JP2009186130A - Heat transfer tubes for radiators with internal fins - Google Patents

Abstract

The present invention relates to an internal fin that can suppress a decrease in heat transfer performance even when refrigeration oil is mixed in a refrigerant, and can be reliably processed while suppressing an increase in necessary materials. It aims at providing the heat exchanger tube for an attached radiator.
A heat transfer tube for an internal fin with a fin having a plurality of internal fins on an inner surface of a tube and allowing passage of a CO ₂ refrigerant in an inner portion of the tube, wherein the inner fin is connected to the first inner surface. A fin 21 and second inner fins 22 formed lower than the first inner fin 21 and 22 are formed, and the height H1 of the first inner fin 21 is 0.04 to 0.2 times the pipe inner diameter d. And the height H2 of the second inner surface fin 22 was set to a range of 0.1 to 0.5 times the height H1 of the first inner surface fin 21.
[Selection] Figure 2

Description

  The present invention relates to a heat exchanger tube for a radiator used in a radiator such as a heat pump type water heater using carbon dioxide as a refrigerant.

  Conventionally, CFC refrigerants are circulated to multiple heat exchangers by compressors in home air conditioners (air conditioners), commercial air conditioners (packaged air conditioners), refrigerators, refrigerators, vending machines, or water heaters. Many heat pump type heat cycle devices have been used.

  However, since chlorofluorocarbon refrigerants cause destruction of the ozone layer and global warming, research and development of natural refrigerants, such as carbon dioxide and hydrocarbon refrigerants, have recently been promoted. Practical use is progressing as a heat pump water heater.

And in a heat pump type hot water heater, an inner fin height h is a heat transfer tube used for a heat exchanger, which is a heat transfer tube for a radiator intended for application to a supercritical single phase flow of CO ₂ refrigerant. 0.15 mm or more, the distance g between adjacent inner surface fins is set to h × 0.9 mm or more, the height h of the inner surface fin is set to 0.20 mm or more, and the distance g between adjacent inner surface fins is set to 0.1 mm or more. A heat transfer tube for an internally grooved radiator has been proposed (see Patent Document 1).

However, the condenser-use heat transfer tube with the inner surface grooved, although can be constructed inner surface fin corresponding to CO ₂ refrigerant, when actually used as a heat absorber heat transfer tube is sufficient under the influence of the refrigerating machine oil mixed in the CO ₂ refrigerant A heat transfer effect could not be obtained.

This is disclosed in Non-Patent Documents 1 and 2 which refer to the promotion of cooling heat transfer coefficient in a pipe when supercritical CO ₂ is used as a refrigerant inside a bare pipe (inner smooth pipe) and an inner grooved pipe. As described above, it is considered that the mixing of the refrigerating machine oil in the CO ₂ refrigerant causes the heat transfer coefficient in the pipe to decrease by about 50% at the maximum, and the pressure loss increases by about 1.6 times at the maximum.

  As described above, the refrigerant oil is mixed in the refrigerant and the pressure loss in the heat transfer tube increases, so that the energy consumption of the compressor for flowing the refrigerant increases and the performance of the entire heat exchanger is degraded. For this reason, suppressing the influence of refrigeration oil as much as possible is an issue for improving the performance of the heat exchanger.

  In order to increase the heat transfer coefficient in the heat exchanger tubes for heat exchangers, measures such as increasing the height of the inner fins and increasing the number of inner fins can be considered, but the height of the inner fins should be as high as possible. Increasing the number of inner fins required increases the amount of material required, leading to an increase in the weight of the tube and an increase in material costs during manufacturing.

JP 2007-178115 A Li Sobu, 5 others, "Experimental research on cooling heat transfer in the supercritical region of natural refrigerant CO2", "Copper and copper alloy", "Japan Copper and Brass Association", 2006, Vol. 45, No. 1 No., p. 42-47 Shinya Higashi Inoue and three others, “Effect of refrigeration oil on CO2 grooved pipe cooling heat transfer and pressure loss characteristics in supercritical pressure region”, “Proceedings of Annual Conference of Japan Society of Refrigerating and Air Conditioning Engineers 2007”, “ Japan Society of Refrigerating and Air Conditioning ", 2007, p. 245-248

  This invention is for a radiator with an internal fin that can suppress a decrease in heat transfer performance and can be reliably processed while suppressing an increase in necessary materials even when refrigeration oil is mixed in the refrigerant. The purpose is to provide a heat transfer tube.

  The present invention is a heat transfer pipe for a radiator with an internal fin that has a plurality of internal fins on the inner surface of the tube and allows passage of refrigerant inside the tube, wherein the inner surface fin includes the first inner surface fin and the first inner surface fin. And a second inner surface fin having a height lower than that of the fin, the height of the first inner surface fin is set in a range of 0.04 to 0.2 times the inner diameter of the pipe, and the second inner surface fin The height is set in a range of 0.1 to 0.5 times the height of the first inner fin.

  As an aspect of the present invention, an interval between the adjacent inner surface fins is set to be 0.9 times or more of a height of the second inner surface fin, and an interval between the first inner surface fins is set to the first inner surface fin. It can be set to more than 3 times the height.

As an aspect of the present invention, the apex angle of the first inner fin can be formed larger in the range of 10 to 22 degrees than the apex angle of the second inner fin.
As an aspect of the present invention, the apex angle of the first inner fin can be set in the range of 18 to 30 degrees, and the apex angle of the second inner fin can be set in the range of 8 to 15 degrees.

Further, as an aspect of the present invention, the corner portion between the bottom portion of the inner fin and the inner surface of the pipe can be formed in a curved shape.
Further, as an aspect of the present invention, the corner portion is configured in a circular arc shape having a predetermined radius of curvature, and the radius of curvature of the corner portion of the first inner fin is defined as the corner portion of the second inner fin. It can be formed larger than the radius of curvature of 0.01 to 0.1 mm.

As in the heat transfer tube for a radiator with an internal fin according to the present invention, the internal fin is composed of a first internal fin and a second internal fin formed lower in height than the first internal fin, and the first internal surface The height of the fin is set in a range of 0.04 to 0.2 times the inner diameter of the pipe, and the height of the second inner fin is 0.1 to 0.5 times the height of the first inner fin. By setting to this range, for example, refrigerating machine oil having a surface tension larger than that of a refrigerant such as carbon dioxide can be induced to flow in the vicinity of the second inner surface fin, and the refrigerating machine oil can be separated from the refrigerant.
Furthermore, by forming two types of inner fins having different heights, turbulent flow in the pipe can be promoted and heat transfer performance can be improved.

  In addition, by setting the height of the first inner surface fin to 0.04 or more of the inner diameter of the tube, the first inner surface is high enough to sufficiently stir the refrigerant that becomes a single-phase flow state in the supercritical region during heat dissipation. Fins can be formed.

  Further, for example, when the height of the first inner fin is set to 0.2 times or more of the inner diameter of the tube, it is difficult to process the first inner fin. By setting it to 0.2 times or less, a reliable first inner fin can be formed.

  Furthermore, the height of the second inner fin is set in the range of 0.1 to 0.5 times the height of the first inner fin, thereby preventing all the inner fins from becoming unnecessarily high. In addition, since the amount of necessary material can be reduced, the material cost of the pipe can be reduced, and the effect of having two types of inner fins with different heights can be obtained.

  That is, the refrigeration oil separated from the refrigerant is guided to the second inner fin having a low height, and the refrigerant separated from the refrigeration oil and the first inner fin having a high height are actively contacted to exchange heat. The performance can be improved. Therefore, an increase in pressure loss can be suppressed and an increase in the load on the compressor can be prevented as compared with the case where all the inner surface fins are set to the same height while improving the heat transfer performance.

The interval between adjacent inner fins is set to 0.9 times or more the height of the second inner fin, and the interval between the first inner fins is set to 3 of the height of the first inner fin. By setting it to be twice or more, it is possible to secure the gap between the inner fins and prevent the refrigerating machine oil once separated from the refrigerant from being mixed with the refrigerant again.
Therefore, it is possible to prevent the refrigeration oil mixed in the refrigerant from adhering to the inner surface of the pipe and reducing the heat transfer area, and to further improve the heat transfer performance of the heat transfer pipe for an internally finned radiator.

  Further, by forming the apex angle of the first inner fin in a range of 10 to 22 degrees larger than the apex angle of the second inner fin, the second inner fin having a small apex angle of the refrigerating machine oil mixed in the refrigerant. It is possible to make it easier to flow through the corners.

  Specifically, the angle of the corner formed by the bottom of the second inner fin having a small apex angle and the inner surface of the tube is smaller than the angle of the corner of the first inner fin having a large apex angle. Thereby, for example, the refrigerating machine oil having a larger surface tension than the refrigerant such as carbon dioxide preferentially flows in the corners of the second inner fin.

  Therefore, the first inner fin having a large apex angle, particularly the apex portion thereof, can be contact-heat exchanged with carbon dioxide, which is a refrigerant, without being covered with the refrigerating machine oil. Therefore, the heat transfer performance can be improved as compared with the heat transfer tubes for radiators with internal fins in which the vertex angles of all the internal fins are formed in the same size.

  In addition, the apex angle of the first inner fin is larger than the apex angle of the second inner fin in the range of 10 to 22 degrees, so that the heat transfer performance due to the shape difference between the two types of inner fins as described above. The effect of can be obtained.

  Specifically, if the difference between the apex angles of the inner fins is less than 10 degrees, the effect on the heat transfer performance due to the difference in shape between the two types of inner fins is not recognized, and if the difference is 22 degrees or more, the apex angle of the first inner fins is large. It becomes too much, and the space | interval with the corner part of an adjacent 2nd inner surface fin becomes narrow.

In this case, the refrigerating machine oil once separated from the refrigerant is not guided to the corners of the second inner fins, and the refrigerating machine oil is mixed into the refrigerant again, resulting in a decrease in heat transfer coefficient in the pipe and an increase in pressure loss. By setting the angle difference within the above range, the interval between the corners of the adjacent first inner fin and the second inner fin can be secured, and the refrigerating machine oil once separated from the refrigerant is guided to the corner of the second inner fin. To do.
Therefore, the refrigerating machine oil is prevented from being mixed with the refrigerant again, and the heat transfer performance is prevented from being lowered due to the refrigerating machine oil being mixed with the refrigerant again.

  Further, the apex angle of the first inner fin is set to a range of 18 to 30 degrees, and the apex angle of the second inner fin is set to a range of 8 to 15 degrees, thereby increasing the apex angle of the first inner fin. It can prevent becoming too much, and can ensure the space | interval with the corner part of an adjacent 2nd inner surface fin. Further, by setting the apex angle of the inner fin within the above range, it is possible to prevent the inner fin from becoming unnecessarily large and to reduce the necessary material amount, so that the material cost of the pipe can be reduced.

  Furthermore, it is difficult in terms of machining technology to process an inner fin with an apex angle of less than 8 degrees, and a reliable inner fin shape is formed by setting the apex angle of the second inner fin to 8 degrees or more. Can do.

  Further, since the corner portion between the bottom portion of the inner fin and the inner surface of the tube is formed in a curved surface shape, refrigerating machine oil having a surface tension larger than that of the refrigerant is more likely to flow through the corner portion of the second inner fin. For this reason, the refrigeration oil does not adhere to the first inner fin, and the first inner fin can directly exchange heat with the refrigerant, so that a decrease in heat transfer performance due to the influence of the refrigeration oil can be suppressed.

Further, the corner portion is configured in a circular arc shape having a predetermined radius of curvature, and the radius of curvature of the corner portion of the first inner fin is set to be 0. 0 from the radius of curvature of the corner portion of the second inner fin. By forming it large in the range of 01 to 0.1 mm, the refrigeration oil can be preferentially flowed to the corners of the second inner surface fins.
Therefore, the first inner fin can exchange heat with carbon dioxide, which is a refrigerant, more reliably, and the heat transfer performance can be further improved.

The heat transfer tube for a radiator with an inner fin includes a copper heat transfer tube for a radiator having a spiral inner fin described later on the inner surface.
The inner fin is formed in a spiral shape on the inner surface of the tube, protrudes toward the axial center of the tube, and includes a spiral belt-like convex portion having a substantially triangular cross section or a substantially trapezoidal cross section formed in a curved shape at the top. .

The height of the inner fin indicates the difference between the distance from the tube center to the bottom of the groove on the inner surface of the tube and the distance from the tube center to the tip of the inner fin top.
The refrigerant includes a refrigerant such as carbon dioxide, hydrocarbon, or chlorofluorocarbon.
The interval between the adjacent inner fins includes the interval between the center lines passing through the apex angles of the inner fins when the inner fins disposed on the circumferential inner surface are expanded, and between the second inner fins, This includes the distance between the first inner fin and the second inner fin.

  The apex angle is an angle obtained with a cross section perpendicular to the formation direction of the internal fins, and is an angle at the apex of the internal fins constituted by one side surface and the other side surface of the internal fin.

The curve shape includes a cross-sectional arc shape, a relaxation curve shape, or a clothoid curve shape.
Similar to the apex angle, the radius of curvature of the corner is a radius of curvature obtained by a cross section perpendicular to the formation direction of the inner fin.

  According to this invention, even if it is a case where refrigeration oil mixes in a refrigerant | coolant, the heat exchanger tube for heat sinks with an internal fin which suppresses the fall of heat transfer performance can be provided.

An embodiment of the present invention will be described below with reference to the drawings.
As shown in FIGS. 1 to 3, the heat transfer tube 1 for an internally finned radiator of the present invention allows a carbon dioxide refrigerant (hereinafter referred to as “CO ₂ refrigerant”) to pass through the tube interior 11, and has a plurality of tubes on the tube inner surface 10. It is the heat exchanger tube for heat radiator provided with the inner surface fin 20 (21, 22).

  1 shows a schematic cross-sectional view in a plane passing through the central axis of a general heat exchanger tube with internal fins, FIG. 2 shows a schematic cross-sectional view in a cross section perpendicular to the tube axis direction L, and FIG. The explanatory drawing which expands the heat exchanger tube for a heat sink with an internal fin and explains an internal fin is shown.

  A plurality of inner surface fins 20 provided on the tube inner surface 10 are constituted by a first inner surface fin 21 and a second inner surface fin 22 formed at a height H2 lower than the height H1 of the first inner surface fin 21.

  The heat transfer tube 1 for a radiator with an internal fin in the present embodiment will be described in detail. The height H1 of the first internal fin 21 is in a range of 0.04 to 0.2 times the tube inner diameter d of 3.4 mm. The height H2 of the second inner fin 22 is set within a range of 0.1 to 0.5 times the height H1 of the first inner fin 21. It is set to 0.10 mm, which is about 0.4 times.

  Further, an interval g between the adjacent inner surface fins 20 is set to 0.53 mm, which is 5.3 times as high as 0.9 times or more the height H2 of the second inner surface fins 22, and the first inner surface fins 21. Is set to 1.06 mm, which is 4.24 times that is three times or more the height H1 of the first inner surface fin 21.

  Further, the apex angle θ1 of the first inner fin 21 is set to 30 degrees within a range of 18 to 30 degrees, and the apex angle θ2 of the second inner fin 22 is set to 15 degrees within a range of 8 to 15 degrees. By setting the angle difference (θ1−θ2) between the apex angle θ1 of the first inner fin 21 and the apex angle θ2 of the second inner fin 22 to 15 degrees within the range of 10 to 22 degrees. ing.

  Further, as shown in FIGS. 2 and 3, the corner portions 31 and 32 of the bottom portion 20a (21a and 22a) of the inner fin 20 (21 and 22) and the tube inner surface 10 are both formed in a curved shape. . Specifically, the corner portions 31 and 32 are formed in a cross-sectional arc shape with a predetermined radius of curvature, the radius of curvature r1 of the corner portion 31 of the first inner surface fin 21 is 0.03 mm, and the second inner surface fin 22. The radius of curvature r2 of the corner portion 32 is set to 0.02 mm. Thereby, the difference between the curvature radius r1 and the curvature radius r2 is 0.01 mm which is within the range of 0.01 to 0.1 mm.

  More specifically, the heat transfer tube 1 for an internal fin-equipped radiator is a heat transfer tube formed of a phosphorous deoxidized copper tube and provided with a spiral internal fin 20 on the tube inner surface 10, and the tube outer diameter D is 4.76 mm. The wall thickness t is set to 0.68 mm, and the twist angle β of the inner fin 20 with respect to the tube axis direction L is set to 40 degrees.

  In addition, ten first inner fins 21 and second inner fins 22 are alternately arranged over the entire circumference of the pipe inner surface 10 alternately (number of inner surface fins: N1, N2). The ratio N1 / N2 of the number of inner fins of the inner fin 21 and the second inner fin 22 is 1.

  Note that, as described above, the heat transfer tube 1 for the radiator with fins on the inner surface is formed by grooving the phosphor deoxidized copper tube on the inner surface 10 of the tube by the floating plug 101 in the processing apparatus 100 shown in FIG. In addition to processing, the desired tube outer diameter D is drawn by a die 102 and manufactured. In addition, in the present Example, the heat transfer tube 1 for an internally finned radiator is formed of a phosphorous deoxidized copper tube, but may be formed of other copper alloys or metal materials.

Moreover, the heat transfer tube 1 for an internal fin radiator has a thickness t equal to or greater than the recommended lower limit thickness calculated by the following equation 1, and the ratio t / D between the outer diameter D and the thickness t is: Since the phosphorous deoxidized copper pipe of 0.04 to 0.25 is used, it can be used as a heat transfer pipe for a radiator in which the CO ₂ refrigerant is in a supercritical state and a high pressure during heat radiation.
In addition, the following number 1 is a mathematical formula for calculating a recommended lower limit wall thickness that can withstand the high operating pressure of the CO ₂ refrigerant, and is defined in the criteria related to the refrigeration safety regulation.

In the above formula 1, the recommended lower limit thickness is calculated assuming that the design pressure P is 10 MPa, the allowable stress σ _a of the heat radiating heat transfer tube is 33 MPa from JIS H 3300, and the efficiency η of the welded joint is 1.

If the outer diameter thickness ratio t / D is less than 0.04, the tube strength is low, so that it cannot withstand the pressure of the CO ₂ refrigerant and breaks, and the outer diameter thickness ratio t / D is 0.25. If it exceeds, the strength of the pipe increases, but the rolling process by the processing apparatus 100 becomes difficult. Therefore, Preferably, the range of the outer diameter thickness ratio t / D is equal to or more than the recommended lower limit thickness calculated in Formula 1, and the outer diameter thickness ratio t / D is more preferably 0.05 to 0.20. The range is 0.06 to 0.10.

With the above-described configuration of the heat transfer tube 1 for a radiator with an internal fin, the heat transfer performance as a heat transfer tube for heat dissipation was improved.
Specifically, the CO ₂ refrigerant becomes a two-phase flow during evaporation in the evaporation heat transfer tube, and it is important to increase the area of the tube inner surface 10 in order to improve the heat transfer performance. In short, the CO ₂ refrigerant becomes a single phase flow in a supercritical state at the time of heat dissipation in the heat transfer tube for heat dissipation, and thus the increase in the area of the tube inner surface 10 does not directly affect the improvement of the heat transfer performance.

  Accordingly, the first inner surface fin 21 and the second inner surface fin 22 having two different heights are provided, and the height H1 of the first inner surface fin 21 is set to a range of 0.04 to 0.2 times the pipe inner diameter, The distance g between the inner surface fins 20 is set to 0.9 times or more of the height H2 of the second inner surface fins 22, and the distance G between the first inner surface fins 21 is three times the height H1 of the first inner surface fins 21. The heat transfer performance was improved by setting as described above.

When the interval g between the inner surface fins 20 is reduced, the CO ₂ refrigerant is excessively agitated by the first inner surface fins 21 more than necessary for heat exchange, and once separated, the corner 32 portion of the second inner surface fins 22 is separated. Since the flowing refrigerating machine oil 50 is mixed with the CO ₂ refrigerant again, it becomes a factor of reducing the heat transfer performance.

Therefore, as described above, the spacing g of the inner surface fin 20 by setting the above interval, once with preventing separated refrigerating machine oil 50 is again mixed with the CO ₂ refrigerant, refrigerating machine oil 50 and CO ₂ refrigerant is separated After that, the height H1 of the first inner fin 21 that only sufficiently stirs the CO ₂ refrigerant was set.

  In this way, the heat transfer tube 1 for an internally finned radiator configured with a configuration for improving heat transfer performance is measured for pressure loss and in-tube heat transfer coefficient using the heat transfer performance evaluation apparatus 200 shown in FIG. Then, the measurement result was compared with a comparative heat transfer tube to be described later, and the pressure loss increase suppression effect and the in-tube heat transfer rate decrease suppression effect due to the provision of the first inner surface fins 21 and the second inner surface fins 22 were confirmed.

As shown in FIG. 5 (b), the test section 210 is composed of three subsections 211 having a heat transfer effective length of 500 mm, and the measurement is performed by using the heat exchanger tube 1 with an internal fin as a heat transfer tube for a high-temperature fluid. It was installed inside the heavy pipe, carbon dioxide was used as a refrigerant, the pressure on the inlet side was 10 MPa, the refrigerant flow rate was 520 kg / m ² s, and the measurement was performed by changing the mass concentration of the refrigerating machine oil.

  The comparative heat transfer tube, which is a conventional heat transfer tube for a radiator with an internal fin, has an outer diameter DΦ of 4.76 mm, a wall thickness of t 0.68 mm, a number of fins of N10, a fin height H of 0.30 mm, an apex angle θ of 30 degrees, an internal fin The radius of curvature r of the corner is 0.03 mm, the distance g 0.335 mm between the adjacent inner fins 20, and the twist angle β40 degrees of the inner fins 20 with respect to the tube axis direction L.

  As shown in FIG. 6A, which is a measurement result of pressure loss by the heat transfer performance evaluation measurement, the concentration of the refrigerating machine oil is 0.08 wt. %, The heat transfer tube 1 for the heat sink with internal fin and the comparative heat transfer tube had almost the same result. In addition, in FIG. 6, the result of the heat exchanger tube 1 for heat sinks with an internal fin is shown as Example No1, and the result of the comparative heat transfer tube is shown as Comparative Example No1.

  However, the concentration of the refrigerating machine oil is 2.7 wt. %, The rate of increase in pressure loss was smaller in the heat transfer tube 1 for the heat sink with internal fin than in the comparative heat transfer tube, and the effect of suppressing the increase in pressure loss was about 25% at maximum with respect to the comparative heat transfer tube. .

  Further, as shown in FIG. 6 (b), which is a measurement result of the heat transfer coefficient in the tube by the heat transfer performance evaluation measurement, the concentration of the refrigerating machine oil is 0.08 wt. %, The heat transfer tube 1 for the heat sink with internal fin and the comparative heat transfer tube had almost the same result.

  However, the concentration of the refrigerating machine oil is 2.7 wt. %, The heat transfer tube 1 for the heat sink with internal fins has a smaller rate of decrease in the heat transfer coefficient in the tube than the comparative heat transfer tube, and can obtain a pressure loss reduction suppression effect of about 20% at maximum with respect to the comparative heat transfer tube. did it.

Then, the performance comparison test implemented using the heat-transfer performance evaluation apparatus 300 shown in FIG. 7 about the heat exchanger tube 1 with an internal fin comprised with the said structure is demonstrated.
In this performance comparison test, Examples 1 to 5 shown in the following Table 1 were used with the number N of inner surface fins, the height H of the inner surface fin, the apex angle θ, and the radius of curvature r of the corner portion as parameters. 5 types of heat transfer tubes 1 for heat sinks with internal fins and 3 types of heat transfer tubes for heat sinks with internal fins up to Comparative Examples 1 to 3 were prepared as comparative objects. Comparative Example 1 is the above-described comparative heat transfer tube that is a conventional heat transfer tube for a radiator with an internal fin.

本性能比較試験は、概略図である図７に示す伝熱性能評価装置３００を用い、交換熱量を測定することにより性能比較を行った。この伝熱性能評価装置３００におけるテストセクションは伝熱有効長さ４ｍの２重管構造となっており、冷媒である二酸化炭素を入口条件：１０ＭＰａ、９０℃、出口条件：３０℃になるように毎時１５ｋｇの条件で流通させ、二重管の内側で放熱用伝熱管の外側の低温流体用伝熱管との間における二酸化炭素と水との交換熱量を測定した。なお、本性能比較試験における測定条件を以下の表２に示す。

In this performance comparison test, performance comparison was performed by measuring the heat of exchange using the heat transfer performance evaluation apparatus 300 shown in FIG. The test section in the heat transfer performance evaluation apparatus 300 has a double pipe structure with an effective heat transfer length of 4 m so that the refrigerant, carbon dioxide, has an inlet condition of 10 MPa, 90 ° C., and an outlet condition of 30 ° C. It was made to distribute | circulate on the conditions of 15 kg / hour, and the calorie | heat amount of the carbon dioxide and water between the heat exchanger tube for low temperature fluids outside the heat exchanger tube for heat radiation inside the double tube was measured. The measurement conditions in this performance comparison test are shown in Table 2 below.

上記表１の最下段に示された本性能比較試験による測定結果であり、伝熱性能評価の基準となる交換熱量は、上記表１の比較例Ｎｏ．１の交換熱量を１００とした際の各々比率で示している。

It is a measurement result by this performance comparison test shown at the bottom of Table 1 above, and the amount of exchange heat serving as a reference for heat transfer performance evaluation is the comparative example No. 1 in Table 1 above. Each ratio is shown as a ratio when the exchange heat quantity of 1 is 100.

  From this test result, the height H1 of the first inner fin 21 is 0.04 to 0.2 times the pipe inner diameter d, and the height H2 of the second inner fin 22 is 0.1 to 0.1 of the height H1. 0.5 times, the gap g between the inner fins 20 is 0.9 times or more of the height H2, the gap G between the first inner fins 21 is three times or more of the height H1, and the apex angle θ1 is 18-30. The apex angle θ2 of the second inner fin 22 is 8 to 15 degrees, the angle difference (θ1−θ2) between the apex angle θ1 and the apex angle θ2 is 10 to 22 degrees, and the difference between the curvature radius r1 and the curvature radius r2 Was set to 0.01 to 0.1 mm, it was confirmed that a higher amount of exchange heat was obtained than in Comparative Example 1 which is a conventional heat transfer tube for an internally finned radiator.

  Comparative Example NO. 2, the height H1 of the first inner fin 21 is 0.04 to 0.2 times the pipe inner diameter d, and the interval G between the first inner fins 21 is three times or more the height H1, The apex angle θ1 is 18 to 30 degrees, the apex angle θ2 of the second inner fin 22 is 8 to 15 degrees, the angular difference (θ1−θ2) between the apex angle θ1 and the apex angle θ2 is 10 to 22 degrees, and the radius of curvature r1 Even if the difference between the radius of curvature r2 and the radius of curvature r2 is set to 0.01 to 0.1 mm, the height H2 of the second inner fin 22 is 0.1 to 0. When exceeding 5 times and the distance g between the inner fins 20 is 0.9 times or less of the height H2, it is confirmed that the amount of exchange heat is lower than that of Comparative Example 1 which is a conventional heat transfer tube for an inner fin finned radiator. did.

  Comparative Example NO. 3, the height H2 of the second inner fin 22 is 0.1 to 0.5 times the height H1, and the distance g between the inner fins 20 is 0.9 times the height H2 or more. The interval G between the inner fins 21 is at least three times the height H1, the apex angle θ1 is 18 to 30 degrees, the apex angle θ2 of the second inner fin 22 is 8 to 15 degrees, and the apex angles θ1 and θ2 are Even if it is a heat exchanger tube for a radiator with an internal fin in which the angle difference (θ1-θ2) is set to 10 to 22 degrees and the difference between the curvature radius r1 and the curvature radius r2 is set to 0.01 to 0.1 mm, the first internal fin When the height H1 of 21 is 0.04 or less with respect to the inner diameter d of the tube, it was confirmed that the exchange heat amount is lower than that of the comparative example 1 which is a conventional heat transfer tube for an internally finned radiator.

As described above, the heat transfer tube 1 for a radiator with an internal fin includes the first internal fin 21 and the second internal fin 22 formed lower than the first internal fin 21, and the first internal fin 21. Is set to a range of 0.04 to 0.2 times the inner diameter d of the pipe, and the height H2 of the second inner fin 22 is set to 0.1 to 0 of the height H1 of the first inner fin 21. 3. By setting the range to 5 times, as shown in FIG. 3, for example, the refrigerating machine oil 50 having a surface tension larger than that of the CO ₂ refrigerant is guided to flow in the vicinity of the second inner surface fins 22, and the refrigeration from the CO ₂ refrigerant is performed. The machine oil 50 can be separated.

Furthermore, by forming the two types of inner fins 20 having different heights, it is possible to promote turbulent flow in the tube interior 11 and improve heat transfer performance.
In addition, by setting the height H1 of the first inner fin 21 to 0.04 or more of the pipe inner diameter d, it becomes a supercritical state at the time of heat dissipation, and the CO ₂ refrigerant in a single-phase flow state can be sufficiently stirred. The first inner fin 21 having a height can be formed.

  Further, for example, when the height H1 of the first inner fin 21 is set to be 0.2 times or more of the pipe inner diameter d, it is difficult to process the first inner fin 21, but the height H1 of the first inner fin 21 is high. Is set to 0.2 times or less of the tube inner diameter d, the reliable first inner surface fin 21 can be formed.

  Furthermore, by setting the height H2 of the second inner surface fins 22 to a range of 0.1 to 0.5 times the height H1 of the first inner surface fins 21, all the inner surface fins 20 become unnecessarily high. This can be prevented and the amount of material required can be reduced, so that the material cost of the pipe can be reduced.

  Further, when the height H1 of the first inner fin 21 is formed higher than the height H2 of the second inner fin 22, all the inner fins 20 are made the same height while improving the heat transfer performance. In comparison with this, an increase in pressure loss can be suppressed, and an increase in the load on the compressor can be prevented.

Further, the interval g between the adjacent inner surface fins 20 is set to 0.9 times or more the height H2 of the second inner surface fins 22, and the interval G between the first inner surface fins 21 is set to the height of the first inner surface fins 21. By setting it to 3 times or more of the height H1, it is possible to secure the interval between the inner fins 20, and to prevent the refrigerating machine oil 50 once separated from the CO ₂ refrigerant from being mixed with the CO ₂ refrigerant again. Therefore, it is possible to prevent the refrigerating machine oil 50 mixed in the CO ₂ refrigerant from adhering to the pipe inner surface 10 to reduce the heat transfer area, and further improve the heat transfer performance of the heat transfer pipe 1 for the radiator with fin on the inner surface. Can do.

Further, by forming the apex angle θ1 of the first inner fin 21 larger in the range of 10 to 22 degrees than the apex angle θ2 of the second inner fin 22, the refrigerating machine oil 50 mixed in the CO ₂ refrigerant has an apex angle θ. The corner portions 32 of the small second inner fins 22 can be made to flow easily.

Specifically, the angle of the corner portion 32 formed by the bottom portion 22a of the second inner surface fin 22 formed with a small apex angle θ2 and the tube inner surface 10 is the corner portion of the first inner surface fin 21 formed with a large apex angle θ1. It becomes smaller than the angle of 31. Thereby, for example, the refrigerating machine oil 50 having a larger surface tension than the CO ₂ refrigerant preferentially flows through the corner portions 32 of the second inner surface fins 22.

Therefore, the first inner fin 21 having a large apex angle θ1, particularly the apex thereof, can be contact-heat exchanged with the CO ₂ refrigerant without being covered with the refrigerating machine oil 50. Therefore, heat transfer performance can be improved as compared with the heat transfer tubes for heat sinks with internal fins in which the apex angles θ of all the internal fins are formed to the same size.

  In addition, since the angle difference (θ1−θ2) between the apex angle θ1 of the first inner fin 21 and the apex angle θ2 of the second inner fin 22 is set in the range of 10 to 22 degrees, two types as described above The effect of the heat transfer performance due to the shape difference of the inner fin 20 can be obtained.

  Specifically, if the difference in the apex angle (θ1-θ2) of the inner fin 20 is less than 10 degrees, the effect on the heat transfer performance due to the shape difference between the two types of inner fins 20 is not recognized. The apex angle θ1 of the inner fin 21 becomes too large, and the interval between the corner portions 32 of the adjacent second inner fins 22 becomes narrow.

In this case, the refrigerating machine oil 50 once separated from the CO ₂ refrigerant is not guided to the corner portions 32 of the second inner surface fins 22, and the refrigerating machine oil 50 is mixed into the CO ₂ refrigerant again, thereby reducing the heat transfer coefficient in the pipe and increasing the pressure loss. However, by setting the angle difference (θ1−θ2) of the apex angle within the above range, the interval between the corner portions 32 of the adjacent first inner surface fins 21 and second inner surface fins 22 can be secured, and CO ₂ refrigerant. It is possible to prevent the refrigerating machine oil 50 separated from the refrigerant from being introduced into the corner portion 32 of the second inner fin 22 and mixed with the CO ₂ refrigerant again.

  In addition, the apex angle θ1 of the first inner fin 21 is set in the range of 18 to 30 degrees, and the apex angle θ2 of the second inner fin 22 is set in the range of 8 to 15 degrees. It is possible to prevent the apex angle θ <b> 1 from becoming too large, and to secure an interval between the corner portions 32 of the adjacent second inner surface fins 22.

  In addition, by setting the apex angle θ of the inner fin 20 within the above range, the size of the inner fin 20 can be prevented from becoming unnecessarily large, and the necessary material amount can be reduced, so that the material cost of the pipe can be reduced. Can be planned.

  Furthermore, it is difficult in terms of machining technology to machine the inner fin 20 having an apex angle θ of less than 8 degrees. By setting the apex angle θ2 of the second inner fin 22 to 8 degrees or more, the inner fin 20 can be reliably connected. A shape can be formed.

In addition, since the corner portion between the bottom portion of the inner fin 20 and the tube inner surface 10 is formed in a curved shape, the refrigerating machine oil 50 having a surface tension larger than that of the CO ₂ refrigerant causes the corner portion 32 of the second inner fin 22 to be more It becomes easy to flow.

Therefore, the refrigerating machine oil 50 does not adhere to the first inner fin 21, and the first inner fin 21 can directly exchange heat with the CO ₂ refrigerant, so that the heat transfer performance can be further improved.

Further, the corner portion 30 has a circular arc shape with a predetermined radius of curvature r, and the radius of curvature r1 of the first inner surface fin 21 is in a range of 0.01 to 0.1 mm from the radius of curvature r2 of the second inner surface fin 22. Therefore, the refrigerating machine oil 50 can be preferentially caused to flow to the corner portions 32 of the second inner surface fins 22.
Therefore, the first inner fin 21 can exchange heat with carbon dioxide, which is a CO ₂ refrigerant, and the heat transfer performance can be further improved.

  In addition, since it becomes the highest pressure at the time of heat radiation, while using the heat transfer tube 1 for the heat sink with internal fin having an outer diameter of 5 mm or less and a sufficient thickness, the height H1 of the first internal fin 21 is 0.15 mm or more It is more preferable to set to.

In correspondence between the configuration of the present invention and the above-described embodiment,
The refrigerant of this invention corresponds to the CO ₂ refrigerant,
Similarly,
The height of the first inner fin corresponds to the height H1,
The height of the second inner fin corresponds to the height H2,
The interval between adjacent inner fins corresponds to the interval g,
The interval between the first inner fins corresponds to the interval G,
The apex angle of the first inner fin corresponds to θ1,
The apex angle of the second inner fin corresponds to θ2,
The bottom of the inner fin corresponds to the bottom 20a (21a, 22a),
The corners correspond to the corners 31, 32,
Although the radius of curvature corresponds to r1 and r2, the present invention is not limited to the configuration of the above-described embodiment, and many embodiments can be obtained.

Sectional drawing in the surface which passes along the central axis of the heat exchanger tube for radiators with an internal fin. Explanatory drawing about the heat exchanger tube for radiators with an internal fin. Explanatory drawing explaining an inner surface fin. Schematic of a processing apparatus. Schematic of the heat transfer performance evaluation apparatus used for heat transfer performance evaluation measurement. The graph of the measurement result by this performance comparison test. Schematic of the heat transfer performance evaluation apparatus used for this performance comparison test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heat exchanger tube 10 with a fin for inner surface ... Tube inner surface 11 ... Inside of tube 20 ... Inner surface fin 21 ... First inner surface fin 22 ... Second inner surface fin 20a, 21a, 22a ... Bottom 31, 32 ... Corner portion d ... Tube Inner diameter g ... Adjacent inner fins G ... First inner fins H1 ... First inner fin height H2 ... Second inner fin height θ1 ... First inner fin apex angle θ2 ... Second The apex angle r1 of the inner fin: the radius of curvature r2 of the corner of the first inner fin r2: the radius of curvature of the corner of the second inner fin

Claims (6)

A heat transfer tube for a radiator with an internal fin that has a plurality of internal fins on the inner surface of the tube and allows passage of the refrigerant inside the tube,
The inner fins,
A first inner fin and a second inner fin formed lower in height than the first inner fin,
While setting the height of the first inner fin in the range of 0.04 to 0.2 times the inner diameter of the tube,
A heat transfer tube for a radiator with an internal fin, wherein the height of the second internal fin is set in a range of 0.1 to 0.5 times the height of the first internal fin. The interval between the adjacent inner fins is set to 0.9 times or more the height of the second inner fin,
The heat transfer tube for a radiator with an internal fin according to claim 1, wherein an interval between the first internal fins is set to be three times or more a height of the first internal fin. The heat transfer tube for a radiator with an internal fin according to claim 1 or 2, wherein an apex angle of the first internal fin is formed larger in a range of 10 to 22 degrees than an apex angle of the second internal fin. Setting the apex angle of the first inner fin to a range of 18 to 30 degrees;
The heat transfer tube for an internal fin-equipped radiator according to claim 1, 2 or 3, wherein an apex angle of the second internal fin is set in a range of 8 to 15 degrees. The heat transfer tube for an internal fin-equipped radiator according to any one of claims 1 to 4, wherein a corner portion between a bottom portion of the internal fin and an inner surface of the tube has a curved shape. The corner is configured with a cross-sectional arc shape with a predetermined radius of curvature,
A radius of curvature of the corner of the first inner fin,
The heat transfer tube for a heat sink with an internal fin according to claim 5, wherein the heat transfer tube is provided with an internal fin with a fin in the range of 0.01 to 0.1 mm larger than the radius of curvature of the corner of the second internal fin.

Images