Patent Publication Number: US-7913750-B2

Title: Louvered air center with vortex generating extensions for compact heat exchanger

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/019,978 for a LOUVERED AIR CENTER WITH VORTEX GENERATING EXTENSIONS FOR COMPACT HEAT EXCHANGER, filed on Jan. 9, 2008, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A heat exchanger assembly, and more specifically, an assembly including louvered fins. 
     2. Description of the Prior Art 
     Louvered air performance is critical to compact heat exchangers (such as radiator, heater, condenser, and evaporator) total heat transfer rate for automotive and STAC applications. A typical heat exchanger with a louvered air design includes a plurality of tubes extending parallel to one another and a fin extending back and forth between each pair of adjacent tubes. Typically, each fin defines at least one louvered portion having a plurality of louvers extending parallel to one another. The fin has legs extending between the tubes and a end portion interconnecting two adjacent legs to define an tube space. 
     Due to the manufacturing limitation, a typical height of the louvered portion is about 75%-85% of the total air center height, or total fin height. This manufacturing limitation has led to “un-louvered regions” in both end of the air center. In these two regions, the airflow is un-disrupted by the louver, airflow velocity is high, and the thermal boundary layers are thick. 
     US Application 2007/0012430 discloses an upper manifold extending along an upper centerline and a lower manifold extending along a lower centerline. The manifolds are spaced form one another with the centerlines being parallel to each other. The upper manifold defines a plurality of upper tube slots being spaced along the upper centerline. The lower manifold define a plurality of lower tube slots being spaced along the lower centerline and aligned with the upper tube slots. 
     A plurality of tubes have flat sides and extend between ends thereof in the upper and lower tube slots and are parallel and spaced from one another. A plurality of fins each extend back and forth between and along the flat sides of the adjacent ones of tubes forming a continuous serpentine path. Each of the fins include a plurality of legs that extend between the tubes and a plurality of end portions that extend along the tube sides adjacent ones of the tubes to define the serpentine path. The adjacent legs are connected by one of the end portions along one tube and are open to the opposite adjacent tube to define a tube space between the adjacent legs along the flat sides of the tubes. 
     Although the current assemblies are sufficient for their intended purposes, there remains a need for a louvered air center heat exchanger that improves heat transfer. 
     SUMMARY OF THE INVENTION 
     The invention provides for a plurality of spaced projections extending inwardly from the end portions of the fins between the legs for interrupting air flow. The invention disrupts the airflow at both ends of the tube space to the same level as that of the air in the louvered region of the tube space thereby breaking airflow and thermal boundary layers and improving total heat transfer of the heat exchanger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description and the accompanying drawings that set forth an exemplary embodiment wherein: 
         FIG. 1  is a perspective view of a heat exchanger assembly; 
         FIG. 2  is a perspective view of a portion of the heat exchanger assembly of  FIG. 1 ; 
         FIG. 3  is a cross sectional view of the embodiment of  FIG. 2  illustrating projections on the tube; and, 
         FIG. 4  is a graph of the air velocity through the channel of  FIG. 3  versus the center height. 
         FIG. 5  is a perspective view of a portion of the heat exchanger of a second embodiment; 
         FIG. 6  is a perspective view of a portion of the heat exchanger of a third embodiment; 
         FIG. 7  is a cross sectional view of the embodiments of  FIGS. 5 and 6  illustrating projections on the tube. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a heat exchanger assembly  20  is generally shown in  FIGS. 1 and 2 . 
     An upper manifold  22  extends along an upper centerline  24  and a lower manifold  26  extends along a lower centerline  28 . The manifolds  22 ,  26  are spaced form one another with the centerlines  24 ,  28  being parallel to each other. The upper manifold  22  defines a plurality of upper tube slots  30  which are equal distantly spaced along the upper centerline  24 . The lower manifold  26  defines a plurality of lower tube slots  32  which are equal distantly spaced along the lower centerline  28  and aligned with the upper tube slots  30 . 
     A plurality of tubes  34  having flat sides  36  extend between the ends thereof in the upper and lower tube slots  30 ,  32  and are parallel and spaced from one another. The tube sides  36  are not limited to being flat. For manufacturing purposes, the tube sides  36  may be extruded. Each of the tubes  34  include a partition  38  that extends between the ends in the slots  30 ,  32  to define a pair of fluid passages  40  in each of the tubes  34  for conveying refrigerant. A plurality of fins  42 , generally indicated in  FIGS. 2 and 3 , extend back and forth between and along the flat sides  36  of adjacent ones of the tubes  34  in a continuous serpentine path  44 , generally indicated in  FIG. 3 . Each of the fins  42  include a plurality of legs  46  that extend between the adjacent ones of the tubes  34 . A plurality of end portions  48  extend along the tube sides  36  of the adjacent ones of the tubes  34  to define the serpentine path  44 . The adjacent legs  46  are connected by one of the end portions  48  along one tube  34  and are open to the opposite adjacent tube  34  to define a tube space  50  between the adjacent legs  46  along the flat sides  36  of the tubes  34 . 
     Each of the legs  46  include at least one set of louvers  52 ,  54  that extend diagonally outwardly from the legs  46 . The Louvers include a set of first louvers  52  that extend between adjacent tubes  34  on one side of the partition  38  and are angled away from the partition  38 . A set of second louvers  54  extend between the adjacent tubes  34  on the other side of the partition  38  and are angled in the opposite direction from the partition  38  for directing air in opposite directions from the partition  38  of each of the tube  34 . The legs may define more than two sets of louvers. Each of the tubes  34  include a plurality of spaced protrusions  56  extending outwardly from the flat sides  36  of the tubes  34  into the tube space  50  between the legs  46  for interrupting air flow through the tube space  50 . The protrusions  56  protrude from both sides of each of the tubes  34  for disposition in the tube space  50  between the legs  46 . 
     A plurality of spaced projections  58  extend inwardly from the end portions  48  of the fins  42  between the legs  46  for interrupting air flow. The projections  58  may have a conical shape, as shown in  FIGS. 1-4 . They may also extend diagonally across the end portions  48  and have a cylindrical shape, as shown in  FIG. 5 . Further, the projections may extend diagonally across the end portions  48  to align with each set of louvers  52 ,  54 , as shown in  FIG. 7 . 
     The velocity of the air through the tube space  50  varies along the center height of the tube space  50 .  FIG. 4  shows the air velocity versus the center height within one of the tube spaces  50 . The protrusions  56  and projections  58  disrupt the airflow and reduce the velocity in each of the tube spaces  50 . The increased uniformity of air velocities through each tube space  50  improve the heat transfer rate by as much as 10% with a corresponding 15% pressure penalty. 
     It is to be understood that “upper” and “lower” as used in the present application are arbitrary, inasmuch as a heat exchanger in accordance with the present invention can be oriented in different directions. Therefore, “upper” and “lower” should be understood to be used with reference to the orientation of the manifolds and tubes as shown in the drawings herein, and is not limiting the orientation of the manifolds or tubes in actual use. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.