Series coupling type vortex enhanced heat transfer tube and cracking furnace

Abstract

The invention relates to the technical field of fluid heat transfer, and discloses a series coupling type vortex enhanced heat transfer tube and a cracking furnace, the series coupling type vortex enhanced heat transfer tube comprises a hollow tubular tube body, and the inner wall of the tube body is provided with a rotational flow generating mechanism extending in the axial direction of the tube body; a vortex generator is arranged at the position, away from the inner wall of the pipe body, of the downstream side of the rotational flow generating mechanism, and a fluid attack angle exists between the vortex generator and the flowing direction of fluid. According to the series coupling type vortex enhanced heat transfer tube provided by the invention, a flow field structure of rigid rotational flow built-in precession type secondary vortex can be formed on the premise of not losing the rotational flow strength of fluid near the tube wall, so that the heat-mass transfer process between the fluid near the tube wall and the fluid in the central area is promoted to be orderly, stably and accurately regulated and controlled; therefore, deep matching of fluid flow-heat exchange-reaction characteristics is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fluid heat transfer technology, in particular to a series coupling type vortex enhanced heat transfer pipe and a cracking furnace. BACKGROUND

[0002] The heat transfer of fluid in the pipe is a common process in the process industry, and the development of related enhanced heat transfer technology has great practical significance for improving the heat transfer effect (rate, intensity and uniformity), promoting industrial production upgrading and energy saving, and thus improving energy utilization efficiency. The heat transfer process in the pipe includes two aspects: one is to destroy and thin the boundary layer to promote the heat transfer between the pipe wall and the fluid near the wall; the other is to strengthen the heat exchange between the fluid in the center region and the fluid near the wall. Among them, the former restricts the heat transfer intensity of the fluid, and the latter determines the heat transfer rate and uniformity of the fluid. Over the years, scholars in the industry have developed a variety of enhanced heat transfer equipment technologies such as elliptical pipe, plum blossom pipe, ribbed pipe, external nail head pipe, finned pipe, twisted pipe, twisted groove pipe, spiral groove pipe, shrink-expand pipe, spiral ribbon, vortex generator and the like from the perspectives of reactor and internal components, in order to improve the heat transfer effect of fluid in the pipe by increasing the heat transfer area or improving the convective heat transfer coefficient. Among the above-mentioned enhanced heat transfer equipment technologies, the plug-in internal component with simple structure, miniaturization, easy implementation and easy to induce longitudinal rotational flow has attracted widespread attention. In fact, rotational flow is an ideal fluid disturbance behavior, which can effectively thin the fluid boundary layer at the heat transfer pipe wall by using high-speed rotational flow to form a large radial pressure gradient and high tangential shear velocity, greatly improving the heat transfer flux while maintaining good heat transfer uniformity.

[0003] In the prior art, helical ribbon is considered as an ideal rotary / vortex generating mechanism. US4466567 discloses a technical solution of welding a solid ribbon on the inner wall of a heat transfer tube, which first proposes a helical ribbon configuration. US005850831A discloses a helical ribbon configuration with alternating changes in twist ratio, which is used to enhance the heat transfer performance of a solar heat receiving tube. US006615911B1 discloses a helical ribbon with a transverse louver grid, which can improve the cooling effect of an electrical appliance when connected to the inner wall of a liquid cooling pipe. US4832114 discloses a ribbon structure with an axial narrow slot, but it is fixed to the rotating shaft transmission member of the heat transfer tube shaft, which is greatly limited in application conditions. US20200271402 A1 discloses a helical ribbon with asymmetric arrangement and small radial size for wall connection, which greatly reduces fluid resistance, but this configuration is essentially a special type of hollow helical ribbon disclosed in US4466567. US4119390 discloses a helical ribbon for an open liquid cooling channel of a gas turbine blade, which has openings staggered along the axial direction on the outer edge. US20110094721 A1 discloses a ribbon configuration composed of rectangular vortex generators, which is arranged in the central region of the heat transfer tube and can efficiently induce vortexes to obtain heat transfer enhancement effect. US9676689B2 discloses a helical ribbon with openings. US20140127091 A1 discloses a hollow helical ribbon configuration with openings.

[0004] In order to overcome the thermal stress effect between the helical ribbon and the heat transfer tube, CN109724444B, CN109724446B, and CN109724448B disclose a helical structure composed of multiple fins. CN112745884B discloses a combination of a ribbon and a fin to inhibit coking and carburizing behavior of the heat transfer tube wall. Xu Fang et al. (Applied Thermal Engineering, 2022, 207:118170) propose a helical ribbon with sawtooth openings on the outer edge to enhance wall disturbance and promote heat transfer. Wang Juan et al. (Process Engineering, 2020, 20(05):510-520) propose a helical ribbon with sawtooth openings on the inner edge, but this configuration increases fluid turbulence at the cost of severe energy dissipation, which does not significantly improve the heat transfer enhancement effect of the fluid downstream of the helical ribbon.

[0005] Further, the above spiral ribbon configuration generally has the following four problems in the industrial heat transfer enhancement application: 1) the fluid mechanics characteristics and heat transfer characteristics under the action of the spiral ribbon are difficult to be deeply matched and coupled, the spiral ribbon makes the fluid form a high-strength rigid rotational flow, and forms a severe shearing and scouring action on the pipe wall, can effectively thin and damage the laminar boundary layer, and promote the effective input of the heat outside the pipe or the pipe wall to the fluid near the pipe wall, but cannot regulate the radial velocity vector to take into account the heat exchange between the fluid in the center area and the fluid near the wall, resulting in a large radial temperature gradient, and the heat exchange efficiency and uniformity are difficult to guarantee. 2) the problem of reliable and reasonable arrangement of the spiral ribbon in the heat transfer pipe. The arrangement of the spiral ribbon in the heat transfer pipe generally includes two kinds of being arranged in the center area of the pipe and being directly connected to the pipe wall, wherein the former needs to introduce a support member, resulting in a decrease in the fluid flow area; the latter is simple and reliable, but stress and strain effects are easily generated between the spiral ribbon and the pipe wall, especially under the action of high-speed impact, long-period stable operation cannot be guaranteed, and it is difficult to adapt to complex and harsh working conditions. 3) For the fouling heat exchange system, the centrifugal force generated by the rotational flow easily causes the fouling particles or precursor components to move, gather and deposit to the pipe wall, and finally form a fouling layer to deteriorate the heat transfer. 4) The spiral ribbon shape has a large resistance, which easily brings a large equipment pressure drop, and to some extent limits the operation flexibility of the heat transfer pipe. SUMMARY

[0006] The present application aims to at least solve one of the technical problems in the related art. To this end, the purpose of the present application is to provide a series coupling type vortex enhanced heat transfer pipe and a cracking furnace, which can break the rigid rotational flow existing in the prior art by inducing secondary vortex without significantly losing the rotational flow intensity of the fluid near the pipe wall, thereby inhibiting the negative effects caused by the centrifugal force, promoting the orderly and stable heat-mass transfer between the fluid near the pipe wall and the fluid in the center area, and realizing the deep matching of the fluid mechanics characteristics and the heat transfer characteristics.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a series coupling type vortex enhanced heat transfer pipe, which comprises a hollow tubular pipe body, a rotational flow generating mechanism is arranged on the inner wall of the pipe body and extends along the axial direction of the pipe body, a vortex generator is arranged on the downstream side of the rotational flow generating mechanism at a position away from the inner wall of the pipe body, and there is a fluid attack angle between the vortex generator and the flow direction of the fluid.

[0008] Preferably, the vortex generator is provided with a plurality of vortex generators, and the plurality of vortex generators are arranged in the radial cross section of the pipe body and are arranged in the circumferential direction or the elliptical circumferential direction.

[0009] Preferably, the fluid attack angle is 0°-90°.

[0010] Preferably, the distance between the vortex generator and the inner wall of the pipe body is 0.1-0.5 times the inner diameter of the pipe body.

[0011] Preferably, the vortex generator is connected to the flow-removing end of the vortex generator mechanism by a rib plate.

[0012] Preferably, the vortex generator is a wing-type vortex generator, the thickness of the wing of the wing-type vortex generator is 0.5-2 times the wall thickness of the pipe body.

[0013] The radial dimension of the wing along the pipe body is 0.05-0.4 times the inner diameter of the pipe body.

[0014] The axial length of the wing along the pipe body is 0.05-1 times the inner diameter of the pipe body.

[0015] The included angle between the bottom end of the wing and the tangent of the circular or elliptical shape formed by the arrangement of the wing in the radial cross-section of the pipe body is 0°-90°.

[0016] Preferably, the vortex generator is a blunt body-type vortex generator, the radial dimension of the blunt body structure of the blunt body-type vortex generator along the pipe body is 0.05-0.4 times the inner diameter of the pipe body.

[0017] The axial length of the blunt body structure along the pipe body is 0.05-1 times the inner diameter of the pipe body.

[0018] Preferably, the blunt body structure is provided with a jet hole.

[0019] Preferably, the vortex generator is a solid spiral ribbon, the twist angle of the solid spiral ribbon is 45-360°, the radial dimension of the solid spiral ribbon along the pipe body is 0.05-0.5 times the inner diameter of the pipe body, the axial dimension of the solid spiral ribbon along the pipe body is 0.05-1 times the inner diameter of the pipe body, and the twist direction of the solid spiral ribbon is the same as or opposite to the twist direction of the vortex generator mechanism.

[0020] Preferably, the vortex generator mechanism is a solid spiral ribbon or a hollow spiral ribbon.

[0021] Preferably, the vortex generator mechanism is a hollow spiral ribbon, and the vortex generator mechanism comprises at least one spiral blade, and at least part of the radial dimension of each spiral blade is gradually arranged in the axial direction of the pipe body.

[0022] Preferably, the twist angle of the spiral blade is 90°-1080°, more preferably 180°-360°.

[0023] Preferably, the height of the helical blade in the axial direction of the pipe body is 1-10 times the inner diameter of the pipe body.

[0024] Preferably, the radial dimension of the inflow end and the radial dimension of the outflow end of the helical blade are respectively 0-0.5 times, more preferably 0-0.4 times, the inner diameter of the pipe body.

[0025] Preferably, the radial dimension of the inflow end of the helical blade is smaller than the radial dimension of the outflow end.

[0026] Preferably, the helical blade has a first helical twist section close to the inflow end thereof and a second helical twist section close to the outflow end thereof, and the helix angle of the first helical twist section is 0.1-5 times the helix angle of the second helical twist section.

[0027] Preferably, the helix angle of the first helical twist section is greater than the helix angle of the second helical twist section.

[0028] Preferably, the vortex generator is a conical ring; preferably, the conical ring is a circular conical ring or a prismatic conical ring.

[0029] Preferably, the radial dimension of the large-diameter end of the conical ring is 0.1-1 times the inner diameter of the pipe body, the radial dimension of the small-diameter end of the conical ring is 0.1-0.8 times the radial dimension of the large-diameter end thereof; the conical angle of the conical ring is 10-80°, the length of the conical ring in the axial direction of the pipe body is 0.1-2 times the inner diameter of the pipe body, and the thickness of the conical ring is 0.5-2 times the wall thickness of the pipe body.

[0030] Preferably, the radial dimension of the large-diameter end of the conical ring is 0.1-0.8 times the inner diameter of the pipe body.

[0031] Preferably, the surface of the conical ring is provided with jet holes, and the opening rate of the jet holes on the conical ring is 1-20%.

[0032] Preferably, the conical ring is coaxially arranged with the pipe body.

[0033] Preferably, the rotational flow generating mechanism and the vortex generator located on the downstream side of the rotational flow generating mechanism constitute a turbulence assembly, and the turbulence assembly is provided in multiple groups, and the multiple groups of turbulence assemblies are arranged at intervals in the axial direction of the pipe body.

[0034] Preferably, the distance between adjacent two turbulence assemblies is 10-100 times the inner diameter of the pipe body.

[0035] Preferably, the helical twist directions of the helical blades of the rotational flow generating mechanisms included in adjacent two turbulence assemblies are opposite.

[0036] The second aspect of the present application provides a cracking furnace, which comprises a radiation chamber, at least one radiation furnace tube assembly is installed in the radiation chamber, the radiation furnace tube assembly comprises a plurality of radiation furnace tubes arranged in sequence and heat transfer tubes connecting adjacent radiation furnace tubes, and the heat transfer tube is the series coupling type vortex enhanced heat transfer tube described above.

[0037] According to the series coupling type vortex enhanced heat transfer tube provided by the present application, by arranging the vortex generator away from the inner wall of the pipe body on the downstream side of the rotational flow generating mechanism, and arranging the vortex generator to have a fluid attack angle with the flow direction of the fluid, when the fluid in the central region of the pipe body flows through the vortex generator, due to the existence of the fluid attack angle, a rotational secondary vortex is induced on the rear side, thereby improving the mixing effect between the fluid in the central region and the fluid away from the central region. Through the series coupling type vortex enhanced heat transfer tube provided by the present application, on the basis of the rotational flow generating mechanism forming a rigid rotational flow, a secondary vortex is formed through the vortex generator, thereby forming a flow field structure of the rigid rotational flow embedded with the rotational secondary vortex, under the premise that the rotational flow intensity of the fluid near the pipe wall is not lost, a radial disturbance is formed in a larger heat transfer pipe space, and the heat exchange between the fluid near the pipe wall and the fluid in the central region is promoted. In addition, in the present application, through the series coupling of the rotational flow generating mechanism and the vortex generator, the heat exchange process is orderly, stable and accurately controlled, the heat exchange efficiency of the fluid is improved, the uniformity of the temperature field in the pipe body is improved, and the radial temperature gradient is effectively reduced or even eliminated. In addition, through the radial disturbance effect of the rotational secondary vortex, the mass transfer can also be accelerated, especially the scale particles or precursor components gathered near the pipe wall under the action of centrifugal force are re-rolled into the central region of the pipe body, thereby inhibiting the appearance and growth of the pipe wall scale layer, and prolonging the scale removal period of the heat transfer pipe. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a structural schematic diagram of a conventional rotational flow generating mechanism;

[0039] Figure 2 is a structural schematic diagram of a series coupling type vortex enhanced heat transfer pipe provided by embodiment 1 of the present application;

[0040] Figure 3 is a configuration schematic diagram of the vortex generator in the present application;

[0041] Figure 4 is a vortex field structure feature comparison diagram of the series coupling type vortex enhanced heat transfer pipe and the light pipe in embodiment 1 of the present application;

[0042] Figure 5 is an axial distribution comparison diagram of the axial fluid temperature of the series coupling type vortex enhanced heat transfer pipe, the light pipe and the heat transfer pipe with a conventional rotational flow generating mechanism in embodiment 1 of the present application;

[0043] Figure 6 is a radial distribution comparison diagram of fluid temperature at the end of the heat transfer pipe of the conventional rotational flow generating mechanism of the series coupling type vortex flow enhanced heat transfer pipe and the light pipe in embodiment 1 of the present application;

[0044] Figure 7 is a structural schematic diagram of a series coupling type vortex flow enhanced heat transfer pipe provided in embodiment 2 of the present application;

[0045] Figure 8 is a structural schematic diagram of a series coupling type vortex flow enhanced heat transfer pipe provided in embodiment 3 of the present application;

[0046] Figure 9 is a structural schematic diagram of a series coupling type vortex flow enhanced heat transfer pipe provided in embodiment 4 of the present application;

[0047] Figure 10 is a structural schematic diagram of a series coupling type vortex flow enhanced heat transfer pipe provided in embodiment 5 of the present application;

[0048] Figure 11 is a structural schematic diagram of a series coupling type vortex flow enhanced heat transfer pipe provided in embodiment 6 of the present application.

[0049] Explanation of reference signs

[0050] 1, pipe body; 2, rotational flow generating mechanism; 201, first side; 202, second side; 21, first spiral blade; 22, second spiral blade; 23, flow removing end; 231, second spiral twisted section; 24, flow entering end; 241, first spiral twisted section; 25, positive pressure side; 26, back pressure side; 3, vortex generator; 4, rib plate. DETAILED DESCRIPTION

[0051] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0052] As shown in Figure 2 , the present application provides a series coupling type vortex flow enhanced heat transfer pipe, which comprises a hollow tubular pipe body 1, a rotational flow generating mechanism 2 is arranged on the inner wall of the pipe body 1 and extends along the axial direction of the pipe body 1, a vortex generator 3 is arranged on the downstream side of the rotational flow generating mechanism 2 at a position away from the inner wall of the pipe body 1, and there is a fluid attack angle between the vortex generator 3 and the flow direction of the fluid.

[0053] In the technical scheme provided by the application, the vortex generator 3 is arranged on the downstream side of the rotational flow generating mechanism 2 and away from the inner wall of the pipe body 1, and the vortex generator 3 is arranged to have a fluid attack angle with the flow direction of the fluid. When the fluid in the central region of the pipe body 1 flows through the vortex generator 3, a secondary vortex is induced on the rear side of the vortex generator 3 due to the fluid attack angle, and the mixing between the fluid in the central region and the fluid away from the central region in the pipe body 1 is strengthened.

[0054] According to the series coupling vortex enhanced heat transfer pipe provided by the application, the rigid rotational flow built-in secondary vortex flow field structure is formed, the rotational flow intensity of the fluid near the pipe wall is not significantly lost, the rotational secondary vortex is effectively induced in the central region away from the pipe wall, the radial disturbance is formed in the larger heat transfer pipe space, and the heat exchange between the fluid near the pipe wall and the fluid in the central region is promoted. In addition, in the application, the heat exchange efficiency of the fluid is improved by the series coupling of the rotational flow generating mechanism 2 and the vortex generator 3, the uniformity of the temperature field in the pipe body 1 is improved, the radial temperature gradient is effectively reduced or even eliminated, and it can be understood that the radial disturbance of the secondary vortex can also accelerate the mass transfer, in particular, the scale particles or precursor components gathered near the pipe wall under the centrifugal force are reinvolved into the central region of the pipe body 1, so that the appearance and growth of the pipe wall scale layer are inhibited, and the scale cleaning period of the heat transfer pipe is prolonged.

[0055] In the application, the number of the vortex generators 3 can be 1-8, and more preferably 1-4. In some embodiments, the vortex generators 3 are arranged in multiple numbers, and the multiple vortex generators 3 are arranged in the circumferential direction or the elliptical circumferential direction in the radial cross section of the pipe body 1.

[0056] In some embodiments, the fluid attack angle is 0°-90°, and more preferably 30°-60°. The fluid attack angle is the included angle between the vortex generator 3 and the flow direction of the fluid. Taking the airfoil vortex generator as an example, the fluid attack angle is the inclination angle of the airfoil with respect to the axial direction of the pipe body 1. By setting the fluid attack angle in the above range, the vortex can be effectively formed behind the vortex generator 3 while the fluid pressure drop is minimized, and finally the balance between the heat exchange effect and the pressure drop loss is achieved.

[0057] It should be noted that the fluid attack angles of different vortex generators can be the same or different in the application.

[0058] In some embodiments, the distance between the vortex generator 3 and the inner wall of the pipe body 1 is 0.1-0.5 times the inner diameter of the pipe body 1; in some embodiments, the vortex generator 3 is connected to the flow-out end 23 of the rotational flow generating mechanism 2 through the rib plate 4. Specifically, the rib plate 4 is connected to the end or middle part of the vortex generator 3.

[0059] In some embodiments, the vortex generator 3 is a wing-type vortex generator, the thickness of the wing of the wing-type vortex generator is 0.5-2 times the wall thickness of the pipe body 1, the dimension of the wing along the radial direction of the pipe body 1 is 0.05-0.4 times the inner diameter of the pipe body 1, and the length of the wing along the axial direction of the pipe body 1 is 0.05-1 times the inner diameter of the pipe body 1; the included angle between the bottom end of the wing and the tangent of the circle or ellipse formed by the arrangement of the wing in the radial cross section of the pipe body 1 is 0°-90°.

[0060] The present application does not make special limitation on the shape of the wing, which can be a regular-shaped wing or an arbitrarily irregular-shaped wing. In some embodiments, the wing can be combined with the vortex generator 3 to form a wing-type vortex generator. Figure 3 As shown, the wing can be one of a triangular wing, a rectangular wing, a trapezoidal wing, a fin-shaped wing, an elliptical wing, a semi-elliptical wing, a curved surface wing, a slant-cut cylindrical surface wing, and a slant-cut elliptical cylindrical surface wing.

[0061] In some embodiments, the vortex generator 3 is a blunt body-type vortex generator, the dimension of the blunt body structure of the blunt body-type vortex generator along the radial direction of the pipe body 1 is 0.05-0.4 times the inner diameter of the pipe body 1, and the length of the blunt body structure along the axial direction of the pipe body 1 is 0.05-1 times the inner diameter of the pipe body 1. Through the above structural arrangement, the enhanced heat transfer pipe provided by the present application effectively enhances the radial mixing disturbance of the fluid in the central region by forming a rotational secondary vortex around the blunt body structure at the cost of small resistance loss, realizes the orderly regulation and control of the flow field structure in the pipe at a low pressure drop, and ensures the high-intensity input of the heat from the pipe wall to the central region of the pipe.

[0062] The present application does not make special limitation on the specific structure of the blunt body structure, and specifically, the blunt body structure can be combined with the vortex generator 3 to form a blunt body-type vortex generator. Figure 3 As shown, the blunt body structure can be one of a fin-shaped body, a slant-cut section of a fin-shaped body, a cylinder, a slant-cut section of a cylinder, an elliptical cylinder, a slant-cut section of an elliptical cylinder, a circular truncated cone, a slant-cut section of a circular truncated cone, a circular cone, a slant-cut section of a circular cone, a hemisphere, a semi-ellipsoid, a prism, a prism, and a pyramid.

[0063] In some embodiments, the blunt body structure is provided with a jet hole. The present application does not make special limitation on the shape of the jet hole, which can be circular, elliptical, square, diamond, trapezoidal, or other irregular shapes.

[0064] In some embodiments, the vortex generator 3 is a solid spiral ribbon, the twist angle of which is 45-360°, the size of the solid spiral ribbon in the radial direction of the pipe body 1 is 0.05-0.5 times the inner diameter of the pipe body 1, and the size of the solid spiral ribbon in the axial direction of the pipe body 1 is 0.05-1 times the inner diameter of the pipe body 1. The twist direction of the solid spiral ribbon is the same as or opposite to the twist direction of the rotational flow generating mechanism 2. Through the above structural arrangement, the present application provides a heat transfer enhanced tube, in which the fluid in the central region is forced to form rotational flow, and under the action of the centrifugal force, obtains a radial velocity migrating towards the tube wall, thereby enhancing the heat-mass exchange between the fluid in the central region and the fluid near the tube wall, and effectively eliminating the central poor heat exchange region.

[0065] In some embodiments, the rotational flow generating mechanism 2 is a solid spiral ribbon or a hollow spiral ribbon; in some embodiments, the rotational flow generating mechanism 2 is a hollow spiral ribbon, which comprises at least one spiral blade, and at least part of the radial dimension of each spiral blade is arranged in a gradient manner in the axial direction of the pipe body 1.

[0066] In the present application, by further improving the structure of the spiral blade and cooperating with the vortex generator 3 arranged on the downstream side of the rotational flow generating mechanism 2, high-intensity rigid rotational flow and rotational high-energy secondary vortex are induced efficiently with simple structure and low pressure drop loss, so as to simultaneously consider the rigid rotational flow to destroy the boundary layer and promote the heat transfer between the tube wall and the fluid near the tube wall, and the secondary vortex to strengthen the heat-mass ordered interaction between the fluid near the tube wall and the main flow.

[0067] Specifically, according to the series coupling vortex enhanced heat transfer tube provided by the present application, when the fluid enters the vortex enhanced heat transfer tube and flows through the rotational flow generating mechanism 2, the fluid in the central region of the pipe body 1 passes through in the form of approximately planar flow, or in the form of rigid rotational flow under the viscous shear action of the fluid near the wall surface of the pipe body 1, and then further flows through the vortex generator 3 on the downstream side of the rotational flow generating mechanism 2; and the fluid near the wall surface region of the pipe body 1, after encountering the rotational flow generating mechanism 2, completes the conversion of the axial velocity component to the tangential velocity component with certain energy loss as the radial dimension increases, forms high-intensity vortex flow, and forms shear disturbance to the fluid in the central region.

[0068] Under the action of the above fluid mechanics characteristics, in the first aspect, the fluid in the central region of the tube body 1 induces secondary vortexes on the back side after passing through the vortex generator 3 due to the existence of the fluid attack angle, thereby strengthening the mixing between the fluid in the central region and the fluid away from the central region in the tube body 1. In the second aspect, the fluid near the wall of the tube body 1 is hindered by the spiral flow generating mechanism 2, resulting in a significant decrease in the axial velocity, so that there is a large velocity difference between the back pressure side 26 of the spiral flow generating mechanism 2 and the fluid in the central region of the tube body 1, and the secondary vortexes are induced on the back pressure side 26 of the incoming flow end 24. The secondary vortexes gradually develop along the axial direction with the increase of the radial size of the spiral flow generating mechanism 2, and the size and strength of the vortexes increase, and the vortexes gradually move to the central region of the tube body 1, and are released to the downstream tube section in a stable motion form at the outgoing flow end 23, and are embedded in the rigid spiral flow. In the third aspect, the high-strength spiral flow formed by the positive pressure side 25 of the spiral blade is released to the downstream tube section at the outgoing flow end 23, forms a rigid spiral flow, and exerts a high-strength shearing force on the wall of the tube body 1, effectively thins and destroys the laminar boundary layer, promotes the heat transfer between the tube wall and the fluid near the tube wall, and increases the wall component update rate, shortens the residence time of the scaling particles or precursors, thereby effectively inhibiting the formation and growth of the fouling layer. Finally, the fluid leaving the spiral flow generating mechanism 2 and the vortex generator 3 obtains a desired spiral flow strength near the wall of the tube body 1, and a plurality of secondary vortexes with a specific size, vorticity and stable form are formed in the central region of the tube body 1, so as to balance the heat transfer between the wall of the tube body 1 and the fluid near the wall, and the heat-mass interaction between the fluid near the wall of the tube body 1 and the fluid in the central region, greatly improve the fluid heat exchange efficiency, strength and uniformity, and effectively inhibit the formation of the fouling layer.

[0069] It can be understood that, in the present application, by gradually changing at least part of the radial size of at least one spiral blade constituting the spiral flow generating mechanism 2 in the axial direction of the tube body 1, the shape resistance of the spiral flow generating mechanism 2 is reduced, the fluid passing capacity is improved, the operating pressure drop of the equipment is reduced, and the production capacity is effectively improved; and by gradually changing the radial size of the spiral blade, the unobstructed flow area of the fluid changes, thereby inducing high-vortex, large-size, and rotationally moving stable symmetrically distributed secondary vortexes in the central region of the heat transfer tube, which can improve the heat exchange strength and reduce or even eliminate the radial temperature gradient; in addition, the above structure can also slow down the direct impact of high-speed fluid on the spiral blade, and improve the overall impact resistance of the spiral flow generating mechanism 2.

[0070] The flow field in the tube body 1 behind the cyclone generating mechanism 2 and the vortex generator 3 is a flow structure with multiple in-progressive high-energy secondary vortices in rigid cyclone, which deeply matches the heat exchange characteristics and greatly improves the heat exchange effect; in addition, the mass transfer can be accelerated under the disturbance of the high-energy secondary vortices, and in particular, the scale particles or precursor components gathered near the wall of the heat transfer tube under the action of centrifugal force are re-rolled into the central area, so as to inhibit the formation of the scale layer on the tube wall and prolong the scale cleaning cycle of the heat transfer tube.

[0071] In the present application, in order to improve the disturbance effect of the cyclone generating mechanism 2 on the fluid in the tube body 1, the twist angle of the spiral blade is 90°-1080°, more preferably 180°-360°; for example, the twist angle of the spiral blade is 180°, 210°, 240°, 270°, 300°, 330° or 360°.

[0072] In some embodiments, the height of the spiral blade in the axial direction of the tube body 1 is 1-10 times the inner diameter of the tube body 1. In particular, by controlling the height of the spiral blade in the axial direction of the tube body 1 to be 1-5 times the inner diameter of the tube body 1, the ideal cyclone speed can be obtained in a shorter axial distance.

[0073] In some embodiments, the radial dimension of the inflow end 24 of the spiral blade and the radial dimension of the outflow end 23 are respectively 0-0.5 times, more preferably 0-0.4 times, the inner diameter of the tube body 1.

[0074] In some embodiments, the radial dimension of the inflow end 24 of the spiral blade is smaller than the radial dimension of the outflow end 23. In this way, the impact of the fluid on the side of the cyclone generating mechanism 2 close to the central area of the tube body 1 can be effectively avoided, and the impact stress concentrated on the inflow end 24 and transmitted to the connection part of the inflow end 24 and the tube body 1 in the form of shear stress can be maximally avoided.

[0075] In some embodiments, the thickness of the spiral blade is arranged in the axial direction of the tube body 1 in an equal or gradual manner; it should be noted that when the thickness of the spiral blade is arranged in the axial direction of the tube body 1 in a gradual manner, the present application does not specially limit the gradual form, for example, the gradual rate is linear or nonlinear.

[0076] The thickness of the inflow end 24 of the spiral blade is 0-2 times, more preferably 1-1.5 times, the thickness of the outflow end 23; further, the thickness of the spiral blade gradually decreases along the flow direction of the fluid in the tube body 1, so that the connection strength of the inflow end 24 of the spiral blade and the tube body 1 can be fully guaranteed, the fluid impact on the inflow end 24 of the spiral blade can be further attenuated, the stress effect between the inflow end 24 of the spiral blade and the tube body 1 can be weakened, and the problem of cracking of the tube wall of the tube body 1 can be avoided.

[0077] In some embodiments, the thickness of the outflow end 23 of the spiral blade is 0.2-2 times the wall thickness of the tube body 1 and 0.1-0.2 times the inner diameter of the tube body 1.

[0078] In some embodiments, the thickness of the spiral blade is equal or gradually arranged in the radial direction of the tube body 1. It should be noted that when the thickness of the spiral blade is gradually arranged in the radial direction of the tube body 1, the present application does not make special limitation on the gradual form, for example, the gradual rate is linear or nonlinear.

[0079] In some embodiments, the spiral blade has oppositely arranged first and second side edges 201 and 202, the first side edge 201 is connected to the inner wall of the tube body 1, the thickness of the first side edge 201 is 0.2-2 times the wall thickness of the tube body 1 and 0.1-0.2 times the inner diameter of the tube body 1, and the thickness of the second side edge 202 is 0-1 times, more preferably 0.5-1 times, the thickness of the first side edge 201.

[0080] It can be understood that in the present application, the gradual form of the thickness of the spiral blade can be adapted to the axial evolution behavior of the fluid impact force, thereby effectively reducing the (thermal) stress at the connection part of the spiral flow generating mechanism and the tube body 1, prolonging the service life of the heat transfer tube and the safe production operation cycle.

[0081] In some embodiments, the spiral blade has a first spiral twisted section 241 close to the inflow end 24 thereof and a second spiral twisted section 231 close to the outflow end 23 thereof, and the helix angle of the first spiral twisted section 241 is 0.1-5 times the helix angle of the second spiral twisted section 231.

[0082] In some embodiments, the helix angle of the first spiral twisted section 241 is greater than the helix angle of the second spiral twisted section 231. Through the above structural arrangement, the generation rate of tangential spiral flow of near-wall fluid when passing through the tube section where the spiral blade is located is different along the axial direction of the tube body 1, specifically, the generation rate of the spiral flow in the region where the first spiral twisted section 241 is located is less than that in the region where the second spiral twisted section 231 is located, and the pressure drop distribution along the tube body 1 presents a trend of "first small and then large". Furthermore, the series coupling type vortex flow enhanced heat transfer tube provided by the present application can slow down the impact of high-speed fluid on the inflow end 24 of the spiral blade, and effectively disperse the shear stress at the connection part of the spiral blade and the tube body 1, so that the pressure drop distribution along the tube body 1 is more gentle, and the overall reliability of the spiral flow generating mechanism 2 is enhanced.

[0083] It can be understood that, in the series coupling type vortex flow reinforced heat transfer pipe provided by the application, at least part of the radial dimension of the spiral blade is gradually arranged in the axial direction of the pipe body 1, that is, the spiral blade can be arranged as a locally variable diameter. In some embodiments, in the axial direction of the pipe body 1, the first spiral twisted section 241 is a variable diameter twisted section, and the second spiral twisted section 231 is a constant diameter twisted section.

[0084] In some embodiments, the rotational flow generating mechanism 2 comprises a plurality of circumferentially arranged spiral blades, which are arranged side by side in the axial direction of the pipe body 1.

[0085] In some embodiments, the vortex generator 3 is a conical ring; preferably, the conical ring is a circular conical ring or a prismatic conical ring; when the conical ring is a prismatic conical ring, the number of edges is 3-12, preferably 4-8.

[0086] In some embodiments, the radial dimension of the large diameter end of the conical ring is 0.1-1 times the inner diameter of the pipe body 1, the radial dimension of the small diameter end of the conical ring is 0.1-0.8 times the radial dimension of the large diameter end of the conical ring; the conical angle of the conical ring is 10-80°, the length of the conical ring in the axial direction of the pipe body 1 is 0.1-2 times the inner diameter of the pipe body 1, and the thickness of the conical ring is 0.5-2 times the wall thickness of the pipe body 1; further preferably, the radial dimension of the large diameter end of the conical ring is 0.1-0.8 times the inner diameter of the pipe body 1.

[0087] In some embodiments, the surface of the conical ring is provided with jet holes, and the opening rate of the jet holes on the conical ring is 1-20%; in the application, the shape of the jet holes includes but is not limited to rectangle, circle, ellipse, polygon.

[0088] In some embodiments, the conical ring is arranged coaxially with the pipe body 1. The conical ring is arranged in a "shrink-expand" manner or an "expand-shrink" manner in the axial direction of the pipe body 1.

[0089] The application does not make special limitations on the arrangement of the conical ring, for example, the conical ring is connected with the rotational flow generating mechanism 2 through a rib plate, or the conical ring is connected with the inner wall of the pipe body 1 through a rib plate.

[0090] It can be understood that the arrangement of the conical ring can induce the oscillation behavior of the fluid in the pipe body 1, strengthen the radial mixing behavior of the fluid, and greatly promote the heat transfer from the pipe wall to the central area.

[0091] In some embodiments, the rotational flow generating mechanism 2 and the vortex generator 3 located on the downstream side of the rotational flow generating mechanism 2 constitute a turbulence assembly, and a plurality of sets of the turbulence assembly are arranged at intervals in the axial direction of the pipe body 1; preferably, the distance between two adjacent turbulence assemblies is 10-100 times the inner diameter of the pipe body 1; more preferably, 30-80 times. Further, the helical twist directions of the helical blades of the rotational flow generating mechanisms 2 included in the two adjacent turbulence assemblies are opposite.

[0092] It can be understood that in the pipe body 1, the fluid passing through the rotational flow generating mechanism 2 and the vortex generator 3 has both rotational flow intensity and turbulent intensity, and the vortex is further intensified when entering the next set of rotational flow generating mechanism 2 and vortex generator 3, and arranging a plurality of sets of rotational flow generating mechanism 2 and vortex generator 3 at intervals in the axial direction of the pipe body 1 can ensure that the ordered heat and mass transfer requirements of the fluid are met. Alternatively, the turbulence assembly of the present application and the conventional rotational flow generating mechanism 5 (as shown in Figure 1 It can be understood that in the present application, by arranging rotational flow generating mechanisms with different configurations in the axial direction of the pipe body 1, the depth of the match between the turbulent intensity, the rotational flow intensity of the fluid in different heat transfer pipe sections, and the heat transfer requirement is achieved. In the solution provided by the present application, the configuration of the rotational flow generating mechanism 2 is simple, easy to manufacture, and easy to carry out industrial reform, which can replace the heat transfer pipe in the existing equipment.

[0093] The second aspect of the present application provides a cracking furnace, which comprises a radiation chamber, at least one radiation furnace pipe assembly is installed in the radiation chamber, the radiation furnace pipe assembly comprises a plurality of radiation furnace pipes arranged in sequence and a heat transfer pipe connecting adjacent radiation furnace pipes, and the heat transfer pipe is the series coupling type vortex enhanced heat transfer pipe provided by the present application. By arranging the series coupling type vortex enhanced heat transfer pipe provided by the present application in the radiation chamber of the cracking furnace, not only the heat transfer effect of the fluid in the radiation chamber can be improved, but also the operating pressure drop of the equipment can be reduced, and the production capacity can be improved; in addition, since the thermal stress of the heat transfer pipe is reduced and the occurrence of the pipe wall scale layer is inhibited, the operation cycle of the cracking furnace can also be improved.

[0094] The series coupling type vortex enhanced heat transfer pipe provided by the present application is further described below through specific embodiments.

[0095] Embodiment 1

[0096] The embodiment takes a pipe body 1 with an inner diameter of 45 mm and a length of 3.6 m as the research object, adds a cyclone generating mechanism 2 and a vortex generator 3 at a position 1 m away from the fluid inlet of the pipe body 1, and investigates the flow-heat transfer characteristics of the fluid in the pipe body 1, with the specific working conditions being: the fluid medium is air, the fluid linear velocity is 75 m / s, the fluid inlet temperature is 873.15 K, the pipe wall temperature is 1118 K, and the outlet pressure is 1 atm.

[0097] In the embodiment, the rotational flow generating mechanism 2 is a hollow spiral ribbon arranged on the inner wall of the pipe body 1 and extending along the axial direction of the pipe body 1, and specifically consists of two spiral blades, i.e., a first spiral blade 21 and a second spiral blade 22. Four rectangular wings are arranged at the downstream side of the rotational flow generating mechanism 2, away from the inner wall of the pipe body 1, and have a 30° fluid angle of attack with respect to the flow direction of the fluid. Along the axial direction of the pipe body 1, the distance between one end of the four rectangular wings connected to the outflow end 23 of the rotational flow generating mechanism 2 and the inner wall of the pipe body 1 is 0.4 times the inner diameter of the pipe body 1, and the distance between the other end of the four rectangular wings away from the outflow end 23 of the rotational flow generating mechanism 2 and the inner wall of the pipe body 1 is 0.3 times the inner diameter of the pipe body 1. The four rectangular wings are uniformly spaced in the circumferential direction in the radial cross section of the pipe body 1 and are connected to the outflow end 23 of the rotational flow generating mechanism 2 by a rib plate 4. The thickness of each rectangular wing is 1 times the wall thickness of the pipe body 1, the radial dimension of each rectangular wing is 0.1 times the inner diameter of the pipe body 1, and the axial length of each rectangular wing is 0.15 times the inner diameter of the pipe body 1. The included angle between the bottom end of each rectangular wing and the tangent of the circle formed by the arrangement of the rectangular wing in the radial cross section of the pipe body 1 is 0°. The twist angles of the first spiral blade 21 and the second spiral blade 22 are the same and are 180°. The heights of the first spiral blade 21 and the second spiral blade 22 in the axial direction of the pipe body 1 are the same and are 3 times the inner diameter of the pipe body 1. The radial dimensions of the inflow end 24 of the first spiral blade 21 and the second spiral blade 22 are 0.2 times the inner diameter of the pipe body 1, respectively, and the radial dimensions of the outflow end 23 are 0.4 times the inner diameter of the pipe body 1, respectively. Along the flow direction of the fluid in the pipe body 1, the thicknesses of the first spiral blade 21 and the second spiral blade 22 gradually decrease linearly. The thickness of the inflow end 24 of the first spiral blade 21 and the second spiral blade 22 is 1.5 times the thickness of the outflow end 23, and the thickness of the outflow end 23 is 0.6 times the wall thickness of the pipe body 1 and 0.1 times the inner diameter of the pipe body 1. The thicknesses of the first spiral blade 21 and the second spiral blade 22 gradually change linearly in the radial direction of the pipe body 1. The first spiral blade 21 and the second spiral blade 22 have oppositely arranged first side edges 201 and second side edges 202, respectively. The thickness of the second side edge 202 is 0.5 times the thickness of the first side edge 201, the thickness of the first side edge 201 is 0.6 times the wall thickness of the pipe body 1, and 0.1 times the inner diameter of the pipe body 1.The first helical blade 21 and the second helical blade 22 each have a first helical twisted section 241 near their respective inflow end 24 and a second helical twisted section 231 near their respective outflow end 23. In the first helical blade 21, the helix angle of the first helical twisted section 241 is equal to that of the second helical twisted section 231, which is 38.5°; in the second helical blade 22, the helix angle of the first helical twisted section 241 is equal to that of the second helical twisted section 231, which is 38.5°. The circumferentially arranged first helical blade 21 and second helical blade 22 are arranged side by side in the axial direction of the tube body 1.

[0098] The test results of fluid flow-heat transfer characteristics are summarized in Table 1; among them, the conventional swirl generator 5 is as follows: Figure 1 As shown. Figure 4 The diagram shown is a characteristic image of the vortex field structure of the series-coupled vortex-enhanced heat transfer tube in this embodiment. Figure 4 It can be seen that the swirl generator 2 and vortex generator 3 in this embodiment induce the formation of an ideal rigid swirling vortex field with built-in symmetrical secondary vortices. For example... Figure 5 The diagram shown is an axial distribution of the axial fluid temperature in the series-coupled eddy current enhanced heat transfer tube in this embodiment, compared to a bare tube (such as...). Figure 5 a) In this embodiment, the temperature of the fluid at the axis of the heat transfer tube is significantly increased by more than 20°C, effectively eliminating the low-temperature zone in the center. Compared with conventional swirling flow generating mechanisms (such as...), Figure 5 b) The heating rate of the fluid at the axis is significantly superior, and the heating trend is stable without violent fluctuations. Figure 6 The radial temperature distribution diagram of the fluid at the end outlet of the series-coupled eddy current enhanced heat transfer tube in this embodiment further confirms that the heat transfer tube provided in this embodiment significantly reduces the radial temperature gradient while improving the heat transfer intensity, thus achieving good heat transfer uniformity.

[0099] Example 2

[0100] Combination Figure 7 The structure of this embodiment is basically the same as that of the series-coupled vortex-enhanced heat transfer tube used in Embodiment 1. The difference is that in this embodiment, along the axial direction of the tube body 1, the distance between one end of the four rectangular wings connected to the outflow end 23 of the vortex generator 2 and the inner wall of the tube body 1 is 0.3 times the inner diameter of the tube body 1, and the distance between the end of the four rectangular wings away from the outflow end 23 and the inner wall of the tube body 1 is 0.4 times the inner diameter of the tube body 1. This causes the flow area of ​​the fluid in the central region of the tubular shell 1 to change in a "gradual contraction-sudden expansion" manner when flowing through the vortex generator 3. The test results of the fluid flow-heat transfer characteristics of the series-coupled vortex-enhanced heat transfer tube provided in this embodiment are summarized in Table 1.

[0101] Example 3

[0102] In combination Figure 8 The structure of the series-coupled vortex enhanced heat transfer tube in this embodiment is basically the same as that in Embodiment 2, except that in this embodiment, the included angle between the bottom end of the wing of the vortex generator 3 and the tangent of the circle formed by the arrangement of the vortex generator 3 in the radial cross section of the tube body (1) is 45°. The working principle of this embodiment is basically the same as that of Embodiment 2, except that the fluid flowing through the vortex generator of this embodiment can obtain tangential velocity, thereby effectively enhancing the strength of the secondary vortex and further improving the heat exchange effect. The fluid flow and heat transfer characteristics test results of the series-coupled vortex enhanced heat transfer tube provided in this embodiment are summarized in Table 1.

[0103] Embodiment 4

[0104] In combination Figure 9 The structure of the series-coupled vortex enhanced heat transfer tube in this embodiment is basically the same as that in Embodiment 3, except that in this embodiment, the height of the first helical twist section 241 is 2 times the inner diameter of the tube body 1, and the height of the second helical twist section 231 is 1 times the inner diameter of the tube body 1, so that the helical pitch angle of the first helical twist section 241 is 46.7°, and the helical pitch angle of the second helical twist section 231 is 27.9°. Through the above structural arrangement, the generation rate of tangential rotational flow of near-wall fluid when passing through the helical blade pipe section exists differences along the axial direction of the tube body 1, specifically, the rotational flow generation rate of the region where the first helical twist section 241 is located is less than that of the region where the second helical twist section 231 is located, thereby affecting the speed, strength and form of the vortex induced by the rectangular wing.

[0105] Compared with Embodiment 3, the series-coupled vortex enhanced heat transfer tube provided in this embodiment can slow down the impact of high-speed fluid on the first helical twist section 241 of the rotational flow generating mechanism 2, effectively disperse the shear stress at the connection part of the rotational flow generating mechanism 2 and the tube body 1, so that the pressure drop distribution along the pipeline is more gentle; in addition, the series-coupled vortex enhanced heat transfer tube of this embodiment can also improve the strength of the secondary vortex induced by the vortex generator 3 to a certain extent. The fluid flow and heat transfer characteristics test results of the series-coupled vortex enhanced heat transfer tube provided in this embodiment are summarized in Table 1.

[0106] Embodiment 5

[0107] In combination Figure 10The structure of the series-coupled vortex enhanced heat transfer tube in this embodiment is basically the same as that in Embodiment 4, except that in this embodiment: the vortex generator 3 is a solid spiral ribbon, and the twist angle is 90°. The size of the solid spiral ribbon in the radial direction of the tube body 1 is 0.2 times the inner diameter of the tube body 1, and the size of the solid spiral ribbon in the axial direction of the tube body 1 is 0.1 times the inner diameter of the tube body 1. The twist direction of the solid spiral ribbon is the same as that of the rotational flow generating mechanism 2. In this embodiment, the vortex generator 3 is coaxially arranged with the tube body 1. The working principle of this embodiment is similar to that of Embodiment 4, and the main difference is that: after the fluid in the central region of the tube body 1 passes through the solid spiral ribbon, a vortex flow is formed, thereby obtaining greater radial velocity and tangential rotational flow velocity, effectively improving the heat transfer rate and strength; at the same time, the adverse effects of the secondary vortex space-time evolution behavior formed and released by the back pressure side 26 of the rotational flow generating mechanism 2 and the rotational flow strength of the fluid near the wall of the tube body 1 are minimized. Compared with Embodiment 4, the scheme provided in this embodiment can effectively eliminate the low-temperature area of the fluid in the center of the heat transfer tube. The test results of the fluid flow and heat transfer characteristics of the series-coupled vortex enhanced heat transfer tube provided in this embodiment are summarized in Table 1.

[0108] Embodiment 6

[0109] In combination Figure 11 The difference between this embodiment and Embodiment 1 is that a conical ring is arranged on the downstream side of the variable-diameter rotational flow generating mechanism, the conical angle of the conical ring is 60°, the height of the conical ring in the axial direction of the tube body is 0.35 times the inner diameter of the tube body 1, the large diameter end of the conical ring is 0.8 times the inner diameter of the tube body 1, the small diameter end is 0.4 times the inner diameter of the tube body 1, and the large diameter end is connected to the rotational flow generating mechanism. The working principle of this embodiment is: the fluid that flows through the rotational flow generating mechanism 2 and exits from the flow outlet 23 has a rigid rotational flow built-in secondary vortex flow structure, after entering the conical ring, due to the effect of the conical ring, the flow channel is rapidly narrowed, the symmetrically distributed built-in double vortex of the fluid is forced to collide and merge into a single vortex, which causes a strong radial disturbance, greatly promoting the mixing of the fluid near the wall of the tube body 1 and the fluid in the central region of the tube body 1, and greatly improving the heat transfer rate and heat transfer strength; at the same time, the rigid rotational flow strength near the wall of the tube body 1 is less affected by the conical ring, and can still maintain a large tangential velocity to realize high-intensity rotational flow shearing action on the tube wall.

[0110] Table 1: Fluid flow and heat transfer characteristics of series-coupled vortex enhanced heat transfer tubes in Embodiments 1-6

[0111]

[0112] The preferred embodiments of the present application are described in detail above with reference to the drawings and examples, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application. In order to avoid unnecessary repetition, the present application does not further describe various possible combination manners. However, these simple modifications and combinations should also be regarded as the disclosed content of the present application, and all fall within the protection scope of the present application.

Claims

1. A series-coupled eddy current enhanced heat transfer tube, characterized in that, The series-coupled vortex-enhanced heat transfer tube includes a hollow tubular tube body (1), and a vortex generator (2) extending axially along the inner wall of the tube body (1). A vortex generator (3) is provided on the downstream side of the vortex generator (2) at a position away from the inner wall of the tube body (1). There is a fluid angle of attack between the vortex generator (3) and the flow direction of the fluid.

2. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, Multiple eddy current generators (3) are provided, and the multiple eddy current generators (3) are spaced apart in the radial section of the tube body (1) along the circumferential direction or the elliptical direction. Preferably, the fluid angle of attack is 0°-90°; Preferably, the distance between the eddy current generator (3) and the inner wall of the tube (1) is 0.1-0.5 times the inner diameter of the tube (1); Preferably, the vortex generator (3) is connected to the outflow end (23) of the vortex generating mechanism (2) via a stiffener (4).

3. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, The vortex generator (3) is an airfoil vortex generator, and the thickness of the airfoil vortex generator's blades is 0.5-2 times the wall thickness of the tube body (1). The radial dimension of the wing along the tube (1) is 0.05-0.4 times the inner diameter of the tube (1). The length of the wing along the axial direction of the tube (1) is 0.05-1 times the inner diameter of the tube (1); The angle between the bottom end of the wing and the tangent of the circle or ellipse formed by its arrangement in the radial section of the tube (1) is 0°-90°.

4. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, The eddy current generator (3) is a blunt-body type eddy current generator. The blunt-body structure of the blunt-body eddy current generator has a radial dimension of 0.05-0.4 times the inner diameter of the tube (1). The length of the blunt body structure along the axial direction of the tube (1) is 0.05-1 times the inner diameter of the tube (1); Preferably, the blunt body structure is provided with jet holes.

5. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, The vortex generator (3) is a solid spiral ribbon with a twist angle of 45-360°. The radial dimension of the solid spiral ribbon on the tube body (1) is 0.05-0.5 times the inner diameter of the tube body (1), and the axial dimension of the solid spiral ribbon on the tube body (1) is 0.05-1 times the inner diameter of the tube body (1). The twisting direction of the solid spiral ribbon is the same as or opposite to the twisting direction of the vortex generating mechanism (2).

6. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, The vortex generating mechanism (2) is a solid spiral ribbon or a hollow spiral ribbon; Preferably, the vortex generating mechanism (2) is a hollow spiral ribbon, and the vortex generating mechanism (2) includes at least one spiral blade, and at least part of the radial dimension of each spiral blade is arranged in a gradually changing manner in the axial direction of the tube body (1); Preferably, the twist angle of the helical blade is 90°-1080°, more preferably 180°-360°; Preferably, the height of the helical blade in the axial direction of the tube body (1) is 1-10 times the inner diameter of the tube body (1); Preferably, the radial dimensions of the inflow end (24) and the outflow end (23) of the spiral blade are 0-0.5 times the inner diameter of the tube body (1), more preferably 0-0.4 times; Preferably, the radial dimension of the incoming flow end (24) of the helical blade is smaller than the radial dimension of the outgoing flow end (23).

7. The series-coupled eddy current enhanced heat transfer tube according to claim 6, characterized in that, The helical blade has a first helical twisted section (241) near its inflow end (24) and a second helical twisted section (231) near its outflow end (23), wherein the helix angle of the first helical twisted section (241) is 0.1-5 times the helix angle of the second helical twisted section (231); Preferably, the helix angle of the first helical twisted segment (241) is greater than the helix angle of the second helical twisted segment (231).

8. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, The eddy current generator (3) is a conical ring; preferably, the conical ring is a circular conical ring or a pyramidal ring; Preferably, the radial dimension of the large-diameter end of the conical ring is 0.1-1 times the inner diameter of the tube body (1), and the radial dimension of the small-diameter end of the conical ring is 0.1-0.8 times the radial dimension of its large-diameter end; the cone angle of the conical ring is 10-80°, the length of the conical ring along the axial direction of the tube body (1) is 0.1-2 times the inner diameter of the tube body (1), and the thickness of the conical ring is 0.5-2 times the wall thickness of the tube body (1); Preferably, the radial dimension of the large-diameter end of the conical ring is 0.1-0.8 times the inner diameter of the tube body (1); Preferably, the surface of the conical ring is provided with jet holes, and the opening ratio of the jet holes on the conical ring is 1-20%; Preferably, the conical ring is arranged coaxially with the tube body (1).

9. The series-coupled eddy current enhanced heat transfer tube according to claim 1, characterized in that, The swirl generating mechanism (2) and the vortex generator (3) located downstream of the swirl generating mechanism (2) constitute a turbulence assembly. Multiple sets of the turbulence assembly are provided, and the multiple sets of the turbulence assembly are spaced apart in the axial direction of the tube body (1). Preferably, the distance between two adjacent flow-disrupting components is 10-100 times the inner diameter of the tube (1); Preferably, the spiral twisting directions of the spiral blades of the swirl generating mechanism (2) included in two adjacent swirl components are opposite.

10. A pyrolysis furnace, characterized in that, The pyrolysis furnace includes a radiation chamber, in which at least one radiation furnace tube assembly is installed. The radiation furnace tube assembly includes a plurality of radiation furnace tubes arranged in sequence and a heat transfer tube connecting adjacent radiation furnace tubes. The heat transfer tube is a series-coupled eddy current enhanced heat transfer tube as described in any one of claims 1-9.

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