JP5500399B2 - Heat exchanger - Google Patents

Description

  The present invention relates to a heat exchanger suitable for application to, for example, an exhaust heat exchanger that performs heat exchange between exhaust gas generated by combustion of an internal combustion engine and cooling water of the internal combustion engine in an EGR (exhaust gas recirculation device). Is.

  Conventionally, as shown in Patent Document 1, for example, when a part of exhaust gas discharged from an engine is circulated to the intake side of the engine in an EGR (exhaust gas recirculation device), the exhaust gas is cooled by engine cooling water. Heat exchangers for cooling are known.

  That is, this heat exchanger is formed by accommodating a plurality of stacked flat heat transfer tubes (heat transfer tube group) inside an outer case having a square cross section. An introduction part for introducing exhaust gas is formed on one side in the longitudinal direction of the outer case, and a lead-out part for leading exhaust gas is formed on the other side, and a body part is formed between the introduction part and the lead-out part. Yes.

  Moreover, the pipe expansion part is formed in the both ends position of the longitudinal direction of a heat exchanger tube, respectively, and when this pipe expansion part is laminated | stacked, it mutually joins. Furthermore, the outer peripheral part of the whole pipe expansion part joined mutually is joined to the inner wall used as the both ends part of the main-body part of an outer case.

  The main body of the outer case is formed with an inflow pipe for allowing cooling water to flow into the main body and an outflow pipe for allowing cooling water within the main body to flow out.

  In the heat exchanger, the cooling water flows from the inflow pipe into the main body portion of the outer case, flows through the main body portion (outside the plurality of heat transfer tubes), and then flows out from the outflow pipe. Further, the exhaust gas flows in from the introduction part, is distributed to each heat transfer tube, flows through each heat transfer tube, and then gathers and flows out in the lead-out part. At this time, the exhaust gas is cooled by the cooling water in the main body of the outer case.

JP 2007-225190 A

  However, in the above heat exchanger, the combustion gas temperature (700 to 800 ° C.) is used in a very high situation with respect to the cooling water temperature (90 to 100 ° C.). There is a risk that the cooling water will boil locally in the vicinity of the part.

  In view of the above problems, an object of the present invention is to provide a heat exchanger that can suppress local boiling of cooling water on the inlet side of exhaust gas.

  In order to achieve the above object, the present invention employs the following technical means.

In the first aspect of the present invention, the tube (110) includes a plurality of tubes (110) stacked in a flat cross section and a flow path (115) formed outside the tube (110). In the heat exchanger for exchanging heat between the exhaust gas of the internal combustion engine flowing through the inside and the cooling water for cooling the internal combustion engine flowing through the flow path (115), the tube (110) on the exhaust gas inflow side in a predetermined region of the outer surface protruding outwardly of the tube (110) has a plurality of convex portions (116) is formed, a convex formed on one of the outer surface of the tube (110) (110a) The shape portion (116) is formed at a position different from the convex shape portion (116) formed on the other outer surface (110b) of the tube, and when the plurality of tubes (110) are laminated, On one outer surface (110a) The formed convex portion (116) is located between the convex portions (116) formed on the other outer surface (110b) of the tube, and the flow cross-sectional area of the flow path in the predetermined region is the tube (110). It is characterized by being smaller than the flow cross-sectional area of the flow path in the general area flow other than the predetermined area .

  Thereby, the flow rate of the cooling water on the inlet side of the exhaust gas can be increased. Therefore, the heat transfer coefficient between the outer surface of the tube (110) and the cooling water can be increased, and the temperature of the temperature boundary layer of the cooling water on the outer surface of the tube (110) can be lowered, and the exhaust gas inlet Local boiling of the cooling water on the side can be suppressed.

  According to invention of Claim 2, the inner fin (120) contacted with the inner wall of a tube (110) is provided in the tube (110), The said convex-shaped part (116) The dimple (116) has a ratio of the predetermined area flow cross-sectional area to a general area flow cross-sectional area of 0.9 or less and a contact area reduction ratio between the inner wall and the inner fin (120) of 5% or more. It is characterized by that.

In a third aspect of the invention, the predetermined region is a region from the inflow end portion (118) where the exhaust gas flows into the tube (110) to the downstream side of the exhaust gas up to 80 mm. To do.
In the invention according to claim 4, the dimple (116) is provided on the outflow side of the exhaust gas from the tube (110) so as to be symmetrical with respect to the longitudinal center of the tube (110). It is a feature. Thereby, the directionality in the longitudinal direction of the tube (110) can be eliminated, and erroneous assembly at the assembly stage can be prevented.

It is a perspective view which shows the external appearance of the EGR gas cooler in embodiment. It is a disassembled perspective view which shows the main structures of the EGR gas cooler in embodiment. It is a perspective view which shows the tube 110 in embodiment. It is a graph which shows the result of the local boiling suppression of the cooling water by the dimple in embodiment.

  In the present embodiment, the heat exchanger according to the present invention is applied to an EGR gas cooler 100A in an exhaust gas recirculation device (EGR) of a diesel engine for a vehicle and a gasoline engine (which is an internal combustion engine, hereinafter referred to as an engine). Hereinafter, the configuration of the EGR gas cooler 100A will be described with reference to FIGS.

  FIG. 1 is a perspective view showing an appearance of the EGR gas cooler 100A, FIG. 2 is an exploded perspective view showing a main configuration of the EGR gas cooler 100A, and FIG. 3 is a perspective view showing a tube 110.

  The EGR gas cooler 100A is an exhaust heat exchanger that cools the exhaust gas recirculated to the engine with engine cooling water. As shown in FIGS. 1 to 3, the EGR gas cooler 100A includes a plurality of tubes 110 in which inner fins 120 are disposed, a first water side tank 130A, a second water side tank 130B, an inlet water pipe 141, It consists of an outlet water pipe 142, gas side tanks 151, 152 and the like. Each member described below is formed from a stainless steel material excellent in strength resistance and corrosion resistance, and the contact portion of each member is joined by brazing or welding.

  As shown in FIGS. 2 and 3, the tube 110 is formed of two tube plates 110a and 110b. Each of the tube plates 110a and 110b is formed into a U-shape having a shallow cross section from a flat plate by press processing or roll processing. And the tube 110 is formed as an elongate pipe member which has a flat cross section by joining the opening side of each tube plate 110a, 110b mutually.

  Inside the tube 110, an inner fin 120 that is pressed from a thin plate material into a cross-sectional wave shape is disposed. Inner fin 120 is joined to the inner surface of tube 110 (tube basic surface 111 described later). The tube 110 having the inner fins 120 is formed by joining after assembling so that the inner fins 120 are sandwiched between the tube plates 110a and 110b.

  A plurality of tubes 110 are stacked such that the tube basic surfaces 111 on the long sides of the flat cross section face each other, and are formed on the gas flow path 114 formed inside the tube 110 and on the outside of the tube 110. The water flow path 115 (detailed later) is provided.

  The tube basic surface 111 is provided with a convex portion 112 and a concave portion 113. The convex portion 112 is a stamped portion that is pressed so as to protrude outward from the surface of the tube basic surface 111, and is formed like a weir on the outer peripheral portion of the tube basic surface 111. And the recessed part 113 is formed as a dent part dented from the protrusion vertex of the said convex part 112 to the tube basic surface 111 side. In other words, the concave portion 113 is provided as a convex non-molded portion where the convex portion 112 is not molded. Here, the positions where the recesses 113 are formed are four locations on both end sides of both long sides of the tube basic surface 111.

  As shown in FIGS. 2 and 3, a plurality of the tubes 110 are laminated such that the convex portions 112 formed on the tube basic surface 111 are in contact with each other, and the convex portions 112 are joined to each other.

  Here, as shown in FIG. 3, a space is formed in the inner region of the convex portion 112 between the stacked tubes 110, and this space is a water flow path (flow path) 115 for cooling water. .

  Of the recesses 113 formed at four locations on the tube basic surface 111, the opening formed by one recess 113 in the longitudinal direction of the tube 110 communicates with the outside through the water flow path 115 and the cooling water flows in. Inflow side opening 113a to be performed (upper and lower two places in FIG. 3).

  Of the recesses 113 formed at four locations on the tube basic surface 111, the opening formed by the other recesses 113 in the longitudinal direction of the tube 110 communicates with the outside and the water flow path 115, and the cooling water flows out. It becomes the outflow side opening part 113b which performs (2 places). Here, in the gas flow path 114 (in the tube 110), the side into which the exhaust gas flows is the inflow side opening 113a, and the opposite side is the outflow side opening 113b.

  And the convex part as a temperature fall means to lower the temperature of the temperature boundary layer of the cooling water in the outer surface of the tube 110 is formed in the tube basic surface 111 which becomes the inflow side opening part 113a side of the tube 110. . Here, the convex portion is formed as a plurality of dimples 116.

  The dimple 116 is provided in a predetermined region from the inflow end portion 118 (FIG. 3) on the exhaust gas inflow side in the longitudinal direction of the tube 110 toward the downstream side. This predetermined area can be set, for example, as an area of 30 mm to 80 mm from the inflow end portion 118. More preferably, the predetermined area is an area 40 mm from the inflow end portion 118. The reason will be described later.

  The dimples 116 can be set as cylindrical convex portions having a diameter of about 4 to 6 mm, for example, and a plurality of dimples 116 are arranged in a grid pattern. The projecting dimension of the dimple 116 is the same as the projecting dimension of the protrusion 112 on the outer periphery of the tube 110. The arrangement position of the dimples 116 is different between the tube plate 110a and the tube plate 110b. That is, when the tubes 110 are stacked, the dimples 116 of the tube plate 110a are positioned between the dimples 116 of the tube plate 110b in the tube plates 110a and 110b facing each other.

  By forming the dimple 116 as described above, the flow cross-sectional area of the water channel 115 in the predetermined region of the tube 110 (predetermined region flow cross-sectional area) is the cross-sectional area of the water flow channel 115 in the general region where the dimple 116 is not formed ( Smaller than the general area cross-sectional area). Depending on the size, number, arrangement, etc. of the dimples 116, the ratio of the predetermined area flow cross section to the general area cross section is preferably 0.9 or less.

  In addition, by forming the dimple 116 as described above, the contact area between the tube basic surface 111 and the inner fin 120 is reduced. However, since the dimple 116 is intentionally provided, this contact area is provided. The reduction rate of 5% or more.

  In addition, in the present embodiment, similar dimples 116 are provided at the end portion on the exhaust gas outflow side in the longitudinal direction of the tube 110. That is, the dimple 116 is provided so as to be symmetric with respect to the longitudinal center of the tube 110.

  As shown in FIG. 2, the first water-side tank 130A and the second water-side tank 130B are bent at approximately 90 degrees from the four corners of the main body 131 to the tube 110 side. In addition, each of the openings 113a and 113b is provided with an extension part 132 that is extended so as to enclose each of the openings 113a and 113b, and is assembled and joined so as to be covered from the outside of the stacked tubes 110.

  The main body 131 includes an outer peripheral portion 131a that contacts the convex portion 112 of the tube 110 and a bulging portion 131b that bulges outward from the outer peripheral portion 131a in the stacking direction of the tube 110 in an inner region of the outer peripheral portion 131a. I have.

  In addition, the overhang portion 132 includes an outer peripheral portion 132a that comes into contact with each of the openings 113a and 113b in the side surface portion of the tube 110, and an inner region of the outer peripheral portion 132a. And a bulging portion 132b that bulges outward.

  A water channel 115 similar to the water channel 115 formed between the tubes 110 is formed between the outermost tube 110 (tube basic surface 111) and the bulging portion 131b of the main body 131. Openings 113 a and 113 b similar to the openings 113 a and 113 b formed between the tubes 110 are formed between the recess 113 of the outermost tube 110 and the bulging portion 131 b of the main body 131. . In addition, a space is formed between a side surface portion of the tube 110 (a position corresponding to each of the openings 113a and 113b) and the bulging portion 132b of the overhanging portion 132.

  In the first water side tank 130A and the second water side tank 130B, the overhang length of the overhang portion 132 is different, and the overhang length of one overhang portion 132 (upper side of 130A in FIG. 2). However, the dimension of the tube 110 is almost the same as that of the tube 110, and the extension length of the other extension portion 132 (the upper side of 130B in FIG. 2) is a predetermined length with respect to the distal end portion of the one extension portion 132. The dimensions are such that they overlap each other. On the lower side, the above is reversed.

  The bulging portion 132b of the bulging portion 132 (upper side in FIG. 2) corresponding to the inflow side opening portion 113a of the first water-side tank 130A is formed with a pipe bulging portion 132c that further bulges in a bowl shape. The pipe bulge portion 132c is provided with a pipe hole 132d for connecting the inlet water pipe 141 having a burring portion (edge stand portion). Although not shown, like the first water side tank 130A, the bulging part of the overhanging part (the bottom side in FIG. 2) corresponding to the outflow side opening 113b of the second water side tank 130B. Is formed with a pipe bulging portion that further swells in a bowl shape, and a pipe hole for connecting the outlet water pipe 142 provided with a burring portion (edge portion) is formed in the pipe bulging portion. It is installed.

  The inlet water pipe 141 is a pipe into which cooling water from the engine flows, and the tip portion is inserted into and joined to the pipe hole 132d. The inlet water pipe 141 communicates with the inflow side opening 113a of the tube 110 through the pipe bulge 132c and the bulge 132b.

  The outlet water pipe 142 is a pipe through which the cooling water flowing through the water flow path 115 of the tube 110 flows out, and the tip of the outlet water pipe 142 is in the pipe hole of the bulging portion (piping bulging portion) of the second water side tank 130B. Inserted and joined. The outlet water pipe 142 communicates with the pipe bulge and the outflow side opening 113b of the tube 110 via the bulge.

  As shown in FIG. 2, the gas side tanks 151, 152 are formed in a funnel shape as a whole, and a side having a large opening has a quadrangular shape and a side having a small opening has a circular shape.

  The sides of the gas-side tanks 151 and 152 that open in a square shape are in contact with and joined to the outer periphery of a plurality of stacked tubes 110. The insides of the gas side tanks 151 and 152 communicate with the inside (gas flow path 114) of a plurality of stacked tubes 110. Further, flanges 151b and 152a connected to the exhaust gas recirculation (EGR) side are joined to the sides (tip portions) of the gas side tanks 151 and 152 that open in a circular shape.

  In the EGR gas cooler 100A configured as described above, as shown in FIG. 1, a part of the exhaust gas discharged from the engine passes through the flange 151a → the gas side tank 151 and the gas flow paths in the tubes 110 114 flows through the gas side tank 152 → the flange 152a. The exhaust gas that has flowed out is again taken into the engine.

  On the other hand, the engine coolant passes between the plurality of tubes 110 through the inlet water pipe 141 on the exhaust gas inflow side → the bulging portions 132c and 132b of the overhanging portion 132 → the upper inflow side opening portions 113a. Through the formed water flow path 115 and the water flow path 115 formed between the outermost tube 111 and the bulging portion 131b, each bulging portion of the outflow side opening 113b and the bulging portion 132 → Outflow from outlet water pipe 142.

  A part of the cooling water flowing in from the inlet water pipe 141 once hits the bulging portion 132b from the lower inflow side opening 113a, and again makes a U-turn and flows in the water flow path 115.

  Then, heat exchange is performed between the exhaust gas flowing through the gas flow path 114 and the cooling water flowing through the water flow path 115 to cool the exhaust gas.

  In the present embodiment, the heat transfer coefficient between the outer surface of the tube 110 and the cooling water is increased to a predetermined region on the outer surface of the tube 110 on the exhaust gas inflow side to the tube 110, A convex portion is provided as temperature lowering means for lowering the temperature of the temperature boundary layer of the cooling water on the surface.

  Therefore, since the temperature on the outer surface of the tube 110 can be lowered, local boiling of the cooling water on the inlet side of the exhaust gas can be suppressed.

  Specifically, the convex portion is formed as a plurality of dimples 116, and by this dimple 116, the predetermined area flow cross-sectional area in the predetermined area is smaller than the general area flow cross-sectional area in the general area (0.9 or less). I am doing so.

  Therefore, the flow rate of the cooling water on the inlet side of the exhaust gas can be increased, the heat transfer coefficient between the outer surface of the tube 110 and the cooling water is increased, and the temperature boundary layer of the cooling water on the outer surface of the tube 110 is increased. The temperature can be lowered and local boiling of the cooling water on the inlet side of the exhaust gas can be suppressed.

  FIG. 4 is a graph showing the result of suppression of local boiling of the cooling water by the dimple 116. The confirmation conditions were an exhaust gas temperature of 700 ° C., a gas flow rate of 12.5 g / s, an inlet side cooling water temperature of 90 ° C., and a cooling water flow rate of 12 L / min. The system pressure of the cooling water is 1.1 kPa. Further, as the EGR gas cooler 100A, a dimple 116 not provided (conventional technology), a dimple 116 having a diameter of 4 mm (dimple 1 specification), and a 6 mm diameter (dimple 2 specification) were prepared. The dimple 116 was provided in a region of 30 mm downstream from the inflow end portion 118 of the tube 110.

  In the prior art without the dimple 116, the wall surface temperature (outer surface temperature) of the tube 110 exceeded the boiling point of cooling water (about 127 ° C.) at a system pressure of 1.1 kPa in the range of 40 mm from the inflow end 118. . However, in the dimple 1 specification, the heat transfer coefficient (αw) on the cooling water side can be 1.15 times that of the prior art, and the range where the wall surface temperature of the tube 110 exceeds the boiling point of the cooling water is within the inflow end. The portion 118 could be reduced to a range of 20 mm. Furthermore, in the dimple 2 specification, the heat transfer coefficient (αw) on the cooling water side can be made 1.3 times that of the prior art, and the range where the wall surface temperature of the tube 110 exceeds the boiling point of the cooling water can be eliminated. did it.

  From the above result, it is preferable that the region where the dimple 116 is set is in a range of 30 mm or more from the inflow end portion 118 (0 mm) of the tube 110. The upper limit of the area setting is preferably up to 80 mm in consideration of an increase in the resistance of cooling water flow. The optimum value for the region setting is preferably in the range of 40 mm from the inflow end portion 118 (0 mm) where local boiling can occur in view of the result of the prior art product.

  Further, the dimple 116 is provided on the exhaust gas outflow side from the tube 110 so as to be symmetrical with respect to the center in the longitudinal direction of the tube 110. Can be eliminated to prevent erroneous assembly at the assembly stage.

(Other embodiments)
In the embodiment described above, the dimples 116 are provided on both ends in the longitudinal direction in order to eliminate the longitudinal directionality of the tube 110. Basically, the dimples 116 may be provided on the exhaust gas inflow side.

  In the above embodiment, the recesses 113 of the tube 110 are provided at four locations on the tube 110. However, the inflow side opening portions 113a corresponding to the inlet water pipe 141 are provided at two locations on the diagonal. The outlet side opening 113b corresponding to the outlet water pipe 142 may be formed.

  Further, the tube 110 may be formed from an integral tube member without being formed from the two tube plates 110a and 110b.

  In the above embodiment, the heat exchanger of the present invention has been described as applied to the EGR gas coolers 100A and 100B. However, the present invention is not limited to this, and can be widely applied to other heat exchangers. The present invention may be applied to an exhaust heat recovery heat exchanger that heats the cooling water by exchanging heat between the exhaust gas discharged to the outside air and the cooling water.

  In the above embodiment, the basic material of the member constituting the heat exchanger is a stainless steel material. However, the material is not limited to this, and other materials such as an aluminum alloy and a copper alloy are used depending on the application. Is also applicable.

100 EGR gas cooler (heat exchanger)
110 Tube 115 Water channel (channel)
116 dimples (convex parts)
118 Inflow end portion 120 Inner fin 141 Inlet water pipe (inflow portion)
142 Outlet water pipe (outflow part)

Claims (4)

A plurality of tubes (110) laminated in a flat cross section;
A flow path (115) formed outside the tube (110),
In the heat exchanger for exchanging heat between the exhaust gas of the internal combustion engine flowing through the tube (110) and the cooling water for cooling the internal combustion engine flowing through the flow path (115),
A plurality of convex portions (116) are formed in a predetermined region on the outer surface of the tube (110) on the exhaust gas inflow side so as to protrude outward from the tube (110) ,
The convex portion formed on the outer surface (110a) of one of the said tube (110) (116), said convex portion formed on the other outer surface (110b) of the tube and (116) They are formed at different positions, and when stacking a plurality of tubes (110), the other of the outer surface of the convex portion formed on the outer surface (110a) of one of the said tube (116) is the tube (110b) located between the convex portions (116) formed ,
The heat exchanger according to claim 1, wherein a flow cross-sectional area of the flow path in the predetermined area is smaller than a flow cross-sectional area of the flow path in the general area flow other than the predetermined area of the tube (110) . In the tube (110), an inner fin (120) that contacts an inner wall of the tube (110) is provided, and the convex portion (116) has a predetermined area flow cross section with respect to the general area flow cross-sectional area. The dimple (116) according to claim 1, wherein the dimple (116) has a cross-sectional area ratio of 0.9 or less and a contact area reduction ratio between the inner wall and the inner fin (120) of 5% or more. Heat exchanger. The heat according to claim 2, wherein the predetermined region is a region from the inflow end (118) through which the exhaust gas flows into the tube (110) to 80 mm downstream of the exhaust gas. Exchanger. The dimple (116) is provided on the outflow side of the exhaust gas from the tube (110) so as to be symmetrical with respect to the longitudinal center of the tube (110). The heat exchanger according to claim 2 or claim 3.

Images