EP1994349B1 - Heat transfer unit - Google Patents

Abstract

A heat transmission unit includes a channel conducting a coolant, and a channel conducting a fluid to be cooled. The two channels are separated from each other by a wall provided with ribs extending therefrom into at least one of the two channels. The channel conducting the fluid to be cooled includes a fluid inlet and a fluid outlet. The channel is separated by a partition wall, arranged in flow direction, into a first and a second partial channel having a first partial inlet for fluid and a second partial inlet for fluid, and a first partial outlet for fluid and a second partial outlet for fluid. At least the first partial inlet for fluid is adapted to be shut off by a first shut-off device.

Description

The invention relates to a heat transfer unit with a channel through which a coolant flows and a channel through which a fluid to be cooled flow, which are separated from one another by a wall, from which ribs extend in at least one of the two channels.

Such heat transfer units are used for example for exhaust gas cooling in an exhaust gas recirculation train in an internal combustion engine. The ribs usually protrude into the channel through which the fluid to be cooled flows. In this case, there are embodiments in which the ribs extend from the two opposite sides of the heat transfer unit into the channel, as well as cooling devices in which the ribs only extend from one side into the channel. The ribs may take on different shapes and either extend integrally along the main flow direction or be formed as a single ribs, here both pin and tubular as well as wing-shaped ribs are known.

The channel through which the coolant flows can be arranged both within the channel through which the fluid to be cooled and also surround it in cross section.

In internal combustion engines heat transfer units are used for example for air, exhaust or oil cooling. Thus, intercoolers serve to reduce the combustion temperatures and thus the resulting nitrogen oxides and exhaust gas cooler for heating the air for faster heating of a passenger compartment or in the exhaust system to reduce the exhaust gas temperature of a gas flowing to a catalyst. In exhaust gas recirculation lines are using the exhaust gas cooler the exhaust gas temperatures and thus the combustion temperature in the engine lowered, which in turn pollutant emissions can be reduced. In each case serve as a coolant, the cooling water of the internal combustion engine.

A heat transfer unit, which is arranged in an exhaust gas recirculation system of an internal combustion engine is, for example, from DE 10 2004 019 554 A1 known. This consists of an inner U-shaped flowed through by exhaust gas channel, which is surrounded over the entire cross-section of a coolant flow channel. This is a multi-part die-cast cooler, which has different graduation levels.

In such heat exchangers, both a high efficiency with respect to the heat to be transferred and the lowest possible sooting are desired. At the same time, the pressure loss over the heat transfer units should be kept as low as possible.

From the JP 60-050225 a charge air cooler is known in which the flow through the radiator can be changed via two flaps. With open flaps, this cooler is flowed through over its entire cross-section in one direction, while with the flaps closed, only the third cross-section is traversed over the third section.

The known heat transfer units, however, have only low cooling capacities and cooler efficiencies, in particular at low throughputs and temperature differences. However, especially in the field of exhaust gas recirculation, it may be desirable to further reduce the pollutant emissions to achieve a high cooling capacity at low pressure loss, both at high and at low flow rates.

It is therefore the object of the invention to provide a heat transfer unit with high cooling capacities over a large throughput and temperature range Efficiencies can be achieved and at the same time the pressure loss is kept as low as possible.

This object is achieved by the characterizing part of the main claim.
This results in a two-stage heat transfer unit, which at low throughputs and relatively low temperature differences to the coolant still achieves a high cooling capacity or a high radiator efficiency, since a high flow rate is achieved by the radiator through the reduced flow-through cross-section. Such a construction reduces the required axial extent of the heat transfer unit, so that it can be built smaller.

Preferably, two shut-off devices are arranged in the heat transfer unit, wherein when the first fluid part inlet is closed by means of the first shut-off device, the second shut-off device is connected such that the cooling path for the fluid in the heat transfer unit lengthens. This means that the shut-off devices are arranged such that the heat transfer unit is flowed through in part by the second barrier in the opposite direction. This leads to a further extension of the effective cooling section and thus to a further increase in efficiency at low flow rates and temperatures, while with open shut-off device compared to known coolers equally good efficiencies are achieved with low pressure drop.

In a further embodiment, the heat transfer unit has two partitions, which cooperate with the shut-off devices in such a way that the entire channel flows through in both switching positions of the shut-off devices, wherein the cooling section extends when the cross-section narrows. It is thus used the entire available cross section of the heat transfer unit in both switching positions of the shut-off, which in turn leads to an increase in efficiency.

In this case, the cooling section preferably extends substantially to the same extent as the cross section through which it flows decreases. This means that when halving the flow-through cross section, the cooling section is doubled. This can be achieved by using the entire heat transfer unit in both switching positions of the shut-off devices and by multiple deflection.

The use of the entire available heat transfer surface in both switching positions of the shut-off to increase the efficiency is achieved in particular by a heat transfer unit, wherein the first partition from the fluid inlet between the first and second fluid part inlet in the main flow direction in the heat transfer unit to the opposite to the fluid inlet End extends and the second partition extends from the fluid outlet between the first and the second Fluidteilauslass in the main flow direction in the heat transfer unit to the fluid outlet opposite end, wherein the first and the second shut-off device are designed as a flap and the flaps at the opposite ends of the heat transfer unit are each arranged between the first and the second partition wall, wherein the flaps are arranged perpendicular to each other in both switching positions. With such a design, a cooler is formed, in which the flow-through cross-section is halved when the first fluid inlet is closed, at the same time the cooling section is doubled. When the first flap is closed, the fluid to be cooled is thus flowed through the narrowed cross section into the heat transfer unit behind the first partition due to the closed position of the second shut-off device deflected by 180 °, behind the central wall in turn deflected by 180 °, which again performed behind the second partition becomes. Only here can the exhaust gas flow out.

Alternatively, the first partition wall extends in a U-shape from the fluid inlet between the first and second fluid part inlet in the main flow direction to the second fluid part outlet and the second partition wall extends U-shaped from the fluid outlet between the first and second fluid part outlet in the main flow direction to the first fluid part inlet , wherein the first and the second shut-off device are designed as a flap, wherein the first flap through the first Fluid part inlet is closed and closed by the second flap of the second Fluidteilauslass, the flaps open and close parallel to each other. By means of such an arrangement, the flow-through cross-section is divided by three when the first fluid part inlet is closed, and at the same time the cooling section is tripled so that a very good cooling effect is achieved with even lower throughputs or fluid mass flows due to the long existing cooling section and the small cross section. At the same time, with the first fluid part inlet open, the pressure loss across the cooler can be kept low.

Particularly when such a heat transfer unit is used in an internal combustion engine for exhaust gas cooling, high radiator efficiencies are achieved independently of the throughput or existing temperature range of the exhaust gas or fluid flowing through the heat transfer unit. At high existing throughputs and high temperatures, a high cooling capacity can be ensured with low pressure losses. It thus increases the working range of such a cooler.

• Figur 1 zeigt eine Draufsicht einer ersten Ausführung einer erfindungsgemäßen Wärmeübertragungseinheit in geschnittener Darstellung.
• Figur 2 zeigt einen Schnitt durch die Wärmeübertragungseinheit gemäß der Fig.1 entlang der Linie A-A
• Figur 3 zeigt eine Draufsicht einer alternativen erfindungsgemäßen Wärmeübertragungseinheit.
• Figur 4 zeigt eine weitere alternative Ausführung einer erfindungsgemäßen Wärmeübertragungseinheit wiederum in Draufsicht und geschnittener Darstellung.

In the figures, three alternative embodiments of heat transfer units according to the invention are shown and will be described below.

• FIG. 1 shows a plan view of a first embodiment of a heat transfer unit according to the invention in a sectional view.
• FIG. 2 shows a section through the heat transfer unit according to the Fig.1 along the line AA
• FIG. 3 shows a plan view of an alternative heat transfer unit according to the invention.
• FIG. 4 shows a further alternative embodiment of a heat transfer unit according to the invention again in plan view and a sectional view.

For functionally identical components of the various embodiments of the heat transfer units according to the invention, the same reference numerals are used below.

In the Figures 1 and 2 a first embodiment of a heat transfer unit 1 according to the invention is shown which is preferably used as exhaust gas heat exchanger in motor vehicles. It consists of an outer housing 2, in which an inner housing 3, which can be produced, for example, by die-casting, is arranged. Between the inner housing 3 and the outer housing 2, a channel 4 flows through the fluid to be cooled after assembly. In the interior of the inner housing 3, a coolant through-flow channel 5 is arranged, the inlet and outlet nozzles 6, 7 in FIG. 2 are shown and which are arranged in the present embodiment at one to a fluid inlet 8 and a fluid outlet 9 opposite end 10 of the heat transfer unit. The coolant flowed through channel 5 is limited by a circumferential wall 11 in the wall, from which ribs 12 extend in the flowed through by the fluid to be cooled channel 4. The channel 4 through which the fluid to be cooled flows is designed such that its fluid inlet 8 is arranged on the same side of the head as the fluid outlet 9, so that the fluid to be cooled is deflected by 180 ° at the opposite end 10. Accordingly, the ribs 12 are arranged in this region following the main flow direction.

In order to achieve such a U-shaped flow, it is necessary to provide between the fluid inlet 8 and the fluid outlet 9 a in the flow direction in the flowed through by the fluid to be cooled channel 4 wall 13, which at a distance from the inlet 8 opposite end 10 of the heat transfer unit 1 ends, which corresponds approximately to the width of the fluid inlet 8 and the fluid outlet 9, so that no flow losses occur, but only a direction reversal of the fluid takes place at this end 10. This wall 13 is designed in height so that it extends to the outer housing 2, whereby a cross flow and an overflow is prevented directly from the inlet 8 to Ausiass 9.

As in particular in FIG. 1 can be seen, the ribs 12 are seen in the main flow direction, arranged in rows next to each other, with completion of a first row each followed by a second row, the ribs 12 are arranged offset from the ribs 12 of the first row. Such an arrangement of the ribs 12 increases the residence time of the fluid in the heat transfer unit and thus its efficiency, since a straight, obstacle-free flow is no longer possible for the fluid to be cooled.

According to the invention, the heat transfer unit additionally has a first partition wall 14, which extends in a U-shape from the fluid inlet 8 via the end 10 to the fluid outlet 9. This partition wall 14 divides in the present embodiment, the channel 4 in two sub-channels 15 and 16 and thus the fluid inlet 8 and the fluid outlet 9 in two approximately equal fluid part inlets 17, 18 and two fluid part outlets 19, 20. The first fluid part inlet 17 is of a Shut-off device 21 dominated in the form of a flap whose axis of rotation 22 is arranged in the present embodiment in extension to the outer housing 2. Of course, both the shut-off device 21 and the partition wall 14 extend over the entire height of the heat transfer unit 1.

When using such a heat transfer unit 1 as an exhaust gas cooler, an exhaust gas recirculation valve is usually formed before the heat transfer unit 1, so that different fluid mass flows or exhaust gas mass flows of the heat transfer unit 1 are supplied. Especially at low exhaust gas mass flows and smaller temperature differences between the exhaust gas and the coolant, the cooling capacity of a heat transfer unit without partition 14 and shut-off device 21 is only very small. In the present embodiment of the heat transfer unit 1 according to the invention, the first fluid inlet 17 is closed by the shut-off device 21, so that the entire mass flow flows via the second fluid inlet 18 to the second fluid outlet 20. This is compared to a heat transfer unit 1 without disconnectable channel only half the cross-section available. Although this results in somewhat higher pressure losses, which are smaller due to the low throughput than when the shut-off device 21 is open and the throughput is full. Furthermore, the Cooling capacity and thus the efficiency of the heat transfer unit 1 compared to known designs with low throughput and reduced cross-section significantly increased. With a correspondingly large fluid mass flow, the shut-off device 21 is opened, so that the entire cross-section of the channel 4 is available for cooling, so that no excessive pressure losses occur and at the same time the known good cooling effect is achieved.

A further embodiment of this is in the FIG. 3 shown. Compared to the first embodiment, in this heat transfer unit 1, two partition walls 23 and 24 are arranged, of which the first partition wall 23 extends from the fluid inlet 8 to the opposite end 10 of the heat transfer unit 1 and the second partition wall 24 extends from the fluid outlet 9 to the opposite end 10 of the heat transfer unit 1 extends. Both partitions 23, 24 terminate at a sufficient distance from the end 10, so that when closing one of the fluid part inlets 17, 18 a sufficient cross-section for the flow of fluid behind the ends of the partition walls 23 and 24 and the outer housing 2 is available.

Between the respective ends of the two partitions 23, 24 in extension to the wall 13 are axes of rotation 25, 26 are arranged, on each of which a shut-off device in the form of a flap 27, 28 is mounted. The width of the flaps 27, 28 corresponds to the distance between the two partitions 23, 24. At the same time corresponds to the distance of the end of the wall 13 of the axes of rotation 25, 26 each half the width of such a flap 27, 28, so that the first flap 27 in its first position, the first fluid part inlet 17 and the first Fluidteilauslass 19 shuts off, while the second flap 28 is disposed in its first end position offset by 90 ° to the first flap 27 and thus rests in its width with one end against the wall 13 and abuts against the outer housing 2 with its other end. In its second position, the first flap 27 abuts with its two ends against the partitions 23 and 24.

is now the first shut-off device 27 in a position in which it rests against the two partitions 23, 24, the first fluid part inlet 17 is closed. The fluid mass flow thus enters via the second fluid part inlet 18 in the sub-channel 16 and from here to the opposite end 10 of the heat transfer unit 1. The second shut-off device 28 prevents now by their above-mentioned first position a fluid mass flow over the extension of the wall 13 addition. Consequently, the fluid mass flow undergoes a 180 ° turn and passes behind the dividing wall 23 into the partial passage 15, but flows through it in the opposite direction, ie in the direction of the first fluid inlet inlet 10. An outflow is prevented here by the closed position of the first shut-off device 27, so that again a reversal of the fluid mass flow in the region of the first sub-channel 15 behind the first Fluidteilauslass 19, so again the usual flow direction compared to the first embodiment or the opposite position of the Flaps 27, 28 is changed. The fluid now flows again to the opposite end 10, where again a reversal takes place in the direction of the second fluid part outlet 20, where the fluid can flow out.

Thus, with this position of the flaps 27, 28, there is a doubling of the total flow path that has been covered in the event of halving the available flow cross-section. As a result, the cooling effect is significantly increased because in each state, the entire available heat exchanger surface is used.

In the opposite position of the two shut-off devices 27, 28 is thus the outer surface of the first flap 27 in extension to the wall 13, so that both fluid part inlets 17, 18 are opened. Thus, the fluid flows from the fluid inlet 8 in both sub-channels 15, 16. The second flap 28 prevents flow from the sub-channel 15 to the sub-channel 16, so that both sub-channels 15, 16 are flowed through in a U-shaped and parallel. From the first fluid part inlet 17, the flow thus takes place to the first fluid part outlet 19 and from the second fluid part inlet 18 the fluid flows to the second fluid part outlet 20. Such a switching position is selected at high mass flow rates.

FIG. 4 shows a further alternative heat transfer unit 1 in which again two partitions 29, 30 and two shut-off devices 31, 32 are used.

However, here runs the first partition wall 29 from the fluid inlet 8 U-shaped to the fluid outlet 9 and ends at a distance in front of the fluid outlet 9, which corresponds to half the width of the shut-32. However, parallel to the U-shaped second partition wall 30 extends from the fluid outlet 9 in the direction of the fluid inlet 8 where it in turn ends at a distance from the fluid inlet 8, which corresponds to half the width of the shut-off device 31. These two partitions 29, 30 are arranged so that the fluid inlet 8 and the fluid outlet 9 are approximately divided in their cross-section and in their width.

The shut-off devices 31, 32 are arranged on axes of rotation 33, 34, which are arranged in extension to the ends of the partitions 29, 30 in the region of the fluid part inlets 17, 18 or fluid part outlets 19, 20.

In the closed position of the two flaps 31, 32 so when the flap 31 on the partition wall 29 and the wall 13 and concerns the flap 32 on the partition wall 30 and the outer housing 2, the fluid mass flow passes through the second fluid part inlet 18 into the heat exchanger unit 1 and flows between the outer housing 2 and the first partition wall 29 U-shaped until the second shut-off device 32, where it is deflected behind the first partition wall 29 and now again in the opposite direction U-shaped in the direction of the first fluid part inlet 17 between the partitions 29 and 30 flows. When the first fluid part inlet 17 is reached, the path through the shut-off device 31 is blocked again so that a reversal takes place behind the dividing wall 30 and the fluid mass flow now flows between the wall 13 and the dividing wall 30 in a U-shaped direction toward the free first fluid part outlet 19. This results in a tripling of the cooling section at the third of the available cross-section.

With the shut-off devices 31, 32 open, that is to say when the flap extension extends in the direction of the dividing walls 29, 30, the usual fluid mass flow is U-shaped through the entire cross section from the fluid inlet 8 to the fluid outlet 9, reliably avoiding excessive pressure losses at high throughputs.

It should be clear that such an embodiment is not limited to the existing embodiments, but the design of the radiator is largely arbitrary. Thus, it would of course also be possible to arrange the fluid inlet and the fluid outlet at opposite ends of the heat transfer unit. Of course, a flow around the heat transfer unit with coolant instead of the internal flow is conceivable. Essential is the possibility to shut off a part of the available cross-sectional area, wherein as possible nevertheless the entire available heat exchanger surface should be used. As shut-off devices both flaps and other elements can be used. It should also be clear that a heat transfer unit is not limited to a heat transfer unit to be produced by die casting, but such heat transfer units which can be switched in their cross section can also be used in heat transfer units of a different design.

The illustrated embodiments of the heat transfer unit allow use with very good cooling performance and cooler efficiencies over a wide range of throughput and temperature. At the same time, the pressure loss across the cooler is kept as small as possible.

Claims (6)

1. A heat transmission unit comprising a channel (5) conducting a coolant, and a channel (4) conducting a fluid to be cooled, said two channels (4,5) being separated from each other by a wall (11) provided with ribs (12) extending therefrom into at least one of said two channels (4,5), wherein said channel (4) conducting the fluid to be cooled comprises a fluid inlet (8) and a fluid outlet (9) and the heat transmission unit (1) further comprises a wall (13) separating the fluid inlet (8) from the fluid outlet (9) and extending to a position before an end (10) of the heat transmission unit (1) opposite to the fluid inlet (8) and respectively the fluid outlet (9),
   characterized in that
   said channel (4) is separated by a partition wall (14;23,24;29,30) arranged in flow direction, into a first and a second partial channel (15,16) having a first partial inlet (17) for fluid and a second partial inlet (18) for fluid as well as a first partial outlet (19) for fluid and a second partial outlet (20) for fluid, at least said first partial inlet (17) for fluid being adapted to be shut off by a first shut-off means (21;27;31) so that, in the opened condition of said first shut-off means (21;27;31), the heat transmission unit (1) is conducting a U-shaped flow and, in the closed condition of said first shut-off means (21;27;31), the heat transmission unit (1) is at least partially conducting a U-shaped flow.
2. The heat transmission unit of claim 1, wherein the heat transmission unit (1) is provided with two shut-off means (27,28;31,32) arranged internally thereof and wherein, in the closed condition of the first partial inlet (17) for fluid as effected by the first shut-off means (27;31), the second shut-off means (28;32) is switched in such a manner that the cooling path for the fluid in the heat transmission unit (1) is lengthened.
3. The heat transmission unit of claim 2, wherein the heat transmission unit (1) comprises two partition walls (23,24;29,30) cooperating with the shut-off means (27,28;31,32) in such a manner that the whole channel (4) is in its flow-conducting state in both switch positions of the shut-off means (27,28;31,32), the cooling path being lengthened and the cross section being narrowed.
4. The heat transmission unit of claim 3, wherein the cooling path is lengthened substantially to the same extent to which the flow-conducting cross section is reduced.
5. The heat transmission unit of claim 3 or 4, wherein the first partition wall (23) extends, in the main flow direction and between the first and second partial inlets (17,18) for fluid, from the fluid inlet (8) into the heat transmission unit (1) to a position before the end (10) opposite to the fluid inlet (8), and the second partition wall (24) extends, in the main flow direction and between the first and second partial outlets (19,20) for fluid, from the fluid outlet (9) into the heat transmission unit (1) to a position before the end (10) opposite to the fluid outlet (9), wherein the first and second shut-off means (27,28) are formed as flaps and the flaps (27,28) are arranged on the opposite ends of the heat transmission unit (1) respectively between the first and second partition walls (23,24), the flaps (27,28) being arranged vertically relative to each other in both switch directions.
6. The heat transmission unit of claim 3 or 4, wherein the first partition wall (29) extends, in the main flow direction and between the first and second partial inlets (17,18) for fluid, along a U-shaped path from the fluid inlet (8) to a position before the second partial outlet (20) for fluid, and the second partition wall (30) extends, in the main flow direction, along a U-shaped path from the fluid outlet (9) between the first and second partial outlets (19,20) for fluid, all the way to a position before the first partial inlet (17) for fluid, wherein the first and second shut-off means (31,32) are formed as flaps, the first flap (31) being adapted to close the first partial inlet (17) for fluid and the second flap (32) being adapted to close the second partial outlet (20) for fluid, and the processes of opening and closing the flaps (31,32) being performed in parallel to each other.

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