance between the front and rear protrusions (along the axis direction of the heat exchange tube 3) is 2.4d, where d is the outer diameter of the heat exchange tube 3, and the deflection angle between the front and rear protrusions (around the axis of the heat exchange tube 3) is 45°. In the present invention, by introducing a heat exchange tube 3 with elliptical protrusions on the surface, the flow field of the shell side material in the cylinder 2 is changed, that is, by changing the inter-tube pressure and vortex field when the shell side material flows through the above heat exchange tube 3, the purpose of reducing the shell side flow resistance and reducing the lateral vibration of the heat exchange tube 3 is achieved.

[0040] The heat exchange tube 3 is made of wear-resistant and corrosion-resistant steel, and the baffle 21 is made of polypropylene.

[0041] As shown in Figure 5, four adjacent heat exchange tubes 3 in the cross section of the heat exchange tube bundle are arranged in a square, wherein the center distance between two adjacent heat exchange tubes 3 is recorded as P, the ratio of the center distance P to the outer diameter d of the heat exchange tube is recorded as P / d, and the angle between the water flow direction (i.e., the shell-side material flushing direction) and the center line connecting the adjacent heat exchange tubes 3 (i.e., the square edge) is recorded as the inflow angle α, α≤90°. Note: (1) Because the bow-shaped baffle 21 allows the shell-side material to be transported in a serpentine manner, the shell-side material will only flush the heat exchange tube 3 from the upper side to the lower side as shown in the figure, or from the lower side to the upper side as shown in the figure, and the heat exchange tubes 3 are arranged in a square, so no matter which flushing direction is used, the inflow angle α remains unchanged. (2) There are actually two connecting lines between the same heat exchange tube 3 and the adjacent heat exchange tube 3, and the two connecting lines are perpendicular to each other. Therefore, based on the above definition, there are actually two choices for the inflow angle, and the difference between the two inflow angles is 90°. For the convenience of expression, the other inflow angle is recorded as 90°-α. When the inflow angle parameters are actually set, for example, the inflow angle is set to 10°, whether α is set to 10° or 90°-α is set to 10°, because the flow fields generated by the two are symmetrical, the actual performance data such as shell-side resistance and turbulence obtained are also consistent. Therefore, in the present invention, it is not necessary to clearly distinguish which of the two angles is defined as the inflow angle.

[0042] For the above heat exchange tube arrangement optimization:

[0043] S1, the above arrangement is designed and analyzed by Box-Behnken Design (BBD) and Response Surface Method (RSM), so as to obtain the ratio of the center distance of the heat exchange tube 3 to the tube diameter P / d, the inflow angle α, and the shell-side material inlet flow rate U for the shell-side resistance C D and turbulence C L The response relationship between the shell resistance C D The larger the value, the greater the pressure drop between the shell inlet and outlet.L The higher the heat transfer efficiency, the higher the corresponding heat transfer efficiency. Therefore, when designing the arrangement parameters, it is necessary to minimize C D , improve C L The above-mentioned BBD is an existing design method, and RSM is an existing analysis method.

[0044] S2, the second generation genetic algorithm Nondominated Sorting Genetic Algorithm II (NSGAII) was used to optimize the above response relationship with three parameters and two objectives, where the three parameters are P / d, α and U, and the two objectives are C D Minimum, C L Maximum, through optimization, C under different inlet flow rates U D With C L The best value relationship between .

[0045] S3, according to the above optimization results, select C D With C L The values ​​of P / d and α are deduced based on the response relationship.

[0046] Exemplary:

[0047] Figures 6(a) to (c) and 7(a) to (c) show the response surface plots obtained through BBD and RSM analysis.

[0048] like Figure 8 The figure shows the optimization results of NSGA II genetic algorithm. The figure shows that C D With C L The optimal relationship curve between, where any point on the curve is expressed as: D Lower C L What is the maximum value that can be taken? Or vice versa, in this C L Lower C D What is the minimum amount that can be taken?

[0049] When designing the specific arrangement parameters of the heat exchange tube 3, the inlet flow rate U usually has a fixed design value (similar to the rated voltage, rated current, etc.). Therefore, as long as the inlet flow rate U is given, according to the optimization result, the appropriate C D With C L , and then infer the values ​​of P / d and α. For example, Table 1 below shows several exemplary comparative tests, where "NSGA-II" is the C selected according to the optimization results of the NSGA II algorithm. D With C L The “CFD simulation” column is the CFD simulation software measured based on the P / d and α values.D With C L Data. In the three groups of comparative tests, the values ​​of P / d and α in the "front" row of each group are arbitrarily set, and the values ​​of P / d and α in the "back" row are selected according to the optimization results of the present invention. Finally, according to the CFD simulation comparative test, when the inlet flow rate U is 0.1m / s, P / d is 2.1 and α is 22°, the shell resistance is reduced by 6.7% compared with the arbitrarily set tube bundle arrangement parameters; when the inlet flow rate U is 0.2m / s, P / d is 1.25 and α is 14°, the shell resistance can be reduced by 14.4%; when the inlet flow rate U is 0.1m / s, P / d is 1.25 and α is 7°, the shell resistance can be reduced by 25.2%; at the same time, the turbulence in the above three groups of comparative tests has been greatly improved.

[0050] Table 1: Comparative test

[0051]

[0052] The above comparative test shows that the design of the arrangement parameters of the heat exchange tube bundle 3 according to the optimization method of the present invention can effectively reduce the shell side resistance C compared with any arrangement. D , and at the same time increase the turbulence C L , that is, it can achieve an effective optimal balance between pressure drop and heat exchange efficiency.

[0053] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0054] The present invention is not limited to the above-mentioned embodiments. Any obvious improvement, substitution or deformation that can be made by those skilled in the art without departing from the essential content of the present invention belongs to the protection scope of the present invention.

Claims

1. A heat exchange tube arrangement optimization method, characterized in that: The heat exchanger comprises a tube box (1), a cylinder (2) and a heat exchange tube (3), wherein the tube box (1) is respectively connected to both ends of the cylinder (2), a tube sheet (12) is provided between the tube box (1) and the cylinder (2), and a baffle (21) is provided inside the cylinder (2); the heat exchange tube (3) is fixed in the cylinder (2) through the tube sheet (12), and both ends are respectively connected to the tube boxes (1) on both sides; four adjacent heat exchange tubes (3) in the heat exchange tube bundle are arranged in a square, wherein the outer diameter of the heat exchange tube (3) is d, the center distance between adjacent heat exchange tubes (3) is P, and among the four heat exchange tubes (3) arranged in a square, the angle between the center line of two adjacent heat exchange tubes (3) on one side and the flushing direction of the shell side material is an inflow angle α, and α is ≤90°; For the above arrangement: First, obtain the relative values ​​of P / d, α and the shell-side material inlet velocity U for the shell-side resistance C D and turbulence C L The response relationship between them; then C D Minimum, C L The maximum is the goal, and multi-objective optimization is performed; finally, according to the optimization results, C is selected D and C L , and infer the values ​​of P / d and α based on the response relationship.

2. The heat exchange tube arrangement optimization method according to claim 1, characterized in that: The response relationship was obtained by Box-Behnken Design and Response Surface Method analysis.

3. The heat exchange tube arrangement optimization method according to claim 1, characterized in that: The multi-objective optimization is performed using the Nondominated Sorting Genetic Algorithm II genetic algorithm.

4. The heat exchange tube arrangement optimization method according to claim 1, characterized in that: The surface of the heat exchange tube (3) is densely covered with ellipsoidal protrusions, which are arranged in a spiral shape between the front and rear protrusions.

5. The heat exchange tube arrangement optimization method according to claim 4, characterized in that: The height of the protrusion is 0.15d, the center distance between the front and rear protrusions is 2.4d, and the deflection angle between the front and rear protrusions is 45°.

6. The heat exchange tube arrangement optimization method according to claim 5, characterized in that: When the design value of the inlet flow velocity U is 0.1 m / s, the center spacing P between the heat exchange tubes (3) is 2.1 d, and the inflow angle α is 22°; when the design value of the inlet flow velocity U is 0.3 m / s, the center spacing P between the heat exchange tubes (3) is 1.25 d, and the inflow angle α is 14°; when the design value of the inlet flow velocity U is 0.5 m / s, the center spacing P between the heat exchange tubes (3) is 1.25 d, and the inflow angle α is 7°.

7. A heat exchanger, characterized in that: The invention comprises a tube box (1), a cylinder (2) and a heat exchange tube (3), wherein the tube box (1) is respectively connected to two ends of the cylinder (2), a tube sheet (12) is provided between the tube box (1) and the cylinder (2), and a baffle (21) is provided inside the cylinder (2); the heat exchange tube (3) is fixed in the cylinder (2) through the tube sheet (12), and two ends are respectively connected to the tube boxes (1) on both sides, and the heat exchange tube (3) is arranged and arranged by using the heat exchange tube arrangement optimization method according to any one of claims 1 to 6.

8. The heat exchanger according to claim 7, characterized in that: The heat exchanger is a single-shell-pass and double-tube-pass structure.

9. The heat exchanger according to claim 7, characterized in that: The baffles (21) are arcuate baffles, the spacing between adjacent baffles (21) is 0.3D, and the height of the circular segment of the baffle (21) is 0.25D, wherein D is the inner diameter of the cylinder (2).

10. The heat exchanger according to claim 7, characterized in that: The heat exchange tube (3) is made of steel, and the baffle (21) is made of polypropylene.

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