PLATE TYPE HEAT EXCHANGER

Abstract: A heat exchanger of the type having a stack of heat exchange units (14) each formed from first and second thin plates (30, 32) having grooves and ribs, wherein the grooves and ribs on facing surfaces of the first and second plates of a unit cross one another and co-operate to define a first flow path, and grooves and ribs on facing surfaces of first and second plates (30, 32) of adjacent units cross one another and co-operate to define a second flow path, wherein the ribs and grooves have transverse projections formed therein to provide the second flow path with a cross-sectional area exceeding the cross-sectional area of the first flow path.

Description: PLATE TYPE HEAT EXCHANGER TECHNICAL FIELD This invention relates to heat exchangers, and in particular, to plate type heat exchangers used in automotive applications as oil coolers. BACKGROUND ART It is known to provide oil coolers for vehicle engines, which are arranged between an engine block and an oil filter and connected to an engine cooling system to permit a cooling liquid, such as water, to pass in heat exchange relationship with oil flowing through the oil cooler. In European patent application Serial No. 90403244.8 filed November 17, 1989 (publication No. 0 430 752 Al) there is disclosed circumferential flow heat exchangers having a stack of like heat exchange units or plate pairs ' , each formed from first and second plates, wherein the plates of each unit co-operate to define a first or oil flow path and the plates of a pair of adjacent units co¬ operate to define a second or water flow path with the cross-sectional areas of such flow paths being essentially equal. Such heat exchangers are effective in controlling movement, i.e. mixing or turbulence, of oil along the first flow paths in a manner which tends to maximize exposure thereof to heat transfer contact with flow bounding surfaces of the plates. The present invention is an improvement over such heat exchangers, especially in the lower range of oil flow rates. DISCLOSURE OF INVENTION In accordance with the present invention, the configuration of the first and second plates forming the heat exchange units allows for the cross-sectional areas of the first and second flow paths defined by each unit and a pair of adjacent units to be selectively varied in size, as required, to optimize oil heat transfer characteristics throughout the full range of oil flow rates typically encountered in vehicle engines. The present invention broadly contemplates reducing the height of crests or ribs formed on the outer surfaces of the plates of each plate pair, and thereby reducing the spacing between the troughs or grooves formed on the inner or facing surfaces of the plates in alignment with such ribs, in order to effect a respective increase and decrease of the cross-sectional areas of the water and oil flow paths. " Spacing between units, and thus the cross-sectional areas of each of the second or water flow paths defined thereby are maintained uniform, by providing the ribs with integrally formed projections having heights corresponding to the reduction in height of the ribs, to provide the units with a desired overall thickness or height. Accordingly, a reduced flow restriction may be provided for coolant flowing along the second flow paths, as compared to oil flowing along the first flow paths, resulting in the ability to substantially change or control the relative pressure drops to which coolant and oil are subjected in passing through an oil cooler, to optimize heat transfer efficiency and provide pressure drop characteristics satisfying automotive industry performance requirements. Increasing the effective cross-sectional area of the second flow paths, as compared to that of the first flow paths, allows the density of the ribs and grooves present on a given unit of surface area of the plates to be increased, thereby serving to increase mixing or turbulence efficiency of the oil without resulting in an oil cooler having an unacceptable water pressure drop performance. BRIEF DESCRIPTION OF THE DRAWINGS The nature and mode of operation of preferred embodiments of the present invention will now be more fully described in the following detailed description, taken with the accompanying drawings wherein: Figure 1 is a perspective view of a heat exchanger incorporating a plurality of heat exchange units formed in accordance with the present invention; Figure 2 is a cross-sectional view taken generally along the lines 2-2 in Figure 1 and showing an outer surface of a first plate of one of the heat exchange units; Figure 3 is a cross-sectional view taken generally along the lines 3-3 in Figure 1 and showing an inner surface of a second plate of one of the heat exchange units; Figure 4 is a sectional view taken generally along the lines 4-4 in Figure 2; Figure 5 is an enlarged view of the area designated as A in Figure 4; and Figure 6 is a view taken generally along the lines 6-6 in Figure 5. BEST MODE FOR CARRYING OUT THE INVENTION An exemplary embodiment of an automotive oil cooler 10 is illustrated in Figure 1 and is intended to be installed between an automotive engine and the engine oil filter (not shown) . It should, however, be understood that the present invention can be utilized in a plurality of other applications, wherein it is desired to effect heat exchange between dissimilar fluids. Automotive oil cooler 10 generally includes a canister 12 housing a stack of heat exchange units or plate pairs designed as 14 in Figures 2 and 4. Canister 12 is defined by an oil filter attachment end portion 16, engine attachment end portion 18, an exterior canister side wall portion 20 provided with coolant outlet and inlet connections, 20a, 20b, and a centrally located sleeve portion 22, which is end connected to end portions 16, 18 and arranged to extend through centrally disposed registration openings 24 of units 14 when they are arranged in a stacked relationship within the canister, as indicated in Figure 4. Heat exchange units 14 are each defined by first and second plates 30, 32 shown in Figures 2 and 3, respectively; and a flow separator 34 shown in Figures 3 and 4. Plates 30, 32 may be formed of thin sheet-metal stock and die cut to define registration openings 30a, 32a, oil outlet openings 30b, 32b, and oil inlet openings 30c, 32c. Plates 30, 32 are embossed or otherwise formed to define.plurality of flow directing elements to be described further below. Preferably, the diameter of plate 32 exceeds that of plate 30 to provide material for defining an annular flange portion 32d intended to clamp about the peripheral edge of its associated plate 30 as shown in Figures 2 and 4. As formed, plates 30, 32 have first or outer, oppositely facing surfaces 40, 42 of like configuration and second or inner oppositely facing sur aces 40' , 42' of like configuration. When plates 30, 32 are assembled or joined together with separator 34 to form unit 14, with openings 30a, 30b and 30c in registration with openings 32a, 32b and 32c, respectively, outer surfaces 40, 42 define mirror images of one another and inner surfaces 40' , 42' define mirror images of one another. To facilitate the following description of the surface configurations of plates 30, 32, elements of the second or inner surfaces 40' , 42 ' of the plates will be designated by like primed reference numerals. Thus, it will be seen by viewing Figures 2-4, that plates 30 and 32 are shaped to provide unembossed or reference planar surfaces 50, 52 with aligned oppositely facing planar surfaces 50', 52', which bound openings 30a, 32a, 30b, 32b, 30c, and 32c; embossed, peripherally extending planar surfaces 60, 62 with aligned oppositely facing planar surfaces 60' , 62' ; a plurality of embossed outer grooves or valleys 70, 72 with aligned oppositely facing inner ribs 70', 72'; and a plurality of outer ribs 80, 82, which are disposed intermediate grooves 70 and 72, with aligned inner grooves or valleys 80', 82'. Planar surfaces 50, 52, and thus aligned surfaces 50', 52' include dividing surface portions, which, as shown only for the case of dividing surface portions 50a, 52a' in Figures 2 and 3, respectively, extend radially outwardly from between openings 30b, 30c, and 32b, 32c • towards peripherally extending surfaces 60, 62 and thus aligned surfaces 60', 62'. When unit 14 is assembled, peripherally extending planar surfaces 60' , 62 ' are disposed in sealing engagement, and separator 34 is arranged between plate surfaces 40', 42' in the manner shown in Figures 3 and 4, such that it sealingly engages with planar surfaces 50 ' , 52' in alignment with registration openings 30a and 32a, whereby to co-operate therewith to define registration opening 24 of unit 14, and such that it sealingly engages with dividing surface portion 52a' and its facing dividing surface portion, not shown, to separate an oil inlet opening 84 of the unit bounded by aligned openings 30b, 32b from an oil outlet opening 86 of the unit bounded by aligned openings 30c, 32c. Thus, oil entering unit 14 via inlet opening 84 is directed to flow once about the interior of the unit along a first flow path defined by inner grooves 80', 82' and inner ribs 70', 72' for discharge through outlet opening 86. When units 14 are assembled and bonded together in a stacked relationship, all of surfaces 40 of plates 30 face in one direction and all of surfaces 42 of plates 32 face in an opposite direction with plates 30, 32 of a pair of adjacent units having their outer surfaces 40, 42 disposed in engagement for co-operation to define a second or water flow path defined by outer grooves 70, 72 and outer rib portions 80, 82. As best seen in Figures 4 and 5, crests 80a, 82a of outer ribs 80, 82 are disposed or arranged vertically intermediate the troughs 70a, 72a of outer grooves 70, 72 and planar surfaces 50, 52, and such outer ribs are provided with a plurality of integrally formed projections 100, 102 whose crests 100a, 102a are disposed to lie essentially coplanar with planar surfaces 50, 52. Thus, when adjacent units 14 are disposed in a stacked relationship with their respective openings 24, 84 and 86 disposed in alignment, the crests 80a, 82a of outer ribs 80, 82 of adjacent units are disposed in a spaced relationship and crests 100a, 102a of projections 100, 102 of adjacent units are disposed in engagement. Preferably, at least one projection is provided on each of outer ribs 80, 82 with the longest of such outer ribs having multiple uniformly spaced projections and .with the projections on adjacent outer ribs being staggered or offset relative to one another, as shown in Figures 2 and 3. Projections 100, 102 are also preferably slightly elongate in a direction lengthwise of their associated ribs 80, 82, such that engaged projections assume an X-shaped pattern, as best shown in Figure 6, when a stack of units 14 is viewed in plan. Spacing between the crests 80a, 82a of outer ribs 80, 82 provides for a greater flow cross-sectional area for water flowing within canister 12 between adjacent units 14 than the flow cross-sectional area provided for oil flowing within such adjacent units, and as a result, the pressure drop of water passing through cooler 10 may be substantially reduced, as compared to the pressure drop of oil passing through such cooler. The grooves and ribs may be of like cross-section and have their troughs and crests of like radius. However, it is contemplated that the radius of curvature of the crests 80a, 82a of the outer ribs 80, 82 may exceed the radius of curvature of the troughs 70a, 72a of the outer grooves 70, 72 with a view towards forming of projections 100, 102 with a minimum reduction in plate thickness and thus strength adjacent the projections. Unequal radius of curvature of the crests and troughs of the outer ribs and grooves necessarily results in their being unequal radius of curvature of the crests and troughs of the inner ribs and grooves-, and this in turn offers a further mechanism for producing variations in the cross-sectional areas of the first and second flow paths. An increase in the cross-sectional area of the second flow paths relative to the first flow paths further allows for an increase in the density of the ribs and grooves present on a given unit of surface area of plates 30, 32, thereby serving to further increase mixing or turbulence to which oil is exposed without resulting in an oil cooler having unacceptable water pressure drop performance. It will also be understood that the arcuate lengths of the grooves and ribs may be varied to vary operating conditions of the circumferential flow oil cooler depicted in the drawings. Changes in arcuate lengths combined with changes in density of the grooves and ribs may be tailored to achieve desired results. Thus, if the number of grooves and ribs is held constant, decreases in their arcuate lengths would tend to decrease the oil pressure drop, while the pressure drop of water would tend to remain relatively constant. On the other hand, if the arcuate lengths of the grooves and ribs is maintained constant and their number is increased, the pressure drop of the oil tends to increase, while the pressure drop of water would tend to remain the same. Once a desired water pressure drop is established, arcuate lengths and densities of the grooves and ribs may be determined to provide an oil cooler having desired characteristics. Operating characteristics of an oil cooler can also be varied for any given installation axial length or envelope by, for instance, decreasing the number of heat exchange units in a stack as an incident to increasing the individual axial length of each unit in a manner which increases the cross-sectional area of the second flow path without change of the cross-sectional area of the first flow path; or by, for instance, maintaining the number of units in a stack constant and increasing or decreasing the heights of the outer ribs to vary the cross-sectional areas of both of the first and second flow paths. By way of example, an oil cooler 10 employing a stack of thirteen heat transfer units formed in accordance with the present invention has an overall length of about 3 centimetres (1.2 inches) . The cooler was found to have water and oil pressure drops of about 20 k Pa (three pounds) and 100 k Pa (fifteen pounds), respectively. In accordance with the illustrated and preferred form of the present invention, the grooves and ribs of the plates of each heat exchanger unit extended generally along involute curves, spirals, etc. It is to be understood, however, that the invention is not limited to the use of involute curves and may have utility when the flow path is defined by straight co-operating grooves and ribs. Also, although a circumferential flow heat exchanger is shown in the drawings, it will be appreciated that a linear flow heat exchanger could be produced in accordance with this invention. In a linear flow heat exchanger, the plates would- be straight with the ribs and grooves arranged at an oblique angle to the longitudinal direction of the heat exchanger.

Claims: WHAT IS CLAIMED IS: 1. A heat exchange unit for a heat exchanger comprising: first and second plates having oppositely facing outer surfaces, and facing inner surfaces, said plates having elongate outwardly opening outer grooves and elongate outer ribs arranged between said outer grooves and extending co- directionally therewith, said outer grooves forming inwardly disposed ribs in said inner surfaces arranged in an engaged crossing relationship, said outer ribs forming inwardly disposed inner grooves crossing to define a first flow path, said plates having flow inlet and outlet openings communicating with opposite ends of said first flow path, said outer ribs having crest portions with outwardly disposed projections formed therein, such that when a plurality of said units are arranged in a stack with said first plate outer surfaces in abutting engagement with said second plate outer surfaces, said outer ribs and outer grooves of said first and second plates co-operate to define second flow paths having cross-sectional flow areas exceeding that of said first flow paths. 2. A heat exchange unit as claimed in claim 1, wherein said projections are elongate lengthwise of said outer ribs and arranged to cross mating projections on outer ribs of an adjacent unit with which they engage. 3. A heat exchange unit as claimed in claim 1, wherein said plates are annular in shape with inner and outer sealed peripheral edges, said ribs and grooves extending generally along involute curves. 4. A heat exchange unit as claimed in claim 3 wherein the flow inlet and outlet openings are adjacent, and further comprising a radial flow separator located therebetween in sealing engagement with the plate inner surfaces. 5. A heat exchanger comprising: a stack of heat exchange units as claimed in claim 1 arranged with the flow inlets of all units in communication with each other, and the flow outlets of all units in communication with each other. 6. A heat exchanger as claimed in claim 5 and further comprising a housing means for receiving said stack of units and having a first flow means communicating with said first flow paths and a second flow means communicating with said second flow paths. 7. A heat exchanger as claimed in claim 5, wherein the plates of each unit are annular in shape with inner and outer sealed peripheral edges, the outer surfaces of said plates being formed with inner planar portions apertured to afford fiow communication between said first flow paths of adjacent units and having facing surfaces thereof fluid sealed relative to one another to cause flow to follow along said first flow paths; and said projections having engagement surfaces disposed to lie essentially co-planar with said planar portions. 8. A heat exchanger as claimed in claim 7, wherein said projections are elongate and disposed in a direction extending lengthwise of said outer ribs. 9. A heat exchanger according to claim 8, wherein all of said outer ribs have at least one projection formed integrally therewith. 10. A heat exchanger according to claim 9, wherein said outer grooves and outer ribs are essentially uniformly spaced and - extend generally along involute curves away from said planar portions towards said outer peripheral edges.

Inventors: BENSON JEFFREY P, MEEKINS KRIS J, BENSON, JEFFREY, P., MEEKINS, KRIS, J.
Applicants: LONG MFG LTD, LONG MANUFACTURING LTD.
Application year: 1992
Main classification: F28D9
IPC codes: F28D9, F28F3