Evaporation heat exchange tubes and their manufacturing methods

Abstract

This application relates to an evaporative heat exchange tube and its manufacturing method. The evaporative heat exchange tube includes a circular tube body formed by bending and welding metal strips. Multiple channels are arranged sequentially at intervals along the axial direction of the tube body on its inner surface. Each of the multiple channels extends in a circumferential direction perpendicular to the axis of the tube body. The width of the channel opening is smaller than that of the channel bottom wall. The channel bottom wall has a raised portion protruding towards the channel opening. Each of the two channel sidewalls has an acute angle with the channel bottom wall. The channel bottom wall has a wider dimension in the axial direction than the channel opening, and the first and second channel sidewalls are arranged in a figure-eight shape. This application aims to improve the heat exchange effect of the evaporative heat exchange tube. This application specifically designs the micro-channels on the inner surface of the heat exchange tube. Through optimized design of the channel structure, its capillary force is enhanced, thereby improving the heat exchange effect of the evaporative heat exchange tube.

Description

Technical Field

[0001] This application relates to the field of heat exchange tubes, and in particular to an evaporative heat exchange tube and a method for manufacturing the same. Background Technology

[0002] There are two main types of evaporators: flooded evaporators and dry evaporators. In a flooded evaporator, the heat exchange tubes are completely submerged in liquid refrigerant, allowing the refrigerant to fully contact the tube walls. In a dry evaporator, the refrigerant's flow pattern restricts its contact with the tube walls, resulting in a heat exchange capacity that is only about half that of a flooded evaporator. Specifically, the dry evaporator operates as follows: a low-temperature working fluid, such as Freon, flows through the heat exchange tubes, simultaneously exchanging heat with the hot fluid outside the tubes, undergoing a phase change to form vapor. That is, the inlet is liquid, and the outlet is vapor. During this phase change, there are gas, liquid, and gas-liquid interfaces, with exchanges of mass, momentum, and energy between the two phases. Because the gas phase is compressible, the interfaces are easily deformable, resulting in different interface combinations during flow, i.e., flow pattern changes. For a horizontal dry evaporator with horizontally arranged heat exchange tubes, the flow patterns within the tubes include: bubbly flow, plug flow, laminar flow, wavy flow, blocky flow, and annular flow. Some of these flow patterns involve liquid at the bottom of the heat exchange tube and gas at the top under gravity, such as laminar flow, wavy flow, and plug flow. In this case, only a portion of the heat transfer area comes into contact with the liquid refrigerant and undergoes a phase change, while the other portion only comes into contact with the gas phase without a phase change. Currently, the enhanced heat exchange tubes used in dry evaporators are internally threaded tubes, meaning that multiple spiral channels are set on the inner wall of the heat exchange tube.

[0003] The technology disclosed in Chinese patent CN85103367A is as follows: many spiral grooves are provided on the inner surface of the heat exchange tube, and the shape of the cross section of the spiral ridge between each spiral groove is triangular or trapezoidal, so the cross section shape of the spiral groove is correspondingly triangular or trapezoidal.

[0004] The technology disclosed in Chinese patent CN2539948Y is as follows: multiple threaded teeth are formed on the inner surface. The cross-section of the tooth is triangular, and the threaded groove between adjacent threaded teeth is trapezoidal. Small cut-ridge grooves with regular spacing are opened along the tooth tip, hence it is called discontinuous tooth internal threaded tube.

[0005] The inventors of the above patents all emphasized that the spiral grooves on the inner surface act as disturbance elements, which can disturb the flow of fluid, disrupt the boundary layer of single-phase fluid, enhance convective heat transfer, and improve the heat transfer coefficient. However, there is still room for further optimization. Summary of the Invention

[0006] Through extensive experimentation and research, the inventors concluded that the microgrooves on the inner surface of the heat exchanger tube can also act as a liquid wick. According to fluid mechanics, these microgrooves generate capillary pressure, which overcomes gravity and transports the liquid from the bottom of the heat exchanger tube to above the liquid surface, wetting the area that was previously only in contact with the gas phase. This increases the contact area between the refrigerant and the heat exchange surface, thereby improving heat exchange efficiency. The size of the capillary pressure determines the amount of liquid transported, and its size is influenced not only by the properties of the liquid and the wall material but also by the geometry of the capillary channels. The maximum capillary pressure of the capillary channels is expressed by the following formula:

[0007]

[0008] in:

[0009] ΔPmax----Maximum capillary head;

[0010] σ --- Surface tension;

[0011] rc---Effect capillary radius.

[0012] The effective capillary radius in equation (1) is related to the geometry of the micro-capillary channels. Currently, the spiral channels in conventional heat exchange tubes are mostly trapezoidal in shape with a large opening and a small base, which has very limited capillary effect and greatly restricts the ability to transport liquid. At the same time, due to processing limitations, the channels in heat exchange tubes are currently spiral in shape. When the liquid is transported to a certain vertical height, the liquid flows a long distance along the channel, which affects the upward transport of the liquid and reduces the amount of liquid obtained on the upper wall of the tube. This leads to a more serious drying phenomenon on the upper wall of the heat exchange tube, which is not conducive to improving the heat exchange performance of the heat exchange tube.

[0013] Furthermore, the heat exchange process in dry evaporator tubes is a flow boiling process, the mechanism of which includes convective heat transfer and nucleation boiling. Improving nucleation boiling efficiency mainly involves three approaches: increasing the number of vaporization nuclei, enhancing heat transfer during bubble growth, and increasing the frequency of bubble detachment, i.e., reducing the size of the detached bubbles. Currently popular commercial internally threaded evaporator tubes have multiple trapezoidal or rectangular channels machined on their inner surface. The trapezoidal channel geometry is characterized by a large opening at the top and a small base. According to the boiling heat transfer theory, these geometries are not conducive to increasing the number of vaporization nuclei and activating nuclei, nor are they conducive to the bubble growth process under heat and the process of bubbles detaching from the heat transfer surface, i.e., the detachment process.

[0014] Based on the above analysis, this application proposes an evaporative heat exchange tube and its manufacturing method to improve the heat exchange effect of the evaporative heat exchange tube.

[0015] The technical solution of this application is:

[0016] An evaporative heat exchange tube includes a circular tube body formed by bending and welding a metal strip. The inner surface of the tube body is provided with a plurality of channels arranged sequentially at intervals in the axial direction of the tube body. Each of the plurality of channels extends in a circumferential direction perpendicular to the axis of the tube body.

[0017] Each of the plurality of channels includes:

[0018] The channel opening and the channel bottom wall are arranged opposite each other in the radial direction of the tube body, and

[0019] The first channel sidewall and the second channel sidewall are disposed opposite to each other in the axial direction;

[0020] The channel opening includes a first edge and a second edge disposed opposite to each other in the axial direction. The channel bottom wall includes a third edge and a fourth edge disposed opposite to each other in the axial direction, a first bottom wall surface extending from the third edge, and a second bottom wall surface extending from the fourth edge. The first bottom wall surface and the second bottom wall surface are disposed at an angle and form a raised portion bulging toward the channel opening. The first channel sidewall is directly connected between the first edge and the third edge, and the first channel sidewall and the first bottom wall surface have a first acute angle. The second channel sidewall is directly connected between the second edge and the fourth edge, and the second channel sidewall and the second bottom wall surface have a second acute angle. The first channel sidewall, the second channel sidewall, the first bottom wall surface, the second bottom wall surface, and the channel have the same length dimension in the circumferential direction. The channel bottom wall has a wider dimension in the axial direction than the channel opening, and the first channel sidewall and the second channel sidewall are disposed in a figure-eight shape.

[0021] In one optional design, any cross-section of the first channel sidewall along the axial direction, any cross-section of the second channel sidewall along the axial direction, any cross-section of the first bottom wall surface along the axial direction, and any cross-section of the second bottom wall surface along the axial direction are all straight lines.

[0022] In one alternative design, the first bottom wall surface is directly connected to the second bottom wall surface, thereby forming the angular protrusion.

[0023] In one optional design, the first bottom wall surface and the second bottom wall surface are symmetrically arranged on both sides of a plane, and the first channel sidewall and the second channel sidewall are also symmetrically arranged on both sides of the plane, wherein the plane is perpendicular to the axis of the pipe body.

[0024] In one alternative design, the included angle of the first acute angle is equal to that of the included angle of the second acute angle, both being 40°-60°.

[0025] In one optional design, the width of the channel opening in the axial direction is 0.15-0.35 mm, the width of the channel bottom wall in the axial direction is 0.5-1.2 mm, and the depth of the channel in the radial direction is 0.3-0.4 mm.

[0026] In one optional design, the plurality of channels are arranged sequentially at equal intervals in the axial direction, and the inner surface of the tube between any two adjacent channels is a smooth surface parallel to the axis of the tube. The interval between two adjacent channels is 1.3-1.5 times the width of the bottom wall of the channel in the axial direction.

[0027] In one alternative design, each of the plurality of channels is a closed annular channel.

[0028] Secondly, this application proposes a method for manufacturing an evaporative heat exchange tube as described in the first aspect, comprising:

[0029] A metal strip and a rolling roller are provided, wherein the rolling surface of the rolling roller is provided with outwardly protruding rolling ribs, the rolling ribs extend in a circumferential direction perpendicular to the axis of the rolling roller, and the top of the rolling ribs has a V-shaped groove corresponding to the raised portion.

[0030] The rolling roller is used to roll out a plurality of straight grooves arranged in parallel in a first direction on the surface of the metal strip, and a straight rib with a rectangular cross-section is formed between any two adjacent straight grooves.

[0031] The top of the straight rib is rolled over, causing the top of the straight rib to extend to both sides in the first direction;

[0032] The metal strip is bent so that its two opposite sides come into contact with each other to form a straight seam, and then welded at the straight seam to form a welded pipe.

[0033] In an alternative design, after the formation of the welded pipe, the following steps are also included:

[0034] The welded pipe is subjected to solution treatment in a protective atmosphere, wherein the protective atmosphere is a mixture of nitrogen with a mass concentration of 25% and hydrogen with a mass concentration of 75%, and the solution treatment temperature is 1020-1100℃.

[0035] This application has at least the following beneficial effects:

[0036] 1. This application specifically designs micro-channels on the inner surface of the heat exchange tube. Through optimized channel structure design, its capillary force is enhanced, improving the heat exchange effect of the evaporative heat exchange tube. Specifically, the bottom wall of the channel is provided with an outward bulge structure, forming two independent acute-angle corner channels extending along the length of the channel between the two side walls and the bottom wall, and reducing the width of the channel opening. When the heat exchange tube is horizontally arranged, the amount of liquid in the channel gradually decreases from bottom to top along the extension direction of the channel. When the liquid in the channel retracts from the channel opening into the acute-angle corner channel, the radius of curvature of the liquid surface in the channel decreases significantly, and the resulting capillary force increases significantly. The acute-angle corner channel produces a significant "pumping" effect, thereby increasing the amount of liquid wetting the upper dry wall surface inside the heat exchange tube, generating more steam, and helping to solve the problem of uneven liquid film distribution on the inner surface of the dry evaporative heat exchange tube, thus improving the evaporative heat exchange capacity of the heat exchange tube.

[0037] Furthermore, the amount of liquid in the acute-angle channel decreases from bottom to top along the extension direction of the acute-angle channel. Thanks to the triangular (cross-section) structure of the acute-angle channel, the radius of curvature of the liquid surface in the acute-angle channel decreases significantly in the extension direction of the channel, resulting in a larger capillary force. This can increase the amount of liquid wetting the upper dry wall surface inside the heat exchange tube and generate more steam.

[0038] 2. A key factor in enhancing the nucleation boiling process is increasing the number of vaporization nuclei, thereby increasing the number of bubbles and improving heat transfer efficiency. Based on heat transfer theory analysis and experimental observation, the inventors discovered that conical cavities, i.e., triangular depressions, easily generate vaporization nuclei or trap residual bubbles, and can reduce the energy required for bubble growth, thus increasing the activation level of bubble nuclei. Theory and experiments confirm that the included angle of the conical cavity should be acute to produce the above-mentioned effects, and the smaller the included angle, the better. This application provides an upwardly convex ridge at an angle on the bottom wall of the channel, and the included angle between the ridge and the side walls of the channel can be adjusted to be even smaller, which is beneficial to enhancing capillary force, generating vaporization nuclei, and promoting bubble growth.

[0039] 3. The channel adopts a dovetail shape with a small top opening and a large bottom edge, thus forming a cavity structure with a large space below. Simultaneously, the top opening of the dovetail-shaped channel forms a narrow slit, which serves as a passage connecting the cavity to the refrigerant outside the cavity, constituting the outlet for the bubbles within the cavity. Under the influence of wall superheat, a large amount of vapor can be generated in the cavity. At this point, the width of the narrow slit at the cavity outlet determines the size of the bubble's detachment diameter. A narrower slit results in a smaller bubble detachment diameter, and vice versa. In practice, the size of the narrow slit can be determined based on the surface tension of the refrigerant.

[0040] 4. The dovetail-shaped channel in this application facilitates heat exchange during bubble growth. Heat transfer theory demonstrates that after the formation of vaporization nuclei and small bubbles, a thin liquid film exists between the bubbles and the heating surface. Under heating conditions, this thin liquid film continuously evaporates, replenishing the bubbles with heat and mass, causing them to grow until they reach their detachment diameter and leave the wall. At this point, the thickness of the thin liquid film becomes the main factor affecting thermal resistance. In the dovetail-shaped channel structure of this application, because the outlet of the cavity is a narrow slit, the bubbles generated in the cavity cannot immediately leave. Therefore, after being heated, the bubbles expand within the cavity, thinning the liquid film between the bubbles and the heating surface, thus reducing the thermal resistance of the heating surface to heat transfer from the bubbles. Under normal boiling conditions, bubbles on the heating surface can only contact one side of the heating surface. However, in this application, the bubbles in the cavity are heated and expand under the constraint of the narrow outlet slit. During expansion, they come into contact with other walls of the cavity, thereby increasing the heated area of ​​the bubbles and thinning the liquid film between the bubbles and the heating surface, reducing thermal resistance and thus improving heat transfer efficiency. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this application, and are not intended to limit this application.

[0042] Figure 1 This is a schematic diagram of the structure of the evaporator heat exchange tube after partial unfolding in an embodiment of this application.

[0043] Figure 2 yes Figure 1 Schematic diagram of the sectional view along the AA direction.

[0044] Figure 3 yes Figure 2 Enlarged schematic diagram of part B.

[0045] Figure 4 This is a partial structural schematic diagram of the rolling roller in an embodiment of this application.

[0046] Figure 5 This is a schematic diagram of the structure of the metal strip after step S102 in the embodiments of this application.

[0047] Figure 6 This is a graph showing the relationship between the included angle of the triangular trench and the height to which the water is lifted in the trench. The horizontal axis represents the included angle of the triangular trench, and the vertical axis represents the height to which the water is lifted in the trench under vertical conditions.

[0048] Figure 7 This is a comparison diagram of the heat transfer performance of the evaporative heat exchange tube and the smooth tube heat exchange tube in the embodiments of this application. In the figure, the horizontal axis represents the mass flow rate, the vertical axis represents the boiling heat transfer coefficient, the circular black dots represent the heat exchange tubes in this embodiment, and the square black dots represent the smooth tube heat exchange tubes.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1-tube body;

[0051] 1a - Weld;

[0052] 101-Channel;

[0053] 1011-Channel opening, 1012-Channel bottom wall, 1013-First channel side wall, 1014-Second channel side wall;

[0054] 1011a - First edge, 1011b - Second edge, 1012a - Third edge, 1012b - Fourth edge;

[0055] 10121 - First bottom wall surface, 10122 - Second bottom wall surface;

[0056] β1 = the included angle of the first acute angle, β2 - the included angle of the second acute angle;

[0057] P-plane;

[0058] 2-Rolling roller;

[0059] 201-Rolled Ribs;

[0060] 201a-V-shaped groove;

[0061] 3-Metal strip;

[0062] 301 - Straight groove;

[0063] 301a-V-shaped protrusion;

[0064] 302 - Straight-line reinforcing bars. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It is understood that, without conflict, some technical means of the various embodiments described herein can be substituted for or combined with each other.

[0066] In the description of this application and the claims, the terms "first," "second," etc., are used only to distinguish the described objects and have no sequential or technical meaning. Therefore, objects specified with "first," "second," etc., may explicitly or implicitly include one or more of those objects. Furthermore, the words "one" or "a" do not indicate a quantity limitation, but rather indicate the presence of at least one, while "multiple" indicates not less than two.

[0067] In the description of this application and the claims, the terms "connection," "installation," and "fixation," unless otherwise specified, should be interpreted broadly. For example, "connection" can mean a separate connection or an integral connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean a non-detachable connection or a detachable connection. Those skilled in the art can understand the specific meaning of the aforementioned terms in this application according to the specific circumstances.

[0068] In the description of this application and the claims, if terms such as "above," "below," or "horizontal" indicate orientation or positional relationships based on the orientation or positional relationships shown in the drawings, they are only for the purpose of clearly and simply describing this application, and do not indicate or imply that the elements referred to must have a specific orientation or be constructed and operated in a specific orientation. These directional terms are relative concepts used for relative description and clarification, and may change accordingly depending on the orientation of the components in the drawings. For example, if the device in the drawings is flipped, an element described as "below" other elements will be positioned "above" other elements.

[0069] In the description of this application specification and claims, the term "configured as" is generally interchangeable with "having the ability to," "designed to," "used for," or "capable of," depending on the context.

[0070] Embodiments of this application will now be described with reference to the accompanying drawings.

[0071] Figures 1 to 3 In a specific embodiment of the evaporative heat exchange tube of this application, the evaporative heat exchange tube is a welded tube, which includes a circular tube body 1 formed by bending and welding a metal strip 3. A plurality of channels 101 are formed on the inner surface of the tube body 1 in a sequentially spaced manner in the axial direction of the tube body 1, and each channel 101 extends in a circumferential direction perpendicular to the axis of the tube body 1.

[0072] Each of the aforementioned channels 101 includes: a channel opening 1011 and a channel bottom wall 1012 arranged opposite each other in the radial direction of the pipe body 1, and a first channel side wall 1013 and a second channel side wall 1014 arranged opposite each other in the axial direction of the pipe body 1. Wherein:

[0073] The channel opening 1011 includes a first edge 1011a and a second edge 1011b disposed opposite to each other in the axial direction of the pipe body 1. The channel bottom wall 1012 includes a third edge 1012a and a fourth edge 1012b disposed opposite to each other in the axial direction of the pipe body 1, a first bottom wall surface 10121 extending from the third edge 1012a, and a second bottom wall surface 10122 extending from the fourth edge 1012b. The first bottom wall surface 10121 and the second bottom wall surface 10122 are disposed at an angle to each other, thereby forming a raised portion that bulges toward the channel opening 1011. The first bottom wall surface 10121, the second bottom wall surface 10122 and the channel 101 have the same length dimension in the circumferential direction. The first channel sidewall 1013 is directly connected between the first edge 1011a and the third edge 1012a, and the first channel sidewall 1013 and the first bottom wall surface 10121 have a first acute angle β1. The second channel sidewall 1014 is directly connected between the second edge 1011b and the fourth edge 1012b, and there is a second acute angle β2 between the second channel sidewall 1014 and the second bottom wall surface 10122. The channel 101 has a dovetail structure, and its channel bottom wall 1012 has a larger width dimension in the axial direction of the tube than the channel opening 1011.

[0074] As expressed in equation (1) in the invention content section of this application: the maximum capillary pressure head of the capillary channel and the effective capillary radius r c Related. Different channels have different effective capillary radii. The effective capillary radii of rectangular channels, triangular channels, and semi-circular channels are shown in Table 1 below:

[0075] Table 1: Different capillary channels and effective capillary radius r c

[0076]

[0077] In this embodiment, the approximately dovetail-shaped channel has two acute angles formed by its two sides (the first and second channel sidewalls) and its bottom edge (the bottom wall of the channel). Specifically, the sharp-angled regions formed by the first acute angle β1 between the first channel sidewall 1013 and the channel bottom wall 1012, especially the first bottom wall surface 10121 of the channel bottom wall 1012, and the second acute angle β2 between the second channel sidewall 1014 and the channel bottom wall 1012, especially the second bottom wall surface 10122 of the channel bottom wall 1012, can serve as channels for liquid flow and are triangular channels. When the heat exchange tubes are arranged horizontally, above the liquid level inside the heat exchange tubes, as the channel 101 extends upwards, the liquid in the channel 101 gradually decreases. When the liquid recedes into the sharp-angled region, the sharp-angled region can serve as a liquid flow channel and can be considered as a triangular channel. As shown in Table 1 above, when the apex angle of the triangle (corresponding to β1 and β2) is a small acute angle, the corresponding cosβ is close to 1, resulting in a large capillary force. This allows for more liquid to wet the upper dry wall surface inside the heat exchange tube, generating more steam. Furthermore, the opening width of the triangular channel is smaller than that of the rectangular channel opening. Therefore, it can be determined that the capillary head of this channel 101 in this embodiment is significantly greater than that of the rectangular channel.

[0078] When the heat exchange tubes are arranged horizontally, compared with the traditional rectangular channel, in this embodiment, the amount of liquid in the channel 101 decreases from bottom to top along the extension direction of the channel 101. When the liquid in the channel retracts into the sharp corner area, the radius of curvature of the liquid surface in the channel 101 is significantly reduced, resulting in a large capillary force. This can lift more liquid to wet the upper dry wall surface inside the heat exchange tube, generating more steam.

[0079] Figure 6 The horizontal axis represents the included angle of the triangular trench, and the vertical axis represents the height to which the water is lifted in the trench under vertical conditions. The experimental results show that the smaller the included angle, the higher the water is lifted in the trench, proving that the smaller the included angle, the greater the capillary force in the trench. Therefore, in this embodiment, the first bottom wall surface 10121 and the second bottom wall surface 10122 of the channel bottom wall 1012 are arranged at an included angle that bulges towards the channel opening 1011, thereby making the first acute angle β1 or the second acute angle β2 smaller, resulting in a greater capillary force.

[0080] The channel adopts a dovetail shape with a small top opening and a large bottom edge, thus forming a cavity structure with a large space below. Simultaneously, the top opening of the dovetail-shaped channel forms a narrow slit, which serves as a passage connecting the cavity to the refrigerant outside the cavity, constituting the outlet for the bubbles within the cavity. Under the influence of wall superheat, a large amount of vapor can be generated in the cavity. At this point, the width of the narrow slit at the cavity outlet determines the size of the bubble's detachment diameter. A narrower slit results in a smaller bubble detachment diameter, and vice versa. In practice, the size of the narrow slit can be determined based on the surface tension of the refrigerant.

[0081] Furthermore, the dovetail-shaped channel facilitates heat exchange during bubble growth. Heat transfer theory demonstrates that after the formation of vaporization nuclei and small bubbles, a thin liquid film exists between the bubbles and the heating surface. Under heating conditions, this thin liquid film continuously evaporates, replenishing the bubbles with heat and mass, causing them to grow until they reach their detachment diameter and leave the wall. At this point, the thickness of the thin liquid film becomes the main factor affecting thermal resistance. In the dovetail-shaped channel structure of this application, because the outlet of the cavity is a narrow slit, the bubbles generated in the cavity cannot immediately leave. Therefore, after being heated, the bubbles expand within the cavity, thinning the liquid film between the bubbles and the heating surface, thus reducing the thermal resistance of the heating surface to heat transfer from the bubbles. Under normal boiling conditions, bubbles on the heating surface can only contact one side of the heating surface. However, in this application, the bubbles in the cavity are heated and expand under the constraint of the narrow outlet slit. During expansion, they come into contact with other walls of the cavity, thereby increasing the heated area of ​​the bubbles and thinning the liquid film between the bubbles and the heating surface, reducing thermal resistance and thus improving heat transfer efficiency.

[0082] In this embodiment, any cross-section of the first channel sidewall 1013 along the axial direction of the pipe body 1, any cross-section of the second channel sidewall 1014 along the axial direction of the pipe body 1, any cross-section of the first bottom wall surface 10121 along the axial direction of the pipe body 1, and any cross-section of the second bottom wall surface 10122 along the axial direction of the pipe body 1 are all straight lines.

[0083] In this embodiment, the first bottom wall surface 10121 and the second bottom wall surface 10122 are directly connected, thereby forming the aforementioned raised portion with a pointed angle. The direct connection between the first bottom wall surface 10121 and the second bottom wall surface 10122 increases the depth of the triangular channel, which in turn helps to wet more liquid on the upper dry wall surface inside the heat exchange tube, generating more steam.

[0084] In this embodiment, the first bottom wall surface 10121 and the second bottom wall surface 10122 have the same area size and are symmetrically arranged on both sides of a plane P perpendicular to the axis of the tube body 1. The first channel sidewall 1013 and the second channel sidewall 1014 also have the same area size and are also symmetrically arranged on both sides of the aforementioned plane P.

[0085] The first acute angle β1 and the second acute angle β2 are equal, and both are preferably 40°-60°. This setting of the degrees of the first acute angle β1 and the second acute angle β2 facilitates the fabrication of the channel 101 structure and also achieves a better anti-drying effect. Specifically, in this embodiment, the first acute angle β1 and the second acute angle β2 are both 40°.

[0086] The dimensions of the channel 101 should not be too large or too small. Generally, the width of the channel opening 1011 in the axial direction of the pipe body 1 is preferably 0.15-0.35 mm, and in this embodiment, it is specifically 0.8 mm. The width of the channel bottom wall 1012 in the axial direction of the pipe body 1 is 0.5-1.2 mm, and in this embodiment, it is specifically 1.0 mm. The depth of the channel 101 in the radial direction of the pipe body 1 is preferably 0.3-0.4 mm, and in this embodiment, it is specifically 0.3 mm.

[0087] In this embodiment, the aforementioned channels 101 are arranged sequentially at equal intervals along the axial direction of the tube body 1, and the inner surface of the tube body 1 between any two adjacent channels 101 is a smooth surface parallel to the axis of the tube body 1. The spacing between two adjacent channels 101 is preferably 1.3-1.5 times the width of the channel bottom wall 1012 in the axial direction.

[0088] In order to ensure that the heat exchange tube can achieve a good anti-drying effect when it is horizontally or approximately horizontally arranged at any angle (the angle of pivoting around the tube axis), each channel 101 in this embodiment is designed as a closed annular channel, obviously surrounding the axis of the tube body 1.

[0089] In this embodiment, the outer diameter of tube 1 is 9.52 mm. To verify the heat exchange performance of this heat exchange tube, we conducted a comparative experiment on the heat exchange performance of the heat exchange tube in this embodiment and a smooth tube heat exchange tube. The smooth tube heat exchange tube has a smooth inner surface without grooves, and its material and dimensions are the same as those of the heat exchange tube in this embodiment. The refrigerant used in the experiment was R410A, with an inlet dryness fraction x = 0.2 and an outlet dryness fraction x = 0.45. The experimental results are as follows: Figure 7 As shown in the figure, the horizontal axis represents the mass flow rate of R410A, and the vertical axis represents the evaporation heat transfer coefficient inside the tube. The circular black dots in the figure represent the heat exchange tubes in this embodiment, and the square black dots represent the smooth tube heat exchange tubes. Figure 7 The experimental results show that the evaporative heat transfer coefficient of the heat exchange tube in this embodiment is 2.1 times that of the bare tube.

[0090] Furthermore, this embodiment also proposes a method for manufacturing the evaporative heat exchanger tube, which includes the following steps:

[0091] S101, a metal strip 3 and a rolling roller 2 are provided, wherein the rolling surface of the rolling roller 2 is provided with an outwardly protruding rolling rib 201, the rolling rib 201 extends in a circumferential direction perpendicular to the axis of the rolling roller 2, and the top of the rolling rib 201 has a V-shaped groove 201a corresponding to the pointed ridge.

[0092] To improve product quality, chemical agents can be used to clean the metal strip 3. After the cleaned metal strip 3 is dried, the edges of the metal strip 3 are straightened to make the width and thickness of the metal strip 3 uniform.

[0093] The material of metal strip 3 can be various grades of titanium steel, stainless steel, carbon steel, aluminum or copper.

[0094] S102, a plurality of straight grooves 301 arranged in parallel in the first direction are rolled out on the surface of the metal strip 3 by the rolling roller 2, and a straight rib 302 with a rectangular cross section is formed between any two adjacent straight grooves 301.

[0095] It is understandable that, since the top of the rolled rib 201 has a V-shaped groove 201a corresponding to the pointed ridge, after this step is completed, the bottom of the formed straight groove 301 has a straight-extending V-shaped protrusion 301a, which corresponds to the aforementioned ridge.

[0096] To facilitate subsequent welding, a smooth, narrow edge of 0.5-3mm can be left at both ends of the straight groove from the edge of the metal strip.

[0097] S103, then roll over the top of the straight rib 302, so that the top of the straight rib 302 extends outward in the aforementioned first direction.

[0098] It is understandable that when the top of the straight rib 302 is subjected to mechanical rolling pressure in the height direction, it will produce deformation extending to both sides of the width. This deformation causes the straight rib 302 to be roughly an inverted isosceles trapezoid, with the two legs of the isosceles trapezoid corresponding to the first channel sidewall 1013 and the second channel sidewall 1014 mentioned above, respectively.

[0099] S104, bend the metal strip 3 so that the two opposite sides of the metal strip 3 come into contact with each other to form a straight seam, and weld the straight seam using argon arc welding process to form a welded pipe.

[0100] After completing step S104, an online eddy current flaw detector can be used to inspect the weld seam of the welded pipe to ensure a tight weld. After confirming that the weld seam quality meets the standards, the welded pipe is subjected to solution treatment in a protective atmosphere to improve the quality of the welded pipe. The aforementioned protective atmosphere can be a mixture of 25% nitrogen and 75% hydrogen by mass, and the preferred temperature for the solution treatment is 1020-1100℃.

[0101] The above are merely exemplary embodiments of this application and are not intended to limit the scope of protection of this application, which is determined by the appended claims.

Claims

1. An evaporative heat exchange tube comprising a circular tube body (1) formed by bending and welding a metal strip (3), characterized in that, The inner surface of the tube (1) is provided with a plurality of channels (101) arranged sequentially at intervals in the axial direction of the tube (1). Each of the plurality of channels (101) extends in a circumferential direction perpendicular to the axis of the tube (1). Each of the plurality of channels (101) is a closed annular channel. Each of the plurality of channels (101) includes: The channel opening (1011) and the channel bottom wall (1012) are arranged opposite each other in the radial direction of the tube body (1), and A first channel sidewall (1013) and a second channel sidewall (1014) are disposed opposite to each other in the axial direction. The channel opening (1011) includes a first edge (1011a) and a second edge (1011b) disposed opposite to each other in the axial direction. The channel bottom wall (1012) includes: a third edge (1012a) and a fourth edge (1012b) disposed opposite to each other in the axial direction, a first bottom wall surface (10121) extending from the third edge (1012a), and a second bottom wall surface (10122) extending from the fourth edge (1012b). The first bottom wall surface (10121) and the second bottom wall surface (10122) are disposed at an angle and form a raised portion protruding toward the channel opening (1011). The first channel sidewall (1013) is directly connected between the first edge (1011a) and the third edge (1012a), and the first channel sidewall (1013) is connected to the... The first bottom wall surface (10121) has a first acute angle (β1) between it and the second channel sidewall (1014). The second channel sidewall (1014) is directly connected between the second edge (1011b) and the fourth edge (1012b). The second channel sidewall (1014) and the second bottom wall surface (10122) have a second acute angle (β2). The first channel sidewall (1013), the second channel sidewall (1014), the first bottom wall surface (10121), the second bottom wall surface (10122) and the channel (101) have the same length dimension in the circumferential direction. The channel bottom wall (1012) has a wider dimension in the axial direction than the channel opening (1011). The first channel sidewall (1013) and the second channel sidewall (1014) are arranged in a figure-eight shape.

2. The evaporative heat exchange tube of claim 1, wherein Any cross section of the first channel sidewall (1013) along the axial direction, any cross section of the second channel sidewall (1014) along the axial direction, any cross section of the first bottom wall surface (10121) along the axial direction, and any cross section of the second bottom wall surface (10122) along the axial direction are all straight lines.

3. The evaporative heat exchange tube of claim 2, wherein The first bottom wall surface (10121) is directly connected to the second bottom wall surface (10122), thereby forming the raised portion with a pointed shape.

4. The evaporative heat exchange tube of claim 3, wherein The first bottom wall surface (10121) and the second bottom wall surface (10122) are symmetrically arranged on both sides of a plane (P), and the first channel sidewall (1013) and the second channel sidewall (1014) are also symmetrically arranged on both sides of the plane (P), wherein the plane (P) is perpendicular to the axis of the pipe body (1).

5. The evaporative heat exchange tube of claim 4, wherein The first acute angle (β1) and the second acute angle (β2) are equal, both being 40°-60°.

6. The evaporative heat exchange tube of claim 1, wherein The width of the channel opening (1011) in the axial direction is 0.15-0.35mm, the width of the channel bottom wall (1012) in the axial direction is 0.5-1.2mm, and the depth of the channel (101) in the radial direction is 0.3-0.4mm.

7. The evaporative heat exchange tube of claim 1, wherein The plurality of channels (101) are arranged at equal intervals in sequence in the axial direction, and the inner surface of the tube (1) between any two adjacent channels (101) is a smooth surface parallel to the axis of the tube (1). The interval between two adjacent channels (101) is 1.3-1.5 times the width dimension of the bottom wall (1012) of the channel in the axial direction.

8. A method of manufacturing an evaporative heat exchange tube as claimed in any one of claims 1 to 7, characterized in that, include: A metal strip (3) and a rolling wheel (2) are provided, wherein the rolling surface of the rolling wheel (2) is provided with an outwardly protruding rolling rib (201), the rolling rib (201) extends in a circumferential direction perpendicular to the axis of the rolling wheel (2), and the top of the rolling rib (201) has a V-shaped groove (201a) corresponding to the protrusion. The rolling roller (2) is used to roll out a plurality of straight grooves (301) arranged in parallel in the first direction (F1) on the surface of the metal strip (3), and a straight rib (302) with a rectangular cross section is formed between any two adjacent straight grooves (301). The top of the straight rib (302) is rolled over so that the top of the straight rib (302) extends to both sides in the first direction (F1); The metal strip (3) is bent so that the two opposite sides of the metal strip (3) come into contact with each other to form a straight seam, and the straight seam is welded to form a welded pipe.

9. The production method according to claim 8, wherein After the formation of the welded pipe, the process further includes: The welded pipe is subjected to solution treatment in a protective atmosphere, wherein the protective atmosphere is a mixture of nitrogen with a mass concentration of 25% and hydrogen with a mass concentration of 75%, and the solution treatment temperature is 1020-1100℃.

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