JP2008096048A - Inner fin of heat exchanger for exhaust gas - Google Patents

Abstract

An object of the present invention is to provide an inner fin of an exhaust gas heat exchanger that has little soot accumulation, little increase in gas resistance and low cooling performance, and can withstand high-temperature exhaust gas.
SOLUTION: Built in a flat tube incorporated in an exhaust gas heat exchanger, the wide direction of the exhaust gas flow path formed by the flat tube is divided into small sections to form a large number of elongated exhaust gas flow paths. In the inner fin, the thin plate material forming the inner fin is formed in a meandering shape in which the respective refractive tops are alternately brought into contact with the opposing inner wall surfaces of the flat tube, so that the thin plate material between the refractive tops is partitioned. A first corrugate shape in which a wall is formed and an elongated exhaust gas flow path is formed between each of the partition walls, and each of the partition walls has a wall surface projecting laterally with respect to the flow direction of the exhaust gas And a second corrugated shape forming a wall surface of the bellows structure in which the recessed wall surface is alternately repeated.
[Selection] Figure 2

Description

  The present invention relates to an inner fin of an exhaust gas heat exchanger that improves the heat exchange efficiency by improving the shape of an inner fin incorporated in a flat tube of a square heat exchanger and facilitates manufacture.

In recent years, in order to respond to exhaust gas regulations of diesel engines, the EGR rate tends to increase. As the EGR gas flow rate increases, the gas temperature has increased. Furthermore, in order to lower the combustion temperature and reduce NOx, it is required to reduce the gas outlet temperature of the EGR cooler and to greatly increase the heat radiation amount.
In order to meet this requirement, as shown in FIG. 7, the inner fin 4 is provided in the flat tube 3 built in the shell 2 of the square heat exchanger 1 having a rectangular cross section with respect to the flow of the EGR gas. Provided at both ends of the shell 2 thus formed are an inlet pipe 5a and an outlet pipe 5b serving as cooling water inlets and outlets on the wall surface and connected to a hot gas pipe (not shown) serving as an EGR gas passage. The headers 7 and 7 are formed as intermediate flow paths that change the cross-sectional area from the cross-section of the hot gas pipe to the cross-section of the shell 2.
The inner fin 4 is built in the flat tube 3 for the purpose of expanding the heat transfer area on the gas side, and each plate material of the flat tube 3 formed by inserting the inner fin 4 into the flat tube 3 or forming two shells. Between the plate surface of the flat tube 3 and each top portion of the inner fin 4 by high temperature brazing.

  As shown in FIG. 8, for example, as shown in FIG. 8, the exhaust gas heat exchanger incorporating a flat tube with an inner fin has a rectangular cross-sectional shape, and the flow path is formed as the flow path shape advances in the longitudinal direction of the flow path. Some have wave fins 8 formed so as to wave or meander (Patent Document 1). In this wave fin 8, each ridge line of the wave is bent into a plane waveform, and at the position of the plane top portion and the plane valley portion of the plane waveform, there is a protruding shape protruding from each plate forming the flat tube. A wave fin without a turbulent flow forming part, which has a turbulent flow forming part, tends to adhere soot in the exhaust gas that tends to stay in the flat top part and the flat valley part. The turbulent flow that is generated prevents the adhesion of soot.

JP 2004-263616 A

[Problems of the prior art]
Since the inner fin 4 of the exhaust gas heat exchanger in such a conventional technique is exposed to high-temperature exhaust gas, it is necessary to ensure durability at a high temperature. Since the passage cross-sectional area is reduced, there are problems such as a decrease in performance of the EGR cooler due to deposition of soot and a large increase in gas resistance even if the initial performance is good.

  The present invention has been made in view of the above problems in the prior art, and the technical problem specifically set in order to solve this problem is that there is little accumulation of soot, an increase in gas resistance, and cooling performance. It is an object of the present invention to provide an inner fin for an exhaust gas heat exchanger that can withstand a high temperature exhaust gas.

In order to identify the inner fin of the exhaust gas heat exchanger that effectively solves the above-mentioned problems in the present invention, all the matters recognized as necessary are covered and specifically configured as the problem solving means described below. Show.
The first problem solving means relating to the inner fin of the exhaust gas heat exchanger is built in a flat tube incorporated in the exhaust gas heat exchanger, and the wide direction of the exhaust gas flow path formed by the flat tube is divided into small sections. In the inner fin forming a plurality of elongated exhaust gas flow paths, the thin plate material forming the inner fin is in a meandering shape in which each refracting apex alternately abuts both inner wall surfaces facing the flat tube. Forming a partition wall with a thin plate material between the refractive tops, and a first corrugated shape in which an elongated exhaust gas flow path is formed between each of the partition walls, and the partition walls And a second corrugated shape forming a wall surface of an accordion structure in which a wall surface protruding in a direction transverse to the flow direction of exhaust gas and a recessed wall surface are alternately repeated. It is intended to.

  In the second problem solving means relating to the inner fin of the exhaust gas heat exchanger, the second corrugated shape is formed into a triangular waveform in which the planar sectional shape of each partition wall is continuous in the flow direction of the exhaust gas. And the outline of the front shape of the part which forms the triangular waveform of each said partition wall was formed in the parallelogram, It is characterized by the above-mentioned.

  The third problem-solving means relating to the inner fin of the exhaust gas heat exchanger is such that the front shape of the edge of the partition wall at the inlet of the exhaust gas flow path bends in opposite directions at both ends serving as the refracted peaks. A straight line that is formed by a curve and a tangent to each bent part and overlaps the short side of the parallelogram, and the straight line is bent at an obtuse angle to the opposite side at a position that overlaps the central part of both short sides. It consists of a straight line formed in parallel with the long side of the parallelogram, and when half-turned around the midpoint, the half-shapes on one side overlap the other half-shapes are formed into the same shape. It is characterized by.

The fourth problem solving means relating to the inner fin of the exhaust gas heat exchanger is that the front face profile of the portion forming the triangular waveform has an angle φ between the long and short sides of the parallelogram and the inner wall of the flat tube, η
40 ° ≦ φ ≦ 50 °
80 ° ≦ η ≦ 85 °
It is characterized by being in the range of

The fifth problem solving means relating to the inner fin of the exhaust gas heat exchanger is characterized in that an angle θ formed by the triangular waveform and a straight line connecting the inlet and outlet is
15 ° ≦ θ ≦ 20 °
And the bend radius r at the tip of the corrugation is set to a range of 0.5 mm or less.

  A sixth problem solving means relating to the inner fin of the exhaust gas heat exchanger is characterized in that the material of the inner fin is ferritic stainless steel.

  In the first problem-solving means relating to the inner fin of the exhaust gas heat exchanger, the partition wall formed by the inner fin divides the wide direction of the exhaust gas passage formed by the flat tube into small sections, and A first corrugated shape that is subdivided into an elongated exhaust gas flow path and a second corrugated shape that forms a wall surface of a bellows structure that repeatedly protrudes or dents in the partition wall with respect to the flow of exhaust gas are formed. As a result, the flat tube can be subdivided to enhance the cooling effect, and turbulent flow in the direction of the exhaust gas flow can be easily generated to prevent the adhesion of substances that cause the wall cooling effect and the heat exchange efficiency such as soot to decrease. It is easy and easy to peel off, and the cooling effect of the exhaust gas can be enhanced.

  In the second problem solving means relating to the inner fin of the heat exchanger for exhaust gas, the plane cross-sectional shape of the second corrugated shape is a triangular waveform, and the contour of the front shape at the triangular waveform forming portion is formed as a parallelogram. As a result, the bending angle between the flat surfaces can be made obtuse, making it possible to mold even hard metal materials with low elongation, such as ferritic materials, and achieve a corrugated shape with a desirable shape, excellent heat resistance and increased cooling efficiency. The vortex generated by the separation of the exhaust gas flow at the protruding end of the triangular wave prevents the soot from adhering to the wall surface of the partition wall and removes the soot accumulated on the surface of the partition wall by peeling it off. be able to.

  In the third problem-solving means relating to the inner fin of the exhaust gas heat exchanger, the cross-sectional shape of the partition wall at the neutral position of the inlet / outlet of the exhaust gas passage and the triangular waveform is half-rotation about the midpoint of the partition wall The half-shape of the cross-sectional shape becomes the same shape as the other half-shapes, making it easy to press-mold, and easier to die after pressing, improving work efficiency during production and reducing production costs. Can contribute.

  In the fourth problem solving means relating to the inner fin of the exhaust gas heat exchanger, the formability of the angle formed by the parallelogram forming portion formed by the contour in the front shape of the partition wall and the inner wall of the flat tube can be improved. By setting the angle range, even a material with little elongation such as ferritic stainless steel can be molded well.

  In the fifth problem-solving means relating to the inner fin of the exhaust gas heat exchanger, a material having less elongation such as ferritic stainless steel is obtained by limiting the bending angle of the triangular waveform and suppressing the elongation of the material used. However, good moldability can be secured, and by reducing the bending radius r at the tip of the corrugation, separation of the exhaust gas flow at the apex is promoted, and improvement in performance and clogging resistance due to increased shear force Can be improved.

  Further, in the sixth problem solving means relating to the inner fin of the exhaust gas heat exchanger, the inner fin is formed of ferritic stainless steel, so that the heat resistance is improved and a cooling fin that can withstand high-temperature exhaust gas is provided. Can be formed.

Hereinafter, the best embodiment according to the present invention will be described in detail.
However, this embodiment is specifically described for better understanding of the gist of the invention, and does not limit the content of the invention unless otherwise specified.

〔Constitution〕
The flat tube of the exhaust gas heat exchanger according to the embodiment has a plate material at each end on the half-opening side of both half-cylinders, as shown in the cross section shown in FIG. Are connected to each other to form a flat hollow tube having a space between parallel walls.
Inside the flat tube 3, an inner fin 14 having a meandering wall surface that divides the inside into a large number of small flow paths 3a, 3b, ..., 3b, 3c is inserted.
One end of the inner fin 14 that reaches from the inner surface of one of the flat tubes to the other inner surface by brazing each of the bent end portions 14a of the inner fin 14 with the meandering wall shape of the meandering wall in contact with the inner surface of the flat tube. Partition walls 15,..., 15 made up of parts are formed.
The partition walls 15, ..., 15 partition the inside of the flat tube 3 into small flow paths 3a, 3b, ..., 3b, 3c, and the small flow paths 3a, 3b, ..., 3b, 3c partitioned by the wall surface. A wall surface of a special bellows structure having a zigzag triangular corrugated cross-sectional shape for generating turbulent flow in the exhaust gas flowing inside is formed.

  The main body 3d of the flat tube 3 is formed so that it can be used as a flat tube by crushing a cylinder, or a long edge is formed by dividing the tube into two bowl-shaped parts that are shallow in the thickness direction and long in the axial direction. In addition, it is formed as a flat tube so that it can be used by combining half-parts. It is desirable to use an iron-based alloy sheet as the material used, and among these, a ferritic stainless steel sheet is preferably used.

  As shown in FIG. 2, the overall shape of the inner fin 14 is a first corrugated shape 16 that meanders so as to subdivide the longitudinal direction of the elongated flow passage in the cross section of the flat tube 3 by pressing a thin plate material. And a wall surface protruding in a direction intersecting with the flow direction of the exhaust gas and a wall surface recessed in the partition wall 15,..., 15 formed by the first corrugated shape 16. A wall surface is formed, and the second corrugated shape 17 is formed so that the cross-sectional shape is corrugated, thereby forming heat transfer fins having two types of corrugated shapes.

  As shown in FIGS. 1 to 3, the first corrugated shape 16 is brazed in such a way that the respective refracting vertices (hereinafter simply referred to as vertices) of the inner fin 14 abut against the opposing inner wall surfaces of the flat tube 3. A flow path shape having a contact area as much as possible and subdivided by the front shape of the partition wall edge and the front shape of the adjacent partition wall 15 that is symmetrical with respect to the vertical plane passing through the apex of the partition wall 15 Are formed, and the direction of the connected partition walls 15 is alternately changed to form a shape that is installed in the entire flat tube 3.

Further, as shown in FIGS. 3 to 5, the second corrugated shape 17 protrudes or dents in the side surface of the partition wall 15 formed by the first corrugated shape 16 in the direction of approaching and separating from the adjacent partition wall 15. By forming, the cross-sectional shape is formed so as to form a corrugated shape.
It is desirable that the corrugation formed on the side surface has a triangular cross-sectional shape, and this wave shape is more likely to cause separation of the exhaust gas flow at the tip portion when the bent portion (or tip portion) is sharpened. preferable.

  As shown in FIG. 3, the second corrugated shape 17 has a contoured front shape in which a corrugated forming portion is generated when the flow direction of EGR gas is viewed from the front (inlet side) to the rear (outlet side). Is a short side (top inclined surface 14b) formed tangent to the curved portion 15r (tip bent portion 14a) formed on each top portion brazed to the inner surface of the flat tube 3, and each of the short sides A parallelogram formed of a long side (center inclined surface 14c) formed by bending at an obtuse angle α toward the short side opposite to each other (opposite side) at a position equidistant from the contact point is formed. 4 and 5, the plane cross-sectional shape forms a wall that blocks the flow direction of the exhaust gas and forms a continuous triangular waveform that is alternately bent to the opposite side at the same angle (obtuse angle) β. A bellows structure that forms a surface is formed.

At the inlet and outlet portions before and after this folding screen-like surface is formed, the flow passage is formed straight in the axial direction with the same flow passage area and depth, and the inlet side end portion 14d serving as the exhaust gas introduction portion and the exhaust gas The flow direction of the exhaust gas directly connected to the inlet side end portion 14d and the outlet side end portion 14e between each of the outlet side end portions 14e serving as gas discharge guide portions and the portion where the folding screen-like surface is formed The first and last bent surfaces 14f and 14g are formed in a bent shape that alternately bends at an obtuse angle β in the opposite direction at half the depth of the bent surfaces 14h,. .
The first and last bent surfaces 14f and 14g are bent at a bending angle γ = 180−θ at a position where they are directly connected to the inlet side end portion 14d and the outlet side end portion 14e.

Among the shapes of the inner fins 14, the bending radius R for bending is set to be as small as possible in a range where the brazing range is not excessively narrowed and the strength is not lowered at each tip bending portion 14 a. To do.
Further, the bending radius r of the bent tip portions of the bent surfaces 14h,..., 14h forming the folding screen-like surface sharpens the tip portion and effectively causes the exhaust gas flow to be separated from the wall surface. To make it easier, make it as small as possible.

In the inner fin 14, it is desirable to use ferritic stainless steel as a material of the inner fin of the exhaust gas heat exchanger, and among these, SUS405 and SUS446 are particularly preferably used.
Moreover, the brazing is preferably Ni brazing which has a high processing temperature and excellent heat resistance.

Of the shape of the inner fin 14, the long side (center inclined surface) 14 c and the short side (top inclined surface) 14 b when the frontal shape of the triangular waveform portion is a parallelogram, and the wall surface of the flat tube 3 are formed. The angles φ and η
40 ° ≦ φ ≦ 50 °
80 ° ≦ η ≦ 85 °
In the range.

In addition, an angle (hereinafter referred to as a wave angle) formed by triangular waveforms (bending surfaces) 14f, 14g, and 14h and planes (entrance / exit side ends) 14d and 14e formed at any of the end portions on the entrance / exit side. θ
15 ° ≦ θ ≦ 20 °
In the range.

At the position where the first and last bent surfaces 14f, 14g are directly connected to the inlet side end 14d and the outlet side end 14e, the bending angle γ is
160 ° ≦ γ = 180−θ ≦ 165 °
In the range.

Further, the radius of curvature R of each tip bending portion 14a is set to about R ≧ 0.5 mm so that the brazing range does not become too narrow and the brazing strength does not decrease.
Further, the bending radius r of the triangular waveform tip is set to r ≦ 0.5 mm, and the tip is formed as sharp as possible.

[Function and effect]
In the inner fin 14 of the exhaust gas heat exchanger in this embodiment, the front projected shape (contour) of the partition wall 15 is bent by the curvature radius R (≧ 0.5 mm) of the curved portion 15r. It consists of top inclined surfaces 14b and 14b which are tangential planes formed in contact with the curved surface, and central inclined surfaces 14c and 14c which are flat surfaces formed by bending from the top inclined surface 14b to the opposite side at an obtuse angle α. It becomes a parallelogram, the angle φ, η formed by the short side and long side of the parallelogram and the wall surface of the flat tube 3 is set within a specified range, the size of the bend is suppressed, and the bend angle θ of the triangular waveform Is set within a specified range, and the elongation in the fin width direction of the material is suppressed to 10% or less, so that a good formability can be obtained even with a material having a small elongation such as ferritic stainless steel.

Triangular corrugation bend radius r is defined as small as 0.5 mm or less to promote separation of exhaust gas flow at the corrugated tip, improving cooling performance and improving clogging resistance by increasing shear force. be able to.
As shown in FIG. 6, the flow separation is performed particularly when the bending angles r of the plate surfaces (bending surfaces) 14 h,..., 14 h formed at the center are obtuse angles β. Since (≦ 0.5 mm) is made small, in the vicinity of the wall surface of the partition wall 15, a concave surface (bent surface) on the back side from the surface 14 h that protrudes on the gas flow side of the wall surface that undulates unevenly. When the flow is changed to 14h, the gas flow is separated from the wall surface to generate a vortex on the back side, and the vortex collides with the next plate surface 14h on the front side, so that the soot is deposited on the plate surface. While hindering, the accumulated soot is peeled off and discharged to the outside, the wall surface of the inner fin 14 is kept in its original state, the adverse effect due to the adhesion of soot and the like is suppressed, and the heat exchange efficiency can be kept high.
By setting the bending radius R of the bent portion 14a to 0.5 mm or more, the inner fin 14 can be fixed to the inner surface of the flat tube 3 without lowering the strength of the brazing portion, and the brazing range. Can be limited to a very narrow range.

[Another aspect]
Such an embodiment is specifically described in order to facilitate understanding of the gist of the invention, but does not limit the content of the invention, and is not particularly described (including design content). The embodiment is not limited, and may be changed as appropriate. In this sense, some other embodiments that meet the spirit of the invention are shown below.

  For example, the ferritic stainless steel exemplified in SUS405, SUS446, etc. was used, but other than this, it is only necessary to be able to bend even if it is a high heat resistance and hard material. Or you may use stainless steels other than ferrite type, such as SUS422, SUS440, SUS316L, SUS321, and SUS347.

It is a cross-sectional view which shows the flat tube which incorporated the inner fin of the heat exchanger for exhaust gas by embodiment of this invention. It is a perspective view which shows the inner fin of the heat exchanger for exhaust gas same as the above. It is front sectional drawing which shows the front shape of the partition wall in the inner fin of a heat exchanger for exhaust gas same as the above. It is a side view which shows the side shape of the partition wall in the inner fin of a heat exchanger for exhaust gas same as the above. FIG. 5 is a plan sectional view showing a planar sectional shape of a partition wall in an inner fin of the exhaust gas heat exchanger, FIG. 5 (A) is a sectional plan view taken along the line AA in FIG. 3, and FIG. It is an expanded plane sectional view which expands and shows the B section of FIG. It is plane sectional explanatory drawing which shows the state of the flow of the exhaust gas along the partition wall in the inner fin of an exhaust gas heat exchanger same as the above. It is a perspective view which fractures | ruptures and shows the conventional square heat exchanger partially. It is a perspective view which shows an example of the wave fin used for the conventional heat exchanger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat exchanger 2 Shell 3 Flat tube 5a Inlet pipe 5b Outlet pipe 6 Flange 7 Header 14 Inner fin (thin plate material)
14a Bend at tip (refractive apex)
14b Top slope (short side)
14c Inclined surface at the center (long side)
14d Inlet side end (plane)
14e Exit end (plane)
14f (first) bent surface 14g (last) bent surface 14h (forms a folding screen-like) bent surface (plate surface)
15 Partition wall 15r Curved portion 16 First corrugated shape 17 Second corrugated shape α Bending angle on the obtuse angle side formed by the long side (center inclined surface) 14c and the short side (top inclined surface) 14b of the parallelogram β Triangular waveform bending angle γ The first bending surface 14f and the inlet side end 14d, the final bending surface 14g and the outlet side end 14e, respectively, the bending angle η The long side of the parallelogram ( Angle θ formed between the central inclined surface 14 c and the surface of the flat tube 3 Wave angle φ Angle formed between the short side (top inclined surface) 14 b of the parallelogram and the surface of the flat tube 3

Claims (6)

In an inner fin that is built in a flat tube incorporated in an exhaust gas heat exchanger and divides the wide direction of the exhaust gas flow path formed by the flat tube into small sections to form a large number of elongated exhaust gas flow paths ,
By forming the thin plate material forming the inner fin in a meandering shape in which the respective refractive tops alternately contact the opposing inner wall surfaces of the flat tube, a partition wall is formed by the thin plate material between the refractive tops, A first corrugated shape in which an elongated exhaust gas flow path is formed between each of the partition walls;
Each of the partition walls has a second corrugated shape that forms a wall surface of a bellows structure in which a wall surface protruding in a direction transverse to the flow direction of the exhaust gas and a recessed wall surface are alternately repeated. Inner fin of exhaust gas heat exchanger. The second corrugated shape is formed into a triangular wave shape in which the planar cross-sectional shape of each partition wall is continuous in the exhaust gas flow direction, and the contour of the front shape of the portion forming the triangular wave shape of each partition wall is The inner fin of the heat exchanger for exhaust gas according to claim 1, wherein the inner fin is formed in a parallelogram. The front shape of the edge of the partition wall at the inlet of the exhaust gas flow path is
Folding curves that bend in opposite directions at both ends that are the refraction top, a straight line that is formed by a tangent to each folding part and that overlaps the short side of the parallelogram, and this straight line is the center of both short sides Consisting of a straight line formed parallel to the long side of the parallelogram by bending at an obtuse angle to the opposite side at a position overlapping with
2. The inner part of an exhaust gas heat exchanger according to claim 1, wherein, when half-rotating about a midpoint, a half shape on one side overlaps with another half shape is formed in the same shape. fin. Angles φ and η between the long and short sides of the parallelogram and the inner wall of the flat tube are the contours of the front shape of the portion forming the triangular waveform,
40 ° ≦ φ ≦ 50 °
80 ° ≦ η ≦ 85 °
The inner fin of the heat exchanger for exhaust gas according to claim 2, characterized in that An angle θ between the triangular waveform and a straight line connecting the entrance and exit,
15 ° ≦ θ ≦ 20 °
The inner fin of the heat exchanger for exhaust gas according to claim 2, wherein the bending radius r of the waved bent end is set to a range of 0.5 mm or less.   The inner fin of the heat exchanger for exhaust gas according to any one of claims 1 to 5, wherein the material of the inner fin is ferritic stainless steel.

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