Abstract:
An inlet manifold for use with a heat exchange device such as a cold plate in which the manifold includes a main passage for transferring liquid. The main passage includes a seat sized to hold an orifice plate for restricting the transfer of liquid to a flow suitable to produce a pressure drop. An orifice plate retaining element contacts the orifice plate to maintain the orifice plate on the seat, and has a locking element to prevent unlocking during use.

Description:
STATEMENT OF GOVERNMENT INTEREST 
       [0001]    This invention was made with government support under NNJ06TA25C awarded by NASA. The government has certain rights in the invention. 
     
    
     BACKGROUND 
       [0002]    Heat exchangers are conventionally used to heat devices that require heat or cool devices that produce heat that needs to be removed. One example of a heat exchanger is known as a cold plate, which is used, for example, to cool electronic units that produce heat while being operated. The heat needs to be removed to permit the electronic components to continue functioning. 
         [0003]    One concern about the use of cold plates is that when orifices are used to control the pressure drop or flow rate, the orifices have been retained in bolted housings that require seals. This introduces potential leak points into the system. Often it is necessary to adjust or control the pressure drop or flow rate specifically for a particular end use, so the cold plate cannot be used without a method of making that adjustment or control. If the cold plate is intended for use in extreme environments, such as in outer space, the seals are particularly vulnerable and the potential for leakage prohibits their use. 
         [0004]    An alternative way to control the pressure drop or flow rate in cold plates is needed to permit use of cold plates in extreme environments. 
       SUMMARY 
       [0005]    The present invention is a device for adjusting fluid flow in cold plates and other fluid flow heat exchangers to obtain a desired pressure drop without the use of seals. The device includes an orifice that provides the desired fluid flow, thus controlling coolant pressure drop inside a cold plate. Different orifices are employed until the one is found that has the appropriate internal diameter to provide the desired pressure drop. During testing, the orifice is secured with a non-locking orifice nut. Once correct orifice size is determined, the orifice is secured using a nut with a locking element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a cold plate used to actively cool electronic boxes. 
           [0007]      FIG. 2  is a perspective view of the other side of the cold plate of  FIG. 1 . 
           [0008]      FIG. 3  is an exploded view of a section of one of the cooling tubes of the cold plate showing the device used to control the pressure drop inside the cold plate of  FIG. 1 . 
           [0009]      FIG. 3A  is a perspective view of one component in  FIG. 3 . 
           [0010]      FIG. 4  is an enlarged view of an orifice retaining nut. 
           [0011]      FIG. 5  is a perspective view showing two cold plates bolted to a vehicle structure. 
           [0012]      FIG. 6  is a perspective view showing the addition of boxes to be cooled by the cold plates shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIGS. 1 and 2  show cold plate  11  with surface  13  for cooling electronic units that require cooling to function. Cooling liquid inlet manifold  14  has inlets  15 A,  15 B and outlets  16 A,  16 B. Cooling liquid outlet manifold  17  has inlets  18 A,  18 B, outlets  19 A,  19 B. Coolant flows through inlets  15 A,  15 B to outlets  16 A,  16 B into cold plate tube coolant loops  20 A,  20 B, respectively. Coolant flows out through loops  20 A,  20 B to inlets  18 A,  18 B of outlet manifold  17 , and then out through outlets  19 A,  19 B. Loops  20 A and  20 B are held in place with loop mounts  23 , as seen in  FIG. 2 . Manifolds  14  and  17  each are shown as having two inlets and two outlets, but one or many inlets, loops and outlets can be used, depending on design considerations. In every inlet manifold, the pressure drop (and thus flow rate of coolant) is controlled by the present invention. Inside cold plate tube manifold inlets  15 A and  15 B are orifices that provide for the required pressure drop for a desired fluid flow rate. 
         [0014]      FIG. 3  illustrates one cooling liquid inlet manifold assembly  14  which includes inlet  15 A, tube  27 , orifice retention bore  29 , orifice plate mounting seat  31 , outlet passage  33 , outlet  16 A, orifice plate  37 , and orifice retaining nut  39 . Cooling fluid flows in inlet  15 A through inlet passage  27 , through retaining nut  39  and orifice plate  37 , to outlet passage  33  and outlet  16 A. 
         [0015]    Orifice plate  37 , shown alone in  FIG. 3A , is positioned within orifice retention bore  29  against mounting seat  31 . Orifice retaining nut  39  holds orifice plate  37  in place against mounting seat  31 . Center bore  40  of retaining nut  39  is aligned with orifice  37 A of orifice plate  37 . 
         [0016]    Orifice retention bore  29  has threads  29 A on its inner wall to engage external threads  39 A on orifice retaining nut  39 . A smaller diameter portion  41  extends from retaining nut  39  into a reduced diameter portion of retention bore  29  and holds in place orifice plate  37 . Orifice plate  37  and retaining nut  39  may be made from any solid material. Stainless steel has been shown to be effective for both elements. 
         [0017]    Orifice retaining nut  39  also includes locking strip  43 . One locking strip that has been effective is a KEL-F® PCTFE strip as defined in AMS 3650, which is standard for locking screws and bolts. KEL F® is a 3M registered trademark for a polychlorotrifluoroethylene polymer and has an operating temperature range of −320° F. (−196° C.) to +390° F. (199° C.). A slot is cut in threaded portion  39 A of locking nut  39 , typically about 0.020 inches (0.08 mm) and filled with a strip of the polymer. Flared inlet  40 A of center bore  40  guides fluid from inlet passage  27 . 
         [0018]    During assembly of cold plate  11 , orifice plates  37  having different sized orifices  37 A are put in inlet manifolds  15 A and  15 B, as shown with manifold  15 A in  FIG. 3 . Orifice plate  37  is held in place with a non-locking orifice nut, which is identical to orifice retaining nut  39  except that it is without locking strip  43 . The coolant pressure drop is measured with different orifices  37 A until the one is found that provides the desired or required pressure drop. The non-locking orifice nut is removed and orifice retaining nut  39  is inserted, with locking strip  43 , such as by use of a screwdriver in slot  39 B. Locking strip  43  is activated simply by screwing locking nut  39  into threads  29 A of orifice retaining bore  29 . Locking strip  43  prevents movement of locking nut  39  under normal vibration and other forces. Cold plate  11  is now ready for installation in a vehicle such as a space station or other orbiting vehicles. 
         [0019]      FIG. 5  shows two cold plates  11 A and  11 B mounted on a portion of vehicle structure  49  after the orifices are installed and locked in place as described above. Inlets  15 A,  15 B and outlets  19 A,  19 B of each cold plate  11 A,  11 B are then welded to the vehicle plumbing (not shown but conventional).  FIG. 6  shows that box  51  and box  53  are secured directly into vehicle structure  49  but boxes  51  and  53  containing electronic elements to be cooled are not fastened to cold plates  11 A and  11 B. Non-structural cold plates, not shown, mount boxes  51  and  53  to vehicle structure  45 . 
         [0020]    The cold plate system of this invention permits controlled cooling of individual electronic units base upon the needs of the unit through selection of the appropriate orifice diameter determined through pre-installation testing. After final installation, the electronics are now protected from heat generated during operation of the electronic components. 
         [0021]    While the invention has been described with reference to an exemplary embodiment(s), 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(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.