US20130146263A1

US20130146263A1 - Heat exchanger

Info

Publication number: US20130146263A1
Application number: US13/529,881
Authority: US
Inventors: Jae Yeon Kim; Wan Je Cho; Yong Lee; Man Hee Park; Jongho SEON
Original assignee: Hyundai Motor Co
Current assignee: Hyundai Motor Co
Priority date: 2011-12-09
Filing date: 2012-06-21
Publication date: 2013-06-13
Also published as: CN103162554A; KR20130065389A; KR101317373B1; DE102012105588A1; JP2013122366A

Abstract

A heat exchanger may include an exhaust gas pipe having a plurality of bypass holes formed at an exterior circumference of one end and a valve mounted at another end, exhaust gas selectively flowing into the bypass holes, a case forming a radial outer flowing space, and having coolant exhaust and inflow ports, first and second headers dividing the flowing space, a first connecting member adapted to receive the exhaust gas through the bypass hole, a second connecting member, an oil flowing section including an inner pipe, an outer pipe and an oil line formed between the inner pipe and the outer pipe, and at least one heat radiating unit disposed between the exhaust pipe and the oil flowing section provided with at least one coupling pipe adapted to connect the first header with the second header.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority of Korean Patent Application Number 10-2011-0132228 filed Dec. 9, 2011, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF INVENTION

1. Field of Invention
The present invention relates to a heat exchanger. More particularly, the present invention relates to a heat exchanger that controls temperatures of operating fluids flowing in the heat exchanger by heat-exchange with exhaust gas of high temperature and coolant.
2. Description of Related Art
Generally, an engine or a transmission is required to be warmed up when initial starting of a vehicle and the engine or the transmission should be cooled during the vehicle runs. Therefore, a heat exchanger is used in the vehicle.
A heat exchanger transfers heat from high-temperature fluid to low-temperature fluid through a heat transfer surface. Such a heat exchanger reuses heat energy or controls a temperature of an operating fluid flowing therein for demanded performance. The heat exchanger is applied to an air conditioning system or a transmission oil cooler of a vehicle, and is mounted at an engine compartment.
Herein, a heat exchanger applied to an exhaust system is adapted to raise a temperature of oil used in the engine and the transmission quickly by using exhaust heat of the vehicle when initial starting of the vehicle. Therefore, the exhaust gas exchanges heat with the coolant and the oil when initial starting of the vehicle, and the oil exchanges heat with the coolant so as to lower temperatures of the engine and the transmission during the vehicle runs.
The heat exchanger applied to the exhaust system is mounted around an exhaust pipe so as to perform heat-exchange by using the exhaust gas efficiently. The exhaust gas flowing in the heat exchanger exchanges heat with the oil and the coolant.
A valve is mounted at an end of the exhaust pipe positioned in the heat exchanger. The valve is selectively opened/closed according to a running state of the vehicle so as to supply the exhaust gas to the heat exchanger or exhaust the exhaust gas through the exhaust pipe.
That is, the valve connected to the end of the exhaust pipe is closed so as to warm up engine oil, transmission oil and coolant quickly during initial warm-up after starting of the vehicle. In this case, the exhaust gas exchanges heat with the oil and the coolant during flowing in the heat exchanger. Therefore, the oil and the coolant may be warmed up quickly.
In addition, the valve connected to the end of the exhaust pipe is partially opened so as to warm up the oil and the coolant by using a portion of the exhaust gas when a temperature of the coolant is raised and a temperature of the oil is not raised.
After that, the valve is fully opened so as to prevent the exhaust gas from flowing into the heat exchanger and to exhaust the exhaust gas through the exhaust pipe when the coolant and the oil are warmed up completely. Therefore, temperatures of the coolant and the oil are not raised. Instead, the oil can be cooled by heat-exchange with the coolant.
Herein, a plurality of pipes for flowing the exhaust gas is provided in the heat exchanger, and the coolant and the oil pass an outside of the pipe. Therefore, the exhaust gas exchanges heat with the coolant and the oil.
Recently, a heat exchanger of shell and tube type is provided with reduced-diameter portions formed at interior circumferences of a plurality of pipes so as to change flow of the exhaust gas. Thereby, the heat exchanger of shell and tube type enhances heat-exchanging efficiency.
However, if pipes of shell and tube type are applied to the heat exchanger so as to change flow of the exhaust gas, manufacturing cost may increase because the reduced-diameter portions should be formed at the interior circumference of each pipe. In addition, since an exterior circumference of the pipe is smooth, turbulence is hard to be formed at the coolant. Therefore, heat-exchanging efficiency may not be increased efficiently compared with the manufacturing cost.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

SUMMARY OF INVENTION

Various aspects of the present invention provide for a heat exchanger having advantages of simultaneously warming up and cooling operating fluids according to temperatures of the operating fluids at a running state or an initial starting condition of the vehicle by using exhaust gas of high temperature and coolant.
Various aspects of the present invention provide for a heat exchanger having further advantages of improving heat-exchanging efficiency between operating fluids by promoting flow change and formation of turbulence in exhaust gas and coolant flowing in the heat exchanger.
Various aspects of the present invention provide for a heat exchanger that may include an exhaust gas pipe having a plurality of bypass holes formed at an exterior circumference of an end portion thereof and a valve mounted at the other end portion thereof, an exhaust gas selectively flowing into the bypass holes according to operation of the valve, a case disposed at a radial outer of the exhaust gas pipe so as to form a flowing space between the case and the exhaust gas pipe, and having a coolant exhaust port formed at a side thereof and a coolant inflow port formed at the other side thereof, first and second headers mounted respectively at both end portions of the case and dividing the flowing space, a first connecting member connect an end of the case to the end portion of the exhaust gas pipe and adapted to receive the exhaust gas through the bypass hole therein, a second connecting member having an end connected to the other end of the case, an oil flowing section formed between the exhaust gas pipe and the case, and including an inner pipe, an outer pipe and an oil line formed between the inner pipe and the outer pipe, the oil line being fluidly connected to an oil inflow port and an oil exhaust port, and at least one heat radiating unit disposed between the exhaust pipe and the oil flowing section, and between the case and the oil flowing section, provided with at least one coupling pipe formed by coupling at least one plate at which at least one protruding portion is formed along a length direction, and adapted to connect the first header with the second header, wherein a connecting line is formed in the coupling pipe so as for the exhaust gas flowing into the first connecting member to flow therein, and the exhaust gas flowing in the connecting line exchanges heat with coolant and transmission oil passing an outside of the coupling pipe.
The protruding portion may be integrally and/or monolithically formed at the plate by pressing.
The protruding portion may be provided with an exterior circumference and an interior circumference formed with semi-circular shape and may be disposed as spiral shape along a length direction of the plate.
Both ends of the heat radiating unit may be inserted respectively in the first header and the second header, and the protruding portion may not be formed at the both ends of the heat radiating unit.
The coupling pipe may be a circular pipe formed by a plurality of protruding portions, and an interior circumference and an exterior circumference of the coupling pipe may be formed as spiral shape such that vortex is generated at the exhaust gas flowing in the connecting line by rotation of the exhaust gas and the coolant passing the outside of the connecting line is caused to form turbulence.
The coupling pipe, in a state that protruding portions of a pair of plates are disposed so as to be protruded toward the outside, may be formed by coupling the pair of plates.
The number of the coupling pipes included in the heat radiating unit may be changed according to a diameter of the exhaust pipe and sizes of the first header and the second header.
The coupling pipes consisting of one heat radiating unit may be releasably assembled with each other.
A plurality of rows of protruding portions may be formed at one plate, and the one plate may be folded to form the heat radiating unit such that one row of protruding portions is connected to another row of protruding portions so as to form the coupling pipe.
The heat radiating unit may enclose an exterior circumference of the exhaust pipe between the exterior circumference of the exhaust pipe and the inner pipe of the oil flowing section.
The heat radiating units may be disposed apart from each other between the outer pipe of the oil flowing section and the case.
The plate may be provided with at least one flowing hole formed between the coupling pipes.
A plurality of first and second mounting holes may be formed at the first and second headers, and the both ends of the heat radiating unit may be inserted in the first and second mounting holes, respectively.
The oil exhaust port and the oil inflow port may be formed at a side and the other sided of the case corresponding to the coolant exhaust port and the coolant inflow port, respectively.
A flowing direction of the exhaust gas passing through the connecting line may be opposite to that of the transmission oil passing through the oil line and that of the coolant passing through the flowing space of the case.
The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary heat exchanger according to the present invention.

FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1.

FIG. 3 is a cross-sectional view taken along the line B-B in FIG. 1.

FIG. 4 is a perspective view of an exemplary heat radiating unit applied to a heat exchanger according to the present invention.

FIG. 5 is an exploded perspective view of an exemplary heat radiating unit applied to a heat exchanger according to the present invention.

FIG. 6 is a cross-sectional view for showing operation of an exemplary heat exchanger according to the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.
FIG. 1 is a perspective view of a heat exchanger according to various embodiments of the present invention; FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1; FIG. 3 is a cross-sectional view taken along the line B-B in FIG. 1; FIG. 4 is a perspective view of a heat radiating unit applied to a heat exchanger according to various embodiments of the present invention; and FIG. 5 is an exploded perspective view of a heat radiating unit applied to a heat exchanger according to various embodiments of the present invention.
Referring to the drawings, a heat exchanger 10 according to various embodiments of the present invention is adapted to warm up and cool operating fluids according to temperatures of the operating fluids at a running state or an initial starting condition of the vehicle by using exhaust gas of high temperature and coolant.
In addition, the heat exchanger 10 is adapted to improve heat-exchanging efficiency between the operating fluids by promoting flow change and formation of turbulence in the exhaust gas and the coolant flowing in the heat exchanger.
For these purposes, the heat exchanger 10 according to various embodiments of the present invention, as shown in FIG. 1 and FIG. 2, includes an exhaust gas pipe 12, a case 20, first and second headers 30 and 40, first and second connecting members 50 and 60, an oil flowing section 70 and a heat radiating unit 80.
A plurality of bypass holes 14 is formed at an exterior circumference of an end portion of the exhaust gas pipe 12, and a valve 16 is mounted at the other end portion of the exhaust gas pipe 12. Therefore, the exhaust gas is exhausted from the exhaust gas pipe 12 through the bypass hole 14 or passes the exhaust gas pipe 12 according to opening/closing operations of the valve 16.
The exhaust gas exhausted from the engine flows into the end portion of the exhaust gas pipe 12 at which the bypass hole 14 is formed.
According to various embodiments, the case 20 is disposed at a radial outer of the exhaust gas pipe 12 so as to form a flowing space 22 between the case 20 and the exhaust gas pipe 12.
The case 20 has a cylindrical shape, and a coolant exhaust port 26, and a coolant inflow port 24 are formed at a side and the other side of the case 20 respectively. Therefore, the coolant flows into the flowing space 22 through the coolant inflow port 24 and is exhausted from the flowing space 22 through the coolant exhaust port 26.
In addition, the first and second headers 30 and 40 are mounted at both end portions of the case 20 so as to divide the flowing space 22, and prevent the coolant flowing into the flowing space 22 from flowing into the exhaust pipe 12.
In addition, the first and second headers 30 and 40 are adapted to fix the case 20 to the exhaust pipe 12.
According to various embodiments, the first connecting member 50 connects an end of the case 20 to an end portion of the exhaust gas pipe 12. The exhaust gas flows into a space formed by the first connecting member 50 through the bypass hole 14.
An end of the second connecting member 60 is connected to the other end of the case 12, and the other end of the second connecting member 60 is connected to an exhaust pipe or a muffler. The exhaust gas flowing into a space formed by the second connecting member 60 is exhausted through the other end of the second connecting member 60.
According to various embodiments, the oil flowing section 70 is formed between the exhaust pipe 12 and the case 20, and includes an inner pipe 72 and an outer pipe 74. An oil line 75 is formed between the inner pipe 72 and the outer pipe 74.
The outer pipe 74 of the oil flowing section 70 is connected to an oil inflow port 76 and an oil exhaust port 78 so as to receive transmission oil through the oil inflow port 76 and to exhaust the transmission oil through the oil exhaust port 78.
Herein, the oil exhaust port 78 and the oil inflow port 76 are formed at a side and the other side of the case 20 corresponding to the coolant exhaust port 26 and the coolant inflow port 24.
That is, the coolant inflow port 24 is formed close to the second header 40 and the coolant exhaust port 26 is formed close to the first header 30. In addition, the coolant exhaust port 26 is formed in a radial opposite direction of the coolant inflow port 24.
In addition, the oil inflow port 76 is formed close to the second header 40 and is connected to the oil line 75 from a radial opposite direction of the coolant inflow port 24. The oil exhaust port 78 is formed close to the first header 30 and is connected to the oil line 75 from a radial opposite direction of the coolant exhaust port 26.
According to various embodiments, the heat radiating units 80, as shown in FIG. 2 and FIG. 3, are disposed between the exhaust pipe 12 and the oil flowing section 70, and between the case 20 and the oil flowing section 70.
The heat radiating unit 80 includes a plurality of coupling pipes 88 formed by assembling plates 82 at which at least one protruding portion 84 is formed along a length direction. A connecting line 86 for flowing the exhaust gas flowing into the space formed by the first connecting member 50 to the space formed by the second connecting member 60 is formed in the coupling pipe 88.
In addition, a plurality of heat radiating units 80 is disposed in parallel with each other and connects the first header 30 with the second header 40. The exhaust gas passing through the heat radiating unit 80 exchanges heat with the coolant passing through the flowing space 22 and the transmission oil passing through the oil line 75. Therefore, temperatures of the coolant and the transmission oil are controlled.
Herein, one end of the heat radiating unit 80 is mounted in a first mounting hole 32 formed at the first header 30 and the other end of the heat radiating unit 80 is mounted in a second mounting hole 42 formed at the second header 40.
That is, both end portions of the heat radiating unit 80 are inserted in the first and second mounting holes 32 and 42 such that the heat radiating unit 80 fluidly connects the first header 30 with the second header 40. If the valve 16 mounted at the exhaust pipe 12 is closed, the exhaust gas flowing into the first connecting member 50 through the bypass hole 14 flows to the space formed by the second connecting member 60 through the heat radiating unit 80. After that, the exhaust gas is exhausted to the exhaust pipe or the muffler.
Flowing direction of the exhaust gas passing through the connecting line 86 of the coupling pipe 88 is opposite to that of the transmission oil passing through the oil line 75 and that of the coolant passing through the flowing space 22 of the case 20.
Therefore, the exhaust gas exchanges heat with the coolant and the transmission oil while flowing to opposite direction of the coolant and the transmission oil. Therefore, heat-exchange occurs more efficiently.
According to various embodiments, the heat radiating unit 80 encloses an exterior circumference of the exhaust pipe 12 between the exterior circumference of the exhaust pipe 12 and the inner pipe 72 of the oil flowing section 70.
In addition, the heat radiating units 80 are disposed apart from each other between the outer pipe 74 of the oil flowing section 70 and the case 20. According to various embodiments, it is exemplified that three heat radiating units 80 are disposed apart from each other between the outer pipe 74 and the case 20.
An exterior circumference and an interior circumference of the protruding portion 84, as shown in FIG. 4 and FIG. 5, are formed with semi-circular shape according to various embodiments. The plurality of protruding portions 84 is disposed as spiral shape along a length direction of the plate 82.
Herein, the protruding portion 84 is not formed at both end portions of the heat radiating unit 80. Since the both end portions of the heat radiating unit 80 are inserted in the first and second mounting holes 32 and 34 formed at the first and second headers 30 and 40 respectively, straight line sections are formed at the both end portions of the heat radiating unit 80 so as to seal between the both end portions of the heat radiating unit 80 and the first and second mounting holes 32 and 34.
The protruding portion 84 can be integrally and/or monolithically formed at the plate 82 by pressing.
According to various embodiments, the coupling pipe 88 is a circular pipe formed by the plurality of protruding portions 84, and an interior circumference and an exterior circumference of the coupling pipe 88 are formed as spiral shape.
When the exhaust gas flows in the connecting line 86, the coupling pipe 88 causes the exhaust gas to rotate so as to generate vortex.
In addition, the coolant and the transmission oil passing the outside of the coupling pipe 88 is caused to form turbulence such that heat-exchanging efficiency between the exhaust gas, the coolant and the transmission oil may be improved.
A pair of plates 82 is coupled to form a pipe shape in a state that the protruding portions 84 of the pair of plates 82 are disposed so as to be protruded toward the outside. Thereby, the coupling pipe 88 is formed.
That is, in a state that the pair of plates 82 is disposed such that inner surfaces of the protruding portions 84 formed at the pair of plates 82 face each other, the pair of plates 82 is coupled to each other so as to form the coupling pipe 88 having the connecting line 86 therein.
Herein, the pair of plates 82 may be coupled by welding.
The number of the coupling pipes 88 included in the heat radiating unit 80 can be controlled according to sizes of the first and second headers 30 and 40 and a diameter of the exhaust pipe 12. In addition, the coupling pipes 88 consisting of one heat radiating unit 80 are releasably assembled.
The heat radiating unit 80 including eight coupling pipes 88 is disposed between the case 20 and the oil flowing section 70 and the heat radiating unit 80 including twenty five coupling pipes 88 is disposed between the exhaust pipe 12 and the oil flowing section 70 according to various embodiments, but is not limited. That is, the number of the coupling pipes 88 may be controlled according to the diameter of the exhaust pipe 12 and the sizes of the first and second headers 30 and 40. In addition, the desirable number of the coupling pipes 88 may be disassembled from the heat radiating unit 80 including a plurality of coupling pipes 88 according to the number of the coupling pipes 88.
According to various embodiments, the heat radiating unit 80 of plate shape is curved to arc shape corresponding to the exhaust pipe 12 and the case 20 having cylindrical shape.
It is exemplified that the heat radiating unit 80 has an arc shape, but is not limited to this. A shape of the heat radiating unit 80 can be changed according to shapes of the exhaust pipe 12 and the case 20.
Meanwhile, at least one flowing hole 89 may be formed between the coupling pipes 88 in the plate 82 according to various embodiments. The flowing hole 89 is formed along a length direction of the plate 82.
After the protruding portion 84 is formed at the plate 82 by pressing, the flowing hole 89 may be formed by punching.
Herein, the flowing hole 89 enables the coolant passing the outside of the heat radiating unit 80 to flow upwardly or downwardly with respect to the heat radiating unit 80. Therefore, flow of the coolant at an exterior circumference of the coupling pipe 88 can be uniformalized. Therefore, heat-exchanging efficiency between the coolant and the exhaust gas can be further enhanced.
According to various embodiments, two plates 82 are assembled with each other so as to form the heat radiating unit 80. However, this is not limited. A plurality of rows of protruding portions 84 is formed at one plate 82, and the one plate 82 is folded to form the heat radiating unit 80 such that one row of protruding portions 84 is connected to another row of protruding portions 84 so as to form the coupling pipe 88 having the connecting line 86.
Hereinafter, operation and function of the heat exchanger 10 according to various embodiments of the present invention will be described in detail.
FIG. 6 is a cross-sectional view for showing operation of a heat exchanger according to various embodiments of the present invention.
When initial starting of the vehicle, the valve 16 closes the exhaust pipe 12 and the exhaust gas supplied from the engine to the exhaust pipe 12 flows to the space formed by the first connecting member 50 through the bypass hole 14 as shown in (S1) of FIG. 6.
The exhaust gas flowing into the space formed by the first connecting member 50 moves through the connecting line 86 of the coupling pipe 88. At this time, since the protruding portions 84 of the coupling pipe 88 are formed as spiral shape, the exhaust gas flowing in the connecting line 86 is rotated to generate the vortex.
Herein, the coolant passes the outside of the coupling pipe 88 and the turbulence is formed at the coolant by spiral shape of the protruding portions 84.
In addition, the coolant is distributed evenly above and below of the heat radiating unit 80 by the flowing hole 89. Therefore, the coolant exchanges heat with the exhaust gas efficiently. Therefore, the coolant can be warmed up quickly.
In addition, the transmission oil passing through the oil line 75 of the oil flowing section 70 is heated quickly by the exhaust gas passing through the heat radiating units 80 disposed at radial inner and outer of the oil flowing section 70. Therefore, the transmission oil can be warmed up quickly.
On the contrary, if the coolant and the transmission oil are warmed up completely, the valve 16 opens the exhaust pipe fully and the exhaust gas is prevented from flowing into the heat radiating unit 80 and is exhausted through the exhaust pipe 12, as shown in (S2) of FIG. 6. Therefore, temperature rise of the coolant and the transmission oil is prevented.
At this time, the coolant cools the transmission oil by heat-exchange with the transmission oil so as to prevent the temperature of the transmission oil from rising excessively.
The heat exchanger 10 according to various embodiments of the present invention is adapted to control the temperatures of the coolant and the transmission oil efficiently at a running state or an initial starting condition of the vehicle as a consequence that the exhaust gas exchanges heat with the coolant and the transmission oil.
Therefore, the heat exchanger 10 according to various embodiments of the present invention is adapted to warm up and cool operating fluids according to temperatures of the operating fluids at the running state or the initial starting condition of the vehicle by using exhaust gas of high temperature and coolant.
In addition, the heat exchanger 10 is adapted to improve heat-exchanging efficiency between the operating fluids by promoting flow change and formation of turbulence in the exhaust gas flowing in the heat radiating unit and the coolant flowing the outside of the heat radiating unit.
Since the temperatures of the operating fluids can be controlled according to the conditions of the vehicle, fuel economy and heating performance of the vehicle may be improved. In addition, since structures of the heat exchanger are simplified, assembling processes may be simplified.
In addition, at least one plate 82 forming with the protruding portions 84 of spiral shape is assembled to form the coupling pipe 88 of spiral shape having the connecting line 86. Therefore, manufacturing cost may be reduced and weight of the heat exchanger 10 may be lowered.
For convenience in explanation and accurate definition in the appended claims, the terms upper or lower, front or rear, inside or outside, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.

Claims

1. The heat exchanger of claim 15, wherein the protruding portion is integrally formed at the plate by pressing.

2. The heat exchanger of claim 15, wherein the protruding portion is provided with an exterior circumference and an interior circumference formed with semi-circular shape and is disposed as spiral shape along a length direction of the plate.

3. The heat exchanger of claim 2, wherein both ends of the heat radiating unit are inserted respectively in the first header and the second header, and the protruding portion is not formed at the both ends of the heat radiating unit.

4. The heat exchanger of claim 15, wherein the coupling pipe is a circular pipe formed by a plurality of protruding portions, and an interior circumference and an exterior circumference of the coupling pipe are formed as spiral shape such that vortex is generated at the exhaust gas flowing in the connecting line by rotation of the exhaust gas and the coolant passing the outside of the connecting line is caused to form turbulence.

5. The heat exchanger of claim 15, wherein the coupling pipe, in a state that protruding portions of a pair of plates are disposed so as to be protruded toward the outside, is formed by coupling the pair of plates.

6. The heat exchanger of claim 15, wherein the number of the coupling pipes included in the heat radiating unit is changed according to a diameter of the exhaust pipe and sizes of the first header and the second header.

7. The heat exchanger of claim 6, wherein the coupling pipes of one heat radiating unit are releasably assembled with each other.

8. The heat exchanger of claim 15, wherein a plurality of rows of protruding portions is formed at one plate, and the one plate is folded to form the heat radiating unit such that one row of protruding portions is connected to another row of protruding portions so as to form the coupling pipe.

9. The heat exchanger of claim 15, wherein the heat radiating unit encloses an exterior circumference of the exhaust pipe between the exterior circumference of the exhaust pipe and the inner pipe of the oil flowing section.

10. The heat exchanger of claim 15, wherein the heat radiating units are disposed apart from each other between the outer pipe of the oil flowing section and the case.

11. The heat exchanger of claim 15, wherein the plate is provided with at least one flowing hole formed between the coupling pipes.

12. The heat exchanger of claim 15, wherein a plurality of first and second mounting holes is formed at the first and second headers, and the both ends of the heat radiating unit are inserted in the first and second mounting holes, respectively.

13. The heat exchanger of claim 15, wherein the oil exhaust port and the oil inflow port are formed at a side and the other sided of the case corresponding to the coolant exhaust port and the coolant inflow port, respectively.

14. The heat exchanger of claim 15, wherein a flowing direction of the exhaust gas passing through the connecting line is opposite to that of the transmission oil passing through the oil line and that of the coolant passing through the flowing space of the case.

15. A heat exchanger comprising:

an exhaust gas pipe having a plurality of circumferential bypass holes formed at one end and a valve mounted at another end, wherein an exhaust gas selectively flows into the bypass holes when the valve is closed;

a outer radial case forming an annular flowing space between the case and the exhaust gas pipe, the case having a coolant exhaust port formed on one side thereof and a coolant inflow port formed on another side thereof;

first and second headers mounted respectively at opposing ends of the case and dividing the flowing space;

a first connecting member interconnecting one end of the case to the one end of the exhaust gas pipe to receive exhaust gas through the bypass holes;

a second connecting member having one end connected to another end of the case;

an oil flowing section formed between the exhaust gas pipe and the case, and including

an inner pipe, an outer pipe and an oil line formed between the inner pipe and the outer pipe, the oil line being fluidly connected to an oil inflow port and an oil exhaust port; and

at least one heat radiating unit disposed between the exhaust pipe and the oil flowing section, and at least another heat radiating unit disposed between the case and the oil flowing section, each provided with at least one coupling pipe formed by coupling at least one plate at which at least one protruding portion is formed along a length direction, and adapted to connect the first header with the second header;

wherein a connecting line is formed in the coupling pipe so as for the exhaust gas flowing into the first connecting member to flow therein, and the exhaust gas flowing in the connecting line exchanges heat with coolant and transmission oil passing an outside of the coupling pipe.