Abstract:
The invention provides a charge air cooler, especially for motor vehicles, having a finned-tube block. The finned-tube block includes flat tubes through which charge air can flow and at least one fin member attached to the flat tubes. At least one fin member includes rows of webs and web crosspieces, the rows offset relative to each other by a predetermined distance. At least one web and/or one web crosspiece possesses at least one vortex generator.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/245,233, filed Nov. 3, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates generally to charge air coolers and particularly to a charge air cooler for motor vehicles.  
           [0004]    2. Description of the Related Art  
           [0005]    A typical prior art air cooler is described in the Shell Lexikon Verbrennungsmotoren (Shell Dictionary of Internal Combustion Engines), supplement to ATZ (Automotive Engineering Journal) and MTZ (Engine Engineering Journal), series 33. It consists of a finned-tube block, which is connected to a charge air inlet chamber and to a charge air outlet chamber. In this arrangement, hot charge air can flow from an internal combustion engine of the motor vehicle through flat tubes of the finned-tube block. A large proportion of the heat is transferred to the ambient air via fins arranged between the flat tubes and subjected to the action of ambient air. Within the flat tubes, there is an internal fin member which possesses rows of webs and web crosspieces. The rows are curved in the manner of webbed fins and offset relative to one another by predetermined distances. This ensures mixing of the charge air within the flat tubes.  
           [0006]    A disadvantage of such a charge air cooler is that, within a particular row between two webs, a hot core flow remains behind in the region of the core of the flow, from which virtually no heat transfer to the internal fin member takes place. This occurs even though the charge air undergoes good heat transfer to the internal fin member in the boundary layer region. Overall, then, the actual heat transfer performance is less than the theoretically possible heat transfer performance.  
           [0007]    Another related reference is DE 196 54 367 A1 and its corresponding publication U.S. Pat. No. 6,070,616, which discloses a method for attaching vortex generators in the form of winglets to a thin metal sheet. The vortex generators are shaped from the thin metal sheet by massive forming.  
         SUMMARY OF THE INVENTION  
         [0008]    An object of the invention is to improve a charge air cooler of the type discussed above, in such a way that the heat exchange is improved over the entire flow profile and the hot core flow is passed to the internal fin member.  
           [0009]    According to the first embodiment of the invention, at least one web and/or one web crosspiece of the internal fin member introduced into the flat tubes possesses at least one vortex generator. As a result, improved mixing of the hot core flow with the boundary layer flow is achieved. This is accomplished by a transverse flow in which the heat of the core flow is no longer guided by the internal fin member and the boundary layer flow guided in isolation by the wall of the flat tube. That is, the boundary layer flow is deliberately broken up and mixed. In addition to the simple breaking-up of the boundary layer flow, lengthwise vortexes are formed by the vortex generators, especially by the winglets. This causes the mixing action to extend far into the core flow. This enables the heat of all the charge air to be removed more efficiently to the ambient air.  
           [0010]    In an another embodiment of the invention, the vortex generators are designed in the form of winglets, as a ramp or in the form of a tab. In these arrangements, the longitudinal axis of the winglets extends obliquely relative to the main flow direction of the charge air, in particular at an angle of approximately 15° to 45°. As a result of such an arrangement of the winglets and the adjustment of the angle of the oblique position, control can be selectively exerted on the shape of the lengthwise vortex and hence, on the mixing of the flow.  
           [0011]    In a further embodiment of the invention, consecutive webs in the main flow direction of the charge air have oppositely oriented winglets. As a result, after a lengthwise vortex with a particular direction of rotation is generated by a first winglet, a lengthwise vortex in the opposite direction is generated at the next winglet.  
           [0012]    This further increases the efficiency of mixing.  
           [0013]    In another embodiment of the invention, the winglets are arranged in pairs and extend in opposite directions obliquely to the main flow direction of the charge air, extending away from one another in the main flow direction of the charge air. The winglets are produced by shaping the webs and/or web crosspieces.  
           [0014]    In a further embodiment of the invention, every second web of a row has a winglet oriented in the same direction. This is particularly beneficial in regards to manufacting. It allows one row at a time to be demolded in parallel and hence, guarantees the simplest and most cost-effective design possible for the internal fin members.  
           [0015]    In another embodiment of the invention, the vortex generator is designed in the form of a ramp inclined obliquely relative to the main flow direction of the charge air. In particular, the incline is at an angle of approximately 20° to 30°. The air flow is deflected upward and downward by the ramp. In addition, a vortex flow with a significant transverse component is generated. This transverse component prevents the formation of a continuous core flow.  
           [0016]    In a further embodiment of the invention, ramps ascending in the main flow direction of the charge air are followed by ramps descending in the main flow direction of the charge air. As a result, the air flow, as it passes through the fin member, is alternately deflected upward with one component and downward with the next component. This results in further turbulence and reduction of a continuous core flow.  
           [0017]    Examples of embodiments of the invention are shown in the drawings and are described in detail below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 shows a perspective, sectional view of a charge air cooler;  
         [0019]    [0019]FIG. 2 shows a perspective, partial sectional view of a flat tube with internal fin members introduced therein;  
         [0020]    [0020]FIG. 3 shows a sectional representation of a vortex generator, perpendicular to its longitudinal axis;  
         [0021]    [0021]FIG. 4 shows a sectional representation of a vortex generator along its longitudinal axis;  
         [0022]    [0022]FIG. 5 shows a perspective view of an internal fin member with vortex generators designed as ramps;  
         [0023]    [0023]FIG. 5 a  shows a lateral view of an internal fin member according to FIG. 5;  
         [0024]    [0024]FIG. 5 b  shows a front view of an internal fin member according to FIG. 5 a;    
         [0025]    [0025]FIG. 5 c  shows a plan view of an internal fin member according to FIG. 5 a;    
         [0026]    [0026]FIG. 5 d  shows a lateral view of the back of an internal fin member according to FIG. 5 a;    
         [0027]    [0027]FIG. 6 shows a detail view of a ramp according to FIG. 5;  
         [0028]    [0028]FIG. 7 shows a detail view of a ramp according to FIG. 5 provided with a passage aperture;  
         [0029]    [0029]FIG. 8 shows a detail view of a vortex generator formed by a tab;  
         [0030]    [0030]FIG. 9 shows a detail view of a vortex generator formed by a box-shaped ramp; and  
         [0031]    [0031]FIG. 10 shows a detail view of a vortex generator formed by a rounded hollow section. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    [0032]FIG. 1 shows a perspective, sectional view of a charge air cooler  10 . This charge air cooler  10  comprises a finned-tube block  12 , which is connected to a charge air inlet chamber  14  and to a charge air outlet chamber (not shown). The finned-tube block  12  comprises flat tubes  16 , between which fins  18  are arranged in the form of webbed fins or corrugated fins. The fins  18  are soldered to the flat tubes  16 . Charge air from an internal combustion engine (not shown) of a motor vehicle flows from the charge air inlet chamber  14  through the flat tubes  16  to the charge air outlet chamber. Perpendicular to this charge air flow, the fins  18  are subjected to the action of ambient air  20 . Because the charge air has a significantly higher temperature than the ambient air  20 , heat transfer takes place from the charge air to the ambient air  20 .  
         [0033]    Internal fin members  22  are arranged within the flat tubes  16  and soldered thereto. As is shown in FIG. 2, these are curved in the manner of webbed fins and comprise a plurality of rows  24  to  38 . They are each arranged perpendicularly to the main flow direction  40  of the charge air and are arranged offset relative to one another. The individual rows  24  to  38  each comprise webs  42  and web crosspieces  44 . The web crosspieces  44  extend substantially parallel to the wide sides  46  of the flat tubes and the webs  42  substantially perpendicularly to the latter.  
         [0034]    When charge air flows through the flat tubes  16 , a core flow forms within each row  24  to  38  of the internal fin members  22  and is surrounded by a boundary layer flow existing in the region of the walls. Because of the insulation provided by the boundary layer flow, the core flow has a significantly higher temperature level in comparison with the walls.  
         [0035]    For improved mixing of the core flow with the boundary layer flow, the webs  42  have vortex generators  48  with a beading-like design arranged approximately centrally on their surfaces. The longitudinal axis  50  of the vortex generators  48  are inclined at approximately 45° relative to the main flow direction of the charge air. Every second web  42  of the first rows  24  and  32  possesses vortex generators  48 . The vortex generators  48  are formed from the material by shaping at the same angle of inclination and in the same direction. The rows  26  and  34 , likewise possess a vortex generator  52  at every second web  42 . These are shaped from the material in the opposite direction of the vortex generators  48  and are also set obliquely at an angle approximately 45° in the opposite direction.  
         [0036]    [0036]FIG. 3 shows a sectional view through a vortex generator  48  perpendicular to its longitudinal axis  50  while FIG. 4 shows a view along its longitudinal axis. From these figures, it can be seen that the vortex generators are produced, simply by shaping the material and that they possess a continuous surface. Thus, a flow from one side of the material through the region of the vortex generators to the other side of the material is excluded.  
         [0037]    By means of the vortex generators  48 ,  52 , an improved mixing of the hot core flow with the boundary layer flow is achieved. Thus, the heat of the core flow is no longer guided by the internal fin member and the boundary layer flow in isolation by the wall. That is, the boundary layer flow is deliberately broken up and mixed. This results in an increase in the heat transfer performance of the charge air cooler  10 .  
         [0038]    [0038]FIG. 5 shows a further advantageous embodiment of the internal fin. In the webbed fin  22  shown previously, the vortex generators  48 ,  52  are designed as elongate beadings which are stamped from the surface of a web  42 . In the example of an embodiment according to FIG. 5, this vortex generator is designed as a ramp  60 , as can be seen in a perspective view of a fin member  61  in FIG. 5. The fin member  61  comprises webs  62  and  63 , which are connected to one another via a web crosspiece  64 . The ramps  60  are designed as flat surfaces extending obliquely to the air flow direction  65 , and form approximately a right angle. In other words, they form a type of shoulder with the web surfaces  62 . The ramps  60  in FIG. 5 ascend, when viewed in the air flow direction  65 . In contrast, ramps  66  are also provided which descend, when viewed in the air flow direction.  
         [0039]    A more detailed representation of the fin member  61  is given in FIGS. 5 a ,  5   b ,  5   c  and  5   d . FIG. 5 a  shows a lateral view of the front of the fin member  61 , in other words, transverse to the air flow direction  65 . It can be seen that, when viewed in the air flow direction  65 , the sequence comprises first an ascending ramp  60 , then a descending ramp  66  and then another ascending ramp  60 . These ramps  60 ,  66  and  60  can also be seen in FIG. 5 c , a view of the fin member  61  from above. In FIG. 5 d , the fin member  61  is shown in a lateral view from the rear. In this case, further ramps  67  and  68  are arranged in the right-hand region of the fin member  61 , in other words, in the downstream part of the fin. An ascending ramp  67  is followed by a descending ramp  68  and this in turn is followed by another ascending ramp  67 . It is particularly apparent from FIG. 5 c  that fin member  61  possesses a total of six ramps, three ramps  60 ,  66 ,  60  being arranged in the front region and a further three ramps  67 ,  68 ,  67  in the rear region on the opposite side of the fin.  
         [0040]    [0040]FIG. 5 b  shows the fin member  61  in a view from the front, in other words, viewed in the air flow direction  65 . The ramp  60 , which is an ascending surface relative to the air flow, has a width of b=1.3 mm. This corresponds approximately to one-third of the total width B of this fin member. At the upper end of the ramp  60 , is a passage  71  with an approximately rectangular cross section, through which the air flow can pass. Apertures similar to aperature  71  are arranged at the end of each of the ascending ramps  60  and  67  or at the beginning of the descending ramps  66  and  68 . In addition, passage apertures  72  are likewise provided downstream of the descending ramps  66  and  68 , and are shown in FIG. 5 and FIG. 5 a.    
         [0041]    The effect of these ramps  60 ,  66 ,  67 ,  68  is first, the air flow  65  is deflected upward and downward and second, a turbulent flow with a significant transverse component is generated. This transverse component is generated, in particular, by the shape and dimensions (width b) of the ramp and prevents the above mentioned continuous core flow.  
         [0042]    Further embodiments of the invention, which show a vortex generator in ramp form, are illustrated in FIGS.  6  to  10 . FIG. 6 shows a section of the above-mentioned fin member with a ramp  80  that forms an obtuse angle relative to the web surfaces  81  and  82 . In the example of embodiment according to FIG. 5, this angle was a right angle. FIG. 7 shows a modification of FIG. 6. In this embodiment, a similar ramp  83  is provided whose surface is pierced by a passage aperture  84  for the air flow.  
         [0043]    [0043]FIG. 8 shows a modification, in which the ramp-shaped vortex generator is designed as an exposed tab  85 . Tab  85  is partially punched out from the web surface  86  and is exposed at a right angle or obtuse angle to the web surface  86 . As a result of this tab  85 , first, a passage aperture  87  is formed in the web wall  86 , and second, cut-off edges  88  and  89 , and also  90 , are formed. These provide further turbulence of the air flow.  
         [0044]    [0044]FIG. 9 shows a box-shaped ramp  91 , which is punched out from the web surface  92  as a U-shaped section  93 . This U-shaped section thus comprises the surfaces  91 ,  94  and  95 , arranged approximately at right angles to one another.  
         [0045]    [0045]FIG. 10 shows a further alternative embodiment having a ramp  96  with a rounded hollow section  97 . The ramps  91  and  96  thus differ only slightly in respect to their hollow sections, but this does have an effect on the vortex formation.  
         [0046]    All the above-mentioned ramps according to FIGS.  6  to  10  have the common feature that they are all inclined approximately at an angle of 20°-30° relative to the air flow direction.  
         [0047]    The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The drawings and description were chosen in order to explain the principles of the invention and its practical application. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.  
         [0048]    German priority application no. 100 03 765.8 filed Jan. 28, 2000, including the specification, drawings, claims and abstract, is hereby incorporated by reference.