JP2010532855A - Finned tube with stepped top - Google Patents

Abstract

The present invention has a tube with helical fins extending from the outer surface of the tube. The fin and tube are integral or formed in one part and have a groove defined between adjacent fins. The fin has a top with a peak and a depression formed at the top. The fin peak has a recess formed on a side surface, and the recess has a side surface and a base surface. The side surface of the hollow portion intersects with the upper part of the fin peak, and the base surface of the hollow portion intersects with the side wall of the fin.
[Selection] Figure 2

Description

  This application claims the benefit of Chinese Patent Application No. 200710043537, filed July 6, 2007, with the title “A HEAT TRANSFER TUBE FOR CONDENSING APPLICATION”.

  The present invention relates to a finned tube, and more particularly to a tube used for heat transfer.

  For many years finned tubes have been used for heat transfer. Since heat flows from the hot side to the cold side, heat transfer is realized by transferring heat from the hot material to the cold material. There is also heat released when the substance condenses from vapor to liquid, and heat is absorbed from the liquid to the gas as the liquid evaporates or evaporates. When a finned tube is used for heat transfer, the hot material is either inside or outside the tube and the cooler material is on the opposite side. Usually, heat transfer is possible without mixing the hot material and the cold material by the tube.

  For cooling purposes, the cooling medium is a liquid such as cooling water flowing through a shell or heat exchanger, or a gas such as air blown onto a finned tube. Similarly, the heating medium is either a liquid or a gas. Finned tubes are sometimes used instead of relatively smooth tubes because they tend to increase the heat transfer rate. Thus, a smaller heat exchanger with a finned tube can transfer as much heat for a given application as a larger heat exchanger with a relatively smooth tube. Finned tube designs affect the heat transfer rate and are sometimes designed differently for specific heat transfer applications. For example, finned tubes used for condensation tend to have a different design than finned tubes used for vaporization.

  An example of the prior art includes a finned tube with a helical protrusion formed on the inner surface of the tube and a fin formed on the outer surface of the tube. The groove is defined by adjacent fins on the outer surface of the tube, and the groove has a curved “U” shaped lower portion, or the groove has a flat bottom. When used as a condensing tube for condensing vapor outside the tube and cooling water inside the tube, the groove is easily filled with liquid condensate. The condensate acts to insulate the tube, limiting the cooling required for further condensation. Since the condensate tends to spread along the bottom of the flat groove instead of scooping up the sides of the fin, the bottom is preferably flat. This eliminates condensate in more surface areas of the fin and promotes heat transfer.

  Moreover, since the tube with a fin has the crack formed in the fin, the condensate which flows in the groove part between two fins may flow into a different groove part through a crack. In the other finned tube, the outer portion of the fin is bent, and the bent portion is a portion of the passage formed between the base portion of the fin and the upper portion of the fin. This makes a further angle to the fins and the tube repels the liquid condensate more quickly. If the liquid condensate is repelled from the tube more quickly, heat transfer is likely to be enhanced. The other fin has a notch or a drop formed at the top of the fin and has a peak defined between the drop. In some cases, the peaks are bent to form a curled shape. This further increases the curvature and angle of the fins, making it easier for the tube to play liquid condensate more quickly.

  By applying the fin material to a relatively smooth tube, a finned tube is produced and the fin is not formed from the material of the tube body. This increases the area available for heat transfer and improves the heat transfer rate, but the interface between the fins and the tube causes resistance to heat flow. Although the fins attached to the tube extend radially from the tube axis, they stand upright from the tube, but they are also curved or bent in various ways. There are many designs of existing finned tubes, but changes that improve heat transfer are always awaited.

  The present invention has a tube with helical fins extending from the tube outer surface. Since the fin and the tube are formed of one part, the fin is integrated with the tube. The fin has a fin top with a peak and a drop between peaks, and has a groove defined between adjacent fins. It has the hollow part prescribed | regulated to a fin peak along a side surface, and a hollow part has a side surface which cross | intersects the upper part of a fin peak. The base surface of the recess extends in a groove defined between the two fins, and the recess forms a step on the side surface of the fin peak. Tube fins and deformation increase the speed of heat transfer across the tube.

FIG. 1 shows a side cross-sectional view of a heat exchanger. FIG. 2 shows a side cross-sectional view of a portion of the tube wall. FIG. 3 shows one fin before the peak and drop are formed. FIG. 4 shows one fin after forming the peak and drop but before forming the depression. FIG. 5 shows one fin after the formation of the peak, drop and depression. FIG. 6 is a plan view of the outer surface portion of the tube, showing the fins as straight vertical walls prior to deformation of the peaks or drops for clarity of the drawing. FIG. 7 is a cross-sectional side view of one fin along line 7-7 of FIG. FIG. 8 is a plan view of the outer surface portion of the tube, showing the fins as straight vertical walls after deformation of the peak or drop but before deformation of the depression. FIG. 9 is a cross-sectional side view of one fin along line 9-9 of FIG. FIG. 10 is a plan view of a portion of the outer surface of the tube, showing the fins as straight vertical walls after deformation of the peaks, drop and depressions. 11 is a cross-sectional side view of one fin along line 11-11 in FIG. FIG. 12 is a plan view of a portion of the outer surface of the tube showing the fins as straight vertical walls after deformation of the peaks, the drop and the depressions on both sides of the fin. 13 is a cross-sectional side view of one fin along line 13-13 in FIG. FIG. 14 is a plan view of the outer surface portion of the tube, showing the fin as a straight vertical wall after deformation of the peak, drop and two stepped depressions on either side of the fin. FIG. 15 is a side cross-sectional view taken along line 15-15 of FIG. FIG. 16 is a side sectional view of the tube wall formed by the shaft and the internal support.

  The finned tube according to the invention is used for heat transfer and mainly for the condensation of liquid on the outer surface of the tube. In an exemplary embodiment, the coolant flowing inside the tube absorbs the heat of condensation as vapor condensation. The fin design on the tube outer surface increases heat transfer by increasing the surface area of the tube and also improving the condensation and divergence performance of the tube. Also, other aspects of the tube design improve the heat transfer rate. Tubes are most often used in shell configurations and tube heat exchangers, but it is also possible to use finned tubes for other heat transfer applications.

Condensation Principles As heat is transferred from the condensed vapor outside the tube to the coolant inside the tube, heat transfer can be considered in several distinct stages. Similar basic steps apply when heat moves through a barrier, such as a tube wall, or between two media at different temperatures. Such an explanation is given with respect to the cooling liquid inside the tube from the condensed vapor outside the tube, but different applications are possible.

  Steam outside the tube needs to transfer heat to the coolant inside the tube. When the steam condenses, a specific amount of heat is released, and this amount of heat is called condensation heat. In general, there is a layer of condensate on the outer surface of the tube, so the first step is the transfer of heat from the steam to the condensate of the tube. And although heat flows through a condensate, since a condensate acts as a heat insulator in many cases, it becomes resistance of heat flow. After heat flows through the condensate, it moves from the condensate to the outer surface of the tube. There is an interface between the condensate and the outer surface of the tube, which provides resistance to heat flow.

  As heat moves to the outer surface of the tube, it must flow from the outer surface of the tube to the inner surface. In order to facilitate such heat flow, heat transfer tubes are typically made of materials or heat conductors that readily conduct heat. In general, there is an essentially stagnant liquid film containing the inner surface of the tube wall. After the heat flow flows through the tube wall, it must travel through the interface between the inner surfaces of the tube wall to the adjacent layer of coolant inside the tube. And heat needs to flow through this thin liquid film.

  The more turbulent or steep the coolant flow in the tube, the thinner the layer of stagnant liquid that floats near the tube wall. Thus, a tube design that causes mixing or agitation of the liquid within the tube provides advantages. Turbulent flow causes mixing of the cooling liquid, and more cooling water flow increases cooling water turbulence compared to laminar flow. Also, the configuration of the inner surface of the tube, such as a rough surface or spiral groove that promotes swirl, promotes turbulence and mixing of the coolant inside the tube. Heat transfer to the flowing coolant in the tube is then released when the liquid exits the tube.

  If the fin is configured separately from the tube and then attached, there is an interface between the fin and the tube. This is true if the fins and tubes are made of the same material, such as copper, or different materials. The interface creates resistance to heat flow. When the fin is formed from the tube wall, there is no resistance and heat flow is improved. In this description, the fins formed from the tube wall are considered integral with the tube, and it is preferred to integrate the fin with the tube to minimize heat flow resistance.

  The tube needs to be made of a malleable material or the fins can be formed from the tube without cracks or cracks formed in the tube wall. Cracks or fissures limit the structural integrity and strength of the tube. In general, these tubes 10 are used in a shell and tube heat exchanger 8, and the ends of the tubes are fixed to a tube sheet 6 of the heat exchanger, as shown in FIG. The malleable tube 10 is easy to incorporate into the tube sheet 6 of the heat exchanger. Further, the tube needs to be made of a material that easily conducts heat.

  The finned tube 10 has design considerations specifically regarding the collection of condensate on the outer surface of the tube. In many cases, the heat exchanger 8 uses several layers of the horizontal tube 10 and the condensate from the upper layer drips to the lower layer. Since the tube 10 on the lower layer side easily overflows or is covered with the condensate, the heat transfer efficiency is lowered. The tube 10 is more suitable for playing condensate than others. As the condensate is repelled more quickly, the layer of condensate in the tube 10 becomes thinner and the resistance to heat flow decreases. Condensate repelling performance is particularly important for the tube 10 in the lower part of the horizontal heat exchanger 8. For this reason, the tube 10 that repels the condensate more quickly is suitable by providing a quicker heat flow across the heat exchanger 8.

  One aspect in which the tube repels the condensate more quickly is the ability of the outer surface to collect the condensate in droplets. This is often done by providing a sharp point or curved surface on the outer surface. Sharp points or curved surfaces are actually recessed, and the condensate is collected in a concave manner due to surface tension, so that it tends to function as a storage for condensate droplets. The concave area tends to collect the condensate in droplets, which move around the tube more quickly and fall off the tube, so the tube repels the condensate more quickly. Condensate tends to avoid convex surfaces because the surface tension effect tends to pull the condensate away from the convex surface region or easily pull away. For this reason, the convex surface region is relatively free of condensate and has a low resistance to heat flow. Curved or sharp points generally give convex and concave surfaces at various locations, helping the condensate to be repelled more quickly with areas of the tube that have little or no condensate, and transfer heat more quickly To do.

  It can also be said that the heat flow becomes faster when the surface area of the condensation tube is increased. As the fins are formed in the tube, it increases the surface area of the tube, which acts to increase the heat transfer rate across the tube.

Finned Tube Body Various views of one embodiment of a finned tube 10 according to the present invention are shown in FIGS. 1 and 2, which are cross-sections of the tube wall to show the details of the surface. Tube 10 has a body 12 having an outer surface 14 and an inner surface 16. The body 12 is the base of the shape or structure of the outer surface 14 or the inner surface 16. The body 12 should be made of a material that is easy to conduct heat. Metals are generally good heat conductors and are frequently used for the construction of tubes according to the present invention. Moreover, the metal needs to be malleable so that various structures of the inner surface 16 and the outer surface 14 can be formed without impairing the integrity of the tube body 12. Thereby, the structure formed from the tube main body 12 can be integrated with the main body 12. Copper can be used because it is a good thermal conductor and is malleable, but other materials including aluminum, steel, and non-metallic materials can also be used.

Tube Fin The tube 10 has at least one fin 20 formed on its outer surface 14. The fins 20 generally project and extend radially from the outer surface 14 of the tube body, typically in a spiral. One fin 20 can be spirally wound over the entire length of the tube 10. It is also possible to receive all of the plurality of fins 20 around the tube 10 in a spiral manner. In a simple case, when viewing a portion of the outer surface 14 of the tube body, it appears as if it has several adjacent circumferential fins 20 that protrude from the outer surface 14 of the tube body. When viewed along the axial direction of the tube 10, the portions of the fins 20 that are adjacent to each other are considered as if the adjacent fins 20 were the same fin 20 spirally wound on the outer surface 14 of the tube body. Since the fin 20 is formed of the material of the tube main body 12, the fin 20 is integrated with the tube main body 12.

  Each fin 20 has several portions including a fin base 22 that is the point where the fin 20 joins to the outer surface 14 of the tube body. The fin top 24 faces the fin base 22 and is the uppermost point of the fin 20 with respect to the tube shaft 26. The fin height 27 is the distance between the fin base 22 and the fin top 24. The fin side wall 28 has a left side wall 30 and a right side wall 32 that faces the left side wall 28. A groove 34 is defined between two adjacent fins 20 such that the groove 34 is between the left side wall 30 of one fin 20 and the right side wall 32 of the adjacent fin 20. The fins 20 are generally perpendicular to the tube body 12 such that the fins 20 extend essentially straight from the outer surface 14 of the tube body. In such a case, the fin 20 extends vertically from the tube shaft 26. Also, the fins 20 can be arranged at other angles with respect to the outer surface 14 of the tube body.

  The fin apex 24 has a plurality of lowered portions 36, as best shown in FIGS. 3, 4 and 5, which show the fin 20 in a continuous form with reference to FIGS. The lowered portion 36 has an inclination angle 38 defined by the angle of the lowered portion 36 with respect to the fin top 24. The tilt angle 38 can range from 0 ° to 90 ° such that the drop 36 is perpendicular to the fin 20, or the drop 36 can be set at various angles with respect to the fin 20. The drop 36 generally has a depth 40 of 0.1 to 0.5 millimeters. The lowered portion 36 does not extend to the fin base 22, and therefore has a positive fin height 27 at the lowered portion 36. A plurality of peaks 42 are defined between adjacent drops 36 or, in an alternative view, a plurality of drops 36 are defined between adjacent peaks 42. The peak 42 is formed from the fin 20 at the fin top 24, similar to the lowered portion 36. For this reason, the fin top portion 24 has a peak 42 and a lowering portion 36, so that the fin top portion 24 has a gun-like appearance like a castle wall. The fin height 27 at the peak 42 is larger than the fin height 27 at the lowered portion 36.

  Since the lowered portion 36 is cut into the fin top portion 24, the material in the lowered portion 36 can be pushed to the side so that the peak 42 is twisted with respect to the fin 20. As a result, a part of the fin peak 42 extends into the groove 34 between the adjacent fins 20, so that the fin peak 42 becomes like a ridge 45. The flange 45 is at least partially above the groove portion 34, and a line perpendicular to the tube axis 26 passes through the groove portion 34 and the portion of the flange 45, but does not pass through other portions of the fin 20. Also, due to the further shape change to the collar 45, it is at least partially above the groove 34 as opposed to above the fin 20.

  The collar 45 is what is referred to as the platform 44 in this description. Platform 44 is a portion of fin top 24 that is formed to extend over adjacent groove 34 rather than over fin 20. The collar 45 is the tip of the platform 44 when the platform 44 is formed from the fin peaks 42. Further, the platform 44 can be formed from the lowered portion 36. This is the case when the material from the lowering part 36 is pushed downward during the formation of the lowering part. Even a platform 44 extending simultaneously from both the peak 42 and the drop 36 is possible. The plurality of platforms 44 provide additional curvature, angle, and surface area of the fins 20 and provide materials that can be formed and utilized to provide additional curvature and angle.

  The fin peak 42 may be considered to have a side 46 that includes a left peak side 48, a right peak side 50, a front peak side 52, and a back peak side 54. The left peak side surface 48 is formed integrally with a part of the left fin side wall 30, and the right peak side surface 50 is formed integrally with a part of the right fin side wall 32. At a recess angle of inclination 38, the left and right peak sides 48, 50 can be partially integrated or face the drop 36. Also, the left and right peak sides 48, 50 can be formed by pushing over the groove 34 adjacent to the fin 20. However, the left and right peak sides 48, 50 are considered part of the left and right fin sidewalls 30, 32.

  The peak 42 also has a front surface 52 and a back surface 54, with the front surface 52 and the back surface 54 generally facing the top and bottom of the fin crest 24 or toward the adjacent drop 36. Similar to the left and right peak side surfaces 48 and 50, the front and rear peak surfaces 52 and 54 slightly face the groove 34 depending on the inclination angle 38 of the lowered portion as shown. Also, the left and right peak side surfaces 48 and 50 are substantially vertical, but face the groove 34 on either side of the fin 20. When referring to the substantially vertical left peak side 48, right peak side 50, front 52 and back 54, instead of moving further parallel to the tube outer surface 14, these surfaces move further up and down relative to the tube outer surface 14. It means that it extends.

  The four peak surfaces 48, 50, 52, and 54 are not necessarily smooth, straight, and need not form a flat surface, but may form a protruding rough curved surface. There is not always a clear angular boundary between adjacent peak surfaces, so that the left side surface 48 has rounded corners and gradually integrates into the front 52 and back 54. In practice, the peak 42 can be rounded when viewed from above, but the four peak surfaces 48, 50, 52, 54 are still useful references for discussing the characteristics of the peak 42. It is also provided. Also, it has an upper portion 56 at the top of the fin that intersects the four peak surfaces 48, 50, 52, 54. Similar to the peak surfaces 48, 50, 52, 54, the upper portion 56 is not necessarily a well-defined flat surface, and the intersection of the upper portion 56 and the peak surfaces 48, 50, 52, 54 is not a sharp corner. Can also be blending.

Recessed portion Recessed portion 58 is defined in peak side surface 46 and may be formed in platform 44 extending from peak 42. The recess 58 has a side surface 60 that is a substantially vertical surface. The side surface 60 does not necessarily have to be strictly perpendicular, but is perpendicular to the tube axis 26, and the side surface 60 tends to extend vertically relative to the outer surface 14 of the tube rather than right and left. Further, the recess 58 has a base surface 62 that is roughly horizontal. The base 62 may not necessarily be completely horizontal to the outer surface 14 of the tube, but extends more parallel to or consistent with the outer surface 14 of the tube. The recess 58 has a coupling portion 64 where the side surface 60 and the base surface 62 meet. Preferably, the side surface 60 and the base surface 62 can define a distinguishable and definable intersection between the two surfaces, such an intersection defining a joint 64. The coupling portion 64 is along the fin base 22 when the recess 58 is formed along and parallel to the fin 20.

  The side surface 60 intersects the upper portion 56 of the fin peak, which is referred to as a seam 66. Preferably, the side surface 60 is well defined to find the seam 66 so that it has a distinguishable visible angle between the side surface 60 and the peak top 56. The base surface 62 intersects the fin sidewall 28 at an edge 68. As with the side surface 60, the base surface 62 is preferably well defined so that the edge 68 preferably forms a detectable angle. The indentation 58 is located on the side of the peak 42 so that the indentation 58 generally faces into the groove 34 between the two adjacent fins 20. Therefore, the base surface 62 intersects only the side wall 28 of one fin, and the base surface extends only to one groove portion 34. Similarly, one recess 58 faces only one groove 34, and the side surface 60 faces the same groove 34 as the base surface extends into.

  The side surface 60 and the base surface 62 of the recess 58 form a stepped structure or shape 70 on the side surface of the fin peak 42, whereby the fin peak 42 has a stepped 70 side surface. The step shape 70 has a relatively horizontal surface that intersects a relatively vertical surface. The relatively horizontal surface is the base surface 62, and the relatively vertical surface is the side surface 60. The side surface of the stepped shape 70 faces the groove 34.

  6-9 show plan and side cross-sectional views of the previous stage of the present invention, and FIGS. 10-15 show plan and side cross-sectional views of various embodiments of the present invention. 6 and 7, the fin 10 shows before the peak or the lowered portion is formed. 8 and 9, the fin 10 is shown with a peak 42 and a drop 36 formed on the fin top 24. FIG. 10 and 11 show the fin 10 having the depression 58 on one side. In FIGS. 12 and 13, the fin 10 has the depression 58 on both sides. Further, the recess 58 has two or more steps 70, and the recess 58 has at least two side surfaces 60 and two base surfaces 62 as shown in FIGS.

  When there are a plurality of steps 70 and the depression has one side surface 60 above another side surface 60, only the uppermost side surface 60 intersects the peak upper portion 56 at the seam 66. Similarly, a plurality of steps 70 provide one base surface 62 above another base surface 62, and only one base surface 62 intersects the fin sidewall 28 at the edge 68. Indentations 58 may be provided on both the left and right peak sides 48, 50 and a stepped side 46 may be provided on the opposite side of the fin peak 42. Furthermore, each recess 58 may have two or more steps 70. If both peak side surfaces 48, 50 have a recess 58 with a plurality of steps 70, the peak 42 has at least four steps 70. The edge 68, seam 66, and coupling portion 64 of the recess 58 all provide edges and acute angles to enhance the performance of the finned tube 10.

  Since the platform 44 can be part of the peak side 46, a recess 58 can be formed in the platform 44. A recess in the platform 44 allows at least a portion of the base surface 62 to be received above the groove 34 between two adjacent fins 20. With the platform 44 on both sides of the peak 42, two depressions on either side of the peak 42 with the base surface 62 of each depression 58 at least partially above the groove 34 instead of above the fins 20. 58 may be included.

Top of Inner Surface As shown in FIG. 2, heat transfer across the tube 10 may be improved by providing good heat transfer from the inner surface 16 of the tube body to the coolant in the tube 10. The protrusion 74 protrudes from the inner surface 16 of the tube body and promotes faster heat transfer. The protrusion 74 of the inner surface 16 is generally spiral and has a depth 76 and a period. The period is the number of protrusions 74 within a predetermined distance. Further, the protrusion 74 is set at various angles with respect to the tube axis. The depth 76 and period of the protrusion 74 change, and the liquid can swirl in the tube 10 by setting the cutting angle. The swirling liquid tends to increase heat transfer by increasing the amount of stirring in the cooling liquid. Also, other shapes or structures of the tube inner surface 16 are possible and are within the framework of the present invention.

Tube Forming Process The finned tube 10 is generally formed from a relatively smooth tube 10 by a tube finning machine well known in the art. The tube finning machine has a shaft 80 as shown in FIG. 16 and as further referenced in FIGS. In many cases, the tube finning machine has three or more shafts 80 disposed around the tube 10, thereby holding the tube 10 in place by the shaft 80. The shafts 80 are positioned and angled so that each complements the other. The tube is provided and supplied through a finning machine such that the tube wall 82 is located between the shaft 80 and the internal support 84. The shaft 80 can deform the outer surface 14 of the tube and the inner support 84 can deform the inner surface 16 of the tube. The tube wall 82 generally rotates with respect to the shaft 80, and moves in the axial direction of the internal support portion 84 when the tube wall 82 rotates.

  The shaft 80 generally has several fin-forming disks 86 that continuously deform and sharpen the tube wall 82 and form one or more helical fins on the outer surface 14 of the tube. The continuous fin disk 86 tends to protrude deeper into the tube wall 82, and the fin 20 is formed and pushed up by the fin disk 86. The inner support portion 84 has a recess 88 so that when the fin 20 is formed on the outer surface 14 of the tube, a spiral protrusion 74 is formed on the inner surface 16 of the tube.

  After the fin disk 86 has deformed the fin 20, various other disks can be included on the shaft 80 to be further deformed, shaped, and defined in the final tube 10 configuration. After the fin disk 86, a knurling is applied to the lowered portion 36 of the fin top 24 using a knurling tool 90. When the knurling tool 90 is a blunter, the material that displaces to form the drop 36 is likely to accumulate at the base of the drop 36 and may have a platform 44 that projects into the groove 34 from the base of the drop 36. . The sharp knurling tool 90 cuts the drop 36 instead of crushing the drop 36, thereby creating a platform 44 on the side 46 of the fin peak. A knurling tool 90 can be set to form the drop 36 at various tilt angles 38, which affects where and how the platform 44 is formed.

  And although the hollow part 92 is formed in the peak 42 using the hollow tool 92, the hollow tool 92 can be used before the knurling tool 90. The shape of the hollow tool 92 determines the shape of the hollow portion 58. Possible shapes of the indentation tool 92 have teeth or a smooth circle. The indentation tool 92 can be shaped to form one step 70, or at least two peaks 70 as required. Using the indentation tool 92, the eccentric indentation 58 is press-fitted into the fin peak 42, whereby the fin peak 42 is stepped. The dimple tool 92 can be shaped or formed on either side of the peak 42, and if both sides are deformed, it can be done simultaneously or sequentially. Also, other tools for further shaping the outer surface 14 of the tube can be included on the shaft 80 as needed.

  The internal support portion 84 forms a protrusion 74 on the inner surface 16 of the tube using the recess 88. The internal support 84 rotates relative to the tube 10, or vice versa, but the internal support 84 can rotate relative to the tube 10 at various speeds rather than the shaft 80. A wide variety of tools or designs can be included in the inner support 84 and a wide variety of designs, shapes or textures can be formed on the tube inner surface 16. The improvement in heat transfer with respect to the outer surface 14 of the tube is most effective when the heat transfer rate of the inner surface 16 is comparable to or higher than the heat transfer rate of the outer surface 14. Many different considerations and factors affect the heat transfer rate, such as the material in contact with the surface, the flow rate, the phase change, and many others.

Advantages of the tube The described tube 10 is very effective when used to liquefy steam at the outer surface 14 with coolant passing through the interior of the tube 10. This type of use is an example of a possible use of the tube 10. Because the outer surface 14 has many angles and sharp corners, it facilitates liquefaction, and these angles and sharp corners provide a region that facilitates liquefaction to form droplets due to surface tension. Once these droplets are formed, the tube 10 drops the condensate more quickly by flowing downward and more easily falling off the tube 10. Also, the groove 34 between the fins 20 facilitates the flow of the condensate, thereby improving the rate at which the droplets fall out of the tube 10. This also improves the condensate drop performance of the present invention. Due to surface tension effects, the condensate tends to avoid convex regions such as fin top 24, seam 66 and edge 68. These relatively condensation-free regions provide little resistance to heat flow and increase the condensation rate.

  Fins 20, drop 36, platform 44, and depression 58 all increase the surface area of the outer surface 14 of the tube. Since heat flows through the surface, increasing the surface area increases the rate of heat flow. For this reason, deformation of the outer surface 14 of the tube that increases the surface area tends to increase the rate of heat flow.

  Further, the inner surface 16 of the tube promotes heat transfer because the protrusion 74 causes turbulent flow and swirls the coolant. Such turbulence and swirling cause mixing to minimize laminar flow and reduce the depth of the liquid layer that is in direct contact with the inner surface 16 of the tube. Also, the protrusion 74 increases the surface area of the inner surface 16, thereby enhancing heat transfer. A high top period and / or a large top depth 76 facilitates increasing the heat transfer rate, but a high top period and / or deeper top 76 also facilitates increasing resistance to coolant flow through the tube 10. As the coolant flow rate decreases, heat transfer can be slowed. For this reason, it is necessary to balance for the best heat transfer conditions.

  Actual testing of the present invention over existing technology using R134A for gas condensation outside the tube shows the advantages of the stepped fin top design. The heat exchange rate of the outer surface of the tube increased from 6.5% to 15% was measured. These improvements were achieved by using a stepped fin top design.

Dimensional Examples Although the dimensions of the present invention can be varied, dimensional examples are provided below and will provide at least one embodiment of the present invention.

  The distance between the fins is the distance between the center points of two adjacent fins 20, and this distance is 0.3 to 0.7 millimeters.

  The fin 20 has a thickness called the fin thickness, which is 0.05 to 0.3 millimeters.

  The fin 20 has a height 27 measured from the fin base 22 to the fin top 24, and the fin height 27 is 0.7 to 1.5 millimeters.

  The drop 36 formed on the fin top 24 has a depth 40 of 0.1 to 0.5 millimeters, and the drop 36 has a width that can be varied from 0.1 to 1 millimeter. .

  The protrusion 74 formed on the inner surface 16 of the tube has a depth 76, which is between 0.1 and 0.5 millimeters. The inner angle of the apex relative to the axis can be set to 46 ° and the starting point of the apex can vary from 8 to 50.

  The outer diameter of the tube 10 is 19 millimeters. Tube wall 82 has a thickness of 1.04 millimeters.

CONCLUSION Although the invention has been described with reference to a limited number of embodiments, it will be appreciated by those skilled in the art that other embodiments having the advantages of the invention may be devised without departing from the scope of the invention disclosed herein. You will understand. Accordingly, the scope of the invention should not be limited to the appended claims.

Claims (21)

A tube body having an outer surface;
At least one fin extending radially from an outer surface of the tube body, the fin having a fin top, a fin base, and a fin height measured from the fin top to the fin base;
A plurality of fin peaks formed on the top of the fin, the fin peaks having side surfaces, such that a plurality of fin drop portions are defined between the fin peaks;
At least one indentation defined on the side of the fin peak;
A finned tube characterized by comprising: Further, the hollow portion includes a side surface, a base surface, and a coupling portion defined by an intersection portion of the side surface and the base surface,
2. The finned tube according to claim 1, wherein the coupling portion is substantially parallel to the fin base. Adjacent fins define the groove,
The finned tube of claim 2, wherein the base surface is received at least partially above the groove.   The finned tube according to claim 1, wherein the fin is formed from the tube body, whereby the fin is integrated with the tube body. The recess has at least two side surfaces and two base surfaces;
The fin peak has an upper surface;
2. The finned tube according to claim 1, wherein only one side surface intersects the fin peak such that the hollow portion has at least two stepped shapes.   2. The finned tube according to claim 1, wherein the peak has two indentations, and the indentation is on the opposite side of the fin peak. The tube body has an inner surface;
The finned tube according to claim 1, wherein the finned tube includes a spiral protrusion protruding from an inner surface of the tube main body. A tube body having an outer surface;
At least one fin having a left and right side wall, a fin top and a fin base, extending spirally from the outer surface of the tube body such that a groove is defined between the left and right side walls of adjacent fins. A fin having a fin height measured from the fin top to the fin base;
A plurality of fin peaks formed at the top of the fin, the fin peak having an upper portion, such that a plurality of fin drop portions are defined between the fin peaks;
At least one recess defined by the fin peak, having a side surface and a base surface, the side surface of the recess portion intersects with the upper portion of the fin peak, and the base surface of the recess portion is one groove portion. A recess that faces only the groove, the side of the recess extending into the base and the base surface extending into;
A finned tube characterized by comprising:   9. The finned tube according to claim 8, wherein the fin is formed of the tube main body so that the fin is integrated with the tube main body. The recess has at least two side surfaces and at least two base surfaces;
9. The finned tube according to claim 8, wherein only one side surface intersects with an upper portion of the fin peak, whereby the recess has at least two steps.   9. The finned tube according to claim 8, wherein the recess has at least two recesses on the opposite side of the fin peak. The tube body has an inner surface;
The finned tube according to claim 8, wherein the finned tube includes a spiral protrusion protruding from an inner surface of the tube main body. A tube body having an outer surface;
At least one fin extending radially from an outer surface of the tube body, the fin having a side wall, a fin top, a fin base, and a fin height measured from the fin top to the fin base;
A plurality of fin peaks received at the top of the fin, the fin peaks having at least one stepped side surface, such that a plurality of fin drop portions are defined between the fin peaks;
A finned tube characterized by comprising:   The finned tube according to claim 13, wherein the stepped side surface of the fin peak has at least two stepped structures.   14. The finned tube according to claim 13, wherein the fin peak has two stepped side surfaces, and the stepped side surface is on the opposite side of the fin peak.   14. The finned tube according to claim 13, wherein the fin is formed from the tube body, whereby the fin is integrated with the tube body. The tube body has an inner surface;
The finned tube according to claim 13, wherein the finned tube further includes a protrusion extending from an inner surface of the tube main body. A method of manufacturing a finned tube comprising:
Providing a tube body;
Forming fins on the outer surface of the tube body;
Attaching a drop to the fin such that a fin peak is defined between the drops;
Press-fitting an eccentric depression into the fin peak such that the side surface of the fin peak has a stepped structure;
A method characterized by comprising.   19. The method of claim 18, further comprising forming a spiral protrusion on the inner surface of the tube body.   The method of claim 18, wherein an eccentric depression is press-fitted on the opposite side of the fin peak.   The method of claim 18, wherein the indentation has at least two stepped structures.

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