HK1083530B - Heat transfer tube and method of and tool for manufacturing the same - Google Patents

Description

Heat transfer tube and method and tool for manufacturing the same

Technical Field

The present invention relates to a heat transfer pipe having projections on the inner surface of the pipe, and a method and a tool for forming the projections on the inner surface of the pipe.

Background

The present invention relates to a heat transfer tube having an enhanced inner surface to facilitate heat transfer from one side of the tube to the other. Heat transfer tubes are commonly used in certain equipment such as flooded evaporators, falling film evaporators, spray evaporators, absorption chillers, condensers, direct expansion chillers and single phase chillers, and heaters used in the refrigeration, chemical, petrochemical and food processing industries. A variety of heat transfer media are used in these applications including, but not limited to, pure water, water glycol mixtures, refrigerants of any type (e.g., R-22, R-134a, R-123, etc.), ammonia, petrochemical liquids, and other mixtures.

An ideal heat transfer tube allows heat to be transferred from the inside of the tube to the outside of the tube and vice versa completely uninhibited. However, this free transfer of heat through the tubes is generally impeded by thermal resistance to heat transfer. The total thermal resistance of the tube to heat transfer is calculated by adding the individual thermal resistances from the outside of the tube to the inside of the tube, or vice versa. To improve the heat exchange efficiency of the tubes, tube manufacturers are constantly striving to find ways to reduce the overall thermal resistance of the tubes. One approach is to reinforce the outer surface of the tube, for example by forming fins on the outer surface. As a result of new research into enhancing the surface of external tubes (see, e.g., U.S. patent nos. 5697430 and 5996686), only a small portion of the total tube thermal resistance is external to the tube. For example, a typical evaporator used in a flooded freezer has an enhanced outer surface and a smooth inner surface, typically having a 10: 1 ratio of inner to outer thermal resistances. Ideally, a 1: 1 ratio of internal to external resistivities is desired. It becomes more important to modify the inner surface of the tube to greatly reduce the internal thermal resistance of the tube and to improve the overall heat transfer performance of the tube.

It is known to provide alternating grooves and ridges on the inner surface of the heat transfer tube. The grooves and ridges together increase the turbulence of the fluid heat transfer medium, such as water, flowing within the tube. The turbulence increases fluid mixing near the inner tube surface, thereby reducing or virtually eliminating boundary layer build-up of the fluid medium near the inner surface of the tube. This boundary layer thermal resistance significantly degrades heat transfer performance due to the increased heat exchange resistance of the tubes. The grooves and ridges also provide additional area for additional heat exchange. This basic premise is described in U.S. Pat. No.3847212 to Wither, Jr et al.

The pattern, profile and dimensions of the grooves and ridges on the inner surface of the tube may be varied to further enhance heat transfer performance. To this end, pipe manufacturers have invested substantial amounts of capital to test for alternative designs, including those disclosed in U.S. patent No.5791405 to Takima et al, U.S. patent nos. 5332034 and 5458191 to Chiang et al, and U.S. patent No.5975196 to Gaffaney et al.

However, in general, it has proven much more difficult to reinforce the inner surface of a pipe than the outer surface. And most of the reinforcement on the inner and outer surfaces of the tube is formed by casting and surface forming. However, it is already possible to create this reinforcing effect by cutting the surface of the tube.

Japanese patent application 09108759 discloses a tool for centering a blade which cuts a continuous helical groove directly in the inner surface of a tube. Similarly, japanese patent application 10281676 discloses a tube expander plug provided with a cutting tool that cuts a continuous helical groove and upstanding fins on the inner surface of the tube. U.S. patent No.3753364 discloses forming a continuous groove along the inner surface of a tube with a cutting tool that cuts into the inner surface of the tube and bends the material upward to form a continuous groove.

While all of these tube inner surface designs are intended to improve the heat transfer performance of the tube, there remains a need in the industry to continue to improve the tube design by modifying existing designs that enhance heat transfer performance and developing new designs. In addition, there is a need to develop structures and patterns that can be more quickly and inexpensively transferred to the tube. As described below, applicants have developed geometries for heat transfer tubes, and tools for forming such geometries, and, as a result, have significantly improved heat transfer performance.

Disclosure of Invention

The present invention provides an improved heat transfer tube surface and method of forming the same that can be used to enhance the heat transfer performance of tubes used in at least all of the above-described applications (i.e., flooded evaporators, falling film evaporators, spray evaporators, absorption chillers, condensers, direct expansion chillers, and single phase chillers and heaters used in the refrigeration, chemical, petrochemical, and food processing industries). The inner surface of the tube is reinforced by a plurality of protrusions that significantly reduce the tube side thermal resistance and improve the overall heat transfer performance. The protrusions provide additional paths for the fluid flow within the tubes, thereby increasing the turbulence of the heat transfer medium flowing within the tubes. This increases the fluid mixing in order to reduce the boundary layer build-up of the fluid medium close to the inner surface of the tube, which build-up increases the thermal resistance and thus inhibits heat transfer. The protrusions also provide additional surface area for additional heat exchange. Protrusions formed in accordance with the present invention can form up to five times the surface area along the inner surface of the tube as compared to simple ridges. Tests have shown that the performance of the tube with the inventive bulges is significantly improved.

The method of the present invention includes the use of a tool that can be easily installed on existing manufacturing equipment, the tool having a cutting edge to sever the ridges on the inner surface of the tube to form a ridge layer, and a lifting edge to lift the ridge layer to form the projections. In this way, the formation of the projections does not remove metal from the inner surface of the tube, thus eliminating swarf in the tube that could damage the equipment. The protrusions on the inner surface of the tube may be formed in the same or a different operation as the ridges are formed.

Pipes formed in accordance with the present application are suitable for use in a number of devices, including, for example, devices used in the HVAC (heating, ventilation and air conditioning), refrigeration, chemical, petrochemical and food processing industries. The physical geometry of the projections can be varied to adapt the tube to the particular device and fluid medium.

It is an object of the present invention to provide an improved heat transfer tube.

It is another object of the present invention to provide an improved heat transfer tube having projections on its inner surface.

It is another object of the present invention to provide a method of forming an improved heat transfer tube having projections on an inner surface.

It is another object of the present invention to provide a new tool for forming an improved heat transfer tube.

It is another object of the present invention to provide a tool for forming projections on the inner surface of the heat transfer tube.

These and other features, objects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments when read in conjunction with the accompanying drawings.

Drawings

FIG. 1a is a partial perspective view of a partially formed inner surface of one embodiment of a tube of the present invention.

Fig. 1b is a side view in the direction of arrow a in fig. 1 a.

FIG. 1c is a side view similar to FIG. 1b, except that the protrusions protrude from the inner surface of the tube in a direction that is not perpendicular to the axis S.

FIG. 1d is a front view of the tube in the direction of arrow b in FIG. 1 a.

FIG. 1e is a top view of the tube shown in FIG. 1 a.

FIG. 2 is a microscopic view of the inner surface of one embodiment of the tube of the present invention.

Figure 3 is a microscopic view of the inner surface of an alternative embodiment of the tube of the present invention.

FIG. 4 is a side view of one embodiment of a manufacturing apparatus that can be used to manufacture tubes according to the present invention.

Fig. 5 is a perspective view of the apparatus of fig. 4.

Fig. 6a is a perspective view of one embodiment of a tool of the present invention.

Fig. 6b is a side view of the tool shown in fig. 6 a.

Fig. 6c is a bottom view of the tool of fig. 6 b.

Fig. 6d is a top view of the tool of fig. 6 b.

Fig. 7a is a perspective view of an alternative embodiment of a tool of the present invention.

Fig. 7b is a side view of the tool shown in fig. 7 a.

Fig. 7c is a bottom view of the tool of fig. 7 b.

Fig. 7d is a top view of the tool of fig. 7 b.

Fig. 8a is a partial perspective view of a partially formed inner surface of an alternative embodiment of a tube of the present invention wherein the depth of the transverse ridges is less than the height of the helical ridges.

Figure 8b is a partial perspective view of a partially formed inner surface of an alternative embodiment of the tube of the present invention wherein the depth of the transverse ridges is greater than the height of the helical ridges.

Figure 9a is a partial top view of the inner surface of another embodiment of a tube according to the present invention.

Fig. 9b is a front view of the tube shown in fig. 9a in the direction of arrow 22.

Fig. 10a is a partial view of the inner surface of the tube of the present invention showing a tool in the g-direction adjacent to the ridge to cut a protrusion from the ridge in the g-direction.

Fig. 10b is a partial view of an alternative inner surface of the tube of the present invention showing a tool in the g-direction adjacent to the ridge to cut a protrusion from the ridge in the g-direction.

Fig. 11a is a schematic view of the inner surface of a tube according to the present invention showing the angular orientation between ridges and grooves, wherein the ridges and grooves are oppositely spiraled.

Fig. 11b is a schematic view of the inner surface of a tube according to the present invention showing the angular orientation between the ridges and grooves, wherein the ridges and grooves are co-directionally helical.

Detailed Description

Fig. 1a-e show a partially formed inner surface 18 of one embodiment of a tube 21 of the present invention. The inner surface 18 comprises a plurality of protrusions 2. The protrusion 2 is formed by a ridge 1 formed on the inner surface 18. The ridge 1 is first formed on the inner surface 18. The ridges 1 are then cut to produce a ridge layer 4, and the ridge layer 4 is then lifted to form the protrusions 2 (as best shown in fig. 1a and 1 b). The cutting and lifting may be accomplished with a tool 13, as shown in fig. 6a-d and 7a-d and described below, but this is not essential.

It should be understood that the tube according to the invention may be used in any device where it is desired to transfer heat from one side of the tube to the other side of the tube, such as, but not limited to, single-phase and multi-phase (both pure liquid or gas or liquid/gas mixture) evaporators and condensers. While the following description provides the tubes of the present invention with desirable dimensions, the tubes of the present invention are in no way limited to these dimensions. The ideal geometry of the tube and of the projections 2 depends on a number of factors, of which the properties of the fluid flowing through the tube are of no importance. Those skilled in the art will know how to modify the geometry of the inner surface of the tube and the geometry of the ridges 1 and projections 2 in order to maximize heat transfer in various devices and tubes used with various fluids.

The ridges 1 are formed on the inner surface 18 at a helix angle α relative to the axis S of the tube (see fig. 1a and 1 e).The helix angle alpha may be any angle between 0 deg. -90 deg., but preferably does not exceed 70 deg.. Those skilled in the art will readily appreciate that the helix angle α will often depend, at least in part, on the fluid medium used. Height e of ridge 1_rThe larger, the more viscous the fluid will generally be for flow through the tube 21. E.g., greater than zero (preferably, but not necessarily, at least 0.001 inch) to the tube inside diameter (D)_i) Height e of 25%_rIt is generally desirable to use it in the tubes of equipment that lowers the temperature with a water/glycol mixture. For this application, D_iIs the inner diameter of the tube 21 as measured from the inner surface 18 of the tube 21. Axial pitch P of ridges 1_a，rDepending on a number of factors, including the helix angle α, the number of ridges formed on the inner surface 18 of the tube 21, and the inner diameter D of the tube 21_i. Although any pitch P may be used_a，rPreferably P_a，r/e_rIs at least 0.002, e_r/D_iPreferably between about 0.001 and 0.25. Again, however, those skilled in the art will readily appreciate that these preferred ratios will often depend, at least in part, on the fluid medium used and the operating conditions (i.e., the temperature of the fluid medium).

The spine layer 4 is cut at an angle θ relative to the axis s, which is preferably between about 20-50, including and more preferably about 30. Axial pitch P of the projections 2_a，pMay be any value greater than zero and generally depends on, among other factors, the number of relative rotations per minute between the tool (described below) and the tube during manufacture, the relative axial feed rate between the tool and the tube during manufacture, and the number of tips provided on the tool forming the projections during manufacture. Although the formed protrusion 2 may have any thickness S_pThickness S_pPreferably about the pitch P_a，p20-100% of the total weight of the composition. Height e of the projection 2_pDepending on the cutting depth t (see fig. 1b, 8a and 8b) and the angle theta at which the ridge layer 4 is cut. Height e of the projection 2_pPreferably at least as large as the cutting depth t, up to three times the cutting depth t. Preferably, but not necessarily, at a height e_rThe ridge 1 is formed and the angle theta is set so as to be convexHeight e of 2_pAt least about the ridge 1 height e_rTwice as much. Thus, e_p/D_iIs preferably between about 0.002 and 0.5 (i.e., e)_p/D_iIs e_r/D_iAbout twice the ratio of the preferred range of 0.001-0.25).

FIGS. 1a and 1b show that the cutting depth t is equal to the height e of the ridge 1_rAnd thus the base 40 of the projection 2 is located on the inner surface 18 of the tube 21. However, the cutting depth t does not have to be equal to the ridge height e_r. Instead, the ridge 1 may be only partially severed (see fig. 8a) or beyond the height of the ridge 1 and into the pipe wall 3 (see fig. 8 b). In fig. 8a, not along its entire height e_rThe ridge 1 is cut so that the base 40 of the projection 2 is further from the inner surface 18 of the tube 21 than the base 42 of the ridge 1, the base 42 being on the inner surface 18. Conversely, FIG. 8b shows a greater ridge height e_rSo that at least one wall of the projection 2 extends into the pipe wall 3 beyond the inner surface 18 and the ridge base 42.

When the ridge layer 4 is lifted, grooves 20 are formed between adjacent protrusions 2. The ridge layer 4 is cut and lifted so that the grooves 20 are oriented on the inner surface 18 at an angle τ to the axis s of the tube 21 (see fig. 1e, 11a and 11b), which is preferably, but not necessarily, between about 80 ° and 100 °.

The shape of the protrusion 2 depends on the shape of the ridge 1 and the orientation of the ridge 1 with respect to the direction of movement of the tool 13. In the embodiment shown in fig. 1a-e, the protrusion 2 has four side surfaces 25, a sloped top surface 26 (which helps reduce the thermal resistance to heat transfer), and a generally pointed tip 28. The projection 2 of the present invention is by no means limited to this illustrated embodiment, but may be formed in any shape. And the protrusions 2 in the tube 21 do not necessarily all have the same shape or have the same geometry.

Whether the direction of the protrusions 2 is straight (see fig. 10a) or curved or twisted (see fig. 10b), depends on the angle β formed between the ridge 1 and the direction of movement g of the tool 13. If the angle β is less than 90 °, the protrusions 2 have a relatively straight orientation, as shown in fig. 10 a. If the angle β is greater than 90 °, the protrusions 2 have a more curved and/or twisted orientation, as shown in fig. 10 b.

During the manufacture of the tube 21, the ridge 1 is cut through with the tool 13 and the resulting ridge layer 4 is lifted to form the protrusion 2. Other devices and methods may be used to form the projections 2. The tool 13 may be made of any metal-cutting resistant material having structural integrity (e.g., steel, carbide, ceramic, etc.), but is preferably made of carbide. The embodiment of the tool 13 shown in fig. 6a-d and 7a-d generally has a tool axis q, two base walls 30, 32 and one or more side walls 34. An aperture 16 is provided through the tool 13. The tip 12 is formed on a side wall 34 of the tool 13. Note, however, that the tip may be mounted or formed on any structure capable of supporting the tip in a desired orientation relative to the tube 21, and such structure is not limited to that shown in fig. 6a-d and 7 a-d. Furthermore, the tips are retractable within their support structure so that the number of tips during cutting can be easily varied.

Fig. 6a-d show one embodiment of the tool 13 with a single tip 12, and fig. 7a-d show an alternative embodiment of the tool 13 with four tips 12. It will be clear to a person skilled in the art that the tool 13 may be provided with any number of tips 12, depending on the predetermined pitch P determined for the protuberances 2_a，p. And the geometry of each tip need not be the same as the tip on a single tool 13. Instead, tips 12 having different geometries may be provided on the tool 13 to form projections having different shapes, orientations, and other geometries.

Each tip 12 is formed by the intersection of planes a, B and C. The intersection of the planes a and B forms a cut edge 14 that cuts through the ridge 1 to form the ridge layer 4. Plane B is formed with respect to a plane perpendicular to the tool axis qIs oriented (see fig. 6 b). CornerIs defined as 90 deg. -theta. Such anglePreferably between about 40-70, allowing the cutting edge 14 to cut through the ridge 1 at a desired angle theta between about 20-50. The intersection of the planes a and C forms a lifting edge 15 which lifts the ridge layer 4 upwards forming the protrusion 2. CornerDefined by plane C and a plane perpendicular to the tool axis q, the angleThe angle of inclination ω (i.e. the angle between a plane perpendicular to the longitudinal axis of the tube 21 and the longitudinal axis of the protrusion 2) at which the lifting edge 15 lifts the protrusion 2 is determined. CornerAnd thus the angle on the tool 13Can be adjusted to directly influence the inclination angle omega of the protrusion 2. Angle of inclination omega (sum angle)) Preferably at an absolute value of any angle between about-45 deg. and 45 deg. relative to a plane perpendicular to the longitudinal axis s of the tube 21. Such that the projections may be aligned with a plane perpendicular to the longitudinal axis s of the tube 21 (see fig. 1b), or inclined to the left and right with respect to a plane perpendicular to the longitudinal axis s of the tube 21 (see fig. 1 c). Also, the tips 12 may be formed in different shapes (i.e., different corners on the tips)Different) so that the projections 2 in the tube 21 can be inclined at different angles (or completely different) and in different directions with respect to a plane perpendicular to the longitudinal axis s of the tube 21.

Although preferred ranges for the physical dimensions of the protrusions 2 have been given, those skilled in the art will appreciate thatThe person will appreciate that the physical dimensions of the tool 13 may be modified to influence the physical dimensions of the protrusion 2 thus obtained. For example, the cutting edge 14 cuts into the ridge 1 to a depth t, and an angleInfluencing the depth e of the projection 2_p. Therefore, the depth e of the projection 2 can be adjusted by the following expression_p

Or, given

e_p＝t/sin(θ)

Wherein:

t is the cutting depth;

is the angle between plane B and a plane perpendicular to the tool axis q; and

theta is the angle at which the ridge layer 4 is cut relative to the longitudinal axis s of the tube 21.

Thickness S of the projection 2_pDepending on the pitch P of the bumps 2_a，pAngle of harmony

Therefore, the thickness S can be adjusted by the following expression_p

Or, suppose

S_p＝P_a，p·sin(θ)

Wherein:

P_a，pis the axial pitch of the lobes 2;

is the angle between plane B and a plane perpendicular to the tool axis q; and

theta is the angle at which the ridge layer 4 is cut relative to the longitudinal axis s of the tube 21.

Figures 4 and 5 show one possible mechanism for reinforcing the surface of the tube 21. These figures in no way limit the process of manufacturing tubes according to the present invention, but rather the tube manufacturing process may use any suitable apparatus or combination of apparatuses. The tube of the present invention may be manufactured from a variety of materials having suitable physical properties including structural integrity, ductility and plasticity, such as copper and copper alloys, aluminum and aluminum alloys, brass, titanium, steel and stainless steel. Fig. 4 and 5 show three knife shafts 10 operating on the tube 21 to reinforce the outer surface of the tube 21. Note that one of the cutter shafts 10 is omitted in fig. 4. Each arbor 10 comprises a tool mechanism with a fin disk 7, the fin disk 7 being radially extruded in a head-to-head manner with an axial pitch P_a，oAnd outer fins 6. The tool mechanism includes additional discs, such as notched or flattened discs, to further strengthen the outer surface of the tube 21. Furthermore, although only three arbors 10 are shown, fewer or more arbors may be used depending on the intended reinforced outer surface. Note, however, that depending on the tube application, the outer surface of the tube 21 may not need to be provided with a reinforcing portion at all.

In one embodiment where the inner surface of the tube 21 is reinforced, the arbor 11 with the mandrel 9 rotatably mounted thereto extends into the tube 21. The tool 13 is mounted on the shaft 11 through an aperture 16. The bolt 24 secures the tool 13. The tool 13 may be rotationally fixed, preferably relative to the shaft 11, in any suitable way. Figures 6d and 7d show a keyway 17, the keyway 17 being provided on the tool 13 to interlock with a (not shown) projection on the shaft 11 to secure the tool 13 in position relative to the shaft 11.

In operation, the tube 12 is typically rotated during its mobile manufacturing process. The tube wall 3 moves between the mandrel 9 and the fin plate 7, which exerts pressure on the tube wall 3. Under pressure, the metal of the tube wall 3 flows into the grooves between the fin discs 7 to form fins 6 on the outer surface of the tube 21.

Mandrel 9 is provided with a mirror image of the desired inner surface pattern so that when tube 21 and mandrel 9 are mated, mandrel 9 will form a predetermined pattern on inner surface 18 of tube 21. As shown in fig. 1a and 4, the desired inner surface pattern comprises ridges 1. After forming the ridge 1 on the inner surface 18 of the tube 21, the tube 21 encounters the tool 13 adjacent the mandrel 9 and downstream of the mandrel 9. As previously explained, one or more cutting edges 14 of the tool 13 cut through the ridge 1 to form the ridge layer 4. One or more lifting edges 15 of the tool 13 subsequently lift the ridge layer 4 in order to form the protrusions 2.

When the projections 2 are formed simultaneously with the external fins and the tool 13 is fixed (i.e. not rotated or moved axially), the tube 21 is automatically rotated with an accompanying axial movement. In this case, the axial pitch P of the projections_a，pDetermined by the following equation:

wherein:

P_a，ois the axial pitch of the outer fins 6;

Z_othe number of fins on the outer diameter of the tube 21; and

Z_ithe number of tips 12 on the tool 13.

For obtaining a specific axial pitch P of the projections_a，pThe tool 13 may also be rotated. The tube 21 and the tool 13 may be rotated in the same direction, or alternatively, the tube 21 and the tool 13 may be rotated in opposite directions. To obtain a predetermined axial pitch P of the projections_a，pThe required rotation of the shaft 13 (in Revolutions Per Minute (RPM)) can be calculated by the following equation:

wherein:

RPM_toolis the rotational frequency of the tube 21;

P_a，ois the axial pitch of the outer fins 6;

Z_othe number of fins on the outer diameter of the tube 21;

P_a，pis the desired axial pitch of the lobes 2; and

Z_ithe number of tips 12 on the tool 13.

If this calculation is negative, the tool 13 is rotated in the same direction as the tube 21 to obtain the desired pitch P_a，p. Alternatively, if this calculation is positive, the tool 13 is rotated in the opposite direction to the tube 21 to obtain the desired pitch P_a，p。

It is noted that although the formation of the projections 2 is shown in the same operation as the formation of the ridges 1, the projections 2 may be produced from the fins in a separate operation with a tube with preformed inner ridges 1. This generally requires an assembly to rotate the tool 13 or tube 21 and move the tool 13 and tube 21 along the tube axis. And a support is preferably provided to centre the tool 13 relative to the inner tubular surface 18.

In this case, the axial pitch P of the projections 2_a，pIs defined by the following equation:

P_a，p＝X_a/(RPM·Z_i)

wherein:

xa is the relative axial velocity (distance/time) between the tube 21 and the tool 13;

RMP is the relative rotational frequency between the tool 13 and the tube 21;

P_a，pis the desired axial pitch of the lobes 2; and

Z_ithe number of tips 12 on the tool 13.

This formula holds true for (1) when the tube is only moving axially (i.e., not rotating) and the tool is only rotating (i.e., not moving axially); (2) when the tube is only rotating and the tool is only moving axially; (3) the tool rotates and moves axially, but the tube is fixed and neither rotates nor moves axially; (4) the tube rotates and moves axially, but the tool is fixed and neither rotates nor moves axially; and (5) any combination of the above.

With the inner tube surface of the present invention, additional paths for fluid flow (through the grooves 20 between the protrusions 2) are created to optimize heat transfer and pressure drop. Fig. 9a shows an additional path 22 for these fluids to flow through the tube 21. These paths 22 are created between the ridges 1 in addition to the fluid flow paths 23. These additional paths 22 have a helix angle alpha relative to the tube axis s₁. Angle alpha₁Is the angle between the protrusions 2 formed by adjacent ridges 1. Fig. 9b clearly shows these additional paths 22 formed between the protrusions 2. By the following expression, the pitch P of the projections 2 can be adjusted_a，pTo adjust the helix angle alpha₁And the orientation of the path 22 through the tube 21

Wherein:

P_a，ris the axial pitch of the ridges 1;

α is the angle of the ridge 1 to the tube axis s;

α₁a desired helix angle between the lobes 2;

Z_ithe number of tips 12 on the tool 13; and

D_iis the inner diameter of the tube 21 as measured from the inner surface 18 of the tube 21.

If both the ridge pitch angle α and the angle τ of the flutes 20 are right-handed or left-handed spirals (see FIG. 11b), "[ - ]" should be used in the above expression. Alternatively, "[ + ]" should be used in the above expression if the helix angle α and the angle τ of the flutes 20 are of opposite handedness (see fig. 11 a).

The tube made according to the present invention is superior to existing tubes. The enhanced performance of two examples of such tubes (boiling Tube No.25 and Tube No.14) is shown by demonstrating the difference in enhancement factors between the tubes. The heat transfer coefficient (both Tube sides and all) of these new tubes (Tube No.25 and Tube No.14) is increased over the existing tubes (Tube No.)And). Also Tube nos. 25 and 14 are only examples of tubes according to the invention. Other types of tubes made according to the present invention are superior to existing tubes used in a variety of equipment applications.

PipeAndare described in tables 1 and 2 of U.S. patent No.5697430 to Thors et al.Introduced as Tube II;introduced as tube III;introduced as Tubei IV_H. Outer surfaces of Tube No.25 and Tube No.14 andare equivalent to each other. Tube No.25 and Tube No.14 are consistent with the present invention and include the following physical attributes:

TABLE 1 tube and Ridge size

TABLE 2 bulge size

Further, the tool for forming projections on Tube nos. 25 and 14 has the following features:

TABLE 3 tool dimensions

The Tube side heat transfer coefficient of Tube No.14 was about1.8 times, Tube side heat transfer coefficient of Tube No.25 is about1.3 times of the total weight of the composition,is currently the most widely used tube in evaporator devices and is shown as a baseline in fig. 12 and 13. Similarly, the Tube side heat transfer coefficient of Tube No.25 is approximately1.25 times, Tube side heat transfer coefficient of Tube No.14 is about1.5 times of the total weight of the powder.

The foregoing is provided for the purpose of illustrating, explaining and describing embodiments of the present invention. Further variations and modifications to these embodiments will be readily apparent to those skilled in the art, and may be made without departing from the spirit or scope of the invention.

Claims (19)

1. A method of manufacturing a tube having a longitudinal axis, comprising:

a. cutting through at least one ridge formed along the inner surface of the tube at an angle relative to the longitudinal axis to a cutting depth to form a ridge layer; and

b. the ridge layer is raised to form protrusions having a protrusion height, a protrusion thickness, and a protrusion pitch.

2. The method of claim 1, wherein at least one ridge is cut through at an angle between 20 ° and 50 ° relative to the longitudinal axis of the tube.

3. The method of claim 2, wherein at least one ridge is cut through at an angle of 30 ° relative to the longitudinal axis of the tube.

4. The method of claim 1, wherein at least one ridge has a ridge height and the cutting depth is equal to the ridge height.

5. The method of claim 1, wherein at least one ridge has a ridge height and the cutting depth is less than the ridge height.

6. The method of claim 1, wherein at least one ridge has a ridge height and the cutting depth is greater than the ridge height.

7. The method of claim 1, wherein lifting the ridge layer to form a protrusion comprises: the ridge layer is lifted such that at least one protrusion extends from the inner surface in a direction perpendicular to the longitudinal axis.

8. The method of claim 1, wherein lifting the ridge layer to form a protrusion comprises: the ridge layer is lifted such that the at least one protrusion extends from the inner surface in a direction that is not perpendicular to the longitudinal axis.

9. The method of claim 1, wherein lifting the ridge layer to form a protrusion comprises: the ridge layer is lifted such that at least one protrusion extends from the inner surface in a direction perpendicular to the longitudinal axis and at least one protrusion extends from the inner surface in a direction non-perpendicular to the longitudinal axis.

10. The method of claim 1, wherein at least some of the protrusions are at least partially twisted.

11. The method of claim 1, wherein the ridges are formed along the inner surface at an angle between 0 ° and 90 ° relative to the longitudinal axis of the tube.

12. The method of claim 1, further comprising forming fins on an outer surface of the tube.

13. The method of claim 1 wherein the cutting and lifting are performed with a tool comprising a tool axis and at least one tip intersecting at least a first plane, a second plane, and a third plane, the tip having a cutting edge intersecting the first plane and the second plane and a lifting edge intersecting the first plane and the third plane.

14. The method of claim 13, wherein the second plane is oriented at an angle of between 40 ° and 70 ° relative to a plane perpendicular to the tool axis.

15. The method of claim 13, wherein the third plane is oriented at an angle relative to a plane perpendicular to the tool axis and the projection is oriented at an angle relative to a plane perpendicular to the longitudinal axis of the tube.

16. The method of claim 15, wherein the angle of the third plane relative to a plane perpendicular to the tool axis is equal to the angle of the projection relative to a plane perpendicular to the longitudinal axis of the tube.

17. The method of claim 15, wherein the angle of the third plane relative to a plane perpendicular to the tool axis and the angle of the projection relative to a plane perpendicular to the longitudinal axis of the tube is no greater than 45 °.

18. The method of claim 13, further comprising usingOr e_pThe bump height is predetermined as t/sin (θ), where:

e_pis the height of the projection;

t is the cutting depth;

is the angle between the second plane and a plane perpendicular to the tool axis; and

θ is the angle through which at least one ridge layer is cut relative to the longitudinal axis of the tube.

19. The method of claim 13, further comprising usingOr S_p＝P_a，pSin (θ) predetermined bump thickness, wherein:

S_pis the thickness of the bulge;

P_a，pis the bump pitch;

is the angle between the second plane and a plane perpendicular to the tool axis; and

θ is the angle through which at least one ridge layer is cut relative to the longitudinal axis of the tube.