JP2015078819A - Inner fin - Google Patents

Abstract

Provided is an inner fin that can suppress clogging and improve heat radiation performance while suppressing pressure loss and has high productivity. An inner fin 1 is inserted into a heat exchange tube, and includes a plate member, a top plate 2, a bottom plate 3, and a side plate 4 that partitions the plate member substantially vertically at a predetermined pitch. The corrugated plate is formed, and a plurality of passages 5 through which gas passes along the front-rear direction are provided on both sides of each side plate 4, and the side plate 4 is bent to the left and right at predetermined intervals in the front-rear direction. A protrusion 7 is formed on the wall surface of the side plate 4 that extends from the inner vertex of the meandering refractive portion 6 to the outer vertex of the upstream refractive portion 6 and protrudes into the passage 5. did. [Selection] Figure 1

Description

  The present invention relates to an inner fin that is inserted into a heat exchanger and promotes heat exchange of exhaust gas or the like.

  In an EGR device that reduces the generation of nitrogen oxides by recirculating a part of exhaust gas and returning it to the intake system of the engine, the EGR cooler mounted on the vehicle to cool the exhaust gas includes an engine exhaust system and an intake system. Installed between the system.

A plate tube type EGR cooler inserts a number of flat plate tubes (hereinafter simply referred to as tubes) into a shell formed as a cylinder to exchange heat between the exhaust gas flowing inside the tube and the cooling water flowing outside the tube. I do.
This tube uses a hollow tube body formed by extrusion molding, or an inner fin inserted into a flat tube body made up of two vertically divided members, and the tube body and the inner fin are brazed.

An offset fin, which is a type of a conventional inner fin, is cut into a plate at a predetermined interval, the cross section becomes a rectangular wave shape, and a quarter wave period (pitch) at a predetermined interval in the front-rear direction is shifted left and right by one quarter. It was cut and raised so as to be displaced in the direction.
The offset fin has a function of improving the heat radiation performance by disturbing the flow of the exhaust gas in the tube and diffusing the exhaust gas.

When exhaust gas passes through the tube and exchanges heat with cooling water outside the tube, soot and PM (particulate matter) in the exhaust gas may accumulate on the inner fins in the tube and cause clogging. It was. When the clogging became significant, the claw covered the surface of the inner fin, and heat exchange between the exhaust gas and the cooling water was not performed well, and the heat dissipation performance was deteriorated.
Further, the soot may block the exhaust gas passage and damage the EGR cooler.

Wayby fins were used as inner fins that are less likely to clog the fins than offset fins.
As shown in FIGS. 7 and 8, the conventional wayby fin 10 is formed into a rectangular wave shape comprising a top plate 2, a bottom plate 3, and a side plate 4 partitioning them substantially vertically at a predetermined pitch. In addition, there is one in which the side plate 4 is bent left and right at predetermined intervals in the front-rear direction and extends in a meandering manner (Patent Document 1).
In the wayby fin 10, the exhaust gas is branched into a number of passages 5 partitioned by the side plates 4 and flows in the direction of the arrow G to exchange heat with the cooling water.

Since the waveby fin 10 has a shape with no cuts, the exhaust gas was allowed to pass smoothly, and soot accumulation was reduced.
In addition, the pressure loss of the wayby fin 10 was smaller than that of the offset fin that caused a pressure loss when the exhaust gas diffused inside.
However, as shown in FIG. 8, in the waby fin 10, the flow passage cross-sectional area C with respect to the flow direction of the exhaust gas in the meandering refracting portion 6 is larger than the upstream flow passage cross-sectional area A. The heat dissipation performance was lower than that of the offset fin.

Further, in the vicinity O of the apex portion outside the refraction part 6, soot is accumulated due to a recirculation region in which the flow rate of the exhaust gas is slow or stagnant, and the heat dissipation performance may be deteriorated.
If soot accumulates in the vicinity of the outer apex portion of the refraction part 6 where the exhaust gas flow velocity is slow, the left and right width of the meandering shape is reduced, making it difficult to generate turbulent exhaust gas and further promoting soot deposition. It was.

In order to improve the heat dissipation performance, the period (wave pitch) of the meandering wave of the waveby fin 10 is made fine, or the period (fin pitch) of the rectangular wave composed of the top plate 2, the bottom plate 3 and the side plate 4 is made fine. However, although some heat dissipation areas were increased, the pressure loss increased because the total length of the exhaust gas passages became longer and the proportion of fins in the exhaust gas flow passage cross-sectional area increased.
Further, if the fin pitch is made finer, the development length of the necessary material for the waveby fin 10 becomes longer, so that the weight and the material cost are increased.

JP 2008-096048 A

  In recent years, in order to respond to stricter exhaust gas regulations, EGR coolers and other heat exchangers mounted on vehicles have been required to have higher heat dissipation performance, lower gas resistance, and prevention of clogging.

  The present invention has been made to solve the above problems, and provides an inner fin that can prevent clogging and improve heat dissipation performance while suppressing pressure loss and has high productivity. Is an issue.

In the present invention, means for solving the above problems are as follows.
1st invention is an inner fin inserted in the tube for heat exchange, Comprising: A corrugated board which consists of a board | plate material, a top plate, a baseplate, and the side plate which partitions between these at a predetermined | prescribed pitch substantially perpendicularly A plurality of passages through which gas passes along the front-rear direction on both sides of each side plate, the side plate refracts to the left and right at predetermined intervals in the front-rear direction, and extends in a meandering manner, and A protrusion projecting into the passage is formed on the wall surface of the side plate that continues from the inner vertex of the meandering refractive portion to the outer vertex of the upstream refractive portion.

  The second invention is characterized in that the protrusion is formed in the vicinity of the apex portion inside the meandering refraction part.

  The third invention is characterized in that the protrusion protrudes perpendicularly to the gas flow.

According to 1st invention, the protrusion which protrudes in a channel | path is formed in the wall surface of the side plate which continues from the inner vertex part of the said serpentine-shaped refractive part to the outer vertex part of the upstream refractive part. Thus, it is possible to prevent soot and PM from accumulating by narrowing the passage and increasing the gas flow velocity in the vicinity of the apex.
Since soot can be prevented from accumulating in the vicinity of the apex portion of the meander, high heat dissipation performance can be maintained over a long period of time.
Further, by increasing the gas flow rate, heat exchange can be promoted, and the heat dissipation performance can be improved.

Furthermore, by providing a protrusion on a part of the side plate of the inner fin, it is possible to suppress an increase in the pressure loss of the exhaust gas when the fin pitch is made fine for improving the heat radiation performance as in the conventional case.
Further, since the protrusions can be provided by press-molding the side plate, it is possible to prevent an increase in the weight and material cost of the inner fin.

  According to the second invention, by forming the protrusion in the vicinity of the apex portion inside the meandering refraction part, the flow path immediately upstream of the refraction part is narrowed, and the flow rate of the exhaust gas flowing into the apex part is reduced. Since it rises and leads to the outer apex, it is possible to more effectively prevent soot and PM accumulation and improve the heat dissipation performance.

  According to the third invention, since the protrusion protrudes perpendicularly to the gas flow, the passage can be narrowed more effectively with a limited material and the exhaust gas flow rate can be increased. .

It is a perspective view which shows the inner fin which concerns on 1st embodiment of this invention. It is a plane explanatory view showing the inner fin. It is a fragmentary perspective view which shows the tube which inserts the same inner fin. It is a plane explanatory view for showing the position which provides a projection in the inner fin. (A) is a graph which shows the relationship between the position of the protrusion of the same inner fin, and heat dissipation performance, (b) is a graph which shows the relationship between the position of the protrusion of the inner fin, and pressure loss. (A) is a graph which shows the relationship between the protrusion length of the protrusion of the inner fin, and heat dissipation performance, (b) is a graph which shows the relationship between the protrusion length of the protrusion of the inner fin, and pressure loss. It is a perspective view which shows the conventional inner fin. It is plane explanatory drawing which shows the conventional inner fin.

Hereinafter, the inner fin 1 which concerns on embodiment of this invention is demonstrated.
The inner fin 1 is inserted into a flat plate tube (hereinafter simply referred to as a tube) through which exhaust gas passes in an EGR cooler mounted on a vehicle. As shown in FIG. 3, the tubes T have flat upper and lower surfaces and left and right side surfaces perpendicular to the upper and lower surfaces, respectively.
A large number of tubes T are stacked inside the EGR cooler at a predetermined interval, and heat is exhausted from the exhaust gas passing through the tubes T to a refrigerant (such as cooling water) flowing outside the tubes T.

As shown in FIG. 1, the inner fin 1 is formed by processing a single SUS (stainless steel) plate material by press molding, and alternately arranging horizontal top plates 2 and bottom plates 3 in the left-right direction. A transverse section formed by partitioning the gaps by a substantially vertical side plate 4 is formed into a rectangular corrugated corrugated plate.
When the inner fin 1 is inserted into the tube T and the top plate 2 and the bottom plate 3 are brazed to the inner surface of the tube T, a number of exhaust gas passages 5 partitioned by the side plate 4 are formed.
In order to increase the heat exchange area and improve the heat dissipation performance, the side plate 4 and the passage 5 are extended in a meandering manner that refracts to the left and right at predetermined intervals in the front-rear direction.

As shown in FIGS. 1 and 2, in the passage 5, a protrusion 7 is formed so as to protrude into the passage 5 from the side plate 4 in the vicinity of the apex portion inside each meandering refractive portion 6.
The protrusions 7 are preferably provided so as to protrude from the side plate 4 forming the inner apex portion of the refraction part 6 toward the opposing outer side plate 4 at an angle perpendicular to the flow of exhaust gas at that position. .

The protrusion 7 is formed for each refractive part 6.
In one passage 5, the inner side plate 4 and the outer side plate 4 are reversed in a certain refractive portion 6 and the nearest downstream refractive portion 6, so that the protrusions 7 are alternately formed on the left and right side plates 4. .

  The protrusion 7 is provided by plastically deforming the side plate 4 at the same time that the rectangular wave-shaped inner fin 1 is press-formed from a SUS plate.

As shown in FIG. 2, in the inner fin 1 of the first embodiment, by providing the protrusion 7, the width of the passage B immediately upstream of the refraction part 6 is relatively narrower than the other part A. .
Therefore, when the exhaust gas is caused to flow in the direction of arrow G in the tube in which the inner fin 1 is inserted, the exhaust gas is guided to the outer apex portion while the flow velocity increases immediately upstream from the apex portion of the refraction part 6, It is possible to make it difficult to deposit soot and PM by increasing the flow rate of the exhaust gas near the outer apex O.

Thereby, accumulation of soot and PM in the refraction part 6 can be prevented, and high heat dissipation performance can be maintained for a long time.
Further, by increasing the flow rate of the exhaust gas, heat exchange with the cooling water can be promoted, and the heat dissipation performance can be improved.

Furthermore, the provision of the projections 7 can reduce the pressure loss of the exhaust gas as compared with the conventional case where the meandering fin pitch is made fine for improving the heat radiation performance.
Moreover, since the protrusion 7 can be provided by press-molding the side plate 4, an increase in the weight and material cost of the inner fin 1 due to the provision of the protrusion 7 can be prevented.

  Further, since the projection 7 projects perpendicularly to the flow of the exhaust gas, the passage can be effectively narrowed and the flow rate of the exhaust gas can be increased.

In FIG. 4, the protrusion 7 can be formed within the range of the wall surface W of the side plate 4 that continues from the inner apex portion of the predetermined refractive portion 6 ′ to the outer apex portion upstream thereof.
Among the wall surfaces W, it is preferable to form the protrusions 7 in the region L downstream of the region U on the extension line of the flow flowing into the refractive portion 6 ″ that is one upstream of the predetermined refractive portion 6 ′.
Since the flow path is relatively wide in the region U, the effect of increasing the flow velocity is reduced even if the protrusions 7 are provided. Further, since the region U is far from the predetermined refraction part 6 ′, it is difficult to maintain the increased flow velocity up to the vertex O outside the refraction part 6 ′. Further, when the protrusion 7 is provided in the region U, a recirculation region is generated between the protrusion 7 and the one upstream refractive portion 6 ″, and the pressure loss of the exhaust gas increases.
On the other hand, when the protrusion 7 is provided in the region L, the flow rate of the exhaust gas passing through the apex portion O outside the refraction part 6 ′ can be increased to prevent soot accumulation, and the exhaust gas is greatly meandered from side to side. By doing so, heat exchange can be promoted and heat dissipation performance can be improved.
In the region L, in particular, as the projection 7 is formed on the downstream side as close as possible to the inner apex portion of the refractive portion 6 ′, the exhaust gas can be greatly meandered to the left and right to improve the heat dissipation performance.

FIG. 5A shows a conventional example in which no protrusion is provided (see FIGS. 7 and 8), which is ¼ upstream of the distance from the apex portion inside the refractive portion 6 ′ to the boundary U0 between the region L and the region U. When the projection 7 is provided at the position L1 (see FIG. 4), when the projection 7 is provided at the position L2 that is 1/2 upstream, and when the projection 7 is provided at the position L3 that is 3/4 upstream, In the case where the protrusion 7 is provided at the position U0 at the boundary with the region U, the heat radiation performance (heat exchange amount) is analyzed and compared.
FIG. 5 (b) is a comparison of each example of FIG. 5 (a) by analyzing the pressure loss of the exhaust gas.
In each example, the protrusion length of the protrusion is the same.

According to FIG. 5A, it was found that heat exchange is promoted and heat dissipation performance is improved when the protrusion 7 is provided, compared to the case where the protrusion 7 is not provided.
In addition, when the protrusion 7 is provided in the region U (U0), the heat dissipation performance is higher in the case where the protrusion 7 is provided in the region L (L1, L2, L3). I understood it.
According to FIG. 5 (b), it can be seen that the pressure loss of the exhaust gas is significantly greater when the protrusion is provided in the region U (U0) than when the protrusion is provided in the region L (L1, L2, L3). It was.

In FIG. 2, the ratio of the protrusion length P of the protrusion 7 / the width A of the passage 5 before the protrusion is preferably set to be less than 1/2.
As the protrusion length P of the protrusion 7 increases, the flow rate of the exhaust gas can be increased, and the exhaust gas can be guided to the apex portion O outside the bent portion to improve the heat dissipation performance.
However, if the protrusion length P of the protrusion 7 is set to be 1/2 or more of the width A of the immediately preceding passage 5, the increase in the pressure loss of the exhaust gas becomes larger than the increase in the heat dissipation performance.

FIG. 6A shows a conventional example in which the protrusion 7 is not provided (see FIGS. 7 and 8), the protrusion length P of the protrusion 7 / the width A of the passage 5 is reduced to ¼. In this case, the heat dissipation performance (heat exchange amount) was analyzed and compared for the case of halving the same.
FIG. 6B is a comparison of the examples of FIG. 6A by analyzing the pressure loss of the exhaust gas.
In each example, a projection was formed at the same position for comparison.
According to FIG. 6A, it is found that the heat dissipation performance is improved as the protrusion length P of the protrusion is increased, while the rate of increase of the heat dissipation performance with respect to the protrusion length P is gradually reduced.
According to FIG. 6B, the pressure loss of the exhaust gas increases as the protrusion length P of the protrusion increases, and the rate of increase in pressure loss with respect to the protrusion length P gradually increases. It was found that when A was halved, the pressure loss was 2.8 times that when no protrusion was provided.

<Other aspects>
The inner fin 1 may be formed in a corrugated plate shape having a smooth curved surface such as a sinusoidal wave shape instead of forming a corrugated plate having a rectangular wave shape in cross section.

DESCRIPTION OF SYMBOLS 1 Inner fin 2 Top plate 3 Bottom plate 4 Side plate 5 Passage 6 Refraction part 7 Protrusion 10 (Conventional) Wayby fin

Claims (3)

An inner fin inserted into a heat exchange tube,
The plate material is formed into a corrugated plate shape composed of a top plate, a bottom plate, and side plates that partition the plate in a substantially vertical manner at a predetermined pitch,
Provided on both sides of each side plate a number of passages that allow gas to pass along the front-rear direction,
The side plate refracts left and right at predetermined intervals in the front-rear direction and extends in a meandering manner, and
An inner fin, wherein a protrusion projecting into a passage is formed on a wall surface of a side plate that continues from an inner vertex of the meandering refractive portion to an outer vertex of an upstream refractive portion.   2. The inner fin according to claim 1, wherein the protrusion is formed in the vicinity of the apex portion on the inner side of the meandering refractive portion.   The inner fin according to claim 1, wherein the protrusion protrudes perpendicularly to the gas flow.