High-temperature radiation furnace tube containing turbulent flow structure and design, preparation and application method thereof

Abstract

The invention discloses a high-temperature radiation furnace tube with a turbulent flow structure and a design, preparation and application method thereof, and belongs to the technical field of high-temperature radiation furnace tubes. The design method comprises the following steps: constructing a calculation model E1 for predicting the influence of geometric parameters of the turbulent flow structure on the pressure drop of the high-temperature radiation furnace tube containing the turbulent flow structure, namely predicting the pressure drop sensitivity of the high-temperature radiation furnace tube containing the turbulent flow structure; the calculation result of the calculation model E1 is limited according to the actual requirement of the application scene of the high-temperature radiation furnace tube containing the turbulent flow structure for the pressure drop sensitivity, and the geometric parameters of the turbulent flow structure meeting the pressure drop sensitivity are obtained. Customized design and optimization can be carried out according to different requirements of the furnace tube on pressure drop, heat exchange performance, outlet temperature and the like under different working conditions, and turbulent flow structure parameters capable of improving the heat exchange efficiency of the furnace tube to the maximum degree can be obtained on the premise that pressure drop control is met.

Description

Technical Field

[0001] This invention relates to the technical field of high-temperature radiant furnace tubes, and particularly to high-temperature radiant furnace tubes with turbulence structures, as well as their design, preparation and application methods. Background Technology

[0002] In ethylene cracking furnaces, the cracking reaction is a high-temperature gas-phase reaction, and its ethylene yield is mainly affected by gas residence time and temperature. Since the cracking reaction is endothermic, continuous heating of the gas inside the furnace tubes is required through the tube walls. To avoid side reactions and ensure a short residence time, the gas velocity inside the cracking furnace tubes is typically maintained at 100-300 m / s, corresponding to a Reynolds number (Re) greater than 10000, indicating a highly turbulent flow. The inner diameter of these furnace tubes is typically 40-200 mm, and the operating temperature range is 800-1100 ℃, while the gas medium temperature is generally between 600-900 ℃.

[0003] Existing furnace tubes mostly use machined surfaces with smooth inner walls. When gas passes through at high speeds, although the main flow exhibits turbulence, the boundary layer region close to the furnace wall has a lower velocity and limited heat transfer effect, resulting in insufficient convective heat transfer efficiency between the inner wall of the furnace tube and the gas. To improve this problem, a common improvement measure is to incorporate turbulence-inducing structures inside the furnace tube, such as spiral blades, fins, or protrusions, to enhance fluid flow around the tube and improve the heat transfer efficiency of the tube wall.

[0004] However, while these internal turbulence structures improve heat transfer efficiency, they also significantly increase flow resistance, leading to a higher pressure drop within the tube. In pressure-drop-sensitive conditions such as ethylene cracking furnaces, excessive pressure drop will cause a decrease in gas flow rate, resulting in increased residence time or uneven distribution, which may lead to over-cracking or uneven reaction. Therefore, precise design of the furnace tube internal structure is required to improve heat transfer efficiency under controllable pressure drop conditions. In pressure-drop-insensitive conditions such as hydrogen conversion furnaces, although a certain increase in pressure drop is permissible, it is still necessary to clarify the relationship between the increase in pressure drop and the improvement in heat transfer efficiency.

[0005] Furthermore, while existing technologies such as CN119425537A have improved heat transfer efficiency and controlled pressure drop to some extent by combining internal surface roughening with micron-level flow around structures, the design of its flow around structure still lacks systematic differentiation and quantitative guidance on pressure drop sensitivity under different operating conditions. In particular, it lacks accurate prediction methods for the coupling behavior of flow and heat transfer under extreme high speed and high temperature conditions, making it difficult to achieve dynamic balance and customized design between pressure drop and heat transfer in different application scenarios such as ethylene cracking, hydrogen production conversion, and iron ore reduction.

[0006] Therefore, how to accurately predict the impact of the internal turbulence structure of the furnace tube on the pressure drop and heat transfer performance, and thereby obtain an optimized design structure that achieves a reasonable balance between enhanced heat transfer and pressure drop control, is a key problem that needs to be solved by existing technologies. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature radiant furnace tube with a turbulence structure and its design, preparation and application methods, in order to solve the problems in existing technologies where the turbulence structure inside the furnace tube leads to a significant increase in pressure drop while improving heat transfer efficiency, and the lack of quantitative and precise control over different pressure drop sensitivity conditions.

[0008] The technical solution of the present invention is as follows: A design method for a high-temperature radiant furnace tube with a turbulence-inducing structure, comprising: A calculation model E1 is constructed to determine the influence of the geometric parameters of the predicted turbulence structure on the pressure drop of the high-temperature radiant furnace tube containing the turbulence structure, i.e., the predicted pressure drop sensitivity of the high-temperature radiant furnace tube containing the turbulence structure. Based on the actual requirements of pressure drop sensitivity in the application scenario of high-temperature radiation furnace tubes with turbulence structures, the calculation results of the calculation model E1 are limited to obtain the geometric parameters of the turbulence structure that meet the pressure drop sensitivity. The computational model E1 is constructed as follows:

[0009] Wherein, ΔP rough This represents the pressure drop ΔP in furnace tubes equipped with turbulence-inducing structures. smooth The pressure drop of the smooth furnace tube is represented by H, the distance from the apex to the bottom center of the turbulence structure (i.e., the radius of the hemispherical turbulence structure), D, the inner diameter of the furnace tube, P, the axial spacing of adjacent turbulence structures on the same axis, N, the total number of turbulence structures covered by the circumference of the furnace tube within the axial spacing of adjacent turbulence structures on the same axis, and π, representing pi. k1, m1, n1, and p1 are fitting parameters with values ​​of k1=178.227, m1=1.117, n1=-1.019, and p1=1.209, respectively. The turbulence structure is hemispherical and is evenly or interlacedly distributed on the inner wall of the high-temperature radiation furnace tube. The geometric parameters of the turbulence structure satisfy D = 40-300mm, H / D = 0.02-0.15, P / D = 0.03-5, and N = 3-48.

[0010] It should be noted that the geometric parameters of the turbulence structure that meet the pressure drop sensitivity described in the above scheme can be a single parameter combination, such as a unique H, D, P and N value, or multiple parameter combinations that meet the calculation requirements, such as multiple sets of H, D, P and N values.

[0011] In the above calculation model, It can be used to approximate the coverage of the circumferential structure. Calculations show that when H / D is 0.05-0.2, the error rate of this approximation is no more than 1%, which can significantly simplify the calculation model and quickly obtain the calculation results.

[0012] The above calculation model of the present invention fully considers that due to the frictional resistance of the inner wall of the furnace tube, a pressure drop will occur between the inlet and outlet of the gas when passing through the furnace tube. The greater the frictional resistance, the higher the corresponding pressure drop. In order to accurately and quantitatively evaluate the influence of the turbulence structure on the pressure drop, the above calculation model uses a smooth furnace tube to obtain the pressure drop ΔP. smooth Based on this, the pressure drop ratio obtained by furnace tubes with turbulence structures and smooth furnace tubes is used to measure the degree of increase in flow resistance caused by different turbulence structures.

[0013] The above calculation model of the present invention fully considers the influence of the geometric parameters of the turbulence structure on the flow characteristics. Specifically, H / D (the ratio of the height of the turbulence structure to the inner diameter of the furnace tube) reflects the relative convexity of the turbulence structure, and P / D (the ratio of the axial spacing of the turbulence structure to the inner diameter of the tube) reflects the sparseness of the turbulence structure arrangement in the axial direction. The term can reflect the combined effect of the number of circumferential disturbance structures and the height of the protrusions. Through the combination of these dimensionless parameters, the coupling relationship between the disturbance structures and flow friction can be accurately and systematically described.

[0014] Furthermore, from a physical perspective, increasing the values ​​of H and N in model E1 significantly enhances boundary layer disturbances and increases the friction factor, leading to a higher pressure drop. Conversely, increasing the values ​​of P and D helps to weaken the disturbance effect and reduce flow resistance. Therefore, this model can not only accurately characterize the influence of different geometric parameters of the disturbance structure on pressure drop, but also provide a reliable prediction tool in engineering design, helping designers to rationally select disturbance structures under pressure drop-sensitive conditions and achieve the optimal balance between improving furnace tube energy efficiency and controlling pressure drop.

[0015] According to some preferred embodiments of the present invention, when the application scenario of a high-temperature radiant furnace tube with a turbulence structure has an extremely sensitive requirement for pressure drop sensitivity, the pressure drop sensitivity is limited to the value obtained according to the calculation model E1. The value of DP satisfies DP < 2; When the application scenario of the high-temperature radiation furnace tube with the turbulence structure requires high sensitivity to pressure drop, the limit is 2≤DP<5; When the application scenario of the high-temperature radiation furnace tube with the turbulence structure requires insensitivity to pressure drop, DP is limited to ≥5.

[0016] According to some preferred embodiments of the present invention, the design method further includes: A computational model E2 is constructed to predict the heat transfer performance of high-temperature radiant furnace tubes containing turbulence structures based on the geometric parameters of the turbulence structure. The calculation results of the calculation model E2 are limited according to the actual requirements of heat transfer performance in the application scenario of the high-temperature radiant furnace tube with turbulence structure, so as to obtain the geometric parameters of the turbulence structure that meet the heat transfer performance. The computational model E2 is constructed as follows:

[0017] Among them, Nu rough Nu represents the Nusselt number of the inner wall of the furnace tube with a turbulence-inducing structure. smooth The value represents the Nusselt number of the inner wall of the smooth furnace tube. k2, m2, n2, and p2 represent the fitting parameters, with values ​​of k2=15.375, m2=0.859, n2=-0.895, and p2=0.773, respectively.

[0018] Similarly, the geometric parameters of the turbulence structure that satisfy the heat transfer performance in the above scheme can be a single parameter combination or multiple parameter combinations.

[0019] The above calculation model E2 of this invention uses the Nusselt number (Nu) as a key indicator for quantitatively evaluating the convective heat transfer capacity of the furnace tube inner wall. This is achieved by using the Nusselt number Nu of the furnace tube inner wall with a turbulence-inducing structure. rough Nusselt number of the smooth inner wall of the furnace tube smoot The ratio between the two values ​​directly reflects the contribution of the turbulence structure to the enhancement of heat transfer. The larger the ratio, the more significant the enhancement of convective heat transfer capacity by the turbulence structure, and the more it helps to improve the heat transfer efficiency of the furnace tube and improve the gas heating effect.

[0020] The calculation model E2 of this invention corresponds to the calculation model E1 regarding voltage drop sensitivity, for example, both using H / D, P / D, and... Dimensionless parameters can comprehensively describe the influence of the geometric parameters of the turbulent structure on the heat transfer characteristics.

[0021] Furthermore, from the physical meaning of model E2, it can be seen that increasing the values ​​of H and N enhances fluid disturbance and turbulence effects, thereby increasing the heat transfer coefficient and leading to an increase in the Nusselt number; while increasing the values ​​of P and D weakens the disturbance effect, reducing the heat transfer enhancement. Using this formula, engineers can quickly predict the extent to which the turbulent structure improves heat transfer under different operating conditions, thus achieving a quantitative balance between energy efficiency improvement and structural optimization.

[0022] According to some preferred embodiments of the present invention, obtaining the geometric parameters of the turbulence structure that satisfy the heat transfer performance includes: under the geometric parameters of the turbulence structure that satisfy the pressure drop sensitivity, taking the maximum value of the calculation model E2 as the heat transfer performance requirement for the application scenario of the high-temperature radiant furnace tube containing the turbulence structure, and obtaining the geometric parameters of the turbulence structure that satisfy the heat transfer performance.

[0023] To verify the accuracy of the above calculation model E2, this invention also provides a model containing Nusselt number Nu. rough The calculation model E3, which predicts the outlet gas temperature of a high-temperature radiant furnace tube containing a turbulence structure based on the geometric parameters of the turbulence structure, is used to determine the Nusselt number (Nu) calculated by model E2 by comparing the predicted temperature obtained from model E3 with the actual temperature or the temperature simulated by software. rough The accuracy.

[0024] The calculation model E3 is as follows;

[0025] Where ΔT represents the difference between the outlet gas temperature and the inlet gas temperature per unit length of furnace tube, i.e., ΔT = T out -T in , among which, T out Indicates the outlet gas temperature of the furnace tube; T wall T represents the temperature of the furnace tube wall. in Nu represents the gas temperature at the furnace tube inlet. rough The value represents the Nusselt number of the inner wall of the furnace tube with the turbulence structure, and L represents the empirical constant used to characterize the degree of increase in the temperature difference between the furnace wall and the gas due to the enhanced heat transfer performance, with a value of L = 0.00004.

[0026] The above calculation model E3 of this invention is based on the heat transfer mechanism of convective heat transfer, and comprehensively considers the furnace tube wall temperature, inlet gas temperature, and friction-through heat transfer capacity (via Nu). rough The influence of parameters can intuitively reflect the temperature evolution of gas during its flow in the pipe.

[0027] The above-mentioned calculation model E3 of this invention fully considers that the change in gas outlet temperature is not only affected by its inlet temperature and furnace tube wall temperature, but also significantly affected by the convective heat transfer capacity along the furnace tube. Therefore, the calculation model E3 reliably characterizes this capacity using the Nusselt number (Nu). Meanwhile, considering that the effect of the turbulence structure on the gas outlet temperature is indirect, mainly by changing the local convective heat transfer coefficient within the furnace tube, thereby affecting the overall temperature change of the gas, this invention does not directly establish a gas outlet temperature calculation model based on the geometric parameters of the turbulence structure.

[0028] The above calculation model E3 of the present invention also reveals the exponential decay characteristics of the gas heat transfer process in the furnace tube: when the heat exchange capacity (Nu) is strong, the temperature difference between the gas and the wall decays rapidly, and the outlet temperature approaches the wall temperature; when Nu is low, the temperature difference decays slowly, and the outlet temperature increases only slightly.

[0029] Based on the above unexpected findings, it can be seen that the combination of models E1, E2 and E3 in this invention can obtain a complete prediction chain for predicting furnace tube pressure drop performance, furnace tube heat transfer performance and furnace tube outlet gas temperature, starting from the geometric parameters of the turbulence structure. This ensures the rationality of the physical mechanism, significantly improves the reliability and engineering applicability of the prediction results, and provides a systematic engineering design method for furnace tube design optimization, energy efficiency assessment and operating condition control.

[0030] According to some preferred embodiments of the present invention, the design method includes: The influence of the geometric parameters of the turbulence structure on the pressure drop of the high-temperature radiant furnace tube containing the turbulence structure is predicted by the calculation model E1, i.e., the pressure drop sensitivity of the high-temperature radiant furnace tube containing the turbulence structure. Based on the actual requirements of pressure drop sensitivity in the application scenarios of high-temperature radiation furnace tubes with turbulence structures, the first constraint condition that the geometric parameters of the turbulence structure based on the calculation model E1 need to satisfy is obtained. The heat transfer performance of high-temperature radiant furnace tubes with turbulence structures is predicted using the computational model E2. Based on the actual requirements of heat exchange performance for the application scenarios of high-temperature radiant furnace tubes with turbulence structures, the second constraint condition that the geometric parameters of the turbulence structure need to satisfy based on the calculation model E2 is obtained. By combining the first constraint, the second constraint, and other constraints related to actual production requirements, the optimization function that the geometric parameters of the disturbance structure need to satisfy is obtained; Solve for the optimal solution of the optimization function to obtain the optimal geometric parameters of the turbulence structure; The turbulence structure is designed based on the optimal geometric parameters of the turbulence structure.

[0031] According to some preferred embodiments of the present invention, the other constraints include: minimum H value, maximum H value, minimum H / D value, maximum H / D value, minimum P / D value, maximum P / D value, minimum N value, and maximum N value of the turbulence structure as defined by manufacturing process capability; minimum D value and maximum D value as defined by production requirements; and minimum H value, maximum H value, minimum H / D value, maximum H / D value, minimum P / D value, maximum P / D value, minimum N value, and maximum N value as defined by corrosion resistance and / or thermal shock resistance requirements of the turbulence structure material.

[0032] The present invention further provides a high-temperature radiant furnace tube with a turbulence structure obtained according to the above design method.

[0033] The present invention further provides a high-temperature radiant furnace tube with a turbulence structure, wherein uniformly or staggeredly distributed hemispherical turbulence structures are provided on the inner wall of the high-temperature radiant furnace tube, and the geometric parameters of the turbulence structure are the optimal geometric parameters of the turbulence structure; the optimal geometric parameters of the turbulence structure are obtained through the following process: The influence of the geometric parameters of the turbulence structure on the pressure drop of the high-temperature radiant furnace tube containing the turbulence structure is predicted by the calculation model E1, i.e., the pressure drop sensitivity of the high-temperature radiant furnace tube containing the turbulence structure. Based on the actual requirements of pressure drop sensitivity in the application scenarios of high-temperature radiation furnace tubes with turbulence structures, the first constraint condition that the geometric parameters of the turbulence structure based on the calculation model E1 need to satisfy is obtained. The heat transfer performance of high-temperature radiant furnace tubes with turbulence structures is predicted using the computational model E2. Based on the actual requirements of heat exchange performance for the application scenarios of high-temperature radiant furnace tubes with turbulence structures, the second constraint condition that the geometric parameters of the turbulence structure need to satisfy based on the calculation model E2 is obtained. By combining the first constraint, the second constraint, and other constraints related to actual production requirements, the optimization function that the geometric parameters of the disturbance structure need to satisfy is obtained; Solve for the optimal solution of the optimization function to obtain the optimal geometric parameters of the turbulence structure; Furthermore, the geometric parameters of the disturbance structure satisfy D = 40-300mm, H / D = 0.02-0.15, P / D = 0.03-5, and N = 3-48.

[0034] The present invention further provides a method for preparing the above-mentioned high-temperature radiation furnace tube with a turbulence structure, wherein the turbulence structure is formed by overlaying with a carburizing-resistant metal powder material, wherein the carburizing-resistant metal powder material is selected from one or more of HP alloy, 35 / 45 alloy, and anti-coking heat-resistant and corrosion-resistant alloy.

[0035] Among them, the anti-carburization metal powder material can be selected according to different application scenarios. For example, for ethylene cracking, it is an anti-coking, heat-resistant and corrosion-resistant alloy, and for hydrogen production conversion furnace, it is HP alloy, 35 / 45 alloy or other heat-resistant and corrosion-resistant alloys similar to the furnace tube base material.

[0036] The present invention further provides a method for applying the above-mentioned high-temperature radiant furnace tube to an ethylene cracking furnace and / or a hydrogen production conversion furnace.

[0037] The present invention has the following beneficial effects: The design method of this invention can obtain the optimized design scheme of furnace tubes with turbulence structure more quickly than the experimental method or numerical simulation method. The design method of the present invention can be customized and optimized according to the different requirements of the furnace tube for pressure drop, heat exchange performance and outlet temperature under different operating conditions. Under the premise of meeting the pressure drop control, a design structure that maximizes the heat exchange efficiency of the furnace tube can be obtained. The design method of this invention can realize the complete correlation from the geometric parameters of the turbulence structure to the engineering performance, and can accurately predict the pressure drop, Nusselt number and outlet temperature of the furnace tube under specific operating conditions, thereby obtaining the optimized design scheme of different turbulence structures. This invention can solve the problem that existing furnace tubes with turbulence structures significantly increase pressure drop while enhancing heat transfer, thus achieving a balance between enhanced heat transfer and pressure drop control, thereby improving reaction performance. The design method or the resulting furnace tube of this invention can be applied under various operating conditions and can be flexibly adjusted according to pressure drop sensitivity. Attached Figure Description

[0038] Figure 1 Figure (a) is a three-dimensional view of the inner surface of the sample with uniformly distributed turbulence structure, (b) is a cross-sectional view of the sample with uniformly distributed turbulence structure, (c) is an unfolded view of the inner surface of the sample with uniformly distributed turbulence structure, (d) is an unfolded view of the inner surface of the sample with interleaved turbulence structure, and (e) is a schematic diagram of the morphology of a single turbulence structure. Figure 2 The sample obtained in the embodiment of the present invention is a physical example diagram; Figure 3 This is a comparison chart of the CFD simulated pressure drop ratios of samples 1-17 obtained in Example 2 and the pressure drop ratios calculated by model E1. Figure 4 This is a comparison chart of the CFD simulation Nusselt number ratios of samples 1-17 obtained in Example 2 and the Nusselt number ratios calculated by model E2; Figure 5 This is a comparison chart of the CFD simulated outlet-inlet gas temperature difference of samples 1-17 obtained in Example 2 and the outlet-inlet gas temperature difference calculated by model E3; Figure 6 This is a schematic diagram of the test apparatus in Example 3. Detailed Implementation

[0039] The technical solutions of the present invention will be further described below with reference to the embodiments and accompanying drawings. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] The turbulence structure set in the following embodiments is shown in the attached figure. Figure 1 , 2 As shown.

[0041] The meanings of the parameters in the following embodiments are as follows: D represents the inner diameter of the furnace tube, H represents the distance from the apex to the center of the bottom of the turbulence structure, i.e., the radius of the hemispherical turbulence structure, and P represents the axial spacing between adjacent turbulence structures on the same axis (when the turbulence structures are uniformly distributed, it is the axial spacing between the two turbulence structures that are closest to each other in the axial direction, as shown in the attached figure). Figure 1 As shown in (c); when the perturbation structures are staggered, their spacing is significantly greater than the axial distance Q between the two closest perturbation structures, as shown in the attached figure. Figure 1 As shown in (d); N represents the total number of turbulence structures covered by the furnace tube circumference within the axial spacing of adjacent turbulence structures located on the same axis, and Coverage represents the total circumferential coverage of turbulence structures within a unit axial length of the furnace tube circumference. .

[0042] The computational models E1, E2, and E3 used are as follows: E1:

[0043] Wherein, ΔP rough This represents the pressure drop ΔP in furnace tubes equipped with turbulence-inducing structures. smooth This indicates the pressure drop across the smooth furnace tube. The pressure drop ratio is represented by H, the distance from the apex to the center of the bottom of the turbulence structure is represented by D, the inner diameter of the furnace tube is represented by P, the axial spacing of the turbulence structures is represented by N, the number of turbulence structures in the circumferential direction of the furnace tube within the axial spacing of adjacent turbulence structures on the same axis is represented by π, and k1, m1, n1, and p1 are the fitting parameters, with values ​​of k1=178.227, m1=1.117, n1=-1.019, and p1=1.209, respectively. E2:

[0044] Among them, Nu rough Nu represents the Nusselt number of the inner wall of the furnace tube with a turbulence-inducing structure. smooth The Nusselt number represents the inner wall of a smooth furnace tube. The ratio of the number of Nusselt numbers is given by k2, m2, n2, and p2, which are the fitting parameters with values ​​of k2=15.375, m2=0.859, n2=-0.895, and p2=0.773, respectively. E3:

[0045] Where ΔT represents the temperature difference between the outlet gas and the inlet gas per unit length of furnace tube, i.e., the outlet temperature difference. wall T represents the temperature of the furnace tube wall. in Nu represents the gas temperature at the furnace tube inlet. rough The value represents the Nusselt number of the inner wall of the furnace tube with the turbulence structure, and L represents the empirical constant used to characterize the degree of increase in the temperature difference between the furnace wall and the gas due to the enhanced heat transfer performance, with a value of L = 0.00004.

[0046] Example 1: Furnace tube samples 1-17 were obtained as shown in Table 1 (where Q > 0 indicates an alternating distribution of turbulence structures): Table 1 Geometric parameters of the turbulence structure of the sample

[0047] Example 2: Numerical simulations of the smooth tube and the sample from Example 1 were performed using Fluent software based on fluid dynamics (CFD) methods. This allowed for a systematic analysis of the influence of the geometric parameters of different turbulence structures on flow resistance and heat transfer performance in Example 1 without relying on a large number of experimental prototypes.

[0048] The simulation parameters are as follows: total furnace tube length 1000 mm, inner diameter 50 mm, gas inlet velocity 160 m / s, inlet temperature 600 ℃; tube wall material is stainless steel, surface micro-roughness height is approximately 1×10⁻⁶. −6 m can be approximated as a smooth tube; the tube wall temperature is constant at 900℃, and the SST k-ω model is selected as the turbulence model, which combines... k-ε and k-ω The model's advantage lies in its performance near the wall. k-ω The model transitions to a free-flow region. k-ε This model is suitable for complex flows with boundary layer separation, strong pressure gradients, and vortex structures. It can calculate turbulent kinetic energy, specific dissipation rate, and the distribution of flow field parameters such as velocity, pressure, and temperature. It offers high accuracy in near-wall flow prediction, simultaneously and accurately capturing the turbulent characteristics of both the viscous sublayer and the free flow region at the wall. In engineering, it is commonly used to predict frictional drag, heat transfer coefficient, and wall heat transfer characteristics.

[0049] The simulation setup also includes: in mesh generation and near-wall treatment, a boundary layer expansion layer is used to generate a progressively finer mesh on the wall. The expansion layer is set to 15 layers, with the initial layer thickness allowing y⁺ to be controlled around 1, and the growth rate controlled at 1.1. The expansion layer is sufficient to cover the velocity and thermal boundary layer thickness to ensure the accuracy of the friction factor and Nusselt number (Nu) calculations. The mesh is further refined in local turbulence protrusions to avoid numerical errors caused by geometric abrupt changes.

[0050] In the simulation, calculations were first performed on a smooth tube without any turbulence structures to obtain baseline values ​​for pressure drop and heat transfer performance, and to verify the rationality of the numerical model and boundary conditions selected in this embodiment. The simulation results show that the pressure drop of the smooth tube is approximately 2930 Pa, and the outlet gas temperature rise is approximately 30 °C, which is consistent with the calculation results of the model in this invention.

[0051] Furthermore, under the same numerical model and boundary conditions, CFD simulations were performed on samples 1-17 of Example 1 to obtain the CFD simulated Nusselt number (CFD-Nusser number), CFD simulated pressure drop (CFD-pressure drop), CFD simulated Nusselt number ratio (CFD-Nusser number ratio), CFD simulated pressure drop ratio (CFD-pressure drop ratio), and CFD simulated outlet temperature difference (CFD-outlet temperature difference). These results were compared with the pressure drop ratio (E1-pressure drop ratio), Nusselt number ratio (E2-Nusser number ratio), and outlet temperature difference (E3-outlet temperature difference) calculated by models E1, E2, and E3 according to the present invention. The results are shown in Table 2 and Appendix. Figure 3 , 4 As shown in Figure 5 ( Figure 5 The temperature difference between the outlet and the outlet is expressed as the temperature rise at the outlet by ΔT.

[0052] Table 2 Comparison of simulated and calculated values ​​for the samples

[0053] As shown in Figure 3, when the pressure drop ratio is in the range of 1-2.5, the calculation results of model E1 are in good agreement with the CFD simulation values. The trends of the pressure drop ratio obtained by both models with the structural parameters (H / D, P / D, N·2H / πD) are basically consistent, and the numerical deviation is small. When the pressure drop ratio is in the range of 2.5-5.5, the numerical deviation between the two models increases, but the overall trend remains consistent. In addition, comparing Implementations 9 and 10, the only difference between them is whether the arrangement of the flow structure is staggered. The CFD simulation results show that the pressure drop data are very close, and model E1 can also accurately predict the results of the two different arrangements. Therefore, model E1 can effectively predict the influence of different geometric parameters of the flow structure and different arrangements on the pressure drop ratio.

[0054] As shown in Figure 4, when the pressure drop ratio is in the range of 1-1.6, the calculation results of model E2 show good consistency with the CFD simulation values. The Nusselt number ratios obtained by both models show basically the same trend with the structural parameters (H / D, P / D, N·2H / πD), with small numerical deviations. However, when the pressure drop ratio is in the range of 1.6-3, the difference between the two models increases. This indicates that as the flow intensity increases, the flow structure becomes more complex, and both CFD simulations and empirical models may have some deviations in their predictions of the actual situation, but these deviations are still within a reasonable range. Comparing Implementations 9 and 10, the only difference is whether the arrangement of the flow structure is staggered. The CFD simulation results show that the Nusselt number ratios are basically the same, and model E2 can also accurately predict the results of the two different arrangements. In summary, model E2 can effectively predict the influence of different geometric parameters of the turbulent structure on the Nusselt number ratio.

[0055] As shown in Figure 5, under the same gas inlet temperature (600 ℃), the gas outlet temperature increases by approximately 30–80 ℃ depending on the geometric parameters of the turbulence structure. This temperature increase is mainly determined by the Nusselt number ratio, which is influenced by the combined effects of the geometric parameters H / D, P / D, and N·2H / πD of the turbulence structure. The comparison between the CFD and E3 results shows good consistency, further validating the accuracy of model E2 in predicting the Nusselt number ratio and model E3 in predicting the outlet temperature difference.

[0056] Example 3: Laboratory tests were conducted on samples 1, 3, and 4 of Example 1, which have typical turbulence structure parameters. The testing apparatus is shown in the attached figure. Figure 6 As shown, it includes: a sample furnace tube 1 installed in a high-temperature furnace 3, a preheating furnace tube 2 connected to the inlet end of the sample furnace tube 1, and a cooling furnace tube 4 connected to its outlet end. The preheating furnace tube 2 and the cooling furnace tube 4 have the same inner diameter and wall thickness as the sample furnace tube 1, the only difference being that the preheating furnace tube 2 and the cooling furnace tube 4 are smooth tubes without a turbulence structure. The preheating furnace tube 2 is connected to a blower 11 through an inlet elbow 7, and the cooling furnace tube 4 is connected to the outside through an outlet elbow 8. An inlet temperature and pressure measuring device 5 and an inlet furnace tube surface thermocouple 10 are installed between the preheating furnace tube 2 and the sample furnace tube 1, and an outlet temperature and pressure measuring device 6 and an outlet furnace tube surface thermocouple 9 are installed between the cooling furnace tube 4 and the sample furnace tube 1. The sample furnace tube 1 has a length of 1000 mm, an outer diameter of 64 mm, an inner diameter of 50 mm, and the turbulence structure is formed by HP high-temperature alloy powder overlay welding.

[0057] In the above device, the preheating furnace tube 2 and the cooling furnace tube 4 can be used to heat and cool the gas respectively, which can ensure the temperature uniformity of the sample furnace tube 1. During the test, the length of the preheating furnace tube 2 in the high temperature furnace 3 is adjusted by moving the position of the high temperature furnace 3 up and down, thereby adjusting the inlet temperature of the gas at the sample inlet.

[0058] The testing process was as follows: The inlet gas velocity was maintained at 160 m / s using blower 11. The furnace tubes were heated by high-temperature furnace 3 until the temperatures measured by thermocouples 9 and 10 on the inlet and outlet tube surfaces reached 900±5℃. The inlet gas temperature measured by inlet temperature and pressure measuring device 5 was 600±5℃. The pressure and temperature data of the outlet gas of different sample furnace tubes were recorded by outlet temperature and pressure measuring device 6. Based on the recorded data, the pressure drop, pressure drop ratio, and temperature difference between the outlet gas temperature and the inlet gas temperature of sample furnace tube 1 were calculated, i.e., the measured pressure drop, measured pressure drop ratio, and measured outlet temperature difference. The results are shown in Table 3 below. Table 3. Measured results of samples 3 and 4

[0059] The measured pressure drop ratio and measured outlet temperature were compared with the pressure drop ratio and outlet temperature difference calculated by models E1, E2, and E3 according to the present invention, and the simulated pressure drop ratio and simulated outlet temperature difference obtained by the CFD simulation method according to Example 2 (as shown in Table 2). The results show that the measured values ​​are all on the same order of magnitude as the model prediction results and CFD numerical simulation results of the present invention, and the trend of change is highly consistent. The results obtained are basically in agreement, which verifies the correctness and engineering feasibility of the model established by the present invention.

[0060] Example 4: Under the conditions of furnace tube inner diameter D=50 mm and inlet gas velocity of 160 m, based on actual production capacity (the minimum thickness of the overlay process is about 1 mm, corresponding to a minimum H / D value of 0.02) and material requirements (the turbulence structure will be subject to erosion and corrosion during use; to minimize the impact of erosion and corrosion, a maximum H / D value of 0.14, a P / D value of 0.3-6, and an N value of 3-12 are set), the geometric parameters of the turbulence structure are designed according to different pressure drop sensitivities, including: Divide the ranges of H / D, P / D, and N into equal parts, for example, 20 parts each, to obtain 20×20×20=8000 parameter combinations; The 8,000 parameter combinations were screened using model E1 to obtain a parameter set that meets the pressure drop sensitivity requirements; By using model E2, a parameter set close to the optimal solution is selected from the parameter set that meets the pressure drop sensitivity requirement, and multiple sets of optimal turbulence structure geometric parameters are obtained.

[0061] Among them, for conditions where the pressure drop sensitivity is extremely high (DP < 2), such as certain ethylene cracking furnace tubes, the optimal turbulence structure geometric parameters obtained through the above process are shown in Table 4, combinations a and b below: Table 4 Optimal turbulence structure parameters under extremely pressure drop sensitive conditions

[0062] The above optimal structural parameters can significantly improve the Nusselt number while achieving a low pressure drop, thus achieving a balance between enhanced heat transfer and pressure drop control.

[0063] Other better (i.e., Nusselt number ratio close to the maximum) spoiler structure parameters include H / D=0.08, P / D=3.4, N=9 (Nusselt number ratio of 1.36); H / D=0.1, P / D=4.1, N=11 (Nusselt number ratio of 1.45); and H / D=0.08, P / D=2.8, N=9 (Nusselt number ratio of 1.43).

[0064] Under the condition of relatively high pressure drop sensitivity (2≤DP<5), the optimal geometric parameters of the turbulence structure obtained through the above process are shown in Table 5 below, combinations c and d: Table 5 Optimal turbulence structure parameters under pressure drop sensitive operating conditions

[0065] The above optimal structural parameters can achieve a higher Nusselt number and higher heat exchange efficiency with a moderate increase in pressure drop, and are suitable for operating conditions with high tolerance for pressure drop.

[0066] Other superior perturbation structure parameters include H / D=0.14, P / D=3.4, N=10 (Nusser number ratio of 1.8); H / D=0.11, P / D=2.8, N=11 (Nusser number ratio of 1.8); and H / D=0.06, P / D=1.6, N=21 (Nusser number ratio of 1.7).

[0067] Under the condition that the pressure drop sensitivity is insensitive (DP≥5), the optimal geometric parameters of the turbulence structure obtained through the above process are shown in Table 6 below, as combined with e: Table 6 Optimal turbulence structure parameters under pressure drop insensitive operating conditions

[0068] The above optimal structural parameters can maximize the Nusselt number and achieve enhanced convective heat transfer efficiency without strict constraints on pressure drop.

[0069] Other better turbulence structure parameters include H / D=0.13, P / D=0.3, N=10 (Nusser number ratio of 7.4); H / D=0.11, P / D=0.3, N=11 (Nusser number ratio of 6.8).

[0070] It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A design method for a high-temperature radiant furnace tube with a turbulence-inducing structure, characterized in that, It includes: A calculation model E1 is constructed to determine the influence of the geometric parameters of the predicted turbulence structure on the pressure drop of the high-temperature radiant furnace tube containing the turbulence structure, i.e., the predicted pressure drop sensitivity of the high-temperature radiant furnace tube containing the turbulence structure. Based on the actual requirements of pressure drop sensitivity in the application scenario of high-temperature radiation furnace tubes with turbulence structures, the calculation results of the calculation model E1 are limited to obtain the geometric parameters of the turbulence structure that meet the pressure drop sensitivity. The computational model E1 is constructed as follows: ； Wherein, ΔP rough This represents the pressure drop ΔP in furnace tubes equipped with turbulence-inducing structures. smooth The pressure drop of the smooth furnace tube is represented by H, the distance from the apex to the center of the bottom of the turbulence structure is represented by D, the inner diameter of the furnace tube is represented by P, the axial spacing of adjacent turbulence structures on the same axis is represented by N, the total number of turbulence structures covered by the circumference of the furnace tube within the axial spacing of adjacent turbulence structures on the same axis is represented by π, and k1, m1, n1, and p1 are the fitting parameters, with values ​​of k1=178.227, m1=1.117, n1=-1.019, and p1=1.209, respectively. The turbulence structure is hemispherical and is evenly or interlacedly distributed on the inner wall of the high-temperature radiation furnace tube. The geometric parameters of the turbulence structure satisfy D = 40-300mm, H / D = 0.02-0.15, P / D = 0.03-5, and N = 3-48.

2. The design method for high-temperature radiant furnace tubes according to claim 1, characterized in that, When the application scenario of a high-temperature radiant furnace tube with a turbulence-inducing structure has an extremely sensitive requirement for pressure drop sensitivity, the requirement is limited to the value obtained from the calculation model E1. The value of DP satisfies DP < 2; When the application scenario of the high-temperature radiation furnace tube with the turbulence structure requires high sensitivity to pressure drop, the limit is 2≤DP<5; When the application scenario of the high-temperature radiation furnace tube with the turbulence structure requires insensitivity to pressure drop, DP is limited to ≥5.

3. The design method for high-temperature radiant furnace tubes according to claim 1, characterized in that, It also includes: A computational model E2 is constructed to predict the heat transfer performance of high-temperature radiant furnace tubes containing turbulence structures based on the geometric parameters of the turbulence structure. The calculation results of the calculation model E2 are limited according to the actual requirements of heat transfer performance in the application scenario of the high-temperature radiant furnace tube with turbulence structure, so as to obtain the geometric parameters of the turbulence structure that meet the heat transfer performance. The computational model E2 is constructed as follows: ； Among them, Nu rough Nu represents the Nusselt number of the inner wall of the furnace tube with a turbulence-inducing structure. smooth The value represents the Nusselt number of the inner wall of the smooth furnace tube. k2, m2, n2, and p2 represent the fitting parameters, with values ​​of k2=15.375, m2=0.859, n2=-0.895, and p2=0.773, respectively.

4. The design method for high-temperature radiant furnace tubes according to claim 3, characterized in that, It includes: Under the geometric parameters of the turbulence structure that satisfy pressure drop sensitivity, the maximum value of the calculation model E2 is used as the heat transfer performance requirement for the application scenario of the high-temperature radiant furnace tube with the turbulence structure, and the geometric parameters of the turbulence structure that satisfy the heat transfer performance are obtained.

5. The design method according to claim 1, characterized in that, It includes: The influence of the geometric parameters of the turbulence structure on the pressure drop of the high-temperature radiant furnace tube containing the turbulence structure is predicted by the calculation model E1, i.e., the pressure drop sensitivity of the high-temperature radiant furnace tube containing the turbulence structure. Based on the actual requirements of pressure drop sensitivity in the application scenarios of high-temperature radiation furnace tubes with turbulence structures, the first constraint condition that the geometric parameters of the turbulence structure based on the calculation model E1 need to satisfy is obtained. The heat transfer performance of high-temperature radiant furnace tubes with turbulence structures is predicted using the computational model E2. Based on the actual requirements of heat exchange performance for the application scenarios of high-temperature radiant furnace tubes with turbulence structures, the second constraint condition that the geometric parameters of the turbulence structure need to satisfy based on the calculation model E2 is obtained. By combining the first constraint, the second constraint, and other constraints related to actual production requirements, the optimization function that the geometric parameters of the disturbance structure need to satisfy is obtained; Solve for the optimal solution of the optimization function to obtain the optimal geometric parameters of the turbulence structure; The turbulence structure is designed based on its optimal geometric parameters: in, The calculation model E2 is shown below: ； Among them, Nu rough Nu represents the Nusselt number of the inner wall of the furnace tube with a turbulence-inducing structure. smooth The value represents the Nusselt number of the inner wall of the smooth furnace tube. k2, m2, n2, and p2 represent the fitting parameters, with values ​​of k2=15.375, m2=0.859, n2=-0.895, and p2=0.773, respectively.

6. The design method according to claim 5, characterized in that, The other constraints include: minimum H value, maximum H value, minimum H / D value, maximum H / D value, minimum P / D value, maximum P / D value, minimum N value, and maximum N value of the turbulence structure as defined by the manufacturing process capability; minimum D value and maximum D value as defined by production requirements; and minimum H value, maximum H value, minimum H / D value, maximum H / D value, minimum P / D value, maximum P / D value, minimum N value, and maximum N value as defined by the corrosion resistance and / or thermal shock resistance requirements of the turbulence structure material.

7. A high-temperature radiant furnace tube with a turbulence structure obtained by the design method according to any one of claims 1-6.

8. A high-temperature radiant furnace tube with a turbulence-inducing structure according to claim 7, characterized in that, The high-temperature radiant furnace tube has uniformly or staggeredly distributed hemispherical turbulence structures on its inner wall. The geometric parameters of the turbulence structures are the optimal geometric parameters of the turbulence structures. The optimal geometric parameters of the turbulence structures are obtained through the following process: The influence of the geometric parameters of the turbulence structure on the pressure drop of the high-temperature radiant furnace tube containing the turbulence structure is predicted by the calculation model E1, i.e., the pressure drop sensitivity of the high-temperature radiant furnace tube containing the turbulence structure. Based on the actual requirements of pressure drop sensitivity in the application scenarios of high-temperature radiation furnace tubes with turbulence structures, the first constraint condition that the geometric parameters of the turbulence structure based on the calculation model E1 need to satisfy is obtained. The heat transfer performance of high-temperature radiant furnace tubes with turbulence structures is predicted using the computational model E2. Based on the actual requirements of heat exchange performance for the application scenarios of high-temperature radiant furnace tubes with turbulence structures, the second constraint condition that the geometric parameters of the turbulence structure need to satisfy based on the calculation model E2 is obtained. By combining the first constraint, the second constraint, and other constraints related to actual production requirements, the optimization function that the geometric parameters of the disturbance structure need to satisfy is obtained; Solve for the optimal solution of the optimization function to obtain the optimal geometric parameters of the turbulence structure; The calculation model E1 is shown below: ； Wherein, ΔP rough This represents the pressure drop ΔP in furnace tubes equipped with turbulence-inducing structures. smooth The pressure drop of the smooth furnace tube is represented by H, the distance from the apex to the center of the bottom of the turbulence structure is represented by D, the inner diameter of the furnace tube is represented by P, the axial spacing of adjacent turbulence structures on the same axis is represented by N, the total number of turbulence structures covered by the circumference of the furnace tube within the axial spacing of adjacent turbulence structures on the same axis is represented by π, and k1, m1, n1, and p1 are the fitting parameters, with values ​​of k1=178.227, m1=1.117, n1=-1.019, and p1=1.209, respectively. The calculation model E2 is shown below: ； Among them, Nu rough Nu represents the Nusselt number of the furnace tubes equipped with turbulence-inducing structures. smooth The value represents the Nusselt number of the smooth furnace tube, and k2, m2, n2, and p2 represent the fitting parameters, with values ​​of k2=15.375, m2=0.859, n2=-0.895, and p2=0.773, respectively. Furthermore, the geometric parameters of the disturbance structure satisfy D = 40-300mm, H / D = 0.02-0.15, P / D = 0.03-5, and N = 3-48.

9. The method for preparing a high-temperature radiant furnace tube with a turbulence-inducing structure as described in claim 7 or 8, characterized in that, It includes: The turbulence structure is formed by overlaying with a carburizing-resistant metal powder material, wherein the carburizing-resistant metal powder material is selected from one or more of HP alloy, 35 / 45 alloy, and anti-coking, heat-resistant, and corrosion-resistant alloy.

10. The application of the high-temperature radiant furnace tube with turbulence structure as described in claim 7 or 8 in ethylene cracking furnaces and / or hydrogen production conversion furnaces.

Images