Patent Publication Number: US-11035624-B2

Title: Heat exchanger with integral anti-icing

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 15/332,574 filed Oct. 24, 2016 for “HEAT EXCHANGER WITH INTEGRAL ANTI-ICING” by M. Zager and M. Doe. 
    
    
     BACKGROUND 
     An aircraft heat exchanger is sometimes exposed to icing conditions at its cold inlet face. Cold air flow from the turbine of an air cycle machine or sub-freezing ambient air may contain snow or ice particles that can damage the leading edges of the cold inlet fins. Flow blockages are caused when the leading edges are bent, or when the snow and ice particles accumulate on the cold inlet face at a rate that exceeds its melting capability. Snow or ice particles can also pierce hot fluid passages and cause leaks that reduce system efficiency. 
     One method of providing ice protection is to make the cold air flow bypass the heat exchanger when snow or ice accumulates on the cold inlet face until the face has warmed sufficiently to melt the accumulation. This, however, requires additional parts at the cold inlet face which can be difficult to fit into the available space on an aircraft. Accordingly, there is a need for a cold inlet face design with integral ice-melting features. 
     SUMMARY 
     A heat exchanger includes a plurality of first and second fluid passages. The first fluid passages are defined by a pair of opposing first fluid passage walls and a plurality of first fluid diverters disposed between the first fluid passages walls. The second fluid passages are defined by a pair of opposing second fluid passage walls and a plurality of second fluid diverters disposed between the second fluid passage walls. The second fluid diverters include a body portion and a leading edge portion. The first fluid passage walls form a first fluid leading edge that extends upstream of the leading edge portions of the second fluid diverters. The second fluid passages extend in a direction generally perpendicular to the direction of the first fluid passages. 
     A method of making a heat exchanger comprises: forming a plurality of opposing first fluid passage walls and a plurality of first fluid diverters disposed between the first fluid passages walls, wherein the plurality of first fluid passage walls and first fluid diverters define a plurality of first fluid passages; forming a plurality of opposing second fluid passage walls and a plurality of second fluid diverters disposed between the second fluid passage walls, wherein the plurality of second fluid passage walls and second fluid diverters define a plurality of second fluid passages. The second fluid diverters include a body portion and a leading edge portion. The first fluid passage walls form a first fluid leading edge that extends upstream of the leading edge portions of the second fluid diverters. The second fluid passages extend in a direction generally perpendicular to the direction of the first fluid passages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the cold inlet face of a heat exchanger. 
         FIG. 2  is a cross-sectional view of the heat exchanger of  FIG. 1 . 
         FIG. 3  is a front view of the cold inlet face of the heat exchanger of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of an alternative embodiment of the heat exchanger of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed heat exchanger includes integral ice-melt passages. Additive manufacturing is used to produce a cold inlet face with the ice-melt passages extending upstream of the fins in the cold flow stream. Additional enhancements can also be achieved at the cold inlet face using additive manufacturing. For example, certain surfaces can be thickened, such as the leading edges of the cold fins and the ice melt-passages. Fins can also be added to the inner surfaces of the ice-melt passages. These integral ice-melt features allow for the optimization of the melting capability of the cold inlet face and reduce the amount of materials traditionally required to achieve the design. 
       FIG. 1  is a perspective view of heat exchanger  10  of an aircraft. Heat exchanger  10  includes header  12 , cold inlet face  14 , a plurality of first fluid passages (not labeled in  FIG. 1 ), and a plurality of second fluid passages (not labeled in  FIG. 1 ). Heat exchanger  10  is configured to receive a cold fluid at cold inlet face  14 . The cold fluid can be, for example, air cycle machine turbine exhaust or sub-freezing ram air. Heat exchanger  10  is also configured to receive a hot fluid via header  12 . The hot fluid can be supplied from within the environmental control system. Often times, the hot fluid is engine bleed air after it has been cooled by other heat exchangers. 
     Referring to  FIGS. 2 and 3 , first fluid passages  16  are defined by opposing first fluid passages walls  20 , and first fluid diverters  22 . First fluid diverters  22  are disposed between first fluid passage walls  20 . Walls  20  meet to form leading edge  24 . Leading edge  24  has an inner surface  26 . Walls  20  and leading edge  24  have a uniform thickness T 1 . First fluid passages  16  receive the hot fluid from header  12 . In one embodiment, first fluid passage walls  20  and first fluid diverters  22  are formed from aluminum. In other embodiments, other suitable materials can be used. 
     Second fluid passages  18  are defined by opposing second fluid passage walls  20  and second fluid diverters  32 . Second fluid diverters  32  are disposed between second fluid passage walls  20 . In the embodiment shown, second fluid diverters  32  are configured as fins, but can also be configured as pins, or a combination of fins and pins. Second fluid diverters  32  have a leading edge portion  34 , and a body portion  36 . Leading edge portion  34  has a thickness T 3  that can be greater than a thickness T 4  (not shown) of the body portion. In some embodiments, thickness T 3  can be anywhere from 110% to 500% of thickness T 4 . In one embodiment, second fluid passage walls  20  and second fluid diverters  32  are formed from aluminum. In other embodiments, other suitable materials can be used. 
     First fluid passages  16  extend in a direction D 1 . Second fluid passages extend in a direction D 2  toward outlet end  15 . As can be seen from  FIGS. 2 and 3 , direction D 2  is perpendicular to direction D 1 . 
     The cold fluid flowing into the heat exchanger at cold inlet face  14  does not always flow in a single direction, rather the fluid flow can be multi-directional and swirling in nature. The swirling fluid can contain snow and ice particles. The increased thickness T 3  of leading edge portions  34 , present in some embodiments, protects the second fluid diverters  32  from damage caused by snow and ice particles. Leading edges  24  of first fluid passages  16  extend upstream of leading edge portions  34  of second fluid diverters  32 , which also protects leading edge portions  34  from snow and ice particles. This occurs because leading edge portions  34  are recessed rearward from the incoming cold fluid flow. Further, leading edges  24  of first fluid passages  16  can melt snow and ice particles before they reach second fluid passages  18  because they provide additional hot surface area with which the cold fluid can come into contact and be warmed as it enters cold inlet face  14 . In some embodiments, leading edges  24  of first fluid passages  16  can extend up to approximately twice the width of second fluid passages (cold passages)  18  beyond leading edge portions  34  of second fluid diverters  32  into the upstream flow. 
     Referring to  FIG. 4 , a heat exchanger with additional ice-melt enhancements is shown. First fluid passages  116  are defined by a pair of opposing first fluid passage walls  120 , and first fluid diverters  122 . First fluid diverters  122  are disposed between first fluid passage walls  120 . Walls  120  meet to form leading edge  124 . Leading edge  124  has an inner surface  126 . Leading edge  124  can also have a thickness T 2 . In one embodiment, thickness T 2  is greater than thickness T 1  of the embodiment of  FIG. 2 . That is, leading edge  124  has walls that are thicker than the sidewalls of walls  120  as shown in  FIG. 4 . 
     In another embodiment also shown in  FIG. 4 , leading edge  124  includes finned inner surface  126 ′ to increase the heat transfer surface area of the first fluid passages  116 . In yet another embodiment, leading edge  124  has an increased thickness T 2  and finned inner surface  126 ′. 
     In the disclosed embodiments, the opposing walls, diverters, and leading edges of the first and second fluid passages can be formed from aluminum. However, in other embodiments, other suitable materials, such as steel, nickel alloys, titanium, non-metal materials, or combinations of such materials, can be used. Further, first fluid passages  16 ,  116  of the disclosed embodiments have a parabolic shape, however, the first fluid passages can be formed into other shapes based on the specific need for ice protection at cold inlet face  14 . 
     Heat exchanger  10  can be manufactured by an additive manufacturing process such as, direct metal laser sintering (DMLS), laser net shape manufacturing (LNSM), electron beam manufacturing (EBM), or laminated object manufacturing (LOM), to name a few non-limiting examples. Additive manufacturing techniques can include, for example, forming a three-dimensional object through layer-by-layer construction of a plurality of thin sheets of material, or through powder bed fusion. Heat exchanger  10  can be designed to have optimal melting capabilities based on parameters such as flow volume and temperature. 
     Heat exchanger  10  can be additively manufactured by forming a plurality of first and second fluid passage walls and diverters, which define a plurality of first and second fluid passages. The first fluid passage walls form a first fluid leading edge. The second fluid diverters include a body portion, and a leading edge portion that can be made to have a thickness 110% to 500% of that of the body portion during the manufacturing process. The first fluid leading edges are formed to extend upstream of the leading edge portions of the second fluid diverters. 
     Additional ice-melt enhancements can be included during the manufacturing process. For example, the first fluid passage walls and the first fluid leading edges can be made thicker. Further, the inner surface of the first fluid leading edges can be finned to increase the heat transfer surface area within the first fluid passages. 
     It will be appreciated that heat exchanger  10  is formed by additive manufacturing using techniques that will allow it to conform to the available space on an aircraft or other structure without influencing the placement of other components. 
     DISCUSSION OF POSSIBLE EMBODIMENTS 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A heat exchanger includes a plurality of first and second fluid passages. The first fluid passages are defined by a pair of opposing first fluid passage walls and a plurality of first fluid diverters disposed between the first fluid passages walls. The second fluid passages are defined by a pair of opposing second fluid passage walls and a plurality of second fluid diverters disposed between the second fluid passage walls. The second fluid diverters include a body portion and a leading edge portion. The first fluid passage walls form a first fluid leading edge that extends upstream of the leading edge portions of the second fluid diverters. The second fluid passages extend in a direction generally perpendicular to the direction of the first fluid passages. 
     The heat exchanger of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The second fluid diverters are selected from the group consisting of fins, pins, and combinations thereof. 
     The body portion of the second fluid diverter has a first thickness, and the leading edge portion of the second fluid diverter has a second thickness. 
     The second thickness ranges from about 110% to about 500% of the first thickness. 
     The first fluid passage walls have a first wall thickness, and the first fluid passage leading edge has a second thickness greater than the first wall thickness. 
     The first fluid passage leading edge has an inner surface, and wherein the inner surface comprises fins. 
     The plurality of first and second fluid passage walls and diverters are formed from aluminum. 
     The plurality of first and second fluid passage walls and diverters are formed from a material selected from the group consisting of steel, nickel alloys, titanium, non-metal materials, and combinations thereof. 
     A method of making a heat exchanger comprises: forming a plurality of opposing first fluid passage walls and a plurality of first fluid diverters disposed between the first fluid passages walls, wherein the plurality of first fluid passage walls and diverters define a plurality of first fluid passages; forming a plurality of opposing second fluid passage walls and a plurality of second fluid diverters disposed between the second fluid passage walls, wherein the plurality of second fluid passage walls and diverters define a plurality of second fluid passages. The second fluid diverters include a body portion and a leading edge portion. The first fluid passage walls form a first fluid leading edge that extends upstream of the leading edge portions of the second fluid diverters. The second fluid passages extend in a direction generally perpendicular to the direction of the first fluid passages. 
     The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The method includes increasing a thickness of the leading edge portion of the second fluid diverter by about 110% to about 500% relative to a thickness of the body portion of the second fluid diverter. 
     The method includes forming the first fluid passage leading edge such that it has a thickness greater than a thickness of the first fluid passage walls downstream of the first fluid passage leading edge. 
     The method includes forming fins on an inner surface of the first fluid passage leading edge. 
     The method includes forming the heat exchanger by additive manufacturing. 
     The method includes forming the heat exchanger from aluminum. 
     The method includes forming the heat exchanger from a material selected from the group consisting of steel, nickel alloys, titanium, non-metal materials, and combinations thereof. 
     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.