JPH11108578A - Egr gas cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculating(EGR) gas cooler using a heat conductive pipe where the cause of the bad conditions of an engine is removed beforehand by providing a projection within the heat conductive face, and increasing the disorder of the flow thereby raising the heat conductivity. SOLUTION: This is an EGR gas cooler where a group of heat conductive pipes consisting of plural pipes are fixed and arranged at a tube sheet 3, and the pipes are set and supported in the through holes of a supporting plate 5 whose periphery is fixed at plural places to the inwall of a drum pipe 1, and end caps which have an inflow port 8 and an outflow port 9 for EGR gas are fixed to outside of both ends of the drum pipe, and the drum pipe of which is provided with cooling medium inflow and outflow ports, and the heat conductive pipe has at least one spiral rib within, and this rib is processed from outside of the heat conductive pipe, and further a plate-shaped fin made of a band- shaped plate or a corrugated plate is inserted into the heat conductive pipe to touch internally the rib, or the plate-shaped fin is made, being twisted in the opposite direction to the spiral direction of at least one spiral rib of the heat conductive pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to cooling water for an engine,
It is applied to a device for cooling EGR gas with a refrigerant for a car air conditioner or cooling air, and more specifically, to prevent particulate components such as soot contained in exhaust gas from adhering to the inner peripheral surface of a heat transfer tube, or The present invention relates to an EGR gas cooling device using a heat transfer tube having improved heat transfer performance even if the heat transfer tube adheres.

[0002]

2. Description of the Related Art A method of extracting a part of exhaust gas from an exhaust gas system, returning the exhaust gas to an intake system of an engine again, and adding it to an air-fuel mixture is based on an EGR (Exhaust Gas Recircucu).
ration: exhaust gas recirculation). EGR is NO
x generation suppression, pump loss reduction, heat radiation loss to coolant due to lowering of combustion gas temperature, increase in specific heat ratio due to changes in working gas amount and composition, and improvement in cycle efficiency accompanying this. Because of its effectiveness, it is considered an effective way to improve the thermal efficiency of the engine. However, when the temperature of the EGR gas increases, the durability of the EGR valve and the like deteriorates due to a decrease in fuel efficiency and a heat effect due to a rise in the intake air temperature, which may cause early damage, and a water cooling structure for preventing the damage may be provided. It is recognized that you need to.

In order to avoid such a situation, there has been proposed a device for cooling the EGR gas by means of a cooling liquid or cooling air for an engine, and a multi-tube heat exchanger is generally used as this device.

As a multi-tube type EGR gas cooling device used in this case, for example, a plurality of heat transfer tubes are fixedly arranged on a tube sheet fixed to the inner wall of the body tube at both ends of the body tube. EGR gas inlet and EG at the end
An R gas outlet is provided, and further, a cooling medium inlet and a cooling medium outlet are provided on the body tube itself by outward burring forming, and the cooling medium inlet and the cooling medium outlet provided by this burring forming are: There is an EGR gas cooling device having a structure in which branch pipes are directly joined by brazing or welding.

[0005]

However, in such a conventional heat transfer tube, the inner peripheral surface thereof is smooth over the entire length of the heat transfer tube in the longitudinal direction as in a normal heat exchanger. Since a simple circular pipe is used, the EGR gas flowing into the pipe flows smoothly with almost no flow resistance. As a result, the EGR gas is not stirred in the heat transfer pipe, and
The heat transfer from the GR gas to the heat transfer tube is not sufficient,
The cooling efficiency of the R gas had to be low. Also E
The soot as the exhaust gas composition is mixed in the GR gas,
In the process in which the EGR gas passes through the tube, the soot is likely to adhere to the inner peripheral surface of the tube, and the soot once adhered is less likely to be separated from the inner peripheral surface of the tube, and gradually grows. It becomes a lump of soot.

When soot adheres to the inner surface of the tube of the heat transfer tube in this way, the soot acts as a heat insulating material, and the heat transfer from the gas body, which is not so high even in a normal state, to the tube wall is further impeded. The desired heat exchange between the EGR gas and the cooling medium is not performed as desired, and the soot adhering to the inner peripheral surface of the tube gradually grows into a lump of soot, and the lump detaches due to vibration or the like. There is also a problem that the EGR gas flows into the circulation system and flows into the engine to cause malfunction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a projection is provided inside a heat transfer surface to positively increase turbulence of a flow to enhance the heat transfer performance of a tube. It is an object of the present invention to provide an EGR gas cooling device using a heat transfer tube in which a heat exchange rate is stable and a cause of engine malfunction is removed in advance.

[0008]

Means for Solving the Problems The present inventors have focused on the problems in the prior art, and have a configuration in which a spiral ridge is provided inside a heat transfer tube, and a plate-like fin is provided in the heat transfer tube. The present invention has been found that the heat transfer can be promoted by inserting and joining the spiral ridges, and that the soot mixed in the EGR gas is prevented from adhering to the inner peripheral surface of the heat transfer tube and growing. It was completed.

In order to achieve the above object, according to the present invention, a heat transfer tube group composed of a plurality of pipes is fixedly arranged on a tube sheet fixed to both ends of an inner wall of a body tube. An end cap provided with an inlet and an outlet for the EGR gas is fixed, and the body tube is provided with a cooling medium inlet and an outlet. The EGR gas cooling device, wherein the heat transfer tube has at least It is characterized by having one spiral ridge, wherein the at least one spiral ridge is processed from the outside of the heat transfer tube, and further has a band-like shape inside the heat transfer tube. A plate-like fin formed of a flat plate or a corrugated plate is inserted and inscribed in and joined to the ridge, and the plate-like fin is opposite to a spiral direction of at least one spiral ridge of the heat transfer tube. Twisted in the direction Is characterized in has been EGR gas cooling device. Characterized by

According to the present invention, at least one spirally projecting ridge is provided inside the heat transfer tube in order to improve the heat transfer by forcibly turbulating the flow of the EGR gas passing through the inside of the heat transfer tube. As a result, a swirl force is applied to the EGR gas which is about to flow linearly, and at the same time, a boundary film formed between the inner peripheral surface of the heat transfer tube and the EGR gas is broken down one after another by spiral ridges to reduce the size. However, the heat transfer coefficient of the film is increased, and at the same time, the occurrence of partial turbulence and the reduction of the adhesion of soot and the like can be promoted.

In order to further increase the turning energy, it is effective to insert a plate-like fin into the inside of the heat transfer tube and join it to the above-mentioned ridge. When the EGR gas passes through the gap between the heat transfer tube and the inner peripheral surface of the heat transfer tube at a high speed, the adhesion of soot and the like can be prevented, and the temperature efficiency can be greatly improved.

[0012]

FIG. 1 is a partially cutaway plan view showing an embodiment of an EGR gas cooling device according to the present invention, and FIG.
This is an example of a heat transfer tube used in an R gas cooling device, and is one example of a heat transfer tube in which one continuous ridge formed in a spiral shape with one winding direction formed on the inner peripheral surface. FIG. 3 is a cross-sectional view of the heat transfer tube of FIG. 2, and FIG. 4 illustrates another embodiment of the heat transfer tube used in the EGR gas cooling device, and has a spiral shape with one winding direction. FIG. 5 is a perspective view showing a part of a heat transfer tube provided with plate-like fins formed by twisting a band-like plate inside a tube body formed with a continuous ridge formed on the inner peripheral surface formed in FIG. FIG. 6 is a cross-sectional view of a heat transfer tube, FIG. 6 is a vertical cross-sectional view illustrating still another embodiment of the heat transfer tube, and FIG. 7 shows an embodiment of a plate-like fin according to the present invention. FIG. 3B is a perspective view showing a part of a plate-like fin in which a number of small holes are formed at intervals, and FIG. It is a perspective view of a portion of a plate-like fins form.

As shown in FIG. 1, in the multi-tube type EGR gas cooling apparatus according to the present invention, a plurality of heat transfer tubes 4 are fixedly arranged on a tube sheet 3 fixed to both ends of an inner wall of a body tube 1. Preferably, each heat transfer tube 4 constituting this heat transfer tube group
Are supported at a plurality of positions of the body tube 1 by fitting through through holes 6 of a support plate 5 whose outer peripheral portions are fixed to the inner wall of the body tube 1.
End caps 7 are secured to the outside of both ends of the EGR gas pipe. The end cap 7 is provided with an EGR gas inlet 8 and an EGR gas outlet 9. The body tube 1 has a cooling medium inlet 10 and a cooling medium inlet. A medium outlet 11 is provided, and a branch pipe 12 is connected to the cooling medium inlet 10 and the cooling medium outlet 11 by brazing or welding.

Here, a heat transfer tube used in the EGR gas cooling device will be described with reference to FIGS. FIG. 2, FIG.
The heat transfer tube 4 shown in FIG. 1 is formed with a spiral groove 4-1 having a winding direction in one direction by forming a groove on a tube outer peripheral surface by a grooved roller or the like to form a spiral groove on the tube inner peripheral surface. Are formed by protruding the continuous ridges 4-2 formed in the above.

The height (h) of the ridge 4-2 is preferably 3 to 10% of the inner diameter (d) of the tubular body, and when it is less than 3%, the EGR gas is swirled and the inner peripheral surface and the EGR gas are mixed. The effect of destroying the film formed between the gas and the gas is poor. On the other hand, if it exceeds 10%, there is not much difference in the above effects and the flow resistance of the EGR gas increases. Further, the pitch (p) of the ridges 4-2 in the pipe axis direction is the outer diameter (D) of the pipe.
It is preferable to be 1.5 to 4.0 D. If the value is less than 1.5 D, the flow resistance of the EGR gas is too large, and the EGR rate is lowered. On the other hand, if the value exceeds 4.0 D, the above-described effect is poor.

In the heat transfer tube 4 shown in FIGS. 4 and 5, as described above, the spiral continuous ridge 4-2 is formed on the inner peripheral surface.
Is formed by inserting a plate-like fin 4-3 formed by twisting a band-like plate into the inside of a tubular body formed with. Here, it is preferable that the maximum width of the plate-like fins 4-3 be substantially equal to the minimum inner diameter of the heat transfer tube 4 in consideration of the gas flow. The plate-like fins 4-3 are joined to the inner peripheral surface of the heat transfer tube 4 so as to prevent rattling due to vibration applied to the heat transfer tube 4. As a method of joining the plate-shaped fin 4-3 to the inner peripheral surface of the tube, a plate-shaped fin 4-3 formed in advance in a spiral shape is inserted into the tube, and the side edge portion of the plate-shaped fin is joined. A method of partially brazing the contact portion of the peripheral surface of the tube with the ridge 4-2 can be used.

The twist direction of the plate-like fins 4-3 may be the same as the spiral direction of the continuous ridges 4-2 when the fins 4-3 are inserted into the heat transfer tube, but are preferably opposite to each other. Fin 4
-3 torsional pitch (p ') is 1.5 times the outer diameter (D) of the tube.
It is preferable that the number be twice or more. EGR below 1.5D
This is because while rotating the gas, the effect of destroying the boundary film generated between the inner peripheral surface and the EGR gas is great, but the flow resistance of the EGR gas increases. On the other hand, the twist pitch (p ') of the plate-like fins 4-3 may be larger than the outer diameter (D) of the tubular body. More preferred.

FIG. 6 shows a heat transfer tube according to another embodiment of the present invention. In this embodiment, a plurality of continuous spiral ridges (three in FIG. 6) formed on the inner peripheral surface are shown. ) 4-
2, 4-2a and 4-2b, and FIG.
In this embodiment, a plate-like fin 4-3 is provided in the heat transfer tube 4, but the plate-like fin is not inserted and joined as shown in FIGS. The same effect as the example can be obtained.

The plate-like fin inserted into the heat transfer tube 4 is a plate-like fin 4 twisted as shown in FIG.
-3, for example, as shown in FIG.
A plate-like fin 4-3a formed by piercing a plurality of small holes 4-3a 'in a band-like plate having a width capable of being inserted into the belt-like plate;
As shown in FIG. 6, a plate-like fin 4-3b having bent pieces 4-3b 'formed by bending both sides of the strip in opposite directions so as to be inserted into the heat transfer tube 4 can be used. 7A and 7B, the side edges of the plate-like fins are similarly formed so as to prevent rattling due to vibration applied to the heat transfer tube 4 or the like. It can be joined to the portion of the ridge 4-2 on the inner peripheral surface of the tube by brazing or the like. FIG. 7 (A),
Each plate-like fin 4-3a in the embodiment shown in FIG.
4-3b can be formed by twisting as shown in FIG. 5, and when the plate-like fin of each of the above-described embodiments is made of iron, its surface may be plated with nickel or the like to improve corrosion resistance. preferable.

As described above, at least one spirally projecting ridge 4-2, 4-2a,
By providing the 4-2b, the swirling force is applied to the EGR gas which is about to flow linearly to forcibly generate turbulence, and at the same time, the EGR gas is generated between the inner peripheral surface of the heat transfer tube and the EGR gas. Spiral ridges destroy the film one after another to reduce it, increase the heat transfer coefficient of the film, reduce the adhesion of soot etc. at the same time as the occurrence of partial turbulence, and promote peeling Can be.

In order to further increase the swirling energy, plate-like fins 4-3, 4-3a and 4-3b are inserted into the inside of the heat transfer tube 4, and the ridges 4-2, 4-2a and 4-2b are inserted. The EGR gas passes at a high speed through the gap between the plate-shaped fin and the inner peripheral surface of the heat transfer tube due to the joining of the plate-shaped fins and the ridges of the heat transfer tube, thereby suppressing the adhesion of soot or the like. Even so, the soot immediately peels off in small pieces,
The heat transfer performance of the heat transfer tube 4 is stably maintained, soot is prevented from growing into a lump, and the heat of the EGR gas is transferred from the plate-like fins 4-3, 4-3a and 4-3b to the plate-like fins 4-3, 4-3a and 4-3b. The ridges 4-2, 4-2a, and 4-2b pass through the joints with the fins.
The heat is transferred to the outer surface of the heat transfer tube 4 via the heat transfer pipe, so that heat is transferred to the cooling medium to increase the amount of exchanged heat, and therefore, a great effect is obtained in improving temperature efficiency.

[0022]

As described above, the present invention has at least one continuous ridge formed in a spiral shape with the winding direction being one direction on the inner peripheral surface of the heat transfer tube. Since the heat transfer tube provided with plate-shaped fins was used, the heat transfer performance was enhanced by increasing the heat transfer area and the turbulence of the flow of the EGR gas. It is possible to provide an EGR gas cooling device that is stripped out of small pieces that do not grow and does not grow into a lump, thus improving the heat exchange rate and preventing engine troubles caused by soot and the like.

[Brief description of the drawings]

FIG. 1 is a partially broken plan view showing one embodiment of an EGR gas cooling device of the present invention.

FIG. 2 illustrates an example of a heat transfer tube used in the above EGR gas cooling device, in which a continuous ridge formed in a spiral shape with a winding direction being one direction is formed on an inner peripheral surface. It is a perspective view which shows a part of heat pipe.

FIG. 3 is a cross-sectional view of the heat transfer tube of FIG.

FIG. 4 illustrates another embodiment of the heat transfer tube used in the EGR gas cooling device, and is a tube body in which a continuous ridge formed in a spiral shape having one winding direction is formed on the inner peripheral surface. FIG. 4 is a perspective view showing a part of a heat transfer tube provided with plate-like fins formed by twisting a band-like plate inside the heat transfer tube.

FIG. 5 is a cross-sectional view of the heat transfer tube of FIG.

FIG. 6 is a vertical cross-sectional view illustrating still another embodiment of the heat transfer tube.

FIG. 7 shows an embodiment of a plate-like fin according to the present invention, in which (A) is a perspective view showing a part of a plate-like fin in which a number of small holes are formed in a band-like plate at intervals. (B) is a perspective view showing a part of a plate-like fin in which bent pieces are formed on both side ends of the band-like plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body tube 2 Inner wall 3 Tube sheet 4 Heat transfer tube 4-1 Spiral groove 4-2, 4-2a, 4-2b Spiral ridge 4-3, 4-3a, 4-3b Plate fin 5 Support plate 6 Through hole 7 End cap 8 EGR gas inflow 9 EGR gas outflow 10 Cooling medium inflow 11 Cooling medium outflow 12 Branch pipe h Height of ridge p, p 'Pitch d Inner diameter of pipe D pipe Body diameter

Claims (4)

[Claims] 1. A heat transfer tube group comprising a plurality of tubes is fixedly arranged on a tube sheet fixed to both ends of an inner wall of a body tube, and an inlet and an outlet of an EGR gas are provided outside the both ends of the body tube. An EGR gas cooling device having an end cap provided with a cooling medium inlet and an outlet provided in the body tube, wherein the heat transfer tube has at least one heat transfer tube therein.
An EGR gas cooling device comprising two spiral ridges. 2. The EGR gas cooling device according to claim 1, wherein the at least one spiral ridge is formed from outside the heat transfer tube. 3. The heat transfer tube according to claim 1, wherein a plate-like fin made of a band-like flat plate or a corrugated plate is inserted into the heat transfer tube, and the heat transfer tube is inscribed and joined to the ridge. EGR gas cooling device. 4. The E according to claim 3, wherein the plate-like fin is formed by being twisted in a direction opposite to a spiral direction of at least one spiral ridge of the heat transfer tube.
GR gas cooling device.