Patent Publication Number: US-11391523-B2

Title: Asymmetric application of cooling features for a cast plate heat exchanger

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 62/647,116 filed on Mar. 23, 2018. 
    
    
     BACKGROUND 
     A plate fin heat exchanger includes adjacent flow paths that transfer heat from a hot flow to a cooling flow. The flow paths are defined by a combination of plates and fins that are arranged to transfer heat from one flow to another flow. The plates and fins are created from sheet metal material brazed together to define the different flow paths. Thermal gradients present in the sheet material create stresses that can be very high in certain locations. The stresses are typically largest in one corner where the hot side flow first meets the coldest portion of the cooling flow. In an opposite corner where the coldest hot side flow meets the hottest cold side flow the temperature difference is much less resulting in unbalanced stresses across the heat exchanger structure. Increasing temperatures and pressures can result in stresses on the structure that can exceed material and assembly capabilities. 
     Turbine engine manufactures utilize heat exchangers throughout the engine to cool and condition airflow for cooling and other operational needs. Improvements to turbine engines have enabled increases in operational temperatures and pressures. The increases in temperatures and pressures improve engine efficiency but also increase demands on all engine components including heat exchangers. 
     Turbine engine manufacturers continue to seek further improvements to engine performance including improvements to thermal, transfer and propulsive efficiencies. 
     SUMMARY 
     In a featured embodiment, a cast plate heat exchanger includes a first surface including a first surface inlet end and a first group of augmentation features defining a first average density of augmentation features across the first surface. A second surface is in heat transfer communication with the first surface. The second surface includes a second surfaces inlet end and a second group of augmentation features defining a second average density of augmentation features across the second surface. A total augmentation feature density ratio is defined from the first average density of augmentation features to the second average density of augmentation features. A first region is shared by both the first surface and the second surface and covers at least a portion of the first surface inlet end. The first region includes a first region augmentation feature density ratio that is less than the total augmentation feature density ratio. 
     In another embodiment according to the previous embodiment, the first region covers at least a portion of the second surface inlet end. 
     In another embodiment according to any of the previous embodiments, the first region extends a length not more than 10% of a total length between the first surface inlet end and a first surface outlet end. 
     In another embodiment according to any of the previous embodiments, the first region augmentation feature density ratio is up to 20% less than the total augmentation feature density ratio. 
     In another embodiment according to any of the previous embodiments, the first region augmentation feature density ratio is up to 15% less than the total augmentation feature density ratio. 
     In another embodiment according to any of the previous embodiments, the density of augmentation features in the second group is up to 225% greater than a density of augmentation features in the first group within the first region. 
     In another embodiment according to any of the previous embodiments, the density of augmentation features in the second group is up to 200% greater than a density of augmentation features in the first group within the first region. 
     In another embodiment according to any of the previous embodiments, the first group of augmentation features and the second group of augmentation features include at least one of a trip strip, a depression and a pedestal integrally formed as part of one of the first surface and the second surface. 
     In another embodiment according to any of the previous embodiments, the first group of augmentation features and the second group of augmentation features include augmentation features that are the same. 
     In another embodiment according to any of the previous embodiments, the first group of augmentation features and the second group of augmentation features include differently shaped augmentation features. 
     In another embodiment according to any of the previous embodiments, the second surface includes an outer surface exposed to a cooling flow and the first surface comprises an inner surface exposed to a hot flow. 
     In another embodiment according to any of the previous embodiments, the first region is disposed adjacent a joint between the cast plate heat exchanger and a manifold. 
     In another embodiment according to any of the previous embodiments, the first region is disposed adjacent a joint between the cast plate heat exchanger and another structure. 
     In another embodiment according to any of the previous embodiments, the outer surface is disposed between fins. 
     In another embodiment according to any of the previous embodiments, the inner surface includes internal walls separating a plurality of passages for the hot flow. 
     In another featured embodiment, a cast plate heat exchanger includes a plate portion including outer surfaces, a leading edge, a trailing edge, and internal passages in heat transfer communication with the outer surfaces. A first group of augmentation features on walls of the internal passages is disposed between an inlet side and an outlet side. The first group of augmentation features defines a first average density of augmentation features. A second group of augmentation features is on the outer surfaces. The second group of augmentation features define a second average density of augmentation features. A total augmentation feature density ratio is defined from the first average density of augmentation features to the second average density of augmentation features. A first region shared by both the first group and the second group includes a first region augmentation feature density ratio that is less than the total augmentation feature density ratio. 
     In another embodiment according to the previous embodiment, the plate portion includes a total length between the inlet side and the outlet side and a length of the first region is no more than 10% of the total length from the inlet side. 
     In another embodiment according to any of the previous embodiments, fin portions extend from the outer surfaces and the second group of augmentation features are disposed between the fin portions. 
     In another embodiment according to any of the previous embodiments, the first region augmentation feature density is up to 20% less than the total augmentation feature density ratio. 
     In another embodiment according to any of the previous embodiments, the second average density of augmentation features is up to 225% greater than the first average density of augmentation features within the first region. 
     Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an example heat exchanger assembly. 
         FIG. 2  is an exploded view of another example heat exchanger assembly. 
         FIG. 3  is a perspective view of a portion of the example heat exchanger assembly. 
         FIG. 4  is a schematic cross-section along a longitudinal plane of a portion of an example plate. 
         FIG. 5  is another schematic cross-section of the example plate. 
         FIG. 6  is a schematic view of augmentation features arranged in internal passages of the example plate. 
         FIG. 7  is a schematic view of augmentation features arranged on an outer surface of the example plate. 
         FIG. 8  is another schematic view of augmentation features arranged within internal passages of the example plate. 
         FIG. 9  is another schematic view of augmentation features arranged on the outer surface of the example plate. 
         FIG. 10A  is a top view of example augmentation features within an internal passage. 
         FIG. 10B  is a side view of augmentation features within an internal passage. 
         FIG. 11A  is a top view of another augmentation feature within the internal passage. 
         FIG. 11B  is a cross-sectional view of the augmentation features shown in  FIG. 11A  within the internal passage. 
         FIG. 12A  is top view of yet another augmentation feature within the internal passage. 
         FIG. 12B  is a cross-sectional view of the augmentation features within the internal passage shown in  FIG. 12A . 
         FIG. 13A  is a top view of augmentation features on an outer surface. 
         FIG. 13B  is a side view of the augmentation features shown in  FIG. 13A . 
         FIG. 14A  is a top view of another example group of augmentation features on the outer surface. 
         FIG. 14B  is a side view of the augmentation features shown in  FIG. 14A . 
         FIG. 15A  is top view of yet another group of augmentation features on the outer surface. 
         FIG. 15B  is a side view of the augmentation features shown in  FIG. 15A . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an example heat exchanger is schematically shown and indicated at  10  and includes a plurality of plates  12  disposed between an inlet manifold  14  and an outlet manifold  16 . Each of the plates  12  include internal passages for hot airflow  18  and external surfaces exposed to a cooling airflow  20 . The plates  12  are one single unitary part that is either cast or formed using other manufacturing techniques that provide a one piece part. The plates  12  are secured to the inlet manifold  14  at a first joint  22  and to the outlet manifold  16  at a second joint  24 . The joints  22  and  24  are exposed to differences in temperature between the cooling airflow  20  and the hot airflow  18 . 
     In the example heat exchanger  10  a high temperature gradient area schematically shown at  26  is located at a position where the coolest of the cooling airflow  20  meets the hottest of the hot flow  18 . In the area  26 , a thermal gradient between cooling airflow  20  and hot airflow within the plates  12  is at its greatest. In contrast, an opposite corner  25  wherein the hottest of the cooling airflow  20  and the coolest of the hot flow  18  meet generates the smallest thermal gradient. The difference in thermal gradients within the areas  26  and  25  can create stresses within the joints  22  and  24 . 
     Referring to  FIGS. 2 and 3  with continued reference to  FIG. 1 , another heat exchanger assembly  28  is schematically shown and includes a plurality of plates  34  attached to an inlet manifold  30  at a first joint  36 . The plates  34  are also attached to an outlet manifold  32  at an outlet joint  40 . Each of the joints  36  and  40  encounter mechanical stresses caused by uneven thermal gradients within each of the plate structure  34  caused by the differences in temperature between the cooling airflow  20  and the hot airflow  18 . In this example, a high stress area indicated at  44  along with lower stresses throughout other areas create mechanical stresses that are most evident in the joints  36  and  40 . 
     Each of the disclosed example plates  34  include features to reduce the thermal gradients relative to the high stress locations to reduce mechanical stresses. It should be appreciated that although joints are shown and described by way of example that other high stress locations and interfaces are within the contemplation of this disclosure. 
     Referring to  FIGS. 4 and 5 , each of the example plates  12 ,  34  include inner passages  46  with inner surfaces that are disposed in heat transfer communication with adjacent outer surfaces. In this disclosure heat transfer communication is used to describe opposing surfaces of a common wall, or adjacent wall through which thermal energy is transferred. 
     In each of the plates  12 ,  34  the inner passages  46  are separated from the outer surface  48  by a common wall. The inner surfaces defined by the passages  46  are exposed to hot flow  18  and the outer surface  48  is exposed to cooling airflow  20 . In this example embodiment, each of the outer surface  48  and the passages  46  include heat augmentation features  50 . The augmentation features  50  improve thermal transfer between the hot and cold flows by providing additional surface area and by tailoring flow properties to further enhance thermal transfer. 
     The augmentation features  50  are arranged in a density for a defined area to tailor thermal transfer to minimize mechanical stresses. Variation of heat augmentation density between augmentation features  50  on the outer surface  48  and the passages  46  enable tailoring of thermal transfer and thereby enable adjustment of thermal gradients to reduce stresses on a joint such as the joint schematically indicated at  56 . 
     An equal number of augmentation features disposed in the passage  46  and on the outer surface  48  does not consider thermal differences across the plate  12 ,  34 . The example disclosed plates  12 ,  34  include groups of augmentation features  50  that are proportionally arranged to reduce thermal gradients relative to mechanical interfaces such as the example joint  56 . 
     Referring to  FIGS. 6 and 7  with continued reference to  FIGS. 4 and 5 , the internal passages  46  are schematically illustrated in  FIG. 6  and include a group of augmentation features  50  that improve the transfer of thermal energy from the hot airflow  18  through the passage walls into the outer surface  48 . 
     Both the internal passages  46  and outer surface  48  are shown adjacent to a joint  56 . The example joint  56  is an interface that includes mechanical stresses that are greatest in the region  58 . Stresses in the joint  56  increase in a direction indicated by arrow  75  toward the region  58 . The example plates  12 ,  34  include a disclosed relative arrangement of augmentation features to provide more uniform thermal gradients that reduce stresses in the joint  56 . Moreover, although a joint  56  is illustrated schematically by way of example, any interface subject to mechanical stress would benefit from the features described in this disclosure. 
     In the plates  12  and  34  the outer surface  48  is on top and bottom surfaces and is heat transfer communication with the walls of the passages  46 . The example plates  12 ,  34  include a length  52  that begins at the joint  56  and extends the entire length of the passages  46 . A first region  55  is disposed within a length  54  from the joint  56  and a second region  57  is disposed at the end of the first region  55  to the end of the plate  12 ,  34 . In one disclosed embodiment the first region  55  is disposed within the length  54  that is no more than 10% of the total length  52 . In another disclosed embodiment, the first region  55  is within the length  54  that is no more than 7% of the total length. 
     Within the first region  55 , the number of augmentation features  50  within the passages  46  is different than the number of augmentation features  50  within the same first region  55  on the outer surface  48 . It should be understood, that variation in the number of augmentation features is discloses by way of example, but any difference in number, structure, shape of the augmentation features that changes the thermal transfer capability through the adjoining wall could be utilized and is within the contemplation of this disclosure. 
     In the example disclosed in  FIGS. 6 and 7 , the outer surface  48  includes a second group  67  of augmentation features  50  that includes an equal number of augmentation features  50  disposed at a uniform density along the entire length  52  to define a second average density of augmentation features. The passage  46  includes a first group  65  of augmentation features  50  that define a first average density of augmentation features for all the augmentation features across the length  52 . The first average density of augmentation features and the second average density of augmentation features are related according to a total augmentation feature density ratio that relates augmentation features in the first and second groups to each other. 
     In the disclosed example, the passage  46  does not include any augmentation features within the first region  55 . Accordingly, a ratio of the first group of augmentation features to the second group of augmentation features within the first region is different than for than the total augmentation feature density of augmentation features. In one disclosed embodiment, a first region augmentation feature density ratio is less than the total augmentation feature density ratio. 
     In one disclosed example embodiment, a density of augmentation features  50  disposed on the outer surface  48  relative to a density of augmentation features within the passage  46  differs to vary the differing densities of heat augmentation features within the passage  46  and the outer surface  48  reduces thermal stresses in the blade and the joint. 
     In another disclosed embodiment, the first region augmentation feature density ratio is up to 20% less than the total augmentation feature density ratio. In this disclosed embodiment, the reduced density ratio is provided by reducing the group of first augmentation features provided in the passage  46  as compared to the group of second augmentation features  50  provided on the outer surface  48 . 
     In yet another embodiment, the first region augmentation feature density ratio is up to 15% less than the total augmentation feature density ratio. In this example embodiment, the density of augmentation features  50  in the first group  65  within the passage  46  is reduced as compared to the second group  67  provided on the outer surface  48  within the first region  55 . Although the disclosed examples include a reduction in augmentation features in the first group within the passage  46 , the different ratios may also be provided by increasing the number of augmentation features within the second group on the outer surface and is within the scope and contemplation of this disclosure. 
     In another disclosed embodiment, the density of augmentation features  50  within the second group  67  disposed on the outer surfaces  48  is up to 225% greater than the first group  65  provided in the first passage  46 . In another disclosed example embodiment, the density of augmentation features  50  within the second group  67  is up to 200% greater than the first group  65  in the passages  46 . The differing density of augmentation features  50  enables tailoring of thermal transfer to reduce stresses within the interface provided by the joint  56 . 
     It should be appreciated that the application of additional heat transfer augmentation devices within the passage  46  increases heat flow into the material. In contrast, the reduction of heat transfer augmentation devices within the passages  46  reduces the heat flow into that region thereby reducing material stresses. Additionally, the addition of augmentation features  50  on the outer surface  48  will increase heat flow out of that region. Accordingly, specific tailoring of densities of augmentation features  50  within the passages  46  and the outer surface  48  within the first region  54  enables modification and tailoring of thermal gradients to reduce stresses on the joint  56 . 
     Referring to  FIGS. 8 and 9 , another example plate  12 ,  34  is schematically shown to illustrate another example relative orientation between augmentation features  50  within the passages  46  and the outer surface within the first region  54 . 
     In this example the density of augmentation features  50  within the passage  46  is increased in a direction away from the high stress area indicated at  58 . The density of augmentation features  50  provided on the outer surface  48  remain the same. Increasing the density of augmentation features  50  in a direction away from the highest stress region  58  within the passages  46  provides desired reduction in thermal gradients that matches stresses within the joint  56 . Arrow  75  indicates a direction of increasing stress in the joint  56 . The density of augmentation features  50  within the passages  46  is increased in a direction opposite the increasing stress indicated by arrow  75 . The reduced number of augmentation features  50  reduce the thermal transfer in that region to provide a more uniform thermal gradient across the plate  12 ,  34 . 
     Referring to  FIGS. 10A and 10B , an example passage  46  is shown including a plurality of trip strips  60 . The trip strips  60  extend from top and bottom walls  62  of the passage  64 . In this example, the trip strips  60  are integrally formed into the walls  62  to both increase surface area and tailor flow properties of the hot flow  18  to increase thermal transfer. 
     Referring to  FIGS. 11A and 11B , another passage  66  is schematically shown and includes augmentation features in the form of pedestals  70  that extend from walls  62  of the passage  66 . 
     Referring to  FIGS. 12A and 12B , augmentation features formed as indentations or dimples  72  are provided along the walls  62  of the passage  68 . The dimples  72  provide additional surface area along enable the flow to be modified to improve thermal transfer. 
     Referring to  FIGS. 13A and 13B , an example outer surface  74  is shown and includes fins  80  and trip strips  82  between the fins  80 . The trip strips  82  extend from the outer surface  74  and provide additional surface area for thermal transfer. Moreover, the example trip strips  82  are shown as simple angled walls that can direct flow against the fins  80  to provide additional thermal transfer. 
     Referring to  FIGS. 14A and 14B , another outer surface  76  is illustrated with pedestals  84  disposed between the fins  80 . The pedestals  84  extend upward between the fins to enable tailoring of thermal transfer and cooling airflow  20  properties. 
     Referring to  FIGS. 15A and 15B , yet another example outer surface  78  is disclosed including dimples  86  disposed between the fins  80 . The dimples  86  provide for flow conditioning of cooling airflow between the fins  80  as well as improved thermal transfer properties. 
     It should be appreciated, that although several example augmentation feature structures have been disclosed by way of example, that other shapes, sizes and relative orientations could also be utilized and are within the contemplation of this disclosure. 
     The example disclosed augmentation features formed as integral portions of surfaces of each of the plates on both the inner and outer surfaces in a targeted manner to tailor thermal gradients to reduce thermal stresses relative to interfaces and joints. 
     Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this disclosure.