EP1248063B1 - Heat exchanger - Google Patents

Abstract

Heat exchanger, especially an evaporator in an air-conditioning system of a motor vehicle, used for transferring heat between a first and a second heat medium comprises a number of flat tubes (4, 4'') forming a block through which the first heat medium flows. The flat tubes are arranged in parallel so that channels for the second heat medium (3) entering at one end (6) of the block are formed in between adjacent flat tubes. The flat tubes extend in the direction of the block depth (t) at least over a partial section at an angle ( alpha ) to the end surface of the block. Preferred Features: The angle is about 25-65, preferably 45 degrees . The flat tubes have an angled or rounded undulating cross-section. The flat tubes are made by extruding a light-weight sheet metal, especially aluminum or an aluminum alloy.

Description

The invention relates to an evaporator of a motor vehicle air conditioner with the features according to the preamble of claim 1. Such evaporators are e.g. from EP-A-0947792.

In motor vehicles, increasingly complex systems are used, so that an ever smaller proportion of the overall installation space available for the individual components is available. This applies in particular to the air conditioning systems, on the one hand, a high performance is required, while on the other hand, the space available for the required heat exchanger space is increasingly limited. This has a detrimental effect on the transmission performance, especially in evaporators of limited block depth.

Heat exchangers of the type mentioned have a substantially formed of parallel flat tubes block, wherein the flat tubes of a slightly evaporating heat medium, namely a refrigerant, flows through. This block is traversed transversely to its end face by a second medium, usually air, wherein on the surface of the flat tubes, a heat exchange between the first and the second heat medium takes place. In evaporators, the cold produced by the evaporation process of the first heat medium is conducted through the metallic wall of the flat tubes to the outer surface and to the air flowing past transferred, whereby this cooled air is used for air conditioning of the vehicle interior.

The volume of the heat exchanger is composed essentially of the end face and the block depth, wherein the block depth substantially corresponds to the depth of the flat tubes of one or more rows of tubes. One way to reduce the volume of construction is to reduce the block depth, which shortens the path of the air flowing through the block in the direction of the block depth. To improve the heat transfer, a variety of solutions are known, which are based essentially on an increase in the heat-transmitting surface. These are on the surface of the flat tubes, which faces the heat medium with the lower heat capacity, so here on the air side, surface enlarging facilities such as fins, corrugated fins or the like. Provided. However, such measures are not sufficient with correspondingly compact designs of the heat exchanger and high power requirement.

The invention has for its object to provide an evaporator, in which the required volume of construction is reduced.

This object is achieved by an evaporator with the features of claim 1.

For this purpose, it is proposed to arrange in a heat exchanger of the type mentioned, the flat tubes in the direction of the block depth at least over a section at an angle to the end face of the block. The angle is expediently approximately in a range between 25 ° and 65 ° and is in particular about 45 °. The channels formed between the flat tubes for the air flowing through are rotated approximately at the same angle, so that the flow direction of the air between the flat tubes has a component inclined to the end face. By taking place opposite the direction of flow deflection of the flow direction in the region of the flat tubes, a detour is imposed on the air flow within the heat exchanger block, as a result of the air flow with an extended path on the surfaces of the flat tubes passes. By extending the path and the associated longer contact time of the air in an evaporator more heat can be withdrawn. At a given by the system requirements heat transfer performance therefore the available space can be better used and in particular the block depth can be reduced.

In an advantageous variant or in combination with an inclined position, the flat tubes have a cross-section approximately in the form of a wave, with the convex side of a shaft of a flat tube engaging in the concave side of the corresponding shaft of the adjacent flat tube at a distance. This results in the distances between the adjacent flat tubes wavy flow channels for the air with a correspondingly extended flow path based on the block depth. In an advantageous variant, the waveform is approximately angled, that is formed, for example, in staircase form. This allows a cost-effective production with simple means. In a further expedient variant, the waveform is rounded, whereby the flow resistance is kept low for the air flowing through the block. To further reduce the flow resistance is the Waveform formed such that the side surfaces of the flat tubes in the region of at least one longitudinal edge and in particular in the region of both longitudinal edges are approximately perpendicular to the end face. The inflowing and possibly also the outflowing air is thereby led straight into the heat exchanger block or let out of it, wherein a deflection takes place only within the heat block under aerodynamically well-defined conditions with low flow losses.

In an advantageous development, the side surfaces of the flat tubes have means for enlarging the heat-transmitting surface and / or the flow path. In an expedient variant, longitudinal ribs lying on the side surfaces of the flat tubes in the direction of their longitudinal axis are provided and arranged offset relative to one another such that the longitudinal ribs of a flat tube engage in the intermediate spaces of the longitudinal ribs of the adjacent flat tube on its adjacent side surface. The resulting mutual engagement of the longitudinal ribs generates a further approximately wave-shaped deflection of the air flow along its path in the depth direction of the heat exchanger block in conjunction with an enlargement of the heat-transferring surface. As a result, a further improvement of the heat transfer performance and thus based on a predetermined heat transfer performance a further reduction of the installation space is possible.

In an expedient variant discrete projections are arranged on the side surfaces of the flat tubes, which also mutually engage in the intermediate spaces between the projections of the adjacent tube. The projections must be surrounded on the outside by the air.

This creates a multiple division and merging of the air flow. The formation of a laminar flow is prevented and achieved a good mixing with a concomitant good heat transfer. The projections also increase due to their Geome-trie conditionally the heat-transferring surface. Furthermore, there is a flow deflection and thus a flow path extension with a component which is parallel to the longitudinal axis of the flat tubes. The said projections expediently have an aerodynamic cross-section, for example in the form of an oval or an ellipse, whereby the flow resistance for the air flowing through is reduced. In an advantageous variant, the projections extend from one outer side of a flat tube to the adjacent outer side of the adjacent flat tube, whereby they also serve as spacers. To simplify the production and to improve the heat transfer struts may be provided which extend transversely through a plurality of flat tubes. A block of flat tubes is threaded onto these struts, the struts serve as an assembly aid and align the flat tubes against each other. In addition, the struts fulfill the function of the projections described above.

The mentioned variants of the surface and Strömungswegvergrößernden means are expediently made in one piece with a wall of the flat tube.

To further improve the heat transfer can be provided on the side surfaces of the flat tube peeled out of the material transverse ribs. These transverse ribs contribute to the increase in surface area, wherein the transverse ribs in the material composite are formed by the process of peeling out stay with the flat tube with a corresponding, correspondingly good heat transfer. As a further measure for improving the heat transfer, the transverse ribs may have an edge in waveform, wherein the waveform may be comparable to the serrated edge of a knife in the transverse rib plane. In another variant, the waveform of the edge is approximately perpendicular to the surface of the transverse rib, whereby this also has a strömungswegverlängernde effect.

In an advantageous development, the flat tubes are designed as multi-chamber tubes with individual channels for the first heat medium. By arranging a plurality of individual channels, on the one hand, the relative surface in contact with the first heating medium is increased, whereby an improved heat transfer is also made possible in this area. On the other hand, a complex flow guidance within the heat exchanger block is made possible by the plurality of separate channels. In an expedient variant, the flat tubes are made of a light metal sheet, whereby a cost-effective production is made possible even under high-volume conditions. Alternatively, the flat tubes are produced by extrusion or extrusion, including light metal and aluminum in particular not only because of the relatively low weight, but equally suitable both from manufacturing aspects and because of its good heat transfer properties.

Fig. 1

in einer schematischen Übersichtsdarstellung einen Wärmeübertrager am Beispiel eines Verdampfers;

Fig. 2

eine Querschnittsdarstellung durch einen Verdampfer mit wellenförmigen Flachrohren und Längsrippen;

Fig. 3

eine schematische Querschnittsdarstellung von Flachrohren mit gerundeter Wellenform;

Fig. 4

eine Variante der Anordnung nach Fig. 3 mit paarweise gegenüberliegenden Längsrippen;

Fig. 5

in einer perspektivischen Darstellung eine weitere Variante von Flachrohren mit Längsrippen und geschälten Querrippen;

Fig. 6

eine schematische Querschnittsdarstellung durch Rohre mit gegeneinander versetzt angeordneten Längsrippen;

Fig. 7

in einer perspektivischen Darstellung ein Flach-rohr mit aus seiner Oberfläche geschälten, gewellten Querrippen;

Fig. 8

eine Variante der Anordnung nach Fig. 7 mit einer Vielzahl von strömungsumleitenden Vorsprüngen;

Fig. 9

eine Querschnittsdarstellung durch ineinandergreifende Vorsprünge nach Fig. 8 zweier benachbarter Flachrohre;

Fig. 10

eine Prinzipdarstellung eines Querschnittes durch Flachrohre in Blechschalenbauweise mit durchlaufenden Streben.

Embodiments of the invention will be explained in more detail below with reference to the drawing. Show it:

Fig. 1

in a schematic overview representation of a heat exchanger using the example of an evaporator;

Fig. 2

a cross-sectional view through an evaporator with wave-shaped flat tubes and longitudinal ribs;

Fig. 3

a schematic cross-sectional view of flat tubes with rounded waveform;

Fig. 4

a variant of the arrangement of Figure 3 with pairwise opposed longitudinal ribs.

Fig. 5

in a perspective view of another variant of flat tubes with longitudinal ribs and shelled transverse ribs;

Fig. 6

a schematic cross-sectional view through tubes with mutually staggered longitudinal ribs;

Fig. 7

in a perspective view of a flat-tube with peeled from its surface, corrugated transverse ribs;

Fig. 8

a variant of the arrangement of Figure 7 with a plurality of Strömungsumleitenden projections.

Fig. 9

a cross-sectional view through interlocking projections of Figure 8 of two adjacent flat tubes ..;

Fig. 10

a schematic diagram of a cross section through flat tubes in sheet metal shell construction with continuous struts.

1 shows a schematic overview of a heat exchanger of an air conditioning system of a motor vehicle, using the example of an evaporator 1. A condenser belonging to the air conditioning system can also be designed according to the invention, described below. The evaporator 1 comprises a plurality of flat tubes 4, 4 ', which are substantially parallel to each other in the form of a block 5 summarized. The flat tubes 4, 4 'are connected at their two ends in each case with a collecting box 29, 30 flow-conducting. The upper collection box 29 is divided by a total of four partitions 31 into a total of four subspaces 38, while the lower collection box 30 is divided by a partition wall 32 into two subspaces 39. A slightly vaporizable first heat medium 2 flows through the flat tubes 4, 4 'along the arrows 27, wherein the arrangement of the partitions 31, 32 results in a flow through the flat tubes 4, 4' in the form of a countercurrent flow. Depending on the application, an embodiment of the evaporator 1 with another flow pairing, for example, a pure cross flow may be appropriate.

The block-shaped arrangement of the flat tubes 4, 4 'results in the region of their longitudinal edges 16 an end face 6, which lies in a plane E indicated by dashed lines. Perpendicular to the end face 6 or to the plane E, the block 5 has a block depth t. The block 5 is flowed through by a second flow medium 3 in the direction indicated by the arrow 7 flow direction, wherein the flow direction. 7 is substantially transverse to the end surface 6. The second heat medium 3 is the air to be cooled by the evaporator 5. When flowing through the block 5, the second heat medium 3 first enters into the block 5 in the region of the front longitudinal edges 16 and is then guided past the flat tubes 4, 4 'on their surfaces 17, 18 for heat exchange. Subsequently, the second heat medium leaves the evaporator 1 in the region of the rear longitudinal edges 17 of the flat tubes 4, 4 '.

Fig. 2 shows a detail of a cross-sectional view through a block 5 (Fig. 1), in which a plurality of mutually parallel flat tubes 4, 4 'is provided, in the direction of the block depth t in each case from a front longitudinal edge 16 to a rear longitudinal edge 17th extend. The flat tubes 4, 4 'extend in the direction of the block depth t in the region of their central portion at an angle α of about 45 ° to the end face of the block 5. Due to the inclination receives the second heat medium 3 between the flat tubes 4, 4' a deflected flow direction eighth having a component inclined to the end face 6 and transverse to the longitudinal axis 10. As a result, the flow path along the deflected flow direction 8 between the front longitudinal edge 6 and the rear longitudinal edge 17 becomes longer than the block depth t. The arrangement of a filling body 28 on the side of the outermost flat tube 4 "also ensures an adjacent flow on the outermost flat tube 12. The flat tubes 4, 4 ', 4" have in their cross-section an approximately angular waveform with one respective shaft 13 in the region of the front and the rear longitudinal edge 16, 17 on. The two shafts 13 are formed such that the two side surfaces 15, 18 of the flat tubes 4, 4 ', 4 "in the region of Longitudinal edges 16, 17 are approximately perpendicular to the end face 6. The flat tubes 4, 4 ', 4 "furthermore have longitudinal ribs 20, 20', 21, 21 'running approximately parallel to the longitudinal axis 10 on their two lateral surfaces 15, 17, which intermesh with one another at a distance described in more detail below in connection with FIG.

In the variant of flat tubes 4, 4 'shown in FIG. 3, these have in their cross-section shown a rounded waveform, each with a rounded shaft 13 in the region of the front and rear longitudinal edges 16, 17. In each case, the convex side 12 of a shaft 13 of a flat tube 4 engages in the concave side 14 of the corresponding shaft 13 of the adjacent flat tube 4 'at a distance. The air flowing in transversely to the plane E along the flow direction 7 is deflected between the flat tubes 4, 4 'in a flow direction 8 such that the flow direction 8 has a component inclined to the plane E.

The variant of flat tubes 4, 4 'shown in FIG. 4 has at its side surfaces 15, 15', 18, 18 'means 19 for enlarging the heat-transferring surface of the flat tubes 4, 4' and the flow path of the second heat medium 3. In the exemplary embodiment shown, the means 19 consist of a number of longitudinal ribs 20, 20 ', 21, 21' arranged parallel to the longitudinal axis 10 (FIGS. 1, 2). In the illustrated embodiment, the longitudinal ribs 20, 21 and the longitudinal ribs 20 ', 21' of the corresponding flat tube 4, 4 'arranged in pairs opposite one another. This results in the region of the longitudinal ribs 20, 21, or 20 ', 21', a thick area 36, while the flat tubes 4, 4 'in the area have a thin area 34 between them. The flat tubes 4, 4 'have an angled waveform, each having a central shaft tip 13. The waveform is symmetrical so that the front and rear longitudinal edges 16, 17 of the flat tubes lie on a line in the block depth direction indicated by an arrow 42. The front and rear sections of the flat tubes 4, 4 'on both sides of the shaft tip 13 are arranged obliquely with respect to the plane E, that mutually each one longitudinal rib 20', 21 engages in the opposite gap 35.

To reduce the flow resistance for the incoming second heat medium 3 along the flow direction 7, the flat tubes 4, 4 'in the region of their longitudinal edge 16 on a thin portion 34. As a result of the mutual engagement of the longitudinal ribs 20 ', 21 in the opposite intermediate spaces 35, a meander-shaped flow path which lengthens the flow path and is described in more detail in connection with FIG. 6 is formed.

The flat tubes 4, 4 'have an identical design, wherein by the inclined position with respect to the plane E despite the cost-saving identical design and the pairwise opposed longitudinal ribs 20, 21 and 20', 21 'their mutual engagement in the opposite spaces 35 is possible , In addition to the flow deflection in the region of the longitudinal ribs 20, 20 ', 21, 21' and the associated intermediate spaces 35 also leads the inclination of the flat tubes 4, 4 'to a combined increase in the flow path of the second heat medium 3 and to increase the heat-transmitting surface of the Flat tubes 4, 4 '.

5 shows in a perspective view schematically a variant of the arrangement according to FIG. 4 for an approximately rectangular arrangement with respect to the end face 6 in the region of the longitudinal edges 16, 17 (FIG. 2), with comparatively the embodiment of FIG Longitudinal ribs 20, 21 and 20 ', 21' are arranged in pairs. In order to enable their mutual engagement in the opposite intermediate spaces 35, the flat tubes 4, 4 'in the region of their front longitudinal edges 16 alternately each have a thick and a thin region 36, 34. At the longitudinal ribs 20, 20 ', 21, 21' distributed in the direction of the longitudinal axis 10 from the material of the flat tubes 4, 4 'peeled-out transverse ribs 23 are provided. The mounting position of the flat tubes 4, 4 'is selected with respect to the direction of the weight force 40 so that the transverse ribs 23 extend obliquely downwards in the direction of the force of gravity 40 and thus facilitate a drainage, for example, of condensed water.

6 shows a cross-sectional view of a further variant of flat tubes 4, 4 ', in which the associated longitudinal ribs 20, 21 or 20', 21 'are offset relative to one another. In this variant, the width difference between the respective thin and thick regions 34, 36 is kept low. As a result of the mutual engagement of the longitudinal ribs 21, 20 'in the opposite intermediate spaces 35, a meander-shaped air duct 37 is formed in which the flow direction of the second heating medium indicated by the arrows 8 alternately with a component lying in the plane E of the end surface 6 (FIG is charged. This will be an extension the flow path and an enlargement of the heat transferring surface achieved.

Fig. 7 shows a further embodiment of a flat tube 4, from the flat side surfaces 15, 18 transversely to the longitudinal axis 10 extending transverse ribs 23 are peeled out as a means 19 for enlarging the heat-transmitting surface. The transverse ribs 23 have a corrugated edge 24, wherein the corrugated edge 24 may be in the plane of the transverse ribs 23 or perpendicular thereto.

In the embodiment of a flat tube 4 shown in FIG. 8, means 19 for enlarging the heat-transferring surface in the form of projections 22 are provided on its side surfaces 15, 18. 9 shows, in a sectional illustration through the projections 22, that in the spaces between them further projections 22 'of a not shown, adjacent flat tube 4' engage. The projections 22, 22 'have to reduce the flow resistance on an aerodynamic cross-section, which is elliptical in the embodiment shown, but may also be oval, diamond-shaped or the like. The projections 22, 22 'create a mutual division and merging of the air flow along the arrows 8 for improved mixing and for improved heat transfer. The deflected flow direction 8 has a component which increases the flow path and which lies parallel to the longitudinal axis 10. In conjunction with an inclination of the flat tubes 4, 4 ', or a wave-like configuration according to the embodiments previously shown, the flow direction 8 may comprise components which lie in any direction with respect to the plane E, and whereby an adapted Extension of the flow path for the heat medium 3 is made possible.

The exemplary embodiments of flat tubes 4, 4 'shown in FIGS. 2 to 8 are manufactured in one piece from aluminum by means of extrusion and are designed as multi-chamber tubes with individual channels 26 for the first heat medium 2. For certain cross-sectional shapes and extruded flat tubes come into consideration. However, it may also be an embodiment made of sheet metal expedient, either as a tube with welded longitudinal seam or as disk elements formed from sheet metal shells.

An embodiment of the latter form is shown in Fig. 10 schematically in cross section. The flat tubes 4, 4 'are formed by two joined half-shells 43, 44 of sheet metal. The two half-shells 43, 44 are shaped such that in each case two chambers 45 are formed as channels 26 for the flow through the first heat medium 2. Depending on the application and training with one or more chambers 45 may be appropriate. The direction of the block depth t corresponding to FIG. 1 is indicated by the arrow 42. The flat tubes 4, 4 'extend with respect to the arrow 42 at an angle α of about 45 °. As a spacer and mounting aid for the flat tubes 4, 4 'and as a means 19 for increasing the heat-transmitting surface, a plurality of struts 41 are provided, which pass through the flat tubes 4, 4'. The struts 41 also form projections 22, 22 'in the sense of FIGS. 8 and 9, which extend from one side surface 15, 18 to the adjacent side surface 18', 15 '. To improve the heat transfer, the struts 41 both from the second heat medium 3 in the direction of arrows 8 as shown in FIG. 9 as Also flows through the first heat medium 2 within the channels 26 in the direction of the arrows 27 of FIG.

The illustrated variants of surface and Strömungswegvergrößernden means 19 in the form of longitudinal ribs 20, 20 ', 21, 21' and in the form of projections 22 and transverse ribs 23 are integrally formed with the respective walls 25 of the flat tubes 4, 4 '. The projections 22, in particular in connection with the sheet-metal shell construction shown in Fig. 10 can be integrally formed by embossing the half-shells 43, 44. However, it may also be a separate production and subsequent attachment, for example by cohesive connection appropriate.

Claims (16)

1. An evaporator of an air conditioning system in a motor vehicle for transferring heat between a first and a second heat medium (2, 3) having a number of flat tubes (4, 4') forming a block (5) through which the first heat medium (2) flows and which are positioned essentially parallel to one another thereby forming ducts for the second heat medium (3) which enters at a front face (6) of the block (5) between neighbouring flat tubes (4, 4'), the front face (6) lying at right angles to a direction of flow (7) of the second heat medium (3),
   characterised in that
   the flat pipes (4, 4') run along the depth of the block (t) at an angle (α) to the front face (6) of the block (5) over at least a part section, the angle (α) lying approximately in a range between 25° and 65°.
2. An evaporator in accordance with claim 1,
   characterised in that
   the angle (α) is approximately 45°.
3. An evaporator in accordance with claim 1 or 2,
   characterised in that
   the flat tubes (4, 4') have an approximately wave-shaped cross-section (11).
4. An evaporator in accordance with claim 3,
   characterised in that
   the wave shape is somewhat angular.
5. An evaporator in accordance with claim 3,
   c h a r a c t e r i s e d i n that
   the wave shape is rounded.
6. An evaporator in accordance with one of claims 3 to 5,
   characterised in that
   the wave shape is such that the lateral faces (15, 18) of the flat tube (4) lie adjacent to a longitudinal edge (16, 17) and in particular in immediate contact with both longitudinal edges (16, 17) approximately perpendicular to the front face (6).
7. An evaporator in accordance with one of claims 1 to 6,
   characterised in that
   the lateral faces (15, 15', 18, 18') of the flat tubes (4, 4') have means (19) of increasing the heat-transferririg surface and/or the flow path of the second heat medium (3).
8. An evaporator in accordance with claim 7,
   characterised in that
   the means (19) are formed in one piece with a wall (25) of the flat tube (4).
9. An evaporator in accordance with claim 7 or 8,
   characterised in that
   on two adjacent lateral faces (15', 18) the flat tubes (4, 4') have longitudinal ribs (20, 20', 21, 21') which are offset in relation to one another.
10. An evaporator in accordance with one of claims 7 to 9,
    characterised in that
    provided on the lateral faces (15, 15', 18, 18') are projections (22, 22'), in particular with an aerodynamic cross-section.
11. An evaporator in accordance with claim 10,
    c h a r a c t e r i s e d in that
    the projections (22, 22') run from one lateral face (18, 15) to the neighbouring lateral face (15' 18') of the subsequent flat tube (4, 4') and in particular are designed as struts (41) which pass through several flat tubes (4, 4').
12. An evaporator in accordance with claim 8 or 9,
    characterised in that
    provided on the lateral faces (15, 18) are transverse ribs (23) which are scooped out of the material of the flat tube (4).
13. An evaporator in accordance with claim 12,
    characterised in that
    the transverse ribs (23) have corrugated edges (24).
14. An evaporator in accordance with one of claims 1 to 13,
    characterised in that
    the flat tubes (4, 4') are designed as multi-chamber tubes with individual channels (26) for the first heat medium (2).
15. An evaporator in accordance with one of claims 1 to 14,
    characterised in that
    the flat tubes (4, 4') are made of a light sheet metal.
16. An evaporator in accordance with one of claims 1 to 14,
    characterised in that
    the flat tubes (4, 4') are made by the extrusion of a light metal, in particular aluminium or an aluminium alloy.

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