Y-shaped spiral baffle heat exchanger and performance evaluation and structure optimization method thereof

Abstract

The invention belongs to the technical field of shell-and-tube heat exchanger design and manufacturing, and particularly relates to a Y-shaped spiral baffle heat exchanger and a performance evaluation and structure optimization method thereof.The Y-shaped spiral baffle heat exchanger comprises a shell pass pipeline and a plurality of turbulent flow units arranged in the shell pass pipeline, and the multiple turbulent flow units are sequentially connected end to end in the length direction of the shell pass pipeline; each turbulent flow unit comprises two turbulent flow single bodies of the same structure, and the two turbulent flow single bodies are arranged in a central symmetry mode. Each turbulent flow single body comprises a lap joint plate and two surface plates fixedly connected to the lap joint plate, an included angle is formed between the two surface plates, and the lap joint plate and the two surface plates are integrally arranged in a Y shape; with the lap plate as the center, the deflection angle of the plane plate along the transverse section of the shell pass pipeline is alpha, the deflection angle of the plane plate along the longitudinal section of the shell pass pipeline is beta, and the deflection angles alpha and beta are both acute angles. The device can effectively improve the flowing effect of fluid entering the shell pass pipeline, so that the fluid fully participates in the heat exchange process, and the heat exchange efficiency of the heat exchanger is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of design and manufacture of shell and tube heat exchangers, and specifically relates to a Y-type spiral baffle heat exchanger and a performance evaluation and structure optimization method thereof. Background Art

[0002] With the continuous growth of global energy demand and the increasingly urgent energy conservation and emission reduction targets, improving the heat transfer efficiency of heat exchangers and reducing energy losses have become the focus of common concern in industry and academia. Among the many heat exchangers, shell and tube heat exchangers have dominated the market with their strong structure, high reliability, and strong adaptability, and their usage accounts for about 70% of all heat exchangers.

[0003] Traditional shell and tube heat exchangers still have many deficiencies in shell-side heat transfer, and it is difficult to design a reasonable turbulence structure. For example, the use of components such as spiral baffles can cause the fluid to form a more complex flow pattern, thereby improving the overall heat transfer performance. In the process of heat transfer enhancement by spiral baffles, four 1 / 4 fan-shaped baffles are usually used to form a cycle, which is called a four-part spiral baffle heat exchanger in this article, to form a quasi-spiral flow. A common problem with four-part spiral baffle heat exchangers is that there is a triangular leakage area between two adjacent baffles, which will cause some fluids to not fully participate in the heat exchange process, thereby affecting the heat exchange efficiency. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a Y-type spiral baffle heat exchanger and its performance evaluation and structural optimization method, which can effectively improve the flow effect of the fluid entering the shell-side pipeline, so that the fluid can fully participate in the heat exchange process and improve the heat exchange efficiency of the heat exchanger.

[0005] The technical solution of the present invention is: A Y-type spiral baffle heat exchanger and a performance evaluation and structure optimization method thereof, comprising a shell-side pipeline and a plurality of flow disturbance units arranged inside the shell-side pipeline, wherein the plurality of flow disturbance units are sequentially connected end to end along the length direction of the shell-side pipeline; The spoiler unit comprises two spoiler monomers with the same structure, and the two spoiler monomers are centrally symmetrically arranged; The spoiler unit includes a lap plate and two plane plates fixedly connected to the lap plate, an angle is provided between the two plane plates, and the lap plate and the two plane plates are arranged in a Y shape as a whole; With the lap plate as the center, the deflection angle of the plane plate along the transverse section of the shell-side pipeline is α, and the deflection angle along the longitudinal section of the shell-side pipeline is β, and both the deflection angles α and β are acute angles.

[0006] Preferably, the lap plate has an arcuate edge and a straight edge, the plane plate is connected to the straight edge of the lap plate, the farthest distance from the arcuate edge of the lap plate to the straight edge is the lap length L of the lap plate, and the value range of the lap length L is: L is greater than 0 and less than 1 / 3 of the radius of the shell-side pipeline.

[0007] Preferably, the deflection angle α ranges from 15° to 50°.

[0008] Preferably, the deflection angle β is in the range of 30°-45°.

[0009] Preferably, according to the above-mentioned Y-type spiral baffle heat exchanger, a method for evaluating its performance comprises the following steps: In the numerical simulation software, according to the structural characteristics of the Y-type spiral baffle heat exchanger, the structure of the Y-type spiral baffle heat exchanger is simplified and a simplified model of the heat exchanger is constructed; Based on the simplified model of the heat exchanger, the energy conservation equation and momentum conservation equation of the second-order upwind format are used in the numerical simulation software to calculate the convective heat transfer of the turbulent monomer and the fluid entering the shell-side pipeline to determine the Nusselt number. N u; Use the semi-implicit algorithm of the pressure coupling equation group to couple the fluid velocity and pressure entering the shell side pipeline to determine the resistance factor f ; According to the Nusselt number N u and the resistance factor f , determine the comprehensive evaluation factor E The experimental value of In numerical simulation software, the Reynolds number Re The changing pattern of E The reference basis for the change is by changing the Reynolds number Re The initial value of N u and resistance factor f The corresponding output value of the Nusselt number is N u and resistance factor f The corresponding output value of obtains multiple comprehensive evaluation factors E The comprehensive evaluation factor of the Y-type spiral baffle heat exchanger is obtained by E The experimental value of Re The change law of the heat exchanger with four spiral baffles at the same Reynolds number Re Comprehensive evaluation factor obtained under initial conditions E By comparison, the performance advantages of Y-type spiral baffle heat exchanger are evaluated, and the comprehensive evaluation factors are used to evaluate the performance advantages of Y-type spiral baffle heat exchanger. E The structure of the Y-type spiral baffle heat exchanger is optimized based on the experimental values.

[0010] Preferably, the N u is determined by the following formula: , in, h is the heat transfer coefficient, expressed in W / (m 2 K); d 0 is the characteristic length of the shell side pipe, in meters; λ is the thermal conductivity of the fluid, measured in W / (m·K).

[0011] Preferably, the resistance factor f Determined by the following formula: , in, Δp is the shell side pressure drop, in Pa; L is the shell-side tube length of the heat exchanger, in meters; ρ is the fluid density in kg / m 3 ; u It is the average velocity of the shell-side fluid, in m / s.

[0012] Preferably, the comprehensive evaluation factor E Determined by the following formula: , in, N u is the Nusselt number, f is the resistance factor.

[0013] Preferably, according to the performance evaluation of the Y-type spiral baffle heat exchanger, the structure of the Y-type spiral baffle heat exchanger is optimized, and the structure optimization method includes the following steps: In Design-Expert software, the Box-Behnken method was used to construct a prediction model between descriptive factors and response values; In the prediction model, the deflection angles α, β and overlap length L are selected as descriptive factors, and the comprehensive evaluation factor E As the response value, by giving multiple groups of initial values ​​of the descriptive factors, the comprehensive evaluation factor corresponding to each group of initial values ​​is obtained. E The predicted value of E The predicted value change curve; then according to the given multiple groups of initial values ​​of descriptive factors, input the comprehensive evaluation factor corresponding to each group of initial values E The experimental value of E The experimental value change curve of E Compare the predicted value change curve with the experimental value change curve to verify the accuracy of the prediction model; After the prediction model is verified, the comprehensive evaluation factor is obtained through the regression equation simulation of Design-Expert software E The multivariate quadratic regression equation between the prediction and each descriptive factor is constructed, and the optimal model parameters are obtained according to the multivariate quadratic regression equation. The deflection angles α, β and overlap length L are corrected by the optimal model parameters.

[0014] Preferably, the comprehensive evaluation factor E The multivariate quadratic regression equation between the predicted value and each descriptive factor is: , in, E is the predicted value of the comprehensive evaluation factor, A is the deflection angle α ；B is the deflection angle β 、C is the overlap length L.

[0015] Compared with the prior art, the Y-type spiral baffle heat exchanger and the performance evaluation and structure optimization method thereof of the present invention have the following beneficial effects: For the shell flow state, during the use of the Y-type spiral baffle heat exchanger, the streamlines on the cross section of the Y-type spiral baffle heat exchanger show more significant annular flow characteristics, and this area forms a richer vortex structure compared with the cross-sectional streamline diagram of the four-part spiral baffle heat exchanger; for the four-part spiral baffle heat exchanger, when the fluid passes through the baffle, due to the existence of the triangular leakage area, part of the fluid can directly pass through the gap between the baffles without experiencing significant changes in speed or direction, resulting in a relatively weak heat exchange effect for this part of the fluid, and this device A Y-shaped spiral baffle heat exchanger formed by an integral combination of a lap plate and two flat plates is arranged, wherein a deflection angle α of the flat plate along the transverse section of the shell-side pipeline and a deflection angle β of the flat plate along the longitudinal section of the shell-side pipeline are introduced as the lap angle, and an obvious flow velocity reduction area can appear at a position close to the wall of the shell-side pipeline behind the turbulent monomer, which effectively reduces leakage flow, forces the fluid to move more laterally, and can effectively improve the flow effect of the fluid entering the shell-side pipeline, so that the fluid fully participates in the heat exchange process, thereby improving the heat exchange efficiency of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of a Y-type spiral baffle heat exchanger; Figure 2 is a schematic diagram of the structure of the spoiler unit; Figure 3 It is a side view of the spoiler unit; Figure 4 This is a schematic diagram of the distribution of the disturbance unit in the shell-side pipeline; Figure 5It is a reliability verification diagram in the embodiment, and a comparison diagram between simulation value and experimental value; Figure 6 The streamline comparison diagram of the cross section of the Y-type spiral baffle heat exchanger and the four-part spiral baffle heat exchanger at Y=-0.2 and Y=-0.95, where Figure 6 (a) is the cross-sectional streamline diagram of the Y-type spiral baffle heat exchanger. Figure 6 (b) is the cross-sectional streamline diagram of the four-helical baffle heat exchanger; Figure 7 This is a streamline comparison diagram of the Y-type spiral baffle heat exchanger and the four-part spiral baffle heat exchanger in the same longitudinal section. Figure 7 (c) is the longitudinal section streamline diagram of the Y-type spiral baffle heat exchanger. Figure 7 (d) is the longitudinal section streamline diagram of the four-part spiral baffle heat exchanger; Figure 8 Comprehensive evaluation factor E Comparison chart of predicted value and experimental value; Fig. 9 The comprehensive evaluation factors of the Y-type spiral baffle heat exchanger and the four-split spiral baffle heat exchanger before and after optimization E Curve comparison diagram, Y is the comprehensive evaluation factor of Y-type spiral baffle heat exchanger before optimization E The change curve of Y OP Comprehensive evaluation factor after optimization of Y-type spiral baffle heat exchanger E The change curve of QH is the comprehensive evaluation factor of the four-helical baffle heat exchanger E The change curve. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0019] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0020] See also Figures 1 to 3As shown, in order to effectively improve the flow effect of the fluid entering the shell-side pipeline during the heat exchange process, the fluid can fully participate in the heat exchange process and improve the heat exchange efficiency of the heat exchanger. This embodiment provides a Y-type spiral baffle heat exchanger and its performance evaluation and structural optimization method. The Y-type spiral baffle heat exchanger includes a shell-side pipeline and a plurality of spoiler units arranged inside the shell-side pipeline, and the plurality of spoiler units are connected end to end in sequence along the length direction of the shell-side pipeline; the spoiler unit includes two spoiler monomers with the same structure, and the two spoiler monomers are centrally symmetrically arranged; the spoiler monomer includes a lap plate and two plane plates fixedly connected to the lap plate, an angle is provided between the two plane plates, and the lap plate and the two plane plates are arranged in a Y shape as a whole; with the lap plate as the center, the deflection angle of the plane plate along the transverse section of the shell-side pipeline is α, and the deflection angle along the longitudinal section of the shell-side pipeline is β, and the deflection angles α and β are both acute angles. Thus, by designing the deflection angles α and β, the two spoiler units form a spiral period, so that a spiral distribution structure is formed inside the shell-side pipeline along the axial direction under the combination of multiple spoiler units, namely a Y-type spiral baffle structure.

[0021] The specific requirements for the design of lap joints are as follows: The lap plate has an arc edge and a straight edge, the plane plate is connected to the straight edge of the lap plate, the farthest distance from the arc edge of the lap plate to the straight edge is the lap length L of the lap plate, and the value range of the lap length L is: L is greater than 0 and less than 1 / 3 of the radius of the shell side pipe. The value range of the deflection angle α is 15°-50°. The value range of the deflection angle β is 30°-45°. Therefore, the optimal heat exchange effect can be produced by the angle limitation of the deflection angles α and β.

[0022] Specifically, the processing method of the spoiler monomer is as follows: a semicircular plate is first divided into two pieces along one side parallel to the diameter, and then a part with an arc is used as a lap plate, and the other part is separated into two parts along a radius line perpendicular to the semicircular edge as two plane plates. The separated plane plates are bent forward and backward at an angle α along the longitudinal cross-section direction of the pipe with the lap plate as the center, and then cut according to the edge contour line, and finally punched to complete.

[0023] Installation method of Y-type spiral baffle heat exchanger: refer to Figures 1 to 4 As shown, firstly, the first spoiler monomer is positioned in the pipe bundle by using a tie rod and a distance rod, and then the second spoiler monomer is installed; the second spoiler monomer is rotated 180° with respect to the installed first spoiler monomer, and is placed on the right side of the first spoiler monomer according to the longitudinal direction of the pipeline; the positions of the two spoiler monomers are adjusted so that the adjacent parts of the two spoiler monomers overlap and align, and then the tie rod and the distance rod are used to position them, and the above process is repeated to complete the installation of other spoiler monomers until the entire pipeline is installed.

[0024] In order to discuss the influence of the spoiler unit on the shell side of the present invention on the fluid flow heat transfer, a method for evaluating the performance of the spoiler unit is proposed in the design process, as follows: 1. In the numerical simulation software, according to the structural characteristics of the Y-type spiral baffle heat exchanger, the structure of the Y-type spiral baffle heat exchanger is simplified and a simplified model of the heat exchanger is constructed; the simplified conditions of the simplified model of the heat exchanger include: The shell-side fluid domain of the shell and tube heat exchanger is selected as the research object; Ignore the tube structure and heat transfer, and set it to constant wall temperature condition; Ignore the effect of gravity on the fluid and the turbulent monomers; The tube structure and the distance between the heat exchange tube and the shell as well as the flow disturbance monomer are ignored; The solid region is ignored and only the fluid region is studied.

[0025] 2. Based on the simplified model of the heat exchanger, the energy conservation equation and momentum conservation equation of the second-order upwind format are used in the numerical simulation software (CFD) to calculate the convective heat transfer of the turbulent monomer and the fluid entering the shell-side pipeline to determine the Nusselt number. N u.

[0026] 3. Based on the simplified model of the heat exchanger, the semi-implicit algorithm (SIMPLE) of the pressure coupling equations in the numerical simulation software (CFD) is used to couple the velocity and pressure of the fluid entering the shell-side pipeline to determine the resistance factor. f .

[0027] 4. According to the Nusselt number N u and resistance factor f , determine the comprehensive evaluation factor E The experimental value of .

[0028] 5. Use numerical simulation software (CFD) to simulate the simplified model of the heat exchanger (before simulating the simplified model of the heat exchanger, it is necessary to further verify the reliability of the simulation method. Specifically, the simplified model of the heat exchanger is constructed based on the existing experimental results, and the simulation value is obtained by using the same simulation method. The simulation value is compared with the existing experimental value to judge the accuracy of the simulation method, so as to prove that the numerical simulation method is correct and reliable. For example, Figure 5 As shown in Figure 2, when the change curves formed by the predicted value and the experimental value are close, it proves that the simulation calculation method is correct. ), the comprehensive evaluation factor of the Y-type spiral baffle heat exchanger is obtained E With Reynolds number Re (The Reynolds number is a dimensionless number used to describe the flow state of a fluid. The size of the Reynolds number can be used to determine whether the fluid flow state is laminar or turbulent) to determine the comprehensive evaluation factor under different initial conditions EThe comprehensive evaluation factor of the heat exchanger with four spiral baffles under the same initial conditions is E The performance advantage of the Y-type spiral baffle heat exchanger is evaluated by comparison. (In fact, in numerical simulation software, the Reynolds number is used Re The changing pattern of E The reference basis for the change is by changing the Reynolds number Re The initial value of N u and resistance factor f The corresponding output value of the Nusselt number is N u and resistance factor f The corresponding output value of obtains multiple comprehensive evaluation factors E The comprehensive evaluation factor of the Y-type spiral baffle heat exchanger is obtained by E The experimental value of Re The change law of the heat exchanger with four spiral baffles at the same Reynolds number Re Comprehensive evaluation factor obtained under initial conditions E After the performance advantages of the Y-type spiral baffle heat exchanger are compared, further evaluation is performed based on the comprehensive evaluation factors. E The structure of the Y-type spiral baffle heat exchanger is optimized based on the experimental values.

[0029] Specifically, the shell flow state of the Y-type spiral baffle heat exchanger and the four-part spiral baffle heat exchanger is compared as follows: From the cross-sectional streamline diagram Figure 6 (a) It can be observed that in the cross section of the Y-type spiral baffle heat exchanger, the streamlines show more significant annular flow characteristics, and this area is similar to the Figure 6 Compared with the cross-sectional streamline diagram of the four-helical baffle heat exchanger shown in (b), a richer vortex structure is formed.

[0030] From the longitudinal section flow line diagram Figure 7 (d) It can be observed that in the quad-helical baffle heat exchanger, when the fluid passes through the baffles, due to the existence of the triangular leakage area, part of the fluid can directly pass through the gap between the baffles without experiencing significant changes in speed or direction, resulting in a relatively weak heat exchange effect for this part of the fluid. After the overlap (i.e., overlap length L) is introduced, as Figure 7 As shown in (c), it can be observed that there is an obvious flow velocity reduction area near the wall behind the turbulent unit. This is because the overlap design reduces leakage and forces the fluid to move more laterally.

[0031] From the above comparison, it can be seen that the Y-type spiral baffle heat exchanger is a high-efficiency heat exchanger with good shell-side heat transfer performance and effectively reduced leakage area compared to the four-part spiral baffle heat exchanger.

[0032] Furthermore, in determining the Nusselt number N u, it is necessary to use numerical simulation software to analyze the model, and calculate the heat transfer coefficient by using the energy conservation equation and momentum conservation equation of the second-order upwind format in the numerical simulation software. h， and then N u is determined by the following formula: , in, h is the heat transfer coefficient, expressed in W / (m 2 K); d 0 is the characteristic length of the shell side pipe, in meters; λ is the thermal conductivity of the fluid, measured in W / (m·K).

[0033] Furthermore, the resistance factor f Determined by the following formula: , in, Δp is the shell side pressure drop, in Pa; L is the shell-side tube length of the heat exchanger, in meters; ρ is the fluid density in kg / m 3 ; u It is the average velocity of the shell-side fluid, in m / s.

[0034] Furthermore, the comprehensive evaluation factor E Determined by the following formula: , in, N u Nusselt number; f is the resistance factor.

[0035] According to the above-mentioned Y-type spiral baffle heat exchanger and its performance evaluation method, in order to make the heat exchange effect of the Y-type spiral baffle heat exchanger better, the Y-type spiral baffle heat exchanger is structurally optimized as follows. The specific structural optimization method of the Y-type spiral baffle heat exchanger includes the following steps: 1. In Design-Expert software (experimental design and statistical analysis software, i.e. "Experimental Design and Analysis Expert"), the Box-Behnken method is used to design and determine the relationship between descriptive factors and response values.

[0036] 2. Select the deflection angles α, β and overlap length L as descriptive factors (input variables) and the comprehensive evaluation factorE is the response value (output variable). For each input variable, take 3 simulation levels (α angle: 15°, 25°, 35°; β angle: 30°, 35°, 40°; L: 0, 1 / 15, 2 / 15) as the initial value of the descriptive factor. Enter the Design-Expert software respectively, such as Figure 8 As shown in the figure, by giving multiple groups of initial values ​​of the descriptive factors, the comprehensive evaluation factor corresponding to each group of initial values ​​is obtained. E The predicted value of E The predicted value change curve; then according to the given multiple groups of initial values ​​of descriptive factors, input the comprehensive evaluation factor corresponding to each group of initial values E The experimental value of E The experimental value change curve is compared to analyze the significant degree of influence between factors and judge the accuracy of the prediction model.

[0037] 3. Comprehensive evaluation factors are obtained through regression equation simulation using Design-Expert software E The multivariate quadratic regression equation is established between the predicted value and each descriptive factor; and the optimal model parameters are obtained based on the multivariate quadratic regression equation analysis, and the deflection angles α, β and overlap length L are corrected using the optimal model parameters.

[0038] Furthermore, the comprehensive evaluation factor E The multivariate quadratic regression equation between the predicted value and each descriptive factor is: , in, E is the predicted value of the comprehensive evaluation factor, A is the deflection angle α ；B is the deflection angle β 、C is the overlap length L.

[0039] Then the optimized model is simulated and calculated again by CFD method to obtain the comprehensive evaluation factor E The variation law of Reynolds number is shown and verified by experimental values. It is compared with the four-helical baffle heat exchanger. Fig. 9 As shown in the results, it is found that the comprehensive evaluation factor of the optimized Y-type spiral baffle heat exchanger is 5000-15000 when the Reynolds number is E Compared with the traditional four-part spiral baffle heat exchanger, it is improved by nearly 40%.

[0040] The Y-type spiral baffle heat exchanger designed in this scheme has the following advantages: The heat transfer performance of the Y-type spiral baffle heat exchanger is better than that of the traditional four-part spiral baffle heat exchanger.

[0041] The Y-type spiral baffle heat exchanger structure can reduce the fluid leakage area of ​​the four-part spiral baffle heat exchanger.

[0042] The Y-type spiral baffle heat exchanger is relatively simple to manufacture and easy to install.

[0043] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A Y-type spiral baffle heat exchanger, comprising a shell-side pipeline and a plurality of flow disturbance units arranged inside the shell-side pipeline, characterized in that: A plurality of the flow-disturbing units are connected end to end in sequence along the length direction of the shell-side pipeline; The spoiler unit comprises two spoiler monomers with the same structure, and the two spoiler monomers are centrally symmetrically arranged; The spoiler monomer comprises a lap plate and two plane plates fixedly connected to the lap plate, an angle is set between the two plane plates, and the lap plate and the two plane plates are arranged in a Y shape as a whole, and two plane plates close to each other in the two spoiler monomers are fixedly connected, and the connection point of the two plane plates is the symmetry center of the two spoiler monomers; With the lap plate as the center, the deflection angle of the plane plate along the transverse section of the shell-side pipeline is α, and the deflection angle along the longitudinal section of the shell-side pipeline is β, and both the deflection angles α and β are acute angles.

2. A Y-type spiral baffle heat exchanger according to claim 1, characterized in that: The lap plate is an arc-shaped plate, and the edge of the lap plate consists of an arc-shaped edge and a straight edge. The flat plate is connected to the straight edge of the lap plate. The farthest distance from the arc-shaped edge of the lap plate to the straight edge is the lap length L of the lap plate. The value range of the lap length L is: L is greater than 0 and less than 1 / 3 of the radius of the shell-side pipeline.

3. A Y-shaped spiral baffle heat exchanger according to claim 1, characterized in that: The deflection angle α has a value range of 15°-50°.

4. A Y-shaped spiral baffle heat exchanger according to claim 1, characterized in that: The deflection angle β has a value range of 30°-45°.

5. A method for performance evaluation and structural optimization of a Y-type spiral baffle heat exchanger according to any one of claims 1 to 4, characterized in that: The performance evaluation method of the Y-type spiral baffle heat exchanger comprises the following steps: In the numerical simulation software, according to the structural characteristics of the Y-type spiral baffle heat exchanger, the structure of the Y-type spiral baffle heat exchanger is simplified and a simplified model of the heat exchanger is constructed; Based on the simplified model of the heat exchanger, the energy conservation equation and momentum conservation equation of the second-order upwind format are used in the numerical simulation software to calculate the convective heat transfer of the turbulent monomer and the fluid entering the shell-side pipeline to determine the Nusselt number. N u; Use the semi-implicit algorithm of the pressure coupling equation group to couple the fluid velocity and pressure entering the shell side pipeline to determine the resistance factor f ; According to the Nusselt number N u and the resistance factor f , determine the comprehensive evaluation factor E The experimental value of In numerical simulation software, the Reynolds number Re The changing pattern of E The reference basis for the change is by changing the Reynolds number Re The initial value of Nusselt number is obtained N u and resistance factor f The corresponding output value of the Nusselt number is N u and resistance factor f The corresponding output value of obtains multiple comprehensive evaluation factors E The comprehensive evaluation factor of the Y-type spiral baffle heat exchanger is obtained by E The experimental value of Re The change law of the heat exchanger with four spiral baffles at the same Reynolds number Re Comprehensive evaluation factor obtained under initial conditions E By comparison, the performance advantages of Y-type spiral baffle heat exchanger are evaluated, and the comprehensive evaluation factors are used to evaluate the performance advantages of Y-type spiral baffle heat exchanger. E The structure of the Y-type spiral baffle heat exchanger is optimized based on the experimental values.

6. The performance evaluation and structural optimization method of a Y-type spiral baffle heat exchanger according to claim 5, characterized in that: The Nusselt number N u is determined by the following formula: ， in, h is the heat transfer coefficient, expressed in W / (m 2 K); d 0 is the characteristic length of the shell side pipe, in meters; λ is the thermal conductivity of the fluid, measured in W / (m·K).

7. A method for performance evaluation and structural optimization of a Y-type spiral baffle heat exchanger according to claim 6, characterized in that: The resistance factor f Determined by the following formula: ， in, Δp is the shell side pressure drop, in Pa; d 0 is the characteristic length of the shell side pipe, in meters; L is the shell-side tube length of the heat exchanger, in meters; ρ is the fluid density in kg / m 3 ; u It is the average velocity of the shell-side fluid, in m / s.

8. The performance evaluation and structural optimization method of a Y-type spiral baffle heat exchanger according to claim 7, characterized in that: The comprehensive evaluation factor E Determined by the following formula: ， in, N u is the Nusselt number, f is the resistance factor.

9. The performance evaluation and structural optimization method of a Y-type spiral baffle heat exchanger according to claim 5, characterized in that: The structural optimization method of a Y-type spiral baffle heat exchanger comprises the following steps: In Design-Expert software, the Box-Behnken method was used to construct a prediction model between descriptive factors and response values; In the prediction model, the deflection angles α, β and overlap length L are selected as descriptive factors, and the comprehensive evaluation factor E As the response value, by giving multiple groups of initial values ​​of the descriptive factors, the comprehensive evaluation factor corresponding to each group of initial values ​​is obtained. E The predicted value of E The predicted value change curve; then according to the given multiple groups of initial values ​​of descriptive factors, input the comprehensive evaluation factor corresponding to each group of initial values E The experimental value of E The experimental value change curve of E Compare the predicted value change curve with the experimental value change curve to verify the accuracy of the prediction model; After the prediction model is verified to be accurate, the comprehensive evaluation factors are simulated through the regression equation of Design-Expert software. E The multivariate quadratic regression equation is constructed between the predicted value and each descriptive factor, and the optimal model parameters are obtained based on the multivariate quadratic regression equation. The deflection angles α, β and overlap length L are corrected using the optimal model parameters.

10. The performance evaluation and structural optimization method of a Y-type spiral baffle heat exchanger according to claim 9, characterized in that: The comprehensive evaluation factor E The multivariate quadratic regression equation between the predicted value and each descriptive factor is: ， in, E is the predicted value of the comprehensive evaluation factor, A is the deflection angle α ；B is the deflection angle β 、C is the overlap length L.

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