JP5883383B2 - Internal grooved tube with excellent extrudability - Google Patents

Description

  The present invention relates to an internally grooved tube made of aluminum alloy.

  In recent years, demands for energy saving and downsizing of heat exchangers used in heat pump air conditioners and the like are increasing, and downsizing and high efficiency of the heat exchangers are required.

  As heat exchangers used in heat pump air conditioners, fin-and-tube heat exchangers are mainly used. This fin-and-tube type heat exchanger is constructed by inserting a heat transfer tube into an aluminum fin having a hole larger in diameter than the heat transfer tube in advance, passing a tube expansion plug through the heat transfer tube, and expanding the tube. It is molded by bringing it into close contact. The fin-and-tube heat exchanger exchanges heat with air outside the fins made of aluminum by flowing a refrigerant such as HFC through the tube of the heat transfer tube.

  Conventionally, as a heat transfer tube used in a fin-and-tube heat exchanger, a copper alloy having high thermal conductivity has been used, but there is also a rise in copper price and a demand for weight reduction of the heat exchanger itself, Instead of copper, aluminum pipes are being used.

  Copper alloys and aluminum alloys that are used as heat exchanger piping use internally grooved tubes with fins on the inner surface in order to increase heat exchange efficiency. Various internal groove shapes have already been proposed, but the spiral tube with a certain angle with respect to the axial direction has excellent heat exchange efficiency, and various groove shapes have been developed and put to practical use. (For example, Patent Document 1).

  As a method for producing a spiral grooved tube from an aluminum alloy, it is common to form a tube by a rolling process as shown in Patent Document 2 after forming the tube by an extrusion process or a drawing process.

  On the other hand, in the case of a straight grooved tube in which the inner groove is parallel to the axial direction, the heat exchange efficiency may be inferior to that of the spiral grooved tube, but the inner groove may be provided only by extrusion or drawing. In terms of cost, it is superior to the spiral tube, so it is expected to be expanded in the future.

  However, most of the fin shapes that have been studied are related to spiral grooved tubes. As the groove shape of the straight grooved tube, an internally grooved tube (Patent Document 3) having fins with different heights has been proposed so that the fins are not crushed when the fins are assembled.

JP-A-4-260793 JP 2001-241877 A JP 2001-289585 A

  However, the prior art described in the above literature has room for improvement in the following points.

  First, the spiral grooved pipes described in Patent Document 1 and Patent Document 2 have a problem in that the manufacturing cost is high because the extruded pipe is further processed in a separate process. In the case of an aluminum alloy, the cold workability is inferior to that of a copper alloy, so the rolling process speed has to be reduced, and there is room for improvement in terms of productivity.

  Secondly, as for the groove shape of the straight grooved tube, sufficient studies have not been made except for the straight grooved tube of Patent Document 3. Furthermore, some straight grooved tubes cannot be extruded depending on the fin shape, and the viewpoint of extrudability becomes important. However, there have been no studies on the fin shape and extrudability so far.

  Under such circumstances, the present inventor first noticed the need for the development of an internally straight grooved tube using an aluminum alloy having a fin shape with excellent extrudability and excellent heat exchange efficiency. It was.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an optimal fin shape that is superior in extrudability and heat exchange efficiency as compared with an inner surface straight grooved tube using a conventional aluminum alloy. To do.

  As a result of various studies on the shape of the inner straight grooved tube made of aluminum alloy, the present inventors have found the length of the inner peripheral edge and the area of the groove space in the cross section orthogonal to the longitudinal direction of the inner grooved tube. It was found that when the ratio was within a certain range, the shape was excellent in extrudability and heat exchange efficiency.

That is, the inner surface grooved tube according to the present invention is an inner surface grooved tube made of an aluminum alloy having a plurality of protrusion-shaped fins existing on the inner surface of the tube in parallel with the longitudinal direction of the tube. The shape and arrangement of the plurality of fins in the cross section orthogonal to the longitudinal direction of the inner surface are substantially uniform in the circumferential direction of the inner grooved tube, and the inner peripheral edge length F (mm) in the cross section and the inner peripheral edge in the cross section And an inner grooved tube having a ratio of the area A (mm ² ) of the groove space surrounded by a circle in contact with the tops of the plurality of fins within a range of 12 ≦ F / A ≦ 14.

  According to this configuration, by setting the length of the inner peripheral edge and the area of the groove space in the cross section orthogonal to the longitudinal direction of the inner surface grooved tube within a certain ratio, excellent extrudability and heat exchange are achieved. An internally grooved tube with excellent efficiency can be obtained.

  Moreover, the heat exchanger which concerns on this invention is equipped with an aluminum alloy external fin, and an internal grooved pipe formed by expanding said internal grooved pipe closely_contact | adhered to this aluminum alloy external fin, Fin It is an and tube type heat exchanger.

  According to this configuration, since the inner grooved tube formed by expanding the inner grooved tube having excellent extrudability and excellent heat exchange efficiency is used, the fin having excellent heat exchange rate by a simple tube expansion process. And tube type heat exchangers can be produced accurately and efficiently.

  Moreover, the air conditioner which concerns on this invention is an air conditioner provided with said heat exchanger.

  According to this configuration, since a fin-and-tube heat exchanger with an excellent heat exchange rate that can be produced accurately and efficiently is used, an air conditioner with an excellent heat exchange rate can be produced with high accuracy and efficiency. Can do.

  ADVANTAGE OF THE INVENTION According to this invention, the heat exchanger tube which is excellent in extrudability and has the fin shape which fully satisfies the heat transfer characteristic as a heat exchanger tube can be provided.

It is a cross section of the internally grooved tube according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate. In addition, in embodiment of this invention, A-B shall mean A or more and B or less.

<Inner grooved tube structure>
FIG. 1 is a cross section of an internally grooved tube according to an embodiment. The inner surface grooved tube 100 is an inner surface grooved tube 100 made of an aluminum alloy having a plurality of protrusion-shaped fins 102 existing on the inner surface of the tube in parallel with the longitudinal direction of the tube. The shape and arrangement of the plurality of fins 102 in the cross section perpendicular to the longitudinal direction of the inner surface grooved tube 100 are substantially uniform in the circumferential direction of the inner surface grooved tube 100. Further, the ratio of the length F (mm) of the inner peripheral edge in the cross section to the area A (mm ² ) of the groove space portion surrounded by a circle in contact with the inner peripheral edge and the tops of the plurality of fins 102 in the cross section is 12 ≦ It is within the range of F / A ≦ 14.

Here, the reason for this numerical limitation will be described. The inner peripheral length (inner peripheral length) F (mm) and the groove space area A (mm ² ) are both fins when given a predetermined inner diameter (diameter of a circle in contact with the groove bottom) D1. It is a numerical value determined by the number of 102, the height of the fin 102, and the width of the fin 102. When the number of fins 102 is small, F is small, A is large, and F / A is small. Conversely, as the number of fins increases, the F / A increases.

  That is, when the height of the fin 102 is large, not only an increase in pressure loss is caused, but also defects such as a missing or missing fin 102 are likely to occur during extrusion. Furthermore, since the fin 102 is likely to be broken during the tube expansion process when the heat exchanger is assembled, the height of the fin 102 is preferably limited to a predetermined height or less.

  Therefore, by providing F and A so that 10 ≦ F / A ≦ 15, it is possible to provide an internally grooved tube having excellent extrudability and high heat exchange efficiency. When F / A is less than 10, the groove space area is large with respect to the inner peripheral length, that is, the number of fins is small, and sufficient heat exchange efficiency cannot be obtained. Therefore, F / A is preferably 10 or more from the viewpoint of extrudability or heat exchange rate, more preferably 11 or more for the same reason, and most preferably 12 or more for the same reason. Further, if F / A exceeds 15, the number of fins is large, that is, the weight of the tube increases, which is not preferable. Furthermore, when the groove space portion area is small, the liquid generated at the time of condensation is not sufficiently discharged, and the heat exchange efficiency is lowered. Therefore, F / A is preferably 15 or less from the viewpoint of suppressing the tube weight or heat exchange rate, more preferably 14.5 or less for the same reason, and 14 or less for the same reason. Most preferred.

  Further, from another viewpoint, particularly when the upper limit value of the height of the fin 102 exceeds 10% of the inner diameter D1 shown in FIG. 1, the fin 102 is lost during extrusion and the fin 102 is broken during the tube expansion process. Probability increases. Therefore, the height of the fin 102 is preferably 10% or less of the inner diameter D1 from the viewpoint of suppression of pressure loss or suppression of missing / breaking of the fin, and more preferably 7% or less for the same reason. 6% or less is most preferable for the same reason. The height of the fin 102 is preferably 1 mm or less in terms of absolute value, from the viewpoint of suppressing pressure loss or suppressing missing / breaking of the fin, and is 0.7 mm or less for the same reason. More preferably, the thickness is 0.5 mm or less for the same reason.

When the inner grooved tube 100 is enlarged and reduced in a similar shape, if the inner diameter (diameter of a circle in contact with the groove bottom) D1 itself of the inner grooved tube 100 is doubled, the length of the inner peripheral edge ( The inner circumferential length F (mm) is also doubled, but the area A (mm ² ) of the groove space is quadrupled. Therefore, the formula of 12 ≦ F / A ≦ 14 is established within the range of a normal inner diameter (diameter of a circle in contact with the groove bottom) D1. The value of the range of the normal inner diameter (diameter of the circle in contact with the groove bottom) D1 is naturally determined by technical common sense. For example, the inner diameter of the inner grooved tube is 3 mm or more. It is preferable from the viewpoint of extrudability, and more preferably 4 mm or more. Moreover, if the internal diameter of an inner surface grooved pipe is 10 mm or less, it is preferable from a viewpoint of weight reduction and size reduction of a heat exchanger, and if it is 8 mm or less, it is more preferable.

  In the present embodiment, numerical values relating to the shape and arrangement of the fins 102 such as the number of fins 102 and the width of the fins 102 are not particularly defined as long as the above relational expression is satisfied. If the thickness is 0.2 mm or less, the probability that the fins are lost during extrusion is remarkably increased. Therefore, in order to suppress the probability that the fins are lost during extrusion, the thickness is desirably 0.2 mm or more. The width of the fin 102 is desirably 0.3 mm or more, and most desirably 0.4 mm or more for the same reason.

  The plurality of fins 102 on the inner surface of the pipe may be produced by any manufacturing process, but are formed by extruding an aluminum alloy material described later. Is preferable in terms of formability and cost.

  In particular, the plurality of fins 102 on the tube inner surface of the straight grooved tube can be provided with an inner surface groove only by extrusion since the inner surface groove is parallel to the axial direction. Therefore, it is preferable that the plurality of fins 102 on the inner surface of the pipe are formed by extrusion because the cost is superior to that of the helical pipe. Moreover, as extrusion conditions, it is preferable that it is what was extruded especially at 350-550 degreeC hot. In other words, an aluminum alloy lump called billet is extruded from a die hole having a shape corresponding to the plurality of fins 102 by applying a strong pressure using an extruder between 350 to 550 ° C. It is preferable to make a plurality of fins 102 having a substantially uniform cross-sectional shape in the circumferential direction of the tube with high accuracy and efficiency.

<Inner grooved tube material>
The main members of the internally grooved tube 100 according to the present embodiment are not particularly limited and may be made of an aluminum alloy. Here, “aluminum alloy” means an alloy containing aluminum as a main component, but excludes so-called “pure aluminum” having a purity of 99.0% by mass (hereinafter referred to as “%”). is not. That is, the “aluminum alloy” includes pure aluminum (1000 series), Al—Cu series alloy (2000 series), Al—Mn series alloy (3000 series), Al—Si series alloy (4000 series), Al—Mg series. Alloys (5000 series), Al—Mg—Si based alloys (6000 series), and Al—Zn—Mg based alloys (7000 series) are included. However, among these aluminum alloys, when used as a heat transfer tube of a heat pump, it is preferable to use an Al—Mn alloy (3000 series) with high strength without reducing the workability and corrosion resistance of pure aluminum. .

  The composition of the aluminum alloy is not particularly limited, but includes, for example, Mn: 1.0 to 1.5%, Cu: 0.05 to 0.20%, and Mg: 0.03% or less, The balance is preferably made of Al and inevitable impurities.

  Next, the reason for limiting the components in this way will be described. Mn is a main additive element for improving the strength of 3000 series alloys, and has the effect of giving solid solution, partly precipitated in aluminum and imparting strength. However, if the added amount is less than 1.0%, it is transmitted. The strength as a heat tube may be insufficient, and if it exceeds 1.5%, the extrusion pressure at the time of extrusion tends to increase, and as a result, defects such as missing or broken fins are likely to occur. Therefore, the amount of Mn added is preferably in the range of 1.0 to 1.5% in order to suppress problems such as strength as a heat transfer tube or missing or missing fins, and further 1.0 to 1.3 % Is preferable for the same reason.

  Cu has the effect of solid solution in aluminum and imparts strength, but if the amount of Cu is less than 0.05%, the effect may not be obtained, while if added over 0.25% Is liable to hinder formability and deteriorate corrosion resistance. Therefore, the Cu addition amount is preferably in the range of 0.05 to 0.25% from the viewpoint of strength, formability, or corrosion resistance.

  Mg dissolves in aluminum and has the effect of further improving the strength of the Al-Mn alloy. On the other hand, if it is contained in a small amount, it tends to cause a significant increase in pressure during extrusion, resulting in formability and productivity. May cause a drop. Therefore, the Mg content is preferably 0.025% or less in order to suppress an increase in extrusion pressure.

  Inevitable impurities include Fe, Si, Zn, and the like. If these are Fe of 0.7% or less, Si of 0.6% or less, and Zn of 0.1% or less, the above-described embodiment will be described. This is preferable because it does not inhibit various effects of the internally grooved tube 100.

  Ti, Cr and Zr may be contained because they have the effect of uniformly refining the ingot structure, but if the total amount exceeds 0.2%, a giant intermetallic compound is formed or the extrudability is lowered. Therefore, the total content is preferably 0.2% or less. The other inevitable impurities are each preferably 0.05% or less, and the total amount is preferably 0.15% or less.

  Further, the inner grooved tube 100 of the present embodiment may be provided with a Zn diffused layer by performing Zn diffusion heat treatment after Zn is adhered to the outer surface by a method such as thermal spraying after extrusion. Since the Zn diffusion layer has a lower pitting corrosion potential than the portion of the pipe material where Zn is not diffused, the sacrificial anticorrosive action prevents the pipe material and improves the corrosion resistance of the pipe material.

<Expanded inner grooved tube>
The internally grooved tube according to the present embodiment is an internally grooved tube formed by expanding the above internally grooved tube 100 before expanding. Although this pipe expansion process is not particularly limited, for example, the process of passing the pipe expansion plug through the inner grooved pipe 100 before the pipe expansion and expanding the inner grooved pipe 100 before the pipe expansion is simple and accurate. Used.

  This tube expansion step is usually performed when a fin-and-tube heat exchanger described later is manufactured. That is, the inner surface grooved tube 100 before expansion is inserted into an aluminum alloy fin having a larger diameter than the inner surface grooved tube 100 before expansion, and the expansion plug is inserted into the inner surface grooved tube 100 before expansion. It is usually performed to manufacture a fin-and-tube heat exchanger by closely contacting an aluminum fin by expanding the tube.

<Fin and tube heat exchanger and air conditioner>
A fin-and-tube heat exchanger according to the present embodiment includes a fin-and-tube type heat exchanger provided with an aluminum alloy external fin and the inner grooved tube 100 formed in close contact with the aluminum alloy external fin. It is a heat exchanger. This fin-and-tube heat exchanger uses an internally grooved tube 100 formed by expanding an internally grooved tube having excellent extrudability and excellent heat exchange efficiency. The heat exchange rate when heat is exchanged with the air outside the aluminum fins by flowing a refrigerant such as HFC in the air, and the fin-and-tube heat exchanger is accurately and efficiently achieved through a simple tube expansion process. Can be produced.

  An air conditioner according to the present embodiment is an air conditioner including the fin-and-tube heat exchanger described above. Since this air conditioner uses a fin-and-tube heat exchanger with an excellent heat exchange rate that can be produced accurately and efficiently, it is possible to achieve downsizing and high efficiency. This air conditioner can be used publicly as a heat pump air conditioner that is particularly demanding for energy saving and downsizing.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  For example, in the above embodiment, the inner surface grooved tube 100 made of aluminum alloy having a plurality of protrusion-shaped fins 102 existing on the inner surface of the tube in parallel with the longitudinal direction of the tube is referred to as “parallel”. Need not be strictly “parallel” and may have a slope of ± 5 °, preferably ± 3 °, most preferably ± 1 ° with respect to the longitudinal direction of the tube. This is because, in the manufacturing process of the inner grooved tube 100, it is difficult to manufacture the plurality of fins 102 of all the protrusions so as to be completely “parallel”.

  In the above embodiment, the shape and arrangement of the plurality of fins 102 in the cross section perpendicular to the longitudinal direction of the inner surface grooved tube 100 are substantially uniform in the circumferential direction of the inner surface grooved tube 100. The term “perpendicular” here does not require strictly crossing at right angles, and is within ± 5 °, preferably within ± 3 °, and most preferably within ± 1 ° with respect to the longitudinal direction of the tube. May be crossed. This is because, when the inner grooved tube 100 is cut and the cross section is observed, it is difficult to cut the inner grooved tube 100 so that it is completely “right” in the longitudinal direction of the inner grooved tube 100.

  Further, the term “substantially uniform” as used herein does not require complete uniformity, and the height and width of the plurality of fins 102 are within ± 5 ° of the average value, preferably within ± 3 °, and most preferably If the angle is within ± 1 °, the shape is assumed to be “substantially uniform”. This is because it is difficult to manufacture all the fins 102 so as to be completely “uniform”. Further, if the intervals between the vertices of the plurality of fins 102 are within ± 5 ° of the average value, preferably within ± 3 °, and most preferably within ± 1 °, the arrangement is “substantially uniform”. . This is because it is difficult to manufacture all the fins 102 so as to be completely “uniform”.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these.

<Experimental example 1>
Next, examples of the present invention will be described together with comparative examples. Internal grooved tubes having various fin shapes shown in Table 1 were produced by hot extrusion. As extrusion conditions, extrusion was performed using a JIS3003 and JIS6063 alloy at a billet temperature of 500 ° C. and an extrusion speed of 20 m / min. After the extrusion, the following evaluation was performed.

Extrudability The tube after extrusion was observed with the naked eye, and when there was a defect such as a missing or missing fin, it was evaluated as “Yes”, and when there was no problem, it was evaluated as “No”.

Heat transfer characteristics Prepared heat transfer tubes of various shapes in the inner tube of a double-pipe heat exchanger, HFC as a refrigerant flows through the heat transfer tube at a refrigerant flow rate of 300 kg / m ² sec, and water to be cooled flows outside the tube Then, the heat transfer coefficient in the tube was measured.

  The evaluation results shown in Table 1 will be described. Examples 1 to 9 satisfy the condition of 10 ≦ F / A ≦ 15, no fin defects during extrusion, and good heat transfer coefficient. On the other hand, in Comparative Examples 10, 11, and 15, F / A does not satisfy the condition of 10 ≦ F / A ≦ 15, and the heat transfer coefficient is low. Since Comparative Examples 12 to 14 had a large number of fins, F / A did not satisfy 10 ≦ F / A ≦ 15, and fin defects were observed during extrusion.

<Experimental example 2>
The extruded tube having the shape of the condition 1 shown in Table 1 was manufactured using the alloy having the components shown in Table 2, and evaluated according to the following evaluation items. The extrusion conditions were a billet temperature of 500 ° C. and an extrusion speed of 20 m / min.

Extrusion pressure The case where a significant pressure increase was observed during extrusion was evaluated as “×”, and the case where there was no problem was evaluated as “◯”. Specifically, when the pressure during extrusion exceeded 20 MPa, it was evaluated as “×”, when it was 20 MPa or less and 18 MPa or more, “Δ”, and when it was 18 MPa or less, it was evaluated as “◯”. The evaluation results are shown in Table 3.

Tensile test The tube after extrusion was subjected to a tensile test based on JISZ2241. The evaluation results are shown in Table 3.

  Table 3 will be described. Examples 16-21 contain a suitable material (Mn: 1.0-1.5 mass%, Cu: 0.05-0.25 mass%, and Mg: 0.025 mass% or less, with the balance being Al. Since an aluminum alloy composed of inevitable impurities is used, no significant increase in pressure is observed during extrusion. On the other hand, each of Comparative Examples 22 and 24 has too little content of Mn or Cu, and therefore does not satisfy the conditions of the preferred material. Therefore, the mechanical properties are lower than when the preferred material is used, so There is room for improvement. In Comparative Examples 23, 25, and 26, since the content of Mn, Cu, and Mg is too high, the conditions for suitable materials are not satisfied. Therefore, a certain amount of pressure is increased during extrusion, and the extrudability is a suitable material. Was not enough.

  In the above, this invention was demonstrated based on the Example. It is to be understood by those skilled in the art that this embodiment is merely an example, and that various modifications are possible and that such modifications are within the scope of the present invention.

  As described above, according to the present invention, it is possible to provide a heat transfer tube having a fin shape that is excellent in extrudability and sufficiently satisfies the heat transfer characteristics as a heat transfer tube, such as heat from a refrigerator or an air conditioner. As an internally finned heat transfer tube used for an exchanger, it has a remarkable industrial effect.

D0: pipe outer diameter D1: diameter of a circle in contact with the groove bottom 100: inner grooved tube 102: fin

Claims (8)

An inner surface grooved tube made of aluminum alloy having a plurality of protrusion-shaped fins present on the inner surface of the tube in parallel with the longitudinal direction of the tube,
The shape and arrangement of the plurality of fins in the cross section perpendicular to the longitudinal direction of the inner surface grooved tube are substantially uniform in the circumferential direction of the inner surface grooved tube,
The ratio of the length F (mm) of the inner peripheral edge in the cross section to the area A (mm ² ) of the groove space portion surrounded by a circle in contact with the inner peripheral edge and the tops of the plurality of fins in the cross section is 12 ≦ F / A Within the range of ≦ 15,
The inner diameter of the inner grooved tube is 3 mm to 10 mm,
The main member of the inner surface grooved tube contains Mn: 1.0 to 1.5% by mass, Cu: 0.05 to 0.25% by mass, and Mg: 0.025% by mass or less, with the balance being Al. And an aluminum alloy consisting of inevitable impurities,
An internally grooved tube, wherein the total content of Ti, Cr and Zr in the inevitable impurities is 0.2% or less.   The internally grooved tube of claim 1, wherein the ratio is in the range of 12 ≦ F / A ≦ 14. Wherein comprising the step you molded by extrusion or drawing process a plurality of fins material in the tube surface, method of manufacturing inner grooved tube according to claim 1.   The internally grooved tube according to claim 1, wherein a height of the fin is 10% or less of the inner diameter.   The internally grooved tube according to claim 1, wherein the fin has a width of 0.2 mm or more. A method for manufacturing an internally grooved tube , comprising the step of expanding the internally grooved tube according to claim 1. Comprising the step of adhering an aluminum alloy external fins to claim 6 inner grooved tube obtained by the method described, the manufacturing method of the heat exchanger of the fin and tube type. Using a heat exchanger obtained by the production method according to claim 7, air conditioner manufacturing method comprising the step of producing the air conditioner.