US20130075071A1

US20130075071A1 - Heat Exchanger

Info

Publication number: US20130075071A1
Application number: US13/635,398
Authority: US
Inventors: Mitsuo Yabe; Shunichi Sakuragi
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 2010-06-23
Filing date: 2011-06-23
Publication date: 2013-03-28
Also published as: CN102812322A; WO2011162329A1; JP2012007778A

Abstract

The invention provides a heat exchanger having a fin with an optimum thickness, and thus being capable of providing a superior cooling effect while having an excellent workability. A heat exchanger is designed to be mounted on a construction machine used on a construction site and is configured to cool heated cooling water. The heat exchanger includes a tube that allows the cooling water to flow therein, and a fin that is joined to the tube and has an imperforate and planar heat radiation surface. The thickness of the fin is greater than 0.2 mm but is equal to or less than 0.4 mm. Further, aluminum is selected as the material for the tube and the fin. The tube and the fin are joined to each other with an aluminum brazing rod.

Description

TECHNICAL FIELD

The present invention relates to a heat exchanger, such as a radiator and an oil cooler for cooling heated cooling water and heated oil as well as an aftercooler for cooling supply air for combustion.

BACKGROUND ART

Conventionally, engines that generate power by burning fuel are cooled by a cooling medium such as water (hereinafter simply referred to as “cooling water”). The temperature of the cooling water after cooling the engine is high, and therefore the cooling water needs to be cooled. For cooling the cooling water, a heat exchanger is used (see, for example, Patent Literatures 1 and 2).
The heat exchanger includes a plurality of tubes that allow the cooling water to flow therein, and fins disposed between the tubes so as to transfer heat from the tubes. The fins are appropriately bent and disposed between the tubes so as to be in contact with the tubes. The cooling water flowing within the tubes is cooled by heat exchange with outside air through the fins disposed between the tubes.

CITATION LIST

Patent Literature(s)

Patent Literature 1: JP-A-60-187655

Patent Literature 2: JP-A-2003-83691

SUMMARY OF THE INVENTION

Problem(s) to be Solved by the Invention

There has been a demand for reducing the thickness of the fins of the above-described heat exchanger in order to have advantages in manufacturing. However, if the thickness of the fins is excessively reduced, the heat transfer between the tubes and the fins becomes poor, which may impair the cooling effect.
On the other hand, if the thickness of the fins is excessively increased in order to increase the heat transfer between the tubes and the fins, it becomes difficult to perform bending processing. Further, the draft resistance of the outside air flowing through the fins is increased to make the air inside the fins more likely to stay in the fins, which may also impair the cooling effect.
If such a heat exchanger is used in a construction machine, the fins may be clogged with dust of gravel and the like contained in outside air flowing through the fins. In particular, a corrugated fin for a heat exchanger disclosed in Patent Literature 2 includes a large number of louvers that are formed by slitting and bending processing, and these louvers are easily clogged with dust. Thus, the draft resistance of outside air is significantly increased, which may affect the heat exchange effect.
The invention has been made in view of the above problems, and an object of the invention is to provide a heat exchanger having a fin with an optimum thickness, and thus being capable of providing a superior cooling effect while having an excellent workability.

Means for Solving the Problem(s)

In order to solve the above problems, the invention provides a heat exchanger described below.
According to an aspect of the invention, there is provided a heat exchanger that cools a heated cooling medium. The heat exchanger includes: a tube that allows the cooling medium to flow therein; and a fin that is joined to the tube and has a heat radiation surface that is entirely imperforate and planar. The thickness of the fin is greater than 0.2 mm but is equal to or less than 0.4 mm.
The phrase “a heat radiation surface that is entirely imperforate and planar” as used herein refers to a heat radiation surface without openings such as the louvers described in Patent Literature 2. Accordingly, the heat radiation surface may be any heat radiation surface that does not have openings. That is, examples of heat radiation surface may include not only a completely flat heat radiation surface, but also an uneven heat radiation surface as shown in FIG. 2.
According to the above aspect of the invention, since the thickness of the fin is greater than 0.2 mm but is equal to or less than 0.4 mm, heat transfer from the tube to the fin can be increased with a preferred thickness for the slitting and bending processing while the draft resistance of the outside air flowing through the fin can be maintained at a preferred level. Thus, it is possible to achieve an excellent cooling effect when cooling the cooling water.
In the heat exchanger according to the above aspect of the invention, it is preferable that aluminum be selected as the material for the tube and the fin.
According to the above aspect of the invention, since aluminum having a very high thermal conductivity may be selected as the material for the tube and the fin, it is possible to increase the amount of heat transfer between the tube and the fin, and thus to achieve an excellent cooling effect when cooling the cooling water. It is to be noted that an aluminum brazing rod made of the same type of metal as the tube and the fin may be used as a brazing material for joining the tube and the fin to each other so as to also ensure thermal conductivity at the joint portion.
In the heat exchanger according to the above aspect of the invention, it is preferable that copper be selected as the material for the tube and the fin, and that the thickness of the fin be greater than 0.2 mm but be equal to or less than 0.3 mm
According to the above aspect of the invention, since copper having a very high thermal conductivity may be selected as the material for the tube and the fin, it is possible to increase the amount of heat transfer between the tube and the fin, and thus to achieve an excellent cooling effect when cooling the cooling water. It is to be noted that a copper-based brazing material made of the same type of metal as the tube and the fin may be used for joining the tube and the fin to each other so as to also ensure thermal conductivity at the joint portion.
The heat exchanger according to the above aspect of the invention may preferably be mounted on a construction machine.
According to the above aspect of the invention, even if the heat exchanger is mounted on a construction machine, it is possible to prevent the fin from being clogged with dust of gravel and the like contained in outside air, and thus to allow the outside air to flow into and out of the fin in a preferable manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall illustration showing a heat exchanger according to an exemplary embodiment of the invention.

FIG. 2 is a cut-away perspective view of a part of the heat exchanger.

FIG. 3 is a front view illustrating a fin as viewed along an outside-air flowing direction.

FIG. 4 is a graph showing heat exchange properties according to a thickness of the fin in the case where the interval between tubes is set to 10 mm; the interval between bent portions of the fin is set to 2 mm; and aluminum is selected as the material for the tubes and the fin.

FIG. 5 is a graph showing changes in a heat removal rate according to the thickness of the fin in the case where the interval between tubes is set to 8 mm; the interval between bent portions of the fin is set to 4 mm; and aluminum is selected as the material for the tubes and the fin.

FIG. 6 is a graph showing changes in the heat removal rate according to the thickness of the fin in the case where the interval between tubes is set to 5.6 mm; the interval between bent portions of the fin is set to 5.6 mm; and aluminum is selected as the material for the tubes and the fin.

FIG. 7 is a graph showing changes in the heat removal rate according to the thickness of the fin in the case where the interval between tubes is set to 10 mm; the interval between bent portions of the fin is set to 2 mm; and copper is selected as the material for the tubes and the fin.

FIG. 8 is a graph showing changes in the heat removal rate according to the thickness of the fin in the case where the interval between tubes is set to 8 mm; the interval between bent portions of the fin is set to 4 mm; and copper is selected as the material for the tubes and the fin.

FIG. 9 is a graph showing changes in the heat removal rate according to the thickness of the fin in the case where the interval between tubes is set to 5.6 mm; the interval between bent portions of the fin is set to 5.6 mm; and copper is selected as the material for the tubes and the fin.

FIG. 10 is a front view illustrating a modification of the fin as viewed along an outside-air flowing direction.

FIG. 11 is a perspective view of another modification of the fin.

DESCRIPTION OF EMBODIMENT(S)

First Exemplary Embodiment

A heat exchanger according to an exemplary embodiment of the invention will be described below with reference to the attached drawings.
FIG. 1 illustrates a heat exchanger 1 according to an exemplary embodiment of the invention.
The heat exchanger 1 is designed to be mounted on construction machines used on construction sites and machines such as transport vehicles. The heat exchanger 1 is used as a radiator that cools cooling water (a cooling medium) which cools an engine mounted on such a machine, by heat exchange with outside air.
The heat exchanger 1 roughly includes a frame 10 having a frame shape, and a heat exchanger main body 20 disposed in the frame 10.
The frame 10 includes an inlet tank 11 and an outlet tank 12 that are disposed in the vertical direction of the drawing, and support plates 13 and 14 each connecting the corresponding lateral ends of the inlet tank 11 and the outlet tank 12 to each other.
The inlet tank 11 is located on an upper side of the heat exchanger main body 20, and is configured to introduce cooling water into tubes 21 of the heat exchanger main body 20. On a lateral part of the inlet tank 11, an inlet 11A for introducing the cooling water fed from the engine is provided. Further, on a top of the inlet tank 11, a feed-water inlet 15 for receiving cooling water is provided. It is to be noted that the inlet 11A is connected to a water jacket (not shown) of the engine with a hose.
The outlet tank 12 is located below the heat exchanger main body 20, and is configured to discharge the cooling water from the tubes 21 of the heat exchanger main body 20. On a lateral part of the outlet tank 12, an outlet 12A for feeding the cooling water to the engine. It is to be noted that the outlet 12A is connected to a water pump (not shown) with a hose.
Each of the support plates 13 and 14 connects the corresponding lateral ends of the opposing inlet tank 11 and outlet tank 12 to each other so as to support these tanks 11 and 12.
FIG. 2 is a cut-away perspective view of a part of the heat exchanger 1.
The heat exchanger main body 20 includes the plurality of tubes 21 that allow the cooling water to flow therein and are arranged at predetermined intervals, and a plurality of wave-shaped fins 25 that are disposed between the tubes 21 so as to be joined to the tubes 21. This heat exchanger main body 20 is configured to exchange heat between the cooling water and outside air through the fins 25 while the cooling water passes through the tubes 21 extending from the inlet tank 11 to the outlet tank 12. The cooling water is cooled by this heat exchange process.
Each of the tubes 21 is flat and hollow as illustrated in FIGS. 1 and 2. The tube 21 is disposed such that upper and lower ends communicate with the inlet tank 11 and the outlet tank 12, respectively. In other words, the cooling water flows from the inlet tank 11 into the tube 21, exchanges heat with outside air while passing through the inside of the tube 21, and flows out of the tube 21 into the outlet tank 12.
Four tubes 21 are arranged to each of the fins 25 in a depth direction (a flowing direction of the outside air). A longitudinal dimension L1 of each of the tubes 21 in the cross section is set to 22 mm, whereas a longitudinal dimension of each of the fins 25 is 100 mm. Further, an internal width dimension L2 of each of the tubes 21 is set to 1.6 mm A gap L3 (FIG. 3) between the adjacent tubes 21 in the width direction may be set to an appropriate distance such as 10 mm, 8 mm, and 5.6 mm. In the illustrated example, the gap L3 is set to 8 mm.
FIG. 3 is a front view illustrating one of the fins 25 as viewed along the outside-air flowing direction.
As illustrated in FIGS. 2 and 3, the fin 25 is arranged to connect the tubes 21 to each other, and is joined to the tubes 21 such that heat is transferred between the fin 25 and the tubes 21 on opposite sides of the fin 25.
The fin 25 is generally referred to as a “corrugated fin”, and is formed by processing a thin plate-shaped aluminum base material into a shape of waves with predetermined intervals. That is, the fin 25 has substantially triangular openings in the side view so as to allow outside air to flow into or out of the fin 25.
Further, a heat radiation surface of the fin 25 is processed by pressing using a die or the like into an uneven shape in the flowing direction of outside air, thereby increasing an area of the heat radiation surface. The heat radiation surface is entirely imperforate and planar, and does not have louvers formed by the slitting and bending processing. Accordingly, even if the heat exchanger 1 having the fins 25 described above is mounted on a construction machine, the heat exchanger 1 can reliably provide functions of a radiator without the risk of clogging with dust.
Further, a thickness L4 of the fin 25 is greater than 0.2 mm but is equal to or less than 0.4 mm. An interval L5 between bent portions 26 of the fin 25 may be set to an appropriate distance such as 2 mm, 4 mm, and 5.6 mm. The interval L5 is preferably set so as to satisfy L5=L3 ×(0.5 through 1.1).
As the material for the above-described tubes 21 and the fins 25, aluminum is selected. The fin 25 is joined at the bent portions 26 to the tubes 21 by using an aluminum brazing rod as a brazing material, thereby achieving a high thermal conductivity.
It is to be noted that, in order to enhance the thermal conductivity between the tubes 21 and the fin 25, a thin film layer (e.g., a carbon fiber sheet) having a higher thermal conductivity than aluminum (i.e., the base material) may be provided on both surfaces of the fin 25. Alternatively, such a thin film layer may be provided at each joint portion between the tubes 21 and the fin 25.
The following describes the results of a simulation on the thus configured heat exchanger 1.
Graphs 1 through 3 of FIGS. 4 through 6 show the rate of change of the net heat-removal effect according to the thickness L4 of the fin 25 in the case where aluminum was selected as the material for the tubes 21 and the fin 25. This rate of change of the net heat-removal effect indicates the rate of change of the expected cooling effect of the cooling water, and is calculated by the difference between the rate of change of the amount of heat removal and the rate of change of the amount of heat removal due to a loss in the outside-air flow amount.
The rate of change of the net heat-removal effect was calculated with reference to the case where the thickness L4 of the fin 25 was set to 0.13 mm. In the measurement, the thickness L4 of the fin 25 was set to 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1 mm.
Graph 1 of FIG. 4 shows an example in which the gap L3 between the tubes 21 was set to 10 mm, and the interval L5 between the bent portions 26 of the fin 25 was set to 2 mm. Graph 2 of FIG. 5 shows an example in which the gap L3 between the tubes 21 was set to 8 mm, and the interval L5 between the bent portions 26 of the fin 25 was set to 4 mm. Graph 3 of FIG. 6 shows an example in which the gap L3 between the tubes 21 was set to 5.6 mm, and the interval L5 between the bent portions 26 of the fin 25 was set to 5.6 mm.
It is to be noted that the settings used in these examples allow even outside air containing a large amount of dust of gravel and the like to easily flow into and out of the fin 25 with less possibility of clogging the fin 25.
As illustrated in Graphs 1 through 3 of FIGS. 4 through 6, in the case where the thickness L4 of the fin 25 was set to 0.2 mm, the rate of change of the net heat-removal effect was significantly increased compared to the case where the thickness L4 was set to 0.13 mm. It is to be noted that, in the case where the thickness L4 of the fin 25 was set to 0.4 mm or greater, the rate of change of the net heat-removal effect tends to be decreased. Further, in the case where the thickness L4 of the fin 25 was set to 0.4 mm or greater, it may also be difficult to perform bending processing.
As can be seen from the above, in the case where the thickness L4 of the fin 25 is greater than 0.2 mm but is equal to or less than 0.4 mm, heat transfer from the tubes 21 to the fin 25 can be increased while having a preferred thickness for bending processing. Further, the draft resistance of the outside air flowing through the fin 25 can be maintained at a preferred level. Thus, it is possible to achieve an excellent cooling effect when cooling the cooling water.
Further, in this heat exchanger 1, aluminum having a very high thermal conductivity is selected as the material for the tubes 21 and the fins 25. Therefore, it is possible to increase the amount of heat transfer between the tubes 21 and the fins 25, and thus to achieve an excellent cooling effect when cooling the cooling water.

Second Exemplary Embodiment

Next, a description will be given of a heat exchanger according to a second exemplary embodiment that is different from the above-described first exemplary embodiment.
The heat exchanger of the second exemplary embodiment is different from the heat exchanger 1 of the first exemplary embodiment in that copper is selected as the material for the tubes 21 and the fins 25 of the heat exchanger 1 of the first exemplary embodiment. The other components of the heat exchanger of the second exemplary embodiment have the same configurations as those of the heat exchanger 1 of the first exemplary embodiment.
Accordingly, the following describes an evaluation test in the case where copper is selected as the material for the tubes 21 and the fins 25.
It is to be noted that the fin 25 is joined at the bent portions 26 to the tubes 21 with a copper-based brazing material, thereby achieving a high thermal conductivity.
Graphs 4 through 6 of FIGS. 7 through 9 show the rate of change of the net heat-removal effect according to the thickness L4 of the fin 25 in the case where copper was selected as the material for the tubes 21 and the fin 25.
The method of calculating the rate of change of the net heat-removal effect and the reference used in the calculation are the same as those used in the simulation in the above first exemplary embodiment, and the thickness L4 of the fin 25 was set to 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1 mm.
Graph 4 of FIG. 7 shows an example in which the gap L3 between the tubes 21 was set to 10 mm, and the interval L5 between the bent portions 26 of the fin 25 was set to 2 mm. Graph 5 of FIG. 8 shows an example in which the gap L3 between the tubes 21 was set to 8 mm, and the interval L5 between the bent portions 26 of the fin 25 was set to 4 mm. Graph 6 of FIG. 9 shows an example in which the gap L3 between the tubes 21 was set to 5.6 mm, and the interval L5 between the bent portions 26 of the fin 25 was set to 5.6 mm.
As illustrated in Graphs 4 through 6 of FIGS. 7 through 9, in the case where the thickness L4 of the fin 25 was set to 0.2 mm, the rate of change of the net heat-removal effect was significantly increased compared to the case where the thickness L4 was set to 0.13 mm. It is to be noted that, in the case where the thickness L4 of the fin 25 was set to 0.4 mm or greater, the rate of change of the net heat-removal effect tends to be decreased. Further, in the case where the thickness L4 of the fin 25 was set to 0.4 mm or greater, it may also be difficult to perform bending processing.
As can be seen from the above, in the case where the thickness L4 of the fin is greater than 0.2 mm but is equal to or less than 0.4 mm, preferably equal to or less than 0.3 mm, heat transfer from the tubes 21 to the fin 25 can be increased while having a preferred thickness for bending processing. Further, the draft resistance of the outside air flowing through the fin 25 can be maintained at a preferred level. Thus, it is possible to achieve an excellent cooling effect when cooling the cooling water.
Further, in this heat exchanger, copper having a very high thermal conductivity is selected as the material for the tubes 21 and the fins 25. Therefore, it is possible to increase the amount of heat transfer between the tubes 21 and the fins 25, and thus to achieve an excellent cooling effect when cooling the cooling water.
It should be understood that the invention is not limited to the above exemplary embodiments, and variations and modifications may be made without departing from the scope of the invention.
For example, the bent shape of the fins 25 of the heat exchanger main body 20 is not limited to the example described above with reference to the drawings, but may be any appropriate shape.
FIG. 10 is a front view illustrating another fin having a different shape as that of the fin shown in FIG. 3.
More specifically, the fin 25 shown in FIG. 3 has substantially triangular openings in the side view so as to allow outside air to flow into or out of the fin 25. On the other hand, a fin 25A of a heat exchanger main body 20A shown in FIG. 10 has substantially rectangular openings in the side view so as to allow outside air to flow into or out of the fin 25A. That is, the fin 25A of FIG. 10 is designed such that bent portions 26A have a predetermined width and such that the fin 25A connects the tubes 21 to each other in a direction orthogonal to a direction in which the tubes 21 extend.
Accordingly, even if the fin 25A having the configuration described above, in the case where the thickness L4 of the fin is greater than 0.2 mm but is equal to or less than 0.4 mm as in the above simulation, heat transfer from the tubes 21 to the fin 25A can be increased while having a preferred thickness for bending processing. Further, the draft resistance of the outside air flowing through the gaps in the fin 25A can be maintained at a preferred level. Thus, it is possible to achieve an excellent cooling effect when cooling the cooling water.
In the above exemplary embodiments, the heat radiation surface of the fin 25 is formed in an uneven shape. However, the heat radiation surface of the fin 25 may be entirely flat as shown in FIG. 11. Even in this case, if the dimension of the main part is set to be within a range specified in the above exemplary embodiments of the invention, the above-mentioned object can be achieved. Further, since the heat radiation surface does not have any opening such as a louver, the risk of an increase in the draft resistance due to clogging with dust such as sand is eliminated.
In the above exemplary embodiments, a radiator has been described as an example of the heat exchanger of the invention. However, the heat exchanger is not limited to the radiator, and may be an oil cooler for cooling oil, an aftercooler for cooling a supercharged air (a supply air), or the like. Further, such a heat exchanger may have any specific configuration, and modifications may be appropriately made upon implementing the heat exchanger. For example, the positions of the inlet tank and the outlet tank may be switched.

INDUSTRIAL APPLICABILITY

The heat exchanger of the invention has a fin with an optimum thickness, and thus can be used as a heat exchanger that is capable of providing a superior cooling effect while having an excellent workability.

Explanation of Codes

1 heat exchanger; 10 frame; 11 inlet tank; 11A inlet; 12 outlet tank; 12A outlet; 13,14 support plate; 15 feed-water inlet; 20 heat exchanger main body; 21 tube; 25, 25A fin; 26, 26A bent portion; and L4 thickness.

Claims

1. A heat exchanger that cools a heated cooling medium, the heat exchanger comprising:

a tube that allows the cooling medium to flow therein; and

a fin that is joined to the tube and has a heat radiation surface that is entirely imperforate and planar, wherein

a thickness of the fin is greater than 0.2 mm but is equal to or less than 0.4 mm.

2. The heat exchanger according to claim 1, wherein aluminum is selected as a material for the tube and the fin.

3. The heat exchanger according to claim 1, wherein

copper is selected as a material for the tube and the fin; and

a thickness of the fin is greater than 0.2 mm but is equal to or less than 0.3 mm.

4. The heat exchanger according to claim 1, the heat exchanger being configured to be mounted on a construction machine.

5. The heat exchanger according to claim 2, the heat exchanger being configured to be mounted on a construction machine.

6. The heat exchanger according to claim 3, the heat exchanger being configured to be mounted on a construction machine.