Abstract:
A shielded heat exchanger and method of use in a vehicle is disclosed. The shielded heat exchanger may comprise a pair of spaced apart headers configured to contain a fluid flowing through the shielded heat exchanger, and a shielded tube. The shielded tube extends between the pair of headers and has a front edge. The shielded tube includes a flowing channel that operatively engages the headers for fluid flow through the flowing channel between the headers and a shielding channel extending parallel to the flowing channel between the headers along the front edge of the shielding tube, with the shielding channel configured to prevent flow of the fluid from the headers into the shielding channel.

Description:
BACKGROUND OF INVENTION 
       [0001]    The present invention relates generally to heat exchangers mounted near the front of a vehicle, and more particularly to protection for the heat exchangers from impacts, such as stones, hitting the front of the heat exchangers. 
         [0002]    Heat exchangers, such as condensers and radiators, are often mounted near the front of a vehicle in order to assure adequate air flow through them. This makes them vulnerable to impacts from objects, such as stones. The impacts can break one or more of the tubes in the heat exchanger, leading to leakage of the fluid flowing through the broken tube. As a result, some vehicles (particularly off-road vehicles) include protection screens that are mounted to block objects before they can impact the heat exchanger. But implementing protection screens for the heat exchangers can cost more than is desirable and may reduce the heat exchanger performance somewhat due to a negative effect on the air pressure drop for air flowing through the heat exchanger. Others have tried to address this concern by increasing the material thickness of a flow channel along the front of heat exchanger tubes. But channels with fluid flowing in them are still exposed, so an impact that pierces the outer wall of this thicker front channel still results in leakage of the fluid flowing through the heat exchanger. 
       SUMMARY OF INVENTION 
       [0003]    An embodiment contemplates a shielded heat exchanger for use in a vehicle. The shielded heat exchanger may comprise a pair of spaced apart headers configured to contain a fluid flowing through the shielded heat exchanger, and a shielded tube. The shielded tube extends between the pair of headers and has a front edge. The shielded tube also includes a flowing channel that operatively engages the headers for fluid flow through the flowing channel between the headers, and a shielding channel extending parallel to the flowing channel between the headers along the front edge of the shielding tube, with the shielding channel configured to prevent flow of the fluid from the headers into the shielding channel. 
         [0004]    An embodiment contemplates a method of protecting a tube of a heat exchanger mounted near a front of a vehicle from leakage due to impacts with objects, the method comprising the steps of: providing a flowing channel in the tube in fluid communication between a pair of headers, and a shielding channel extending adjacent to the flowing channel along a front of the tube; flowing a fluid through the flowing channel between the headers; and blocking any flow of fluid from the headers into the shielding channel. 
         [0005]    An advantage of an embodiment is that the shielded heat exchanger is much less likely to suffer tube leaks due to impacts from objects, such as stones. The shielding channels can absorb the energy of a stone impact, thus shielding the flowing channels from the impact. And, it does not matter if the material of a shielding channel is pierced since it does not carry any fluid through it. The improvement in resistance to leakage due to impacts is also generally more cost effective than employing protection screens. Moreover, shielding channels can be selectively used on the tubes of the heat exchanger that are more likely to receive impacts from objects and not used on tubes that are less likely to receive impacts, thus minimizing cost and weight. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a portion of a shielded heat exchanger according to a first embodiment. 
           [0007]      FIG. 2  is a view similar to  FIG. 1 , but taken from a different perspective. 
           [0008]      FIG. 3  is a view similar to  FIG. 1 , but showing a side view. 
           [0009]      FIG. 4  is a perspective view similar to  FIG. 1 , but illustrating a second embodiment. 
           [0010]      FIG. 5  is a perspective view of the second embodiment, similar to  FIG. 4 , but taken from a different perspective. 
           [0011]      FIG. 6  is a perspective view similar to  FIG. 1 , but illustrating a third embodiment. 
           [0012]      FIG. 7  is a side view similar to  FIG. 3 , but showing the shielded heat exchanger of the third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIGS. 1-3 , a portion of a shielded heat exchanger, indicated generally at  20 , is shown. The shielded heat exchanger  20  may be, for example, a condenser or radiator mounted near the front of a vehicle. The shielded heat exchanger  20  includes multiple tubes  22 , two of which are shown, that connect between a pair of headers  24 , only one of which is shown in this embodiment. Rows of fins  26 , only one row shown, are mounted between the tubes  22  and extend between the headers  24 . 
         [0014]    Each of the tubes  22  shown in  FIGS. 1-3  include multiple flowing channels  28  that are defined by reinforcements  30  and an outer wall  32  of the tubes  22 . The flowing channels  28  are sealed and direct fluid flow between the two headers  24 . The fluid may be, for example, refrigerant or engine coolant. 
         [0015]    Both tubes  22  shown in the first embodiment are shielded tubes—that is, the tubes  22  both also include a shielding channel  34  extending across the front  40  of the heat exchanger  20  between the headers  24 . The front  40  of the heat exchanger  20  is the side of the heat exchanger  20  that will face toward the front of the vehicle in which it will be used. The shielding channels  34  are, of course, located along the front of the tubes  22  because this is the most likely location for a significant impact from an object, such as a stone, while operating the vehicle. 
         [0016]    Each end of each shielding channel  34  includes a plug  38 . The plugs  38  seal the ends to prevent fluid in the headers  24  from entering the shielding channels and leaking out of the heat exchanger  20 . The plugs  38  may by made of wire with cladding on it so that the plugs  38  will be welded to the ends of the shielding channels  34  during a brazing process the heat exchanger  20  undergoes during assembly. Of course, other types of sealing means may be employed to seal the ends of the shielding channels  34  from the fluids in the headers  24  if so desired. In addition, each of the shielding channels  34  may include a cutout  36 . Also, one or two of the reinforcements  30  may be eliminated (as compared to a conventional heat exchanger tube) in order to compensate somewhat for material added for the shielding channels  34 . 
         [0017]    The tubes  22  can be manufactured using conventional extrusion or folding techniques used to form tubes in conventional heat exchangers. Thus, the complexity of manufacture is not increased significantly by adding the shielding channels  34  to the tubes  22 . Moreover, the shielding channels  34  can be formed integral with the flowing channels  28  of the tubes  22 . The term “integral” as used herein means that the particular elements are formed as a single monolithic piece—rather than being formed separately and later assembled and secured together. 
         [0018]    Also, if the shielding channels  34  are not additions to the original tubes for the conventional version of the heat exchanger, then one or two of the reinforcements  30  may be removed to increase the flow area in the flowing channels  28  to compensate for the loss of flow area in the shielding channels  34 . 
         [0019]    When operating the vehicle, the fluid will flow between the headers  24  through the flowing channels  28  of the tubes  22  while air flows through the fins  26 . The shielding channels  34 , since there is no fluid flowing in them, may act somewhat like the fins  26 , drawing heat from fluid flowing in the flowing channels  28  and transferring the heat to air flowing through the heat exchanger  20 . The cutouts  36 , allowing for air flow into and out of the shielding channels  34 , will not create a thermal shield, which may aid in the shielding channels  34  acting as fins. The distance of the shielding channels  34  in front of the fins  26  may help to reduce the fin deformation, resulting in a lower air pressure drop. 
         [0020]    During vehicle operation, should a stone or other object impact one of the tubes  22 , the impact will be with the shielding channel  34  since it extends across the front of the tube  22 . The shielding channel  34 , then, will absorb the energy of the impact. Since the fluid of the heat exchanger  20  does not flow through the shielding channel  34 , even if the impact pierces the shielding channel  34 , there will be no fluid leakage from the heat exchanger  20 . Consequently, this shielding channel  34  will act as a shield to protect the tube  22  right where and only where it is needed. In addition, the cutouts  36  can be employed to inspect the shielding channels  34  to assure that there is no leakage through the plugs  38  into the shielding channels  34 . 
         [0021]      FIGS. 4-5  illustrate a second embodiment of the shielded heat exchanger  120 . Since this embodiment is similar to the first, similar element numbers will be used for similar elements, but employing 100-series numbers. 
         [0022]    In this embodiment, the shielding channels  134  at the front  140  of each tube  122  extend almost all of the way across between the headers  124 , but stop just short, at open channel ends  142 . Thus, while the flowing channels  128  still extend to and direct fluid between the headers  124 , the shielding channels  134  do not contact or extend into the headers  124 . With this configuration, no brazing or other means of sealing needs to take place to assure that fluids do not leak from the headers  124  into the shielding channels  134 . 
         [0023]    In addition, the cross sectional shape of the shielding channels  134  can be whatever is desirable to provide the most advantageous combination of ability to absorb impact energy while minimizing manufacturing costs. This flexibility in cross sectional shape is applicable for other embodiments as well. 
         [0024]      FIGS. 6-7  illustrate a third embodiment of the shielded heat exchanger  220 . Since this embodiment is similar to the first, similar element numbers will be used for similar elements, but employing 200-series numbers. 
         [0025]    In this embodiment, one of the tubes is a shielded tube  222  while the other tube is a non-shielded tube  244 , with of course a row of fins  226  between them. Thus, there may be a zone  246  of shielded tubes  222  and a zone  248  of non-shielded tubes  244 . This illustrates that not all of the tubes need to be shielded tubes. It may be preferable for a particular vehicle application to have only a few of the lowest tubes on the heat exchanger be shielded to provide protection from projectiles while the upper tubes are non-shielded to save weight and cost. Of course, this is applicable to the other embodiments as well. 
         [0026]    For the shielded tube  222 , the flowing channels  228  are open to the headers  224  while the shielding channel  234  has welded ends  238  that block fluid flow into this channel  234 . For the non-shielded tube  244 , the channel along the front  240  of the tube  244  is a flowing channel  228  with a fluid connection to the headers  224  like the other flowing channels  228 . This channel along the front of the non-shielded tube  244  may be an additional channel, with the non-shielded tube having the same number of channels as a shielded tube, or there may be one less channel for the non-shielded tube if so desired. 
         [0027]    The shielding channel  234  in this embodiment is sealed, with no cutouts or open channel ends like the first two embodiments. Thus, air is trapped in the shielding channel  234 . As the trapped air heats up during operation of the vehicle, this hot air may build pressure that will help absorb the energy of impact from objects, such as stones. 
         [0028]    While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.