Abstract:
The efficiency of dimple-type turbulators located on roughly parallel walls defining a flow channel within a heat exchanger is increased by providing protuberances on the dimples themselves which enhance turbulence, and thus, increase the rate of heat exchange.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to heat exchangers, and more particularly to improved turbulators for heat exchangers.  
       BACKGROUND OF THE INVENTION  
       [0002]     For many years, various types of turbulators have been employed in the flow channels for one or more heat exchange fluids in a heat exchanger. The turbulators induce turbulence in the flow of the heat exchange fluid through the channel and as is well known, the resulting increased turbulence increases the heat exchange coefficient, which, in turn, increases the rate of heat transfer.  
         [0003]     Turbulators come in many shapes and forms. In some cases, the turbulators are manufactured as elements separate from other constituents of the heat exchanger and are placed in a fluid flow channel at the time of assembly of the heat exchanger with which they are to be used. In other cases, turbulators are formed in the walls that define a flow channel. This type of turbulator is frequently found in so-called plate heat exchangers, drawn cup heat exchangers, and in heat exchangers utilizing so-called flattened tubes. In each of these types of heat exchangers, two or more generally parallel walls of high thermal conductivity, along with other constituents, define one or more channels. Dimple-like turbulator structures are formed in one or both of the walls. In some cases, where the dimples are formed in only one wall, they will extend entirely across the channel to contact and typically be bonded to the opposite wall to improve the strength of the heat exchanger.  
         [0004]     In some cases, dimples will be formed in both walls and extend across the flow channel to be bonded to the opposite wall, again to provide strength. In still other cases, the dimples will be aligned with each other and formed in both walls in which case the dimples extend only half-way across the flow channel and then are bonded to one another, again to provide strength to the heat exchanger.  
         [0005]     A typical plate heat exchanger having dimples which serve as turbulators formed in only one wall of the flow channel is illustrated in European patent Publication EP 0 263 798 B1. An example of dimples formed on both walls and extending partway across the flow channel to be bonded t one another is illustrated, for example, in European patent Publication EP 0 418 227 B1.  
         [0006]     As mentioned in the &#39;798 European patent publication, and as mentioned above, it is common to provide turbulator plates in various flow channels. The plates can be formed with a significant variety of structure that can be adapted to the particular heat exchange requirements. However, from a manufacturing standpoint, the provision of separate turbulators is not the preferred choice because separate parts are involved that must be produced and inserted into the flow channels, thus complicating production and assembly.  
         [0007]     Another restriction that hampers the use of separate turbulators is that in many applications, a great degree of cleanliness of the flow channels is required and residues used to bond the separate turbulators in place can have deleterious effects on the entire system.  
         [0008]     Thus, there is a real need for improved turbulator configurations where the turbulators are integrally formed with a wall or walls of a heat exchanger flow channel to avoid the problems associated with the use of separate turbulators and yet provide enhanced performance and adaptability to different heat exchange requirements that is more readily achievable with separate turbulators.  
       SUMMARY OF THE INVENTION  
       [0009]     The principal object of the invention is to provide a new and improved turbulator structure for use in the flow channels of heat exchangers. More particularly, it is an object of the invention to provide a new and improved turbulator that is integrally formed with the walls defining a flow channel in a heat exchanger.  
         [0010]     An exemplary embodiment of the invention achieves the foregoing objects in a heat exchanger having at least one flow channel for a heat exchange fluid defined by spaced, generally parallel walls between which the heat exchange fluid flows. A plurality of dimples are formed in at least one of the walls to extend therefrom toward the other wall to be secured thereto or to another dimple extending from the other wall toward the one wall. The dimples, as is conventional, act as turbulators to induce turbulence in the heat exchange fluid as it flows between the generally parallel walls. The invention specifically contemplates the provision of protrusions on the sides of the dimples that extend into the flow channel or channels to increase the inducement of turbulence in the heat exchange fluid as it flows between the parallel walls and around the dimples.  
         [0011]     In one embodiment, the walls are aluminum sheets and the dimples and the protrusions are formed by a metal-forming die.  
         [0012]     The invention contemplates that the dimples have bases integral with at least one of the walls and opposite flat tops bonded to the other of the walls or to the flat top of another of the dimples.  
         [0013]     In one embodiment of the invention, the protrusions on the dimples are located between the base and flat top of the corresponding dimple.  
         [0014]     In a preferred embodiment, the protrusions are ribs that extend from the base to the flat top of the dimples.  
         [0015]     In one embodiment, each dimple has a plurality of the ribs spaced from one another about the periphery of the dimple.  
         [0016]     A preferred embodiment contemplates that the ribs on each dimple are generally radially oriented. In a highly preferred embodiment, as mentioned previously, the dimples are die-formed in at least one of the walls and the protrusions are integral with the sheet of which the wall is formed and die-formed in the dimples.  
         [0017]     Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is comprised of  FIG. 1   a  and  FIG. 1   b  and illustrates fragmentary cross sections of the turbulence inducing protrusions of the invention.  FIG. 1   a  and  FIG. 1   b  are representative cross sections taken approximately along the line  1 - 1  in  FIG. 2 ;  
         [0019]      FIG. 2  is a fragmentary section taken approximately along the line  2 - 2  in  FIG. 3  or  4 ;  
         [0020]      FIG. 3  is a plan view of a turbulator dimple with enhanced turbulating inducing protrusions made according to the invention according to one embodiment thereof;  
         [0021]      FIG. 4  is a view similar to  FIG. 3  but of a modified embodiment of a turbulence-inducing structure made according to the invention;  
         [0022]      FIG. 5  illustrates flow channels employing turbulators according to the invention in one form of a heat exchanger;  
         [0023]      FIG. 6  is a fragmentary view showing still another example of turbulators made according to the invention; and  
         [0024]      FIG. 7  is a fragmentary, perspective view of a heat exchanger plate embodying turbulators made according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     In considering the invention, it must be kept in mind that same is not limited to any one specific type of heat exchanger. While it will most often be used in plate heat exchangers, drawn cup heat exchangers, or heat exchangers employing flattened tubes, those skilled in the art will readily appreciate that the same is susceptible to use in any sort of heat exchanger wherein flow channels are defined by two, generally parallel walls in which turbulating dimples can be formed. Hence, no restriction to any particular type of heat exchanger is intended except insofar as expressly stated in the appended claims.  
         [0026]     With the foregoing in mind, reference is made to  FIG. 7 , which shows a fragmentary perspective view of one type of heat exchanger, specifically, a housingless plate type heat exchanger with which the invention can be used. Specifically, one plate used in the formation of such a heat exchanger is illustrated and includes a base or wall section  10  surrounding by a somewhat trapezoidally shaped flange  12 . At the corners, ports  14 ,  16 , for two different heat exchange fluids are illustrated and the manner in which such ports  14 ,  16  are connected to like ports in other plates that are generally identical in the overall configuration that is shown in  FIG. 7  is well known and forms no part of the present invention.  
         [0027]     Projecting upwardly from the wall  10  is a pattern of a plurality of dimple-like turbulators  18  to be described in greater detail hereinafter. The pattern can take on any of a plurality of different forms depending upon the heat exchange requirements of the heat exchanger, the type of flow, i.e., cross current, counter current, or concurrent, etc., the overall resistance of the flow path within the heat exchanger, etc.  
         [0028]     As is well known, the plates shown in  FIG. 7  are frequently stacked as illustrated in  FIG. 5  to form adjacent flow channels and as a consequence, the wall  10  may be provided with downwardly directed dimples  20  at various locations and in a desired pattern to provided for turbulation in an adjacent flow channel.  
         [0029]     Referring to  FIG. 5 , it is seen that a second plate  22  also provided with a peripheral flange  24  substantially identical with the flange  12  is nested within the flange  12  and abutted to flat tops  26  of the turbulators  18 . Typically, the plates  10  and  22  are formed of aluminum, although other highly heat-conductive metals could be used as well. Braze alloy (not shown) is located at the interface of the flanges  12 ,  24  and the point of contact between the flat tops  26  of the dimples  18  and the plate  22  so that a brazing operation will bond all of the components together. A fluid-tight seal is thus provided between the flanges  12  and  24  making for a housingless heat exchanger while the dimples  18  are brazed to the adjacent plate  22  to provide strength. The net result is that connected flow channels  28  are formed about the dimples  18 .  
         [0030]      FIG. 6  illustrates a different configuration that may be employed. In this case, both the plate  22  and the plate  10  are provided with the dimples  18 , with dimples extending in opposite directions towards each other and with the plates  10  and  22  bonded together at points of abutment.  
         [0031]     As can be seen in both  FIGS. 5 and 6 , the dimples  18  are provided with protrusions  30  that are made according to the invention, and will now be described. Referring to  FIG. 3 , the flat top of each dimple  26  is illustrated and it will be seen that the flat top is connected by a generally frustoconical sidewall  32  to a base  34  which is, in reality, one or the other or both of the plates  10 ,  22 . That is to say, the base  32  is integral with the plates and the frustoconical sidewall and top  26  integral with the plates  10  and  22  as well. The protuberances  30  are formed in the sidewall  32  and extend from the base  34  to the flat top  26  at radially spaced locations. The protuberances, in the embodiment illustrated in  FIG. 3 , are in the form of ribs which extend generally radially from the center of the flat top  26 .  
         [0032]      FIG. 4  shows a somewhat similar configuration but rather than having a frustoconical sidewall, the same is an oblong sidewall  36  that decreases in dimension as one moves from the base  34  to the flat top  26 . Again, a plurality of ribs are on the protuberances  30 , and the same are generally radially extending from the top  26  to the base  34 .  
         [0033]      FIGS. 1   a ,  1   b , and  FIG. 2  show the protuberances  30  in cross section.  
         [0034]      FIGS. 1   a  and  1   b  show that the rib-like protuberances  30  may have relatively sharp apexes as desired. It will also be appreciated that with the dimples  18  being die-formed from the plates  10 ,  22 , that the protuberances  30  can be simultaneously formed using a concave die of the desired configuration operating against radially outer surface  40  of each dimple  18  as shown in  FIG. 1   a  and a convex die operating against the radially inner surface  42  of each dimple  18  as shown in  FIG. 1   b.    
         [0035]     It should be noted that the protuberances  30  need not be in the form of ribs as shown in  FIGS. 2, 3 , and  4 . They will, however, be formed of any kind of an interruption or almost micro fine structure located on the walls  32  or  36  at a location between the base  34  and the flat top  26  of each dimple.  
         [0036]     It is also observed that with two heat exchange fluids flowing in opposite sides of a plate, as, for example, the plate  10  as shown in  FIG. 7 , that the down turned dimples  20  may have different configurations and orientations from the upturned dimples  18  and different protrusions  30  as well to achieve desired heat exchange characteristics. Similarly, it is possible to use the dimples with the protuberances in only the flow channels handing one heat exchange fluid and not the other.  
         [0037]     The presence of the protrusions greatly enhances the turbulating effect provided the dimples like those shown at  18  or  20  but without the protrusions  30  to achieve efficiencies more comparable to those achieved with the use of separate turbulators without the attendant disadvantage of the use of separate parts requiring additional assembly and/or contamination problems as a result of extensive bonding operations.  
         [0038]     Typically, the protuberances  30  can be in the millimeter range, and with such a height, will enhance the bonding of the flat tops  26  to the plates  20 ,  22 .