Abstract:
The disclosure includes a heat exchanging apparatus, comprising a heat exchanger plate comprising a plurality of flow passages, and wherein each flow passage comprises at least one surface feature configured to change the flow characteristics of a linear flow along an axis of flow for the flow passage. The disclosure further includes a method of constructing a heat exchanger, comprising using additive manufacturing to form a first plate having a plurality of flow passages, wherein each of the flow passages has one or more integrally formed surface features, wherein the integrally formed surface features are configured to change the flow characteristics of a fluid flowed linearly along an axis of flow for the flow passage.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority benefit of U.S. Patent Application 62/196,713 filed Jul. 24, 2015 entitled ENHANCED HEAT TRANSFER IN PRINTED CIRCUIT HEAT EXCHANGERS, the entirety of which is incorporated by reference herein. 
     
    
     TECHNOLOGICAL FIELD 
       [0002]    Exemplary embodiments described herein pertain to three dimensional (3D) printing/additive manufacturing. More specifically, some exemplary embodiments described herein apply 3D printing/additive manufacturing to change the heat transfer and/or flow characteristics of printed circuit heat exchangers. 
       BACKGROUND 
       [0003]    This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art. 
         [0004]    Generally, conventional heat exchangers accomplish heat transfer from one fluid to another across a heat exchange surface. In plate type heat exchangers, fluids exchange heat while flowing through heat exchange zones between adjacent (stacked) peripherally sealed thin metal heat exchanger plates. Plate type heat exchangers offer the benefits of counter-current thermal contact, a large easily adjustable surface area-to-volume ratio, and relative compactness. Plate type heat exchangers are the most popular alternative to the more conventional shell-and-tube type heat exchangers for these reasons. Heat exchanger plates may be manufactured by pressing, embossing or other techniques known in the art to create long lengths of corrugated patterns and/or interleaving ridges forming plate paths, flow channels, and/or flow passages, wherein indirect heat exchange may take place between fluids disposed on either side of the ridges. These processes generally aim to produce a uniform, smooth, and defect-free flow passage. However, room for improvement exists in this technology and efficiencies may be increased. 
         [0005]    Printed Circuit Heat Exchangers (PCHE) provide the ability to exchange large quantities of energy between numerous streams in a compact unit as compared to conventional shell-and-tube heat exchangers. The heat exchanger plate layers of these PCHE are comprised of sheets of metal into which the desired flow passage arrangement is chemically etched. Each flow passage may be approximately 2.0 millimeters (mm) wide and 1.0 mm deep. Each heat exchanger plate, sheet, or layer of flow passages may have representative dimensions of 600 mm in width and 1,500 mm in length. Multiple heat exchanger plates may be stacked and placed into a vacuum furnace, wherein the collection of these individual layers becomes one solid piece via a process called diffusion bonding. A representative depth of a final assembly or core may be 600 mm. Multiple assemblies or cores may be joined together to form a final heat exchanger unit. Chemical etching aims to produce a uniform, smooth, and defect-free flow passage. However, room for improvement exists in this technology and efficiencies may be increased. 
         [0006]    Additive manufacturing techniques are increasingly used in manufacturing. Typically, additive manufacturing techniques start from a digital representation of the object to be formed generated using a computer system and computer aided design and manufacturing (CAD/CAM) software. The digital representation may be digitally separated into a series of cross-sectional layers that may be stacked or aggregated to form the object as a whole. The additive manufacturing apparatus, e.g., a 3D printer, uses this data for building the object on a layer-by-layer basis. Additional background information is known in the art and may be found in U.S. Patent Applications 2014/0205454, 2014/0163717, 2014/0154088, 2014/0124483, 2013/0310961, 2013/0320598, 2013/0316183, and 2013/0149182, and European Patent Application 2675583, each of which is hereby incorporated by reference in their entirety. 
       SUMMARY 
       [0007]    This disclosure includes a heat exchanging apparatus, comprising a heat exchanger plate comprising a plurality of flow passages, and wherein each flow passage comprises at least one surface feature configured to change the flow characteristics of a linear flow along an axis of flow for the flow passage. 
         [0008]    The disclosure further includes a method of constructing a heat exchanger, comprising using additive manufacturing to form a first plate having a plurality of flow passages, wherein each of the flow passages has one or more integrally formed surface features, wherein the integrally formed surface features are configured to change the flow characteristics of a fluid flowed linearly along an axis of flow for the flow passage. 
         [0009]    The disclosure additionally includes a method of using a heat exchanging apparatus, comprising flowing a first fluid through a first flow passage, wherein flowing comprises passing the fluid along the first flow passage, disturbing a flow of the fluid using a plurality of surface features disposed at regular intervals along an axis of flow for the flow passage, wherein the plurality of surface features allow the flow of fluid to continue flowing along the axis of flow for the flow passage, and flowing a second fluid through a second flow passage, wherein heat is exchanged between the first fluid and the second fluid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific example embodiments is not intended to limit the disclosure to the particular forms disclosed herein, but on the contrary, this disclosure is to cover all modifications and equivalents as defined by the appended claims. It should also be understood that the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating principles of exemplary embodiments of the present invention. Moreover, certain dimensions may be exaggerated to help visually convey such principles. 
           [0011]      FIG. 1  is an exemplary exploded view of a conventional welded plate frame heat exchanger. 
           [0012]      FIG. 2  is a perspective view of a conventional PCHE plate. 
           [0013]      FIG. 3  is a perspective view of another conventional PCHE plate. 
           [0014]      FIG. 4  is a cross-section view of a first embodiment heat exchanger plate having flow passage sections each having a different flow passage profile. 
           [0015]      FIG. 5  is a cross section view of a second embodiment heat exchanger ate a flow passages each having a different flow passage profile. 
           [0016]      FIG. 6  is a perspective view a third embodiment of a heat exchanger plate. 
           [0017]      FIG. 7  is a perspective view a fourth embodiment of a heat exchanger plate. 
           [0018]      FIG. 8A  is a top view of a first embodiment flow passage having surface features extending vertically into the respective flow passage. 
           [0019]      FIG. 8B  is a top view of a second embodiment flow passage having surface features extending vertically into the respective flow passage. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Exemplary embodiments are described herein. However, to the extent that the following description is specific to a particular, this is intended to be for exemplary purposes only and simply provides a description of the exemplary embodiments. Accordingly, the invention is not limited to the specific embodiments described below, but rather, it includes all alternatives, modifications, and equivalents falling within the true spirit and scope of the appended claims. 
         [0021]    The present technological advancement can capture technology opportunities through the use of additive manufacturing as a technique to change various operating characteristics for PCHE-type heat exchangers. Current techniques aim to produce a uniform, smooth, and defect-free flow passage. However, the present disclosure includes techniques to produce irregular flow passages that can change flow characteristics for flow within and/or along a channel to improve overall heat transfer along the channel. Moreover, the present disclosure accomplishes this technique as enabled by new and previously unavailable manufacturing capabilities that permit the present techniques to precisely control what variations are placed within and/or along a channel and with what frequency within a precise tolerance, e.g., to within ±2 mm, ±1.5 mm, ±1 mm, ±0.75 mm, ±0.5 mm, ±0.25 mm, ±0.1 mm, ±0.05 mm, etc. Thus, the present advancement provides an alternative solution to the problem described above in a unique way by teaching away from earlier developments. 
         [0022]    As used herein, the phrase “additive manufacturing” means a process of creating a three dimensional (3D) item of manufacture/equipment, where successive layers of material are laid down to form a three-dimensional structure. Exemplary 3D printing techniques include, but are not limited to, Scanning Laser Epitaxy (SLE), Selective Laser Sintering/Hot Isostatic Pressing (SLS/HIP), Fused Deposition Modeling, foil-based techniques, and direct metal laser sintering (DMLS). 
         [0023]    As used herein, the phrase “aggregate flow” means a flowing fluid understood in its bulk entirety within the context of a flow passage and not viewed or analyzed in discrete, disaggregated portions or segments. For example, an aggregate flow may be described as generally having a single, horizontal direction of flow along an axis of flow for a flow passage while comprising discrete, lesser portions therein of eddy, turbulent, or other limited cross- or counter-directional flow with respect to the aggregate flow. A flow passage will have a single direction of aggregate flow along an axis of flow for that flow passage or portion thereof 
         [0024]    As used herein, the phrase “indirect heat exchange” means the bringing of two fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other. 
         [0025]    As used herein, the phrase “integrally formed” means constructed, fabricated, manufactured, printed, sintered, and/or machined such that the component is comprised of the same unitary material as the substrate. As used herein, the phrase “integrally formed” does not mean brazed, welded, embedded, bonded, or otherwise affixed or coupled as one component onto a second component, e.g., as with an inline valve, flow restrictor, baffle, etc. as conventionally installed along a flowpath. Integrally forming a structure on a substrate explicitly includes fabricating a component on a substrate by one or more additive manufacturing techniques. Integrally forming a structure on a substrate includes forming the component as a negative space, channel, depression, cavity, or other such space along the substrate. Integrally forming a structure on a substrate may occur at the same time as fabrication of the substrate. 
         [0026]    As used herein, the phrase “flow passage profile” means the cross-sectional shape of the relevant flow passage. For example, flow passage profiles may be generally circular, triangular, oblong, rectangular, polygonal, etc., or any combination thereof. 
         [0027]    As used herein, the phrase “flow passage wall” means any outer boundary of a given flow passage, including any applicable sides, floors, and/or ceilings for a given flow passage. 
         [0028]    As used herein, the term “fluid” means gases, liquids, and combinations of gases and liquids, as well as to combinations of gases and solids, and combinations of liquids and solids. 
         [0029]    As used herein, the term “substantial” when used in reference to a quantity or amount of a material, or a specific characteristic thereof, refers to an amount that is sufficient to provide an effect that the material or characteristic was intended to provide. The exact degree of deviation allowable may depend, in some cases, on the specific context. 
         [0030]      FIG. 1  is an exemplary exploded view of a conventional welded plate frame heat exchanger  100 . Heat exchanger  100  (e.g., a plate frame exchanger (PFE)) includes a core  102  and various frame and housing components. The core  102  includes a plurality of metal plates that are configured to transfer heat between fluids  104  and  106 . The metal plates are compressed together in a rigid frame to form an arrangement of parallel flow passages with alternating hot fluids  104  and cold fluids  106 . The metal plates may be corrugated plates, e.g., having intermating and/or chevron corrugations, and the flow passages themselves may be strictly linear or may have a wavy, a zigzag, or other shape pressed into the plate. 
         [0031]      FIG. 2  is a perspective view of a conventional PCHE plate  202 , e.g., the heat exchanger plate of core  102  of  FIG. 1 , having a plurality of flow passages  204  extending from an inlet section  206 , along an intermediate section  208 , and to an outlet section  210 . The flow passages  204  are arranged in parallel and are substantially uniform along their respective axis of flow. 
         [0032]      FIG. 3  is a perspective view of another conventional PCHE plate  302 , e.g., the heat exchanger plate of core  102  of  FIG. 1 , having a plurality of flow passages  304  extending from an inlet section  306 , along a wavy intermediate section  308 , and to an outlet section  310 . The flow passages  304  are arranged in parallel and are substantially uniform along their respective axis of flow. Each flow passage of the wavy intermediate section  308  comprises two curved edges (sides) directing an aggregate flow through various axis of flow depending on the position of aggregate flow in the wavy intermediate section  308 . 
         [0033]      FIG. 4  is a cross-section view of a heat exchanger plate  402 , e.g., the heat exchanger plate of core  102  of  FIG. 1 , having flow passage sections  404 - 418  each haying a different flow passage profile. The flow passage profiles of the flow passage sections  404 - 418  depict a variety of flow passage depths, widths, sidewall slopes, and shapes. Various embodiments of heat exchanger plates as described herein may comprise one or more of these flow passage sections  404 - 418 , and may do so in a manner wherein different flow passage sections having different flow passage profiles are situated adjacently (as illustrated), in series, or in any combination thereof. Additional designs for flow passage sections disclosed herein having different flow passage profiles include flow passage profiles with generally circular shapes, triangular shapes, oblong shapes, rectangular shapes, polygonal shapes, etc., or any combination thereof Other embodiments may change in measurement from one flow passage to another or along the length of a single flow passage, e.g., by varying the surface feature extension height, surface feature recess depth, surface feature diameter, and/or surface feature curvature. For example, each wall of the flow passage section  416  comprises an integrally formed surface feature  420  that extends partially into the associated flow passage. The surface features  420  as depicted extend into between 1% and 49% of the illustrated flow passage width, permitting some portion of fluid to flow between opposing surface features  420  for each flow passage of the flow passage section  416 . Alternate embodiments may further restrict flow and permit no fluid to pass between opposing surface features  420 . Still other embodiments may permit a relatively greater amount of fluid to pass between opposing surface features  420 , e.g., by extending between 1%-10%, 1%-20%, 1%-30%, 1%-40%, 1%-45%, 10%-20%, 10%-30%, 10%-40%, 10%-45%, 20%-30%, 20%-40%, 20%-45%, 30%-40%, 30%-45%, or 40%-45% of the flow passage width. In some embodiments, the flow passage width is approximately 2.0 millimeters (mm) wide and approximately 1.0 mm deep. While the surface features  420  are depicted as extending from the top of the walls of the flow passage section  416 , any location along the boundary of the flow passage may be employed as a surface feature mounting location within the scope of this disclosure. As described above, some flow passage sections may be placed in series, and in such embodiments an average flow passage width may be used for measuring the extension of the surface features  420 . Additionally or alternatively, those of skill in the art will appreciate that a single surface feature extending from a single wall of a flow passage may be used to accomplish the same characteristics, e.g., by extending between 1%-50%, 1%-60%, 1%-70%, 1%-80%, 1%-90%, 10%-50%, 10%-60%, 10%-70%, 10%-80%, 10%-90%, 20%-50%, 20%-60%, 20%-70%, 20%-80%, 20%-90%, 30%-50%, 30%-60%, 30%-70%, 30%-80%, 30%-90%, 40%-50%, 40%-60%, 40%-70%, 40%-80%, 40%-90%, 50%-60%, 50%-70%, 50%-80%, 50%-90%, 60%-70%, 60%-80%, 60%-90%, 70%-80%, 70%-90%, or 80%-90% of a flow passage width, within the scope of the present disclosure. In some embodiments, the flow passage width is approximately 2.0 millimeters (mm) wide and approximately 1.0 mm deep. 
         [0034]      FIG. 5  is a cross section view of a heat exchanger plate  502  having flow passages  504  and  506  each having a different flow passage profile. The components of  FIG. 5  may be substantially the same as the corresponding components of  FIG. 4  except as otherwise noted. Integrally formed surface features  508 - 512  extend from a flow passage wall into the flow passages  504  and  506 . The surface features  508 - 512  are mounted along an axis different from the axis of flow for the associated flow passages  504  and  506 , namely, perpendicular to the axis of flow. Some embodiments may space the surface features  508 - 512  at regular intervals along the mounting axis, along the axis of flow, or both. The surface features  508 - 512  may be configured to create an eddy flow, a turbulent flow, or otherwise obstruct flow. The surface features  508 - 512  may be configured as needle- or pin-type extensions, fin-type extensions, bumps, ridges, scallops, divots, or another protrusion or recess for changing flow characteristics. The surface features  508 - 512  may be configured to accelerate flow along the axis of flow for the flow passage, e.g., as a nozzle, or may be configured to create a cyclonic flow along the axis of flow, e.g., as fins, rifling, etc. The depicted surface features  508  and  510  are of differing shape and size, while the depicted surface features  512  are of uniform shape and size. While depicted as adjacent flow passages, those of skill in the art will appreciate that alternate embodiments may place flow passages  504  and  506  in non-adjacent locations, e.g., on separate heat exchanger plates of core  102  of  FIG. 1 . Those of skill in the art will appreciate that alternate embodiments may create surface features by recessing the surface features  508 - 512  into the walls of the respective flow passages  504  and  506 . 
         [0035]      FIG. 6  is a perspective view a heat exchanger plate  602  having flow passages  604 - 608  as enabled by the techniques disclosed herein. The components of  FIG. 6  may be substantially the same as the corresponding components of  FIG. 5  except as otherwise noted. The walls of the flow passages  604 - 608  comprise flow paths  610 . While the depicted flow paths  610  permit fluid communication between the adjacent flow passages  604 - 608 , other embodiments of flow paths  610  may permit fluid communication between non-adjacent flow passages, e.g., as tunnels through flow passage walls or across the flow channel(s) of the flow passages. In some embodiments, such flow paths may extend from plate-to-plate rather than from flow passage-to-flow passage along a single plate. 
         [0036]      FIG. 7  is a perspective view of a heat exchanger plate  702  having flow passages  704 - 708  as enabled by the techniques disclosed herein. The components of  FIG. 7  may be substantially the same as the corresponding components of  FIG. 6  except as otherwise noted. The top walls of the flow passages  704 - 708  comprise pores  710 . The pores  710  permit fluid communication from plate-to-plate rather than from flow-passage-to-flow passage as enabled by the flow paths  610  of  FIG. 6 . The pores  710  are depicted as triangular but alternate embodiments may optionally select from any suitable configuration to obtain a desired flow characteristic. 
         [0037]      FIGS. 8A and 8B  are top views of flow passages  802   a  and  802   b  having surface features  804   a  and  804   b  extending vertically into the respective flow passages. The components of  FIGS. 8A and 8B  may be substantially the same as the corresponding components of  FIG. 7  except as otherwise noted. Flow through the flow passages  802   a  and  802   b  is depicted with dashed lines. As depicted, flow across the surface features  804   a  may result in eddy flow. Additionally, the surface features  804   b  may be configured for flow to pass through, e.g., as nozzles, flow directors, slats, or other surface features configured to admit the passage of flow therethrough, as depicted by the dashed lines extending through the surface features  804   b.  Disturbing the flow through the flow passages  802   a  and  802   b  may increase the relative thermodynamic mixing of flow through the flow passages  802   a  and  802   b,  thereby increasing the efficiency of the associated heat exchanger, e.g., the plate frame heat exchanger  100  of  FIG. 1 . Alternately or additionally, the surface features  804   a  and/or  804   b  may be used to obtain a desired pressure change across the length of the flow passages  802   a  and son. 
         [0038]    The present techniques may be susceptible to various modifications and alternative forms, and the examples discussed above have been shown only by way of example. However, the present techniques are not intended to be limited to the particular examples disclosed herein. Indeed, the present techniques include all alternatives, modifications, and equivalents falling within the spirit and scope of the appended claims.