JP2009030913A - Heat transfer pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat transfer pipe wherein a fin area is reduced, water is easily spread to a pipe axis direction correspondingly, the whole of a pipe outer peripheral surface can be wet, and as a result, a heat transfer rate outside the pipe can be improved. <P>SOLUTION: In the heat transfer pipe 11, a fin 12 spirally protruding from a pipe outer peripheral surface is formed, and a protrusion 13 and a recess 14 are formed on the fin 12 along the longitudinal direction of the fin 12 in a repeated manner in a normal or reverse state. The length La of the protrusion 13 is equal to or shorter than the length Lb of the recess 14, and a gap between the adjacent protrusions 13 is in a range of 1.0 mm to 10 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat transfer tube used for an evaporator or an absorber such as an absorption refrigerator used for cooling a building or an absorption heat pump for air conditioning.

In a cooling system using an absorption chiller used for building cooling, an absorption heat pump for air conditioning, etc., the heat transfer tubes are arranged horizontally in a multi-row and vertical direction inside the evaporator and absorber. Installed, communicating the ends of adjacent heat transfer tubes in the vertical direction, keeping the inside of the evaporator at a reduced pressure of about 5 mmHg, and flowing about 12 ° C water into the heat transfer tube The refrigerant (water) supplied from the condenser is dripped or dispersed.
And it is comprised so that the flowing water in a heat exchanger tube may be cooled to about 7 degreeC by the latent heat at the time of a refrigerant | coolant flowing down the surface of a heat exchanger tube group, and evaporating.

  On the other hand, in the absorber, the heat transfer tubes are installed horizontally so as to form a multi-row and multi-stage in the vertical direction, the ends of the heat transfer tubes adjacent in the vertical direction are communicated, and the cooling medium (water) is placed in the heat transfer tubes While flowing, the absorbing solution (lithium bromide aqueous solution) supplied from the regenerator through the cooling heat exchanger to the heat transfer tube is dropped or sprayed.

  The absorbing liquid absorbs the refrigerant vapor evaporated by the evaporator when flowing down the surface of the heat transfer tube group, and then is sent to the regenerator. The cooling medium in the heat exchanger tube of the absorber is configured so as to be sent to the heat exchanger tube of the condenser after cooling the absorbing liquid whose temperature rises due to absorption of the refrigerant vapor.

  Conventionally, this type of heat transfer tube uses a spiral finned tube in which fins are spirally formed on the outer peripheral surface of the tube in order to improve the heat transfer rate outside the tube in an evaporator and an absorber.

Furthermore, in the heat transfer tubes, the evaporating area of the outer peripheral surface of the tube is increased, and in order to further improve the heat transfer performance (heat transfer coefficient outside the tube), the height of the fin is increased, There are also heat transfer tubes with more fins.
By the way, as mentioned above, the cooling medium in the heat transfer tube in the evaporator is cooled by using latent heat generated when the water dropped on the heat transfer tube evaporates by the condenser. It is necessary to spread thinly over the entire outer peripheral surface.

  However, as described above, when the fins are positively formed on the outer peripheral surface of the pipe, a situation occurs in which the spiral fins hinder the movement of water in the pipe axis direction.

In response to such a situation, the following Patent Document 1 discloses “a heat transfer tube for an evaporator and a method for manufacturing the same”.
According to Patent Document 1, “a heat transfer tube for an evaporator and a manufacturing method thereof” in which a pressing portion (2) is intermittently formed in a spiral fin (1) along the fin forming direction is disclosed.

  The “heat exchanger tube for evaporator” in Patent Document 1 is configured such that water dripped onto the heat transfer tube can move in the tube axis direction through the pressing portion (2).

  With the above configuration, it can be said that the “heat transfer tube for evaporator” in Patent Document 1 certainly facilitates diffusion of water in the tube axis direction as compared to a heat transfer tube having a configuration in which no pressing portion is formed on the fin. .

  However, according to Patent Document 1, “the evaporator heat transfer tube and the manufacturing method thereof” is designed to minimize the reduction of the fin area due to the formation of the pressing portion (2). The length is limited to a short length of 0.3 mm or less.

  For this reason, whether water is diffused in the direction of the tube axis and the effect of forming the pressing portion (2) on the fin that can improve the heat transfer coefficient outside the tube can be sufficiently exhibited. Further study was needed.

JP-A-11-118382

  Therefore, in the present invention, although the fin area is reduced, water easily spreads in the direction of the tube axis, and the entire outer peripheral surface of the tube can be wetted. As a result, the tube is significantly more than conventional heat transfer tubes. It aims at providing the heat exchanger tube which can improve an external heat transfer rate.

  The heat transfer tube of the present invention is a heat transfer tube in which a fin projecting spirally from the outer peripheral surface of the tube is formed, and a convex portion and a concave portion are repeatedly formed in the fin in the forward and reverse directions along the length direction of the fin. And the length of the said convex part was formed below the length of the said recessed part, and the space | interval of the said adjacent convex parts was formed in the range of 1.0 mm to 10 mm, It is characterized by the above-mentioned.

  In the heat transfer tube of the present invention, the ratio of the length of the convex portion to the concave portion can be formed within a range of 0.25 to 1.

  The heat transfer tube of the present invention is characterized in that a repeated pitch between the convex portion and the concave portion is formed within a range of 1.0 mm to 10 mm.

  In the heat transfer tube of the present invention, the height of the convex portion of the fin with respect to the outer peripheral surface of the tube can be formed within a range of 0.2 mm to 0.95 mm.

  In the heat transfer tube of the present invention, the concave portion with respect to the fin top portion can be formed with a depth within a range of 0.1 mm to 0.8 mm and at least a height equal to or greater than the outer peripheral surface of the tube.

  The fins can be formed within a range of 19 to 50 sheets per inch in a cross-section obtained by cutting the heat transfer tube along the tube axis direction.

  In addition, since the convex part and the recessed part are repeatedly formed in the fin direction in the fin in the fin direction and include the recessed part, the recessed part has a recessed part in a cross section obtained by cutting the heat transfer tube along the tube axis direction. Although it may appear, this recess is also counted as a part of the fin.

  The concave portion is, for example, a notch-shaped portion that can be formed by intermittently pressing the fin with a special tool such as a work roll or a gear-shaped disk tool, and the fin has a length direction. When the concave portion and the convex portion are repeated along, the portion having the lowest height relative to the outer peripheral surface of the pipe is shown within the range of the interval between the adjacent convex portions.

  On the other hand, although the said convex part shows the top part (fin upper end part) of a fin, in addition to the step part of the shape which notched the fin top part so that height might become higher than the said recessed part, ie, in a fin In the space | interval of the said adjacent top parts, the part higher than the said recessed part is included.

  The interval between the adjacent convex portions indicates the interval between the predetermined adjacent convex portions in the fin in which the convex portion and the concave portion are repeatedly formed in the forward and reverse directions. The space | interval of the intermediate parts of a length direction is shown.

  In the present invention, although the fin area is reduced, the water of the pipe shaft surrounding work is easily spread, and the entire surface of the pipe can be wetted. As a result, the heat outside the pipe is significantly higher than that of the conventional heat transfer pipe. The transmission rate can be improved.

An embodiment of the present invention will be described below with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the heat transfer tube 11 in the first embodiment forms a fin 12 that protrudes spirally from the outer peripheral surface of the tube with a height (H) of 0.3 mm, and the fin 12 has its length. A convex portion 13 and a concave portion 14 are formed along the direction, the length of the convex portion 13 is set to be equal to or shorter than the length of the concave portion 14, and the interval between the adjacent convex portions 13 is 1.0 mm to 10 mm. It is formed within the range.
FIG. 1 is a partially enlarged front view of the heat transfer tube 11 in the first embodiment.

As shown in FIGS. 2A and 2B, the heat transfer tube 11 has a ratio (La / Lb) of the length (La) of the convex portion 13 to the length (Lb) of the concave portion 14 as 0. 0.75 which is within a range of .25 to 1, and the concave portion 14 and the convex portion 13 are repeatedly formed in the forward and reverse directions along the length direction of the fin 12, and the length direction of the fin 12 A repetitive pitch (P) between the concave portion 14 and the convex portion 13 is formed at 7 mm within a range of 1.0 mm to 10 mm.
2A and 2B are perspective views showing a part of the outer peripheral portion of the heat transfer tube 11 in the first embodiment, respectively, and are enlarged perspective views of the fin 12 portion.

  Further, the heat transfer tube 11 is formed such that the height (H) of the convex portion 13 of the fin 12 with respect to the outer peripheral surface of the tube is 0.3 mm, which is in the range of 0.2 mm to 0.95 mm.

  Further, the concave portion 14 with respect to the fin top portion 12T is formed with a depth (d) of 0.25 mm which is a depth (d) within a range of 0.1 mm to 0.8 mm, and at least equal to or greater than the outer peripheral surface of the pipe. It is formed with height.

  Further, the fins 12 are formed at a rate of 40 sheets / inch, which is in a range of 19 to 50 sheets per inch in a cross section obtained by cutting the heat transfer tube 11 along the tube axis direction Y.

  Furthermore, since the concave portion 14 is formed with a depth (d) of 0.25 mm with respect to the fin 12 having a height of 0.3 mm as described above, the height (h) with respect to the outer peripheral surface of the pipe is small. 0.05 mm.

  And as above-mentioned, as for the said heat exchanger tube 11, the ratio (La / Lb) of the length of the said convex part 13 with respect to the said recessed part 14 is 0.75, and also the pitch (P) of the length direction of a fin is Since it is 7 mm, the length (Lb) in the length direction of the fin of the concave portion 14 is 4 mm, and the length (La) of the fin in the length direction of the convex portion 13 is 3 mm. .

  Further, as shown in FIG. 1, the helical fin 12 has a large twist angle θ (70 to 85 degrees) with respect to the tube axis.

  As shown in FIG. 3 (a), the heat transfer tube 11 described above has fins 12 formed in a spiral shape by a fin-forming disk tool group 15 on the outer peripheral surface of a heat transfer element tube 11 'manufactured by a conventional method. Then, the fin 12 is intermittently pressed by the gear-shaped disk tool 16 disposed on the outer peripheral surface of the heat transfer element tube 11 ′ in which the fin 12 is formed, and the convex portion 13 and the concave portion 14 are formed in the fin 12. It is manufactured by.

Specifically, as shown in FIG. 3 (b), a plurality of gear-shaped disk tools 16 are arranged at equal distribution angular intervals in the circumferential direction of the heat transfer element tube 11 ′, and the inside of the heat transfer element tube 11 ′. Although not shown, a rotatable mandrel is inserted and rotated in the same direction with the gear disk tool 16 pressed against the mandrel side.
The outer peripheral surface 16a of the gear-shaped disk tool 16 has a concavo-convex shape symmetrical to the fin 12 in which the convex portion 13 and the concave portion 14 of the heat transfer tube 11 are repeatedly formed. Is inclined by an angle corresponding to the twist angle θ of the fin 12 of the heat transfer tube 11 with respect to the tube axis direction of the heat transfer element tube 11 ′.
Therefore, when the gear-shaped disk tool 16 is rotated in the same direction while being pressed against the heat transfer element tube 11 ′, the heat transfer element tube 11 ′ is pressed by the gear-shaped disk tool 16 and moved. Spiral fins 12 are continuously processed on the tube surface, and the fins 12 can be alternately and continuously processed with convex portions 13 and concave portions 14 along the length direction of the fins 12. it can.

In addition, the convex part 13 of the fin 12 is corresponded to the part which was not pressed by the said gear-shaped disk tool 16 in the length direction of the fin 12. FIG.
As described above, the fin 12 and the recess 14 are continuously formed, so that extremely high productivity can be obtained.
3A and 3B are process explanatory views showing examples of the method of manufacturing the heat transfer tube 11 in the first embodiment, respectively, in the process of forming the convex portion 13 and the concave portion 14 on the fin 21. It is explanatory drawing which shows an example.

As described above, according to the heat transfer tube 11 of the first embodiment,
A fin 12 protruding spirally from the outer peripheral surface of the tube is formed, and a convex portion 13 and a concave portion 14 are formed in the fin 12 along the length direction of the fin 12, and the length of the convex portion 13 is It forms below the length of the said recessed part 14, and the space | interval of the said adjacent convex parts is formed in the range of 1.0 mm to 10 mm.

For this reason, for example, when incorporated into an evaporator in a cooling system and used, water dropped on the outer peripheral surface of the pipe is formed in the fin 12 without being inhibited from diffusing in the pipe axis direction Y by the fin 12. It is possible to smoothly diffuse in the tube axis direction Y through the recessed portion 14 and to increase heat transfer performance by increasing the wetted area.
Note that such a cooling system is typically used in the cooling of office buildings and the like as described above, and there is a small system such as a convenience store. Some systems are large.

  Specifically, as described above, according to the heat transfer tube 11 of the first embodiment, the ratio (La / Lb) of the length of the convex portion 13 to the concave portion 14 is in the range of 0.25 to 1. Forming.

Thus, the reason why the ratio (La / Lb) of the length of the convex portion 13 to the concave portion 14 is formed within the range of 0.25 to 1 is that this ratio (La / Lb) is less than 0.25. In other words, when the length of the fin 12 in the length direction of the concave portion 14 with respect to the convex portion 13 is extremely long, the area of the fin 12 is too small to obtain a sufficient heat transfer effect (heat radiation effect). Because.
On the contrary, when the ratio (La / Lb) exceeds 1, the length of the fin 12 in the concave portion 14 with respect to the convex portion 13 is shortened, and the dropped water is sufficiently diffused in the tube axis direction Y. It is because it cannot be done.

  As described above, according to the heat transfer tube 11 of the first embodiment, the concave portion 14 and the convex portion 13 are repeatedly formed in the reverse direction along the length direction of the fin 12, and the concave portion 14 and the convex portion 13 are formed. The repetitive pitch (P) with the portion 13 is formed within a range of 1.0 mm to 10 mm.

  With the above-described configuration, the plurality of recesses 14 are arranged in a well-balanced manner in the pipe circumferential direction X along the length direction of the fins 12, so that the dropped water diffuses in the pipe circumferential direction X and passes through the recesses 14. Since it diffuses in the axial direction Y, a uniform refrigerant liquid film can be formed on the entire tube.

The reason why the repetitive pitch (P) between the concave portion 14 and the convex portion 13 is formed within a range of 1.0 mm to 10 mm is that when the pitch (P) is less than 1.0 mm, the dropped water is This is because it becomes difficult to pass through the recess 14 and cannot be sufficiently diffused in the tube axis direction Y.
On the contrary, when the pitch (P) exceeds 10 mm, the dropped water diffuses in the tube axis direction Y in the concave portion 14, but becomes difficult to diffuse in the tube axis direction Y in the convex portion 13. This is because water is hardly diffused uniformly in the tube axial direction Y in the tube circumferential direction X.

  Further, as described above, according to the heat transfer tube 11 of the first embodiment, the height (H) of the convex portion 13 of the fin 12 with respect to the outer peripheral surface of the tube is formed within a range of 0.2 mm to 0.95 mm. ing.

  The reason why the height (H) of the convex portion 13 of the fin 12 with respect to the pipe outer peripheral surface is formed within the range of 0.2 mm to 0.95 mm is that the height (H) of the convex portion 13 of the fin 12 is 0. If it is less than 2 mm, the area of the fin 12 is excessively reduced, and a sufficient heat transfer effect cannot be obtained. Conversely, if the height (H) of the convex portion 13 of the fin 12 exceeds 0.95 mm, it is difficult to process the fin 12.

  Further, as described above, according to the heat transfer tube 11 of the first embodiment, the concave portion 14 with respect to the fin top portion 12T is formed with a depth (d) in the range of 0.1 mm to 0.8 mm, and at least the It is formed at a height higher than the outer peripheral surface of the tube.

  The reason why the depth (d) of the concave portion 14 with respect to the fin top portion 12T is formed within the range of 0.1 mm to 0.8 mm is that the depth (d) of the concave portion 14 is less than 0.1 mm. This is because it becomes difficult for the water to pass over the recess 14 and the water cannot be sufficiently diffused in the tube axis direction Y.

  Conversely, when the depth (d) of the concave portion 14 exceeds 0.8 mm, the area of the fin 12 is reduced and the heat transfer effect cannot be sufficiently obtained. Further, it is difficult to keep a small amount of the dropped water between the fins 12 in the tube axis direction Y, and it is difficult to form a refrigerant liquid film.

  The reason why the depth (d) of the concave portion 14 with respect to the fin top portion 12T is at least higher than the outer peripheral surface of the tube is that if the depth exceeds the outer peripheral surface of the tube, the refrigerant in the concave portion 14 This is because the thickness of the liquid film becomes too thick and the heat transfer performance decreases.

  Further, as described above, according to the heat transfer tube 11 of the first embodiment, the fin 12 has a cross section of the heat transfer tube 11 cut along the tube axis direction Y within a range of 19 to 50 per inch. It is formed with.

  The reason why the number of fins 12 is formed in the range of 19 to 50 per inch in the tube axis direction Y is that the number of fins 12 is less than 19 per inch in the tube axis direction Y. This is because the area of the fin 12 is excessively reduced and a heat transfer effect cannot be obtained sufficiently. Conversely, if the number of fins 12 exceeds 50 per inch in the tube axis direction Y, fin 12 processing becomes difficult.

(Example)
The heat transfer tube 11 of the present invention used in this example has the same configuration as the heat transfer tube 11 of the first embodiment, and uses a phosphorous deoxidized copper base tube 11 ′ having an outer diameter of φ15.88 mm and a wall thickness of 0.8 mm. Is configured.

A heat transfer tube 101 used as a comparative example of the heat transfer tube 11 of the first embodiment has a configuration as shown in FIGS. That is, in the heat transfer tube 101 used in the comparative example, the convex portion 103 and the concave portion 104 are formed on the fin 102 along the length direction of the fin 102, but the length (La ′) of the convex portion 103. It is the conventional heat exchanger tube which takes the structure formed so that it might become longer than the length (Lb ') of the recessed part 104. FIG.
Further, the heat transfer tube 101 used in the comparative example is configured by using a phosphorus-deoxidized copper base tube having an outer diameter of 15.88 mm and a wall thickness of 0.8 mm, similarly to the heat transfer tube 11 of the first embodiment.
8A and 8B are a partial front view of a conventional heat transfer tube 101 used in the comparative example and a perspective view in which a part of the outer peripheral portion is developed.

For each of the heat transfer tube 11 of the first embodiment and the heat transfer tube 101 used in the comparative example, the heat transfer coefficient outside the tube was measured using the test apparatus 24 shown in FIG. 4 under the test conditions shown in Table 1. A comparison was made.
FIG. 4 is a schematic diagram of the test apparatus 24 used in this example.

前記試験装置２４は、図４に示すように、減圧された蒸発器２５内部に蒸発器用伝熱管２６が１列５段に２列配されている。各列の伝熱管２６は相互に連通されている。伝熱管２６の上方に配された冷媒水滴下トレー２７から冷媒水（純水）が滴下され、この冷媒水の蒸発潜熱により伝熱管２６内の水が冷却される。

As shown in FIG. 4, the test apparatus 24 has evaporator heat transfer tubes 26 arranged in two rows in one row and five stages inside the decompressed evaporator 25. The heat transfer tubes 26 in each row are in communication with each other. Refrigerant water (pure water) is dropped from the refrigerant water dropping tray 27 disposed above the heat transfer tube 26, and the water in the heat transfer tube 26 is cooled by the latent heat of evaporation of the refrigerant water.

On the other hand, the absorber heat transfer tubes 29 are arranged in one row and five stages inside the depressurized absorber 28. The heat transfer tubes 29 are in communication with each other. Absorbing liquid (lithium bromide aqueous solution) is sprayed from the spray pipe 35 on the surface of the heat transfer tube 29, and the vapor generated in the evaporator 25 is absorbed by the absorbing liquid. Cooling water is allowed to flow inside the absorber heat transfer tube 29 to cool the absorbing liquid, thereby improving the absorption efficiency of the vapor.
The absorption liquid diluted by absorbing the vapor is transferred from the absorption liquid storage tank 36 to the absorption liquid adjustment tank 37, and after the concentration is adjusted here, the pump 38 can be circulated to the spray pipe 35.

  As the evaporator heat transfer tube 26 in the test device 24, the heat transfer tube 11 of the first embodiment and the heat transfer tube 101 used in the comparative example are separately incorporated, and the refrigerant flow rate is 1.0 liter / m · min. Table 2 shows the results of measuring the external heat transfer coefficient of each tube.

なお、表２にはフィン１２および凹部１４の寸法などを併記した。第１実施形態の伝熱管１１の管外熱伝達率は、比較例として用いた伝熱管１０１の管外熱伝達率を１００としたときの比率で表した。

Table 2 also shows the dimensions of the fins 12 and the recesses 14. The external heat transfer coefficient of the heat transfer tube 11 of the first embodiment is expressed as a ratio when the external heat transfer coefficient of the heat transfer tube 101 used as the comparative example is 100.

Furthermore, about the heat exchanger tube 11 of 1st Embodiment, and the heat exchanger tube 101 used by the comparative example, a refrigerant | coolant flow volume is 0.6-2.8 liter / m * min. FIG. 5 shows the result of calculating the heat transfer coefficient outside the tube when various changes are made in the above range.
As is apparent from Table 2 and FIG. 5, the heat transfer tube 11 of the first embodiment has a refrigerant flow rate of 1.5 liters / m · min. Compared to the heat transfer tube 101 used in the comparative example. In addition to the above, high external heat transfer coefficient was shown at all refrigerant water flow rates, and the effectiveness of the heat transfer tube 11 of the first embodiment was clarified by this example.

Further, the heat transfer tube of the present invention is not limited to the form of the heat transfer tube 11 of the first embodiment described above, and can be configured by other embodiments.
Below, although the heat exchanger tube of other embodiment in this invention is demonstrated, about the structure similar to the heat exchanger tube 11 of 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
For example, the heat transfer tube 11 of the first embodiment is not limited to being used as the evaporator heat transfer tube 26 as in the above-described example, but can also be applied to the absorber heat transfer tube 29. Absorbing liquid such as a lithium bromide aqueous solution dropped on the outer peripheral surface of the absorber heat transfer tube 29 can be easily diffused in the tube axis direction Y through the recesses 14 formed in the fins 12.

  Therefore, the absorbing liquid actively absorbs the vapor and can be quickly cooled by the cooling water flowing in the absorber heat transfer tube 29 even if the temperature rises.

  The heat transfer tube of the present invention is not limited to using the element tube 11 ′ of the phosphorous deoxidized copper tube like the heat transfer tube 11 of the first embodiment, but may be copper, a copper alloy, or other metal having good thermal conductivity. You may comprise using the raw material pipe | tube of another material.

(Second Embodiment)
As in the heat transfer tube 11 in the first embodiment, the heat transfer tube in the second embodiment is formed by repeatedly forming convex portions and concave portions in the fin along the length direction of the fin.
However, although not shown, the convex portion in the second embodiment is stepped with a portion having a height corresponding to the top of the fin and a portion lower than the top of the fin and higher than the recess. Is formed.

  Even in the above configuration, since the length of the convex portion along the length direction of the fin is less than or equal to the length of the concave portion, water is diffused in the tube axis direction Y, and the heat transfer coefficient outside the tube is increased. Can be improved.

(Third embodiment)
As shown in FIG. 6, the heat transfer tube 31 in the third embodiment is formed in a spiral shape so that two types of fins 12 (12a, 12b) having different heights (H1, H2) with respect to the outer peripheral surface of the tube are mixed. Yes.
In addition, FIG. 6 shows the partial front view of the heat exchanger tube 31 in 3rd Embodiment.

  Specifically, the heat transfer tube 31 according to the third embodiment includes a kind of fins 12a on the side (H1) having a high height relative to the pipe outer peripheral surface, and a side having a height lower than the type of fin 12a on the pipe outer peripheral surface. (H2) The other types of fins 12b are alternately arranged along the tube axis direction Y at a ratio of 1: 2.

And the convex part 13 and the recessed part 14 are formed only in the kind of fin 12a along the length direction. Furthermore, the convex part 13 and the said recessed part 14 form the length of the convex part 13 below the length of the recessed part 14 similarly to the heat exchanger tube 11 of 1st Embodiment, and the space | interval of the said adjacent convex parts 13 is formed. , 1.0 mm to 10 mm.
ing.

  The heat transfer tube 31 in the third embodiment is formed to have a high height with respect to the outer peripheral surface of the tube like a kind of fins 12a. Therefore, the area of the fin 12 can be increased as compared with the case where all the fins 12 are formed of other types of fins 12b, and water is diffused in the tube axis direction Y through the recesses 14 of the kind of fins 12a. And the entire outer peripheral surface of the tube can be wetted.

  Therefore, the external heat transfer coefficient of the heat transfer tube 31 in the third embodiment can be improved.

  The heat transfer tube in the present invention is not limited to the above-described configuration. For example, although not shown, the other types of fins 12b on the lower side (H2) are also provided with convex portions 13 and concave portions along the length direction of the fins 12b. 14 may be formed, and the pitch of the convex portion 13 and the concave portion 14 may be formed with different lengths in each of the one type of fin 12a and the other type of fin 12b.

  Furthermore, as described above, the fins 12a and 12b having different heights (H1, H2) are not limited to two types, and three or more types of fins 12 having different heights are mixed. Or may be mixed at any ratio along the tube axis direction Y.

(Fourth embodiment)
As shown in FIGS. 7A and 7B, the heat transfer tube 41 in the fourth embodiment has a large number of convex ridges 43 (linear protrusions) formed in a spiral shape on the inner peripheral surface thereof.
7A and 7B are a transverse sectional view and a longitudinal sectional view showing an example of the convex ridge 43 formed on the inner surface of the heat transfer tube 11 in the fourth embodiment, respectively.

  Further, the convex ridge 43 is processed by a rolling method before processing the fin 12 on the outer peripheral surface of the raw tube, and has a ridge number of 30 in the cross section, a ridge twist angle of 46 °, and a ridge height of 0.2 mm. Forming.

As described above, the heat transfer tube 41 according to the fourth embodiment does not have the convex ridges 43 formed on the inner peripheral surface as shown in Table 3 because the convex ridges 43 are formed on the inner peripheral surface. Compared with the heat transfer tube, the turbulent flow of the refrigerant flowing in the tube is promoted, the heat transfer area on the inner surface of the tube is increased, and the heat passing rate K is improved. Furthermore, by forming the fin 12 having the convex portion 13 and the concave portion 14 on the outer peripheral surface of the tube, the heat transfer coefficient outside the tube can be further improved.
Table 3 is a table showing the difference in the heat transfer rate K depending on the presence or absence of the ridge in the tube. The heat transfer rate K of the heat transfer tube 41 of the fourth embodiment is the heat of the heat transfer tube without a ridge used as a comparative example. Expressed as a ratio when the pass rate is 100.
Here, the heat transfer rate K is a value that takes into account the effects of both the heat transfer coefficient outside the tube and the heat transfer rate inside the tube, and the larger the value, the higher the heat transfer performance of the heat transfer tube. The definition of the heat transfer rate K is expressed by the following equation.

Structure explanatory drawing of the heat exchanger tube in 1st Embodiment. Structure explanatory drawing of the heat exchanger tube in 1st Embodiment. Process explanatory drawing which shows the example of the manufacturing method of the heat exchanger tube in 1st Embodiment. Explanatory drawing of the apparatus used for the measurement of the heat transfer performance of the heat exchanger tube in 1st Embodiment. The comparison explanatory drawing of the heat exchanger tube in 1st Embodiment, and the conventional heat exchanger tube in the heat transfer coefficient outside a tube when changing coolant water flow volume. The partial front view of the heat exchanger tube in 3rd Embodiment. The partial front view of the heat exchanger tube in 4th Embodiment. Structure explanatory drawing of the conventional heat exchanger tube.

Explanation of symbols

11, 31, 41 ... Heat transfer tube 12, 12a, 12b ... Fin 13 ... Convex part 14 ... Concave part 12T ... Fin top part

Claims (6)

A heat transfer tube in which a fin protruding in a spiral shape from the outer peripheral surface of the tube is formed, and a convex portion and a concave portion are repeatedly formed in the fin direction along the length direction of the fin,
The length of the convex portion is
Formed below the length of the recess,
The interval between the adjacent convex portions is
A heat transfer tube formed within a range of 1.0 mm to 10 mm. The ratio of the length of the convex part to the concave part,
The heat transfer tube according to claim 1, which is formed within a range of 0.25 to 1. Repetitive pitch between the convex part and the concave part is
The heat transfer tube according to claim 1, wherein the heat transfer tube is formed within a range of 1.0 mm to 10 mm. The height of the convex portion of the fin with respect to the outer peripheral surface of the tube,
The heat transfer tube according to any one of claims 1 to 3, wherein the heat transfer tube is formed within a range of 0.2 mm to 0.95 mm. The recess relative to the fin top,
The heat transfer tube according to any one of claims 1 to 4, wherein the heat transfer tube is formed at a depth within a range of 0.1 mm to 0.8 mm and at least a height equal to or greater than the outer peripheral surface of the tube. The heat transfer tube according to any one of claims 1 to 5, wherein the fin is formed within a range of 19 to 50 sheets per inch in a cross section obtained by cutting the heat transfer tube along the tube axis direction. .

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