Non-equal-interval arrangement type discrete double-inclined inner rib reinforced heat exchange tube

Abstract

The invention relates to the technical field of supercritical horizontal flow enhanced heat exchange, in particular to a non-equal-interval arrangement type discrete double-inclined inner rib enhanced heat exchange tube which is characterized in that discrete rib structures with bidirectional inclined angles are arranged on the inner wall of a supercritical horizontal heat exchange tube in the circumferential direction at non-equal intervals, and the included angle between the axis of each rib and the axis of the tube is + / -(30-60) degrees; the positive number is inclined in the right-handed rotation direction, the negative number is inclined in the left-handed rotation direction, the normal height of the fins is smaller than or equal to 0.2 d, the circumferential width is smaller than or equal to 0.5 d, the axial length is smaller than or equal to 2d, and d is the hydraulic inner diameter of the base pipe. Multi-scale vortexes are induced through the double inclined fins which are arranged in the circumferential direction of the tube wall at non-equal intervals, mixing of cold and hot fluid can be more effectively promoted compared with DDIR under the supercritical working condition, development of a thermal boundary layer is restrained, adaptability to the thermally induced buoyancy force effect is improved, and therefore higher heat exchange performance is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of supercritical horizontal flow enhanced heat exchange, and in particular to a non-equidistantly arranged discrete double-oblique inner rib enhanced heat exchange tube. Background Art

[0002] Medium and low temperature waste heat accounts for more than half of the total industrial waste heat. Efficient recovery and utilization of medium and low temperature waste heat resources is crucial to building a clean and low-carbon energy system. The transcritical organic Rankine cycle (T-ORC) is a technology for efficient recovery of medium and low temperature waste heat. Its core equipment is the heat exchanger, which is usually arranged horizontally. Supercritical fluids have unique thermal properties. During horizontal flow, circumferential thermal unevenness is prone to occur, resulting in local overheating, affecting heat exchange efficiency and system safety.

[0003] Traditional horizontal smooth tubes (ST) cannot effectively suppress the thermally induced buoyancy effect due to the lack of spoiler elements, resulting in serious circumferential thermal unevenness and low heat transfer efficiency. Although the internally threaded tube (IRT) can enhance disturbance, the arrangement of continuous ribs is not very sensitive to the thermally induced buoyancy effect, making it difficult to effectively improve the circumferential thermal unevenness. For the discrete double inclined internal fin tube (DDIR), due to its symmetrically arranged inclined discrete fins, it can effectively enhance disturbance, promote the mixing of cold and hot fluids, and improve heat transfer performance. At the same time, it maintains a small pressure drop in the tube and has excellent comprehensive performance under subcritical conditions, but has limited effect on improving the supercritical circumferential thermal unevenness.

[0004] Compared with the prior art, the present invention can greatly enhance the eddy strength, enhance the turbulent disturbance, more effectively destroy the fluid boundary layer, significantly improve the problem of circumferential thermal unevenness and improve the heat exchange efficiency by arranging discrete double oblique inner ribs on the inner wall of the horizontal heat exchange tube at non-uniform intervals along the circumference, which is superior to DDIR and other heat exchange enhancement elements under supercritical heat exchange conditions, while maintaining a low flow resistance of the fluid, and will not significantly increase the pressure drop of the fluid while improving the heat exchange efficiency. The asymmetric fin layout suppresses the formation of the near-wall recirculation zone, effectively controls the fouling deposition and improves the operational reliability. The multi-dimensionally adjustable rib structure parameters (spacing / height / inclination) realize adaptive matching of the working conditions, and the compact design combined with the discrete molding process significantly reduces the equipment volume and manufacturing cost while ensuring the heat exchange efficiency. The present invention is suitable for a variety of supercritical fluid horizontal flow heat exchange occasions, such as T-ORC systems, supercritical organic working fluid heat exchangers, etc., and has broad application prospects. Summary of the invention

[0005] The purpose of the present invention is to provide a discrete double oblique inner rib reinforced heat exchange tube with non-equidistant arrangement, so as to further improve the heat exchange performance of the discrete double oblique inner rib reinforced heat exchange tube in the horizontal flow of supercritical fluid. The discrete double oblique inner rib reinforced heat exchange tube with non-equidistant arrangement has a discrete fin structure with bidirectional inclination angles arranged at non-equidistant intervals along the circumference of the inner wall of the heat exchange tube. By inducing multi-scale vortices with double oblique fins arranged at non-equidistant intervals along the circumference of the tube wall, it can more effectively promote the mixing of cold and hot fluids, inhibit the development of thermal boundary layers, and improve the adaptability to thermally induced buoyancy effects under supercritical conditions compared to DDIR, thereby achieving higher heat exchange performance.

[0006] Taking Example 1 as an example, the structure adopts a 30° right-handed fin group densely arranged in the top area and a left-handed fin group sparsely arranged in the bottom area, forming a differentiated rib parameter layout (see Figure 3 ), forming a three-dimensional spiral secondary flow field (see Fig.11 Velocity vector cloud diagram) Through the three-dimensional spiral secondary flow field and orthogonal vortex interference mechanism, a velocity gradient perpendicular to the buoyancy direction is generated on the tube section, which effectively destroys the thermal stratification boundary layer, causing the working fluid to undergo 3-5 periodic reversing movements, and the turbulent mixing path is increased by more than 40% compared with the traditional symmetrical fins (comparison Fig.11 Streamline distribution). In terms of geometric parameter design, when the rib height-to-tube diameter ratio h=0.05d, the circumferential width W and the axial length L meet the W / L≤0.25 constraint to avoid flow separation and heat transfer dead zone; the axial projection overlap ratio δ=1-(p / L)cosα is controlled in the range of 30%-70% to ensure the dynamic matching of the flow field disturbance intensity and the thickness of the physical property mutation layer.

[0007] Taking Example 1 as an example: When R134a is in the quasi-critical zone of 4.26MPa, the optimal overlap rate is 55%, which makes the turbulence integral scale match the thickness of the specific heat capacity mutation layer, and the circumferential coverage angle φ and the rib inclination angle α satisfy the relationship φ≥2α, so that the standard deviation of the wall heat flux density is reduced by 35%. The structure achieves a 2.3-fold increase in the local Nusselt number in the quasi-critical zone of supercritical R134a, and the comprehensive performance coefficient (PEC) reaches 1.6-2.5 times that of the horizontal light tube, and the increase in the friction resistance coefficient is controlled within 15% (see Fig.10 Performance comparison). Through the asymmetric vortex interference mechanism and parameter optimization matching, the present invention effectively optimizes the problem of insufficient adaptability of traditional enhanced tubes to thermally induced buoyancy effect, and is particularly suitable for T-ORC systems and supercritical organic working fluid heat exchangers.

[0008] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0009] A non-equidistantly spaced discrete double-inclined inner rib enhanced heat exchange tube comprises: a discrete fin structure with bidirectional inclination angles is arranged non-equidistantly along the circumferential direction on the inner wall of a supercritical horizontal heat exchange tube, the angle between the fin axis and the tube axis is ±(30-60) degrees, a positive sign indicates a right-handed inclination, a negative sign indicates a left-handed inclination, the normal height of the fin is ≤0.2d, the circumferential width is ≤0.5d, the axial length is ≤2d, and d is the hydraulic inner diameter of the base tube.

[0010] Furthermore, the circumferential arrangement of the double oblique inner ribs is one or a combination of the following arrangements: non-uniform spacing along the circumference, but symmetrical along the gravity direction; non-uniform spacing along the circumference, but symmetrical along the axial horizontal symmetry plane; non-uniform spacing along the circumference and asymmetrical arrangement.

[0011] Furthermore, the axis of the double inclined inner rib forms an angle including but not limited to ±(30-60) degrees with the axis of the base pipe, wherein a positive sign indicates a right-handed inclination and a negative sign indicates a left-handed inclination.

[0012] Furthermore, the angle between the axis of the double-oblique inner rib and the axis of the base pipe can be the same or different for different fins.

[0013] Furthermore, the inclination directions of different ribs of the double inclined inner ribs may be the same or different.

[0014] Furthermore, the projections of the double oblique inner ribs along the axial direction may be parallel, staggered, or a combination of the two.

[0015] Beneficial effects of the present invention:

[0016] The present invention arranges discrete double inclined inner ribs at unequal intervals along the circumference of the inner wall of the heat exchange tube, and combines the design of a bidirectional inclination angle of ±(30-60)° between the fin axis and the tube axis, thereby inducing the formation of an asymmetric multi-scale vortex structure in the circumferential flow of the fluid. Among them, the non-uniformly spaced distribution of the fins breaks the periodic disturbance pattern produced by traditional equally spaced fins, and the fin spacing is differentially arranged in the direction of gravity (top / bottom) (for example, the fin arrangement density in the top area is higher than that in the bottom area), and a dense group of fins is used to generate high-intensity local vortices in the buoyancy-dominated area, which directly impacts the thermal stratification boundary layer; and the reverse swirl generated by the bidirectionally inclined fins forms staggered vortex pairs on the tube cross section, enhancing the three-dimensional mixing of cold and hot fluids. Fig.11 As shown in the figure, the structure forms a small-scale vortex at the top to accelerate the peeling of the high-temperature fluid near the wall, and at the same time generates a large-scale vortex at the bottom to promote the penetration of the mainstream low-temperature working fluid into the wall. The dual effect significantly reduces the circumferential temperature gradient. Compared with the limitation of DDIR symmetrical equidistant fins that only produce a single vortex, the asymmetric vortex generation mechanism of the present invention specifically weakens the local overheating phenomenon at the top caused by buoyancy, reducing the temperature unevenness of the same cross section by more than 50%.

[0017] The normal height of the fins of the present invention is strictly limited to ≤0.2d (hydraulic diameter of the base pipe), ensuring that the fin disturbance depth penetrates the viscous bottom layer to destroy the development of the thermal boundary layer, while avoiding a sharp increase in pressure loss caused by fluid separation due to excessive rib height. The design of circumferential width ≤0.5d combined with non-equidistant spacing arrangement forms a wide rib-narrow gap combination structure locally, utilizing the strong flow-guiding effect of the wide ribs and the acceleration effect of the narrow gaps to enhance the near-wall turbulent kinetic energy generation rate; and the discrete fin layout with an axial length of ≤2d controls the overlap ratio (30-70%) of the axial projections of adjacent fins to avoid the generation of flow dead zones while maintaining continuous disturbance. This parameter system matches the high compressibility and low Prandtl number characteristics of supercritical fluid in the quasi-critical region, and the turbulent pulsation scale generated by the fins is adapted to the spatial distribution of the region where the fluid properties change drastically, so that under strong buoyancy conditions (q / G≥0.1kJ / kg), the comprehensive heat transfer performance coefficient (PEC) reaches 1.6-2.5 times that of a horizontal light tube, and the increase in the friction resistance coefficient is controlled within 15%.

[0018] The present invention adopts a non-uniformly spaced and asymmetrical fin arrangement strategy along the circumferential direction (such as Figure 5 , Figure 6 ), forming a non-uniform velocity field distribution in the near-wall area, using the high shear stress generated by the dense fins on the top to peel off the initial dirt particles, while the low-speed recirculation zone formed by the sparse fins on the bottom promotes the secondary suspension of particles, avoiding the local accumulation of sediments in the direction of gravity. In addition, the discrete layout of the bidirectional inclined fins reduces the risk of thermal stress concentration in the continuous rib structure, and the root of the fin adopts a gradient fillet design (such as Figure 3 Local amplification) makes the stress distribution uniform, and the fatigue life under periodic thermal shock load is increased by more than 40%. This feature is especially suitable for the coking condition in supercritical organic working fluid heat exchangers. After long-term operation, the fouling thermal resistance is reduced by 30%-50% compared with traditional internal threaded pipes.

[0019] The present invention forms a multi-dimensional parameterized design space by independently regulating the circumferential spacing distribution pattern of the fins (symmetrical / asymmetrical), the inclination angle (variable from ±30 to 60°) and the axial projection relationship (parallel / staggered). For example, in a horizontally arranged evaporator, an asymmetric staggered layout with a top fin inclination angle of 60° right-handed and a bottom fin inclination angle of 45° left-handed can be adopted to enhance the ability to suppress vapor-liquid separation during the phase change process; while in the condenser, a parallel fin arrangement with partially overlapping axial projections is adopted to optimize the distribution of the condensate film. This flexible design can be achieved through CNC multi-axis linkage of a single rolling die (such as Figure 7 , Figure 8), the dynamic matching algorithm of the mold lead and the tube feed speed ensures the forming accuracy of non-uniformly spaced fins (circumferential angle deviation ≤ ±1°), which is more than 3 times the processing efficiency of traditional equally spaced fins, and there is no need to add subsequent finishing steps, which significantly reduces the cost of large-scale production.

[0020] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the structure of a non-uniformly spaced discrete double oblique inner rib enhanced heat exchange tube;

[0023] Figure 2 for Figure 1 A~A section diagram in;

[0024] Figure 3 for Figure 2 A partial enlarged view of B in the middle;

[0025] Figure 4 for Figure 1 A schematic diagram of a partial circumferentially unfolded structure;

[0026] Figure 5 It is a schematic diagram of the radial cross-section structure of another non-uniformly spaced discrete double-oblique inner rib enhanced heat exchange tube.

[0027] Figure 6 It is a schematic diagram of the radial cross-section structure of another non-uniformly spaced discrete double-oblique inner rib enhanced heat exchange tube.

[0028] Figure 7 This is a schematic diagram of the partial circumferential expansion structure of another non-uniformly spaced discrete double-oblique inner rib enhanced heat exchange tube.

[0029] Figure 8 This is a schematic diagram of the partial circumferential expansion structure of another non-uniformly spaced discrete double-oblique inner rib enhanced heat exchange tube.

[0030] Figure 9 is a comparison of the global thermal characteristics of a non-uniformly spaced discrete double-inclined inner rib enhanced heat exchange tube and a DDIR horizontal heat exchange tube under the influence of strong buoyancy conditions (relative to the range of research conditions), a is a comparison of the wall temperature distribution along the process under the research conditions, and b is a comparison of the heat transfer coefficient (HTC) distribution along the process.

[0031] Fig.10 It is a comparison chart of the comprehensive heat transfer performance and friction resistance coefficient of discrete double inclined inner rib enhanced heat exchange tubes and DDIR horizontal heat exchange tubes with different non-uniform spacing arrangements under the influence of strong and medium buoyancy lift conditions (relative to the range of research conditions).

[0032] Fig.11 This is a comparison diagram of the flow field, swirl intensity and temperature field of a non-uniformly spaced discrete double inclined inner rib enhanced heat exchange tube and a DDIR horizontal heat exchange tube under strong buoyancy conditions (relative to the range of research conditions) in the same radial section. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Figure 1 As shown, the inner wall of the tube is circumferentially arranged with non-equidistant discrete fin structures having bidirectional inclination angles, and the double inclined inner ribs are circumferentially arranged with non-equidistant and asymmetrical spacing.

[0036] The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube is a structure of discrete fins with bidirectional inclination angles arranged at non-equidistant intervals on the inner wall of the horizontal heat exchange tube. The angle between the fin axis and the tube axis is ±(30-60) degrees. The positive sign indicates inclination in the right-hand direction, and the negative sign indicates inclination in the left-hand direction. The normal height of the fin is ≤0.2d, the circumferential width is ≤0.5d, and the axial length is ≤2d (d is the hydraulic inner diameter of the base tube). The manufacture of the non-equidistant discrete double-inner-rib tube can be based on ordinary plain tubes, low-rib tubes or threaded tubes, and a non-continuous rib structure is formed on the tube wall through molding and rolling processes; the inner ribs can also be directly formed when rolling seamless tubes or welding seam tubes. Compared with the DDIR horizontal heat exchange tube, the non-equidistantly spaced discrete double-inner-rib tube significantly enhances turbulent disturbances and promotes radial mixing of cold and hot fluids through the design of non-equidistantly spaced fins along the circumference, effectively suppressing the circumferential thermal unevenness caused by buoyancy in supercritical horizontal flow.

[0037] In this embodiment, if Figure 1 , Figure 2 and Figure 4 As shown, 1 is a discrete double oblique inner rib arranged at non-equidistant intervals in the tube. Figure 1Where d is the hydraulic inner diameter of the heat exchange tube, L is the axial length of a single double-inclined inner rib, C is the angle between the double-inclined inner rib and the axis, C 1 The circumferential arrangement angle of the fins is 30 degrees. Figure 3 In the figure, h is the normal height of the double-slanted inner rib, and W is the circumferential width of the double-slanted inner rib. L = 0.3d, h = 0.05d. C ≈ ± (30-60) degrees, positive values ​​indicate right-hand rotation, and negative values ​​indicate left-hand rotation.

[0038] Example 2

[0039] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Figure 5 The radial cross-section of another non-uniformly spaced discrete double oblique inner rib enhanced heat exchange tube is shown in FIG2 . 2 is a non-uniformly spaced discrete double oblique inner rib in the tube. The double oblique inner rib in the tube is arranged in a non-uniformly spaced manner along the circumference of the inner wall of the tube, but is arranged symmetrically along the gravity direction. C 2 is 60 degrees, C 3 It is 30 degrees.

[0040] Example 3

[0041] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Figure 6 The radial cross-section of another non-uniformly spaced discrete double oblique inner rib enhanced heat exchange tube is shown. 3 in the figure is a non-uniformly spaced discrete double oblique inner rib in the tube. The double oblique inner rib in the tube is arranged non-uniformly along the circumference of the inner wall of the tube, but is arranged symmetrically along the axial horizontal symmetry plane. 4 is 60 degrees, C 5 It is 30 degrees.

[0042] Example 4

[0043] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Figure 7 Another partial circumferential development diagram of a non-uniformly spaced discrete double oblique inner rib enhanced heat exchange tube is shown, 4 is a non-uniformly spaced discrete double oblique inner rib arrangement in the tube, and the double oblique inner ribs in the tube are staggered along the axial direction.

[0044] Example 5

[0045] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Figure 8 Another partial circumferential expansion diagram of a non-uniformly spaced discrete double oblique inner rib enhanced heat exchange tube is shown, 5 is a non-uniformly spaced discrete double oblique inner rib arrangement in the tube, and the angles between the 1st and 4th rows and the 2nd and 3rd rows of double oblique inner ribs in the tube and the axis are different, which are 30 degrees and 60 degrees respectively.

[0046] Example 6

[0047] The present embodiment describes a non-uniformly spaced discrete double-inner-rib enhanced heat exchange tube, as shown in FIG9 , which is a non-uniformly spaced asymmetric discrete double-inner-rib enhanced heat exchange tube and a DDIR horizontal heat exchange tube in Example 1 under strong buoyancy conditions (working fluid is R134a, P=4.26MPa, inlet temperature T in =343K, q / G=0.1kJ / kg). From the wall temperature distribution along the process, it can be seen that the wall temperature along the process does not show obvious periodic fluctuations similar to the DDIR horizontal heat exchange tube. UA significantly reduces the local high temperature area at the top of the horizontal heat exchange tube, and the average wall temperature at the top and bottom are lower than DDIR. In the distribution of heat transfer coefficient (HTC) along the process, UA has been significantly improved compared with ES, both at the top and bottom. Under the strong buoyancy supercritical heat exchange conditions within the research scope, the non-uniformly spaced discrete double inclined inner rib enhanced heat exchange tube has better performance in improving the circumferential thermal unevenness of the supercritical horizontal heat exchange tube wall and improving convective heat transfer.

[0048] Example 7

[0049] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Fig.10 As shown, it is a comparison diagram of the comprehensive heat transfer performance and friction resistance coefficient CFD results of different non-uniformly spaced discrete double oblique inner rib enhanced heat exchange tubes and DDIR under the influence of strong and medium buoyancy lift within the research working range (working fluid is R134a, P = 4.26MPa, inlet temperature Tin = 343K, q / G = 0.1kJ / kg, q / G = 0.056kJ / kg), ES represents a DDIR horizontal heat exchange tube, EA represents a horizontal heat exchange tube with fins arranged at equal spacing but asymmetrically along the circumferential direction, US and UA are the horizontal heat exchange tubes of Example 3 and Example 1, respectively, where the heat transfer enhancement factor Nu / f is 1 / 3 The comprehensive heat transfer performance evaluation index PEC reflects the comprehensive efficiency improvement of the four types of layouts, and f reflects the magnitude of the flow resistance of supercritical R134a in the tube. Non-uniform spacing layout (such as US and UA) will increase the flow resistance in the tube and thus cause an increase in f, but the flow resistance is not much different from that of the rib equal spacing layout (such as ES and EA). The three rib layouts are all better than DDIR in Nu / f 1 / 3 There are different degrees of improvement in PEC, among which the comprehensive improvement effect of UA horizontal heat exchange tube is the most obvious. Within the working conditions studied, its comprehensive performance coefficient (PEC) can reach 1.6-2.5 times that of horizontal light tube (ST).

[0050] Example 8

[0051] The present embodiment describes a non-equidistantly spaced discrete double-oblique inner rib enhanced heat exchange tube, such as Fig.11The figure shows the comparison of the CFD simulation results of the flow field, swirl intensity and temperature field of the same radial section of the non-equally spaced discrete double oblique inner rib enhanced heat exchange tube and the DDIR horizontal heat exchange tube in the strong buoyancy condition (the working fluid is R134a, P = 4.26MPa, the inlet temperature Tin = 343K, q / G = 0.1kJ / kg) of Example 1. ES represents the DDIR horizontal heat exchange tube, and UA represents the non-equally spaced asymmetric discrete double oblique inner rib enhanced heat exchange tube of Example 1. For DDIR, the working fluid flow generates a vortex in the radial section of the tube, and only generates a strong swirl intensity near the wall, resulting in a large radial temperature gradient in the tube; while for UA, the non-equally spaced fin arrangement design makes the working fluid form two vortices of different sizes at the bottom and top of the tube when flowing in the tube, which better promotes the mixed heat exchange between the hot fluid near the wall and the cold fluid in the center of the mainstream, and the uniformity of the temperature field in the section is significantly improved.

[0052] The best implementation method for the non-uniformly spaced discrete double oblique inner rib reinforced heat exchange tube is rolling or compression molding. One of the manufacturing processes for heat exchange tubes with discontinuous bidirectional spiral ribs inside the tube and smooth outer wall is similar to the manufacturing process of internally threaded and externally smooth tubes; the second manufacturing process is to reprocess (cold drawing, etc.) the discontinuous inner bidirectional spiral rib and outer bidirectional spiral groove heat exchange tube formed by rolling or compression molding. The manufacturing efficiency of the rolling or compression molding method of the discontinuous double oblique inner rib heat exchange tube is several times higher than that of ordinary spiral groove, transverse groove and threaded surface heat exchange tubes. This is due to the advantages brought by the discontinuity of the oblique ribs, so its manufacturing cost is also reduced accordingly.

[0053] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A non-uniformly spaced discrete double-oblique inner rib enhanced heat exchange tube, characterized in that: include: Discrete fin structures with bidirectional inclination angles are arranged at unequal intervals along the circumferential direction on the inner wall of the supercritical horizontal heat exchange tube. The angle between the fin axis and the tube axis is ±(30-60) degrees, the positive sign indicates inclination in the right-handed direction, and the negative sign indicates inclination in the left-handed direction. The normal height of the fin is ≤0.2d, the circumferential width is ≤0.5d, and the axial length is ≤2d, where d is the hydraulic inner diameter of the base tube.

2. The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube according to claim 1, characterized in that: The arrangement of the double oblique inner ribs along the circumferential direction is one or a combination of the following arrangements: non-uniform spacing along the circumferential direction, but symmetric along the gravity direction; non-uniform spacing along the circumferential direction, but symmetric along the axial horizontal symmetry plane; non-uniform spacing along the circumferential direction and asymmetrical arrangement.

3. The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube according to claim 1, characterized in that: The axis of the double inclined inner rib forms an angle including but not limited to ±(30-60) degrees with the axis of the base pipe, wherein a positive sign indicates a right-handed inclination and a negative sign indicates a left-handed inclination.

4. The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube according to claim 1, characterized in that: The angle between the axis of the double-oblique inner rib and the axis of the base pipe is the same for different fins.

5. The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube according to claim 1, characterized in that: The angle between the axis of the double-inclined inner rib and the axis of the base pipe is different for different fins.

6. The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube according to claim 1, characterized in that: The inclination directions of different ribs of the double inclined inner ribs are the same.

7. The non-equidistantly spaced discrete double oblique inner rib enhanced heat exchange tube according to claim 1, characterized in that: The inclination directions of different ribs of the double inclined inner ribs are different.

8. The non-equidistantly spaced discrete double-inner-rib enhanced heat exchange tube according to claim 1, characterized in that: The projections of the double oblique inner ribs along the axial direction are parallel, staggered or a combination of the two.

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