JPH07318278A - Heat transfer tube with inner surface groove - Google Patents

Abstract

PURPOSE:To largely improve in-tube evaporating or condensing heat transfer efficiency at the time of evaporating or condensing refrigerant. CONSTITUTION:Many protruding strips 2 which are extended in a tube axis O direction and in which ends 2a are formed in a sharp shape, and grooves 3 formed between the strips 2 and in which opening gaps 3a of a centripetal direction are narrow are formed on the inner surface of a tube body made of good heat conductive metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is a patent application based on the provisions of Japanese Patent Application No. 6-65081, which is a prior application, based on the provisions of Article 42-2, paragraph 1 of the Patent Act. The present invention also relates to the structure of a heat transfer tube with an inner groove used as a heat transfer tube for a heat exchanger for an air conditioner, for example.

[0002]

2. Description of the Related Art A heat exchanger for a refrigerator such as a heat exchanger for an air conditioner, when used as an evaporator or a condenser, flows through a refrigerant flowing inside the heat transfer tube and a refrigerant flowing outside the heat transfer tube. It exchanges heat with the generated air to evaporate or condense (phase change) the refrigerant.

For the purpose of improving the evaporation heat transfer coefficient or the condensation heat transfer coefficient in each heat transfer tube used in the heat exchanger as described above, a large number of heat transfer tubes have been conventionally extended in the axial direction on the inner surface of the heat transfer tube. Has been developed, and various shapes of the ridges formed on the inner surface of the heat transfer tube have been devised.

For example, as disclosed in JP-A-2-97898 (first example), one having a large number of trapezoidal grooves formed on the inner surface of the heat transfer tube, or JP-A-4-1-1163.
As disclosed in Japanese Patent No. 91 (second example), there is a heat transfer tube having a tunnel-shaped groove formed on the inner surface thereof.

Further, for example, Japanese Patent Laid-Open No. 4-211117
As disclosed in (Third example), there is one in which a large number of protrusions having a triangular cross section are formed on the inner surface of the heat transfer tube.

[0006]

However, in the case of the first example of the above-mentioned known examples, in the case of acting as a condenser, the heat transfer performance is improved by thinning the condensed refrigerant liquid film. However, such a trapezoidal groove shape has a problem that it is difficult to generate boiling bubble nuclei for promoting evaporation heat transfer when it is made to act as an evaporator, and it is difficult to expect a dramatic improvement in performance. Further, when the flow velocity of the circulating refrigerant is small, even if the groove is spiral, the refrigerant flows down before reaching the pipe top, and the refrigerant flow mode becomes a laminar flow, and the pipe top cannot be effectively used. There is also a problem.

Further, in the case of the second example of the above-mentioned known examples, although the formation of the boiling bubble nucleus at the time of evaporation of the refrigerant is promoted by the formation of the tunnel-shaped groove, the tip of the ridge forming the groove has a sharp shape. When the refrigerant is condensed, the effect of the surface tension cannot be sufficiently obtained, so that the entire projection may be covered with the condensed liquid film, which may lead to a decrease in the condensation heat transfer coefficient in the tube.

Further, in the ridge structure of the third example of the above-mentioned known examples, the surface area of the valleys formed between the ridges having a triangular cross section is small, and the peak angle of the peaks is 30 ° to 60 °. Since it is large, the average liquid film thickness in the tube at the time of refrigerant condensation becomes large, the thermal resistance between the inner wall of the tube and the gas-liquid interface of the refrigerant is large, and again there is a limit in improving the heat transfer performance.

The present invention has been made in view of the above conventional problems, and it is possible to greatly improve the in-tube evaporation heat transfer coefficient or the in-tube condensation heat transfer coefficient during refrigerant evaporation or refrigerant condensation. It is an object of the present invention to provide a heat transfer tube with an inner groove.

[0010]

The present invention has been made for the purpose of solving the above problems, and in order to achieve the above object, for example, the following problem solving means
It is configured with (configuration).

First, according to the first aspect of the invention of the present application, a large number of ridges extending in the axial direction of the pipe and having sharpened tips at the inner surface of the pipe made of a metal having good thermal conductivity, Grooves are formed between the protrusions, each of which has a narrow opening in the centripetal direction.

In the structure of the second invention of the present invention, a large number of ridges extending in the tube axis direction and having sharpened tips at the inner surface of the tube body made of a heat conductive metal, and these A groove having a circular arc shape at the bottom of the groove is formed between the ridges.

In the structure according to the third aspect of the present invention, each of the ridges and grooves has a spiral shape having a predetermined lead angle with respect to the tube axis direction.

In the structure of the fourth aspect of the present invention, the inner surface of the tubular body made of a metal having good thermal conductivity extends in the axial direction of the tube and has a triangular cross-section at its tip and a vertical angle of 30 degrees or less. It is configured by providing a ridge.

In the fifth aspect of the present invention, the inner surface of the tube made of the heat-conductive metal in the tube axis direction extends in the tube axis direction, and the tip thereof has a triangular cross section and the apex angle is 13 degrees or less. It is configured by providing a large number of ridges.

According to a sixth aspect of the present invention, in the fourth and fifth aspects of the invention, each of the protrusions has a spiral shape having a predetermined lead angle with respect to the tube axis direction. .

In the configuration of the seventh invention of the present invention, after the heat transfer tubes of the configurations of the fourth, fifth and sixth inventions are formed by cutting one side surface of an elongated flat plate to form a ridge, It is formed by spirally winding and forming a cylinder.

In the structure of the eighth invention of the present invention, the heat transfer tubes of the structures of the fourth, fifth, and sixth inventions are welded and integrated with a ridge formed separately on one side surface of an elongated flat plate. It is formed into a cylindrical body by winding it in a spiral shape.

[0019]

Therefore, the heat transfer tubes with inner groove according to the first to eighth inventions of the present invention have the following operations corresponding to the above respective configurations.

That is, first, in the configuration of the first invention of the present invention, when the refrigerant is evaporated, the refrigerant liquid flows through the groove having a narrow opening gap in the centripetal direction, so that the boiling bubble nucleus is generated. On the other hand, when the refrigerant is condensed, the effect of surface tension promotes the removal of the refrigerant liquid from the ridge tips to the groove side.Therefore, not only in the high dry range but also in the medium dry range to the low dry range. Even in the temperature range, the tips of the ridges are exposed (that is, not covered by the condensed liquid film), so the transfer of heat to and from the refrigerant is promoted by using the boundary layer leading edge effect. Becomes

In the configuration of the second invention of the present invention, the action obtained by making the tip of the ridge sharp is the same as that of the configuration of the first invention, but the shape of the groove bottom is substantially the same. The arc shape increases the area of the bottom of the groove, and the refrigerant liquid flowing down from the ridges when the refrigerant is condensed can be smoothly discharged to the pipe outlet side. Therefore, the refrigerant liquid film of the ridge can be further thinned.

In the third aspect of the invention of the present application, the protrusion and the groove are formed in a spiral shape having a predetermined lead angle with respect to the tube axis direction, and the refrigerant flowing in the groove is guided to the top of the tube. Therefore, the entire inner surface of the pipe is wet with a thin liquid film. In particular, when this configuration is used in combination with the configuration of the first aspect of the present invention, the effect of retaining the refrigerant liquid near the top of the pipe is increased even when the flow velocity is low.

According to the fourth aspect of the present invention, as described above, the inner surface of the tubular body made of a heat-conductive metal extends in the axial direction of the tube, and its tip has a triangular cross section and an apex angle. Is 3
A large number of ridges with a sharp tip of 0 degrees or less are provided, which makes it possible to increase the ridge height and sharpen the groove apex angle as much as possible within the pipe manufacturing limit compared to conventional products. It becomes possible to suppress the liquid submersion of the portion by the liquid refrigerant, and thin the liquid film by increasing the surface tension of the tip portion. Further, by optimizing the lead angle and the number of grooves in addition to this, it is possible to sufficiently increase the surface area of the groove troughs between the protrusions, so that a more sufficient effect of improving the heat transfer coefficient is realized. Will be able to.

Further, in the configuration of the fifth invention of the present invention,
On the inner surface of the tube made of heat conductive metal in the tube axis direction, a number of ridges extending in the tube axis direction, having a triangular cross-section and an apex angle of 13 degrees or less are provided. It is possible to increase the height of the ridges and make the groove apex angle as sharp as possible within the pipe manufacturing limit, and it is possible to prevent the mountain portion from being submerged by the liquid refrigerant, and at the tip of the mountain portion. The surface tension of is further increased, and further thinning of the liquid film is realized. Further, by further optimizing the lead angle and the number of grooves, the surface area of the groove troughs can be expanded more effectively, and a higher effect of improving the heat transfer coefficient can be realized.

Further, in the configuration of the sixth invention of the present invention, as described above, the ridge has a spiral shape having a predetermined lead angle with respect to the tube axis direction.

When the plurality of ridges and the grooves formed between the plurality of ridges have a spiral shape having a predetermined lead angle with respect to the pipe axis direction, the refrigerant flowing between the grooves is guided to the top of the pipe. Since this is possible, the entire inner surface of the pipe becomes wet with a thin liquid film. Therefore, the heat transfer performance is further improved. In particular, when used in combination with each of the above configurations, the refrigerant liquid retention effect near the pipe top is increased even at low flow rates,
It will be more effective.

Further, in the configuration of the seventh invention of the present invention, as described above, after one side surface of the elongated flat plate is cut to form a ridge, the ridge is spirally wound into a cylindrical body. Since it is formed by cutting, the sharpening of the top of the ridge as much as possible facilitates the removal of the refrigerant liquid from the tip of the ridge to the groove side due to the effect of surface tension, especially when the refrigerant is condensed. Since the tip of each ridge is exposed (that is, not covered with the condensate film) not only in the high-dry range but also in the medium-to-low dry range Utilizing the layer leading edge effect effectively promotes heat exchange with the refrigerant.

In the eighth aspect of the present invention,
As described above, the ridges separately formed on one side of the elongated flat plate are welded and integrated, and then spirally wound to form a tubular body. In particular, when the refrigerant is condensed, the surface tension effect further promotes the removal of the refrigerant liquid from the tips of the ridges to the groove side, and not only in the high-dry range but also in the medium-dry range. Even in the dryness range, the tip of each ridge is exposed (that is,
Since it is not covered with the condensed liquid film), the heat exchange with the refrigerant can be more effectively promoted by utilizing the boundary layer leading edge effect.

[0029]

As a result of the above, according to the present invention, at the time of evaporation of the refrigerant, the refrigerant liquid flows through the groove narrowed in the opening gap in the centripetal direction, thereby promoting the generation of the boiling bubble nucleus. On the other hand, when the refrigerant is condensed, the effect of surface tension promotes the removal of the refrigerant liquid from the ridge tips to the groove side, so that not only in the high dryness range but also in the medium dryness range to the low dryness range. Also, the tip of each ridge is exposed (that is,
Being not covered by the condensed liquid film), the transfer of heat to and from the refrigerant is promoted by using the boundary layer leading edge effect, and the evaporation heat transfer coefficient in the tube and the condensation heat transfer coefficient in the tube are significantly improved. There is an excellent effect that it can be achieved.

Therefore, when a heat exchanger is constructed using such a heat transfer tube, the heat exchange efficiency of the heat exchanger is greatly improved, and a more compact size can be achieved.

On the other hand, by making the shape of the bottom of the groove substantially arcuate, the area of the bottom of the groove increases, and the refrigerant liquid flowing down from the ridges during refrigerant condensation smoothly flows out to the pipe outlet side. It becomes possible.

Therefore, there is an excellent effect that the refrigerant liquid film of the ridge can be further thinned and the condensation heat transfer coefficient in the pipe can be improved.

In each of these cases, when the protrusion and the groove have a spiral shape having a predetermined lead angle with respect to the pipe axis direction, it becomes possible to guide the refrigerant flowing through the groove to the pipe top. The entire inner surface of the tube will be wet with a thin liquid film. Therefore, the heat transfer performance can be further improved thereby. Further, as a result, the effect of retaining the refrigerant liquid near the top of the pipe is increased even when the flow velocity is low, which is more effective.

Further, the ridge apex angle is selected to be the most effective acute angle range that is feasible in the processing technology, in which the apex angle is equal to or less than a predetermined angle, and is set appropriately in relation to the value for increasing the groove valley surface area. Then, the higher heat transfer performance can be obtained by the synergistic effect of thinning the liquid film by increasing the surface tension at the tip of the crest and increasing the surface area in the trough.

As a result, according to the structure of the heat transfer tube with the inner surface ridge of the present invention, it is possible to improve the heat transfer performance of the heat exchanger more sufficiently than the conventional structure.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) FIGS. 1 to 6 show a heat transfer tube with an inner surface groove and a method for manufacturing the same according to Embodiment 1 of the present invention.

As shown in FIGS. 1 and 2, the heat transfer tube with the inner groove of the present embodiment has a predetermined shape with respect to the tube axis O on the inner surface of the tube body 1 made of a heat conductive metal (for example, copper). Of the respective tips 2a, 2a extending spirally in a direction having a lead angle θ of
.. a large number of ridges 2, 2 ... with sharp points, and the opening gaps 3a in the centripetal direction between these ridges 2, 2.
.. are formed so as to form grooves 3, 3 ...

The heat transfer tube with the inner groove having the above structure can be manufactured by the method shown in FIGS.

First, as shown in FIG. 3, with respect to an elongated flat plate 1'made of a heat conductive metal (for example, copper), a ridge 2 ', which extends in the longitudinal direction by using a fin forming disk 5, is formed.
2 ′ ·· are formed at equal intervals. Each protrusion 2'formed at this time is a trapezoidal protrusion having a flat top surface. Further, the grooves 3 ', 3' ... formed between the ridges 2 ', 2' ...
The bottom portions 3b ', 3b' ... Of are formed in an arc shape. This is because it is difficult to process unless the tip of the fin forming disk 4 has an arcuate shape. However, by forming the arcuate bottom 3a ', the bottom 3b of the groove 3 to be completed later also has an arcuate shape. (See Figure 5).

Next, as shown in FIG. 4, a V-shaped disc 6 is used to form a V-shaped groove 4, at the tip of each of the ridges 2 ', 2' ...
Form 4 ... Then, the ridges 2 ', 2' ... Are bisected by the V-shaped grooves 4, 4 ,.
.. is to form sharp ridges 2, 2 ..

Then, as shown in FIG. 5, the tip ends 2a, 2a, ... Of the adjacent ridges 2, 2 ,. Then, the grooves 3, 3, ... Between the ridges 2, 2, ..
・ Is formed. In the case of this embodiment, the adjacent grooves 3,
V-shaped grooves 4, 4 ... Are formed between 3 ... Of course, the inside of these V-shaped grooves 4, 4 ... Also serves as a refrigerant liquid passage.

Thereafter, as shown in FIG. 6, the ridges 2, 2, ...
The flat plate 1 ′ is spirally rolled into a cylindrical shape with the surface on which the grooves 3 and 3 are formed as the inner surface, and the longitudinal end faces of the flat plate 1 ′ are welded to each other. Then, the heat transfer tube with the inner groove having the structure shown in FIGS. 1 and 2 is obtained.

When the heat exchanger is constructed by using the heat transfer tube with the inner groove having the above construction, the following operational effects are exhibited.

At the time of evaporation of the refrigerant, the refrigerant liquid Xw flows through the groove 3 narrowed in the opening 3a in the centripetal direction, thereby promoting the generation of the boiling bubble nucleus G. Therefore, the evaporation heat transfer coefficient in the tube is significantly improved.

On the other hand, at the time of condensing the refrigerant, the removal of the condensed refrigerant liquid Xw from the ridge tips 2a to the groove 3 side is promoted by the effect of the surface tension.
Tip 2 of each ridge 2 in the medium to low dryness range
When a is exposed (that is, not covered with the condensed liquid film), transfer of heat to and from the refrigerant is promoted by utilizing the boundary layer leading edge effect. Therefore, the condensation heat transfer coefficient in the pipe is significantly improved.

In addition, in the case of this embodiment, since the ridge 2 and the groove 3 are formed in a spiral shape having a predetermined lead angle θ with respect to the pipe axis O, the refrigerant flowing in the groove 3 can be guided to the pipe top. Therefore, the entire inner surface of the pipe is wet with a thin liquid film. Therefore, the heat transfer performance can be further improved. In particular, it is more effective because the effect of retaining the refrigerant liquid near the pipe top is increased even at a low flow velocity.

Further, in the case of this embodiment, the bottom portion 3b of the groove 3 is
Since the area of the groove bottom 3b is slightly increased by making the arc shape substantially arc-shaped, the refrigerant liquid Xw flowing down from the ridges 2 at the time of refrigerant condensation can be smoothly discharged to the pipe outlet side. . Therefore, the refrigerant liquid film of the ridge can be further thinned, and the condensation heat transfer coefficient in the pipe can be improved.

(Embodiment 2) FIG. 7 shows the shape of the inner surface of the heat transfer tube with the inner groove according to the second embodiment of the present invention.

In the heat transfer tube with the inner groove of this embodiment, the inner surface of the tube body 1 made of a heat conductive metal (for example, copper) extends in the direction of the tube axis O and the respective tips 2a, 2a. A large number of sharp ridges 2, 2, ... And these ridges 2, 2.
・ Grooves 3,3 between which the overall shape is arcuate
And are formed. These ridges 2, 2 ...
The grooves 3, 3, ... Spirally extend in a direction having a predetermined lead angle θ with respect to the tube axis O, as in the first embodiment (see FIG. 1).

In the case of the heat transfer tube with the inner groove of this embodiment, the working effect obtained by making the tip 2a of the ridge 2 into a sharp shape is the same as in the case of the first embodiment. In addition, in the case of the present embodiment, by making the entire shape of the groove 3 into an arc shape,
Since the entire area of the groove 3 is increased and a smooth curve is formed from the side surface to the bottom portion, the refrigerant liquid Xw flowing down from the ridges 2 at the time of condensation of the refrigerant is smoothly discharged to the pipe outlet side. The action and effect is further improved. Therefore, the heat transfer tube with the inner groove of the present embodiment is more effective when used as a condenser.

By the way, in the case of the heat transfer tube with the inner groove having the structure as in this embodiment, since the cross-sectional shape of the groove 3 formed on the inner surface may affect the heat transfer coefficient and the pressure loss in the tube, When the groove apex angle α (see FIG. 8), the groove height H (see FIG. 8), the lead angle θ (see FIG. 1) and the number of grooves N were changed, the heat transfer coefficient and the pressure loss at that time were measured. The results shown in FIGS. 9 to 16 were obtained. At this time, the outer diameter of the heat transfer tube was 7.00 mm and the bottom wall thickness of the groove 3 was 0.25 mm.

The results shown in FIGS. 9 and 10 show that the smaller the groove apex angle α, the higher the evaporation heat transfer coefficient and the condensation heat transfer coefficient, and when α ≦ 10 (dig), there is little change. Therefore, it can be seen that it is desirable to make the value as small as possible within the manufacturing range with α ≦ 10 (dig). The change in groove apex angle α has almost no effect on the pressure loss.

According to the results shown in FIGS. 11 and 12,
It can be seen that when the groove height H increases, the evaporation heat transfer coefficient and the condensation heat transfer coefficient increase, and when H ≧ 0.20 (mm), there is little change. Therefore, 0.25 (mm) ≧ H ≧ 0.20
It is desirable to set it in the range of (mm). Here, the upper limit of the groove height H is set to 0.25 mm because of the manufacturing limit. In addition,
The change in groove height H has almost no effect on the pressure loss.

According to the results shown in FIGS. 13 and 14,
The evaporation heat transfer coefficient and the condensation heat transfer coefficient have a lead angle θ ≈ 18 (d
It can be seen that the maximum value is set to (ig) and the value becomes lower when it becomes larger or smaller. Therefore, 15 (dig)
It is desirable that the range is ≦ H ≦ 25 (dig). The change in the lead angle θ has almost no effect on the pressure loss.

According to the results shown in FIGS. 15 and 16,
It can be seen that the evaporation heat transfer coefficient and the condensation heat transfer coefficient have maximum values when the number of grooves N≈55, and are lower when the groove number is larger or smaller. Therefore, it is desirable that the range is 50 ≦ N ≦ 60. The change in the number of grooves N has almost no effect on the pressure loss.

In the above embodiment, the ridges and grooves have a spiral shape, but the present invention can be applied to those in which the ridges and grooves are parallel to the tube axis. is there.

(Embodiment 3) FIGS. 17 and 18 show the structure of a heat transfer tube with an inner groove according to Embodiment 3 of the present invention and its heat transfer performance improving effect.

That is, as shown in FIG. 17, for example, the heat transfer tube with the inner surface groove of the present embodiment has the same structure as in the case of FIG. 1 on the inner surface of the tube body 1 made of a heat conductive metal (for example, copper). The spiral angle in a direction having a predetermined lead angle θ with respect to the tube axis O and the angles of the respective apexes 2a, 2a.
(Vertical angle) α is 30 degrees or less, and a large number of ridges 2, 2 ... With a triangular shape in cross section, and each of these ridges 2, 2
.. Grooves 3 and 3 of depth H (H = 0.25 mm) having an opening gap between which the diameter gradually increases in the centripetal direction (radial direction)
.. and consist of

In the heat transfer tube with the inner groove having the above-described structure, as in the case of the first embodiment, for example, one side surface of the elongated flat plate is cut to form the ridges 2, 2, ...
・ By forming spirals and then forming them into a tubular body by forming a spiral shape, and on the other hand, the projections 2, 2 with the apex angle α separately formed on one side surface of an elongated flat plate are integrally welded together. After being formed, they are spirally wound inside and formed into a cylinder.

In the heat transfer tube having the above structure, for example, in the case of the current heat transfer tube which is one of the conventional examples shown in FIG. 21, (α = 4
Compared to 0-60 °, H = 0.18mm), the ridge (mountain part) 2.2
・ The apex angle α is sufficiently small and the groove (groove valley) 3,3
..The depth H of .. is sufficiently deep that ridges 2, 2
.. In particular, the surface tension of the refrigerant is sufficiently increased particularly at the top portions 2a, 2a .. and the thinning of the liquid film is effectively achieved, and the inner surface portion (groove valley surface portion) 3b of the grooves 3, 3. Since the surface areas of 3b and 3b are maximized, it is possible to contribute to a sufficient improvement in heat transfer performance as compared with the conventional structure shown in FIG. 21, for example, as shown in the measurement data of FIG.

(Embodiment 4) FIGS. 19 and 20 show the structure of a heat transfer tube with an inner groove according to Embodiment 4 of the present invention and the effect of improving the heat transfer performance thereof.

That is, as shown in FIG. 19, for example, as shown in FIG. 19, the heat transfer tube with the inner groove of the present embodiment has the same structure as that of FIG. O
With respect to each other, it extends spirally in a direction having a predetermined lead angle θ, and the angle (vertical angle) α of each of the apexes 2a, 2a.
A large number of ridges 2, 2 ... with a triangular shape in cross section, which are especially sharp, and are between the ridges 2, 2 ... Each of which the diameter gradually increases in the centripetal direction (radial direction). It is composed of grooves 3 having a depth H (H = 0.25 mm) having a gap.

In the heat transfer tube with the inner surface groove having the above structure, for example, one side surface of an elongated flat plate is machined in the same manner as in the above-mentioned case, so that the ridges 2, 2, ... With a vertex angle α (α = 13 ° or less). After forming, by spirally winding to form a cylinder,
On the other hand, on the other hand, the ridges 2,2 ... with apex angle α (α = 13 ° or less) separately formed on one side of the elongated flat plate are welded and integrated, and then they are spirally wound inside. It is formed by forming a cylinder.

In the heat transfer tube having the above-described structure, for example, as compared with the current heat transfer tube shown in FIG.
Is particularly small at 13 degrees or less, and the depth H of the groove portions 3, 3, ... Is sufficiently deeper, so the above-mentioned ridge portion (mountain portion) 2,
In 2 ..., especially, the surface tension of the refrigerant is further increased at the top portions 2a, 2a .. and the thinning of the liquid film is achieved more effectively, and the inner surface of the grooves 3, 3. ) 3b,
Since the surface area of 3b ... Is maximally expanded, as shown in FIG. 20, it is possible to contribute to a more sufficient improvement in heat transfer performance as compared with the conventional structure of FIG.

[Brief description of drawings]

FIG. 1 is a side view in which a part of a heat transfer tube with an inner groove according to a first embodiment of the present invention is shown in section.

FIG. 2 is an enlarged cross-sectional view of a main part of the heat transfer tube with the inner groove according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a state of a first step (that is, a ridge processing step using a fin-forming disk) in the method for manufacturing the heat transfer tube with the inner groove according to the first embodiment of the present invention.

FIG. 4 is an explanatory view showing a state of a second step (that is, a V-shaped groove processing step using a V-shaped disc) in the method for manufacturing the heat transfer tube with the inner surface groove according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a state of a third step (that is, a roll processing step using a piled roll) in the method for manufacturing the heat transfer tube with the inner surface groove according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a state of a fourth step (that is, a cylindrical roll welding step) in the method for manufacturing the heat transfer tube with the inner groove according to the first embodiment of the present invention.

FIG. 7 is an enlarged perspective view of an essential part of a heat transfer tube with an inner groove according to a second embodiment of the present invention.

FIG. 8 is an enlarged sectional view of an essential part of a heat transfer tube with an inner groove according to a second embodiment of the present invention.

FIG. 9 is a characteristic diagram showing changes in evaporation and condensation heat transfer rates when the groove apex angle is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 10 is a characteristic diagram showing changes in pressure loss when the groove apex angle is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 11 is a characteristic diagram showing changes in the evaporation and condensation heat transfer rates when the groove height is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 12 is a characteristic diagram showing a change in pressure loss when the groove height is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 13 is a characteristic diagram showing changes in evaporation and condensation heat transfer rates when the lead angle is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 14 is a characteristic diagram showing a change in pressure loss when a lead angle is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 15 is a characteristic diagram showing changes in evaporation and condensation heat transfer rates when the number of grooves is changed in the heat transfer tube with an inner groove according to the second embodiment of the present invention.

FIG. 16 is a characteristic diagram showing a change in pressure loss when the number of grooves is changed in the heat transfer tube with an inner surface groove according to the second embodiment of the present invention.

FIG. 17 is a sectional view of essential parts showing a structure of a heat transfer tube with an inner surface groove according to Embodiment 4 of the present invention.

FIG. 18 is a graph showing a heat transfer performance improving effect of the heat transfer tube according to the fourth embodiment of the present invention in comparison with a conventional example.

FIG. 19 is a sectional view of essential parts showing a structure of a heat transfer tube with an inner surface groove according to Embodiment 5 of the present invention.

FIG. 20 is a graph showing a heat transfer performance improving effect of the heat transfer tube according to the fifth embodiment of the present invention in comparison with a conventional example.

FIG. 21 is a sectional view of an essential part showing the structure of a conventional heat transfer tube with an inner groove.

[Explanation of symbols]

Reference numeral 1 is a tube, 2 is a ridge, 2a is a tip of the ridge, 3 is a groove, 3a is an opening gap, 3b is a groove bottom, O is a tube axis, and θ is a lead angle.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazumi Toda 1304 Kanaoka-cho, Sakai City, Osaka Prefecture Daikin Industries, Ltd.Kanaoka Plant, Sakai Manufacturing Co., Ltd. (72) Kanji Akai 1304, Kanaoka-cho, Sakai City, Osaka Prefecture Sakai Factory Kanaoka Factory

Claims (8)

[Claims] 1. A large number of protrusions extending in the pipe axial direction and having a sharp tip at the inner surface of a tubular body made of a heat conductive metal, and opening gaps in the centripetal direction between these protrusions. A heat transfer tube with an inner groove, each of which has a narrow groove. 2. A large number of projections extending in the tube axial direction and having sharp tips on the inner surface of a tube made of a heat-conductive metal, and grooves having an arc-shaped bottom between these projections. A heat transfer tube with an inner groove, characterized in that 3. The heat transfer tube with an inner surface groove according to claim 1, wherein the projection and the groove have a spiral shape having a predetermined lead angle with respect to the tube axis direction. 4. A large number of ridges extending in the axial direction of the tube, having a triangular cross-section, and having an apex angle of 30 degrees or less are provided on the inner surface of the tube made of a heat conductive metal. Heat transfer tube with inner groove. 5. A large number of ridges extending in the tube axis direction and having a triangular cross-section at the tip and an apex angle of 13 degrees or less are provided on the inner surface of the tube made of a heat conductive metal in the tube axis direction. Heat transfer tube with inner groove. 6. The heat transfer tube with an inner surface groove according to claim 4, wherein the projection has a spiral shape having a predetermined lead angle with respect to the tube axis direction. 7. The inner surface groove according to claim 4, 5 or 6, wherein a ridge is formed by cutting one side surface of an elongated flat plate and then spirally wound into a tubular body. Heat transfer tube with. 8. The inner surface groove according to claim 4, wherein the projection formed separately on one side surface of the elongated flat plate is integrally welded and then spirally wound into a tubular body. Heat transfer tube with.