JP6718666B2 - Heat transfer tube for heat exchanger and heat exchanger using the same - Google Patents

Description

The present invention relates to a heat transfer tube for a heat exchanger and a heat exchanger using the same, and more particularly, to perform heat exchange between a first fluid flowing inside the tube and a second fluid flowing outside the tube. The present invention relates to a heat transfer tube for a heat exchanger, and a heat exchanger using the same. Among them, the present invention, the first fluid side flowing through the inside of the tube, the heat transfer tube for heat exchanger for further heat transfer promotion, and to improve the heat exchanger using the same, In particular, it can be advantageously applied to a heat exchanger for hot water supply in which the first fluid is water.

Conventionally, two heat transfer tubes, a first heat transfer tube that allows a first fluid to flow and a second heat transfer tube that causes a second fluid to flow, have been combined to produce a first fluid and a second fluid. Various heat exchangers configured to perform heat exchange between them have been used, and one of such heat exchangers is disclosed in Japanese Patent Laid-Open No. 2002-228370 (Patent Document 1). There is. There, in a form in which a refrigerant tube through which a refrigerant flows is spirally wound around the outer circumference of a core tube through which water flows, or a heat transfer joint is made by arranging the core tube and the refrigerant tube in parallel to the tube axis direction. The heat exchange between the water and the refrigerant is performed.

However, when a heat transfer tube used in such a conventional heat exchanger, in particular, a heat transfer tube for circulating water inside has a tube with a simple circular cross section and an inner surface that is smooth, a refrigerant or the like flowing outside thereof is used. There was a problem that the heat exchange performance with the fluid was insufficient.

Therefore, in such a heat exchanger, various measures have been conventionally made in order to improve the heat exchange efficiency. For example, in Japanese Unexamined Patent Application Publication No. 2009-270755 (Patent Document 2), a continuous spiral ridge is provided on the inner surface of the pipe in correspondence with the concave ridge that continuously extends spirally in the pipe axial direction on the outer pipe surface. At the same time, a heat transfer tube for a heat exchanger having a structure in which a plurality of projections are formed on the top of the ridge at predetermined intervals and with a predetermined size is proposed, and JP 2011-12909 A (Patent Document 3). In the case of (1), a protruding portion corresponding to a corrugated groove spirally formed on the outer peripheral surface of the pipe is spirally formed on the inner peripheral surface of the pipe, and a protrusion corresponding to a plurality of recesses provided adjacent to the corrugated groove. A heat transfer tube, which is formed on the inner peripheral surface of the tube, has been clarified.

However, even the heat transfer tubes for heat exchangers disclosed in Patent Documents 2 and 3 cannot be said to have sufficient heat exchange performance, and further improvement in heat exchange performance is required. .. Further, in FIG. 7 of Patent Document 2 and FIGS. 3 to 6 of Patent Document 3, a so-called double-tube heat exchanger different from the heat exchanger having the configuration shown in Patent Document 1 is disclosed. The same problem is inherent in the heat transfer tube used in such a double tube heat exchanger.

JP 2002-228370 A JP, 2009-270755, A JP, 2011-12909, A

Here, the present invention has been made in view of such circumstances, and the problem to be solved is that the heat exchange performance can be advantageously improved with a simple structure. Another object of the present invention is to provide a heat exchanger tube for a heat exchanger, and another object is to provide a heat exchanger excellent in heat exchange characteristics using such a heat exchanger tube for a heat exchanger.

Then, in the present invention, in order to solve such a problem, the inside of the pipe is made to be the first flow passage, and the first fluid is made to flow therethrough, and the second flow passage is provided outside the pipe. Is a heat transfer tube for a heat exchanger configured to perform heat exchange with a second fluid that is made to flow therethrough, and a plurality of V-shaped planar shapes are formed on the inner surface of the tube. The protrusions are formed independently of each other, and the plurality of protrusions are arranged such that their V-shapes are widened toward the upstream side of the flow of the first fluid. A heat transfer tube for a heat exchanger, which is characterized in that

According to one of the preferable modes of the heat exchanger tube for a heat exchanger according to the present invention, the plurality of V-shaped projections are independently arranged at a predetermined distance in the tube axis direction. In addition, the V-shaped angle of the protrusion is 30° to 140°.

Further, in the present invention, the heat exchanger tube for a heat exchanger described above is used, and it is accommodated in an outer tube having a diameter larger than that of the heat exchanger tube, and a first fluid is circulated inside the heat exchanger tube. A double-tube heat exchanger constituted by circulating a second fluid outside the heat transfer tube and performing heat exchange between the two fluids is also included in the gist of the present invention. is there.

Furthermore, in the present invention, a large-diameter pipe in which the inside of the pipe serves as a first flow passage, and the pipe is arranged in close contact with the outer peripheral surface of the large-diameter pipe, and the inside of the pipe serves as a second flow passage. In a heat exchanger composed of one or a plurality of small-diameter pipes having a smaller diameter than the large-diameter pipe, as the large-diameter pipe, a heat exchanger having a structure using the above-mentioned heat transfer pipe for heat exchanger, This is the summary.

Therefore, according to the heat transfer tube for a heat exchanger configured according to the present invention, a plurality of V-shaped projections that are expanded to the upstream side with respect to the flow of the first fluid are provided on the inner surface of the tube. By virtue of this, the first fluid such as water circulated in the pipe is effectively disturbed by the V-shaped protrusions provided on the inner surface of the pipe, and the heat transfer from the fluid to the heat transfer pipe is advantageous. Therefore, the heat exchange performance can be effectively improved.

In a heat exchanger in which the first fluid on the inner surface side of the heat transfer tube receives heat from the second fluid on the outer surface side, the disturbed first fluid is Although it will flow to the downstream side in the immediate vicinity, on the inner surface of the heat transfer tube on the downstream side, the temperature of the first fluid in contact with it will increase, so the heat exchange efficiency will be lower than on the upstream side. .. However, in the heat transfer tube according to the present invention, the first fluid whose temperature has risen is the V-shaped corner portion (downstream) along the projection from the upstream opening of the V-shaped projection provided on the inner surface of the tube. At the corner of the V-shape, the projections are crossed over and the flow is formed from the inner surface of the tube toward the central axis of the tube. At the same time, the first fluid (fresh fluid) having a lower temperature than the vicinity of the center of the pipe flows into the downstream side of the V-shaped corner portion, and heat exchange with the first fluid having a lower temperature causes the inside of the pipe on the downstream side to flow. Therefore, the heat exchange efficiency in the aspect can be improved. Further, the flow of the first fluid similar to the above is induced by another V-shaped projection provided on the downstream side thereof, and the longitudinal direction of the pipe (the flow of the first fluid from the upstream to the downstream). Direction), the heat exchange efficiency is improved.

Further, in the present invention, since the structure capable of obtaining such heat exchange performance improving effect is a simple structure, the pressure loss of the first fluid circulated in the pipe is effectively reduced. In addition to having the advantage that can be done, in the heat exchanger heat exchanger tube configured according to the present invention, by relatively simple processing such as rolling the outer peripheral surface of the tube, Since the desired V-shaped projection can be easily formed, it is possible to advantageously reduce the production cost of the heat transfer tube.

Further, in the heat exchanger using the heat transfer tube for a heat exchanger according to the present invention as described above, since the heat transfer efficiency of the heat transfer tube is high, the first fluid and the heat transfer tube that can be circulated inside the heat transfer tube It is possible to effectively improve the heat transfer with the second fluid that is made to flow through the flow path formed outside the heat exchanger, and it is possible to exhibit high heat exchange performance as a heat exchanger. It has features. Moreover, since such a heat transfer tube for a heat exchanger has a relatively simple structure and therefore can be manufactured at a low cost, the production cost of the heat exchanger can be advantageously reduced and its productivity can be improved. It also has a feature that can effectively increase the

It is explanatory drawing which shows an example of the heat exchanger tube for heat exchangers according to this invention, (a) is a partial explanatory view of the external appearance, (b) is explanatory drawing which shows the pipe outer surface side in the expansion view. Yes, (c) is an enlarged perspective partial explanatory view of the pipe inner surface showing one of the V-shaped projections formed on the inner surface of the pipe, and (d) is an enlarged explanatory view of the DD cross section in (b). And (e) is an enlarged explanatory view of the EE cross section in (b). It is a plane explanatory view about a V-shaped projection, and (a) and (b) show a different example, respectively. It is explanatory drawing which shows the different form of V-shaped projection according to this invention, (a) is a plane explanatory drawing which shows one of the modified examples of V-shaped projection, (b) is in (a). It is a BB sectional explanatory view, and (c) and (d) are expanded plane explanatory views showing other different forms of a V-shaped projection, respectively. It is explanatory drawing which clarifies about the cross-sectional shape of a V-shaped projection, (a) is a plane partial view which shows one free end side part of a V-shaped projection, (b) is in (a). It is an expanded sectional explanatory view showing an example of an AA sectional shape, and (c) is a sectional explanatory view equivalent to (b) which shows a cross-sectional shape where V-shaped projection differs. It is explanatory drawing which shows the arrangement|positioning form of a V-shaped projection, Comprising: (a), (b), and (c), a plurality of V-shaped projections differ in a pipe axial direction and/or a pipe peripheral direction, respectively. FIG. 3 is a development explanatory view showing an example arranged in FIG. It is sectional explanatory drawing which shows an example of the rolling processing apparatus which manufactures the heat exchanger tube for heat exchangers according to this invention in the cross-sectional form orthogonal to a pipe axis. It is explanatory drawing which shows the form in which V-shaped protrusion is formed, (a) is a longitudinal cross-section partial description which shows the processing form of V-shaped protrusion by the rolling tool in the rolling processing apparatus shown in FIG. It is a figure and (b) is explanatory drawing corresponding to (a) which shows the form which forms a V-shaped protrusion in a pipe axis direction. It is a partial explanatory view showing an example of a heat exchanger constituted by using a heat exchanger tube for a heat exchanger according to the present invention, in which (a) is a small diameter tube spirally wound around an outer peripheral surface of a large diameter tube and fixed. It is a partial cross section partial explanatory view which shows an example of the outer winding type heat exchanger of the structure which is made up, and (b) is a cross section partial explanatory diagram which shows an example of a double pipe type heat exchanger.

Hereinafter, in order to more specifically clarify the present invention, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows an embodiment of a heat exchanger tube for a heat exchanger according to the present invention. There, as is clear from (a) and (b), the heat transfer tube 10 has a plurality of recesses 12 (three in this case) having a V-shaped planar shape on the outer surface thereof in the axial direction of the tube. The pipes are arranged at a predetermined distance, so that, corresponding to such a V-shaped recess 12, the inner surface of the pipe is provided with V as shown in (c), (d) and (e). A plurality of (here, three) projections 14 having a V-shaped planar shape are provided independently of each other. The plurality of V-shaped projections 14 are directed toward the upstream side of the flow of the first fluid that is made to flow through the first flow path provided in the heat transfer tube 10, that is, in FIG. In (a), it is arranged so as to widen to the right, whereby the heat exchange efficiency can be effectively improved.

That is, in the heat transfer tube 10 having such V-shaped projections 14 provided on the inner surface thereof, the first fluid, which has a temperature increased and flows in the immediate vicinity of the inner surface of the tube, has the V formed on the inner surface of the tube. From the expanded upstream side opening of the V-shaped projection 14, the V-shaped projection 14 can be converged to the downstream V-shaped corner (base) along the V-shape, and the projection is formed at the V-shaped corner. The flow over 14 causes the flow from the inner surface of the pipe to the center side of the pipe. At the same time, the first fluid having a low temperature (fresh fluid) flows into the downstream side of the V-shaped corner portion of the V-shaped projection 14 from the center side of the pipe, whereby the first fluid having a low temperature is applied. The one fluid enhances the heat exchange efficiency on the inner surface of the pipe on the downstream side. Further, another V-shaped projection 14 provided on the downstream side thereof causes the same flow of the first fluid as described above, and thus, the longitudinal direction of the pipe, in other words, from the upstream to the downstream. In the flow direction of the one fluid, the effective improvement effect of the heat exchange efficiency is brought about.

The effect of improving the heat transfer efficiency due to the disturbance of the first fluid by the plurality of V-shaped protrusions 14 is that the outer diameter (D) is about 9.52 to 30 mm and the wall thickness (t) is 0.5. In the heat transfer tube 10 of about 1.0 mm, the length (l): 0.5 to 3.0 mm, the width (w): 0.5 to 2.0 mm, the height (h): 0.2 to 1. It is advantageous to arrange the V-shaped projections 14 having a size of 0 mm and an angle (α) of 30 to 140° at a pitch (p) in the tube axis direction of about 4 to 8 mm. .. In particular, by setting the angle (α) to 30° or more, it becomes possible to effectively receive the fluid in the V-shape. When water is used as the first fluid that can be circulated inside the heat transfer tube 10, the flow rate is generally set to about 0.5 to 2.0 L/min.

By the way, according to the present invention, the V-shaped projections 14 formed on the inner surface of the heat transfer tube 10 are generally bilaterally symmetrical with respect to the center line A, as shown in FIG. .. That is, the lengths l ₁ , l ₂ , widths w ₁ , w ₂ and heights h ₁ , h ₂ of the two right and left hypotenuse parts 14 a, 14 b constituting the V-shaped projection 14 are the same, respectively. In addition to the dimensions (l ₁ =l ₂ , w ₁ =w ₂ , h ₁ =h ₂ ), the angles α ₁ and α _{2 formed} by the left and right hypotenuse parts 14 a and 14 b with respect to the center line A are also: The angles are the same (α ₁ =α ₂ ).

However, the present invention is by no means limited to the V-shaped protrusion 14 having such a left-right symmetrical shape, and as shown in FIG. 2B, the V-shaped protrusion 14a, 14b is asymmetrical. It is also possible to use the projections 14. There, the angle α is expressed as the sum of the angles α ₁ and α _{2 formed} with respect to the center line A of the left and right hypotenuses (α=α ₁ +α ₂ ), and these α ₁ and α ₂ are respectively , The angle with respect to the center line A is greater than 0° and less than or equal to 70°, and in the lengths: l ₁ and l ₂ , the shorter length (here, l ₁ ) is , At least 0.5 mm or more, and the lower height of the hypotenuse parts 14a, 14b is at least 0.2 mm, and the width: w ₁ , w ₂ is at least 0.5 mm or more. Will be said. Regarding the two angles α ₁ and α ₂ , the smaller angle (here, α ₁ ) needs to be at least larger than 0° so that the fluid receives the V-shape, and the fluid is effective. In receiving, the V-shape is open to the upstream side with respect to the flow of the fluid, and in order to smoothly guide the fluid to the corner (base) side of the V-shape, the larger angle (here α ₂ ) is preferably 70° or less.

Further, the V-shaped projection 14 can be formed into various V-shaped plane shapes as shown in FIGS. 3(a) to 3(e). That is, in FIG. 3A, the height of the connecting portion of the two left and right hypotenuse portions 14a and 14b, which are the V-shaped corner portions (base portions), is lowered as shown in FIG. 3B. h ₁ '<h ₁ ), whereby the flow of the fluid guided and converged by the two right and left hypotenuses 14a and 14b is easily flowed over at the corners of the V-shape and easily flowed downstream. ing. Incidentally, such left and right sides of the inclined portion 14a, 14b connection portion of the height of: when h ₁ 'is too low, from where the effective flow from the tube surface of the first fluid into the tube center direction is not easily caused , H ₁ ′ is preferably 0.2 mm or more. Further, in FIG. 3(c), the V-shaped corners of the V-shaped projection 14 are curved, and in FIG. 3(d), such V-shaped corners are Instead of the bent portion, in the curved shape, the left and right hypotenuse portions 14a and 14b are connected to each other to have a V-shape as a whole.

Further, even in the lateral cross-sectional shape of the left and right hypotenuse parts 14a and 14b forming the V-shaped projection 14, in addition to the angular shape as shown in FIG. 1 and the rounded shape as shown in FIG. It is also possible to do so. That is, an arc-shaped cross-sectional shape as shown in FIG. 4(b) or a trapezoidal-shaped corner portion as a curved cross-sectional shape as shown in FIG. 4(c) is also possible. is there.

Furthermore, regarding the arrangement of the plurality of V-shaped projections 14 formed on the inner surface of the heat transfer tube 10 according to the present invention, as shown in FIG. 1, they are arranged independently in one row in the tube axis direction. In addition to the above case, various arrangements as shown in FIGS. 5A to 5C are possible. Specifically, in the example shown in FIG. 5A, a plurality of V-shaped projections 14 arranged at a predetermined pitch (pitch): p in the tube axis direction are arranged in the tube circumferential direction. They are arranged with a predetermined deviation: x. In this case, x/p is preferably 0.3 or less in order to continuously obtain good heat exchange characteristics without disturbing the fluid flow. Further, in the example shown in FIG. 5B, a row of a plurality of V-shaped protrusions 14 arranged at a predetermined pitch in the tube axis direction has a space of d in the tube circumferential direction and V-shaped projections. It is provided in a plurality of rows with a distance y between the tips of the oblique sides. Then, in that case, it is desirable that the distance y between the tip ends of the hypotenuses of the V-shaped projections 14 is 0.3 mm or more, which improves the flow of fluid between the V-shaped portions. Good heat exchange characteristics can be obtained. Further, in the example shown in FIG. 5C, a plurality of rows of V-shaped projections 14 are arranged in the pipe circumferential direction, and the V-shaped projections 14 of adjacent rows are displaced in the tube axial direction by: It is configured in such a form that it is provided with e.

By the way, the heat transfer tube 10 according to the present invention configured as described above is manufactured by a known rolling method, for example, by using a rolling apparatus 20 as shown in FIG. 6 as described below. The Rukoto.

That is, the rolling device 20 includes one of the projection rolling tools 22 in which the V-shaped projection forming disks 26 each having the V-shaped processed portions 27 provided on the outer peripheral surface thereof at predetermined intervals are attached to the rotary drive shaft 24. As shown in FIG. 6, one of the holding tools 30 has a rotary drive shaft 24 and a tube holding disk 28 having a flat outer peripheral surface serving as a contact surface. Is arranged and arranged with a phase difference of about 120° around the tube 32 sized to give In addition, each of the rotary shafts 24 has a lead angle (spiral angle) of a recess (V-shaped recess 12) formed so as to be positioned spirally on the surface of the heat transfer tube 10 with respect to the tube axis of the raw tube 32. : Β), respectively.

Then, the V-shaped projection forming disk 26 of the projection rolling tool 22 is rotated with respect to the outer surface of the raw pipe 32 while the raw pipe 32 is fed at a constant speed by the rolling processing device 20. By pressing them while making them, the hollow (V-shaped recess 12) corresponding to the V-shaped processed portion 27 on the outer peripheral surface of the V-shaped projection forming disk 26 is formed on the outer surface of the raw tube 32. Of. The outer peripheral surfaces of the tube holding disks 28, 28 of the two holding tools 30, 30 have a phase difference of 120° with respect to the contact position of the V-shaped projection forming disk 26 with the base tube 32 (see FIG. 6). Since it is adapted to be brought into contact with the outer peripheral surface of the raw pipe 32 and to be rotated by the rotary drive shafts 24, 24, the pressing force by the V-shaped projection forming disk 26 is The pipes 28, 28 are effectively received by the pipe holding disks 28, 28 so that the straight running of the raw pipe 32 can be advantageously ensured.

Further, in this manner, a plurality of predetermined depressions (V-shaped recesses 12) are formed in a spiral shape on the outer peripheral surface of the raw pipe 32 by rolling, independently of each other. , V-shaped projections (14: see FIG. 1, etc.) corresponding to the recesses (V-shaped recesses 12) are formed on the inner peripheral surface of the raw pipe 32 in a spiral shape. As a result, the heat transfer tube 10 that is the object of the present invention can be obtained.

The rolling apparatus 20 shown in FIG. 6 is for forming a hollow (V-shaped recess 12) in the raw pipe 32 in a spiral shape as shown in FIG. 7A. If such a rolling process is carried out in a direction parallel to the axial direction of the raw pipe 32 as shown in FIG. 7B, the V-shaped projection shown in FIG. 1 or FIG. It is also possible to easily form the 14 in the axial direction of the tube. In that case, the V-shaped projection forming disk 26 is relatively pressed and moved with respect to the outer peripheral surface of the raw tube 32 in a direction parallel to the tube axis direction.

As described above, the heat transfer tube 10 having the structure according to the present invention is produced by a relatively simple process such as rolling the outer peripheral surface of the tube having a smooth inner and outer peripheral surface. In addition to the excellent heat exchange performance, the production cost of the heat transfer tube 10 can be advantageously reduced.

By the way, in the present invention, a heat exchanger for exchanging heat between two fluids using the heat transfer tube 10 as described above is also an object of the present invention. The heat exchanger as shown in a) or (b) can be mentioned.

Specifically, the heat exchanger 40 shown in FIG. 8A is arranged in close contact with the large-diameter pipe 42 whose inside is the first flow path and the outer peripheral surface of the large-diameter pipe 42. An outer-winding type heat exchanger comprising one or a plurality of small-diameter pipes 44 having a smaller diameter than the large-diameter pipe 42, in which the inside of the pipe serves as a second flow passage. As 42, the heat transfer tube 10 according to the present invention is used. Then, low-temperature water is circulated as the first fluid in the large-diameter pipe 42 (heat transfer pipe 10), while high-temperature refrigerant is circulated as the second fluid in the small-diameter pipe 44. Heat is exchanged between the low temperature water and the high temperature refrigerant. Here, the small diameter pipe 44 is spirally wound around the large diameter pipe 42 with a predetermined pitch: p0, and the large diameter pipe 42 and the small diameter pipe 44 are joined by brazing or the like. They are closely arranged by being joined according to the method.

Further, the heat exchanger 50 shown in FIG. 8(b) is a double-tube heat exchanger including a large-diameter outer pipe 52 and a small-diameter inner pipe 54 accommodated coaxially in the pipe. The heat transfer tube 10 according to the present invention is used for the inner tube 54, and the inside of the tube serves as a first flow path, while a predetermined space is provided between the inner tube 54 and the outer tube 52. The second flow path is formed. Then, here, by narrowing both ends of the outer pipe 52 arranged coaxially with the inner pipe 54 so as to reduce the diameter, the ends of the outer pipe 52 are brought into close contact with the outer peripheral surface of the inner pipe 54, and A sealed second flow path is formed in the gap between the outer peripheral surface of the inner pipe 54 and the inner peripheral surface of the outer pipe 52, and a water inlet (Fig. On the other hand, by forming a water outlet 56 near the other end, a fluid such as low-temperature water introduced from the water inlet is made to flow through the second flow path, while the inner pipe is formed. By circulating high-temperature water in 54, heat exchange between the low-temperature water and the high-temperature water is performed.

Although the representative embodiments of the present invention have been described above in detail, the embodiments are merely examples, and the present invention is not limited to the specific description according to the embodiments. It should be understood that it should not be construed.

The present invention can be carried out in various modifications, modifications, improvements, and the like based on the knowledge of those skilled in the art, and such an embodiment does not depart from the spirit of the present invention. Needless to say, all of them belong to the category of the present invention.

Hereinafter, representative examples of the present invention will be shown to further clarify the characteristics of the present invention, but the present invention is subject to any restrictions due to the description of such examples. Not to mention that.

First, in order to form the heat transfer tube (10) having the structure according to the present invention, phosphorus deoxidized copper (JIS-H-3300-C1220) having an outer diameter (D) of 10 mm and a wall thickness (t) of 0.7 mm. A circular smooth tube (32) having a simple cross section was prepared. Then, as shown in FIG. 7(b), the V-shaped projection forming disk (26) is pressed against the prepared smooth tube (32), and the V-shaped projection forming disk (26) is relatively moved in the axial direction. The plurality of V-shaped protrusions (14) independent from each other are formed on the inner surface of the smooth tube (32) in parallel with the tube axis and in a row at a pitch (p) of 6.0 mm. In, it was rolled. The size of the formed V-shaped projection (14) is 2.0 mm in length (l ₁ =l ₂ ), and width (w ₁ =w) in the bilaterally symmetrical form as shown in FIG. 2A. ₂ ): 1.0 mm, height (h ₁ =h ₂ ):0.8 mm, angle (α ₁ =α ₂ ):45° (α=α ₁ +α ₂ =90°).

The heat transfer tube (10) thus obtained was used as a large-diameter tube (42) in FIG. 8(a), and its outer peripheral surface was covered with phosphorus deoxidized with an outer diameter of 6 mm and a wall thickness of 0.7 mm. Two small circular tubes (44) made of copper (JIS-H-3300-C1220) with a simple cross section are wound at a winding pitch (p ₀ ) of 6.0 mm and fixed by brazing. An outer wound heat exchanger (40) was created.

Then, using the obtained outer-winding heat exchanger (40), low-temperature water of 17° C. is circulated at a flow rate of 1.7 L/min in the large-diameter heat transfer tube (10), The small-diameter small-diameter pipe (44) is supplied with a carbon dioxide refrigerant at 80° C. at a flow rate of 11 L/min per pipe, which is opposed to the flow of the low-temperature water, so that the low-temperature water is removed. Heat exchange was performed with the carbon dioxide refrigerant, and the heat exchange performance was evaluated. The heat exchange performance is evaluated by measuring the temperature of water in the large diameter pipe (10) at 17°C when the temperature of the carbon dioxide refrigerant flowing in the small diameter pipe (44) changes from 80°C to 20°C. The heat exchange performance was determined by measuring the heat quantity from the temperature difference and the heat capacity.

On the other hand, as a comparative example, the large-diameter pipe (42) has the same outer diameter, wall thickness, and material as those of the heat transfer pipe (10) described above, and has a smooth inner surface without the V-shaped projection (14) provided on the inner surface. An outer-wound heat exchanger (40) as shown in FIG. 8(a) was manufactured using the tube, and the same heat exchange performance as above was evaluated. The conditions such as the flow rates of the refrigerant and water are the same as those in the above-described evaluation of the heat exchange performance.

As a result, in such a comparative example, when the heat exchange performance when the inner surface smooth tube was used as the large diameter tube (42) of the outer wound heat exchanger was 100, the V-shaped protrusion was formed on the inner surface of the tube according to the present invention. The heat exchange performance of the outer-wound heat exchanger using the heat transfer tube (10) having (14) formed was 108. From this, it was possible to confirm that the V-shaped projections (14) provided on the inner surface of the heat transfer tube (10) could realize an effective improvement effect of the heat exchange performance.

10 Heat Transfer Tube 12 Recess 14 Protrusion 14a, 14b Oblique Side 20 Roll Forming Machine 22 Protrusion Rolling Tool 24 Rotation Drive Shaft 26 V-Shaped Protrusion Forming Disk 27 V-Shaped Section 28 Pipe Holding Disk 30 Holding Tool 32 Base pipe 40 Heat exchanger 42 Large diameter pipe 44 Small diameter pipe 50 Heat exchanger 52 Outer pipe 54 Inner pipe 56 Water outlet

Claims (6)

The inside of the pipe is the first flow path, between the first fluid that is made to flow therethrough, and the second flow path is formed outside the pipe, and between the second fluid that is made to flow therethrough, A heat transfer tube for a heat exchanger configured to perform heat exchange,
On the inner surface of the pipe, a plurality of protrusions having a V-shaped planar shape are formed independently of each other at a pitch of 4 to 8 mm in the pipe axis direction, and the V-shaped protrusions are V-shaped. The left and right hypotenuses, which are the corners of the letter, are formed such that the heights of the connecting parts are lower than the heights of the hypotenuses and are 0.2 mm or more. The protrusions are arranged so that their V-shapes are widened toward the upstream side of the flow of the first fluid, while the outer surface of the pipe has a V-shape corresponding to the protrusions. A heat transfer tube for a heat exchanger, wherein a plurality of recesses are formed independently of each other. The heat transfer tube for a heat exchanger according to claim 1, wherein an angle forming the V-shape of the protrusion is 30° to 140°. The plurality of V-shaped projections are positioned at a predetermined interval in the tube circumferential direction, and the distance between the tip ends of the hypotenuses of the adjacent V-shaped projections in the tube circumferential direction is 0.3 mm or more. The heat transfer tube for a heat exchanger according to claim 1 or 2, which is provided. A heat transfer tube having an outer diameter of 9.52 to 30 mm and a wall thickness of 0.5 to 1.0 mm, wherein the V-shaped projections have a length of two right and left hypotenuses forming the V-shape. Thickness: 0.5 to 3.0 mm, width of the hypotenuse portion: 0.5 to 2.0 mm, and height of the hypotenuse portion: 0.2 to 1.0 mm. Item 6. A heat transfer tube for a heat exchanger according to any one of items 3 . In a double-tube heat exchanger composed of an outer tube and an inner tube housed in the tube, the heat transfer tube according to any one of claims 1 to 4 is used as the inner tube. A double-tube heat exchanger characterized by the above. A large-diameter pipe whose inside is a first flow path, and a large-diameter pipe that is disposed in close contact with the outer peripheral surface of the large-diameter pipe and has a second flow path inside the pipe, which has a smaller diameter than the large-diameter pipe. A heat exchanger comprising one or a plurality of small-diameter pipes, wherein the heat transfer pipe according to any one of claims 1 to 4 is used as the large-diameter pipe. Exchanger.

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