Abstract:
A heat exchanger useful for mounting to an electronic component housing or other system requiring heat exchange. The heat exchanger has a manifold having a cross-sectional configured for providing an unequal coolant flow to an array of cooling channels fed by the manifold, thereby providing for preferential amounts of heat exchange over a given heat exchange surface of the heat exchanger. A safety channel may surround the channels carrying the coolant to prevent potential leakage outside of the heat exchanger.

Description:
TECHNICAL FIELD 
     The technical field generally relates to heat exchangers, such as those used to cool power electronics or other apparatus or systems requiring heat exchange. 
     BACKGROUND 
     Electronic components used in power generation systems often create heat and as such are generally cooled. Although a variety of cooling options are available, in airborne applications the choices are typically limited by weight, cost, reliability, and so on. Furthermore, since devices requiring cooling may experience differential heating across their bodies, cooling systems must often be over-sized, or include complicated valving etc., to ensure all areas are adequately cooled. However, in airborne systems, there are associated cost, weight and/or reliability penalties with these prior art solutions which the designer has heretofore had no choice but to accept. Hence, there remains a need for improved heat exchange solutions. 
     SUMMARY 
     There is provided a heat exchanger comprising: a body having a plurality of cooling channels defined therein, and a fluid supply manifold located at a first end of the cooling channels, the fluid supply manifold being in parallel fluid flow communication with the cooling channels for feeding coolant thereto, the fluid supply manifold having a cross-sectional area which varies over its length and thereby configured for providing greater coolant flow to cooling channels fed by portions of the fluid supply manifold having a greater cross-sectional area than remaining portions of the fluid supply manifold. 
     There is also provided a heat exchanger comprising a first plate having a first surface, and a second plate, the second plate abutting the first surface of the first plate in sealing engagement, the first plate and the second plate including therebetween: a plurality of cooling channels, a supply channel being in fluid-flow communication with the cooling channels for supplying coolant thereto, a discharge channel being in fluid-flow communication with the cooling channels for discharging fluid therefrom, and a safety channel circumscribing the cooling channels, the supply channel and the discharge channel for collecting any coolant leakage therefrom, the first plate having a second surface opposite the first surface, the first surface cooling the second surface when coolant flows through the cooling channels. 
     There is further provided a heat exchanger comprising: a first plate having two protrusions on opposite sides thereof, the first plate having an undersurface having a plurality of cooling channels defined therein in a side-by-side parallel configuration, a fluid supply channel located at a first end of the cooling channels and disposed transversally with respect to the cooling channels, the fluid supply channel being in fluid flow communication with the cooling channels for feeding coolant thereto, a fluid removal channel located at a second end, opposite the first end, of the cooling channels and disposed transversally with respect to the cooling channels, the fluid removal channel being in fluid flow communication with the cooling channels for removing fluid therefrom, a fluid connection inlet for connection with a coolant supply source for providing coolant to the heat exchanger and which is in fluid flow communication with the fluid supply channel, the fluid connection inlet being provided at a first one of the two protrusions, a fluid connection outlet for connection with a coolant exhaust so as to discharge coolant from the heat exchanger and which is in fluid flow communication with the coolant removal fluid channel, the fluid connection outlet being provided at a second one of the two protrusions, a second plate coupled with the undersurface of the middle plate so as to seal the cooling channels, the fluid supply channel, the fluid removal channel, the fluid connection inlet and fluid connection outlet; wherein the first plate includes a top surface in heat exchange relationship with components to be cooled, the coolant flowing through the cooling channels on the undersurface of the first plate removing heat from the top surface of the first plate. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying figures, in which: 
         FIG. 1  is an exploded view of an embodiment of a heat exchanger including an upper plate, a middle plate and a bottom plate; 
         FIG. 2  is a bottom plan view of a plate of the heat exchanger of  FIG. 1 ; and 
         FIG. 3  is an enlarged view of section A of the plate shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     A heat exchanger for a heated surface is generally shown at  10 , as seen in detail on  FIG. 1 , which shows an exploded view of the heat exchanger  10 . The heat exchanger  10  can be used to remove heat losses from power electronic equipment or electronic components. The heat losses may be transferred to a coolant passing through the heat exchanger  10 . 
     In one embodiment, the heat exchanger  10  comprises a body or housing  12  on top of which electronic components (not shown) may be located. The housing  12  of the heat exchanger  10  comprises three main components, a middle plate  14 , a bottom plate  16  positioned under the middle plate  14 , and a top plate  18  positioned over the middle plate  14 . The three plates  14 ,  16 ,  18  can be made of aluminum, but may alternatively be made from other types of heat conducting material, for example copper etc. 
     As seen in  FIG. 2 , the middle plate  14  has an undersurface  19  including a series of cooling channels  20  defined therein and located in a side-by-side arrangement, a fluid supply channel  24  in fluid flow communication with a first end of the cooling channels  20  for supplying coolant thereto and a fluid discharge channel  22  in fluid flow communication with a second opposed end of the cooling channels  20  for discharging coolant therefrom. The supply and discharge channels  24  and  22  are facing each other from opposed sides of the cooling channels  20  and are transversely disposed with respect thereto. The middle plate  14  has a generally rectangular contour except for two protrusions  26 , the protrusions  26  being located on opposite longitudinal sides of the middle plate  14  and being located in the same horizontal plane as the housing  12 . The two protrusions  26  are slightly laterally offset to provide correct assembly. As will be seen hereinafter, one of the protrusions  26  provides for a fluid inlet connection  28 , while the other protrusion  26  provides for a fluid outlet connection  30  when the bottom plate  16  is assembled to the middle plate  14 . The fluid inlet connection  28  is in fluid flow communication with the fluid supply channel  24  for supplying fluid thereto, whereas the fluid outlet connection  30  is in fluid flow communication with the fluid discharge manifold  22  for discharging fluid therefrom. In addition, the middle plate  14  includes a safety channel  32  defined in the undersurface  19  and circumscribing the cooling channels  20 , the fluid supply and fluid discharge channels  24 ,  22  and the fluid inlet and fluid outlet connections  28 ,  30 . 
     The cooling channels  20  are provided for having coolant flow therethrough. The cooling channels  20  may have a zigzag type configuration with rectangular cross sections, which in the embodiment shown, are all identical. In another embodiment, the cooling channels  20  may have different configurations with respect to one another. The cooling channels geometry depicted in the Figures is defined for laminar flow at relatively low Reynolds number of the coolant flow, as described in co-pending application publication number 2009/0255652 from Pratt &amp; Whitney Canada, the entire content of which application is incorporated herein by reference. 
     The fluid inlet and outlet connections  28 ,  30  include connection openings  29  which extend through respective protrusions  26  of the middle plate  14  and which may accommodate a fluid inlet component (not shown) and a fluid outlet component (not shown), respectively, such as to provide a coolant inlet and a coolant outlet, respectively, into and out of the heat exchanger  10 . The fluid inlet component and the fluid outlet component may be for example, fluid pumps. The fluid inlet and outlet connections  28 , also include fluid channels  31   b ,  31   a , respectively, which interconnect the connection openings  29  and the fluid channels  22 ,  24 . 
     The fluid supply channel  24  and the fluid discharge channel  22  are positioned transversely with respect to the cooling channels  20 . The fluid supply channel  24  has an inner wall  25   a  located adjacent the cooling channels  20  and including openings  42  therein for supplying coolant to the cooling channels  20  and an outer wall  25   b  located opposite the inner wall  25   a  and including an opening  43  for receiving fluid from the fluid channel  31   b  of the fluid inlet connection  28 , the width W of the supply channel  24  being defined as the distance between inner wall  25   a  and outer wall  25   b . The fluid discharge channel  22  has an inner wall  23   a  located adjacent the cooling channels  20  and including openings  40  therein for discharging coolant from the cooling channels  20  and an outer wall  23   b  located opposite the inner wall  23   a  and including an opening  41  for directing fluid into the fluid channel  31   a  of the fluid outlet connection  30 , the width W of the discharge channel  22  being defined as the distance between inner wall  23   a  and outer wall  23   b . As seen in  FIG. 2 , the inner walls  23   a  and  25   a  are generally straight, whereas the outer walls  23   b  and  25   b  may be oblique, skewed and/or curved, such that the channels  22 ,  24  have widths W which vary over their respective lengths L. In the embodiment shown, the fluid supply channel  24  and the fluid discharge channel  22  have a constant depth, and the widths W determine the size of the cross-sectional area at various locations of the channels  22 ,  24 . 
     In the embodiment shown in  FIG. 2 , the fluid supply channel  24  and the fluid discharge channel  22  are unequal and may be skewed, such that their cross-sectional areas are not constant and vary throughout their respective lengths L. As shown in  FIG. 2 , the channels  22  and  24  may have the same profile variation or cross-sectional change along the length thereof (i.e. they can be a mirror image of each other). The channels  22  and  24  have greater cross-sectional areas at locations where they have a wider width W and smaller cross-sectional areas at locations where they have a smaller width W. The fluid supply channel  24  and the fluid discharge channel  22  both contribute to unequal coolant flow across individual cooling channels  20 , as more coolant is provided in and removed from, respectively, the cooling channels  20  positioned adjacent where the channels  22 ,  24  have a larger cross-sectional area. As such, it is possible to provide more coolant flow in certain cooling channels  20 , even though each cooling channel  20  has an identical configuration. For instance, in the example illustrated in  FIG. 2 , more coolant flow can be provided to the cooling channels  20  disposed on the right hand side of the page than to the cooling channels  20  located on the left hand side of the page. This provides for greater cooling for the devices mounted on the ring hand side of the heat exchanger. Accordingly, devices required added cooling can be mounted on that side of the heat exchanger, thereby obviating the need for complex valve system for regulating the flow through the cooling channels in order to provide differential cooling across the surface of the heat exchanger body. 
     The safety channel  32  is a closed-loop channel surrounding the cooling channels  20 , the fluid supply and fluid discharge manifolds  24 ,  22  and the fluid inlet and fluid outlet connections  28 ,  30 . The safety channel  32 , in the case of a fluid leak, receives any fluid leakage from the cooling channels  20 , the fluid supply and fluid discharge manifolds  22 ,  24  and the fluid inlet and fluid outlet connections  28 ,  30 , and contains the fluid leakage, such that the fluid is prevented from leaking outside of the heat exchanger  10 . The safety channel  32  has at least one evacuation hole  34  ( FIG. 3 ) formed therein, for evacuating in a controlled way, any fluid leakage received inside the safety channel  32 . In the embodiment shown, the evacuation hole  34  is at an outer periphery extremity of the protrusion  26  in which is provided the outlet connection  30 . The evacuation hole  34  may be connected to a device to collect, evacuate and signal the presence of fluid inside the safety channel  32 , thereby indicating a fluid leak in the heat exchanger  10 . The safety channel  32  is connected to an environment pressure at the evacuation hole  34 , the fluid leakages in the safety channel naturally flowing towards the environment pressure. 
     As shown in  FIG. 1 , the middle plate  14  has a top surface  21 , opposite the undersurface  19 , which may be heated and as such, heat may be transferred from the top surface  21  into coolant passing through the cooling channels  20  of the undersurface  19 , thereby cooling the top surface  21 . The top surface  21  includes the connection openings  29  of the fluid inlet and outlet connections  28 ,  30 . 
     As seen in  FIG. 1 , the bottom plate  16  has a generally similar rectangular contour as that of the middle plate  14 , including protrusions  36  which have the same shape as the protrusions  26  of the middle plate  14 . The bottom plate  16  is coupled to the middle plate  14 , thereby superimposing the undersurface  19  of the middle plate  14  and closing off and sealing a bottom portion of the cooling channels  20 , the fluid supply channels  24 , the fluid discharge channels  22 , fluid channels  31   b ,  31   a  of the fluid inlet and outlet connections  28 ,  30  and the safety channel  32  defined in the middle plate  14 . The bottom plate  16  may be coupled to the middle plate  14  using for example, diffusion bonding. As mentioned, the connection openings  29  of the fluid inlet and outlet connections  28 ,  30  pass through the middle plate  14 , and as such, these openings  29  remain unsealed on the top surface  21  of the middle plate  14 . Therefore, a fluid inlet component (not shown) and a fluid outlet component (not shown) may be accommodated by the connection openings  29  on the top surface  21 . 
     In an alternative embodiment, the bottom plate  16  may be coupled to the middle plate  14 , and the cooling channels  20 , the fluid supply channel  24 , the fluid discharge channel  22 , the inlet and outlet fluid channel  31   b ,  31   a  and the safety channel  32  may be formed between the plates  14 ,  16 , i.e. partly in the middle plate  14  and partly in the bottom plate  16 , such that a portion of these elements lies in the middle plate  14  and an opposite portion of these elements lies in the bottom plate  16 . The various channels could also be only defined in the top surface of the bottom plate with the middle plate acting as a cover for sealing the top surface of the bottom plate. 
     It is also understood that the cooling channels  20 , the fluid supply channel  24 , the fluid discharge channel  22 , the fluid inlet and outlet channels  31   b ,  31   a  and the safety channel  32  may be formed in different plates. For example, the safety channel  32  and the cooling channels  20  may be formed in the middle plate  14 , whereas the fluid supply channel  24 , the fluid discharge channel  22 , the fluid inlet channel  31   b , and the fluid outlet channel  31   a  may be formed in the middle plate  16 . Other such combinations are possible in various other embodiments. 
     As seen in  FIG. 1 , the top plate  18  has a similar rectangular structural contour as that of the middle and bottom plates  14 ,  16 , but without the protrusions  26 ,  36 . The top plate  18  may carry heat-emitting components (not shown) thereon, for example electronic components. These components may be attached to the top plate  18  using various fasteners, types of bonding or adhesives. In the embodiment shown, the top plate  18  has a plurality of holes  38 , with fasteners (not shown) being inserted into the holes  38  in order to attach electronic components thereto. In the embodiment shown, the holes  38  include threaded inserts (not shown) therein and the electronic components are attached thereto with bolts (not shown). 
     The top plate  18  may be connected to the middle plate  14  using various bonding materials, such as for example, relatively low temperature soldering or a high temperature epoxy-silver adhesive. The soldering or the adhesive serve to facilitate low thermal resistance between the top plate  18 , having the electronic components thereon which are sources of heat, and the remainder of the housing  12 , namely the middle and bottom plates  14 ,  16 , which is cooled using the coolant. As such, heat transfer from the top plate  18  to the middle and bottom plates  14 ,  16  is enhanced, thereby providing additional cooling to the top plate  18 . 
     The electronic components attached to the top plate  18  create heat losses which raise the temperature of the top plate  18 , and create the need for cooling. The middle and bottom plates  14 ,  16  may therefore be mounted to the top plate  18  in order to provide cooling thereto. In use, a fluid inlet component is attached to the connection opening  29  of the fluid inlet connection  28  of the heat exchanger  10  and provides coolant thereto. The coolant flows enters the heat exchanger  10  and flows through the fluid inlet passages and the fluid supply manifold formed by the inlet channel  31   b , the supply channel  24  and the channel sealing bottom plate  16 . The coolant then flows into the cooling channels  20 , different amounts of coolant flow being provided to the various cooling channels  20  as a function of the size of the supply manifold along the inlet end of the array of cooling channels  20 . The cooling channels  20  which are located in areas where the supply channel  24  has a greater cross-section will receive more coolant flow than the cooling channels  20  that are located in areas where the supply channel  24  has a smaller cross-section. The coolant leaves the cooling channels  20  and enters the fluid discharge channel  22  which is sealed by the bottom plate  16  to form a fluid discharge manifold. Thereafter, the coolant enters the fluid passages  31   a  and proceeds to exit the heat exchanger  10  through the connection opening  29  of the fluid outlet connection  30 . A fluid outlet connection attached to the connection opening  29  of the fluid outlet connection  30  may then receive the coolant flow for further usage. 
     The cooling is provided by heat transfer from the top plate  18  to the middle plate  14  and into the coolant flowing through the cooling channels  20 , the heat losses of the electronic components thereby being transferred to the coolant. Due to the use of different electronic components and different positioning configurations of the electronic components on the top plate  18 , the top plate  18  may experience variations in temperature, such that the top plate has a higher temperature at certain locations and a lower temperature at other locations. As such, it may be necessary to vary the amount of cooling provided at different locations of the top plate  18 . As seen above, this may be achieved by varying the cross-sectional areas of the unequal fluid supply and fluid discharge channels  22 ,  24 , such that more coolant is provided in cooling channels  20  adjacent where the locations of the top plate  18  have a higher temperature and require additional cooling. 
     The coolant used with the heat exchanger may be any heat transfer fluid including flammable liquids like jet fuel. Because the second surface  21  of the first plate  14  is interposed between the holes  38  in the third plate  18  and the cooling channels  20 , the coolant flowing through the cooling channels  20  is prevented from leaking through the holes  38  and contacting the electronic components located on the third plate  18 . The heat exchanger is specifically designed to be able to safely accommodate flammable liquids as a coolant. 
     The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, it is apparent that the present heat exchanger could be used to exchange heat (i.e. to heat or cool) any suitable surface, object or fluid adjacent the assembly. Any suitable arrangement of heat-exchanging conduits may be employed. The heat exchanger need not be plate-like, but may be any suitable configuration. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.