JP2008008568A - Heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger which avoids formation of a stagnation part in a cooling liquid side of a tube plate on a gas inlet side even when a large thermal load is applied to the heat exchanger, and positively cools a junction by sufficiently supplying a cooling liquid to the junction between a heat transfer tube and the tube plate. <P>SOLUTION: In the heat exchanger 1, a plurality of heat transfer tubes 13 with both ends respectively fixed by tube plates 11, 12 is arranged in a shell 14, gas Ge is sent through heat transfer tube 13 interiors, and the cooling liquid W is sent over heat transfer tube 13 exteriors to cool the gas Ge. A guide passage 11a guiding the cooling liquid W along one part or all of an inner circumference of the shell 14 is provided on a liquid communicating side of the tube plate 11 on an inlet side of the gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat exchanger, and more particularly to a heat exchanger that can sufficiently cool a joint portion between a heat transfer tube and a tube sheet that is likely to become high temperature on the gas inlet side.

  In order to cool the EGR gas of an internal combustion engine used in an automobile or the like, an EGR cooler having a structure as shown in FIG. 6 is used. The EGR cooler cools the EGR gas by passing EGR gas through a circular pipe, which is a plurality of heat transfer tubes (cores) housed in a case, and passing cooling water through the outer periphery of the circular pipe. This cooling reduces the volume of the EGR gas and increases the amount of EGR gas that recirculates into the engine cylinder. Also, the temperature of the mixed gas of fresh air and EGR gas supplied into the cylinder is reduced. This reduces the deterioration of combustion.

  As this EGR cooler, for example, a partition plate (tube plate) in which both ends of a plurality of tubes (heat transfer tubes) are fixed is arranged inside an outer cylinder (trunk), and at least one surface of the heat transfer surface is coated with a nonmetal as a thin film There has been proposed a heat exchanger in which EGR gas is allowed to flow through the treated tube, and cooling water is allowed to flow inside the outer cylinder and outside the tube between the partition plates to cool the EGR gas (see, for example, Patent Document 1). .

  In addition, a heat exchanging tube (heat transfer tube) and end plates (tube plates) that support both ends of the tube are built in the shell (trunk), and the tube and end plate, and between the end plate and shell are placed in the furnace. A method of manufacturing an EGR cooler is proposed in which a heat exchanger core part is integrally formed by brazing the joints of the heat exchanger, and the header is attached to both ends of the shell after the shell is brazed, and the header is hermetically secured to the shell. (For example, refer to Patent Document 2).

  This cool EGR system has become an indispensable technology as a combustion control technology corresponding to recent exhaust gas regulations, and in order to introduce a larger amount of EGR gas, the thermal load on the EGR cooler is increasing. Especially in the North American specification, a large amount of EGR is required even in the high-speed and high-load region, so the heat transfer tube (core) becomes high temperature, especially at the gas inlet side (high temperature side) welding or brazed joints, As a result, the possibility of occurrence of cracks, peeling, etc. increases, which has become a problem in terms of durability of the EGR cooler.

In a heat exchanger having a conventional structure, an inlet of cooling water is provided on the gas inlet side where the temperature of the heat transfer tube increases due to the flow of high-temperature gas, and the temperature of the joint is lowered with relatively low-temperature cooling water. Yes. However, since a stagnation portion where the cooling water hardly flows is generated near the wall surface (shaded portion in FIG. 6) A at the position opposite to the inlet where the cooling water is injected, the temperature is high in this vicinity. The heat transfer between the heat transfer tube and the cooling water is lowered, and the cooling of this portion is deteriorated. As a result, the temperature rises most at the joint of this part, and becomes significantly higher than the joint near the cooling water inlet. In addition, when the cooling water is boiled in the stagnation portion due to a large heat load, it becomes easy to cause defects such as cracks and peeling at the joint portion. Once a malfunction occurs in this part, the coolant enters the EGR gas and enters the engine cylinder together with the EGR gas, which may cause serious troubles such as seizing and water hammer. Arise.
JP 2006-90833 A JP 2006-57475 A

  The present invention has been made to solve the above-described problems, and the purpose thereof is to provide a liquid for cooling the tube plate on the gas inlet side even when a large heat load is applied to the heat exchanger. The present invention provides a heat exchanger that can avoid the occurrence of a stagnation portion on the side, can sufficiently supply a cooling liquid to the joint portion between the heat transfer tube and the tube sheet, and can cool the joint portion reliably. .

  A heat exchanger for achieving the above-described object has a plurality of heat transfer tubes each having both ends fixed to a tube plate in a cylinder, allows gas to flow in the heat transfer tubes, and cools the heat transfer tubes outside. In the heat exchanger that flows the liquid for cooling and cools the gas, an introduction passage is provided on the liquid flow side of the tube plate on the gas inlet side to guide the cooling liquid along part or all of the inner periphery of the cylinder. Configured.

  According to this configuration, since the cooling liquid is guided along the part or the entire circumference of the body (shell, casing) on the liquid flow side of the tube plate on the gas inlet side by the introduction passage, It is possible to avoid stagnation of the liquid. As a result, the welded and brazed joint between this heat transfer tube (tube) and the tube plate (end plate, header plate) for fixing and supporting this heat transfer tube can be cooled sufficiently. It is possible to prevent cracking and peeling of the part.

  Further, according to this configuration, since the cooling liquid is guided to or near the liquid flow side of the tube plate on the gas inlet side by the introduction passage, the cooling effect on the tube plate is increased, and the cooling efficiency for the joint portion is increased. Get better. Furthermore, since the cooling liquid is guided along the inner periphery of the cylinder, it is possible to generate a swirling flow in the cylinder and increase the heat transfer efficiency of the heat transfer tube.

  In the above heat exchanger, when the introduction passage is formed by a groove-like passage provided on the liquid flow side of the tube plate on the gas inlet side and along the inner periphery of the cylinder, the introduction passage has a relatively simple configuration. Can be provided. The groove-like passage can be provided integrally with the tube plate on the outer peripheral side of the tube plate, and a ring-like body or groove-like passage is formed on the fluid circulation side of the tube plate. It is also possible to arrange and provide a ring-shaped body. Further, the groove-shaped passage may have a concave cross section where the central portion side of the cylinder is opened when viewed in a side cross section, and the central portion side of the cylinder and the downstream side of the gas are opened. It may have an L-shaped cross section. In addition, when providing integrally with a tube sheet, the liquid distribution | circulation side of a tube sheet may be cut into a groove shape, and a groove-shaped channel | path may be formed.

  Further, in the case of the introduction passage of the groove-like passage, the introduction of the cooling liquid from the tangential direction of the inner periphery of the cylinder is facilitated so that the cooling liquid can be easily guided along a part or all of the inner periphery of the cylinder. The cooling liquid supply pipe is preferably attached in the tangential direction of the inner periphery of the cylinder and connected to the introduction passage.

  Further, in the above heat exchanger, if the depth in the radial direction of the cylinder in the groove-shaped passage is formed so as to become shallower as it moves away from the cooling liquid inlet, the liquid introduced into the groove-shaped passage is Since it is gradually discharged to the center side of the body, it has a flow velocity toward the center side, and a flow toward the center can be intentionally caused.

  Further, in the above heat exchanger, the introduction passage is formed by a pipe-like passage provided on the liquid circulation side of the tube plate on the gas inlet side and along the inner periphery of the cylinder, and the pipe-like passage is cooled. When the liquid outlet is provided, the introduction passage can be easily formed simply by connecting the ring-shaped pipe to the cooling liquid supply port. In addition, by providing an outlet in the pipe, the cooling liquid can be allowed to flow out aiming at a portion that is prone to stagnation, so that stagnation can be further avoided.

  Further, when the direction of the outlet is directed toward the center of the cylinder, it becomes easier to supply the cooling liquid to the center of the cylinder, so that the joint at the center can be further cooled. Further, since the outflow direction and the outflow speed can be selected depending on the opening direction and the opening amount of the outflow port, it is possible to generate a swirling flow in the trunk and increase the heat transfer efficiency of the heat transfer tube.

  Alternatively, in the heat exchanger of the present invention for achieving the above object, a plurality of heat transfer tubes each having both ends fixed to a tube plate are arranged in a cylinder, gas is allowed to flow in the heat transfer tubes, and the heat transfer tubes In a heat exchanger for cooling a gas by flowing a cooling liquid outside, a plurality of supply ports for supplying the cooling liquid into the body are provided along the liquid circulation side of the tube plate on the gas inlet side. .

  Since the cooling liquid supplied from the plurality of supply ports can avoid the occurrence of stagnation, the welded or brazed joint between the heat transfer tube and the tube sheet can be sufficiently cooled, and the joint Cracks and peeling can be prevented. Furthermore, when the cooling liquid is supplied with a flow velocity component in the tangential direction of the inner circumference of the cylinder, a swirl flow can be generated in the cylinder, so that the heat transfer efficiency of the heat transfer tube can be increased.

  And in said heat exchanger, when the said gas is EGR gas of an internal combustion engine, ie, when this heat exchanger is made into an EGR cooler, an engine requires a lot of EGR by high load operation. Even in such an operating state, the joint portion between the heat transfer tube and the tube sheet of the EGR cooler can be sufficiently cooled, so that the joint portion can be prevented from cracking or peeling and reliability can be ensured. As a result, it is possible to provide an engine capable of realizing low emission combustion that can meet the strict exhaust gas regulations in North America.

  As described above, according to the heat exchanger according to the present invention, even if a large heat load is applied to the heat exchanger, the stagnation portion is provided on the cooling liquid side of the tube plate on the gas inlet side. Generation | occurrence | production can be avoided and the liquid for cooling can be supplied to the junction part of a heat exchanger tube and a tube sheet, and a junction part can fully be cooled.

  Hereinafter, a heat exchanger according to an embodiment of the present invention will be described with an EGR cooler used for an internal combustion engine (engine) as an example with reference to the drawings.

  1 to 5 show a heat exchanger 1 according to a first embodiment. The heat exchanger 1 includes a plurality of heat transfer tubes (cores and tubes) 13 fixed at both ends to tube plates (end plates and header plates) 11 and 12 in a body (shell and casing) 14. It is formed. One of the cylinders 14 is provided with an inlet-side pipe 15 to which high-temperature EGR gas (gas) is supplied, and the other is provided with an outlet-side pipe 16 through which cooled EGR gas (gas) is discharged.

  The heat transfer tube 13 is formed of a metal such as stainless steel, and one end thereof is connected to the tube plate 11 on the inlet side by welding or brazing and fixed. Further, the other end is connected and fixed to the tube sheet 12 on the outlet side by welding or brazing. These tube plates 11 and 12 are formed of a metal such as stainless steel, and are fixed to a body 14 formed of a metal such as stainless steel by welding or brazing. In some cases, one end side is not fixed in consideration of thermal expansion. An inlet side pipe 15 and an outlet side pipe 16 are connected to the barrel 14 by welding, brazing, a flange, or the like.

  In the EGR cooler, EGR gas (gas) Ge is caused to flow in the heat transfer tube 13, and cooling water (cooling liquid) W is supplied from the cooling water supply tube 17 into the body 14, and then flows outside the heat transfer tube 12. After the EGR gas Ge is cooled, it is discharged from the cooling water discharge pipe 18.

  In the present invention, the introduction passage formed by the groove-like passage along the inner circumference of the barrel 14 on the liquid circulation side of the tube plate 11 on the inlet side of the EGR gas Ge or in the vicinity thereof. 11a is provided and configured. Thereby, the introduction passage 11a can be provided with a relatively simple configuration.

  In the configuration of FIGS. 1 to 5, the introduction passage 11 a of the groove-like passage is provided integrally with the tube plate 11, and when viewed in a side cross section, the center portion side of the body 14 and the downstream side of the EGR gas Ge Is formed by cutting the liquid flow side of the tube plate 11 into a groove shape so as to have an L-shaped cross section. Further, the groove depth d in the radial direction of the trunk 14 in the introduction passage 11a is made shallower as it goes away from the supply port 17a of the cooling water W, in other words, a front view (a state seen from the axial direction of the trunk 14). It is formed to have a spiral recess.

  The introduction passage 11a of the groove-shaped passage is not limited to this configuration, and may have a concave cross section in which the central portion side of the trunk is open, and the groove-shaped passage 11a is formed on the fluid circulation side of the tube plate 11. Alternatively, a ring-shaped body in which a groove-shaped passage 11a is formed may be provided. Further, instead of providing the introduction passage 11 along the entire inner circumference of the cylinder 14, it can be provided along a part of the inner circumference of the cylinder 14 so as to supply the cooling water W only to the portion that is easily stagnant. .

  Further, in the case of the groove-shaped passage 11a, the cooling water supply pipe 17 is attached in the tangential direction of the inner periphery of the body 14 so that the cooling water W can be easily guided along the inner periphery of the body 14, and is connected to the introduction passage 11a. Then, the cooling water W is supplied to the introduction passage 11a from the tangential direction of the inner periphery of the body 14.

  By this introduction passage 11a, the cooling water W can be guided along a part or all of the inner periphery of the barrel 14 on the liquid flow side of the tube plate 11 on the inlet side, so that the cooling water W is prevented from being stagnation. it can. As a result, the welded or brazed joint 19 between the heat transfer tube 13 and the tube sheet 11 can be sufficiently cooled, and cracking and peeling of the joint 19 can be prevented.

  In particular, since the cooling water W is guided to the liquid flow side of the tube plate 11 on the inlet side or the vicinity thereof by the introduction passage 11a, the cooling effect on the tube plate 11 is increased, and the cooling efficiency for the joint portion 19 is improved. Furthermore, since the cooling water W is guided along the inner periphery of the cylinder 14, a swirl flow can be generated in the cylinder 14 to increase the heat transfer efficiency of the heat transfer tube 13.

  Further, since the groove depth d in the radial direction of the body 14 in the introduction passage 11a is formed so as to become shallower as it moves away from the supply port 17a of the cooling water W, the cooling water W introduced into the introduction passage 11a. Is gradually discharged toward the center of the body 14. As a result, since the cooling water W flows along the tube plate 11 through the introduction passage 11 a, the cooling water W has a circumferential velocity component Va in a direction that wraps around the inner periphery of the cylinder 14, and a flow velocity toward the center of the cylinder 14. That is, it also has a center direction velocity component Vb (see FIG. 5), and can intentionally cause a flow toward the center. Further, since the cooling water W is directed to the cooling water discharge port 18a by the sequential supply of the cooling water W, it has an axial velocity component Vc (not shown) in a direction parallel to the axis of the body 14.

  That is, the cooling water W has a circumferential velocity component Va, a central velocity component Vb, and an axial velocity component Vc (not shown). For this reason, the circumferential velocity component Va eliminates the stagnation portion of the cooling water W in the vicinity of the joint portion 19 between the heat transfer tube 13 and the tube plate 11, which is a problem in the conventional structure, and makes the connection portion 19 having the highest temperature uniform. By cooling, it is possible to prevent the occurrence of a failure of the connection portion 19 due to a high temperature. At the same time, the center portion of the barrel 14 can be cooled by the central velocity component Vb, and the EGR gas Ge passing through the heat transfer tube 13 can be cooled as usual by the axial velocity component Vc. .

  As described above, according to the heat exchanger according to the present invention, the cooling water W of the EGR cooler 1 is introduced from one place, and the introduced cooling water W is on the side where the highest temperature is likely to be the highest in the prior art. Since the surrounding portion and the joint portion 19 can be sufficiently cooled, it is possible to prevent the occurrence of defects such as cracks and peeling of the connection portion due to the high temperature.

  Therefore, the reliability of the joint between the heat transfer tube 13 and the tube plate 11 of the EGR cooler 1 can be ensured even in an operation state in which the engine is in a high load operation state and requires a large amount of EGR. An engine equipped with the EGR cooler 1 can realize low emission combustion that can meet strict exhaust gas regulations in North America.

  Next, a second embodiment will be described. In the EGR cooler (heat exchanger) 1A according to the second embodiment shown in FIG. 6, instead of the introduction passage 11a formed by the groove-like passage in the EGR cooler 1 according to the first embodiment, the introduction passage is provided as an inlet. The pipe-shaped passage 20 is formed on the liquid flow side of the tube plate 11 on the side and along the inner periphery of the body 14, and cooling water (cooling liquid) is formed in the pipe-shaped passage 20 formed of a metal such as stainless steel. ) Provide one or several W outlets 20a. Other configurations are the same as those of the first embodiment.

  In the EGR cooler 1A having the introduction passage 11a formed by the pipe-like passage 20 of the second embodiment, the introduction passage 20 can be easily formed simply by connecting the ring-like pipe 20 to the supply port 17a of the cooling water W. Can be formed. In addition, by providing the outlet 20a in the pipe-shaped passage 20, the cooling water W can be flowed out aiming at a portion where the cooling water W tends to stagnate, so that the occurrence of stagnation can be avoided.

  Further, when the direction of the outlet 20a is directed toward the center of the body 14, the cooling water W can be easily supplied to the center of the body 14, so that the joint 19 on the center can be further cooled. Further, since the outflow direction and outflow speed can be selected depending on the opening direction and the opening amount (opening size) of the outlet 20a, a swirling flow is generated in the body 14 to increase the heat transfer efficiency of the heat transfer tube 13. You can also.

  Next, a third embodiment will be described. In the EGR cooler (heat exchanger) 1B of the third embodiment shown in FIG. 7, instead of the introduction passage 11a formed by the groove-like passage in the EGR cooler 1 of the first embodiment, cooling water (cooling) A plurality of supply ports 17a for supplying the liquid W to the body 14 are provided along the liquid flow side of the tube plate 11 on the inlet side. Other configurations are the same as those of the first embodiment.

  Since the generation of stagnation can be avoided by the cooling water W supplied from the plurality of supply ports 17a, the welded and brazed joint 19 between the heat transfer tube 13 and the tube plate 11 can be sufficiently cooled. Further, it is possible to prevent the joint 19 from being cracked or peeled off. Furthermore, if the cooling water W is supplied with a flow velocity component in the tangential direction of the inner circumference of the cylinder 14, a swirl flow can be generated in the cylinder 14, so that the heat transfer efficiency of the heat transfer tube 13 can be increased.

It is a figure which shows the structure of the heat exchanger (EGR cooler) of 1st Embodiment which concerns on this invention. It is an AA arrow line view of FIG. It is a front view which shows the structure of the tube sheet of the inlet_port | entrance side of FIG. FIG. 4 is a transverse sectional view showing a configuration of a tube sheet on the inlet side in FIG. 3. It is a figure which shows the flow of a cooling water typically. It is a figure which shows the structure of the heat exchanger (EGR cooler) of 2nd Embodiment which concerns on this invention. It is a figure which shows the structure of the heat exchanger (EGR cooler) of 3rd Embodiment which concerns on this invention. It is a figure which shows the structure of the heat exchanger (EGR cooler) of a prior art.

Explanation of symbols

1,1A, 1B EGR cooler (heat exchanger)
11 Inlet side tube sheet 11a Grooved passage (introduction passage)
12 Tube plate on outlet side 13 Heat transfer tube 14 Body 17 Cooling water supply tube 17a Cooling water supply port 18 Cooling water discharge tube 19 Junction between heat transfer tube and tube plate 20 Pipe-shaped passage (introduction passage)
20a Outlet of cooling water d Depth of cylinder in radial direction in introduction passage Ge EGR gas Vr Central velocity component Va Circumferential velocity component Vb Axial velocity component W Cooling water

Claims (6)

  In a heat exchanger that cools the gas by arranging a plurality of heat transfer tubes fixed at both ends of the tube plate in the cylinder, flowing a gas into the heat transfer tube, flowing a cooling liquid outside the heat transfer tube, A heat exchanger characterized in that an introduction passage for guiding a cooling liquid along a part or all of the inner periphery of the cylinder is provided on the liquid circulation side of the tube plate on the gas inlet side.   The heat exchanger according to claim 1, wherein the introduction passage is formed by a groove-like passage provided on the liquid flow side of the tube plate on the gas inlet side and along the inner periphery of the cylinder.   3. The heat exchanger according to claim 2, wherein a depth of the trunk in the groove-like passage is formed so as to become shallower as the distance from the cooling liquid injection port is increased.   The introduction passage is formed by a pipe-like passage provided on the liquid circulation side of the tube plate on the gas inlet side and along the inner periphery of the trunk, and an outlet for cooling liquid is provided in the pipe-like passage. The heat exchanger according to claim 1, wherein   In a heat exchanger that cools the gas by arranging a plurality of heat transfer tubes fixed at both ends of the tube plate in the cylinder, flowing a gas into the heat transfer tube, flowing a cooling liquid outside the heat transfer tube, A heat exchanger characterized in that a plurality of supply ports for supplying the cooling liquid into the cylinder are provided along the liquid flow side of the tube plate on the gas inlet side. The heat exchanger according to any one of claims 1 to 5, wherein the gas is EGR gas of an internal combustion engine.

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