TECHNICAL FIELD
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The invention relates to a heat exchanger. In particular, the invention relates to the heat exchanger for a motor vehicle.
BACKGROUND OF THE INVENTION
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The present invention relates to the field of heat exchanger and in particular to heat exchangers intended to be traversed by a fluid under high pressure. In this respect, the invention relates more particularly to air conditioning gas coolers, inner gas coolers or evaporators capable of being traversed by a refrigerant fluid in the supercritical state, as is the case for natural gases such as carbon dioxide, also known as CO2 or R744. Such heat exchangers find particular application in motor vehicles.
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A known fluid refrigerant circuit forms a closed loop in which the refrigerant fluid flows in order to dissipate or collect calories through heat exchangers. The heat exchanger comprises the manifold to connect said heat exchanger to the fluid refrigerant circuit, said manifold linking pipes from the fluid refrigerant circuit to the heat exchanger core, in order for the refrigerant fluid to flow through heat exchanger tubes.
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In a fluid refrigerant circuit traversed by a refrigerant fluid in the supercritical state, this refrigerant fluid remains essentially in the gaseous state and under a very high pressure, which is usually around 100 bars. As a result, heat exchangers must be able to withstand such high pressure, the recommended burst pressure being generally three times the value of the nominal operating pressure, burst pressure thus reaching around 300 bars.
SUMMARY OF THE INVENTION
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An object of the invention is a heat exchanger comprising a first manifold, a second manifold, and a plurality of flat tubes connecting the first manifold with the second manifold; the plurality of flat tubes being arranged alternatingly with a plurality of heat dissipation elements, wherein each flat tube is arranged to meander between respective heat dissipation elements with its co-planar sections, with the co-planar sections being connected to each other with integral reversal elements arranged beyond the heat dissipation elements, wherein the first manifold includes a first header plate, a first distribution plate, a first intermediate plate and a first cover stacked on top of each other, wherein the second manifold includes a second header plate, a second distribution plate, a second intermediate plate and a second cover stacked on top of each other, wherein flat tubes pass through the first and second header plates and terminate in first and second distribution plates without reaching the first and second intermediate plates.
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In one option, each of the first and second intermediate plates has a channel opening extending along the first and second manifolds, respectively.
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In one option, the first and second intermediate plates are thicker than the first and second distribution plates.
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In one option, the first and second intermediate plates are at least twice times thicker than the first and second distribution plates.
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In one option, each of the first and second distribution plates includes a plurality of distribution openings within which the flat tubes terminate.
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In one option, the flat tubes penetrate through less than a half of a height of the respective distribution openings.
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In one option, the distribution openings have a cross-section larger than cross-section of the flat tubes so that there is no direct contact there-between.
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In one option, the first and second distribution plates are of the same thickness as the first and second cover plates.
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In one option, the first and second header plates include a plurality of crimping elements bent onto respective first and second cover plates from both sides of each manifold in parallel pairs, wherein for each flat tube there is a corresponding adjacent pair of crimping elements.
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In one option, the first and the last pair of crimping elements are wider than the crimping elements between them.
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In one option, the last pair of crimping elements is wider than the first pair of crimping elements.
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In one option, wherein the first and second manifolds include respectively a first and a second connector block, wherein the first and second distribution plates include respectively a first and a second connector openings configured to communicate fluidly the first and second connector blocks with respective manifolds, wherein the first and second connector openings are narrower than the distribution openings.
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In one option, the first and second connector openings are elongated along the extension direction of the first and second manifolds.
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In one option, the first and second manifolds include respectively a first and a second connector block, wherein each connector block includes two pairs of block crimping tabs bent onto respective covers, wherein the first and second distribution plates have positioning protrusions extending between said pairs.
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In one option, the flat tube is extruded and includes a plurality of micro channels for a heat exchange medium.
BRIEF DESCRIPTION OF DRAWINGS
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The present invention will be described in greater detail below with reference to the drawings. In the drawings:
- Fig. 1 shows a heat exchanger in a perspective view;
- Fig. 2 shows a top portion of the heat exchanger with an exploded header box;
- Fig. 3 shows a flat tube;
- Fig. 4 shows a top portion of the heat exchanger without covers on the manifolds;
- Fig. 5 shows a cross-section of a manifold; and
- Fig. 6 shows a cross-section of the connector blocks 41.
DETAILED DESCRIPTION OF THE INVENTION
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Fig. 1 shows a heat exchanger 100 in a perspective view. The heat exchanger 100 is intended to be used in a fluid refrigerant circuit. The heat exchanger 100 comprises a header box 1 and heat exchange tubes 200. The heat exchanger 100 can be used as an evaporator, as a condenser or as a gas cooler.
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The header box 1 extends along a first axis X and a second axis Y perpendicular to the first axis X, the first axis X and the second axis Y defining a plane XY.
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The heat exchanger tubes 200 extend away from and towards the header box 1 along a third axis Z, said third axis Z being perpendicular to the plane XY.
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The header box 1 comprises a first manifold 10, a second manifold 20 and a connector 30. The connector 30 is intended to fluidically connect the header box 1 to the fluid refrigerant circuit. The connector 30 comprises a first pipe 39 and a second pipe 40, the first pipe 39 being connected to the first manifold 10 and the second pipe 40 being connected to the second manifold 20.
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The connector 30 comprises attaching elements 35 grabbing the first manifold 10 and the second manifold 20 of the header box 1, thus securing the attachment of the connector 30 onto the header box 1, said securing being needed due to the very high pressure in the fluid refrigerant circuit.
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The header box 1 also comprises a gap 50 between the first manifold 10 and the second manifold 20, said gap 50 extends all along the header box 1 along the first axis X. This configuration allows the header box 1 to limit the heat exchange between the first manifold 10 and the second manifold 20. In other words, the gap 50 reduces the thermal coupling of the first manifold 10 and the second manifold 20. Thus, this configuration allows an improved efficiency of the heat exchanger 100.
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Fig. 2 shows an example of a header box 1 according to the invention. The first manifold 10 comprises a first cover 14, a first intermediate plate 13, a first distribution plate 12 and a first header plate 11. Similarly, the second manifold 20 comprises a second cover 24, a second intermediate plate 23, a second distribution plate 22 and a second header plate 21. In this example, the first cover 14 is separated from the second cover 24. The first header plate 11 is also separated from the second header plate 21. In this context, separated means that there is no direct contact between those parts, the latest being thermally decoupled.
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The first intermediate plate 13 is localized between the first header 11 and the first cover 14 of the first manifold 10. In a similar way, the second intermediate plate 23 is localized between the second header plate 21 and the second cover 24 of the second manifold 20.
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Each manifold 10, 20 comprises crimping elements 15 extending from the first header plate 11 or the second header plate 21 to the first cover 14 or the second cover 24, respectively. These crimping elements 15 secure the assembly of the components of the first manifold 10 and the second manifold 20 by grabbing the corresponding cover 14, 24, in order for said assembly to withstand the very high pressure inside the heat exchanger 100.
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The crimping elements 15 are regularly interspaced between each other along the first axis X of the header box 1, thus allowing an equal securing of the assembly of the components from the header box 1.
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The crimping elements 15 are teeth, but they can be replaced, according to the invention, by any fixation mean, for example screws, blots, or rivets.
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Fig. 3 shows a flat tube 200 for the heat exchanger 100. The flat tube 200 may comprise first tubular element 211, a second tubular element 212, a third tubular element 230 and a fourth tubular element 240. The third tubular element 230 and a fourth tubular element 240 are essentially the same as the first tubular element 211 and the second tubular element 212. Each tubular element 211, 212, 230, 240 may comprise two juxtaposed longer walls 213 having essentially flat surface. In other words, the longer walls 213 are substantially identical wall portions arranged in parallel and facing each other with their respective flat surfaces. The tubular elements 211, 212, 230, 240 may also comprise two shorter walls 214 connecting the longer walls 213 to form a closed profile, and an axis of elongation. The flat tube 200 may further comprise two open ends 219. The term open end refers to a terminal ends of the tubular element 211, 212, 230, 240 which allows the fluid to enter or exit the entire flat tube 200.
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The open ends 219 of the flat tube 200 are arranged on the same side and at the same level, whereas the longer walls 213 of the adjacent tubular elements 211, 212 are arranged so that their flat surfaces are coplanar with respect to each other. In order to achieve such configuration, the flat tube 200 may further comprise at least one reversal element 215 configured to fluidly connect the first tubular element 211 and the second tubular element 212, with similar reversal element connecting the third tubular element 230 and the fourth tubular element 240. The reversal elements 215 may be made integral with the rest of the flat tube 200.
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The reversal elements 215 may thus be interpreted as any integral section of the flat tube 200 which is configured to change the intended flow of the fluid within the flat tube 200. In particular, the reversal elements 215 may be configured to provide the counter flow of the fluid within two neighboring straight sections of the flat tube 200, i.e. the first tubular element 211 and the second tubular element 212, et cetera.
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The reversal element 215, may comprise, inter alia, a first twisted section 215A and at least one second twisted section 215B. A term "twisted" refers to essentially helical or semi-helical shape of the section. The twisted section 215A, 215B allow smoother transition of the channel of the fluid, without drastic change of the hydraulic diameter within the reversal element 215. Moreover, if the flat tube 200 is an extruded flat tube comprising micro channels, said channels remain their desired shape.
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The integrity between the tubular elements 211, 212, 230, 240 and the reversal element 215 may be described, so that the first twisted section 215A may protrude directly from first tubular element 211, and the second twisted section 215B may protrude directly from the second tubular element 212. The twisted sections 215A, 215B may be then joined together to form a fluidal communication between the neighboring tubular elements 211, 212, 230, 240. Naturally, it is also true that the second twisted section 215B may protrude directly from the first twisted section 215A, so other ways of describing the twisted sections 215A 215B are also possible. For example, the first twisted section 215A may protrude in helical manner in the counterclockwise direction with respect to the first tubular element 211, yet with respect to the second twisted section 215B it may protrude in a clockwise direction. Similarly, the second twisted section 215B may protrude in helical manner in the counterclockwise direction with respect to the second tubular element 212, yet with respect to the first twisted section 215B it may protrude in a clockwise direction.
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The reversal element may comprise an essentially U-shaped section 216 that connects the first twisted section 215A and the second twisted section 215B. The U-shaped section 216A may be of relatively small curvature, or of bigger curvature. The smaller curvature of the U-shaped section is formed to the extent that is allowed by mechanical properties of the material from which the flat tube 200 is made of. Small curvature allows packing the consecutive tubular elements 211, 212, 230, 240 closer to each other, which improves packaging. The bigger curvature on the other hand facilitates thermal decoupling of the consecutive tubular elements 211, 212, 230, 240 and allows relatively smoother transfer of the fluid therein.
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As mentioned in previous paragraphs, the second twisted section 215B protrudes helically in one direction, wherein the first twisted section 215A protrudes helically in the same direction as the second twisted section 215B. Alternatively, the second twisted section 215B protrudes helically in one direction, wherein the first twisted section 215A protrudes helically in different direction than the second twisted section 215B. The helical direction of protrusion means that the sidewalls 214 remain substantially equidistant with respect to each other, but the axis of elongation of the tubular element 211, 212, 230, 240 is disordered.
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The reversal elements 215 allow to change the intended flow direction of the fluid, without the necessity to provide additional manifolds. It may significantly reduce the overall cost and weight of the heat exchanger 100 while keeping the desired packaging. The reversal elements 215 having the twisted sections 215A, 215B further allow to form the substantially equidistant path for the fluid throughout the flat tube 200, unlike in the flat tube comprising direct U-turn, wherein the sidewalls 214 are at some point of different length.
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Each flat tube 200, including both the tubular element 211, 212, 230, 240 and the reversal elements 215 may comprise a set of micro channels 217 extending between the open ends of the flat tube 200. Naturally, the micro channels are continuous throughout the reversal elements 215, i.e. the micro channels in the reversal elements are configured to link fluidly the corresponding micro channels in respective tubular elements 211, 212, 230, 240. The tubular elements 211, 212, 230, 240 may be of the same size, i.e. their external dimensions such as: width, measured as the distance between the outer faces of the shorter walls 214; the length- measured along the longer walls 213, as the distance between the open ends of the flat tube; or as the height, measured as the distance between the outer faces of the longer walls of the same tubular element 211, 212, 230, 240.
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The flat tube 200 may be implemented in a heat exchanger 100. The exchanger 100 may comprise, inter alia: the plurality of flat tubes 200 which arranged in a stacking direction, wherein the stacking direction is perpendicular to the flat surfaces of the flat tubes 211, 212, 230, 240.
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Fig. 4 shows a top portion of the heat exchanger without covers 14, 24 on the manifolds 10, 20, with Fig. 5 showing a cross-section of a manifold 20. In one embodiment, the heat exchanger 100 comprises a first manifold 10, a second manifold 20, and a plurality of flat tubes 200 connecting the first manifold with the second manifold. The plurality of flat tubes 200 is arranged alternatingly with a plurality of heat dissipation elements 150. Each flat tube 200 is arranged to meander between respective heat dissipation elements 150 with its co-planar sections 211, 212, 213, 214, with the co-planar sections 211, 212, 213, 214 being connected to each other with integral reversal elements 215 arranged beyond the heat dissipation elements 150. The first manifold 10 includes a first header plate 11, a first distribution plate 12, a first intermediate plate 13 and first cover 14 stacked on top of each other. The second manifold 20 includes a second header plate 21, a second distribution plate 22, a second intermediate plate 23 and a second cover 24 stacked on top of each other. The flat tubes 200 pass through the first and second header plates 11, 21 and terminate in first and second distribution plates 12, 22 without reaching the first and second intermediate plates 13, 23.
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The flat tube 200 can be extruded and include a plurality of micro channels 217 for a heat exchange medium.
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Each of the first and second intermediate plates 13, 23 can have a channel opening 30 extending along the first and second manifolds 10, 20, respectively.
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The first and second intermediate plates 13, 23 can be thicker than the first and second distribution plates 12, 22. This thickness can be measured parallel the third axis Z.
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The first and second intermediate plates 13, 23 can be at least twice times thicker than the first and second distribution plates 12, 22. This thickness can be measured parallel the third axis Z.
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Each of the first and second distribution plates 12, 22 can include a plurality of distribution openings 31 within which the flat tubes 200 terminate.
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The flat tubes 200 can penetrate through less than a half of a height of the respective distribution openings 31. The penetration can be measured parallel the third axis Z.
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The distribution openings 31 can have a cross-section larger than cross-section of the flat tubes 200 so that there is no direct contact there-between.
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The first and second distribution plates 12, 22 can be of the same thickness as the first and second cover plates 14, 24. This thickness can be measured parallel the third axis Z.
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The first and second header plates 11, 21 can include a plurality of crimping elements 15 bent onto respective first and second cover plates 14, 24 from both sides of each manifold 10, 20 in parallel pairs, wherein for each flat tube 200 there can be a corresponding adjacent pair of crimping elements 15.
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As can be seen in Fig. 1, the first and the last pair of crimping elements 15 can be wider than the crimping elements 15 between them. This can be measured along the first axis X.
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The last pair of crimping elements 15 can be wider than the first pair of crimping elements 15.
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Fig. 6 shows a cross-section of the connector blocks 41, 42.
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The first and second manifolds 10, 20 can include respectively a first and a second connector block 41, 42, wherein the first and second distribution plates 12, 22 can include respectively a first and a second connector openings 43, 44 configured to communicate fluidly the first and second connector blocks 41, 42 with respective manifolds 10, 20. The first and second connector openings 43, 44 can be narrower than the distribution openings 31. This can be measured along the second axis Y.
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The first and second connector openings 43, 44 can be elongated along the extension direction of the first and second manifolds 10, 20.
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Each connector block 41, 42 can include two pairs of block crimping tabs 45 bent onto respective covers 14, 24, wherein the first and second intermediate plates 13, 23 have positioning protrusions 46 extending between said pairs.