DE3508240A1 - Heat exchanger, in particular charge air cooler with optimised flow resistances for all heat-exchanging media - Google Patents

Abstract

Nowadays, many demands for the recooling of various media are being placed on the output side of internal combustion engines. The use of hydrodynamic outputs or hydrostatic outputs, but also the use of retarders, requires recooling of the hydraulic oil. However, in the operation of heat pumps and the drives of air conditioning units recooling of condensing and evaporating media is also necessary. The plant operator frequently requires of the motor manufacturer the recooling of various hydraulic circuits, but also of various media, in conjunction simultaneously with a compact design of the heat exchangers. The heat exchanger principle presented by the invention permits a plurality of recooling media to be simultaneously applied by taking account of an optimised overall cooler volume. The heat exchanger is designed as an obliquely divided block consisting of at least two cooling units. Division is performed in such a way that a constant flow resistance prevails in all regions for the medium to be cooled. Provided for the cooling medium in the heat exchanger are turbulence generators which decrease in the direction of flow as a function of the achievable effect (Fig. 1). <IMAGE>

Description

description

The invention relates to a heat exchanger, in particular a charge air cooler for supercharged internal combustion engines, consisting of at least one cooling element with an inlet and an outlet, the flow cross-sections of which are in the flow direction of those involved Cooling or heating media increase or decrease.

Heat exchangers on internal combustion engines serve as a recooling device for. B. for charge air, engine oil, cooling water and exhaust gas and are often permanently integrated into the engine.

Heat exchangers used today, both lamellar and tubular heat exchangers, are designed in such a way that that the heat exchange areas are equal, d. H. the same lengths and diameters of the fins or tubes given are. The consequence of this design for both exchanging media is that the flow resistance in the heat exchanger is constantly changing and thus the total pressure loss is higher than necessary and the heat exchange is less than possible. In terms of performance and volume, such heat exchangers are not optimally designed.

A heat exchanger of the generic type of the invention is known from DE-GM 19 26 029. Here is the Coolant guide designed in such a way that, by simple conversion, either cooling air or cooling water as Coolant can be used, so as to heat exchangers in vehicle and assembly construction with internal combustion engine drives to make it universally usable regardless of its type of cooling. Due to the decreasing flow cross-section of the charge air cooling elements is particularly taken into account that the pressure resistance of the gaseous medium Charge air in a flow tube - apart from its flow velocity and its viscosity - is essentially a function of temperature. so that by this measure the pressure loss in Air cooling element can be minimized.

On internal combustion engines in today's vehicle and aggregate construction, there are often related demands with the cooling system, which the known heat exchanger cannot do justice to. Of the Frequently used hydrodynamic or hydrostatic output requires a recooling of the hydraulic oil. This requirement also applies to the use of retarders.

There are also demands for recooling in vehicle construction when using heat pumps and Air conditioning systems that work with condensing and evaporating media.

With the known heat exchanger, only one medium can be cooled, so that in the areas of application described several different heat exchangers must be provided on the drive unit, which have a significant Take up space. The known

The heat exchanger is designed in such a way that almost a constant flow resistance prevails. A corresponding adjustment on the coolant side is against it not made.

It is the object of the present invention to provide a heat exchanger of the type mentioned in the introduction in a simple manner Way to improve to the effect that a reduction for both exchange media in the heat exchanger the total flow losses are given when the efficiency of the heat exchanger is increased.

According to the invention, this object is achieved in that the heat exchanger is designed as an obliquely divided block and has a geometric shape that has a constant flow resistance in all areas of the heat exchanger causes the medium to be cooled, such as that passed through the fins or tubes also for the cooling medium. A constant cross-section adjustment in the flow direction for that to be cooled The medium is directly related to the temperature reduction achieved. That becomes the fact Into account that the resistance of gases - depending on the speed and viscosity - im is essentially a function of temperature; d. H. the flow resistance of gaseous media also falls the temperature. Liquid media, on the other hand, have the opposite effect; d. H. the flow resistance increases with decreasing temperature.

For example, in a charge air cooler according to the inventive concept, the heat exchanger is diagonally divided, whereby the flow cross-sections steadily decrease from inlet to outlet, corresponding to the decreasing ones Charge air temperature. A reverse heat exchanger design, i. H. Enlargement of the flow cross-sections for the medium to be cooled in the flow direction, results according to the concept of the invention when it is acted upon with a liquid medium. This heat exchanger concept also allows recooling different media and also the combination of liquid and gaseous media under consideration the physical properties such as increased resistance for liquids with falling temperatures or decreasing resistance for gaseous media with falling temperatures.

In this way, this heat exchanger principle is suitable for a wide range of applications in both vehicle construction, the aggregate construction as well as, for example, the plant construction can be used. With technically simple This heat exchanger can be produced by means of a medium. Furthermore, this design offers the possibility of maintaining the aerodynamically favorable design of the exchange surfaces of the known heat exchanger further or several further media, depending on requirements or application, in the same heat exchanger cool or use their energy potential for heating or cooling. The dimensioning and arrangement the individual cooling elements of the heat exchanger can be used in the context of the invention as required be different.

The idea of the invention also provides for the resistance of the cooling medium over the entire surface of the To keep the heat exchanger constant. Flow-influencing measures ensure a constant level of resistance Reached over the entire heat exchanger surface. According to this proposal according to the invention the cooling medium is optimally used. For example, when using the cooling medium air it is achieved that Uniform heating takes place over the entire cross-section and thus the loss of power for the Cooling of the media concerned is a minimum.

In an embodiment of the invention it is provided that the heat exchanger consists of several obliquely divided Blocks. This arrangement has the advantage of a compact design of the heat exchanger and a simplified cooling air routing for the cooling medium air compared to several individually arranged Heat exchangers.

ίο The inventive idea according to claim 3 allows the heat exchanger with another medium, for example exhaust gas, lubricating oil, hydraulic oil, cooling water or to apply another gaseous or liquid medium. With this possibility, the Use cases with a simultaneous reduction in the number of variants, d. H. Reduction of different heat exchanger designs.

According to claim 4, the heat exchanger is particularly suitable for V-engines in which each row of cylinders of the V-engine is provided with its own charging device, for example an exhaust gas turbocharger. With this Concept, the combustion air can be fed to each cylinder bank separately and independently of one another will. This heat exchanger is also suitable for two-stage charging.

In claim 5, a special feature of the V-engines is taken into account. In V-engines, depending on the number of cylinders, the V-angle and the ignition interval, pressure fluctuations can occur in the charge air line, which can adversely affect the degree of delivery of individual cylinders. To avoid or reduce pressure fluctuations, this arrangement of the heat exchanger (charge air cooler) offers the option of establishing a connection between the two cooler parts in the middle of the heat exchanger in such a way that pressure equalization between the two air flows is achieved on the charge air side at all times. This transition replaces the additional connecting line between the intake manifolds of the two cylinder rows of the V-engine, which is customary today. When using this heat exchanger for two-stage charging, there is no need for this cross-connection between these cooling units.
When using the heat exchanger for recooling two gaseous media, e.g. B. charge air for a two-stage supercharged internal combustion engine with intercooling of the charge air, the charge air is fed into the heat exchanger, which has the shape of an obliquely divided block. With the charge air passed through the heat exchanger in countercurrent and the respectively decreasing cross-sections in the direction of flow, one follows the physical law of gases, which states that the flow resistance is essentially a function of temperature, ie it decreases with temperature. The different densities of the two charge air flows can also be taken into account in a simple form.

In an embodiment of the invention, the heat exchanger can also consist of a plurality of cooling units that are put together exist. Each unit is designed according to the principle of the invention, i. H. the flow resistance for the medium to be cooled is constant in all areas of the corresponding cooling unit. The heat exchanger can be acted upon with different media, likewise the flow method can be any one Cooling unit can be determined whether cross countercurrent or cross direct current and thus also the efficiency of each individual heat exchanger can be changed.

The heat exchanger can also consist of a combination of two diagonally divided cooling units be designed, which together form a heat exchanger. By acting on the heat exchanger by a liquid and gaseous medium, which flow through the heat exchanger in cocurrent achieves that the special physical properties of liquids and gases in this heat exchanger conception usable applied. This heat exchanger also offers advantages in terms of structural volume compared to single heat exchangers.

A heat exchanger consisting of a diagonally divided block with two cooling units that are independent are to be acted upon from each other, can also flow through two gaseous or two liquid media will. It is advantageous to lead them through the cooler using the countercurrent principle in order to reduce the physical Use properties, d. H. In the case of gaseous media, resistance decreases with falling temperature or in the case of liquids, increase in resistance with falling temperature. This inventive idea is of of particular importance for condensing and evaporating media, as the drag coefficients are in change very strongly and lead to considerable cross-sectional changes, which in turn give rise to opportunities to give meaningful combinations for optimal utilization.

The coolant guide is advantageously provided with different turbulence-stimulating means, which on on the coolant side cause an even resistance level across the entire width of the heat exchanger. the The arrangement is such that, depending on the achievable effect, the number of turbulence exciters in the direction of flow expediently decreases. This measure, which is simple in terms of production technology, is in particular important for coolant ducts in sheath design.

The heat exchanger concept on which the invention is based provides that the coolant guide also by finned tubes or fins known per se are formed, which are flowed through by coolant as a coolant. Here, the finned tubes z. B. pull through the heat exchanger in the form of a pipe coil or in a cross flow to the cooling channels. This configuration offers the advantage that, in addition to the guides for the cooling media, the coolant guide can be used as a cooling channel for a further medium in the case of air cooling, with one gaseous cooling medium the coolant conduction with turbulence-stimulating means in the in claim 9 proposed way is provided.

Further features of the invention emerge from the following description and the drawings, represent the embodiments of the invention schematically. It shows

Fig. 1 shows a charge air / water heat exchanger which works according to the modified cross-countercurrent principle,

Fig. 2 is a two-stage intercooler with the throughflow Kreuzgleich- and cross-counterflow; water is used as the cooling medium,

Fig. 3 is a charge-air / cooling-air heat exchanger in countercurrent flow, consisting of two cooling units,

Fig. 4 shows a heat exchanger the charge air / water, with a condenser unit in cross-cocurrent and another in the cross-counterflow,

Fig. 5 is a heat exchanger with the cooling medium and the air to be cooled media charge air and oil; the exchange media work according to the cross-flow principle,

Figure 6 is a heat exchanger which is provided for the media to be cooled charge air and exhaust gas and the cooling medium is air. working according to the cross flow.

Fig. 7 shows a heat exchanger, intended for two-stage supercharging with intermediate cooling, with the cooling medium is water and the medium to be cooled charge air.

The heat exchanger 1 shown in Fig. 1 shows a charge air cooler acted upon by cooling water in a modified cross-countercurrent, as it is particularly suitable for highly charged engines with higher temperature differences of the charge air between inlet and outlet. The medium to be cooled, charge air, enters the heat exchanger 1 and there it enters the inlet cross-section of the obliquely divided block 7, which tapers towards the opposite end of the cooler. In the reversal area 9 of the heat exchanger, which is shown in a simplified triangular shape, the cooling medium is diverted. The inlet cross section of the cooler part 8 is the same as the outlet cross section of the cooler part 7. The cooler unit 8 also tapers from the inlet to the outlet. The diagonal division causes a constant flow resistance for the charge air. The physical property of gaseous media is used, ie simplified, the flow resistance of gases decreases with decreasing temperature. The charge air therefore enters the largest radiator cross section 1 and exits the narrowest radiator cross section 2.

The principle shown can also be used for conventional, tightly ribbed tube coolers, with the Cooling medium, preferably cooling water, inside through the pipes and the charge air outside through the cooling fins of the Pipes flows.

In Fig. 2, the heat exchanger 2 is shown, which forms two cooling units 10, 11 divided at an angle. The picture shows the heat exchanger as a charge air cooler, consisting of the two cooling units 10, 11. The charge air flows through the cooler in countercurrent. This heat exchanger (charge air cooler) is particularly suitable for V engines. With an arrangement at a V angle, the otherwise usual connection line between the two rows of cylinders, which ensures pressure equalization, can be dispensed with if a connection between the two cooler parts is established in the heat exchanger in such a way that pressure equalization between the two air flows on the charge air side at all times , and thus between the two intake lines of the cylinder rows of the V-engine, is achieved, identified by 29 in FIG. 2. If this heat exchanger is used for two-stage charging, this cross-connection between the cooling unit 10 and 11 is omitted. The principle of the invention is limited to the charge air side, since the heat exchanger on the water side usually only leads to a slight change in temperature. As in FIG. 1, the charge air enters on the large cross-sectional area of the radiator of the corresponding radiator unit 10 or 11 and exits again on the opposite radiator side. The charge air and the cooling medium water flow through the cooler unit 10 in a modified cross-countercurrent, in the cooler unit 11, however, in a modified cross-countercurrent.

Fig. 3 illustrates a loaded with cooling air charge air cooler in countercurrent flow is also suitable for a two-stage supercharging with intermediate cooling. In this arrangement, the heat exchanger 3 consists of two individual heat exchangers joined together to form a unit, each consisting of the cooling units 12, 13 and

16, 17 exist. The medium to be cooled, air, enters the cooling unit 12 and 17, supplied independently of one another. The flow area narrows steadily towards the center of the heat exchanger up to the reversal areas 14,15; these are located next to one another at the ends of the individual cooling units in the middle of the heat exchanger 3. The flow cross-section in the reversal areas 13, 16 is almost constant. The charge air enters the cooling units 13 and 16 in a deflected manner and leaves the heat exchanger 3 at its narrowest flow cross-sections. The illustration also shows that the concept of the invention relates not only to a constant flow resistance for the medium to be cooled, but also provides measures for the coolant in order to achieve a uniform resistance level over the entire heat exchanger. This can be achieved, for example, by reducing turbulence-stimulating agents as the cooling air becomes more heated. These turbulence-stimulating means are shown in simplified form in FIG. 3 with the reference numeral 28.

FIG. 4 shows a variant of FIG. 3. The heat exchanger 4 is shown as a charge air cooler, which is recooled with water. B. Oil can be used. As an example of the multitude of variants that the idea of the invention contains, the right part of the heat exchanger 4, consisting of the cooling units 22, 23 and the reversing area 21, is designed according to the cross-counterflow, whereas the left half of the heat exchanger with the cooling units 18, 19 and the reversing area 20 is designed according to the cross direct current. These pressures cause the cooler to have different efficiencies with the same external dimensions. The invention can also be transferred to heat exchangers with heat exchange surfaces that differ from one another, ie the cooling units 18, 19 are not identical to the cooling units 22, 23.

In Fig. 5, a heat exchanger is shown in cross flow. According to the concept of the invention, which uses the physical properties of gaseous and liquid media and converts them into the heat exchanger design, the heat exchanger 5 is also divided at an angle. The cooling unit 24 expands in the flow direction for the medium to be cooled, oil, and brings about a reduction in resistance. In contrast, the cooling unit 25 is acted upon with charge air, for which the cross section narrows in the flow direction. The media to be cooled, charge air and oil, are conducted in cocurrent through the heat exchanger 5. The inclined division of the heat exchanger allows this application while at the same time taking into account the specific properties. In simple terms it can be said; for a liquid medium the resistance increases with falling temperature, whereas for gaseous media the resistance falls with decreasing temperature.

Fig. 6 shows the heat exchanger 6 in cross flow, which is acted upon by two gaseous media which flow through the cooler to each other on the countercurrent principle. The cooling unit 26 is flowed through by exhaust gas and the cooling unit 27 by charge air. For both media, the flow cross-section decreases with increasing cooling. The heat exchanger principle shown in FIG. 6 is advantageously used for better utilization of the engine's own heat, in which first charge air and then the exhaust gas are cooled. This version can also be used in connection with the use of internal combustion engines to drive heat pumps. In the case of condensing and evaporating media, the concept of the invention is of particular importance, as the flow resistance coefficients change to a great extent due to temperature and lead to considerable changes in cross-section, which in turn give the opportunity to make useful heat exchanger combinations.

Fig. 7 illustrates a heat exchanger, such as may be used for example for internal combustion engines with two-stage supercharging and intermediate cooling. The diagonally divided heat exchanger 30 forms the cooling units 31, 32. The illustration shows the heat exchanger 30 as a charge air cooler, consisting of the two cooling units 31, 32 connected in series. The unequal division of the cooling units 31, 32 illustrates the concept of the invention. The intermediate cooler 31, which is designed as a low-pressure stage, takes up more exchange area than the end cooler, which can also be referred to as a high-pressure stage. With an unequal division of the cooling units 31, 32 that is coordinated for the respective internal combustion engine, the different density, temperature and the different pressure of the charge air can be taken into account. The charge air enters on the large cross-sectional area of the cooling unit 31 and exits again on the opposite side. The charge air flow is then compressed in a separate charging device, not shown, and then reaches the largest cross-sectional area of the cooling unit 32 and leaves the heat exchanger on the opposite side. The charge air and the cooling medium water flow through the cooling unit 31 in a modified cross-countercurrent, in the cooling unit 32 in a modified cross-countercurrent. The charge air in the cooling units 31, 32, on the other hand, is passed through the heat exchanger in countercurrent.

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Claims (11)

Claims 1. Heat exchanger, in particular charge air cooler for supercharged internal combustion engines, consisting of at least one cooling unit with an inlet and an outlet, the flow cross-sections of which decrease in the flow direction of the cooling or heating media involved, characterized in that the heat exchanger is designed as an obliquely divided block with at least two cooling units and has a geometric shape such that an approximately constant flow resistance is given in all areas of the heat exchanger for the medium to be cooled or for the cooling medium guided through the fins or the tubes. 2. Heat exchanger according to claim 1, characterized in that the heat exchanger consists of several diagonally divided blocks. 3. Heat exchanger according to claim 1 or 2, characterized in that another in the heat exchanger Medium such as exhaust gas, lubricating oil, cooling water, cooling oil or the like. Can be recooled. 4. Heat exchanger according to one of claims 1 to 3, characterized in that the heat exchanger consists of two separate heat exchangers, divided into two cooling units (10, 11), which are preferably designed as parallel, countercurrent charge air coolers, as they are useful for V-engines, for internal combustion engines with two separate charging devices (Fig. 2). 5. Heat exchanger according to claim 4, characterized in that a connection is established between the cooling units (10, 11) (Fig. 2). 6. Heat exchanger according to one of claims 1 to 3, characterized in that the heat exchanger consists of two separate heat exchangers, each with divided blocks, which are preferably designed as a series-connected charge air cooler for two-stage charging, in which the charge air flows through the cooler in countercurrent to each other and the cross-section of the individual blocks is preferably adapted to the different densities of the charge air (FIG. 7). 7. Heat exchanger according to one of claims 1 to 3, characterized in that the heat exchanger consists of several slanted blocks joined together, each unit being separate to act on and operate from each other. 8. Heat exchanger according to one of claims 1 to 3, characterized in that the flow guide in the heat exchanger, consisting of joined, obliquely divided blocks, is designed for different media so that the media to be cooled flow through the heat exchanger in cocurrent to each other, while the cooling medium flows through the heat exchanger in a cross-current or cross-countercurrent manner in relation to the media to be cooled (Fig. 5). eo 9. Heat exchanger according to one of claims 1 to 3, characterized in that the flow guide in the heat exchanger, consisting of joined, obliquely divided blocks, is designed for different media so that the different media to be cooled flow through the heat exchanger in countercurrent to each other, while the Cooling medium flows through the heat exchanger in relation to the media to be cooled in a cross flow (Fig. 6). 10. Heat exchanger according to one of claims 1 to 7, characterized in that the coolant guide is provided with turbulence-stimulating means (28) which decrease in the flow direction with regard to the achievable effect (Fig. 3). 11. Heat exchanger according to claims 1 to 7, characterized in that the coolant duct is formed by well-known finned tubes as well as Lamel len, which is from the cooling liquid as Coolant are flowed through.