CN101182977A - Internal cross spiral external three-dimensional diamond rib double-sided enhanced heat transfer tube - Google Patents

Abstract

The invention discloses a double-sided strengthened heat transfer tube with internal cross spiral external three-dimensional rhombic ribs, comprising a heat transfer tube base, tube external rhombus ribs and tube internal spiral grooves, the heat transfer tube base, tube external rhombic ribs and tube inner The spiral groove is an integrated structure. The diamond-shaped ribs outside the tube are interrupted from each other, and are distributed in a spiral shape along the axial direction to form a three-dimensional extended surface of the entire outer surface of the tube wall. Occurs in pairs. The invention utilizes the three-dimensional diamond-shaped ribs outside the tube to increase the heat transfer area while destroying the stagnant boundary layer, improving the convective heat transfer coefficient and the condensation heat transfer coefficient, and at the same time, the spiral grooves in the tube can induce secondary separation flow, thereby promoting the intensification of turbulent flow, improving the convective heat transfer coefficient in the tube, and increasing the anti-scaling ability. In addition, the invention has a wide range of applications, and under the same heat exchange conditions, has a compact structure and saves metal materials.

Description

Internal cross spiral external three-dimensional diamond rib double-sided enhanced heat transfer tube

technical field

The invention relates to an enhanced heat transfer tube, in particular to an inner cross helical outer three-dimensional rhombic rib double-sided enhanced heat transfer tube.

Background technique

Shell-and-tube heat exchangers are currently the most widely used heat exchange equipment, and they are commonly found in industrial fields such as energy and power, petrochemical, and metallurgical materials. It is also the key equipment for rational utilization and conservation of existing energy and development of new energy, accounting for about 70% of all heat exchangers. In order to reduce the weight of the shell-and-tube heat exchanger, reduce the volume of heat exchange equipment, save energy and reduce consumption, efforts should be made to strengthen its heat transfer process. Among them, changing the basic element of the shell-and-tube heat exchanger, the heat transfer tube, from a smooth tube to an enhanced heat transfer tube is the main way to achieve efficient and compact heat transfer.

At present, the more commonly used enhanced heat transfer tubes include spiral grooved tubes, spiral horizontal lines (threaded tubes), twisted oval tubes, spiral grooved tubes, horizontally grooved corrugated tubes, corrugated tubes, inner finned tubes, and tubes inserted with strengthening materials, but they Each has its own characteristics and scope of application. The spiral groove tube is machined by rolling, forming a spiral groove on the outer surface of the tube, and a corresponding spiral protrusion on the inner surface of the tube, so that the fluid in the tube can be partially rotated, which is conducive to thinning the boundary layer, and through periodic disturbance To destroy the turbulent boundary layer, it is mainly used in the heat transfer of single-phase fluid. The heat transfer mechanism and characteristics of the spiral groove (thread pipe) and the spiral groove pipe are similar to the spiral groove pipe, and they are all suitable for low Re (Reynolds number) heat transfer. Thermal strengthening has a more obvious effect, but the heat transfer enhancement for high Re is not significant. The corrugated pipe is a thin-walled carbon steel pipe or stainless steel pipe processed into a continuous corrugated curve inside and outside by a special mold, and its longitudinal section waveform is composed of large and small arcs tangent to each other. This kind of heat transfer tube has a certain self-cleaning function, and the anti-scaling ability is better. However, the heat transfer performance is not as good as that of the spiral groove tube under the same Re. In addition, there are some disadvantages as follows: (1) the flow resistance in the pipe generated is large and the pressure drop is large; (2) the pressure bearing capacity is only about 1/10 of that of a smooth pipe, and it cannot be applied to medium and high pressure occasions; (3) in low Re In the case of high viscosity fluid heat exchange, the effect of enhancing heat transfer is not obvious. (4) When used for falling film evaporation, splashing and detachment of the liquid film tend to occur when the flow rate is large, and the heat transfer performance decreases. The twisted elliptical tube is made by two processes of flattening and twisting. Any section of the tube is oblong. It is a spirally twisted elliptical section tube. The heat transfer mechanism is enhanced through the spirally twisted elliptical channel inside the tube Make the fluid generate rotation and secondary vortex disturbance. The disadvantages of this kind of heat transfer tube: First, the heat transfer enhancement effect on low Re is not obvious. Only at high Re, compared with smooth round tubes, the convective heat transfer coefficient in twisted oval tubes can be increased by 35%- 55%; the second is that while the heat transfer is enhanced, the internal resistance of the tube also increases, and the increase is quite large. Inner-finned tubes and tubes are inserted with strengthening materials, such as double-helical spring tubes, which are mainly used for single-convection heat transfer and phase-change heat transfer in the tube. The increase of the heat transfer surface area, the contribution of the two to the heat transfer is roughly equal, the disadvantage is that the surface of the inner fin of the tube is easy to foul. The double-helical spring tube is processed into a double-helical spring by using thin spring wire, and the double-helical spring is welded to the tube wall by brazing process, so as to realize the enhancement of heat transfer. The laminar flow heat transfer enhancement effect is remarkable, but the internal resistance of the tube increases It is also more obvious and more suitable for heat transfer of clean media.

In many shell-and-tube heat exchangers, such as high-pressure feed water heaters and low-pressure feed water heaters widely used in power production, the convective heat transfer coefficient of the feed water inside the tube is equivalent to the condensation heat transfer coefficient of the steam outside the tube, thus strengthening the The heat transfer of the type heat exchanger must use double-sided enhanced heat transfer tubes. However, in heat exchangers such as oil coolers widely used in rolling stock, heavy machinery, and generators, the convective heat transfer coefficient of the water side in the tube is much greater than the convective heat transfer coefficient of the oil side of the shell side, and the heat transfer resistance is at the shell side ( Therefore, the heat transfer tube used for the oil cooler should adopt double-sided enhanced heat transfer tubes, and the heat transfer coefficient outside the tube should be higher than the heat transfer coefficient inside the tube. However, the above-mentioned enhanced heat transfer tubes can only enhance heat transfer on one side, or the heat transfer coefficients on both sides of the enhanced heat transfer do not meet the requirements.

Theoretical research shows that for heat exchangers with high viscosity and low flow rate, intermittent high-fin heat transfer tubes, spiral grooved tubes, spiral stripes (threaded tubes), twisted oval tubes, spiral grooved tubes, etc. should be used to enhance heat transfer. There are no intersecting fins outside the tube of the transverse grooved pipe and corrugated pipe. The patent applicant of the present invention once proposed a double-sided enhanced heat transfer tube with internal spiral and external ratchet (Chinese patent, ZL03274468.4). Finning and rolling are formed on the outer surface of the tube, and curved ratchet fins are formed on the surface of the tube to improve the heat transfer coefficient outside the tube. Due to structural reasons, the height of the ratchet fins of this heat transfer tube is small, and the spiral groove in the tube is unidirectional. For high viscosity, such as the single convective heat transfer of oil, the enhanced heat transfer efficiency still has a certain limit, and the fouling in the tube has not been solved well. So far, there has not been an enhanced heat exchange tube that can meet the heat transfer requirements inside and outside the tube and prevent scaling, and has a simple structure and saves materials, so that the use of shell and tube heat exchangers is limited. limits.

Contents of the invention

The purpose of the present invention is to overcome the defects in the prior art that the heat transfer effect inside and outside the tube cannot be considered, the heat transfer coefficient is low, the anti-scaling and anti-scaling functions are poor, and the consumption of metal plates is large, and to provide a three-dimensional diamond-shaped rib with internal cross spiral external Enhanced heat transfer tubes on both sides.

The present invention can be realized through the following technical solutions: a double-sided reinforced heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs, including a heat transfer tube base, tube outer rhombus ribs and tube inner spiral grooves, the heat transfer tube base, The outer diamond-shaped ribs and the inner spiral grooves are an integrated structure. The outer diamond-shaped ribs are interrupted from each other and spirally distributed along the axial direction to form a three-dimensional extended surface of the entire outer surface of the tube wall. The inner spiral grooves are distributed across the heat transfer tube. In the matrix, they appear in pairs in a left-right direction.

The pipe outer diamond-shaped ribs of the present invention are formed by intersecting left-handed multi-headed convex rectangular threads and right-handed concave single-headed or multi-headed rectangular threads, or formed by right-handed multi-headed convex rectangular threads and left-handed concave single-headed or multi-headed The rectangular threads are formed by intersecting each other and are perpendicular to the axis of the pipe or the outer wall of the pipe. The pitch of the convex rectangular thread is greater than the pitch of the concave rectangular thread, the pitch of the convex rectangular thread is 100-200mm, and the pitch of the concave rectangular thread is 20-50mm. The helix angle β of the convex rectangular thread is 60°-80°, and the helix angle α of the concave rectangular thread is 110°-150°. The axial cross-section widths of the rectangular threads are equal or unequal, and the volumes of the formed diamond-shaped ribs are correspondingly equal or unequal. The axial spacing of the diamond-shaped ribs is 0.5-3.5mm, the thickness of the diamond-shaped ribs is 0.7-2.5mm, and the height of the diamond-shaped ribs is 1.2mm-4.5mm.

The helical groove in the pipe according to the present invention is formed by intersecting a left-handed concave single-head or multi-head helical groove and a right-handed concave single-head or multi-head helical groove, and the pitch of the left and right helical grooves is 2～ 6mm, groove depth 0.20mm ~ 2.5mm. The cross-sectional shape of the helical groove in the pipe is trapezoidal, arc-shaped, triangular, rectangular or polygonal, and the left helix angle θ1 and the right helix angle θ2 of the helical groove in the pipe are equal or unequal, and the left helix angle θ1 and the right helix angle θ2 are equal. It is 75°～85°.

The materials of the heat transfer tube base body, tube outer diamond-shaped ribs and tube inner spiral grooves in the present invention are copper, copper alloy, aluminum, aluminum alloy tube, carbon steel or other metal materials.

Compared with the prior art, the present invention has the following advantages:

1. The diamond-shaped ribs outside the tube, the spiral grooves inside the tube and the tube base of the present invention are an integrated structure without contact thermal resistance. Interrupted diamond-shaped ribs are used outside the tube to enhance convective heat transfer or condensation heat transfer, and cross-helical grooves are used inside the tube The groove enhances convective heat transfer, which can fully take into account the requirements for enhanced heat transfer inside and outside the tube;

2. The invention utilizes the three-dimensional diamond-shaped ribs outside the tube to increase the heat transfer area while destroying the stagnant boundary layer, thereby improving the convective heat transfer coefficient and the condensation heat transfer coefficient;

3. The intersecting helical grooves in the tube of the present invention can induce secondary separation flow, thereby promoting the intensification of turbulent flow, improving the convective heat transfer coefficient in the tube, increasing the anti-scaling ability, and maintaining long-lasting excellent heat transfer performance;

4. Compared with smooth tubes with the same diameter parameters, the present invention can increase the total heat transfer coefficient of a single tube by more than 120% under condensation conditions, and increase the total heat transfer coefficient by 80% under convective heat transfer conditions per unit area. % or more, but the pressure drop inside the tube does not increase significantly. Under the same heat transfer conditions, the structure is compact and saves metal materials. It is a high-efficiency double-sided enhanced heat transfer tube, which can be widely used on the outside of the tube with a small heat transfer film coefficient. occasions.

Description of drawings

Fig. 1 is a three-dimensional structural diagram of the present invention;

Fig. 2 is a partial three-dimensional structural diagram of the present invention;

Fig. 3 is an axial view of the present invention;

Fig. 4 is the front view of the present invention;

Fig. 5 is a schematic axial sectional view of the present invention.

Explanation of marks in the attached drawings:

1-diamond rib; 2-heat transfer tube base; 3-spiral groove;

t-the height of the rhombus fins outside the pipe wall; β-the helix angle of the convex rectangular thread;

α-concave rectangular thread helix angle;

δ1-the axial width of the diamond-shaped fins outside the pipe wall; δ2-the axial spacing of the diamond-shaped fins outside the pipe wall;

θ1-left helix angle of the helical groove; θ2-right helix angle of the helical groove;

F1-lead (or pitch) of the left helical groove; F2-lead (or pitch) of the right helical groove;

b-groove depth of the helical groove

Detailed ways

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the outer surface of the pipe wall is a diamond-shaped rib according to the present invention, and the inner surface is a cross helical groove. Views, Fig. 4 has provided the front view of the present invention, Fig. 5 has provided the axial sectional schematic view of the present invention. The invention combines the advantages of spiral grooved tubes, spiral grooved tubes, corrugated tubes, inner finned tubes and zigzag finned heat transfer tubes in strengthening condensation heat transfer and convective heat transfer, and avoids their shortcomings.

As shown in Figures 1 to 5, the present invention is provided with 16 to 45 evenly distributed, convex rectangular threads with the same height on the outer surface of the heat transfer tube, and at the same time, 1 to 5 parallel threads are arranged on the outer surface of the heat transfer tube. The above-mentioned concave spiral grooves with opposite directions of rotation and uniform distribution. The inner concave spiral groove cuts the outer convex rectangular thread into many helically distributed diamond-shaped ribs, and these diamond-shaped ribs constitute a special three-dimensional extended surface. Each rhombic rib is integrated with the outer wall of the heat transfer tube, and is disconnected from the four surrounding rhombic ribs at the bottom of the groove. The side of each rhombic rib is perpendicular to the tube wall or the tube axis. The higher the height of the diamond-shaped rib outside the tube, the larger the specific surface area, and the better the heat transfer enhancement outside the tube, but it also increases the resistance of the fluid outside the tube. Therefore, the height t of each rhombic fin can be taken as 1.2mm-4.5mm, the axial spacing δ2=0.5-3.5mm, and the fin thickness δ1=0.7-2.5mm.

The inner surface of the heat transfer tube is provided with a pair of left-handed and right-handed, single-headed or multi-headed right-handed spiral grooves and left-handed spiral grooves. Spiral groove inside the tube. The deeper the spiral groove in the tube, the smaller the lead (or pitch), the greater the enhanced convective heat transfer coefficient in the tube, but it also increases the pressure drop of the fluid in the tube. Therefore, the helix angle θ1 or θ1 of each spiral groove can be taken as 75°-85°, the lead (or pitch) F1 or F2=2-6mm, and the groove depth b=0.20mm-2.5mm.

The above-mentioned unique structure of the present invention has a strong vortex core, which is conducive to disturbing the gas-liquid two-phase flow state, reducing the thickness and thermal resistance of the stagnant bottom layer, and thus has a high heat transfer effect. Furthermore, the application of seamless tube integrated production technology ensures the integrity of the outer surface, inner surface and tube matrix structure, and eliminates quality problems such as increased thermal resistance caused by welds and defects such as shape dislocation. The invention is suitable for strengthening convective heat transfer of high-viscosity fluids, condensation of multi-component steam and water vapor containing non-condensable gases, convective heat transfer of non-phase change fluids, etc., and has high heat transfer coefficient, large specific heat transfer surface and The characteristics of anti-scaling and anti-scaling can be widely used in the heat exchange of various high-viscosity oil products in the fields of power energy, petrochemical industry, etc., and the condensation of water vapor and other heat exchangers, to replace smooth tubes or low-fin threaded tubes, Spiral grooved pipe, etc.

Principle of the present invention and effect are as follows:

The mechanism of the present invention to enhance convective heat transfer outside the tube is: the diamond-shaped ribs distributed in a helical shape outside the tube along the axial direction are three-dimensional discontinuous fins. Cut off the stagnant layer of fluid on the fins, so that the fluid flow direction is constantly changed and separated from the boundary layer, which strongly reduces the thickness of the stagnant layer. At the same time, when the fluid flows through the gaps between the rhombic ribs, strong disturbances can be generated, and the induced secondary flow (spiral flow and boundary layer separation flow) further thins the thickness of the fluid retention layer, which is beneficial to reducing thermal resistance and improving The heat transfer coefficient is very favorable. For the high Prandtl (Prandtl) number oil fluid whose heat transfer resistance is concentrated in the viscous bottom layer, the three-dimensional intermittent fins of this structure can enhance the heat transfer performance better.

On the other hand, when the fluid flows in the spiral flow channel, it makes a shearing motion with the rhomboid ribs, and the flow boundary layer and the heat transfer boundary layer are continuously separated due to the motion inertia of the fluid. After separation, the fluid will generate a vortex, and the impact of the fluid on the wall of the rhombic rib will strengthen the mass and momentum exchange and replacement between the fluid micro-clusters in the boundary layer of the wall and the fluid micro-clusters in the main flow area, and strengthen the convective heat transfer.

When the present invention is used for two-phase condensation heat exchange, the diamond-shaped ribs with a special three-dimensional extended surface structure can fully exert the surface tension of the condensate, causing the continuous phase near the wall to cause a superheated or supercooled state to promote phase transition, and the rhombus The condensed liquid droplets on the top of the ribs are pulled into the recesses, so that the film on the convex diamond-shaped ribs is quickly renewed, which helps to promote the continuous generation of condensate, and quickly flows from the top of the diamond-shaped ribs to the root of the gap between the two ribs , and quickly removed from the finned tube under the action of the screw force, this will enhance the disturbance in the liquid film, the effect is to increase the heat transfer coefficient of the condensation side outside the tube, reduce the thermal resistance of the condensate, and make the heat transfer process better strengthened.

The mechanism of the invention to enhance convective heat transfer in the tube is: the spiral groove on the inner wall of the tube causes a part of the fluid close to the wall to generate an additional spiral flow, which will increase the flow rate of the fluid, make the fluid rotate, reduce the thermal resistance, and improve heat transfer. At the same time, another part of the fluid near the wall is affected by the helical ribs produced by the intersecting spiral grooves, which generates a reverse pressure gradient on the rear side of the ribs, and causes a secondary separation flow, which promotes the flow of fluid in the radial direction. Mixing increases the degree of mixing between the mainstream fluid and the boundary layer fluid, thereby accelerating the heat transfer from the wall to the fluid body.

Since the present invention is provided with intersecting spiral grooves on the inner wall of the tube, the intersecting spiral grooves can make the fluid in the tube generate a helical flow and cause a secondary separation flow under low Re, so that the fluid presents a turbulent state and has a strong impact on the tube wall. Better flushing effect reduces the chance of medium deposition and fully prolongs the induction period of scaling. At the same time, the local curvature change of the intersecting spiral grooves in the axial direction can also force the formed scaling layer to crack and fall off again. The role of the flow, to achieve the effect of automatic descaling.

The implementation of the present invention can use the smooth pipe as a blank, adopt a special pipe rolling machine and carry out extrusion and little/no cutting processing, and process the inside and outside of the pipe step by step. Its processing method is as follows:

Put the copper, aluminum or steel smooth tube on a special rolling machine, insert it into a special mold arranged in an equilateral triangle, clamp the mold, and slowly pull out the steel tube along the axial direction. As the amount of extrusion increases, the metal along the Radial and axial flow, through radial and axial extrusion, the metal is plastically deformed to form a multi-headed convex rectangular thread. Then, another set of special tools is replaced, and the pipe is rotated in reverse. The special tool makes the metal plastically deformed to form a concave spiral groove. It cuts the metal convex rectangular thread formed in the previous step into left and right parts. The thicknesses of the two parts are respectively the axial width δ1 of the rhomboid fins and the axial distance δ2 of the rhomboid fins. The feed rate of the mold and the tool during the above two-step processing constitutes the height t of the rhombus fins. Through these two steps of processing, the helically distributed diamond-shaped ribs 1 on the outside of the tube can be formed. Finally, a special hobbing knife is inserted into the tube for less cutting and extrusion processing. The hobbing knife can form a left-handed spiral groove by extruding the material on the inner wall of the tube, and then rotate the pipe in the opposite direction to further squeeze the tube through the hobbing knife. The material of the inner wall can form right-handed helical grooves, and the intersection of left-handed helical grooves and right-handed helical grooves can form the surface of the intersecting helical grooves on the inner wall of the tube. Through the above several procedures, the steel smooth tube blank can be processed into the invention. Table 1 is a concrete example of the present invention:

Table 1

Tube outer diameter D(mm) Tube inner diameter d(mm) Outer tube geometric parameters Rib height t/mm Axial spacing of fins W1/mm Rhombus rib thickness W2/mm The pitch L1/mm of the convex rectangular thread The pitch L2/mm of the concave rectangular thread Outwardly convex rectangular thread helix angle β/ ⁰ Recessed rectangular thread helix angle α/ ⁰ 50 40 2.5 2 1.1 150 twenty three 71.56 114.7 Tube outer diameter D(mm) Tube inner diameter d(mm) Tube geometric parameters The left helix angle θ1/ ⁰ of the helical groove Right helix angle θ2/ ⁰ of the helical groove The lead (or pitch) of the left helical groove F1/mm The lead (or pitch) of the right spiral groove F2/mm The groove depth of the spiral groove b/mm 50 40 72.4 72.4 3.5 3.5 1.5

Example

Now take the transformation of the oil cooler in thermal power plant as an example to illustrate the effect of the present invention:

The heat transfer efficiency of the copper smooth tube oil cooler in a power plant is low, which makes it impossible to cool the oil temperature to a given value, causing related equipment to malfunction and affecting the normal operation of the power plant. The present invention is now manufactured with steel pipes, and the structural parameters are as the above-mentioned specific examples of the present invention to replace the original copper pipes in the oil cooler for copper-free transformation.

After modification, under the same working condition, the total heat transfer coefficient of the oil cooler of the invention is 28%-54% higher than that of the copper smooth tube oil cooler. This shows that although the thermal conductivity of the steel pipe is less than half of that of the copper pipe, the total heat transfer efficiency of the present invention is higher than that of the smooth copper pipe. This is because the three-dimensional diamond-shaped ribs on the outer surface of the heat transfer tube of the present invention are discontinuous and distributed in a spiral shape along the tube wall, which can reduce the thickness and thermal resistance of the stagnant bottom layer of the oil fluid, and the specific surface area is 3 times that of the copper smooth tube , for high-viscosity oil, this form of rough elements enhances heat transfer performance better than low-fin threaded tubes, spiral grooved tubes, etc.

Claims (10)

1. A double-sided reinforced heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs, comprising a heat transfer tube base, outer tube rhomboid ribs and tube inner spiral grooves, characterized in that: the heat transfer tube base, tube outer rhombus ribs It is an integrated structure with the spiral groove inside the tube. The diamond-shaped ribs outside the tube are interrupted from each other and are distributed in a spiral shape along the axial direction to form a three-dimensional extended surface of the entire outer surface of the tube wall. The spiral grooves inside the tube are intersected in the heat transfer tube matrix, and Appears in pairs in a left-right rotation. 2. The double-sided enhanced heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs according to claim 1, characterized in that: said outer rhomboid ribs are made of left-handed multi-headed convex rectangular thread and right-handed inner concave single-headed or Multi-start rectangular threads are formed by crossing each other, or formed by crossing right-handed multi-start convex rectangular threads and left-handed concave single-start or multi-start rectangular threads, and are perpendicular to the pipe axis or the outer wall of the pipe. 3. The double-sided enhanced heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs according to claim 2, characterized in that: the pitch of the outer convex rectangular thread is greater than the pitch of the inner concave rectangular thread, and the pitch of the outer convex rectangular thread 100-200mm, and the pitch of the concave rectangular thread is 20-50mm. 4. According to claim 2 or 3, the double-sided strengthened heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs is characterized in that: the helix angle of the outer convex rectangular thread is 60°-80°, and the inner concave rectangular thread helix angle is 60°-80°. The angle is 110°～150°. 5. The double-sided heat transfer tube with internal intersecting helical external three-dimensional rhombic ribs enhanced heat transfer according to claim 4, characterized in that: the width of the axial section of the rectangular thread is equal, and the shape and volume of the formed rhombus ribs are correspondingly equal. 6. The double-sided reinforced heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs according to claim 5, characterized in that: the axial spacing of the rhomboid ribs is 0.5-3.5 mm, and the thickness of the rhombic ribs is 0.7-2.5 mm. mm, and the height of the rhombus fins is 1.2mm to 4.5mm. 7. The double-sided enhanced heat transfer tube with inner cross helical outer three-dimensional rhombic ribs according to claim 6, characterized in that: the inner helical groove in the tube is composed of a left-handed inner concave single-headed or multi-headed helical groove and a right-handed inner The concave single-head or multi-head spiral grooves are formed by crossing each other, and the pitch of the left and right spiral grooves is 2-6mm, and the groove depth is 0.20mm-2.5mm. 8. The double-sided heat transfer tube with inner cross helical outer three-dimensional rhombic ribs enhanced heat transfer according to claim 7, characterized in that: the cross-sectional shape of the inner helical groove in the tube is trapezoidal, arc-shaped, triangular or rectangular. 9. The double-sided enhanced heat transfer tube with inner cross helical outer three-dimensional rhombic ribs according to claim 8, characterized in that: the left helix angle of the inner helical groove in the tube is 75°-85°, and the right helix The angle ranges from 75° to 85°. 10. The double-sided strengthened heat transfer tube with inner cross spiral outer three-dimensional rhombic ribs according to claim 1, characterized in that: the material of the heat transfer tube base, the outer rhomboid ribs and the inner helical grooves of the tube is copper or copper alloy , aluminum, aluminum alloy or carbon steel.

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