JP3939090B2 - Multi-tube heat exchanger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an inner tube (heat transfer tube) group through which a first fluid passes and an outer tube (fuselage) through which a second fluid passes, and a plurality of heat transfer tube groups introduce the first fluid at both ends thereof. The present invention relates to a multi-tubular heat exchanger that is disposed while being held by an introduction side / discharge side holding plate respectively positioned on the side and the first fluid discharge side. In particular, heat exchangers that exchange heat by passing high-speed high-temperature gas (gas) through the heat transfer tube group and cooling water (liquid) through the body (outer tube), for example, cooling the exhaust gas of an internal combustion engine with cooling water It is an invention suitable for an exhaust cooler (which requires a high degree of heat exchange capability).
[0002]
[Background]
As described above, a multi-tube heat exchanger 12 as shown in FIGS.
[0003]
In other words, a plurality of inner pipes (heat transfer pipes) 14 through which the first fluid (hot gas) passes and an outer pipe (fuselage) 16 through which the second fluid (cooling water) passes are provided. .. (Heat transfer tube group) 14, 14... Are disposed with their both ends held by the introduction side / discharge side holding plates 18, 20 located on the first fluid introduction side and the first fluid discharge side, respectively. In the illustrated example, a large number of heat transfer tube groups 14, 14... Are disposed inside the body 16 via introduction / discharge side holding plates (tube sheets) 18 and 20 at both ends of the body 16. Both ends of the body 16 are provided with inlet / outlet ports (connection pipes) 26 and 28 with flanges 26a and 28a via frustoconical introduction / discharge side rectification cylinder portions (rectification portions) 22 and 24, respectively. The first fluid (hot gas) can pass through the heat tube groups 14, 14. In addition, on the upper and lower sides of the body 16, introduction / discharge nozzles 30 and 32 are provided, and a second fluid (cooling water) can pass outside the heat transfer tubes 14.
[0004]
However, when the number of heat transfer tubes 14 is increased to increase the heat exchange efficiency, the multi-tube heat exchanger 12 as shown in FIGS. As a result, it has been difficult to increase the heat exchange efficiency due to a decrease in the heat transfer rate and the accompanying decrease in the heat transfer coefficient.
[0005]
Further, the multi-tubular heat exchanger 12 has a large manufacturing man-hour and a tendency to increase its weight.
[0006]
In view of the above, the inventors of the present invention have provided a multi-tube heat exchanger having the following configuration in order to provide a multi-tube heat exchanger that can easily increase the heat exchange efficiency and can reduce the number of manufacturing steps. An exchange was previously proposed (Japanese Patent Application No. 2000-061541: unpublished at the time of filing).
[0007]
“In a multi-tube heat exchanger in which a plurality of heat transfer tubes are arranged inside the fuselage, each heat transfer tube is connected between the heat transfer tube main body having a flat cross section and the opposing surfaces in the longitudinal direction of the heat transfer tube main body. It consists of a single heat transfer fin. "
The present invention mainly relates to an improvement of a multi-tube heat exchanger having the above-described configuration, and an object of the present invention is to provide a multi-tube heat exchanger that can be expected to further reduce manufacturing steps and increase heat exchange efficiency. is there.
[0008]
[Means for Solving the Problems]
As a result of diligent efforts to solve the above-mentioned problems, the present inventors have conceived a multitubular heat exchanger having the following configuration.
[0009]
An inner tube (heat transfer tube) group through which the first fluid passes and an outer tube (fuselage) through which the second fluid passes, and a plurality of heat transfer tube groups are connected to the first fluid introduction side and the first In the multi-tube heat exchanger that is arranged to be held by the introduction side / discharge side holding plate respectively positioned on the fluid discharge side,
The heat transfer tube is composed of a heat transfer tube main body having a flat cross section and a plurality of heat transfer fins connecting between the opposing surfaces in the longitudinal direction of the heat transfer tube main body or projecting from both or one of the opposing surfaces. Plate-like or knob-like protrusions are formed at predetermined intervals (predetermined pitches) in the longitudinal direction on the wall surfaces of the respective divided flow paths of the heat transfer tubes formed by the heat fins , and eddy currents can be generated in the first fluid. It is characterized by being.
[0011]
Since the protrusions are formed at a predetermined pitch on the wall surface of the flow path of the heat transfer tube, a vortex flow (longitudinal vortex flow) is generated when the first fluid such as high-speed gas passes through the heat transfer tube. Due to the presence of the vortex, the first fluid such as high-speed gas is disturbed, and the heat transfer coefficient (heat exchange efficiency) is relatively increased.
[0012]
Further, in the above configuration, each heat transfer tube has a structure in which a heat transfer fin is formed by inserting and joining a corrugated plate separate from the heat transfer tube main body to a heat transfer tube main body formed of a flat tube, It is desirable that the protrusions be formed by cutting (pressing out) or stamping the wall surface. This is because, when the corrugated plate is manufactured by press working or the like, a protrusion having an arbitrary shape according to the design (specification) can be easily formed at the same time, and the productivity is good.
[0013]
The protrusion is plate-shaped, and (1) the angle of attack is 20 to 80 °. (2) The height and width are 0.1 to 0.8 times the channel height and channel width, respectively. (3) It is desirable that the pitch in the flow direction is 1 to 5 times the height of the flow path in order to increase the heat transfer coefficient (heat exchange efficiency).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. About the part corresponding to the above-mentioned example, the last two digits were attached | subjected as the same number.
[0015]
FIGS. 3 and 4 show an example of the multi-tube heat exchanger 112 to which the present embodiment is applied (cited from FIGS. 3 and 4 in the above-mentioned prior application. However, the reference numerals are different).
[0016]
That is, a plurality of heat transfer tubes 114 are arranged via the fixed tube plates 118 and 120 in a rectangular tube body 116 provided with introduction side / extraction side holding plates (tube sheets) 118 and 120 at both ends. The first fluid inlet / outlet (connecting pipe) 126 with flanges 126a and 128a are provided at both ends of the rectangular cylinder body 116 via square-pyramidal inlet / outlet side rectifying cylinders (rectifiers) 122 and 124, respectively. 128, the first fluid (hot gas) can be conducted through the heat transfer tube groups 114, 114.
[0017]
Here, the heat transfer tube 114 is configured by a heat transfer tube main body 134 formed of a flat tube and a heat transfer fin 136 formed of a corrugated plate connecting between opposing surfaces in the longitudinal direction of the heat transfer tube main body 134. Here, the corrugated plate 136 has a rectangular wave shape in the illustrated example, but may have a triangular mountain wave shape, a trapezoidal mountain wave shape, or a semicircular wave shape.
[0018]
In addition, the inlet / outlet nozzles 130 and 132 are provided above and below the rectangular tube body 116 so that the second fluid (cooling water) can be conducted to the outside of the heat transfer tube 114.
[0019]
As shown in FIG. 5 (corresponding to the portion 4 (5) -4 (5) in FIG. 3), the body can be a cylindrical body 116A. As described above, the number of types of parts can be reduced. That is, when it is cylindrical, it is necessary to prepare 114, 114 ', 114''having different widths as heat transfer tubes as shown in the figure.
[0020]
In addition, as described above, the heat transfer tube is configured so that the heat transfer tube main body 134A and the heat transfer fins are opposed to each other as shown in FIGS. 6 (a) and 6 (b) even if the heat transfer tube main body and the heat transfer fin are not separate. The heat transfer tubes 114A and 114B may be formed by projecting from both or from one side to form a large number of heat transfer fins 136A and 136B.
[0021]
When the heat transfer fins 136A and 136B are protruded from both sides, it is not always necessary to join the heat transfer fins 136A and 136B. Instead, the heat transfer fins 136A and 136B may protrude alternately as shown in FIG. 6 (b). May be. Further, when protruding from one side, it is usually brought into contact with the other facing surface, but may be separated from the viewpoint of formability.
[0022]
These heat transfer tubes are sequentially formed from a single metal pipe by multi-stage pressing or, although not shown, from a single plate material (hoop material) by pressing or roll forming.
[0023]
Further, each heat transfer tube may be a square pipe or a conventional round pipe as shown in the figure, even if the outer cross section is not a flat cross section. The square pipe is desirable because it is easier to insert and fix the band plate provided with the protrusion when forming the protrusion described later.
[0024]
In these cases, it is only necessary to fix a thin strip plate in which a projection plate or a protrusion is formed at a predetermined pitch in the pipe in the same manner as in the case of the heat transfer fin described above.
[0025]
In the above configuration, in the present embodiment, the protrusions 140 are formed at predetermined intervals in the longitudinal direction (flow direction) on the wall surface of the divided flow path 137 formed by the heat transfer tube main body 134 and the heat transfer fins 136. Form (see FIG. 7).
[0026]
Here, for convenience of explanation, FIG. 7 shows a model in which the divided flow path has a rectangular cross section (square), and the protrusions 140 are plate-shaped and arranged at predetermined intervals.
[0027]
The protrusion 140 is usually plate-shaped, but may be a knob (hemispherical, pyramidal, prismatic). In the case of a plate shape, it is formed by cutting and raising, and in the case of a knob shape, it is formed by stamping or the like. Cutting and stamping are categories of press working. In the case of a plate shape, it is generally rectangular as shown in the figure, but the planar shape is arbitrary, such as trapezoidal, triangular shape 140B (FIG. 8 (b)), semicircular shape, etc. As shown in a), a pair of 140A and 14OA may be arranged in the shape of an arrow (counter). That is, it is optional if vortex is generated in the flow of high-temperature gas or the like (gas turbulence is generated) and contributes to improvement of the heat transfer rate (heat exchange efficiency).
[0028]
Further, in the illustrated example, the protrusion 140 may be a side surface as well as the groove bottom side of the corrugated plate, but is subject to processing limitations. Usually, the protrusion 140 is formed by cutting and raising from the wave bottom side of the corrugated plate.
[0029]
And, when the projection is a rectangular plate shape (projection plate), the shape characteristics ((1) inclination angle, (2) angle of attack, (3) height, (4) pitch) of the projection plate are within the following ranges respectively. It has been confirmed by an experimental simulation that the heat transfer rate is improved by the protrusions (see FIGS. 9 to 12).
[0030]
In addition, each form element is shown in FIG. 7 (a) projection plate attack angle α and projection pitch p, (b) projection plate inclination angle β and projection plate height h, (c) projection plate height h and flow path. The height H is shown respectively. The integral average heat transfer coefficient (on the entire peripheral wall surface) is as follows: inclination angle: 90 °, angle of attack: 45 °, channel shape: 4 mm × 4 mm × 220 mmL, protrusion shape: 1.5 mm × 1.5 mm × 0. The simulation was performed under the conditions of gas flow rate: 20 g / s and gas temperature: 400 °, with each form characteristic varied with 5 mmt as a reference. The heat transfer coefficient ratio (vertical axis) in each graph is displayed with 1.0 as the heat transfer coefficient when there is no protruding plate under the above conditions.
[0031]
The following can be understood from FIGS.
[0032]
(1) Fig. 9: Projection plate inclination angle is in the range of 30 to 90 °, and there is almost no effect on the heat transfer rate, so it may be about 90 ° from a manufacturing standpoint, but the heat transfer rate is slightly improved. If it is desired, the range is 45 to 75 °.
[0033]
(2) FIG. 10: The projection plate angle of attack is most preferably 45 °. That is, the smaller the angle of attack, the easier the vortex to occur, but the pressure loss (flow resistance) increases (because of the balance between vortex generation and pressure loss). Therefore, it can be appropriately determined in the range of 20 to 70 °, preferably 30 ° to 60 °, according to the characteristics of the fluid (flow velocity, viscosity, etc.) and the shape of the protruding plate. In addition, although the simulation result of the angle of attack does not indicate 45 ° or more, when it exceeds 45 °, it is estimated that the heat transfer coefficient gradually decreases in a symmetrical manner.
[0034]
(3) FIG. 11: The height of the protruding plate is 0.1 to 0.8, preferably 0.2 to 0.7, more preferably 0.4 to 0.6 of the flow path height. If it is too low, it is difficult for eddy currents to be generated, and if it is too high, the heat transfer coefficient is only slightly increased against the increase in flow resistance.
[0035]
(4) FIG. 12: The projection plate pitch is 1.0 to 2.0 times the flow path width, preferably about 1.5 times, when the cooling performance is considered first. If the protruding plate pitch is too long, the vortex flow is significantly attenuated, and it is difficult to effectively increase the cooling performance. However, when the protrusion plate pitch is short as described above, the pressure loss is increased. Therefore, the pitch is determined in terms of the balance between the cooling performance and the pressure loss. In the above (1) to (3), each numerical range is determined from the viewpoint of the balance between the cooling performance and the pressure loss.
[0036]
Furthermore, the present inventors have formed a protruding plate to form the flow path and the form of FIG. 8 (b) (only the protruding plate is changed to an inscribed triangle shape with respect to the above-described reference shape). Similarly, a simulation experiment was performed on the flow paths. As a result, the form of FIG. 8 (a) improves the heat transfer rate by about 35% with respect to the case without protrusions, and the form of FIG. 8 (b) has a heat transfer of about 53% with respect to cases without protrusions. It can be seen that the heat transfer rate (heat exchange rate: high-temperature gas cooling efficiency) is improved when the rate plate is improved and the protruding plate is clearly formed.
[0037]
Next, the manufacturing method of the heat exchanger of this embodiment is demonstrated.
[0038]
First, as shown in FIG. 13, a flat tube (a strip cross section in the illustrated example) 134 serving as a heat transfer tube main body, a metal corrugated plate 136 serving as a heat transfer fin, and an introduction side / discharge side holding plate (tube sheet). 118 and 120 are prepared. Here, the cross section of the flat tube 134 may be a rectangular tube shape or an oval shape. The corrugated plate 136 has a rectangular wave shape in the illustrated example, but may have a triangular mountain wave shape or a circular wave shape.
[0039]
The thicknesses of the flat tube (heat transfer tube main body) 134, the metal corrugated plate, and the introduction side / discharge side holding plate vary depending on the material used and the service life. For example, in the case of stainless steel, the former first party: 0.1 -1.0 mm (preferably 0.3-0.8 mm), former second: 0.01-0.8 mm (preferably 0.05-0.5 mm), latter: 0.5-3 mm (preferably 1 to 2 mm).
[0040]
The method for preparing the corrugated plate 136 is not particularly limited, and can be prepared by a conventional method. For example, drawing or corrugating molding (pressing) may be performed by rolling a gear-shaped punch on a corrugated die.
[0041]
When the corrugated plate 136 is manufactured (pressing), the protruding plate 140 can be simultaneously formed by pressing or the like, and the number of manufacturing steps of the corrugated plate is hardly increased as compared with the case where the protruding plate 140 is not formed.
[0042]
Next, after being inserted into the flat tube 134 with the brazing material attached to the top of each corrugated plate 136, the flat tube 134 is compression-molded to temporarily fix the corrugated plate 136, and then passed through the brazing heating furnace. A heat transfer tube 114 is prepared. In addition, since the introduction side end of the flat tube 134 (heat transfer tube 114) can adjust the brazing clearance and increase the brazing length, it can be flared to increase the joint strength to the introduction side holding plate 118. It is desirable to keep it.
[0043]
Next, the heat transfer tube unit 138 is prepared by inserting and joining the heat transfer tubes 114 in the above embodiment into the heat transfer tube holding holes 118 a and 120 a formed in the insertion side / discharge side holding plates 118 and 120. The form of joining at this time is usually a brazing theory. At this time, for example, when the heat exchanger is made of stainless steel, copper brazing or nickel brazing is usually used. The heating and cooling conditions during brazing are set in consideration of the type of brazing material and the heat capacity.
[0044]
After the brazing material is applied to the outer periphery of the introduction side / discharge side holding plates 118 and 120 of the heat transfer tube unit 138 thus prepared, the pyramid cylinder that forms the rectifying unit 118 after being partially inserted into the rectangular cylinder 116 that forms the body On the other hand, introduction ports / discharge ports (connection pipes) 126 and 128, in which flanges 126a and 128a are integrated, are inserted on the small diameter side and joined (mainly fixed), respectively.
[0045]
These joining (main fixing) means are preferably TIG welding or laser welding which is easy to secure joining strength with little oxidation deterioration, but other arc welding, resistance welding, and further joining with a heat resistant adhesive. Also good.
[0046]
In the above, the body (outer tube) 116 can be halved and retrofitted. In this case, after the parts other than the body 116 are integrated by resistance welding / brazing or the like, the body 116 is integrated by resistance welding in a separate process. For this reason, although the number of manufacturing steps is increased, it is desirable that the problem of metal cracking based on the difference in the cooling efficiency between the surface side and the inner side after brazing is difficult to occur.
[0047]
In the above description, a heat exchanger that performs heat exchange by passing high-speed high-temperature gas (gas) through a group of straight heat transfer tubes (inner tubes) and cooling water (liquid) through a body (outer tube) is taken as an example. The combination of the first fluid and the second fluid is arbitrary as long as there is a temperature difference capable of heat exchange. In addition, the exhaust gas of the automobile passed through the heat exchanger is usually gas flow rate: 0 to 50 m / s, and gas temperature: 120 to 700 ° C.
[0048]
However, it is usually desirable to select the first fluid (passing through the inner tube) and the second fluid (passing through the outer tube) based on the following criteria. (See Chemical Engineering Association, “Chemical Engineering Dictionary” (May 30, 1974) Maruzen, p. 365-366)
Fluid that should be passed through the inner pipe (pipe): Corrosive fluid, fluid with large dirt on the pipe wall, high-pressure fluid, and high-temperature fluid that requires special materials.
[0049]
Fluid to be passed through the outer tube (outside the tube): Fluid with a small flow rate, fluid with a large viscosity, fluid with a small allowable pressure loss.
[0050]
Moreover, even if the heat transfer tube group is bent (bent) in the middle, the present invention can also be applied to a tube bent in a U shape and having both ends positioned on the same side.
[0051]
Naturally, the present invention can be applied to all types of multi-tubular heat exchangers such as a heat exchanger in which a rectifying section (rectifying chamber) is provided only at one end and partitioned by a partition plate and the inlet / outlet port is on the same side. is there.
[Brief description of the drawings]
1 is a longitudinal sectional view showing an example of a conventional multi-tube heat exchanger. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1. FIG. 3 is a multi-tube type applied to an embodiment of the present invention. FIG. 4 is a longitudinal cross-sectional view showing an example of a heat exchanger. FIG. 4 is a cross-sectional view of one embodiment taken along the line 4 (5) -4 (5) in FIG. FIG. 7 is a cross-sectional view showing each form of an integrally formed heat transfer tube formed from a pipe material to which the present invention can be applied. FIG. 7 is a model diagram for explaining a heat transfer tube flow path formed with a projection plate and each form element of the projection plate. Model diagram to be displayed [Fig. 8] Model diagram showing examples of other arrangements of projection plate (a) and other shapes (b) [Fig. 9] Effect of projection plate inclination angle on heat transfer coefficient in simulation experiment FIG. 10 is a graph showing the influence of the angle of attack of the projection plate on the heat transfer coefficient. FIG. 11 is also the heat transfer coefficient. FIG. 12 is a graph showing the influence of the protrusion plate pitch on the heat transfer coefficient. FIG. 13 is a manufacturing process of the heat transfer tube unit in the multi-tube heat exchanger to which the present invention is applied. Figure [Explanation of symbols]
12, 112 Multi-tube heat exchangers 14, 114 Heat transfer tubes 16, 116 Outer tube (fuselage)
18, 118 Inlet side holding plate 20, 120 Discharge side holding plate 22, 122 Inlet side rectifying cylinder portion 24, 124 Discharge side rectifying cylinder portion 26, 126 Inlet (connection pipe)
28, 128 outlet (connection pipe)
134 Flat tube (heat transfer tube body)
136 Corrugated sheet (heat transfer fin)
137 Split channel (hot gas channel)
138 Heat Transfer Tube Unit 140 Projection (Projection Plate)

Claims (7)

An inner tube (heat transfer tube) group through which the first fluid passes and an outer tube (fuselage) through which the second fluid passes, and a plurality of heat transfer tube groups are connected to the first fluid introduction side and the first In the multi-tube heat exchanger that is arranged to be held by the introduction side / discharge side holding plate respectively positioned on the fluid discharge side,
The heat transfer tube is composed of a heat transfer tube main body having a flat cross section and a plurality of heat transfer fins connecting between the opposing surfaces in the longitudinal direction of the heat transfer tube main body or projecting from both or one of the opposing surfaces. Plate-like or knob-like protrusions are formed at predetermined intervals (predetermined pitches) in the longitudinal direction on the wall surfaces of the respective divided flow paths of the heat transfer tubes formed by the heat fins, and eddy currents can be generated in the first fluid. A multi-tube heat exchanger characterized by being made . Each of the heat transfer tubes has a configuration in which a heat transfer fin is formed by inserting and joining a corrugated plate separate from the heat transfer tube main body to a heat transfer tube main body formed of a flat tube, and cutting the wall surface of the heat transfer fin. The multi-tubular heat exchanger according to claim 1, wherein the plate-like or knob-like protrusion is formed by stamping. The multitubular heat exchanger according to claim 1 or 2, wherein the protrusion is plate-shaped and the angle of attack is 20 to 80 °. The multi-tube according to claim 1, 2 or 3, wherein the protrusion is plate-shaped and the height and width thereof are 0.1 to 0.8 times the height of the flow path and the width of the flow path, respectively. Type heat exchanger. The multi-tube heat exchanger according to any one of claims 1 to 4, wherein the protrusions are plate-like and the flow direction pitch is 1 to 5 times the flow path height or flow path width. . The multitubular heat exchanger according to any one of claims 1 to 5, wherein the protrusion is plate-shaped and the planar shape thereof is rectangular. A method of manufacturing a multi-tube heat exchanger according to any one of claims 2 to 6, wherein a corrugated plate separate from the heat transfer tube main body is inserted and joined to a heat transfer tube main body made of a flat tube. When producing each heat transfer tube by forming a heat fin, a multi-tube type using the corrugated plate formed with the plate-like or knob-like projections by cutting or raising a wall surface or stamping is used. Manufacturing method of heat exchanger.

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