Abstract:
The invention relates to a soldered heat exchanger network comprising folded flat multichamber tubes and wave-like ribs that are provided with fins. The multichamber tubes encompass at least two chambers, each of which is formed by folded webs that are soldered in the interior of the multichamber tube. According to the invention, the wave-like ribs are provided with fin-free fields in the area of the web or webs.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application is a Continuation of U.S. application Ser. No. 10/572,479, filed Aug. 28, 2006, which is the National Stage of International Application No. PCT/EP2004/010068, filed Sep. 9, 2004, which is based upon and claims the benefit of priority from prior Federal Republic of Germany Patent Application No. 103 43 905.6, filed Sep. 19, 2003, the entire contents of all of which are incorporated herein by reference in their entirety. 
         [0002]    The invention relates to a soldered heat exchanger network. 
     
    
     BACKGROUND 
       [0003]    Heat exchangers, for example coolant radiators or refrigerant condensers for motor vehicles, have a heat exchanger network comprising tubes and ribs, with coolant or refrigerant, for example, flowing through the tubes, and cooling air, in particular ambient air, flowing over the ribs. In soldered cooling systems, the tubes are embodied as flat tubes and the ribs are embodied as corrugated ribs which are soldered at their wave peaks to the flat longitudinal sides of the flat tubes. Flat tubes of large depth, that is as measured in the direction of the airflow, are often embodied as so-called multichamber tubes, that is to say, in order to divide individual chambers, they have webs which act as tie-rods and thus prevent the flat pipes from swelling or inflating as a result of the inner pressure. In folded multichamber tubes, it is therefore important that all the webs are uniformly soldered so that the required internal pressure stability of the flat pipe is maintained. 
         [0004]    Heat exchanger networks of this type are produced by cutting flat tubes and corrugated ribs to length and then “bundling” them in a suitable device, that is to say arranging the corrugated ribs adjacent to the flat pipes and joining them to form a block which is subsequently clamped and soldered (if appropriate to the associated tube ends or collecting tubes) in a soldering furnace. The clamping presses both the peaks of the corrugated ribs against the flat tubes and also the folded webs against the inner wall of the flat tubes. This contact pressure must be as uniform as possible in order to ensure as uniform and complete a solder as possible. Folded multichamber tubes, multichamber tubes for short, are known in various forms from the prior art, for example from EP-A 302 232 by the applicant. The known flat tube has, for example, a central web which is soldered to the opposite side of the flat tube and thus forms two chambers. A modified form of tube additionally has two beads (webs) which are folded from the tube material and are soldered to the opposite side of the tube and form four chambers in total. Folded multichamber flat tubes are known from EP-A 457 470 in which folded webs are alternately formed from opposite sides of the tube and are in each case soldered to the opposite inner wall of the tube. In addition, multichamber tubes are known which have opposing folded webs which only extend as far as the centre of the inner width of the tube and are soldered to one another there. The multichamber tubes can be embodied in one piece, that is to say can be provided with a longitudinal welded seam, or can be embodied in two pieces, that is to say with folded and soldered longitudinal seams arranged at the narrow sides. The applicant has disclosed a further form of folded multichamber flat tube in DE-A 102 12 300, in which a method of production is also described. 
         [0005]    As already mentioned, corrugated ribs, which have gills or sets of gills in order to improve the transfer of heat, are arranged between the flat tubes. Sets of gills such as this can, as shown for example in EP-B 547 309, be arranged in a continuous fashion in the direction of airflow or—as described in U.S. Pat. No. 4,693,307—be arranged in individual sets of gills, between which are situated smooth, that is to say non-gilled, corrugated rib regions. 
       SUMMARY OF THE PREFERRED EMBODIMENTS 
       [0006]    The applicant has established that when folded multichamber flat tubes having corrugated ribs to are soldered form a heat exchanger network, defects can occur which lead to the flat tubes “inflating”, this being attributable to insufficient soldering of individual webs to the opposing tube inner wall. 
         [0007]    It is therefore an object of the present invention to improve a soldered heat exchanger network of the type mentioned in the introduction using suitable measures such that faultless soldering is carried out both on the outside and the inside of the multichamber flat tubes. 
         [0008]    According to the invention, it is provided that the corrugated ribs are of smooth design in the region of the webs, that is to say are not provided with gills. “In the region of the webs” is intended to mean: as an extension of the webs in a transverse direction with respect to the flat sides of the multichamber tube. Gills or sets of gills are arranged in the regions between the webs, so that the chambers of the multichamber flat tube are each associated with sets of gills at approximately the same depth. The inventors have established that a “gilled” corrugated rib does not have a uniform rib height but rather a lower rib height, the minimum height, is present in the regions of the individual sets of gills than in the smooth, that is to say non-gilled regions, where there is a larger rib height, the maximum height. This irregularity in the rib height is attributable to the fact that the cutting and subsequent “twisting out” of the gills results in the corrugated rib being “pulled in” in the region of the gills, that is to say there is an element of fitting to size. The inventors have utilized this observation and matched the corrugated rib with its gilled arrangement to the multichamber flat tubes. This brings about the advantage that when the heat exchanger network is clamped after bundling, a uniform contact pressure is exerted on all the webs via the corrugated ribs. This subsequently leads to uniform, fixed soldering of all the webs so that they can fulfill their tie-rod function to the full extent and thus prevent the tubes from “inflating”. 
         [0009]    In an advantageous embodiment of the invention, the multichamber flat tubes have longitudinal seams which are either soldered or welded and are preferably arranged on one or both narrow sides of the multichamber flat tube. As a result, asymmetries on the flat sides of the tubes, which could adversely affect the soldering process, are avoided. 
         [0010]    In a further advantageous embodiment of the invention, the corrugated ribs also have smooth regions on the inflow and outflow sides. Above all, straight inflow and outflow edges and a laminar entry region for the airflow are obtained as a result. 
         [0011]    In a further advantageous embodiment of the invention, the smooth regions of the corrugated ribs each have an equal and maximum rib height. This ensures that the same contact pressure is exerted on all webs, and that the joint gap between the ridge of the web and the inner wall of the tube is minimized in a uniform manner. Uniform soldering, with sufficient strength for a tie-rod effect, is obtained as a result. 
         [0012]    In a further embodiment of the invention, the regions which are provided with gills have a minimum rib height. In this way, when the network is clamped, the clamping force does not act as an area load on the wave peaks but acts directly on the webs in approximately the manner of point-loads, and as a result, the flat tubes are pressed together in the region of the webs until they come into contact. 
         [0013]    In a further embodiment of the invention, the multichamber tube has two identical chambers which are separated by means of a central web, in the region of which the corrugated ribs are of smooth design. This is the most simple form of multichamber tube, which is used for relatively small system depths. 
         [0014]    In a further advantageous embodiment of the invention, the number of chambers or webs can be increased by any desired number, two webs with three chambers being a preferred solution for motor vehicle heat exchangers. 
         [0015]    An exemplary embodiment of the invention is described in more detail in the following and is illustrated in the drawing, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]      FIG. 1  shows a corrugated rib in a view from above, 
           [0017]      FIG. 1   a  shows the corrugated rib of  FIG. 1  in a side view and 
           [0018]      FIG. 2  shows a multichamber tube having lateral corrugated ribs. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  shows a corrugated rib  1  in a view from above,  FIG. 1   a  shows the corrugated rib  1  in a side view. The corrugated rib  1  serves as a secondary heat exchange area in air-cooled flat tube systems or heat exchanger networks. The corrugated rib  1  is subjected to a flow of air (ambient air) flowing in the direction of the arrow L, and has a depth T in the airflow direction L. The rib height corresponds to the amplitude of the wave pattern (cf.  FIG. 1   a ) and is denoted by H. The corrugated rib  1  is preferably produced from a thin aluminium sheet, into which are cut gills  2  on the air side in order to improve the exchange of heat, which gills  2  are arranged in the form of sets of gills  3 ,  4  on the rib surface. The ribs  2  are—as is not illustrated here but is disclosed by the prior art (EP-B 547 309 or U.S. Pat. No. 4,693,307) cited in the introduction—inclined relative to the rib surface and in this way form a so-called gill angle. This method of production of the gills  2 , that is to say the cutting and subsequent twisting of the rib material, results in a constriction, illustrated by the dashed lines  5 , in the region of the sets of gills  3 ,  4 . Said constrictions lead to a reduction in the rib height H. The reduced rib height is denoted by h and represents the minimum rib height. The maximum rib height is denoted by H and protrudes beyond the sets of gills  3 ,  4 , that is to say, in  FIG. 1 , at the inflow and outflow sides and in the centre of the corrugated rib  1 . As illustrated in  FIG. 1   a,  the corrugated rib  1  has wave peaks  1   a,    1   b,  by means of which the corrugated rib  1  bears against the tubes (not illustrated here). On account of the constrictions  5 , the wave peaks  1   a,    1   b  therefore do not form a continuous straight line. The gills  2  project into the airflow. 
         [0020]      FIG. 2  shows a folded multichamber tube  6  which has two flat longitudinal sides  6   a,    6   b  and two rounded narrow sides  6   d,    6   c.  Two webs  7 ,  8  are formed out of the upper longitudinal side  6   a  by means of folding, which webs  7 ,  8  are soldered to the opposite longitudinal side  6   b  and thus form tie-rods. The multichamber tube  6  is produced from sheet metal which is closed at the narrow side  6   d  by means of a longitudinal welded seam  9 . The multichamber tube  6  thus has three chambers  10 ,  11 ,  12  in which a coolant or refrigerant flows. Outside the multichamber tube  6 , corrugated ribs  13 ,  14  are arranged on its longitudinal sides  6   a,    6   b,  which corrugated ribs  13 ,  14  are soldered to the multichamber tube  6 . The corrugated ribs  13 ,  14  and the multichamber tube  6  thus constitute a section of a heat exchanger network (not illustrated) which is constructed in accordance with this pattern and can be used in coolant radiators or refrigerant condensers for motor vehicles. The corrugated ribs  13 ,  14  each have three sets of gills  15   a,    15   b,    15   c  and  16   a,    16   b,    16   c,  between which remain non-gilled, that is to say smooth, regions  17   a,    17   b  and  18   a,    18   b.  The arrangement of the sets of gills  15   a,    15   b,    15   c,    16   a,    16   b,    16   c  is selected such that they are situated in the region of the chambers  10 ,  11 ,  12 , and the smooth regions  17   a,    17   b,    18   a,    18   b  are arranged in the region of the webs  7 ,  8 . As explained above, said corrugated ribs also have a reduced rib height on account of the sets of gills  15   a  to  c  and  16   a  to  c,  and a maximum rib height H in the smooth regions  17   a,    17   b,    18   a,    18   b.  On account of the selected arrangement, the maximum rib heights H are situated, as seen in the direction of depth, at the level of the webs  7 ,  8  and at the inflow and outflow sides of the corrugated ribs  13 ,  14 . As explained in the introduction, the corrugated ribs  13 ,  14  and multichamber tubes  6  are bundled to form a heat exchanger network and are subsequently clamped using suitable clamping means in order to prepare for the soldering process. In the process, clamping forces occur between the corrugated ribs  13 ,  14  and the multichamber tubes  6 , which clamping forces are illustrated here by arrows F, each pointing in the direction of the webs  7 ,  8 . In said clamping process, the webs  7 ,  8  are thus pressed against the inner wall of the longitudinal side  6   b  of the tube, so that there is a minimum joint gap at the contact points. This ensures complete soldering and thus provides the multichamber tube  6  with the required internal pressure stability. 
         [0021]    The invention is explained on the basis of the above exemplary embodiment, that is to say for a multichamber tube having two webs and three chambers. Variations both in terms of shape and also in terms of the number of webs and thus the number of chambers likewise fall within the scope of the invention. An essential aspect of all embodiments is that the clamping forces exerted on the multichamber tube by the corrugated tubes are always directed towards the webs and bring about the required contact pressure there.