Patent Publication Number: US-6907920-B2

Title: Heat exchanger panel

Description:
STATEMENT OF GOVERNMENT INTEREST 
   Government has rights in this invention, pursuant to Contract No. NAS3-00177 awarded by NASA. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a novel heat exchanger panel which has particular utility in high temperature environments, such as in air breathing and rocket propulsion systems. 
   One method for fabricating a high temperature capability composite heat exchanger comprised processing or densifying a composite material with high temperature capability and metallic coolant containment tubes integrally assembled into the composite. This method required the use of expensive and high density (heavy) metal tubes which could not be removed for inspection or replacement. As a result, these old heat exchangers were heavy, costly, difficult to inspect, and virtually impossible to maintain. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a heat exchanger panel which is less complex, lighter, and less expensive to manufacture. 
   It is also an object of the present invention to provide a heat exchanger panel as above which is high temperature capable. 
   It is a further object of the present invention to provide a heat exchanger panel as above which is easy to inspect and repair. 
   It is yet a further object of the present invention to provide a heat exchanger panel as above which has utility in air breathing and rocket propulsion systems. 
   The foregoing objects are attained by the heat exchanger panels of the present invention. 
   In accordance with the present invention, a high temperature capable heat exchanger panel is provided. The heat exchanger panel broadly comprises a first panel, a second panel, and at least one fluid containment device positioned intermediate the first and second panels. At least one of the first panel and the second panel have at least one feature on an interior surface to accommodate the at least one fluid containment device which is separable from and independent of the first and second panels. 
   In a preferred embodiment of the present invention, each of the first and second panels is formed from a high conductivity, high temperature composite material such as a high conductivity, high temperature carbon/carbon composite material and/or a high conductivity, high temperature carbon/silicon carbide composite material. 
   Also, in a preferred embodiment of the present invention, the first and second panels are joined together by one or more composite fasteners. The fasteners may also be used to join a heat exchange panel in accordance with the present invention to a substructure. 
   Other details of the heat exchanger panel of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a heat exchanger panel in accordance with the present invention; 
       FIG. 2  is a sectional view of a portion of the heat exchanger panel of  FIG. 1  showing a fastener for joining the panel to a substructure; 
       FIG. 3  is an exploded view of a fastener used with the heat exchanger panel of the present invention; 
       FIG. 4  is an end view of an alternative heat exchanger panel in accordance with the present invention; 
       FIG. 5  is an end view of a heat exchanger panel embodiment with a machined metal assembly forming a coolant fluid containment device; 
       FIG. 6A  is an exploded view of a wall of a propulsion engine having heat exchanger panels in accordance with the present invention; 
       FIG. 6B  is a sectional view of a portion of the wall of  FIG. 6A ; 
       FIG. 7  is a sectional view of a portion of a combustion panel having a flush wall fuel injection system; 
       FIG. 8  is a perspective view of a portion of a combustion panel having an alternative fuel injection system; 
       FIG. 9  is a sectional view of another embodiment of a combustion panel having a fuel injection system; 
       FIG. 10  is a perspective view of a portion of a panel having spacers for accommodating a fluid containment system; and 
       FIG. 11  is a perspective view of a portion of the panel of  FIG. 9  having spacers for accommodating a fluid containment system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
   Referring now to the drawings,  FIGS. 1 and 2  illustrate a heat exchanger panel  10  in accordance with the present invention. The heat exchanger panel  10  includes a first panel  12 , a second panel  14 , and a fluid containment device  16  positioned intermediate the first and second panels  12  and  14 . The fluid containment device  16  may be formed from any suitable metallic and/or non-metallic materials known in the art, such as composite materials. In accordance with the present invention, the fluid containment device  16  is not fastened to either panel  12  or panel  14  in any manner. Rather, it is merely sandwiched between the panels  12  and  14 . 
   The panel  10  further includes one or more fasteners  18  for joining the first and second panels  12  and  14  together and/or for joining the heat exchanger panel  10  to a substructure  20 , such as a load carrying substructure. When the panels  12  and  14  are joined together in this manner, they hold the fluid containment device  16  in place. 
   In order to enable the heat exchanger panel  10  to be used in a high temperature environment, such as a wall panel for a scramjet engine or a rocket engine, each of the panels  12  and  14  is formed from a lightweight, high conductivity, high temperature capable composite material, preferably a non-metallic composite material. Suitable high conductivity, high temperature materials for the panels  12  and  14  include, but are not limited to, high conductivity, high temperature carbon/carbon and/or carbon/silicon carbide composite materials. Carbon/silicon carbide composite materials preferably are used only in situations where the temperature encountered by the panel(s) does not exceed 3000 degrees Fahrenheit. In accordance with the present invention, each of the panels  12  and  14  may be a simple monolithic sheet of material. Such sheets are advantageous in that they do not require expensive tooling and are not labor intensive to fabricate. Yet another advantage is that the aforementioned composite materials may be densified to be at least 75 to 80% dense using any number of common techniques known in the art and may be easily coated with an oxidation resistant material. Both densification and coating may be performed prior to installation of any fluid containment device  16 . 
   In order to accommodate and position the fluid containment device  16 , an interior surface  24  of each of the panels  12  and  14  is provided with a surface feature  25  which conforms to the exterior shape of the fluid containment device. For example, in the heat exchanger panel embodiment of  FIG. 1 , the fluid containment device  16  may comprise a plurality of parallel fluid passageways or tubes  26  connected to fluid inlet and outlet manifolds (not shown). In this embodiment, the surface feature  25  comprises a plurality of arched portions or grooves for receiving conforming the interior surface  24  to the exterior shape of the tubes  26 . 
   While it is preferred to have appropriate surface features on each of the interior surfaces  24  of the panels  12  and  14 , it should be noted that one could design a heat exchange panel so that the interior surface  24  of the panel  12  has a surface feature  25 , while the interior surface  24  of the panel  14  is planar or flat. 
   While the tubes  26  have been shown as having circular cross-sections, it should be realized that they could have other cross-sectional shapes. When such other cross-sectional shapes are used, the surface feature(s)  25  are shaped to conform to the shape of the tubes  26 . 
   In the embodiment of  FIG. 4 , the fluid containment device  16  may comprise two metallic sheets  28  which are formed to create fluid passages and which are brazed, bonded, or welded at the contact points. As before, the fluid passages may be joined to fluid inlet and outlet manifolds (not shown). In this embodiment, the surface features  25  on the panels  12  and  14  comprise a plurality of arched portions separated by planar portions  30  to accommodate the metallic sheets  28 . 
   In yet another embodiment of the present invention, the fluid containment device  16  may be a metallic heat exchanger  32  having thin planar face sheets to minimize weight. In this embodiment, the fluid passages in the metallic heat exchanger  32  may be joined to integrally formed fluid inlet and outlet manifolds (not shown). In this embodiment, the surface feature  25  is a planar interior surface feature on each of the panels  12  and  14  because there is no need to accommodate tubular cooling arrays. 
   The composite material panels  12  and  14  used in the heat exchanger panel  10  may be woven to minimize labor costs. The surface features  25  required to accommodate the fluid containment device  16  may be woven in to avoid machining and cutting fibers, if they can not be molded. If conductivity is an issue, a 2D lay-up could be used in order to cut down on the through thickness conduction. 
   Where high through the thickness conductivity is desired, a pitch fiber may be used in the composite materials forming the panels  12  and  14  and heat set after 3-D weaving to drive the conductivity as high as possible, while still allowing for weaving. 
   As previously mentioned, the panels  12  and  14  of the heat exchanger panel  10  are joined together by one or more fasteners  18 . Each of the fasteners  18  is preferably formed from a high temperature capable composite material. Suitable composite fasteners which may be used are shown in U.S. Pat. Nos. 6,042,315 and 6,045,310, both to Miller et al., which are hereby incorporated by reference herein. As shown in  FIG. 3 , each of the fasteners  18  has an enlarged head portion  40  and a rectangularly or square shaped shaft  42 . The shaft  40  is received by a rectangularly or square shaped orifice  44  in a metal sleeve  46 . The metal sleeve  46  has an exterior thread  48  and a bore  50  for receiving a locking pin  52 . The locking pin  52  is inserted through the bore  50  into a bore  51  in the shaft  42 , thereby securing the sleeve  46  and the fastener  18  together. 
   Referring now to  FIG. 2 , the panel  12  has a countersunk bore  54  for receiving the head portion  40  of the fastener  18 . The panels  12  and  14  and the substructure or back structure  20  having mating bores  56  for receiving the shaft  42  of the fastener  18 . To secure each fastener  18  in place and thus secure the panels  12  and  14  and the substructure  20  together, a nut  58  is threaded onto the sleeve  46 . The use of the composite fasteners  18  allows the panel  10  to be mechanically assembled and disassembled periodically for inspection and maintenance and to allow easy removal of the fluid containment device  16  or portions thereof. 
   The fluid containment devices  16  described herein may be used to transfer a coolant fluid through its passages. Alternatively, they may be used in some situations to heat or pre-warm a fluid, such as fuel, to be delivered to a portion of a propulsion system. 
   As can be seen from the foregoing description, the two piece heat exchanger panel of the present invention sandwiches the fluid containment device/manifold system and utilizes low cost composite materials and fabrication techniques. The material thickness of the panel  10  may be minimal, since it is for fluid/coolant containment only. The weight of the fluid containment device  16  is not a large contributor to the weight of the panel  10 . Thin conductive foils or paste could be used in areas where voids exist to enhance thermal conduction. This, in addition to thermal expansion and flowpath pressure, should result in good thermal conductivity from the composite to the fluid/coolant. One advantage to the panel of the present invention is that the panels  12  and  14 , when heated and/or pressurized, will conform to the coolant passage contour of the composite resulting in good thermal conduction. 
   The heat exchanger panel  10  of the present invention has utility in a wide range of air breathing propulsion systems such as jet turbine engines, ramjet engines and, in particular, a scramjet engine such as that shown in U.S. Pat. No. 5,333,445, which is incorporated by reference herein. A number of portions of such air breathing propulsion engines are subjected to extreme temperatures and require cooling. These portions include the cowl wall and the engine sidewalls of a scramjet engine amongst others. Also, the heat exchanger panel  10  may be used in rocket propulsion systems.  FIGS. 6A and 6B  illustrate one way in which a wall  80 , such as a cowl wall, can be provided with a heat exchanger panel  10  in accordance with the present invention. 
   As can be seen from these figures, a wall  80 , such as the cowl wall, may have a leading edge  82 , an inlet section  84 , a combustion panel section  86 , and a nozzle section  88 . The leading edge  82  may be formed from any suitable high temperature composite material known in the art, preferably a non-metallic composite material. Each of the sections  84 ,  86 , and  88  may be formed from a heat exchanger panel in accordance with the present invention. For example, each of the sections  84 ,  86 , and  88  may have a first or hot panel  90  formed from a high conductivity, high temperature capable composite material which forms the hot side of the wall, a second panel  92  formed from a composite material which forms a lower cold wall, and a coolant containment system  94  comprising a plurality of tubes or fluid passageways  96  which extend between a coolant inlet manifold (not shown) and a coolant outlet manifold (not shown). As can be seen from  FIG. 6A , the tubes or fluid passageways  96  run parallel to a longitudinal axis of the wall  80 . A first one of the manifolds may communicate with inlet tubes  98  for introducing a coolant into the tubes or fluid passageways  96 . A second one of the manifolds may communicate with outlet tubes  100  through which heated coolant can be removed from the tubes or fluid passageways  96 . The heated coolant may be passed through a heat exchanger (not shown) to be cooled and recycled. 
   The panels  90  and  92  may be formed as discussed above and may be provided with appropriate surface features for accommodating the tubes  96  of the coolant containment system  94 . Each of the panels  90  and  92  may be formed from a composite material selected from a group consisting of a carbon/carbon composite material and a carbon/silicon carbide composite material. The panels  90  and  92  may be joined to each other and to a substructure or back structure  102  using the composite fasteners  18  in the manner discussed above. The substructure  102  may be formed from any suitable metallic or non-metallic material known in the art. Typically, the substructure  102  will be formed by a hollow metallic structure. 
   The combustion panel section  86  may also be used to distribute cooled fuel into a space bounded by the wall  80  of the air breathing propulsion system. To this end, the combustion panel section  86  may be provided with one or more fuel supply tubes  104  which are each connected to a manifold  106  which extend transverse to the longitudinal axis of the wall  80 . As shown in  FIGS. 7 and 8 , each manifold  106  may be situated within the substructure  102  and may communicate with a plurality of injection nozzles  108  through which heated fuel is injected into the engine. As shown in  FIG. 7 , the injection nozzles  108  may terminate flush with the surface  110  or relatively close to the surface  110 , i.e. less than 0.010 inches below the surface  110 , of the hot panel  90  of the combustion panel section  86 . Alternatively, as shown in  FIG. 8 , the injection nozzles  108  may extend through the hot panel  90  of the combustion panel section  86  and have their outlets above the surface  110 . If desired, the substructure or back structure  102  may be slotted in the area of each injection nozzle  108  to allow for thermal differential growth between the cold panel  92  and the substructure or back structure  102 . Further, each hot panel  90  has a plurality of openings  107  with each injection nozzle  108  having its outlet aligned with one of the openings  107 . 
   In some instances, it may be desirable to not have a continuous cold panel  92 . In such situations, a discontinuous cold panel  92  may be utilized. As shown in  FIGS. 10 and 11 , in lieu of a continuous cold panel  92 , local supports or spacers  120  may be used to maintain separation between the fluid passageways or tubes  96  in the fluid containment system  94 . The spacers  120  are preferably joined to the substructure or back structure  102 . If desired, however, the spacers  120  may be joined to the underside of the hot panel  90 . Any suitable means known in the art may be used to join the spacers  120  to the substructure or back structure  102  or the panel  90 . If desired, the spacers  120  may be integrally formed with the substructure  102 . In this type of system, the hot panel  90  may be joined to the substructure  102  directly via the composite fasteners  18  in the manner previously mentioned herein. 
     FIG. 9  illustrates an alternative embodiment of a flush wall fuel injector system. In this embodiment, fuel enters manifold  106  via fuel line  104  and traverses to the injector nozzles  108  via conduits  122  located intermediate the hot panel  90  and the substructure  102 . If desired, the substructure  102  may be slotted to allow the injector nozzles  108  to move with the panel. 
   In the wall system of  FIG. 6 , the inlet, combustion panel, and nozzle sections  84 ,  86 , and  88  have been shown as being separate heat exchanger panels. If desired, these sections could be formed from a single heat exchanger panel  10  which extends from a point  128  near the leading edge  82  to a trailing edge point  130 . The single heat exchanger panel would have a single hot panel  90  and a single cold panel  92  which extends from the point  128  to the point  130 . In such an embodiment, the fluid/coolant containment system  94  may extend from an inlet manifold adjacent one of the points  128  and  130  to an outlet manifold adjacent the other of the points  128  and  130 . A fuel injection system such as those discussed above may be placed anywhere along the panel as required. 
   In yet another embodiment of the present invention, the wall  80  may be formed by a heat exchanger panel which has a cold panel  92  that extends from the point  128  to the point  130  and a hot panel  90  which is made up of a plurality of sections as shown in FIG.  6 . Such an arrangement has the advantage that if a particular area of the heat exchanger panel  10  has to be inspected, only one of the hot panels  90  needs be removed. 
   It is apparent that there has been provided in accordance with the present invention a heat exchanger panel which fully satisfies the objects, means, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.