JP2017067362A - Heat transfer pipe, manufacturing method thereof, and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress temperature reduction in a radial direction of a fin of a heat transfer pipe, to thereby accelerate heat transfer from a heat source side fluid to a heat reception side fluid.SOLUTION: A heat transfer pipe 10 is arranged in a heat source side fluid 15 and transmits heat to a heat reception side fluid 16. The heat transfer pipe 10 includes a main pipe 11 inside which the heat reception fluid 16 circulates, and a fin 12 attached to an external surface of the main pipe 11 in a contact manner and extending outward from a contact part of the main pipe 11. The fine 12 includes a fin base material part 30, and a microcavity layer 31. The microcavity layer 31 comprises high emissivity material with higher emissivity than that of the fin base material part 30, and is provided with many cavities 32 configured to resonate electromagnetic waves having a heat radiation wavelength.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a heat transfer tube, a manufacturing method thereof, and a heat exchanger using the heat transfer tube.

  Heat transfer tubes with fins attached to the outer surface of the mother tube are widely known.

  For example, heat is transferred from the heat source side fluid to the heat receiving side fluid by flowing the heat source side fluid (high temperature side fluid) outside the heat transfer tube and flowing the heat receiving side fluid (low temperature side fluid) inside the mother tube. .

  FIG. 10 is a partial longitudinal sectional view schematically showing a conventional heat transfer tube 10. FIG. 11 is a diagram schematically showing a temperature distribution in the radial direction inside and outside the conventional heat transfer tube 10.

  As shown in FIG. 10, the mother pipe 11 is a metal circular pipe, for example, and fins 12 are attached to the outer surface of the mother pipe 11. The fins 12 are formed in an annular shape, and the roots 13 of the fins 12 are welded to the outer surface of the mother pipe 11 by, for example, all-around welding. The fin 12 extends from the root 13 to the tip 14 along a plane perpendicular to the axial direction (vertical direction in FIG. 10) of the mother pipe 11.

  A large number of fins 12 are usually arranged side by side at a predetermined interval in the axial direction of the mother pipe 11. The heat source side fluid 15 is caused to flow outside the heat transfer tube 10, and the heat receiving side fluid 16 is caused to flow inside the mother tube 11.

  At this time, when the radial direction temperature part distribution of the heat transfer tube 10 is schematically shown, a curve X in FIG. 11 is obtained. A heat source side fluid 15 having a temperature (bulk temperature) Ta flows outside the tip 14 of the fin 12. In addition, a heat receiving side fluid 16 having a temperature (bulk temperature) Te flows in the mother pipe 11. The temperature Ta of the heat source side fluid 15 is higher than the temperature Te of the heat receiving side fluid 16, and heat moves from the heat source side fluid 15 toward the heat receiving side fluid 16.

  11, the temperature Ta of the heat source side fluid 15 includes the temperature Tb of the tip 14 of the fin 12, the temperature Tc of the root 13 of the fin 12, the inner surface temperature Td of the mother pipe 11, and the heat receiving side fluid 16. The temperature decreases sequentially through the order of the temperature Te.

  At this time, since the distance between the fins 12 is narrow, the heat source side fluid 15 does not sufficiently enter the roots 13 of the fins 12 and is affected by the thermal conductivity of the material used for the fins 12. The heat source side fluid 15 at the fluid temperature Ta becomes the temperature Tb by convective heat transfer with the tip 14 of the fin 12. The root 13 of the fin 12 is lowered to the temperature Tc by heat conduction from the tip 14 of the fin 12 to the root 13 and convective heat transfer on the surface of the fin 12. The heat receiving side fluid 16 receives heat by the temperature difference between the temperature Td further decreased by the heat conduction in the thickness direction of the mother pipe 11 and the temperature Te of the heat receiving side fluid 16 and heat transfer of convection and boiling. In order to suppress this temperature drop, generally, the base 13 of the fin 12 and the mother pipe 11 are joined by the entire circumference welding of the mother pipe 11 in the circumferential direction to suppress the contact thermal resistance.

JP 2004-92931 A

  By the way, the temperature difference between the temperature Td of the inner surface of the mother pipe 11 and the temperature Te of the heat receiving side fluid 16 has a correlation with the heat transfer amount received by the heat receiving side fluid 16. For example, if the fin 12 is formed long, the temperature Tc of the root 13 of the fin 12 is lowered, and accordingly, the temperature difference between the temperature Td of the inner surface of the mother pipe 11 and the temperature Te of the heat receiving side fluid 16 becomes small. The amount of heat transfer received by the side fluid 16 is limited to an increase in the amount of heat transfer that is smaller than the effect of expanding the heat transfer area by forming the fins 12 long. Therefore, in order to suppress the temperature drop in the length direction of the fins 12, the fins 12 have not been able to be made sufficiently long until now.

  An object of an embodiment of the present invention is to solve the above-described problem, and suppresses a temperature decrease in the radial direction of the fin in a heat transfer tube disposed in a high-temperature heat-source-side fluid so that the heat-source-side fluid The object is to promote the transfer of heat to the low temperature heat receiving fluid in the tube.

  In order to solve the above problems, a heat transfer tube according to the present embodiment is a heat transfer tube that is disposed in a heat source side fluid and transfers heat to a heat receiving side fluid that is lower in temperature than the heat source side fluid, and the heat receiving tube A main pipe through which a side fluid circulates, and a fin extending in a radial direction of the main pipe from a root attached in contact with an outer surface of the main pipe, the fin being a fin base portion And a high emissivity material having a higher heat emissivity than the fin base part, coated on at least the surface of the fin base part extending in the radial direction of the mother pipe, and resonating electromagnetic waves having a heat radiation wavelength. And a microcavity layer provided with a large number of cavities.

  The heat transfer tube according to the present embodiment is a heat transfer tube that is disposed in the heat source side fluid and transfers heat to the heat receiving side fluid that is lower in temperature than the heat source side fluid, and the heat receiving side fluid circulates inside the heat transfer tube. And a fin extending from the base attached in contact with the outer surface of the mother pipe toward the radially outer side of the mother pipe. The fin includes a fin base portion and a fin base portion. Is made of a high emissivity material having a high heat emissivity, coated at least on the surface of the fin base portion extending in the radial direction of the mother pipe, and formed entirely in a sawtooth shape and facing the mother pipe side. And a sawtooth-shaped layer having a surface formed on an inclined surface.

  The heat exchanger according to this embodiment includes the heat transfer tube of the above embodiment.

  The method of manufacturing a heat transfer tube according to the present embodiment includes a mother pipe, a fin base part extending toward the radially outer side of the mother pipe, and a high emissivity material having a higher heat emissivity than the fin base part. A method of manufacturing a heat transfer tube, comprising: a microcavity layer that covers a surface of the fin base portion and the mother pipe and includes a plurality of cavities that resonate electromagnetic waves having a heat radiation wavelength. A welding step of fixing the fin base portion to the mother pipe by whole circumference fillet welding to the outer peripheral surface of the mother pipe, and after the welding step, at least the fin base portion of the mother pipe A microcavity layer forming step of forming the microcavity layer by coating a surface extending in a radial direction and a surface of the mother pipe with a high emissivity material having a higher emissivity of heat than the fin base portion; Have The features.

  According to the embodiment of the present invention, heat transfer from the heat source side fluid to the low temperature heat receiving side fluid in the mother pipe is promoted.

1 is an external view schematically showing a heat exchanger according to a first embodiment. It is a fragmentary longitudinal cross-sectional view which shows typically the heat exchanger tube which concerns on 1st Embodiment. FIG. 3 is a partially enlarged longitudinal sectional view showing an enlarged part of the heat transfer tube of FIG. 2. It is a fragmentary perspective view which shows typically the heat flow in the heat exchanger tube of FIG. 2 by a one-dimensional model. It is a fragmentary longitudinal cross-sectional view which shows typically the heat exchanger tube which concerns on 2nd Embodiment. It is explanatory drawing which shows typically the radiation direction of the electromagnetic waves in the fin of the heat exchanger tube of a comparative example. It is explanatory drawing which shows typically the radiation direction of the electromagnetic wave in the fin of the heat exchanger tube which concerns on 2nd Embodiment. It is a fragmentary longitudinal cross-sectional view which shows typically the heat exchanger tube which concerns on 3rd Embodiment. It is explanatory drawing which shows typically the effect | action of the fin of the heat exchanger tube which concerns on 3rd Embodiment. It is a fragmentary longitudinal cross-sectional view which shows the conventional heat exchanger tube typically. It is a figure which shows typically the radial direction temperature distribution inside and outside the conventional heat exchanger tube.

  Hereinafter, a heat transfer tube, a manufacturing method thereof, and a heat exchanger according to the present embodiment will be described with reference to the drawings. Here, parts that are the same as or similar to those in the prior art are given the same reference numerals, and redundant descriptions are omitted.

[First Embodiment]
FIG. 1 is an external view schematically showing a heat exchanger according to the first embodiment. FIG. 2 is a partial longitudinal sectional view schematically showing the heat transfer tube according to the first embodiment.

  As shown in FIG. 1, the heat exchanger 20 according to the first embodiment is disposed in the high-temperature heat source side fluid 15 and communicates the inlet header 21, the outlet header 22, the inlet header 21, and the outlet header 22. And a plurality of heat transfer tubes 10. The plurality of heat transfer tubes 10 are arranged in parallel to each other. The inlet header 21 is provided with a heat receiving side fluid inlet 23 for supplying the low temperature heat receiving side fluid 16. The outlet header 22 is provided with a heat receiving side fluid outlet portion 24 for discharging the heat receiving side fluid 16.

  Each heat transfer tube 10 includes one mother pipe 11 and a large number of fins 12 attached to the outer surface of the mother pipe 11. The mother pipe 11 is a circular pipe made of a metal having a high thermal conductivity, for example. The fin 12 has a disk shape with a circular opening formed in the center, that is, an annular shape, and is made of a metal having high thermal conductivity. As shown in FIG. 2, the fin 12 extends from the root 13 to the tip 14 along a plane perpendicular to the axial direction of the mother pipe 11. A large number of fins 12 are arranged in the axial direction of the mother pipe 11 at a predetermined interval.

  The root 13 of the fin 12 is welded to the outer surface of the mother pipe 11. The welded portion between the fin 12 and the mother pipe 11 is formed by, for example, full circumference fillet welding between the root 13 of the fin 12 and the outer surface of the mother pipe 11. Thereby, heat is transmitted from the fin 12 to the mother pipe 11 by heat conduction.

  As shown in FIG. 2, the fin 12 of the present embodiment includes a fin base portion 30 responsible for mechanical strength, and a microcavity layer 31 that covers both surfaces of the fin base portion 30 and the outer surface of the mother pipe 11. Have. The microcavity layer 31 is made of a high emissivity material having a heat radiation (radiation) rate higher than that of at least the fin base portion 30. The microcavity layer 31 is formed by printing a resin material in which ceramics or carbon is dispersed or by photolithography.

  The microcavity layer 31 has a periodic fine structure of the order of the heat radiation wavelength (several μm to several tens μm) on the surface of the fin base portion 30 of the fin 12. That is, the microcavity layer 31 is formed with a large number of cavities 32 having a rectangular cross section on both surfaces of the fin base portion 30 and the outer surface of the mother pipe 11. As shown in FIG. 3, the microcavity layer 31 is formed with opposing walls 32 a that are parallel to each other and face each other in a large number of cavities 32.

  As the heat receiving side fluid 16, for example, a gas such as water vapor or a mixed gas, or a liquid such as water, oil, or chlorofluorocarbon can be used. The heat source side fluid 15 has a higher temperature than the heat receiving side fluid 16, and for example, a gas such as water vapor or a mixed gas, or a liquid such as water, oil, or chlorofluorocarbon can be used.

  Next, the operation of the first embodiment will be described.

  As shown in FIG. 1, the heat receiving side fluid 16 flows into the inlet header 21 from the heat receiving side fluid inlet 23, and branches and flows from the inlet header 21 into the mother pipe 11 of the plurality of heat transfer tubes 10. At this time, heat is transferred from the heat source side fluid 15 flowing outside the heat transfer tube 10 to the heat receiving side fluid 16 in the heat transfer tube 10. Here, the heat receiving side fluid 16 that has received the heat flows out from the heat receiving side fluid outlet portion 24 through the outlet header 22.

  FIG. 4 is a partial perspective view schematically showing a heat flow in the heat transfer tube of FIG. 2 by a one-dimensional model. The concept of heat balance in this model is shown below. The heat of the heat source side fluid 15 ventilated outside the heat transfer tube 10 is transferred to the fins 12 of the heat transfer tube 10. Part of the heat is transferred to the mother pipe 11 by heat conduction from the tip 14 of the fin 12 to the root 13 (joint portion between the fin 12 and the mother pipe 11), and the other is radiated from the fin 12 to the outer surface of the mother pipe 11. Heat is transferred by. Heat is transferred from the outer surface of the mother pipe 11 to the inner surface by heat conduction in the solid wall, and is transferred from the inner surface of the mother pipe 11 to the heat receiving side fluid 16 in the mother pipe 11 by boiling or convection. However, since the wall thickness of the mother pipe is smaller than the length of the fin, the thickness of the pipe wall of the mother pipe 11 is ignored, and the temperature inside and outside the pipe wall of the mother pipe 11 is assumed to be equal. .

(1) Amount of heat transfer by convection from the hot gas (heat source side fluid) 15 to the fin tip 14 [W]: Qconv2, Qconv3
Qconv2 = Qconv3 = hf × Af × (Tg−Tt)
However,
hf: forced convection heat transfer coefficient at the tip of the fin [W / m ² K],
Af: Fin tip area (1/2 of fin cross-sectional area) = df × (1/2) × Yf [m ² ],
Tg: high temperature gas temperature [° C.]
Tt: fin tip temperature [° C.]
df: fin thickness [m],
Yf: width of mother pipe and fin [m]
(2) Heat transfer amount [W] by heat conduction from the fin tip 14 to the fin root 13: Qcond2, Qcond3
Qcond2 = Qcond3 = λf × Af / Xf × (Tt−Tw)
However,
λf: thermal conductivity of the fin [W / mK],
Xf: fin length [m],
Tw: Tube wall temperature [° C]
(3) Heat transfer amount [W] by radiation (radiation) between opposing fins 12: Qrad1
It is assumed that the fins 12 facing each other in the direction perpendicular to the surface of the fin 12 are isothermal, and heat transfer by radiation is not performed.

(4) Heat transfer amount [W] by radiation from the fin 12 to the pipe wall of the mother pipe 11: Qrad2, Qrad3
Qrad2 = Qrad3 = σ × εf × F × Arad × (Tt + 273.15) ⁴ − (Tw + 273.15) ⁴ ) × K
However,
σ: Stefan-Boltzmann constant [W / m ² K ⁴ ],
εf: fin emissivity [−],
F: form factor from fin to tube wall = 1 (radiation from fin to tube wall is closed space),
Arad: Radiation heat transfer area of fin = Xf × Yf [m ² ],
K: Reduction coefficient of heat transfer due to fin temperature distribution (5) Heat transfer due to boiling from wall of mother pipe 11 to water in pipe [W]: Qb
Qb = hb × Ab × (Tw−Tsat)
However,
hb: boiling or convective heat transfer coefficient [W / m ² K],
Ab: Boiling or convection heat transfer area = (dp + df × (1/2) × 2) × Yf [m ² ],
Tsat: saturation temperature of water in the tube [° C.]
(6) Heat balance Qconv2 + Qconv3
= Qcond2 + Qcond3 + Qrad2 + Qrad3 = Qb

  In the heat transfer path from the fin tip 14 to the mother pipe 11, the fins have low emissivity, Qrad2 and Qrad3 occupying the entire heat transfer amount are small, and Qcond2 and Qcond3 occupy many. Here, if the emissivity εf of the fins is improved and the heat transfer amounts of Qrad2 and Qrad3 are increased, the tube wall temperature can be increased, and the temperature difference between the mother pipe 11 and the heat receiving side fluid 16 can be expanded.

  As described above, according to the present embodiment, the microcavity layers 31 are formed on both surfaces of the fin base portion 30 of the fin 12 and the outer surface of the mother tube 11. Resonance of the electromagnetic wave having the heat radiation wavelength occurs by the opposing wall 32a facing each other, and the wavelength in the infrared region can be mainly used as compared with the wavelength in the ultraviolet region. Therefore, a high emissivity can be obtained compared to the simple smooth fin 12 shown in FIG. 10 in which the microcavity layer 31 is not formed. Therefore, the amount of heat transfer (Qrad2 and Qrad3) due to radiation from the fins 12 to the mother pipe 11 increases, and the temperature of the mother pipe 11 rises. Thereby, the heat transfer amount received by the heat receiving side fluid 16 can be increased.

  In particular, since the microcavity layer 31 is formed on the surface of the fin 12, the emissivity is improved as compared with a smooth fin. As a result, when heat is transferred from the heat source side fluid 15 to the heat receiving side fluid 16, the amount of heat transfer (Qrad2 and Qrad3) due to radiation from the fins 12 to the mother pipe 11 increases and the temperature of the mother pipe 11 rises. The amount of heat transfer received by the heat receiving side fluid 16 can be increased.

  In this embodiment, the shape of the cavity 32 for resonating electromagnetic waves is formed in a rectangular cross section as described above. However, the shape is not limited to this, and may be a curved curve shape. Even when formed in this way, in the cavity 32, in order to resonate electromagnetic waves, it is necessary to have opposing walls 32a facing each other at least partially.

  Further, the cavity 32 may be a groove having a circular or square planar shape, or may be formed in a concentric shape in the form of a large number of grooves. Furthermore, although the microcavity layer 31 is formed on the outer surfaces of the fin base portion 30 and the mother pipe 11, the microcavity layer 31 may be formed at least on the fin base portion 30.

  Furthermore, when a black oxide film is used as the microcavity layer 31, the emissivity is improved by coloring it black.

[Second Embodiment]
FIG. 5 is a partial longitudinal sectional view schematically showing a heat transfer tube according to the second embodiment. FIG. 6 is an explanatory view schematically showing the radiation direction of electromagnetic waves in the fins of the heat transfer tube of the comparative example. FIG. 7 is an explanatory view schematically showing the radiation direction of electromagnetic waves in the fins of the heat transfer tube according to the second embodiment.

  Note that this embodiment is a modification of the first embodiment, and the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 5, the fin 12 of the present embodiment includes a fin base portion 30 responsible for mechanical strength, and a sawtooth layer 33 covering both surfaces of the fin base portion 30 and the outer surface of the mother pipe 11. Have.

  The saw-tooth shaped layer 33 is formed with a large number of saw-tooth shaped irregularities, and as shown in FIG. 7, an inclined surface 34a inclined so as to become gradually lower toward the mother tube 11 side, and the inclined surface 34a are continuously formed. A vertical surface 34 b formed perpendicular to the fin base material portion 30, and a parallel surface 34 c formed between the vertical surface 34 b and the inclined surface 34 a and formed parallel to the fin base material portion 30. Have The inclined surface 34a has a larger area than the vertical surface 34b and the parallel surface 34c.

  The sawtooth-shaped layer 33 is made of a high emissivity material having a heat radiation (radiation) rate higher than that of at least the fin base portion 30. The sawtooth layer 33 is formed by printing a resin material in which ceramics or carbon is dispersed or by photolithography.

  In the present embodiment, as shown in FIG. 1, a high emissivity heat transfer tube 10 covered with a sawtooth-shaped layer 33, a heat receiving side fluid inlet portion 23, an inlet header 21, an outlet header 22, and a heat receiving side fluid outlet portion. 24 constitutes the heat exchanger 20.

  Next, the operation of the second embodiment will be described.

  Compared to a horizontal smooth surface only with the fin base portion 30 shown in FIG. 6, the surface of the sawtooth-shaped layer 33 formed as in the present embodiment has the intensity of electromagnetic waves radiated from the inclined surface 34a shown in FIG. Emissivity). Therefore, the amount of radiant heat transfer from the fins 12 toward the mother pipe 11 can be increased. Here, in FIG.6 and FIG.7, it has shown that emissivity is so high that the line of an arrow is thick.

  As described above, according to the present embodiment, when heat is transferred from the high-temperature heat source side fluid 15 to the heat-receiving side fluid 16 through the high-emissivity heat transfer tube 10 covered with the sawtooth-shaped layer 33, the high emissivity fins 12 are used. The amount of heat transfer (Qrad2 and Qrad3) due to radiation from to the mother pipe 11 increases, and the temperature of the mother pipe 11 rises. Thereby, the heat transfer amount received by the heat receiving side fluid 16 can be increased.

  In addition, although the sawtooth-shaped layer 33 of this embodiment formed the vertical surface 34b continuously with the inclined surface 34a, you may make it form not only this but the vertical surface 34b in an inclined surface. In this case, in order to increase the amount of radiant heat transfer from the fin 12 toward the mother pipe 11, it is necessary to relatively reduce the angle of the inclined surface 34a.

[Third Embodiment]
FIG. 8 is a partial longitudinal sectional view schematically showing a heat transfer tube according to the third embodiment. FIG. 9 is an explanatory view schematically showing the action of the fins of the heat transfer tube according to the third embodiment.

  Note that this embodiment is a modification of the first embodiment, and the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 8, each heat transfer tube 10 of the present embodiment includes a single mother pipe 11 and a large number of fins 17 attached to the outer surface of the mother pipe 11. The fin 17 has a disk shape with a circular opening at the center, that is, an annular shape, and is made of a metal having high thermal conductivity. The fin 17 extends from the root 13 to the tip 14 along a plane perpendicular to the axial direction of the mother pipe 11. A large number of fins 17 are arranged in the axial direction of the mother pipe 11 at predetermined intervals.

  The roots 13 of the fins 17 are welded to the outer surface of the mother pipe 11. The welded portion between the fin 17 and the mother pipe 11 is formed by, for example, full circumference fillet welding between the root 13 of the fin 17 and the outer surface of the mother pipe 11. Thereby, heat is transferred from the fins 17 to the mother pipe 11 by heat conduction.

  The fin 17 of the present embodiment is formed with a bending portion 18 whose front end 14 and the vicinity thereof bend in the axial direction of the mother pipe 11, particularly in the upward direction of FIG. 8. The tips 14 of the fins 17 face upward.

  The fin 17 is a means for forming a curved surface on the fin by applying an external force after welding a flat fin to the mother pipe 11 in advance, before the fin 17 is welded to the mother pipe 11. Formed by.

  Therefore, in the present embodiment, since the curved portion 18 is formed on the fin 17, the surface of the fin 17 on which the curved portion 18 shown in FIG. 9 is formed is curved as compared with the fin formed in the planar shape of FIG. The intensity (emissivity) of the electromagnetic wave radiated from the curved surface of the portion 18 is increased. Therefore, the amount of radiant heat transfer from the fins 17 toward the mother pipe 11 can be increased.

  Here, the curvature of the bending portion 18 is set so that the intensity (emissivity) of the radiated electromagnetic wave is the highest.

  In the present embodiment, the bending portion 18 is formed so as to bend upward. However, the present invention is not limited to this, and the bending portion 18 may be formed to bend downward. Moreover, although the example which formed the curved part 18 in the fin 17 was demonstrated, you may form so that the front-end | tip 14 of the fin 17 and its vicinity may be bent in linear form besides this. Also in this case, it may be bent in either the upward direction or the downward direction.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  In addition, the said 1st Embodiment and 2nd Embodiment can be comprised in combination with the said 3rd Embodiment, respectively. With this configuration, the amount of radiant heat transfer toward the mother pipe 11 can be further increased.

  Moreover, in the said embodiment, although it was set as the structure which the some parallel mother pipe 11 connected between the inlet header 21 and the outlet header 22, as another example, the mother pipe 11 is made into a helical curved pipe or a meander. It may be a curved pipe (not shown).

  DESCRIPTION OF SYMBOLS 10 ... Heat-transfer tube, 11 ... Mother pipe, 12 ... Fin, 13 ... Root (fin base), 14 ... Tip (fin tip), 15 ... Heat source side fluid, 16 ... Heat receiving side fluid, 17 ... Fin, 18 ... Curved part 20 ... Heat exchanger, 21 ... Inlet header, 22 ... Outlet header, 23 ... Heat receiving side fluid inlet, 24 ... Heat receiving side fluid outlet, 30 ... Fin base material, 31 ... Microcavity layer, 32 ... Cavity, 32a ... opposing wall, 33 ... sawtooth shaped layer, 34a ... inclined surface, 34b ... vertical surface, 34c ... parallel surface

Claims (5)

A heat transfer pipe disposed in the heat source side fluid for transferring heat to the heat receiving side fluid having a temperature lower than that of the heat source side fluid,
A mother pipe through which the heat-receiving-side fluid circulates;
A fin extending in contact with the outer surface of the mother pipe and extending radially outward of the mother pipe from a root,
The fin is made of a fin base part and a high emissivity material having a higher heat emissivity than the fin base part, and is coated on at least a surface of the fin base part extending in the radial direction of the mother pipe. And a microcavity layer provided with a large number of cavities for resonating electromagnetic waves having a heat radiation wavelength. A heat transfer pipe disposed in the heat source side fluid for transferring heat to the heat receiving side fluid having a temperature lower than that of the heat source side fluid,
A mother pipe through which the heat-receiving-side fluid circulates;
A fin extending in contact with the outer surface of the mother pipe and extending radially outward of the mother pipe from a root,
The fin is made of a fin base part and a high emissivity material having a higher heat emissivity than the fin base part, and is coated on at least a surface of the fin base part extending in the radial direction of the mother pipe. And a sawtooth-shaped layer formed entirely in a sawtooth shape and having a surface facing the mother pipe side formed in an inclined surface.   The heat transfer tube according to claim 1, wherein the fin has a tip bent to the side of the mother tube.   A heat exchanger comprising the heat transfer tube according to any one of claims 1 to 3. A main pipe, a fin base part extending toward the outer side in the radial direction of the main pipe, and a high emissivity material having higher heat emissivity than the fin base part, and the fin base part and the main pipe A microcavity layer covering a surface and provided with a plurality of cavities for resonating electromagnetic waves having a heat radiation wavelength, and a method of manufacturing a heat transfer tube,
A welding step of fixing the fin base portion to the mother pipe by welding the whole circumference of the base of the fin base portion to the outer peripheral surface of the mother pipe;
After the welding step, at least a surface of the fin base portion extending in the radial direction of the mother pipe and a surface of the mother pipe are coated with a high emissivity material having higher heat emissivity than the fin base portion. A microcavity layer forming step of forming the microcavity layer,
The manufacturing method of the heat exchanger tube characterized by having.

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