JP4823990B2 - Heat transfer tube - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a heat transfer tube used in a heat exchanger, and more particularly to a heat transfer tube used in a heat exchanger for a heat pump water heater that distributes hot water in the tube.

  Various heat transfer devices have been developed to reduce carbon dioxide emissions from the viewpoint of global environmental conservation. Many types of water heaters can obtain hot water by heating water with city gas or oil-based fuel, but by forming a heat cycle by circulating refrigerant with a power-driven compressor The performance of heat pump water heaters that obtain hot water is increasing. Many heat pump water heaters use carbon dioxide instead of chlorofluorocarbon as a refrigerant, which contributes to chlorofluorocarbon removal.

  The heat transfer tube used in the heat exchanger for the heat pump water heater needs to be set to an appropriate water passage cross-sectional area in consideration of the effects of the heat transfer rate and the water flow pressure loss.

  This is because if the water flow path (cross-sectional area) in the heat transfer tube that passes through the heat exchanger is increased, the water flow rate in the heat transfer tube is decreased, and the heat transfer coefficient that affects the performance of the heat exchanger decreases. is there.

  Conversely, if the water flow path (cross-sectional area) is reduced, the flow rate of the water flowing in the heat transfer pipe is increased and the heat transfer coefficient is improved, but the contact area between the water and the heat exchanger is reduced. Only the water flow path of the heat transfer tube needs to be extended.

In this way, when the water flow rate is increased and the water flow path is extended, the water flow pressure loss increases, and as a result, the power of the water flow pump P becomes larger (to that extent, the pump Cost increases due to increased capacity and power consumption of pump P increases).
In consideration of the above points, a gas cooler generally has a copper or copper alloy tube having an outer diameter of about 8.0 to 12.7 mm (thickness is 0.6 to 1.0 mm) as a heat transfer tube for passing water. Often used.
For example, also in the gas cooler disclosed in Patent Document 1, the diameter of the core tube used as the heat transfer tube is set from such a viewpoint.

  However, a sufficient heat transfer coefficient could not be obtained simply by setting the heat transfer tube in the gas cooler to an appropriate water passage cross-sectional area as described above.

  For this reason, in order to improve the heat transfer rate on the water flow side, fins (inner grooved tubes) are provided on the inner wall surface of the heat transfer tubes, and the height of the fins is set as high as possible. It has been clarified that even when it is low (when the Reynolds number is as small as about 3000 to 5000), the heat transfer rate during water flow can be improved and the pressure loss can be suppressed to an appropriate level.

  However, if the number of fins configured to be as high as possible on the inner surface of the tube is increased, the necessary material per unit length increases, and the weight of the tube increases.

Conversely, when forming fins on the inner surface of the tube, if the number of fins configured in the circumferential direction of the inner surface of the tube is reduced, the heat transfer tube is buckled and fins cannot be processed on the inner surface of the tube.
JP 2002-228370 A

  Therefore, the object of the present invention is to provide a high yield and a material with the premise that it can be effectively used for a heat exchanger such as a gas cooler of a heat pump water heater, where it is difficult to improve heat transfer performance and optimize pressure loss. The purpose of the present invention is to provide a heat transfer tube that can reduce the weight of the tube through effective use and has high heat transfer performance.

According to the present invention, while the pressing tool provided on the outer side of the pipe revolves in the pipe circumferential direction, the raw pipe made of copper or a copper alloy pipe is pressed toward the grooved plug provided on the inner side of the pipe, and the outer periphery of the grooved plug is By rolling the groove to the inner surface of the tube , the outer diameter is in the range of 8.0 mm to 12.7 mm, the wall thickness is in the range of 0.6 to 1.0 mm, and the tube inner surface is A heat transfer tube in which a plurality of helical fins are formed over the entire circumference, wherein the fin is composed of a first fin and a second fin having a height lower than the first fin, The fins are set to a height in the range of 0.5 to 1.0 mm, and are disposed at the same pitch in the circumferential direction of the inner surface of the tube, and the second fin is set to a height of 0. 1 of the height of the first fin. Press to set the height within a range of 1 to 0.5 times and press the second fin with the pressing tool. Characterized in that arranged at the same pitch between every portion of the variation in the tube circumferential direction is first fin unformed portion increases with respect to the first fin-forming portion of the first fin to each other.

  As an aspect of the present invention, a first corner which is a corner between the bottom of the first fin and the inner surface of the tube, and a second corner which is a corner of the bottom of the second fin and the inner surface of the tube Each of the parts is configured with a cross-sectional arc shape, and the radius of curvature of the first corner is set to a size within a range of 0.08 to 0.12 times the height of the first fin. The radius of curvature of the second corner can be set to a size within a range of 0.08 to 0.12 times the height of the second fin.

  As described above, turbulent flow promotion during water flow is achieved by forming two types of fins having different heights, the first fin and the second fin lower than the first fin, on the pipe inner surface. And excellent heat transfer performance can be obtained.

  In particular, by setting the height of the first fin to 0.5 mm or more, high-performance heat transfer performance can be maintained even in a portion where water having a water temperature of, for example, about 10 degrees flows in the pipe.

In addition, the height of the first fin is configured to be 1.0 mm or less, and the height of the second fin is configured to be 0.5 times or less the height of the first fin, so that all the fins are unnecessarily high. It is possible to prevent the loss and to reduce the amount of necessary material. Therefore, it is possible to reduce the weight and reduce the cost.
Thus, by setting the height of the first fin to 1.0 mm or less, the fin does not become too high, so that the fin can be processed reliably.

  In particular, as described above, the height of the first fin can be set within a range of 0.5 to 1.0 mm, but is preferably set within a range of 0.5 to 0.8 mm. It is more desirable to set within the range of 0.55 to 0.7 mm. This is because as the height of the first fin increases, adjustment of pressure loss and difficulty of processing increase.

Further, by configuring the height of the second fin to be not less than 0.1 times the height of the first fin, it is possible to prevent the heat transfer tube from buckling during processing.
Specifically, when the height of the second fin is configured to be not more than 0.1 times the height of the first fin, the second fin is too low and the fin forming portion in the circumferential direction is substantially the first fin. As a result, the distance between the fins in the circumferential direction becomes longer.

  For this reason, when rolling the groove of the grooved plug, the fluctuation of the pressing force of the processed ball against the heat transfer tube becomes large between the fin forming part and the part not forming, which causes the heat transfer tube to buckle during processing. However, as described above, a plurality of spiral fins are provided on the inner surface of the tube over the entire circumference of the tube, and the height of the second fin is set to 0.1 of the height of the first fin. By constructing with more than twice, buckling of the heat transfer tube can be prevented during processing.

  In particular, as described above, the height of the second fin can be set within a range of 0.1 to 0.5 times the height of the first fin, but the height of the first fin is 0.1. It is desirable to set within a range of ˜0.3 times, and it is more desirable to set within a range of 0.15 to 0.25 times.

  By configuring the height of the second fin with the above-described setting, the effects of providing the second fin, such as promoting turbulent flow during water flow, preventing buckling, and reducing the weight, can be significantly achieved. .

  Further, as an aspect of the present invention, the first fin and the second fin are alternately arranged at the same pitch in the circumferential direction of the pipe inner surface, so that the pipe axial direction and the entire pipe circumferential direction are provided. In addition, even more uniform and high-performance heat transfer performance can be obtained, and buckling can be prevented during fin processing.

  In addition, as an aspect of the present invention, a first corner that is a corner between the bottom of the first fin and the inner surface of the pipe, and a second corner that is a corner between the bottom of the second fin and the inner surface of the pipe. By constituting the corner portions with curved surfaces, it is possible to reduce the adhesion of scale due to long-term use of the gas cooler.

  As an aspect of the present invention, each of the first corner portion and the second corner portion is formed in a cross-sectional arc shape, and the curvature radius of the first corner portion is set to the height of the first fin. By setting the radius of curvature of the second corner portion to 0.06 times or more the height of the second fin, The amount of scale attached to the portion can be further reduced, and the fin can be formed in an accurate shape that is easy to process during fin processing.

  Further, the radius of curvature of the first corner is set to a size of 0.15 times or less the height of the first fin, and the radius of curvature of the second corner is set to the second radius. By setting the size to 0.15 times or less of the height of the fin, unnecessary materials can be reduced and the increase in the unit length of the pipe can be avoided.

  Further, as described above, the radius of curvature of the first corner can be set to a size within a range of 0.06 to 0.15 times the height of the first fin. It is desirable to set the size within the range of 0.08 to 0.12 times the height, and it is more desirable to set the size within the range of 0.1 to 0.12 times.

  Furthermore, as described above, the radius of curvature of the second corner can be set to a size within a range of 0.06 to 0.15 times the height of the second fin. It is desirable to set the size within a range of 0.08 to 0.12 times the height of the height, and it is more desirable to set the size within a range of 0.1 to 0.12 times.

  Thus, the radius of curvature of the first corner and the radius of curvature of the second corner are 0 with respect to the height of the first fin and the height of the second fin, respectively. From the viewpoint of reducing the amount of scale and improving the workability of the fins as described above, it is particularly preferable that it is about 1 time or slightly larger.

  The cross-sectional arc shape indicates that a shape obtained by a cross section perpendicular to the direction of fin formation in each of the first corner portion and the second corner portion is an arc shape.

  In addition, the curved surface shape includes a curved shape obtained by cross-sectionally viewing the first even angle portion or the second even angle portion is a curved shape formed by an arc shape, a relaxed curve shape, or a clothoid shape. Further, the radius of curvature indicates a radius of curvature obtained in a cross section perpendicular to the fin forming direction.

  According to the present invention, it is possible to provide a heat transfer tube that can reduce the weight of the tube by high yield and effective use of materials and that has high heat transfer performance.

An embodiment of the present invention will be described below with reference to the drawings.
As shown in FIGS. 1, 2, and 3, the heat transfer tube 11 in this embodiment includes a large number of helical fins 12 (23, 24) protruding from the tube inner surface 10 in the tube axis direction. .

  1 is a cross-sectional view showing a part of the heat transfer tube 11 of the present embodiment cut at right angles to the tube axis direction, and FIG. 2 is a view of the heat transfer tube 11 of the present embodiment cut in the tube axis direction. It is sectional drawing which shows a part which did. FIG. 3 is a cross-sectional view of a plane passing through the central axis of the tube.

  The plurality of fins 12 are configured over the entire circumference of the pipe, and are configured by first fins 23 and second fins 24 having a height lower than that of the first fins 23. The height H1 of the first fin 23 is set to 0.7 mm, which is in the range of 0.5 to 1.0 mm, and the height H2 of the second fin 24 is the height of the first fin 23. Is set to 0.2 mm, which is within a range of 0.1 to 0.5 times.

  In the heat transfer tube 11 in the present embodiment, the first fins 23 and the second fins 24 are alternately arranged at the same pitch p in the circumferential direction of the tube inner surface 10.

  Furthermore, the heat transfer tube 11 of the present embodiment includes a first corner portion 26 that is a corner portion 25 (26, 27) between the bottom portion 23a of the first fin 23 and the tube inner surface 10, and the second fin 24. The second corner portion 27, which is the corner portion 25 between the bottom portion 24a of the tube and the inner surface 10 of the tube, is configured by a curved surface having a circular arc shape in cross section.

  The radius of curvature R (R1, R2) of the corner 25 is 0.06 to 0.15 times the radius of curvature R1 of the first corner 26 than the height H1 of the first fin 23. And the radius of curvature R2 of the second corner portion 27 is within a range of 0.06 to 0.15 times the height H2 of the second fin 24. The size is set to 0.03 mm.

  More specifically, the heat transfer tube 11 of this embodiment is made of phosphorous deoxidized copper. As shown in FIG. 1, the outer diameter Do is 9.52 mm, the wall thickness t is 0.75 mm, and the inner diameter Di is 8. As shown in FIG. 3, the twist angle β of the fin 12 with respect to the tube axis direction is 44 degrees.

The heat transfer tube having the above configuration is used in a heat exchanger of a heat pump water heater.
The heat pump water heater is generally configured by a system as shown in FIG.
FIG. 8 is a system flow diagram of the heat pump water heater 37.

  In the heat pump water heater 37, the high-temperature and high-pressure refrigerant from the compressor 41 is sent to a heat exchanger 43 called a gas cooler, and the heat exchanger 43 exchanges heat with tap water flowing in the heat transfer pipe 11. It is possible to obtain hot water for use in. The refrigerant whose temperature has been lowered by the gas cooler 43 is reduced in pressure by the expansion valve 45, is vaporized by the outside air in the evaporator 46 installed outside the room, and is again increased in temperature and pressure by the compressor 41.

  In such a heat pump water heater 37, hot water boiled by using low-night power set at low cost in order to equalize the amount of electric power used is stored in a hot water storage tank 47, and the day of the next day. Some use hot water in the hot water storage tank 47.

  Specifically, since 300 to 500 L of hot water at 65 to 90 ° C. is stored in the hot water storage tank 47 over about 6 hours, the gas cooler 43 is approximately 0.8 to 1.4 L / min. Tap water is supplied to the extent.

  In the heat pump water heater 37, it is difficult to optimize the heat transfer coefficient and water flow pressure loss of the gas cooler 43. By using the heat transfer tube 11 of the present embodiment in the gas cooler 43, the following effects are obtained: An effect can be obtained.

  As described above, the heat transfer tube 11 of the present embodiment includes two types of fins having different heights of the first fin 23 and the second fin 24 lower than the first fin 23 on the tube inner surface 23. Therefore, it is possible to promote turbulent flow during water flow. Therefore, as shown in FIG. 9, the pipe inner surface 100 is provided with only one type of fin 102 having the same height as the first fin 23 by the total number of fins of the first fin 23 and the second fin 24. Compared to the conventional heat transfer tube 101A, excellent heat transfer performance can be obtained.

In addition, the weight of the tube can be reduced by using the material effectively, and the cost can be reduced.
Specifically, although it depends on the fin shape, the weight can be reduced by about 3 to 10%.

  Further, the heat transfer tube of the present embodiment is not configured to reduce the number of fins in order to reduce the weight of the tube, but the second fin 24 is configured along the entire circumference of the tube together with the first fin 23 by the amount of fins to be reduced. By doing so, buckling can be prevented during fin processing, and manufacturing can be performed with a high yield.

  Furthermore, in the heat transfer tube 11 of the present embodiment, the first corner portion 26 and the second corner portion 27 are both formed in a curved shape, so that the scale adheres when the gas cooler is used for a long period of time. Can be reduced.

Next, an experiment conducted to compare the performance of the heat transfer tubes 11 having the above-described configuration will be described. In the experiment, two experiments, a processing experiment and a heat transfer experiment, were performed. In any experiment, Example 1 shown in Table 1 below using the number of fins N (N1, N2), the fin height H (H1, H2), and the radius of curvature R (R1, R2) of the corner 25 as parameters. 6 types of heat transfer tubes 11 to 6 were made, and heat transfer tubes of Comparative Examples 1 to 6 used as comparative controls were made.
Note that the heat transfer tubes of Comparative Examples 1 to 6 are all conventional heat transfer tubes. In particular, Comparative Examples 1 and 2 are conventional heat transfer tubes having one type of fins having the same height on the inner surface of the tube. In particular, Comparative Example 1 is a heat transfer tube 101 </ b> A provided with a large number of fins 102 in the circumferential direction on the tube inner surface 100, as shown in FIG. 9.

前記加工実験は、図４（ａ）に示すような内面溝付管の加工装置２８を用いて行った。
ここで、前記加工装置２８の構成について簡単に説明しておく。
内面溝付管の加工装置２８は、素管１１ａを縮径するダイス３２を備え、該ダイス３２部分において回動自在に係合したフローティングプラグ３３を備えている。

The machining experiment was performed using a machining device 28 for an internally grooved tube as shown in FIG.
Here, the configuration of the processing device 28 will be briefly described.
The inner grooved tube processing device 28 includes a die 32 for reducing the diameter of the base tube 11a, and a floating plug 33 that is rotatably engaged at the die 32 portion.

  In addition, the downstream side of the floating plug 33 is connected to the floating plug 33 through the connecting rod 31 so as to be rotatable independently of the floating plug 33, and a plurality of spiral grooves 34a are formed on the outer periphery thereof as shown in FIG. A grooved plug 34 as shown is provided.

Further, the groove processing device 28 is provided with three balls 35 on the outer peripheral side of the raw tube 11a, and these balls 35 are rotatable around the tube axis while being pressed to the grooved plug 34 side outside the raw tube 11a. It is arranged.
Finally, a tool called a diameter adjusting die 36 is passed through to finish the tube with a desired outer diameter.

  The processing device 28 is configured to pull a large number of parallel spiral fins 12 on the inner peripheral surface of the raw tube 11a by pulling the raw tube 11a in the drawing direction X and pressing the plurality of balls 35 toward the grooved plug 34 side. Can be formed.

Further, in this processing experiment, the heat transfer tubes 11 of Examples 1 to 6 and the heat transfer tubes of Comparative Examples 1 to 6 are both material tubes (elements) having an outer diameter of 14 mm and a wall thickness of 1.0 mm. Tube), the revolution number of the three balls 35 provided in the processing device 28 is set to 8000 rpm, and the drawing speed is set to 5 to 10 m / min. The target was to draw a length of 1000 m and process each into a heat transfer tube as shown in Table 1.
As a result, first, paying attention to the drawing length, as shown in Table 2, all the heat transfer tubes 11 of Examples 1 to 6 were able to be drawn as long as 1000 m as intended.

実施例１から６までの伝熱管１１は、図５に示すように、管内面１０に溝付プラグ３４の溝３４ａを転造する際に、加工ボール３５の伝熱管１１に対する押圧力が、管周方向におけるフィン形成部分と形成していない部分とにおいて変動することを抑制することができるため、加工ボール３５は、材料管の周上を安定して公転する。

As shown in FIG. 5, in the heat transfer tubes 11 of Examples 1 to 6, when the groove 34 a of the grooved plug 34 is rolled on the tube inner surface 10, the pressing force of the processed ball 35 against the heat transfer tube 11 is Since it is possible to suppress fluctuations between the fin-formed portion and the non-formed portion in the circumferential direction, the processed ball 35 stably revolves around the circumference of the material tube.

  For this reason, it is considered that the heat transfer tubes 11 of Examples 1 to 6 were able to process the fins 12 on the tube inner surface 10 without buckling.

On the other hand, the heat transfer tube of Comparative Example 2 buckled and broke when the length of 230 m was pulled out.
This is because the fins on the inner surface of the pipe are all configured at the same height (H1 = 0.60 mm), and the total number of fins in the circumferential direction is the smallest (N1 = 7) compared to other heat transfer tubes. It is thought that it is because it is doing.

  That is, in the case of the heat transfer tube of Comparative Example 2, since the number of fins 102 in the circumferential direction of the tube inner surface 100 is small, the groove 34a of the grooved plug 34 is rolled on the tube inner surface 100 as shown in FIG. When manufacturing, since the pressing force of the processed ball 35 against the heat transfer tube 101B fluctuates greatly between the fin forming portion and the non-formed portion in the tube circumferential direction, as a result, the heat transfer tube 101B of the comparative example 2 is being processed. It is thought that it buckled and broke.

Furthermore, the heat transfer tube of Comparative Example 3 was buckled at the time when the length of 505 m was pulled out, resulting in a fracture.
This is because the height H1 of the higher fin is 1.00 mm, and the height H2 of the lower fin is set to 0.07 mm, which is 0.07 times the height H1 of the higher fin. This is probably because the fin height on the lower side is too low.

  Furthermore, the heat transfer tube of Comparative Example 4 was designed so that the fin height on the high side was the highest H1 = 1.2 mm compared to the other heat transfer tubes, but processing was attempted. Under the conditions, the fin height was too high to process.

  In addition, about the heat exchanger tube 101A of the comparative example 1, only the fin of one kind whose height H1 is 0.60 mm is set to 14 pieces and many fins in the circumferential direction. With this configuration, when the groove 34a of the grooved plug 34 is rolled on the pipe inner surface 100 as in the heat transfer pipe 101A shown in FIG. 10B, the pressing force of the processed ball 35 against the heat transfer pipe 11 is It is possible to suppress fluctuations in the fin forming part and the non-formed part in the direction.

  Therefore, the heat transfer tube 101A of Comparative Example 1 was able to ensure the strength that could withstand buckling, and was able to pull out a length of 1000 m. Thus, only the fin 12 having a high height was used. Since many are configured in the circumferential direction, the amount of material used is greatly increased, and the tube weight and cost are increased.

  Subsequently, focusing on the drawing speed, as shown in Table 3, the heat transfer tube 11 of Example 5 was 10 m / min. However, the heat transfer tube 11 of Example 3 and Example 4 was 7 m / min. Even at a drawing speed of, work breakage occurred.

  As shown in Table 3 below, the heat transfer tubes 11 of Examples 1 to 3 have the same number of fins N1, N2 and fin heights H1, H2, but the corner portions 25 (26, It is considered that the difference in the radii of curvatures R1 and R2 in (27) causes a difference in the strength of the fins 12 and the work breaks depending on the drawing speed.

具体的には、実施例５の伝熱管１１は、第１隅角部２６の曲率半径Ｒ１を、第１フィン２３の高さ（Ｈ１＝０．７０ｍｍ）の０．０６倍以上の大きさである０．０７ｍｍに設定しているからであり、第２隅角部２７の曲率半径Ｒ２を、第２フィン２４の高さ（Ｈ２＝０．２０ｍｍ）の０．０６倍以上の大きさである０．０３ｍｍに設定しているからであると考えられる。

Specifically, in the heat transfer tube 11 of the fifth embodiment, the radius of curvature R1 of the first corner portion 26 is 0.06 times the height of the first fin 23 (H1 = 0.70 mm) or more. This is because the radius of curvature R2 of the second corner portion 27 is 0.06 times or more the height of the second fin 24 (H2 = 0.20 mm). This is considered to be because it is set to 0.03 mm.

  On the other hand, in the heat transfer tube 11 of the third embodiment, the curvature radius R1 of the first corner portion 26 is set to 0.04 mm, which is smaller than the respective curvature radii of the heat transfer tubes 11 of the fourth and fifth embodiments. In the heat transfer tube 11 of the fourth embodiment, the curvature radius R2 of the second corner portion 27 is set to 0.01 mm, which is smaller than the respective curvature radii of the heat transfer tubes 11 of the third and fifth embodiments. It is thought that.

  Further, in the heat transfer tube of the present invention, like the heat transfer tube 11 of the fifth embodiment, the radius of curvature R1 of the first corner portion 26 is not more than 0.15 times the height of the first fin 23. In addition, the radius of curvature R2 of the second corner portion 27 can be configured to be not more than 0.15 times the height of the second fin 24.

  With the above configuration, the amount of scale attached to the corner portion 25 can be further reduced. Furthermore, the fin 12 having the above-described configuration has a shape that can be easily processed at the time of processing, can reduce unnecessary materials for processing, and can avoid an increase in the weight of the unit length tube.

Next, a heat transfer experiment for evaluating the heat transfer performance of the heat transfer tubes 11 of Examples 1 to 6 was performed.
In the heat transfer experiment, for each of the heat transfer tubes 11 of Examples 1 to 6 and the heat transfer tubes of Comparative Examples 1 to 5 created in the above-described processing experiment, an experimental apparatus 50 as shown in FIG. The heat transfer performance was evaluated.

The experimental apparatus 50 includes a test tube 51 to be measured, and an annular portion that is disposed on the outer peripheral side of a predetermined portion in the length direction of the test tube 51 and includes a high-temperature water inlet 53 and a high-temperature water outlet 54. And a device called a double-pipe heat exchanger with 52 is used.
The tube inner diameter of the annular portion 52 is 16.7 mm.

In the experimental device 50, the thermometer T is installed on the high temperature water inlet 53 side and the high temperature water outlet 54 side of the annular portion 52, and on the upstream side with respect to the arrangement portion of the annular portion 52 in the tube axis direction of the test tube 51. And on the downstream side.
Furthermore, the flow meter F is installed downstream of the annular portion 52 on the high temperature water outlet 54 side and the arrangement portion of the annular portion 52 in the tube axis direction of the test tube 51.

In the annular portion 52, water of about 30 degrees (high temperature side) is supplied at a flow rate of 30 L / min. (Reynolds number: ReL≈30000), and circulate from the hot water inlet 53 side to the hot water outlet 54 side. In the test tube 51, water at about 10 ° C. (low temperature side) is supplied at a flow rate of 0.5 to 3.0 L / min. (ReL≈2000-9000, in this experiment, this corresponds to a flow velocity of 0.3-0.9 m / sec), and heat exchange is performed by flowing in the direction opposite to the flow of water in the annular portion 52. went.
As time elapses, the water temperature at the outlet 54 side of the annular portion 52 converges to a predetermined temperature and reaches a steady state, and then the water temperature and flow rate of each portion are measured.

  Based on these measured values, the in-tube heat transfer coefficient αi of the test tube 51 is calculated from the equations (1) and (2), and further, the Nusselt number (hereinafter referred to as the Nu number) by the equation (3). It became dimensionless.

ここで、数式（１）中のｋＨは、高温水側の熱伝導率（ｋＷ／ｍＫ）、ｄｅは、環状部相当直径（ｍ）、ＲｅＨは、高温水側のレイノルズ数（−）、ＰｒＨは、高温水側のプランドル数（−）を示す。
数式（２）中のＡは、伝熱面積（＝Ｄｉ×Ｌ×π）（ｍ２）を示す。但し、Ｌは、伝熱有効長さ（ｍ）を示す。
ΔＴは、対数平均温度差（Ｋ）、ＱＬは、低温度側交換熱量（ｋＷ）、Ｄｏは、供試管５１外径（ｍ）、Ｄｉは、供試管５１最大内径（＝Ｄｏ−２ｔ）（ｍ）を示す。但し、ｔは、供試管５１の底肉厚（ｍ）を示す。
また、数式（３）中のｋＬは、低温水側の熱伝導率（ｋＷ／ｍＫ）を示す。

Here, in Equation (1), kH is the thermal conductivity (kW / mK) on the high temperature water side, de is the annular portion equivalent diameter (m), ReH is the Reynolds number (−) on the high temperature water side, PrH Indicates the number of plan dollars (-) on the high temperature water side.
A in Formula (2) represents a heat transfer area (= Di × L × π) (m2). However, L shows heat transfer effective length (m).
ΔT is the logarithm average temperature difference (K), QL is the low temperature side heat exchange rate (kW), Do is the test tube 51 outer diameter (m), Di is the test tube 51 maximum inner diameter (= Do−2t) ( m). However, t indicates the bottom wall thickness (m) of the test tube 51.
Moreover, kL in Formula (3) shows the thermal conductivity (kW / mK) on the low temperature water side.

  Then, Nu (DG) of the smooth tube inside the tube is expressed by the following Dituss-Beolter equation (4).

ここで、数式（４）中のＲｅＬは、低温水側のレイノルズ数（−）、ＰｒＬは、低温水側のプランドル数（−）を示す。
管内平滑円管のＮｕ（ＤＧ）数に対するＮｕ数の比率となるＮｕ／Ｎｕ（ＤＧ）は、熱伝達率の向上率を示す性能比であり、各伝熱管１１が示すＮｕ／Ｎｕ（ＤＧ）を、表４中に示す。

Here, ReL in Equation (4) indicates the Reynolds number (−) on the low temperature water side, and PrL indicates the Prandle number (−) on the low temperature water side.
Nu / Nu (DG), which is the ratio of the Nu number to the Nu (DG) number of the smooth tube inside the tube, is a performance ratio indicating the improvement rate of the heat transfer coefficient, and Nu / Nu (DG) indicated by each heat transfer tube 11. Are shown in Table 4.

表４に示したように、実施例１から６は、いずれも高いＮｕ／Ｎｕ（ＤＧ）の値を示した。
特に、実施例２から６は、比較例１から５のいずれのＮｕ／Ｎｕ（ＤＧ）の値よりも格段に高い値となった。
なお、表４中のＮｕ／Ｎｕ（ＤＧ）の値は、レイノルズ数が３０００時に比較した値である。

As shown in Table 4, Examples 1 to 6 all showed high Nu / Nu (DG) values.
In particular, Examples 2 to 6 were much higher than any Nu / Nu (DG) values of Comparative Examples 1 to 5.
Note that the value of Nu / Nu (DG) in Table 4 is a value compared with a Reynolds number of 3000.

  Moreover, as shown in Table 4, the heat transfer tube 11 of Example 5 is 0.7 mm in which the height H1 of the first fin 23 is lower than the height H1 of the fin of Comparative Example 2 = 0.8 mm. The effect of turbulent flow at the time of passing water by setting two types of fin heights H1 and H2 of the first fin 23 and the second fin 24 is increased, and Nu / Nu (DG) having a higher value than that of Comparative Example 2. was gotten.

  Moreover, in the heat transfer tube 11 of the fifth embodiment, the sum of the number of fins N1 of the first fins 23 and the number of fins N2 of the second fins 24 is 10 which is the same as the number of fins of the second comparative example. Since the height H1 is set to 0.70 mm, which is lower than the fin height on the higher side in Comparative Example 2, the weight of the tube can be reduced.

  In addition, the heat transfer tube of the comparative example 5 obtained only Nu / Nu (DG) lower than the comparative example 1. This is because, in the heat transfer tube of Comparative Example 5, the height H1 of the fin on the higher side is set to 0.4 mm, which is the lowest compared to the fin height of the other heat transfer tubes, and accordingly, the heat conductivity is increased accordingly. This is thought to be due to the decrease.

As an example of the experimental results, the graph of FIG. 7 shows the relationship of Nu / Nu (DG) with respect to the Reynolds number in Example 6 and Comparative Example 1.
As shown in FIG. 7, the heat transfer tube 11 of Example 6 showed a higher value of Nu / Nu (DG) at all Reynolds numbers tested than the heat transfer tube of Comparative Example 1.

Furthermore, as is clear from the values shown in Table 4 and FIG. 7, in both Example 6 and Comparative Example 1, the Reynolds number was 2500 or more and Nu / Nu (DG) showed a high value. In the heat transfer tube 11 of Example 6, especially when the water temperature was low, that is, when the Reynolds number was low, Nu / Nu (DG) showed a significantly higher value than the heat transfer tube of Comparative Example 1.
From this, it was also clarified that the heat transfer tube 11 of Example 6 has high heat transfer performance and contributes to improvement of the performance of a heat exchanger such as a gas cooler particularly at a low water temperature.

  As a result of the above-described processing experiments and heat transfer experiments, the heat transfer tubes of the present invention as shown in the above-described Examples 1 to 6 achieve cost optimization through high yield and effective use of materials, and It was revealed that high heat transfer performance can be provided.

  Specifically, by setting the height H1 of the first fin 23 to 0.5 mm or more, high-performance heat transfer performance even in a portion where low-temperature water having a water temperature of, for example, about 10 degrees circulates in the pipe. Can be maintained.

  Further, the height H1 of the first fin 23 is configured to be 1.0 mm or less, and the height H2 of the second fin 24 is configured to be 0.5 times or less of the height H1 of the first fin 23. The fins can be prevented from becoming unnecessarily high, and the necessary amount of material can be reduced, so that the weight can be reduced and the cost can be reduced.

  In particular, by setting the height H1 of the first fin 23 to 1.0 mm or less, the fin height does not become too high, so that the fin 12 can be processed reliably.

  Further, as described above, the first fins 23 and the second fins 24 are alternately arranged at the same pitch p in the circumferential direction of the pipe inner surface 10, and the height H2 of the second fins 24 is set as follows. By configuring the first fin 23 to be 0.1 times or more the height H1 of the first fin 23, buckling of the heat transfer tube 11 can be prevented during processing.

  Further, each of the first corner portion 26 and the second corner portion 27 is formed in a cross-sectional arc shape, and the curvature radius R1 of the first corner portion 26 is set to the height H1 of the first fin 23. By setting the radius of curvature R2 of the second corner 27 to 0.06 times or more of the height H2 of the second fin 24, The amount of scale attached to the corner portion 25 can be further reduced, and it can be formed in an accurate shape that is easy to process during fin processing.

  Further, the radius of curvature R1 of the first corner portion 26 is set to 0.15 times or less the height H1 of the first fin 23, and the radius of curvature R2 of the second corner portion 27 is set. By setting the size to 0.15 times or less the height H2 of the second fin 24, it is possible to reduce unnecessary materials in configuring the fin 12 and increase the tube weight per unit length. It can be avoided.

  The heat transfer tube of the present invention is not limited to the heat transfer tube 11 of the first to sixth embodiments, and can be configured in various other configurations.

Sectional drawing which shows a part which cut | disconnected the heat exchanger tube of this embodiment at right angle with respect to the pipe-axis direction. Sectional drawing which shows a part which cut | disconnected the heat exchanger tube of this embodiment in the pipe-axis direction. Sectional drawing in the surface which passes along the pipe axis of the heat exchanger tube of this embodiment. Explanatory drawing (a) of the processing apparatus used for the processing experiment of the heat exchanger tube of this embodiment, and the external view (b) of a grooved plug. Explanatory drawing which shows a mode in the fin formation process of the heat exchanger tube of this embodiment. Explanatory drawing of the apparatus used for the measurement of the heat transfer performance of the heat exchanger tube of this embodiment. The graph which shows the measurement result by this experiment. The system flow figure which shows a heat pump water heater. Structure explanatory drawing of the conventional heat exchanger tube. Explanatory drawing (a) which shows a mode during fin formation processing, Explanatory drawing (b) which shows buckling during fin formation processing.

DESCRIPTION OF SYMBOLS 11 ... Heat-transfer tube 10 ... Pipe inner surface 12 ... Fin 23 ... 1st fin 24 ... 2nd fin 23a, 24a ... Bottom part 25 ... Corner part 26 ... 1st corner part 27 ... 2nd corner part H1 ... 1st fin Height H2 ... height of the second fin R1 ... radius of curvature of the corner of the first fin R2 ... radius of curvature of the corner of the second fin

Claims (2)

While the pressing tool provided on the outer side of the pipe revolves in the pipe circumferential direction, the base pipe made of copper or copper alloy pipe is pressed to the side of the grooved plug provided on the inner side of the pipe, and the outer peripheral groove of the grooved plug is The outer diameter is within the range of 8.0 mm to 12.7 mm, the wall thickness is within the range of 0.6 to 1.0 mm, and the inner surface of the pipe is extended over the entire circumference of the pipe. A heat transfer tube formed with a plurality of spiral fins,
The fins,
It is composed of a first fin and a second fin having a height lower than that of the first fin,
The first fin is set to a height within a range of 0.5 to 1.0 mm, and is arranged at the same pitch in the circumferential direction of the pipe inner surface.
The second fin is set to a height within a range of 0.1 to 0.5 times the height of the first fin;
A portion between the first fins, which is a first fin non-forming portion in which variation in the tube circumferential direction of the pressing force for pressing the second fin against the first fin by the pressing tool is larger than the first fin forming portion. A heat transfer tube characterized by being arranged at the same pitch. Each of the first corner that is the corner between the bottom of the first fin and the inner surface of the tube and the second corner that is the corner of the bottom of the second fin and the inner surface of the tube Consists of arc shape,
The radius of curvature of the first corner is set to a size within a range of 0.08 to 0.12 times the height of the first fin,
2. The heat transfer tube according to claim 1, wherein the radius of curvature of the second corner is set to a size within a range of 0.08 to 0.12 times the height of the second fin. .

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