EP0445006B1 - Heat exchanger with circular flow - Google Patents

Description

The subject of this invention is an energy exchange structure according to the preamble of claim 1 and an automobile oil cooler comprising such a structure, the invention being particularly suitable for applications in oil cooling equipment of automobile engines in which high ratios - heat transfer / oil pressure drop - are desired.

The invention also relates to a method of manufacturing such an oil cooler.

With the development of lighter, more compact, high-speed, high-torque internal combustion engines, there is an increased need for more efficient means of oil cooling. Many car manufacturers have introduced into their basic concept of engine the need for oil cooling means in addition to that obtained by the conventional system of oil cooling circuits from foundry with the engine block. Some manufacturers have specified the use of oil coolers not integrated in the engine block and intended to cool an oil flow by means external to the engine block. A typical assembly consists of mounting the oil cooling system on the oil filter system. To meet the requirements of the automotive industry, such a cooling means must be compact, light and highly efficient in heat transfer without causing a drop in oil pressure. This is how the persistent need for lighter and more efficient heat transfer systems has led to the development of a multitude of new systems and new configurations in the manufacture of heat exchangers used in cooling systems. automotive oil.

Originally, heat transfer systems, external to the engine block, usually used as oil coolers in automotive applications included a continuous serpentine tube, with or without cooling fins, installed outside the engine, usually in the air stream in front of the radiator or in the latter's cooling radiator. Oil, such as engine oil, transmission oil or any other fluid, is sent into the tube to be cooled. Conventionally, a refrigerant passed over the tube, for example in a radiator using a refrigerant or in a separate element using air cooling, thus ensuring the exchange of energy in the tube between the hot oil and the coolant.

With the need for greater compactness, and as described, for example, in EP-A-0 208 957, the oil coolers were subsequently mounted on the engine, usually between the engine block and the oil filter. mounted externally to the engine; they cooled the oil coming in or leaving the filter using the fluid from the engine cooling system. These oil filter mounted coolers generally included multiple hollow plate structures spaced apart from each other and generally parallel between which the oil and coolant flow in parallel planes to maximize heat transfer . Such spaced plate structures can be fitted with cooling fins between the hollow structures or are constructed of corrugated plates. In such devices, oil flows from an orifice located on or near the filter to the cooler and flows between the parallel plates of the cooler. The cooling agent coming from the engine cooling system circulates between and / or near the parallel plates containing the circulating oil, thereby transferring the heat energy from the oil to the cooling agent. There are a wide variety of realizations of this system, with the oil being first filtered and then sent to the cooling system or vice versa and, generally, with the coolant circulating in the engine cooling system, usually from the radiator or the water pump, to the oil cooling system.

One of the typical characteristics of oil coolers mounted on the filter is that one or both fluids circulate in a generally circular direction relative to the center of the cooler and, generally, the heat transfer elements of the fins and wavy surfaces, are generally not aligned in more than one or two directions. We have found that such a configuration of the fins or corrugated surfaces results in a loss of efficiency in the area of the heat transfer / oil pressure drop ratio in the heat exchanger.

We can therefore say that a problem still exists, in particular for optimizing the heat transfer / oil pressure drop ratio in the heat exchangers. With modern engines with increasing average revolutions per minute, added to high engine torque and decreasing response times, the need for a highly efficient oil cooling system with minimal effect on pressure engine lubrication system oil has become desirable.

One of the aims of this invention is to provide energy exchange structures having better heat transfer.

Another object of this invention is to provide energy exchange structures causing only a reduced drop in the internal pressure of the fluid.

Another object of the invention is to provide an automotive oil cooler with reduced internal oil pressure drop.

Yet another object of the invention is to propose a method of manufacturing energy exchange structures ensuring efficient heat transfer associated with a drop in internal pressure of the reduced fluid.

These objects are achieved by the invention as defined in claims 1 and 14.

The invention relates to an energy exchange structure, comprising plates generally opposite in parallel and assembled to define between them a hollow passage in which a fluid circulates in a generally circular direction between an inlet and an outlet, the said opposite plates being corrugated to form a cruciform structure defining multiple opposing gutters projecting into the hollow passage and arranged to constitute four or more sets of generally parallel gutters drawn to make an oblique with respect to the adjacent sets and also with respect to the direction of circulation of the fluid which flows in the hollow passage formed by the plates assembled to one another. The sets of gutters of a first plate being arranged to join in cross with the opposite sets of gutters of a second plate so that the volume comprised between the opposed gutters of the opposite sets defines cruciform passages in which the fluid can circulate.

Automobile engine oil coolers include multiple opposing plates, stacked to form interconnected energy exchange structures for flow of oil in a generally circular direction. The inputs of the energy exchange structures open into an input collector where they are connected in parallel with the other inputs or else they are connected in series with the inputs and outputs of a second structure. The outputs lead to an output collector and are also connected either in parallel or in series with the inputs and outputs of a second structure.

The stacked and interconnected energy exchange structures provide the passage for the flow of oil inside the energy exchange structures and for the circulation of a cooling fluid outside the energy structures. energy exchange. The preferential direction of the flow of the fluid generally forms an oblique with respect to the axis of the opposite gutters of the opposite plates of the energy exchange structures to improve the energy exchange.

The energy exchange structures can be installed inside a container acting as a housing in which the liquid and / or the cooling gas can be circulated above and between the opposing plates, or alternatively may be exposed to be subjected to a draft or other coolant. The periphery of the stacked energy exchange structures can be made integral with the wall of the housing so as to define separate passages for the coolant which can also be connected separately or interconnected in parallel or in series with the inlet collectors and / or coolant outlet.

Automobile engine oil coolers are manufactured by a process in which opposing plates are corrugated to obtain a cruciform structure forming multiple gutters arranged in four or more sets of generally parallel gutters, with each set forming an oblique with the direction of the adjacent assemblies as well as with the circular direction of the flow of the fluid in the hollow passage formed between the attached plates. The gutters of a first plate are in contact with the tops of the gutters in opposition to a second plate and the area between the gutters in opposition constitutes a passage which preferably must form an oblique between 5 and 75 ° with respect to the circular direction of flow in energy exchange structures. Said first and second plates are assembled to form a hollow passage, comprising an inlet and an outlet for the fluid, the passage being constructed to direct the incoming fluid from the inlet towards the outlet in a generally circular direction. The multiple energy exchange structures can be assembled in series and / or in parallel to constitute the cooler, with an input of a first energy exchange structure connected to an output or to an input of a second energy exchange structure. Typically, it is preferable to assemble one or more groups of structures linked together in parallel with each group organized in series with the inputs and outputs of the collector.

Ordinarily, the energy exchange structures thus assembled are placed in a container serving as a housing equipped with an inlet and an outlet for the coolant. In general, the contiguous outer edges of the opposing plates are extended to form a flat plate providing additional cooling surface on the outer edges of the exchange structures. Such an extension allows the circulation of the cooling fluid over the outer limits of the stacked structures for additional cooling and may also present a practical means of assembling the structures together to immobilize them in the housing.

Figure 1 is a top perspective view of an oil cooler with an energy exchange structure designed according to the present invention.

Figure 2 is a bottom perspective view of the oil cooler of Figure 1.

Figure 3 is a sectional view taken approximately along line 3-3 of Figure 1.

Figure 3a is an enlarged sectional view of a hollow energy exchange structure of Figure 3.

Figure 4 is a sectional view taken approximately along line 4-4 of Figure 1.

Figure 5 is a perspective view of an energy exchange structure designed according to the present invention.

Figure 6 is a plan view of the interior surface of the top plate of Figure 5.

Figure 7 is a plan view of the interior surface of the bottom plate of Figure 5.

Figure 8 is a schematic view of another embodiment of the invention.

By way of example, an embodiment of an automobile oil cooler is illustrated in Figures 1 and 2.

Referring to Figures 1 and 2, there is shown an illustration of an oil cooler 10 of the type usually installed between the vehicle engine and the oil filter according to a conventional layout scheme of automotive technology. The cooler 10 comprises a metal housing 11 having a base for attachment to the engine 12, a base for attachment to the oil filter 20, an outer wall for the housing 17 and an interior opening for the housing 14. The base for attachment to the engine 12 includes an oil inlet 13 and an engine sealing groove 16 which maintains the oil seal 15, as shown in Figures 3 and 4. The outer wall 17 of the housing 11 includes the inlet of the coolant 18 and the outlet of the coolant 19. The bottom of attachment to the oil filter 20 includes an oil outlet 21 and a sealing surface to the oil filter 22. The interior opening of the housing 14 goes from the bottom of the attachment to the engine 12 to the bottom of the attachment to the oil filter 20 and thus presents a passage in which a removable oil filter can be fixed to the engine while ensuring the sealing of the filter and the cooler to the engine as well as the return passage of the cooled and filtered oil to the engine.

The oil cooler 10 comprises a set of hollow energy exchange structures, contained in the housing 11, through which the oil circulates between the oil inlet 13 and the oil outlet 21. Surrounding at at least part of the energy exchange structures, there are hollow passages in which the coolant can flow from the inlet of the coolant 18 to the outlet of the coolant 19 while establishing an exchange ratio of energy with hollow energy exchange structures.

In operation according to the embodiment shown in the diagrams, a first fluid, first brought to high temperature, such as hot engine oil, enters the oil cooler 10 through the oil inlet 13, circulates between the opposite plates by the generally circular passages of all of the hollow energy exchange structures up to the engine oil outlet from the cooler 21 to the inlet of the oil filter (not shown in the figures). The cooled oil passes through the oil filter, then is directed to a hollow oil filter attachment rod (not shown in the figures) which extends to the engine passing through the interior opening 14 of the housing. The hollow oil filter attachment rod attaches to the engine and is threaded in a conventional manner to compress the oil filter and oil cooler to the engine. The rod therefore provides both a means of fixing the filter and the cooler to the engine and a return passage of the cooled and filtered oil from the filter to the engine.

It should be understood that, alternatively, the oil can follow an opposite path: from the engine to the filter by the hollow rod, then to the cooler and back to the engine from the cooler.

The circulation of oil through the exchange structures is directed by several assemblies, arranged to form an angle between them, of generally parallel gutters which protrude into the hollow passage of the opposite plates. The oil flow is passively separated and mixed by the cruciform paths formed by the opposing gutters thus increasing the contact of the oil flow with the opposite plates of the energy exchange structure. The heat energy from the oil is dissipated in the opposite plates of the energy exchange structures and in all the fins with which it can be in contact.

A second fluid, such as a coolant such as a conventional water / antifreeze mixture, enters through the inlet of the cooler 18 so as to circulate through opposite plates or any fin with which it can be in contact, preferably in the direction contrary to the direction of flow of the oil flow. The heat energy is dissipated by the energy exchange structures when the heat energy of the cooling fluid is less than the heat energy of the exchange structures. The coolant flows into the housing containing the exchange structures towards the outlet of the cooler 19 to be recycled by the cooling system.

Referring now to Figure 3, which illustrates a sectional view of the oil cooler of Figure 1 taken approximately along line 3-3, in which there is seen a stack of hollow energy exchange structures 23 to the interior of the housing 11. In Figure 3a, an energy exchange structure is shown enlarged to show an upper corrugated opposite plate 24 and a lower opposite plate 25, joined to form a welded outer border 26. The low points 27 of the gutters directed towards the inside of the upper opposite plate 24 cross the low points 28 of the gutters directed towards the inside of the opposite opposite plate 25, with the area between the low points of the gutters of a plate comprising ridges 29 in the upper plate 24 and ridges 30 in the lower plate 25. The gutters formed downward direct the flow of oil in the exchange structures along the line of the ridges , the cruciform gutters continuously performing passive separation, mixing and redirecting in oblique angular directions the flow of oil in a generally circumferential direction from the entry of the energy exchange structure to the exit of this structure. The volumes between the energy exchange structures stacked one on the other also constitute passages formed by the undulations of the plates. The coolant circulating in these passages is directed by the arrangement of the gutters 27 and 28. As for the oil flow, the arrangement of the gutters performs the passive separation, the mixing and the oblique angular deflection of the current of the coolant from the entry of the cooler until its exit.

In the embodiment illustrated in FIG. 3, the central inner edges of the upper plates 24 and lower plates 25 are joined to each other by means of a compression ring 31 to ensure the general assembly of the hollow energy exchange structures and to ensure the separation of the fluids. The surface 34 of the interior housing opening, thanks to its upper lip 33 and its lower lip 32, retains the base for attachment to the engine 12 and the base for attachment to the oil filter 20 and, by compression, ensures the contact of the upper plates 24 and of the lower plates 25 with one another, by alternating direct contacts and contacts by means of the compression ring 31.

Figure 4 is a sectional view of Figure 1 showing in particular the inlet oil collector 35 and the outlet oil collector 36. It can be seen therein that the upper plates of a first exchange structure for stacked energy and the lower plates of a second energy exchange structure are joined near the inner periphery of the collectors to obtain a sealed separation between the oil and coolant circuits in the exchange structures. It should be clearly understood that if the embodiment illustrated here shows collectors common between all the inputs and all the outputs of the energy exchange structure for oil flows in parallel between the structures, the invention considers this case as specific and includes the organization in separate collectors between the inputs and outputs of the stacked exchange structures for serial oil flows.

The plates of the exchange structures are fixed to each other by any suitable means to ensure a structural integrity of the assembly sufficient to withstand the pressures generated inside the system. A conventional weld by brass welding is preferred when the building materials are in stainless steel, copper, brass or aluminum. Appropriate ceramic or polymer materials can also be used, the assembly of the plates can then be done with suitable solvents, adhesive materials or by welding the materials hot and by ultrasound.

Figure 5 shows a preferred embodiment of an energy exchange structure object of the present invention comprising four sets of gutters. There is an energy exchange structure 23, an opposite corrugated upper plate 24 and a lower corrugated plate 25. The upper plate 24 comprises downward gutters 27 and the lower plate 25 comprises opposite gutters formed downward. bottom 28 (not seen in the Figure) .The area between the gutters of the top plate 24 includes ridges 29 and the area between the gutters of the bottom plate 25 includes ridges 30 (not seen in the Figure), each of these two zones constituting a passage through which the flow of oil circulates. The opposing plates are fixed to each other by their outer edge 26. In the preferred embodiment described here, the edges are brazed to ensure the structural integrity of the assembly of the energy exchange structures. The central inner edge of the exchange structure comprises the compression ring 31 on which the edges of the plates rest.

The gutters of the opposing plates can conveniently be formed by stamping, stamping or molding or any other process which makes it possible to obtain the desired arrangement of gutters in the plates. Conventionally, the gutters are straight or slightly curved and it is preferable that they are short in length.

Although it is not necessary for a gutter to be equidistant from the adjacent gutter on its entire length, such an arrangement is preferable in many applications in the automotive field. By equidistant spacing is meant that the distance between two adjacent gutters generally remains the same all along the gutter. It should be understood that this preferred equidistance does not mean that the distance between the gutters must be the same everywhere, although here too this is preferable for many applications.

The areas between two adjacent gutters constitute the adjacent ridges. Neither the adjacent ridges nor the adjacent gutters need to be the same width. The ridges may be in the plane of the plate or they may be stamped, stamped or otherwise formed so as to protrude from the plane of the plate. It should be understood that all the means well known in the state of the art for forming gutters and ridges, including molding and other process are taken into account by the invention.

Generally ridges and gutters form an oblique to the general circular direction of the plate. Preferably, this oblique will form an angle of between 5 and 75 ° approximately with respect to the circumferential direction taken by the oil circulating between the plates and, better still, between 15 and 45 ° approximately.

The first and second plates in opposition, with their gutters arranged angularly, are assembled in such a way that the gutters of the first plate meet the opposite gutters of the second plate. It is not essential that the gutters and ridges of the first plate form the same oblique angle to the longitudinal direction as those of the second plate, although this is generally preferable. In general, it is preferable that the figure formed by a set of gutters of the first plate in a hollow structure of energy exchange assembled, that is the inverted reflected image of the figure formed by the set of gutters of the second plate.

Figures 6 and 7 show plan views of the inner faces of the upper plate 24 and the lower plate 25 of Figure 5. Figure 6 shows the gutters 27 of the upper plate 24, arranged in four sets so that practically straight gutters are primarily equidistant from the adjacent gutter over their entire length on the plate. The ridges shown in this preferred embodiment are practically of equal width, but it should be understood that the invention takes into account any configuration in which the ridges and the gutters do not have a width equal to the ridge or the gutter which is adjacent to them.

Figure 7 shows the inner surface of the lower plate 25 which is opposite the inner surface of the upper plate 24. There are seen the gutters 28 organized in four sets, with gutters in each set equidistant from the adjacent gutters and forming a reverse reflected image of the upper plate 24. When the upper and lower plates are assembled to face each other, they form the energy exchange structure object of the invention, the gutters of each assembly of the upper plate in contact with the gutters organized according to an inverted reflected image on the lower plate.

FIG. 8 schematically represents a configuration of gutters on the opposite interior surfaces of corrugated plates in which the corrugations form five sets of gutters which are practically parallel, each set being in oblique inside the hollow passage. In this embodiment, the oblique direction relative to the circular flow in the exchanger is not suitable for all sets of gutters for the circulation of the oil flow through the exchanger.

Ordinarily, the oil coolers of the invention can be made from any suitable material which will withstand the effects of corrosion and the internal pressures exerted by the fluid on the system. Conventional material includes malleable metals such as aluminum, copper, steel, stainless steel and their alloys and may even include plastics and / or ceramics.

The material can be coated internally or externally, treated, etc. Typically, it is desirable to use a material as thin as possible to obtain maximum efficiency gain during energy exchange. Generally, it is preferable that each component of the cooler is of the same material whenever they need to be joined together. For example, the plates used to form the energy exchange structures should ideally be made of the same material. It should however be clearly understood that the invention takes into account the use of various materials for assembly, such as for example using steel or plastics to manufacture the housing or the housing bottoms and other metals, plastics or ceramics, for the manufacture of energy exchange structures.

It should be clearly understood that, if the invention described here relates to an automobile oil cooler, it must be considered as applicable to the multiple applications using heat exchange.

Claims (14)

1. Energy exchange structure comprising a first plate and a second plate (24, 25), facing and parallel overall and connected to each other so as to form a hollow passage in which a circulation of fluid in a generally circular direction is established between an inlet (13) and an outlet (21), characterised in that the facing plates (24, 25) are corrugated in order to define a crosswise structure forming multiple channels (27, 28) opposite each other, projecting into the hollow passage and disposed in several sets of generally parallel channels, each set forming an oblique with respect to the adjacent set and with respect to the generally circular direction of the fluid, with the channels (27) in the first plate (24) disposed so as to cross the channels (28) in the second plate (25) so that the area between two opposite channels defines crossed passages.
2. Structure according to Claim 1, characterised in that each of the said facing plates (24, 25) comprises at least four sets of channels (27, 28).
3. Structure according to Claim 1 or 2, characterised in that it comprises generally rectilinear channels (27, 28).
4. Structure according to one of the preceding claims, characterised in that it comprises generally curved channels (27, 28).
5. Structure according to one of the preceding claims, characterised in that channels (27, 28) are disposed obliquely at approximately 5 to 75° with respect to the direction of the fluid in the hollow passage.
6. Structure according to one of the preceding claims, characterised in that the channels (27, 28) in a plate (24, 25) are equidistant from the adjacent channels over their entire length.
7. Structure according to one of the preceding claims, characterised in that it comprises channels (27, 28) which are of generally equal width.
8. Structure according to one of the preceding claims, characterised in that the outer edges of the plates (24, 25) are connected so as to form a flat plate.
9. Structure according to one of the preceding claims, characterised in that the sets of channels are disposed so as to form the same oblique angle with respect to the general direction of circulation of the fluid in the structure.
10. Vehicle oil cooler, characterised in that it comprises at least one energy exchange structure according to any one of Claims 1 to 9.
11. Cooler according to Claim 10, characterised in that the inlet (13) of the energy exchange structure is connected to a header (35) and the outlet (21) of the energy exchange structure is connected to a header (36).
12. Cooler according to Claim 10 or 11, characterised in that the inlet (13) of one energy exchange structure is connected to the outlet (21) of another energy exchange structure.
13. Cooler according to one of Claims 10 to 12, characterised in that a stack of energy exchange structures is constructed in a structure (11) configured so as to enable a second fluid to circulate in the vicinity of the surfaces of the stacked energy exchange structures.
14. Process for manufacturing an oil cooler according to one of Claims 10 to 13, characterised in that it comprises the manufacture of plates (24, 25), corrugated in a crosswise structure so as to form multiple channels (27, 28) disposed in several sets of parallel channels, each set being disposed obliquely with respect to the adjacent sets; the arrangement of the said plates so that the tops of the sets of channels in a first plate (24) are in contact with the adjacent tops of the sets of channels in a second plate (25); the connection of the said first and second plates (24, 25) at their centre and at their outer edges which have been extended so as to form an energy exchange structure having a hollow passage offering a direction of flow of fluid which is generally circular between an inlet and outlet and in which the said channels in the said plates are disposed obliquely with respect to the direction of circulation of the said fluid; and the assembly of several energy exchange structures by stacking them on top of each other.

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