Abstract:
A process (or method) for manufacturing a heat exchanger includes inserting at least one plate for heat emission between two adjacent corrugations of a corrugated body. The corrugations are pressed against each other such that the inserted plate is clamped in between the corrugations in a positive-locking and non-positive manner. The heat exchanger for cooling fluids includes a tube, which is designed partially as a corrugated body and has at least one plate inserted for heat emission between two corrugations of the corrugated body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a United States National Phase application of International Application PCT/EP2011/002528 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2010 021 334.9 filed May 22, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a process (or method) for manufacturing a heat exchanger for cooling fluids with a tube, which is designed partially as a corrugated body, and to a heat exchanger for cooling fluids with a tube, which is designed partially as a corrugated body. 
       BACKGROUND OF THE INVENTION 
       [0003]    Such heat exchangers are used to bring about heat exchange between fluids, gases or liquids. A first fluid, which is to be cooled or heated, flows through a tube. This tube is led in another container, which surrounds the tube and which contains a second fluid, wherein said second fluid flows around the tube containing the first fluid, and there is a temperature difference between the two fluids. Such heat exchangers are used, for example, in systems for returning exhaust gas in motor vehicles, for heating the air admitted into the passenger compartment of a vehicle by waste heat of the engine or the use, in which the waste air, such as the exhaust gas of an internal combustion engine, is cooled by means of a heat exchanger. Such a system is described in EP 1 136 780 A2, wherein a first tube, which carries a first liquid, is surrounded by a second tube, which carries a second liquid having a different temperature into the intermediate space formed. The heat exchanger has two connection pieces formed movably through corrugated bodies and a straight middle part. Furthermore, ribs are formed on the first, inner tube in the middle part thereof in the axial direction around the outer circumference of said tube, and said tubes are distributed over the circumference. The ribs are made somewhat shorter than the length of the middle part. Due to the elongated contact surface of the ribs with the smooth tube, a strong stress structure develops over the length of the tube, to which the different temperature gradients along the tube make a considerable contribution due to the different temperatures of the fluids. 
         [0004]    Heat exchangers with transverse ribs, which are fastened around the tube in a ring-shaped pattern, mostly by welding, are known in this connection as well. These have a small heat exchange area, i.e., connection areas between tube and rib, as a result of which a large number of such ribs can be arranged on the tube. Restrained stresses, which may adversely affect welding in case of high stresses and lead to expensive repair, develop in the circumferential direction in the tube wall precisely here at high temperature gradients, as they can be seen, for example, in an exhaust gas tube. 
         [0005]    Also known are heat exchangers that have one or more corrugated bodies as an inner element carrying a first fluid instead of a smooth tube with ribs. The use of a corrugated body improves the functionality of a heat exchanger according to the state of the art because the velocity of flow of the gas within the tube is slowed down by the corrugations. The corrugations generate lateral spaces in relation to the main direction of gas flow, which generates turbulence, which leads to a slowdown of the entire velocity profile of the gas within the tube. There is a continuous heat exchange with the second fluid outside the corrugated body due to the longer residence time of the inner fluid. However, the prior-art constructions have a complicated design, which reaches a heavy weight. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide a heat exchanger of the type mentioned in the introduction, which has a simple design and can be manufactured in a cost-effective manner. Another object is to propose a process for manufacturing a tube for such a heat exchanger. 
         [0007]    These object is accomplished according to the present invention by a process of the type mentioned in the introduction, which is characterized in that at least one plate is inserted for heat emission between two corrugations of the corrugated body, and the corrugations are pressed against each other such that the inserted plate is clamped between the corrugations. Furthermore, the present invention provides for a heat exchanger of the type mentioned in the introduction, in which at least one plate is clamped for heat emission between two corrugations of the corrugated body in a positive-locking and non-positive manner. 
         [0008]    The heat exchanger according to the present invention comprises a tube, which is partially premanufactured as a corrugated body. Increased heat emission can be achieved by the heat exchanger according to the present invention by a plate consisting of metal being additionally clamped between two consecutive corrugations of the corrugated body. The heat transfer from the inner fluid to the outer fluid is improved by the use of the plate due to the enlargement of the surface of the heat exchange area. To further increase the area of the heat exchange surface, provisions are preferably made for this to be variable between corrugations and plate due to different corrugation heights. The consequence of a greater corrugation height is that the plate has better hold after pressing and a larger area between the corrugation and plate is favorable for a changed, improved heat emission. The heat emission can be controlled in a specific manner by the use of a plurality of plates, and provisions are made in an especially preferred manner for two plates being able to be inserted from radially opposite sides of the tube between two corrugations. Uniform heat emission is thus guaranteed over the entire circumference. Provisions are preferably made for this by the present invention for the at least one plate to have a rectangular shape and for the plate to have a semicircular recess fitting the diameter of the corrugated body in the valley of the corrugation at an edge facing the tube with said plate and/or said tube being manufactured from stainless steel. Plates whose thickness does not exceed the width of the corrugation valley located between the corrugations of the corrugated body are preferably used. The better the plate can be inserted between the corrugations and the better the edge presses close to the tube, the better is also the pressing. 
         [0009]    The manufacture of the heat exchanger is especially simple. A suitable plate, said plates having been provided in advance with a semicircular recess fitting the diameter of the tube in the corrugation valley, is inserted between two adjacent corrugations of the corrugated body. These corrugations are then pressed together with the plate located in between such that the inserted plate is clamped between the corrugations in a positive-locking and non-positive manner. For an especially firm, pressed connection, provisions are made by the present invention for the corrugations to be pressed radially uniformly onto the plate by axial upsetting by means of a tool. No weld seam is thus needed to fasten the plate to the tube. Provisions are, furthermore, advantageously made for the plates to be inserted prior to the bracing from radially opposite sides of the tube between two adjacent corrugations, as a result of which an improvement is achieved compared to welded variations with ring-shaped ribs because a multipart insert, which can be prepared in a simple manner, is used instead of a ring-shaped insert. Restrained stresses are avoided in the circumferential direction due to thermal expansion by means of the multipart inserts of the plates. The heat exchanger is thus exposed to less mechanical load, which is generated by temperature gradients, than in case of usual welded heat exchangers. A special advantage is the use of air as a heat exchange medium. No additional arrangement is thus needed for a second fluid, which would be used as a heat exchange gas or liquid. The construction as a whole is smaller and more compact. Other various combinations of materials between tube and plate are also conceivable, so that the heat emission can be further optimized. 
         [0010]    Further advantages and features of the present invention appear from the claims and from the following description, in which an exemplary embodiment of the present invention is explained in detail with reference to the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic overall view of the heat exchanger according to the present invention; 
           [0012]      FIG. 2  is a side view of the heat exchanger according to the present invention in a cross section; 
           [0013]      FIG. 3  is a front view of a plate for heat emission; 
           [0014]      FIG. 4.1  is a perspective view of a first step of the manufacturing process according to the present invention; 
           [0015]      FIG. 4.2  is a cross-sectional view of a second step of the manufacturing process according to the present invention; and 
           [0016]      FIG. 4.3  is a cross-sectional view of a third step of the manufacturing process according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to the drawings in particular,  FIG. 1  and  FIG. 2  show an overall view of a heat exchanger  1  according to the present invention in an overall view and a side view. Heat exchanger  1  comprises a tube  2  with a corrugated body  3 . Tube  2  and corrugated body  3  preferably consist of stainless steel here and are manufactured from one piece. Corrugated body  3  has corrugations  4 , with a corrugation valley  4 . 1  and with a corrugation peak  4 . 2 . A plate  5  is arranged pressed in between two corrugations  4 . For example, a single plate  5  is shown clamped in between corrugations  4  in the exemplary embodiment being shown here in  FIG. 1 . It is also possible to insert a plurality of plates, and the plates can be inserted not only from one side, but also from two sides, which are located opposite in relation to the tube, and they thus point in different directions. This can be used in a flexible manner depending on the space needed and the amount of heat emission needed. 
         [0018]      FIG. 3  shows such a plate  5 . Plate  5  has a rectangular basic shape, and a semicircular recess  5 . 2  is provided on its edge  5 . 1  which will later face the corrugated body  3 . Recess  5 . 2  has a diameter D 1 , which corresponds to a diameter D 2 , which is determined by the centers of the radii of the corrugation valley  4 . 1  of corrugated body  3  (cf.  FIG. 2  for this). Plate may also have other shapes, so that a semicircle or a triangle is also possible, besides a rectangular shape in various lengths and heights. To guarantee optimal fitting shape, the plate should have a maximum thickness that corresponds to the width of the corrugation valley  4 . 1  or to a distance between two corrugations  4  before bracing. Positive-locking and non-positive connection is thus guaranteed after bracing. Plate  5  is preferably made of stainless steel, and other materials, e.g., copper, are also possible to optimize the heat emission. 
         [0019]    The views in  FIGS. 4.1  through  4 . 3  show the process for manufacturing such a heat exchanger  1  step by step in a cross-sectional view. For example, it is shown how two plates  5  are brought to the corrugated body  3  from the top and from below the tube  2 . The plates  5  are inserted into a corrugation valley  4 . 1  at right angles to the direction in which tube  2  extends between two corrugations  4  (cf.  FIG. 4.2 ) and optionally held in this position. The semicircular recess  5 . 2  of plate  5  is now helpful for finding a central position at the bottom of corrugation valley  4 . 1 . When the plate  5  is inserted at right angles in relation to tube  2 , a tool (not shown) is attached on both sides of the corrugations  4  surrounding the plate  5 , one corrugation  6 . 1  to the left of plate  5  and one corrugation  6 . 2  to the right of plate  5 . This tool will then press the corrugations in question against each other uniformly in opposite axial directions, so that the corrugation  6 . 1  on the left of plate  5  as well as the corrugation  6 . 2  on the right of plate  5  are pressed against each other. The corrugations  4  are now pressed completely together, so that plate  5  is clamped in in a positive-locking and non-positive manner. The tool is then again detached from the corrugations  4  and moved to another plate  5  that can be inserted if a plurality of plates are to be fastened to the corrugated body  3 . Should two plates  5  be inserted between the same corrugations  4 , provisions are made for the plates  5  to be brought opposite each other to the tube  2 , to hold them and to press them together. 
         [0020]    A cost-effective heat exchanger, which can be manufactured in a simple manner and which can be further optimized by the use of additional plates and various material combinations, is obtained with the heat exchanger  1  according to the present invention. A further optimization of heat emission can be achieved by varying the heat exchange area, which is determined by the corrugation height and the area of the plate pressed in therein. Furthermore, restrained stresses in the circumferential direction, which commonly occur in case of welded heat exchangers, are avoided altogether by pressing the plate. This is achieved by the plates being inserted one by one rather than being attached to the tube in a ring-shaped pattern. The special advantages over welding is the increased mechanical mobility of the pressing. Compared to a welded solution, the materials have just enough clearance in relation to one another to compensate stresses, induced by the different thermal expansions of the materials, i.e., due to temperature. The cost-effective aspect is seen especially in that preformed corrugated bodies of any design and size can be used. The pushing in and pressing of suitable plates can be varied depending on the requirement imposed on the heat exchanger and can be integrated in the existing manufacturing process with a major effort. The non-pressed corrugations offer the added advantage of the heat exchanger that these offer the heat exchanger mobility and compensation, which is not offered by rigid tubes. 
         [0021]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
       LIST OF REFERENCE NUMBERS 
       [0000]    
       
           1  Heat exchanger 
           2  Tube 
           3  Corrugated body 
           4 . 1  Corrugation valley 
           4 . 2  Corrugation peak 
           5  Plate 
           5 . 1  Edge 
           5 . 2  Recess 
           6 . 1  Left corrugation 
           6 . 2  Right corrugation 
         D 1  Diameter of recess 
         D 2  Diameter of the centers of the radii in the corrugation valley