GB2425170A

GB2425170A - Heat exchanger body with longitudinal passages and external longitudinal fins

Info

Publication number: GB2425170A
Application number: GB0515848A
Authority: GB
Inventors: Timothy Frank Brise
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-02-16
Filing date: 2005-08-02
Publication date: 2006-10-18
Anticipated expiration: 2025-08-02
Also published as: GB0503220D0; GB0515848D0; GB2424265A; GB2425170B

Abstract

The invention provides a heat exchanger core element comprising an extruded tubular body of substantially rectangular cross section and having an interior including a plurality of longitudinal passages. A plurality of parallel, integrally formed longitudinally extending fins are provided on the outer surface of the tubular body, the fins being aligned with a longitudinal axis of the tubular body. A tool is used to shear the fins into fin segments which are twisted to form files of fin segments aligned with the longitudinal axis of the body such that each fin segment has a base portion attached to the body and an outermost portion which is twisted out of alignment with the longitudinal axis.

Description

HEAT EXCHANGERS

This invention relates to heat exchangers and to new methods of manufacturing heat exchangers.

Background of the Invention

Numerous types of heat exchangers are known for transferring heat from one medium to another. For example, heat exchangers can be of the radiator type, in which a hot fluid such as water or oil is passed through a radiator provided with a large surface area in order to maximise the transfer of heat from the fluid to the surrounding air. Other types of heat exchangers involve transfer of heat between different liquids such as water and oil.

Heat exchangers are used extensively in industry, particularly in the automotive industry, and common types of heat exchanger include: .. * * Air/air intercoolers for automotive turbochargers * Water/air charge coolers for automotive turbochargers * . : * Water/oil heat exchangers for automotive and industrial use * ***S * Air/oil heat exchangers for automotive and industrial use * : :: : * Air/water radiators for automotive and industrial use * Heaters and condensers for automotive and industrial use In order to maxim ise the transfer of heat from one medium to another, it is usual to provide the pipe or vessel through which the heated fluid is flowing with as large a surface area as possible, and typically such pipes or vessels will be provided with arrays of heat transfer fins along which heat is conducted from the heated fluid within the tube or vessel to a surrounding medium such as air or a cooling fluid.

For a variety of reasons, heat exchangers are typically constructed so that a coolant is passed over the surface of the pipe or vessel containing the heated fluid in a direction transverse to the direction of flow of the heated fluid. Consequently, it is conventional practice to provide a tube or vessel containing a heated fluid with transverse fins. However, manufacturing heat exchangers with transverse fins is not straightforward, and a particular problem is that transverse fins cannot be formed integrally by extrusion.

One method of fabricating heat exchangers involves passing a length of pipe through a series of fins and then expanding the pipe so that the fins are held in place. This form of construction is relatively lightweight and easy to make, but suffers from the disadvantages that it tends to be fairly fragile and has a low heat exchange capacity for a given volume. The reason for the low heat exchange capacity is that only a relatively small proportion of the fluid flowing through the pipe is in contact with the wall of the pipe and consequently much of the liquid passes through the pipe without giving up its heat to the walls of the pipe and the fins.

An alternative method of constructing heat exchanger cores involves brazing fins to * an extruded or seam welded tube. This method is far from ideal in that it requires careful control of temperatures in order to compensate for the different thicknesses * of the tube wall and the material from which the fins are made, and tends to be both *.* time and energy consuming. Typically, the tube will need to be clad with a brazing * * alloy having a lower melting point than the fins or tube, a requirement that would effectively preclude the formation of the tube by extrusion.

Another method of constructing heat exchanger cores, and which addresses the problem of poor heat transfer encountered in many known types of core, has been to employ aluminium extrusions containing multiple longitudinal passages running along the length of the extrusion. The provision of multiple passages running through the core ensures that a much greater proportion of the liquid passing through the extrusion is in contact with a metal wall to allow transfer of heat. The external surfaces of the extrusions are then provided with an array of transverse fins to maximise heat loss to the surrounding environment. However, a problem with this type of construction is that since the fins are transverse to the longitudinal passages through the extrusion, they cannot be formed during the extrusion process.

Instead, the fins are typically formed from lengths of thin metal ribbon that are folded into a concertina pattern and then fixed to the surface of the extrusion in a subsequent manufacturing step. Because the fins are formed from a relatively thin material, connecting them to the surface of the extrusion by methods such as brazing can be difficult, for the reasons set out above. Adhesive is therefore often used as a means of bonding the fins to the surface of the extrusion. This is a far from satisfactory solution, since there is typically an air break between the extrusion and the fins, thereby reducing heat transfer to the fins. In addition, the glue can act as an insulator thereby further reducing the heat transfer to the fins. An example of a heat exchanger core constructed in this way is shown in Figure 1.

As can be seen from Figure 1, the heat exchanger core 2 comprises a plurality of flattened oval extrusions 4 secured together by a header plate 6. The interiors of each of the oval extrusions are divided up into a series of longitudinal passages by webs 8. Internal fins 10 increase the surface area in contact with fluid passing * through the channels, thereby maximising heat transfer to the external surface 12 of the extrusion. S...

S I...

The outer surface 12 has bonded thereto by means of an adhesive an array of fins S...

14. Each fin 14 consists of a thin ribbon strip of aluminium foil folded into a S...

concertina and then glued to the surface 12 of the extrusion. This type of,. : construction suffers from several inherent disadvantages. Firstly, the transverse fins are very fragile and can easily be bent or otherwise damaged during the assembly operation. Secondly, there is relatively poor contact between the lower surfaces of the fins and the surface 12 of the extrusion. In many cases, there is an air gap between the bottom of the fin and the surface of the extrusion. In addition, the glue between the extrusion and the fins can act as an insulator, thereby inhibiting heat flow. As a consequence, the efficiency with which heat is transferred from the interior of the channels to the fins and thence to the surrounding environment is relatively poor.

Summary of invention

The present invention provides a method of fabricating a tubular heat exchanger core element by initially extruding a tubular body having one or more longitudinal fins extending along its length and then subjecting the fins to a mechanical shearing and deforming step to create an array of fin segments that are twisted out of alignment with the longitudinal axis of the tubular body. By shearing the longitudinal fins into segments and twisting the segments out of alignment with the tube axis, gaps are created that allow one fluid to flow transversely across the surface of the tubular body thereby enabling the exchange of heat with another fluid flowing through the interior of the tubular body.

The method of the invention provides a heat exchanger core element in which the segmented fins are formed integrally with the tubular body, in contradistinction to known methods of fabricating heat exchanger core elements that involve the initial extrusion of a finless tubular core and the addition of fins by brazing, adhesive bonding, or by a milling process. *

In one aspect therefore, the invention provides a heat exchanger core element * comprising an extruded tubular body having at least one file of integrally formed fin segments on an outer surface thereof, the file of fin segments being aligned with S...

a longitudinal axis of the extruded tubular body; each of the fin segments having a base portion connected to the tubular body, and an outermost portion which is::: e..

twisted out of alignment with the longitudinal axis. * .. : Typically, the extruded tubular body has a plurality of files of integrally formed fin segments on the outer surface thereof, each file being aligned with the longitudinal axis of the body. For example, the extruded tubular body may have at least 5 files of integrally formed fin segments, e.g. 6, or 7, or 8, or 9, or 10, or 11, or 12 files of integrally formed fin segments.

Each segment has a base portion integrally connected to the tubular body, and an outermost portion. The outermost portion of the segment is twisted out of alignment with the longitudinal axis. Preferably, the base portion of the segment remains in alignment with the axis of the extruded tubular body. The angle formed between the fin segment and the longitudinal axis may increase progressively from the base portion towards the outermost portion of the fin segment. Thus the fin segments, when twisted, may have a partially helical profile.

The outer portions of the fin segments typically form an angle of between about 30 and 600 with the longitudinal axis. More typically, the upper portions of the fin segments form an angle of between about 30 and about 50 .

Typically, all of the fin segments in a file are aligned in the same direction.

However, as an alternative, the fin segments in a given file may differ in their alignment:- for example, the fin segments may have alternating alignments. In a further alternative, a block of fin segments of a given file may be aligned in one direction, and an adjacent block of segments of the same file may be aligned in another direction. Preferably, however, the fin segments in a given file are all aligned in the same direction.

Similarly, the fin segments in adjacent files may be aligned in the same direction, or in different directions. Preferably, however, all of the fin segments one side of the tube will be aligned in the same direction.

The tubular body may have a flaftened cross section, presenting an upper surface and a lower surface, and two side surfaces linking the upper and lower surfaces. : Typically, at least one and preferably a plurality of files of fin segments are SS* S provided on the upper and lower surfaces of the tubular body. *:::: In one embodiment, the tubular body is of substantially rectangular cross section.

The shorter side surfaces of the rectangular cross section may be radiussed or otherwise curved, or they may be straight.

The interior of the tubular body is typically divided into a plurality of longitudinal passages, the dividing walls between the passes serving both to strengthen the tubular body and to increase the surface area over which transmission of heat to or from the fluid flowing through the passages may take place. The passages may be, for example, arranged side by side.

The surface areas of the tubular body or individual passages through the tubular body may be further increased by means of internal fins or other protrusions extending inwardly from the inner surfaces of the tubular body or passage.

The heat exchanger core elements may be configured so as to be stackable, the fin segments on a surface of one tubular body being of a size and orientation such that the spaces therebetween can accommodate the fin segments on a surface of the tubular body of an adjacent heat exchanger core element.

In one embodiment, the fin segments on an upper surface of the tubular body and the fin segments on the lower surface of the tubular body are all rotated clockwise by an angle of up to about 45 with respect to the longitudinal axis, and in another embodiment the fin segments on an upper surface of the tubular body and the fin segments on the lower surface of the tubular body are all rotated anticlockwise by an angle of up to about 45 with respect to the longitudinal axis. The sizes and angles of inclination of the fin segments on the respective surfaces are selected such that when heat exchanger core element are stacked, the fin segments on the upper * S...

surface of one heat exchanger core element fit between the fin segments of the fin *.

segments of the lower surface of another heat exchanger core element. More particularly, the relative alignments of the fin segments of the stacked heat exchanger core elements may be such as to create a "herringbone" array of fin. . : segments between the surfaces of the tubular bodies. . *... S... S...

In a further embodiment, the fin segments on one surface of the tubular body are * ..

rotated clockwise by an angle of up to about 45 with respect to the longitudinal axis, and the fin segments on the other surface of the tubular body are rotated anticlockwise by an angle of up to about 45 with respect to the longitudinal axis.

When two or more heat exchanger core elements are stacked, the interfitting fin segments define a plurality of tortuous paths between the confronting surfaces of the tubular bodies, through which a fluid can pass. The gaps between the fin segments are selected so that a balance is struck between, on the one hand, ensuring that flow of the fluid around the fin segments between the surfaces of the tubes is turbulent rather than laminar and, on the other hand, ensuring that there is not an unacceptable pressure drop across the flow path. By creating turbulent flow, the boundary effects arising from slower movement of fluid along a surface are minimised, and heat exchange between the fluid and the fin segments is enhanced.

The part helical configuration of the fin segments further assists in creating turbulent flow.

The heat exchanger core elements, or a stack of heat exchanger core elements, can be enclosed within a casing, the casing having inlets and outlets for each of the fluids passing through the heat exchanger. An advantage of configuring the fin segments on adjacent core elements so that they interlock when stacked is that the individual tubes are much closer together and hence more tubes per unit volume can be incorporated into a heat exchanger than is possible with the convoluted fin heat exchanger cores of the type described above. A further advantage of employing arrays of interlocking fin segments is that it is possible to connect stacked core elements together without using a header plate of the type shown in Figure 1 by infilling the open ends of the voids between the core elements with weld material. s's I...

This further assists in making the heat exchanger more compact. . In another aspect, the invention provides a heat exchanger comprising at least one heat exchanger core element as here inbefore defined. 5***

In a further aspect, the invention provides a heat exchanger comprising one or more * : : ::* heat exchanger core elements enclosed within a casing, the casing having inlet and outlet openings for a first fluid, and inlet and outlet openings for a second fluid.

Instead of enclosing one or more heat exchanger cores within a casing, a heat exchanger core may be provided with inlet and outlet manifolds at either end so that it can function as an air-liquid heat exchanger. Accordingly, in another aspect, the invention provides a liquidlair heat exchanger comprising a heat exchanger core as defined herein having inlet and outlet manifolds at either end for connection to other elements of a cooling system.

The segmentation of the fins on the heat exchanger cores means that they can be bent much more easily than would be the case if the fins were not segmented. For example, the heat exchanger core can be bent into a coil for use in association with a cooling fan.

In a still further aspect, therefore, the invention provides a liquid/air heat exchanger comprising a heat exchanger core as defined herein having inlet and outlet manifolds at either end but wherein the core has been formed into a coil.

The heat exchanger may be used for the transfer of heat between any two fluids in connection with which heat exchangers are commonly used, and examples of such heat exchangers are set out in the introductory part of this application.

The invention also provides a process for making a heat exchanger core element, the process comprising the steps of: (i) extruding a tubular element having one or more fins along the outer surface thereof, the fins being aligned with the longitudinal axis of the tubular element; (ii) bringing the tubular element into contact with a shearing and deforming tool; (ii) operating the shearing and deforming tool to shear the or each fin into a plurality of fin segments and to twist each fin segment so that an outer portion of each fin segment is twisted out of alignment with the longitudinal axis of the: : tubular element. I...

S

The shearing and deforming tool may be operated in an incremental manner in a * process comprising a repeating sequence of steps in which the tubular element and/or the shearing and deforming tool are advanced by a predetermined distance so that the tool is positioned above an unsheared portion of the or each fin, and the tool is then actuated to shear and twist a segment of the or each fin.

A plurality of shearing and deforming tools may be arranged in an array, so that each fin on a given surface (e.g. upper surface) has a tool positioned above it. A shearing and deform ing tool may be actuated by hand or by means of a powered actuator. For example, the tools may be mounted in a holder or holders each provided with a guide surface or cam that interacts with a cam or guide surface on a tool so that downwards motion of the tool is converted into a rotational motion to give rise to a shearing action. An actuator may take the form of a ram (e.g. a hydraulic ram) or press which may be used to impart downwards motion to the tool.

The tubular element can be advanced past the shearing and deforming tool manually or with the assistance or using a powered feeding device.

In a further aspect, the invention provides a tubular structure from which a heat exchanger core element of the invention can be formed, the tubular structure comprising an extruded tubular body of substantially rectangular cross section having an interior divided into a plurality of longitudinal passages by means of a plurality of dividing walls, the tubular body having an upper surface and a lower surface, and a plurality of substantially parallel integrally formed longitudinally extending fins on each of the upper and lower surfaces, the fins being aligned with a longitudinal axis of the tubular body.

Brief Description of the Drawings

Figure 1 illustrates a known type of heat exchanger core element.

Figure 2a is a view from one end of an aluminium extrusion from which a heat exchanger core element according to one embodiment of the invention can be made.

Figure 2b is a view from above of the extrusion of Figure 2a.

Figure 3a is a perspective view of a forming tool and tool holder used to segment the fins on the extrusion of Figures 2a and 2b.

Figure 3b is a view from one side of the tool holder shown in Figure 3a.

Figure 3c is a view from the front of the tool holder shown in Figure 3b.

Figure 3d is a view from one side of the tool shown in Figure 3a.

Figure 3e is a view from above of the tool shown in Figure 3d.

Figure 3f is a view from another side of the tool shown in Figures 3d and 3e.

Figures 3g and 3h are views from the underside of the tools of Figures 3d.

Figure 3i is an enlarged view of Figure 3h.

Figure 4a is an end view of a heat exchanger core element showing the fin segments.

Figure 4b is a view in direction A of the heat exchanger core element of Figure 4a.

Figure 4c is a view in direction B of the heat exchanger core element of Figure 4c.

Figure 5a is an end view of a stack of heat exchanger core elements of the invention.

Figure 5b is an end view of the stack of heat exchanger core elements of Figure 5a within a casing.

Figure 5c is an end view of the casing shown in Figure 5b.

Figure 5d is an end view of the casing and stack of heat exchanger core elements of: . Figure Sb welded to provide an end seal.

Figure 5e is an end view corresponding to Figure 5a but with cutting lines shown.

shown.

Figure 5f is a partial sectional elevation along line I-I in Figure 5e.

Figure 5g is an end view of the casing and stack of heat exchanger elements of Figures Se and 5f with the spaces between the elements closed at the ends thereof.

Figure 5h is a partial sectional elevation along line Il-Il in Figure 5g.

Figure 6a is a view from above of an oil-water heat exchanger containing the heat exchanger core elements of Figures 4a to Sd.

Figure 6b is a side view of the heat exchanger of Figure 6a.

Figure 6c is an end view of the heat exchanger of Figures 6a and 6b.

Figure 7 is a schematic view of the interior of the heat exchanger of Figures 6a to 6c showing the flows of oil and water through the heat exchanger.

Figure 8a is a side view of a heat exchanger according to a further embodiment of the invention.

Figure 8b is a view from direction C of the heat exchanger of Figure 8a.

Figure 8c is a sectional elevation along line 111-111 of the heat exchanger of Figure 8a.

Figure 9 is an isometric view showing the heat exchanger of Figures 8a to 8c formed into a coil configuration.

Detailed Description of the Invention

The invention will now be illustrated, but not limited, by reference to the specific embodiments shown in the drawings Figures 2a to 7. 0*IS * *

The heat exchanger core elements of the invention are manufactured from extrusions, typically metal (e.g. aluminium) extrusions, comprising a tube having at least one fin (and usually a plurality of fins extending along its length. One: S...

example of such an extrusion is shown in Figures 2a and 2b. S... * S

As shown in Figures 2a and 2b, the extrusion comprises a tube 202 of flattened *: :: *.

rectangular form having a plurality of elongate fins 204 extending along its length.

Both the upper and lower surfaces of the tube are provided with fins 204 which are formed integrally with the tube during the extrusion process.

The interior of the tube 202 is divided by walls 206 into a plurality of passages 208 each of which in this embodiment is of generally square cross section. The walls 206 serve both to strengthen the tube and to provide an increased surface area to enhance heat transfer. The inner surfaces of each passage 208 are provided with a number (in this case four) of ridges or protrusions 210 which further increase the surface area over which heat transfer can take place.

The extrusions shown in Figures 2a and 2b may be of use for use in air cooling applications where the heat exchanger core element is not encased. However, because the fins are aligned with the longitudinal axis of the tube, the extrusions are not per se generally suitable for use in enclosed heat exchangers where cooling of a fluid is effected by passing a stream of a coolant transversely over the surface of a tube carrying the fluid. According to the present invention therefore, the fins 204 are segmented and the fin segments twisted so that at least the upper parts of the fin segments are at an angle with respect to the longitudinal axis of the tube.

Segmenting the fins and twisting the fin segments creates lateral flow paths across the surface of the tube along which coolant can flow.

A manually operable apparatus for segmenting the fins is shown in Figures 3a to 3h. The apparatus consists of a tool holder 302 comprising a block 304 having a guide slot 306 running along its lower edge. The guide slot 306 is of a width and depth to enable it to sit on a fin 308 on the extrusion 300. Connected to the block 304 is a cylindrical tube 310 within which is mounted the shaft 314 of the tool 312.

The lower end of the shaft 314 ofthe tool 312 has a slot 316 formed therein, the side walls of which are substantially parallel at the upper ends thereof and curved at the lower ends thereof. The radius of curvature of the walls of the slot increases from top to bottom, as can be seen most clearly from Figure 3i. At the upper end of..:.

the shaft is a T-bar, one end 320 of which is cranked and acts as a stop to limit the * I...

extent to which the tool can be rotated in the holder. A handle 322 extends:::* outwardly and upwardly from the side of the block 304, the upper end of the handle acting as an abutment that engages the cranked end of the T-bar to limit its rotation.

In use, the tool 302 is positioned on a fin at a desired location so that the guide slot in the tool holder and the slot in the tool both sit on the fin. The T-bar is then turned so that a shearing motion is created between the slotted tool and the edge of the guide slot in the tool holder. A segment is thus cut and the segment is rotated out of alignment with the remainder of the fin 308. As a result of the variable curvature of the slot in the tool, the base of the segment remains in alignment with the fin whilst the upper part of the segment is twisted out of alignment with the fin, the angle of rotation increasing from the base of the segment to the top of the segment. The tool is then lifted off the deformed segment and moved over a region of undeformed fin and the exercise repeated until the fins on the extrusion have been fully segmented.

The manually operated tool illustrated in Figures 3a to 3i demonstrates the principles involved in creating files of fin segments on the extrusion. However, on a manufacturing scale, the process may be automated and an array of tools may be used together with automatic means for actuating the tools.

For example, a tool holder may be provided that carries a plurality of shearing and deforming tools, one for each fin on an extrusion. Each tool holder may contain a guide surface or cam arrangement that engages a complementary cam or guide surface on a tool to convert axial movement into rotational motion. Each tool may be spring loaded so that after each shearing and deforming action, it is lifted clear of the deformed segment. A ram or press may be used to provide the downwards force on the tool. Thus, at each stroke of the press, the tools are urged downwardly onto the fins. Once the fins have been engaged, further downwards force is * :: :: converted into rotational motion so that a segment of each fin is sheared against the static cutting edge of the tool holder and twisted out of alignment with the longitudinal axis of the extrusion. The cutters are then lifted by the return springs and the extrusion is advanced by the correct pitch length to present the next sections of the fins for shearing and deforming. A conventional compressed air-driven Is., feeder can be used to advance the extrusion towards and past the shearing and. ::: : deforming tool.

When the complete length of the extrusion has passed through the forming station, the result is a heat exchanger core element as shown in Figures 4a to 4c, each fin having been divided into a plurality of fin segments 404 that are inclined at an angle with respect to the longitudinal axis 406 of the tube 402. The cutting and forming operation is carried out such that the angle of the fin segment to the longitudinal axis 406 increases from the lower part of the fin segment, where it is attached to the tube surface, to the upper edge 408 of the segment. Thus, the upper edge of the fin segment is inclined at an angle of about 35 to the longitudinal axis whereas the lower part (or root) 410 remains in alignment with the longitudinal axis. In between the upper edge 408 and the root 410, the fin segment has a partial helical form, the advantages of which are discussed below.

The rotatable tool can be mounted in the tubular mounting so that it can be rotated in either direction. Thus, the fin segments can be cut and twisted so that they all face in the same direction, or they can be cut and twisted so that the segments in adjacent files, or adjacent rows, or on opposite sides of the tube, face in opposing directions. The angles of rotation and pitch length of the segments are chosen such that the segments on an upper surface of one tube will intermesh with the fin segments on a lower surface of another tube to form a herringbone patternwhen two heat exchanger core elements are stacked.

In order to construct a heat exchanger, a number of the heat exchanger core elements will be stacked and welded together as shown in Figures 5a to 5d. In the embodiment shown in Figure 5a, five heat exchanger core elements 502 have been stacked and welded together, the welds being shown as the dark areas in Figure Sd.

Usually, the stack of elements will be contained within a casing 504 and the spaces * between the edge 506 of the stack and the inner wall 508 of the casing may be filled in with weld material at the two ends of the stack as shown in Figure 5d so that only the passageways 510 through the tubes are open at the ends of the stack.

An alternative method of sealing the spaces between the core elements 502 at their ends is illustrated by Figures 5e, Sf, 5g and 5h. As shown in Figures Se and 5f, prior to inserting the stack of elements into the casing 504, the fin segments 522, side walls 524 of the tube and the interior walls 206 are cut away along lines 520 (only some of which are shown in the drawing) to a depth of about 4-5 mm to leave the protruding ends 528 of the upper and lower walls of the tubes. The protruding ends 528 of adjacent tubes in the stack are then bent towards each other and welded together along lines 530 so that they cover the spaces between the tubes but allow access to the interiors of the passages 208 extending through the tubes. The outermost two protruding ends are bent outwardly so that they partially overlay the outermost fin segments. The stack of core elements is then inserted into casing 504 and the remaining gaps 532, 534, 536 between the casing 504 and the stacked core elements may then be filled with weld material so that a complete seal is formed.

In order to reduce the amount of weld material required, the sides 538 of the casing can be crimped inwardly (as shown in Figure 5g) at the ends prior to welding to reduce the gap between the casing and the core elements.

The advantages of the arrangement shown in Figures 5e to 5h are firstly that there is less likelihood of the passages 208 being blocked with weld material, and secondly that less weld material is required.

The assembled stacks of heat exchanger core elements shown in Figures 5a to 5h can be used to manufacture a heat exchanger, for example a wateroil heat exchanger as shown in Figures 6a to 6c.

In order to form the heat exchanger, a manifold 602 is welded onto either end of the casing 504, the manifolds having openings 606 and 607 which can be, for example, threaded for connection to associated pipe work. Two diagonally opposed lateral openings 604 and 605 are also provided on the casing 504 and, as with the openings. $ 606 and 607, the lateral openings can be threaded for connection to other elements of the cooling system. *( (

The interior of the heat exchanger is shown schematically in Figure 7. Cooling water passes in a longitudinal direction through the passages 510 (not shown) from. S..

the inlet 606 to the outlet 607 whilst oil flows through the spaces between the fin segments from inlet 604 to outlet 605. The intermeshing fin segments 702 and 704 of adjacent heat exchanger core elements together form a herringbone pattern which provides a tortuous path for oil entering the inlet 604 and flowing towards the outlet 605. The herringbone arrangement does not greatly impede the flow of oil and allows the flow of oil through the heat exchanger to take place relatively quickly whilst at the same time creating turbulence that allows heat transfer to take place more efficiently. The turbulence is enhanced by the part helical shape of the fin segments.

The heat exchanger core elements and heat exchangers of the invention offer a number of advantages over conventional heat exchangers. Thus, for example, because the fin segments are formed integrally with the tube carrying the fluid to be cooled, rather than being brazed or adhesively bonded to the tube, there is no thermal barrier to heat transfer from the interior of the tube to the fin segments.

The manufacture of the heat exchanger core elements is also more efficient than with many known types of heat exchanger in that there is no material wastage through milling away excess metal, and the number of brazing or welding operations required to make a heat exchanger is minimised. Moreover, the arrangement of the files of fin segments provides more turbulent flow of fluid across the heat exchanger thereby minimising the boundary effect at the surfaces of the fins and maximising heat transfer.

The heat exchanger core elements of the invention may be used in a wide variety of types of heat exchanger. Further examples of heat exchangers comprising the heat exchanger core elements of the invention are illustrated in Figures 8a to 8c and 9.

Figures 8a to 8c illustrate an air/oil heat exchanger 800 in which hollow cylindrical members 802 have been connected to the two ends of the heat exchanger core element 804 by welding or brazing. The heat exchanger core element 802 corresponds to the core elements described above and illustrated in Figures 3a, 4a, 4b and 4c. The hollow cylindrical members 802, which serve as inlet and outlet manifolds for the heat exchanger, are closed at one end and their hollow interiors: S...

communicate with the longitudinal passages extending through the core element. At S...

the other end of each hollow cylindrical member 802 is a threaded region 806 5.5 which allows connection to pipework or hoses feeding the heat exchanger. .. : Figure 9 is an isometric view of an oil/air heat exchanger in the form of a coil which may be used in, for example, an automotive context. The coiled heat exchanger 902 can be formed by bending the linear heat exchanger 800 shown in Figures 8a to 8c.

A circular former, which may be made of wood or a plastics material, is placed on one surface of the linear heat exchanger 800 so that it is in contact with the core and one of the hollow cylindrical members. The diameter of the former is chosen to be the minimum diameter that the extrusion may be bent or rolled onto, without excessive distortion of its internal tubular section. The former and the hollow cylindrical member are clamped together and then rolled into a coil or spiral shape.

When the whole of the length of the heat exchanger has been rolled, the former can be extracted leaving the heat exchanger in its coiled state.

The segmented nature of the fins means that the heat exchanger can be rolled into a coiled configuration much more easily than would be the case if the fins were not segmented. The fin segments on the internal surface of the coil will move together and overlap with each other as the heat exchanger is rolled, and will stretch apart from each other on the outer surface of the coil. The internal walls within the extrusion allow the coil to be wound on a tight radius without deformation of the tubular internal section.

Equivalents It will readily be apparent that numerous modifications and alterations may be made to the specific embodiments of the invention described above without departing S...

from the principles underlying the invention. All such modifications and alterations: are intended to be embraced by this application. * S...

S S... * S... *. *5

SS S

Claims

1. A heat exchanger core element comprising an extruded tubular body having an interior which is divided into a plurality of longitudinal passages; the tubular body having a cross section defined by an opposed pair of wider sides linked by an opposed pair of narrower sides, one or both of the wider sides having extending outwardly therefrom a plurality of files of integrally formed fin segments, the files of fin segments being aligned with a longitudinal axis of the extruded tubular body; each of the fin segments having a base portion connected to the tubular body, and an outermost portion which is twisted out of alignment with the longitudinal axis.

2. A heat exchanger core element according to claim 1 wherein the tubular body is of substantially rectangular cross section. *.S.

3. A heat exchanger core element according to claim 1 or claim 2 wherein each * *** fin segment has a base portion integrally connected to the tubular body, and *. * an outermost portion, the outermost portion of the fin segment being twisted out of alignment with the longitudinal axis and the base portion of the fin: S..

segment remaining in alignment with the axis of the extruded tubular body. * S S...

4. A heat exchanger core element according to claim 3 wherein an angle formed * : ::: between the fin segment and the longitudinal axis increases progressively from the base portion towards the outermost portion of the fin segment, and the fin segment has a partially helical profile.

5. A heat exchanger core element according to any one of the preceding claims wherein all of the fin segments in a file are aligned in the same direction.

6. A heat exchanger core element according to any one of the preceding claims wherein the fin segments on one side of the tubular body are aligned in the same direction.

7. A heat exchanger core element according to any one of the preceding claims wherein the longitudinal passages are arranged side by side.

8. A heat exchanger core element according to any one of the preceding claims wherein the tubular body or longitudinal passages through the tubular body have internal fins or other protrusions extending inwardly from the inner surfaces thereof.

9. A heat exchanger core element according to any one of the preceding claims wherein which is stackable with another heat exchanger core element, the spaces between fin segments on a surface of one tubular body being of a size and orientation to accommodate the fin segments on a surface of the tubular body of an adjacent heat exchanger core element.

10. A heat exchanger core element according to claim 9 wherein the fin segments on an upper surface of the tubular body are aligned in one direction, and the fin segments on the lower surface of the tubular body are aligned in an opposite direction, the size and angles of inclination of the fin segments on the respective surfaces being selected such that when heat exchanger core elements are stacked, the fin segments on the upper surface of one heat exchanger core element fit between the fin segments of the lower surface of S...

another heat exchanger core element. ..:. S...

11. A heat exchanger component comprising a plurality of stacked heat exchanger core elements as defined in any one of the preceding claims. * ::: :

12. A heat exchanger core element as defined in any one of the preceding claims, or a stack of heat exchanger core elements, enclosed within a casing, the casing having inlets and outlets for a pair of fluids between which heat is to be exchanged.

13. A heat exchanger comprising at least one heat exchanger core element as defined in any one of the preceding claims.

14. A heat exchanger comprising one or more heat exchanger core elements as defined in any one of the preceding claims enclosed within a casing, the casing having inlet and outlet openings for a first fluid, and inlet and outlet openings for a second fluid.

15. A heat exchanger comprising a heat exchanger core as defined in any one of claims 1 to 10 having inlet and outlet manifolds at either end thereof.

16. A heat exchanger according to claim 1 wherein the heat exchanger core is formed into the shape of a coil.

17. A process for making a heat exchanger core element as defined in any one of the preceding claims, the process comprising the steps of: (i) extruding a tubular body having one or more fins along the outer surface thereof, the fins being aligned with the longitudinal axis of the tubular element; (ii) bringing the tubular body into contact with a shearing and deforming tool; (ii) operating the shearing and deforming tool to shear the or each fin into a plurality of fin segments and to twist each fin segment so that an outer S...

portion of each fin segment is twisted out of alignment with the longitudinal * axis of the tubular element.

18. A process according to claim 16 wherein the shearing and deforming tool is:" operated in an incremental manner in a process comprising a repeating S...

sequence of steps in which the tubular element and/or the shearing and *.. .

deforming tool are advanced by a predetermined distance so that the tool is *.. : positioned above an unsheared portion of the or each fin, and the tool is then actuated to shear and twist a segment of the or each fin.

19. A heat exchanger core element substantially as described herein with reference to the accompanying drawings Figures 2 to 7.

20. A heat exchanger substantially as described herein with reference to the accompanying drawings Figures 2 to 7.

21. A tubular structure from which a heat exchanger core element according to any one of claims 1 to 10 can be formed, the tubular structure comprising an extruded tubular body of substantially rectangular cross section having an interior divided into a plurality of longitudinal passages by means of a plurality of dividing walls, the tubular body having an upper surface and a lower surface, and a plurality of substantially parallel integrally formed longitudinally extending fins on each of the upper and lower surfaces, the fins being aligned with a longitudinal axis of the tubular body.

22. A tubular structure according to claim 21 wherein the rectangular cross section has a pair of longer sides and a pair of shorter sides, the longer sides being straight and the shorter sides being radiussed or otherwise curved, or straight. S... * S * . * S S * SS

S S... S... * S S... **.

S S S