JPH1123185A - Double tube type heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further enhance radiating performance of an overall double tube type oil cooler by devising cooling water side heat transfer efficiency by effectively utilizing a fastest part of a flowing velocity in a flow of the water flowing out from a tube to heat exchange with oil without reducing a radiating area. SOLUTION: A double tube type oil cooler 1 is installed in an extension line of an outer diameter size (WT) of a tube 2 in a lower tank 3 of a radiator, i.e., in a fastest part of a flowing velocity in a flow of cooling wafer flowing out from the tube 2. And, a sectional shape of the cooler 1 is formed in a short flat elliptical shape having a shorter size of the short axis along a width direction of the tube 2 than the axis along a lengthwise direction of the tube 2. Thus, even in the case of the cooler 1 having small size in the width direction, a surface area of an outer wall surface of an outer cylindrical tube 11 in contact with the water is increased to suppress a decrease in radiating area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-pipe heat exchanger having an annular passage in which a second fluid that exchanges heat with a first fluid flows. The present invention relates to a double-pipe heat exchanger that is optimal for an oil cooler with a built-in radiator that cools oil by being cooled.

[0002]

2. Description of the Related Art Conventionally, as a double-pipe heat exchanger, as shown in FIGS. 10 and 11, a radiator downstream tank 10 for cooling cooling water of an automobile engine is used.
2 has a built-in radiator double-tube oil cooler 100. The double-pipe oil cooler 100 is a water-cooled oil cooler that exchanges heat between cooling water flowing in from a tube 103 of a radiator and oil flowing inside the double-pipe oil cooler 100 to cool the oil. .

The double-pipe oil cooler 100 has a cylindrical outer pipe 104 in contact with the cooling water on the outer wall surface, and is disposed inside the outer pipe 104 so as to be concentric with the outer pipe 104. A cylindrical inner tube 105, and an annular oil passage 10 formed between the outer tube 104 and the inner tube 105.
6, an inner fin 107 provided in the oil passage 106, and a connection joint 109 for connecting the outer tube 104 and the connecting tube 108 to recirculate oil into the oil passage 106.

[0004]

However, in the conventional double-tube oil cooler 100, generally, as shown in FIGS. 10 and 11, in order to secure a sufficient heat radiation area (heat transfer area). And the width of the tube 103 (WT)
The diameter of the double-tube oil cooler 100 is larger than that of the oil cooler 100. In this case, the flow of the cooling water becomes stagnant in the vicinity of the downstream portion (the lower end portion in the figure) of the double-tube oil cooler 100, and the flow velocity of the cooling water flowing around the downstream portion is slowed down. There has been a problem that the side heat transfer efficiency is reduced. Further, in the related art, the water flow of the cooling water flowing from the tube 103 into the downstream tank 102 is not effectively used for improving the oil cooling performance. There has been a problem that the heat radiation performance cannot be further improved.

Japanese Utility Model Laid-Open Publication No. Sho 58-46969 proposes a radiator tank in which a double-pipe oil cooler having an outer cylinder pipe and an inner cylinder pipe each having an 8-shaped cross section is incorporated. However, since the relationship between the radiator tube and the double-tube oil cooler is not disclosed at all, the cooling water flowing from the tube into the tank is effectively used, that is, the cooling water side specification is used. It is hard to say that it has improved.

Further, Japanese Utility Model Laid-Open No. 58-52462 proposes a radiator tank in which a double-pipe oil cooler having an outer tube and an inner tube having a flat or rectangular cross section is incorporated. Have been. However, the long axis of this double-pipe oil cooler is provided so as to oppose the direction of the flow of cooling water flowing from the tube, and the short axis extends along the direction of the flow of cooling water flowing from the tube. Is provided. For this reason, the flow of the cooling water becomes stagnant near the bottom portion of the double-tube oil cooler, and the flow speed of the cooling water flowing around the bottom portion is reduced, and the cooling water side heat transfer efficiency is reduced. Problem arises. As a result, the cooling water flowing from the tube into the tank cannot be effectively used, and if the heat radiation area is to be made the same as that of the cylindrical double-pipe oil cooler, it is necessary to increase the width of the tank. Therefore, there is a problem that the width of the radiator is increased.

Japanese Utility Model Laid-Open Publication No. Sho 59-71071 proposes a radiator tank in which a double-pipe oil cooler having an outer cylinder pipe and an inner cylinder pipe having an elliptical cross section is incorporated. . Furthermore, Japanese Patent Application Laid-Open No. 3-233129 proposes a radiator tank in which a double-pipe oil cooler having an outer pipe and an inner pipe having a substantially U-shaped cross section is incorporated. However, since the diameter of the double-pipe oil cooler is larger than the width of the tube of the radiator, these parts effectively utilize the portion of the cooling water flowing from the tube into the tank at the highest flow velocity. Absent.

[0008] The study of improving the heat radiation performance of the entire double-pipe oil cooler has been focused on the improvement of the oil-side specification, which has a high contribution to the performance improvement. In order to improve the oil side specification, inner fins are mainly inserted in the oil passages, and specially shaped inner fins are used to increase the heat transfer area of the inner fins. Now, the optimization has progressed, and we have reached a place where there is no room for further improvement.

Here, conventionally, as a radiator,
Generally, a down-flow radiator in which a plurality of tubes extending in the vertical direction is arranged between the upper tank and the lower tank, and the cooling water flows vertically (up and down) from the upper tank to the lower tank. Was. However, in recent years, a radiator has been changed to a cross-flow radiator in which a radiator is arranged in a vehicle in a horizontal direction and flows from an upstream tank to a downstream tank in a horizontal direction in order to improve mountability to the vehicle. The number of tubes of the cross-flow type radiator is smaller than that of the down-flow type radiator, and the flow rate of the cooling water flowing into the downstream side tank from one tube becomes faster than that of the down-flow type radiator. I have.

[0010] Regardless of the down-flow system or the cross-flow system, under high engine load conditions in which the heat radiation performance of the double-tube oil cooler is particularly required, the cooling water flowing back to the radiator also has a high flow rate, and The flow velocity of the cooling water flowing into the downstream tank is further increased. Therefore, in the flow of cooling water that returns to the radiator,
By effectively utilizing the cooling water flow having the highest flow velocity, that is, the cooling water flowing from the tube, the cooling water side specification is improved to further improve the heat radiation performance of the entire double-tube oil cooler 100. It is desired.

In order to effectively utilize the flow of the cooling water flowing from the tube 103, as shown in FIG. 12, the diameter of the double-tube oil cooler 100 is set to be smaller than the width (WT) of the tube 103. It is conceivable to make it smaller. However, in this case, the double-tube oil cooler 1
The heat radiation area of the oil cooler 100 is greatly reduced, and the heat exchange performance of the double-tube oil cooler 100 is deteriorated.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the portion of the first fluid flowing from the upstream flow pipe into the downstream flow pipe having the highest flow rate without reducing the heat transfer area. It is an object of the present invention to provide a double-pipe heat exchanger that can be used effectively for heat exchange with two fluids to improve the first fluid side specification and further improve the overall heat exchange performance. . Another object of the present invention is to provide a double-pipe heat exchanger in which the first fluid-side heat transfer efficiency does not decrease by preventing stagnation of the first fluid in the downstream portion. It is still another object of the present invention to provide a double-pipe heat exchanger capable of suppressing an increase in the width of an upstream flow path pipe such as a tube or a downstream flow path pipe such as a downstream tank.

[0013]

According to the first aspect of the present invention, the double-pipe heat exchanger is installed in the downstream flow pipe within an extension of the width dimension of the upstream flow pipe. By doing so, the first flow from the upstream flow pipe into the downstream flow pipe
The fastest part of the fluid flow can be brought into contact with the outer wall surface of the entire double-pipe heat exchanger. As described above, since the first fluid side specification can be improved, the heat exchange performance of the entire double-pipe heat exchanger can be further enhanced.

The cross-sectional shape of the double-pipe heat exchanger has a flat shape in which the width is shorter in the horizontal direction than in the vertical direction perpendicular to the width direction of the upstream flow pipe, and the upstream flow path is By making the lateral dimension of the double-pipe heat exchanger smaller than the lateral dimension of the pipe, the surface area of the outer wall surface of the double-pipe heat exchanger in contact with the first fluid can be increased. Even if the double-pipe heat exchanger is installed within the extension of the width dimension of the upstream flow pipe in the downstream flow pipe, it is possible to suppress the decrease in the heat exchange performance of the double-pipe heat exchanger. it can.

According to any one of the second to fourth aspects of the present invention, the cross-sectional shape of the double-tube heat exchanger may be a polygonal shape having a major axis and a minor axis, or an elliptical shape. Alternatively, by making the shape oval, the first fluid flows smoothly near the outer wall surface of the double-pipe heat exchanger without stagnation, so that the heat transfer efficiency of the first fluid is improved. According to the invention described in claim 3 or 4, the cross-sectional shape of the double-pipe heat exchanger is made elliptical or elliptical having a major axis and a minor axis, so that the upstream side is formed. Since the first fluid flows smoothly without stagnation near the outer wall surface of the double-pipe heat exchanger on the side opposite to the flow path pipe side, the flow velocity of the first fluid does not decrease. For this reason, the heat transfer efficiency of the first fluid is further improved.

According to the fifth aspect of the present invention, the long axis of the double tube heat exchanger has a length of at least twice the length of the short axis of the double tube heat exchanger. Since the surface area of the outer wall surface of the double-pipe heat exchanger that comes into contact with the first fluid can be increased, the double-pipe heat exchanger is extended in the downstream flow pipe in the width direction dimension of the upstream flow pipe. Even if it is installed in the inside, it is possible to suppress a decrease in the heat exchange performance of the double-pipe heat exchanger.

According to the sixth aspect of the present invention, the double-tube oil cooler is installed in the downstream tank along an extension of the width direction of the tube, so that the oil cooler flows from the tube into the downstream tank. In the cooling water flow, the portion having the highest flow velocity can be brought into contact with the outer wall surface of the entire outer tube. As described above, since the specification of the cooling water side can be improved, the heat radiation performance of the entire double-pipe oil cooler can be further enhanced.

Further, the cross-sectional shape of the outer tube is made flat in a dimension that is shorter in the transverse direction than in the vertical direction perpendicular to the width direction of the tube, and the outer tube is smaller in the width direction than the tube. By reducing the lateral dimension (outer diameter dimension), it is possible to increase the surface area of the outer tube in which the outer wall surface comes into contact with the cooling water. Even if it is installed within an extension of the dimensions, it is possible to suppress a decrease in the heat radiation performance of the double-pipe oil cooler.

According to the present invention, the outer tube of the double-tube oil cooler is formed by caulking the concave portions of the pair of forming plates, and the caulked portion of the outer tube is formed. A double-tube oil cooler is arranged in the downstream tank so as to be located on the axis of the tube.
For this reason, the swirling portion of the cylindrical pipe can smoothly divide the flow of the cooling water flowing from the tube into the downstream tank, so that the flow of the cooling water near the outer wall surface of the outer cylindrical pipe on the upstream flow path pipe side can be reduced. There is no stagnation of one fluid,
The flow rate of the first fluid does not decrease.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

[Configuration of First Embodiment] FIGS. 1 to 5 show a first embodiment of the present invention.
FIG. 1 is a view showing a double-pipe oil cooler built in a lower tank of a radiator, and FIG. 2 is a view showing a flow of cooling water flowing out of a tube and a double-pipe oil cooler. It is a figure showing a relation.

The double-tube oil cooler 1 of this embodiment is
This is equivalent to the double-pipe heat exchanger of the present invention, and cools oil (corresponding to the second fluid) with cooling water (corresponding to the first fluid) of an automobile engine. The double-pipe oil cooler 1 is built in a lower tank 3 that is joined to downstream ends (lower ends) of a plurality of tubes 2 of a radiator that is installed in a place that is susceptible to the traveling wind of an automobile. It is an oil cooler with a built-in radiator.

The plurality of tubes 2 correspond to the upstream side flow tube of the present invention, and are formed of a metal material having excellent heat conductivity such as an aluminum alloy in a flat shape (an oval shape). And an upstream cooling water passage 4 through which cooling water flows downward from above. When the cooling water passes through the upstream cooling water passages 4 of the plurality of tubes 2, the cooling water exchanges heat with air passing through the outer wall surface of the tubes 2 and is cooled. Note that a heat transfer promoting member such as a corrugated fin (not shown) is joined between the adjacent tubes 2.

The lower tank 3 corresponds to the downstream flow passage tube of the present invention, and is caulked with a core plate 5 made of a metal material such as an aluminum alloy and a sealing material 6 such as a rubber packing. And the like, and has a downstream cooling water channel 8 that flows in from a plurality of tubes 2 therein.

The core plate 5 has a plurality of tubes 2
An insertion hole 5a which is joined by brazing or the like in a state where the downstream end portion is inserted is formed. Capsule 7
Is a resin tank integrally formed in a bottomed container shape (a substantially U-shaped cross section) from a resin material such as nylon resin. A nipple 10 of the double-tube oil cooler 1 is provided on a side wall of the capsule 7. Circular insertion hole 7 to be inserted
a are formed. Note that the capsule 7 may be formed of a metal material.

Next, the structure of the double-tube oil cooler 1 will be described with reference to FIGS. Here, FIGS. 3 to 5 are views showing the double-pipe oil cooler 1. The double-pipe oil cooler 1 includes two nipples 10 as joint members, a two-part type outer cylinder pipe 11 connected to the nipples 10, and an inner cylinder arranged in the outer cylinder pipe 11. Tube 1
2, an oil passage 13 in which oil flows back inside, a cooling water passage 14 in which cooling water flows back inside, and an oil passage 13
And the inner fins 15 disposed therein.

The two nipples 10 are respectively inserted into insertion holes 7 a of the capsule 7, and a sealing member 16 such as an O-ring is mounted between the nipple 10 and the inner wall surface of the capsule 7. On the outer circumference of the tubular portion of the nipple 10 protruding from the outer wall surface of the capsule 7, an outer peripheral thread 19 into which a nut 17 and an external connection pipe 18 are fitted is formed.

The outer connecting pipe 18 has an inlet connecting pipe connected to the double-pipe oil cooler 1 and a torque converter (not shown) of an automatic transmission for a vehicle, and an outlet connecting pipe connected to an oil pump or an oil pump. It is connected to an oil pan (not shown). The flow direction of the oil may be a torque converter → double-pipe oil cooler 1 → oil pump or oil pan, or may be an oil pump or oil pan → double-pipe oil cooler 1 → torque converter or other.

The outer tube 11 is made of a metal material such as aluminum alloy or brass.
The periphery is joined by caulking to form a flat shape. The cross-sectional shape of the outer tube 11 is such that the long axis (long dimension portion) is arranged along the flow direction of the cooling water that has flowed out of the tube 2 into the lower tank 3, and has flowed out of the tube 2 into the lower tank 3. It has an oval shape in which a short axis (short dimension portion) is arranged so as to face the flow direction of the cooling water.

The dimension (HO) of the long axis of the outer tube 11 is
It has a length that is at least twice (in this example, 3.4 times) the dimension (WO) of the short axis of the outer tube 11. And the cross-sectional shape of the upper end part and the lower end part of the outer tube 11 is semicircular (arc part 2).
0), and the cross-sectional shape of the intermediate portion is a linear shape (a straight portion 21 having a vertical dimension LS). The swaged portion 22 of the outer tube 11 is disposed in the cooling water passage 8 on the downstream side of the lower tank 3 such that the swaged portion 22 is located on the axis of the tube 2. As illustrated in FIG. 1, the outer tube 11 has a dimension in the width direction of the tube 2 (for example, the tube 2).
The outer diameter of the WT is fixed to the nipple 10 so as to be located within an extension line of the WT (dashed line in the drawing).

The inner tube 12 is made of a metal material such as aluminum alloy or brass, and is formed in an oval shape concentric with the outer tube 11. The oil passage 13 is a portion corresponding to the annular passage of the present invention, and is formed in an oval ring shape between the outer tube 11 and the inner tube 12. The cooling water passage 14 is open at both ends in the direction in which the plurality of tubes 2 are arranged, and the cooling water flowing in the downstream cooling water passage 8 passes therethrough. The inner fin 15 is a member for contributing to an improvement in oil-side heat transfer efficiency.

[Operation of First Embodiment] Next, the operation of the double-pipe oil cooler 1 of the present embodiment will be briefly described with reference to FIGS.

When the automobile engine is operated and the oil pump is driven, the oil for lubricating the sliding portion of the automobile engine passes through the external connecting pipe 18 on the inlet side and the oil passage of the double-tube oil cooler 1. After being returned to the inside 13 and exchanging heat with cooling water, it is discharged from the double-tube oil cooler 1 through the external connection pipe 18 on the outlet side. The oil passage 1
Since the inner fins 15 are arranged in 3, the oil-side heat transfer efficiency is high.

On the other hand, when the water pump is driven by driving the automobile engine, the cooling water flowing out of the water jacket of the automobile engine flows into the upper tank of the radiator. Then, the cooling water distributed to each tube 2 is cooled by exchanging heat with air when passing through the tubes 2, and then flows out from the downstream end of each tube 2 into the lower tank 3.

The cooling water flowing into the lower tank 3 from the downstream end of each tube 2 is smoothly divided by the caulking portion 22 of the double-tube oil cooler 1. Since the double-pipe oil cooler 1 is installed at the portion where the flow rate of the cooling water is the fastest, and the double-pipe oil cooler 1 has the straight portion 21, the outer wall surface of the outer pipe 11 The cooling water that has contacted the air flows smoothly without stagnation. Thereby, the cooling water side heat transfer efficiency is further improved, so that the oil flowing in the oil passage 13 is efficiently cooled.

[Effects of the First Embodiment] As described above, in the present embodiment, the double-pipe oil cooler 1 is used to reduce the width of the tube 2 in the portion where the flow velocity of the cooling water is the highest, that is, in the lower tank 3. It is installed within an extension of the dimension in the direction (WT: for example, the outer diameter dimension of the tube 2). Thereby, since the water flow of the cooling water flowing out of each tube 2 can be effectively used, the heat radiation performance of the entire double-tube oil cooler 1 can be further enhanced.

The double-tube oil cooler 1 is a flat oval double tube having a major axis dimension (HO) twice or more as large as a minor axis dimension (WO). By making the dimension of the short axis of the double-tube oil cooler 1 smaller than the diameter, the surface area of the outer wall surface that comes into contact with the cooling water can be increased. As a result, the short axis dimension (WO) of the double pipe oil cooler 1 is changed to the outer diameter dimension (W) of the tube 2.
Even if it is smaller than T), it is possible to suppress a decrease in the heat radiation performance of the double-pipe oil cooler.

Even when the heat radiation area of the double-tube oil cooler 1 is set to be the same as that of the cylindrical double-tube oil cooler, the long-axis dimension (HO) of the tube 2 along the longitudinal direction is reduced. By making the flat tube into a flat elliptical shape that is at least twice as long as the short axis dimension (WO) orthogonal to the longitudinal direction of 2, the tube 2 and the lower tank 3 can be prevented from increasing in width. In addition, it is possible to prevent the radiator from increasing in width. Here, even if the width of the downstream tank such as the lower tank 3 is made to substantially match the width of the tube 2, the double-tube oil cooler 1 can be installed in the downstream tank. Since the size can be reduced, a compact radiator having a small width can be obtained.

In this embodiment, the double-pipe oil cooler 1 is installed in the lower tank 3 of the down-flow radiator, but the double-pipe oil cooler 1 is installed in the downstream tank of the cross-flow radiator. May be installed. In this case, as described above, the number of tubes of the cross-flow type radiator is smaller than that of the down-flow type radiator, and the flow rate of the cooling water flowing out of each tube is faster than that of the down-flow type radiator. Further, even under an engine high load condition in which the flow rate of the cooling water flowing through the engine cooling water circuit, particularly the radiator, increases, the flow velocity of the cooling water flowing out of each tube is high. Therefore, when the double-pipe oil cooler 1 of the present embodiment is used under these conditions, the cooling water-side heat transfer efficiency is improved as compared with the present embodiment, and the entire double-pipe oil cooler 1 is used. Can further improve the heat radiation performance.

[Second Embodiment] FIG. 6 shows a second embodiment of the present invention and is a view showing a double-pipe oil cooler built in a lower tank of a radiator.

In this embodiment, the lower tank 3 of the radiator of the down-flow type in which the tubes 2 are arranged in two rows in the front-rear direction of the automobile (the cross-sectional shape of the capsule 7 is substantially horseshoe-shaped) is placed in the double tank. A tubular oil cooler 1 is installed. Although the inner fin disposed in the oil passage 13 formed between the outer tube 11 and the inner tube 12 is omitted, the inner fin is naturally installed to enhance the oil-side heat transfer efficiency. You may.

In the present embodiment, the double-tube oil cooler 1
Is smaller than the width dimension (WT) of the two tubes 2 arranged in tandem, and the double-tube oil cooler 1 is smaller than the width dimension (WT) of the two tubes 2. A double-pipe oil cooler 1 is installed in the lower tank 3 so as to fit within the extension line (dashed line in the drawing). The cross-sectional shape of the upper end and the lower end of the double-tube oil cooler 1 is semi-elliptical.

[Other Embodiments] In the present embodiment, the present invention is applied to a double-pipe oil cooler 1 for cooling a torque converter oil of an automatic transmission for an automobile, but the present invention is applied to an automobile, a ship, an aircraft, and a railway. The present invention may be applied to a double-pipe heat exchanger that cools engine oil of an engine mounted on a vehicle. Further, the present invention may be applied to a double-pipe heat exchanger that cools oil such as automatic transmission oil, lubricating oil, and operating oil such as power steering.

Further, the present invention relates to a double-tube type condenser for condensing and liquefying a refrigerant by exchanging heat with a cooling medium (air or cooling water), and evaporating the refrigerant by exchanging heat with a heating medium (air or hot water). The present invention may be applied to a double tube refrigerant evaporator for vaporizing. The present invention may be applied to a double-pipe heat exchanger that exchanges heat between the gas flowing through the outer wall surface of the outer tube and the gas flowing through the outer tube. The present invention may be applied to a double-pipe heat exchanger in which heat is exchanged between a liquid flowing through the outer tube and a gas flowing through the outer tube.

In this embodiment, the double-tube oil cooler 1
The cross-sectional shape of the double-tube heat exchanger such as the double-tube oil cooler 1 is changed to an elliptical shape having a straight portion 21 as shown in FIG. Alternatively, as shown in FIG. 7B, the cross-sectional shape of the double-pipe heat exchanger such as the double-pipe oil cooler 1 may be a simple elliptical shape.

As shown in FIG. 8A, the cross-sectional shape of the double-tube heat exchanger such as the double-tube oil cooler 1 may be a pentagonal shape having the straight portion 21. As shown in FIG. 8B, the cross-sectional shape of the double-pipe heat exchanger such as the double-pipe oil cooler 1 may be a triangular shape having the straight portion 21. Further, the cross-sectional shape of the double-pipe heat exchanger such as the double-pipe oil cooler 1 may be polygonal such as rectangular.

In this embodiment, as shown in FIG. 9 (a), the oval double-tube oil cooler 1 is installed within an extension of the outer diameter (WT) of the radiator tube 2. As shown in FIG. 9B, an oval double-tube oil cooler 1 may be installed within an extension of the inner diameter (WT) of the tube 2. That is, the dimension in the width direction of the tube 2 may be based on the outer diameter of the tube 2 or may be based on the inner diameter of the tube 2.

Further, as shown in FIG. 9C, the dimension in the width direction connecting the centers of the thicknesses of the tubes 2 may be used as a reference. As shown in FIG. 9C, when the downstream end of the tube 2 is expanded, the water flow of the cooling water tends to expand and the lower tank (lower tank) ), It is desirable to adopt the outer diameter of the tube 2 as the dimension in the width direction of the tube 2.

In this embodiment, the double-tube oil cooler 1 with a built-in radiator using the tube 2 as the upstream flow pipe and the lower tank 3 as the downstream flow pipe has been described as an example. Even when the present invention is applied to a triple-pipe heat exchanger (triple-pipe oil cooler) including an inlet-side flow pipe as a flow pipe and an outermost tubular pipe (housing) as a downstream flow pipe. good.

Further, a metal pipe,
A resin pipe, a rubber hose, or the like may be used, and a metal tank, a tube, an oil pan-shaped container, a metal pipe, a resin pipe, or the like may be used as the downstream channel pipe. The cross-sectional shape of the upstream-side channel pipe may be any shape such as a flat shape such as an elliptical shape, an oval shape, and a rectangular shape, a circular shape, or a polygonal shape.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a double-pipe oil cooler built in a lower tank of a radiator (first embodiment).

FIG. 2 is a cross-sectional view showing a relationship between a water flow of cooling water flowing out of a tube and a double-pipe oil cooler (first embodiment).

FIG. 3 is a plan view showing a double-pipe oil cooler (first embodiment).

FIG. 4 is a front view showing a double-pipe oil cooler (first embodiment).

FIG. 5 is a partial sectional view showing a double-pipe oil cooler (first embodiment).

FIG. 6 is a sectional view showing a double-pipe oil cooler built in a lower tank of a radiator (second embodiment).

7A is a cross-sectional view illustrating a double-pipe oil cooler, and FIG. 7B is a cross-sectional view illustrating a double-pipe oil cooler.

8A is a cross-sectional view illustrating a double-pipe oil cooler, and FIG. 8B is a cross-sectional view illustrating a double-pipe oil cooler.

9A is a cross-sectional view showing a double-pipe oil cooler, and FIG. 9B is a cross-sectional view showing a double-pipe oil cooler.
(C) is a sectional view showing a double-pipe oil cooler.

FIG. 10 is a cross-sectional view showing a double-pipe oil cooler built in a downstream tank of a radiator (prior art).

FIG. 11 is a cross-sectional view showing the relationship between the flow of cooling water flowing out of a tube and a double-pipe oil cooler (prior art).

FIG. 12 is a cross-sectional view showing a double-pipe oil cooler incorporated in a downstream tank of a radiator (prior art).

[Explanation of symbols]

 Reference Signs List 1 double pipe oil cooler (double pipe heat exchanger) 2 tube (upstream flow path pipe) 3 lower tank (downstream flow path pipe, downstream tank) 4 upstream cooling water path 8 downstream cooling water path 10 nipple (Connection joint) 11 Outer tube 12 Inner tube 13 Oil passage (annular passage) 14 Cooling water passage 15 Inner fin 18 External connection tube 22 Caulked portion 11a Mold plate 11b Mold plate

Claims (7)

[Claims] 1. A second flow passage disposed in a downstream flow passage into which a first fluid flows from an upstream flow passage and exchanging heat with the first fluid.
A double-pipe heat exchanger having an annular passage through which a fluid flows, wherein the double-pipe heat exchanger is an extension of the width dimension of the upstream flow path pipe in the downstream flow path pipe. It has a flat cross-section having a dimension that is shorter in the horizontal direction than in the vertical direction orthogonal to the width direction of the upstream flow path pipe, and is larger than the width dimension of the upstream flow path pipe. The double-tube heat exchanger has a small horizontal dimension. 2. The double-pipe heat exchanger according to claim 1, wherein the double-pipe heat exchanger is provided with a first fluid flowing from the upstream flow pipe into the downstream flow pipe. A polygonal shape having a major axis arranged along the inflow direction, and a minor axis arranged so as to oppose the inflow direction of the first fluid flowing into the downstream channel pipe from the upstream channel pipe. A double-pipe heat exchanger having a cross section. 3. The double-pipe heat exchanger according to claim 1, wherein the double-pipe heat exchanger is provided with a first fluid that flows from the upstream flow pipe into the downstream flow pipe. An elliptical shape having a major axis arranged along the inflow direction, and a minor axis arranged so as to face the inflow direction of the first fluid flowing from the upstream flow pipe into the downstream flow pipe. A double-pipe heat exchanger having a cross section. 4. The double-pipe heat exchanger according to claim 1, wherein the double-pipe heat exchanger includes a first fluid that flows from the upstream flow pipe into the downstream flow pipe. An elliptical shape having a major axis arranged along the inflow direction, and a minor axis arranged to face the inflow direction of the first fluid flowing from the upstream flow pipe into the downstream flow pipe. A double-pipe heat exchanger having a cross section of: 5. The double-pipe heat exchanger according to claim 2, wherein a long axis of the double-pipe heat exchanger is the double-pipe heat exchanger. A double-pipe heat exchanger having a length that is at least twice the length of the short axis of the exchanger. 6. The double-pipe heat exchanger according to claim 1, wherein the upstream flow pipe has a plurality of tubes forming an upstream cooling water passage therein. In the downstream flow pipe, the cooling water as the first fluid flows in from one end of the plurality of tubes, and forms a downstream cooling water passage wider than the upstream cooling water passage therein. A double-tube heat exchanger, wherein the double-tube heat exchanger is a double-tube oil cooler installed in a row direction of the plurality of tubes in the downstream tank. The tubular oil cooler has an elliptical outer cylindrical tube in which cooling water contacts an outer wall surface, an elliptical inner cylindrical tube disposed inside the outer cylindrical tube and concentric with the outer cylindrical tube, and an outer cylindrical tube. Formed between the inner wall surface and the outer wall surface of the inner cylindrical tube, A double pipe type, comprising: an oil passage, and a connection joint for connecting the outer cylinder tube and the external connection tube to recirculate oil as the second fluid in the oil passage. Heat exchanger. 7. The double-pipe heat exchanger according to claim 6, wherein the outer pipe is formed by caulking concave portions of a pair of forming plates that are concave in a dish shape, and forming the outer cylindrical tube. The double-pipe heat exchanger is characterized in that the pipe-type heat exchanger is arranged in the downstream-side tank such that a swaged portion of the outer tube is located on the axis of the tube.