CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application 62/382,722, filed September 1, 2016, and titled "STRUCTURAL HEAT

EXCHANGER," the disclosure of which is incorporated herein by reference in its entirety and for all purposes.

TECHNICAL FIELD

[0002] The subject matter disclosed herein generally relates to coolant systems. More specifically, the present disclosures relate to a structural heat exchanger with various industrial applicabilities.

BACKGROUND

[0003] Conventionally, coolant systems for industrial applications are manufactured using subtractive manufacturing methods, meaning that larger materials are used which are whittled down until a desired structure is created. These designs are therefore limited by the manufacturing methods employed. In addition, coolant systems are conventionally built with multiple pieces, needing to be welded and fastened together. For ease of manufacturing and replicability, these designs therefore exhibit numerous failure points or other high stress areas. In addition, due to utilizing more reliable subtractive manufacturing methods, optimal geometries for heat transfer, and cooling designs are not used. It is desirable therefore to develop new ways of generating heat exchanging coolant systems and their various components. BRIEF SUMMARY

[0004] Aspects of the present disclosure are presented for a structural heat exchanger design with optimal heat transfer and cooling properties that may be created using additive manufacturing techniques.

[0005] In some embodiments, a heat exchanger includes: a housing including: a wall at least partially enclosing a region containing a high volume of heat relative to surrounding volumes; and a plurality of coolant channels each defined by vacant channel space within the wall, the coolant channels configured to allow fluid to flow within the wall; wherein the housing is manufactured using additive manufacturing.

[0006] In some embodiments, of the heat exchanger, each of the plurality of coolant channels has at least a portion of cross-sectional area in a shape of a bean.

[0007] In some embodiments of the heat exchanger, each of the plurality of coolant channels has at least a portion of cross-sectional area in a shape of a trapezoid with rounded corners.

[0008] In some embodiments of the heat exchanger, each of the plurality of coolant channels has at least a portion of cross-sectional area having a shape with parallel concave curves, wherein one of the concave curves is located nearest an inner wall side closest to the high heat volume region, and a second of the concave curves is located nearest an outer wall side farthest from the high heat volume region.

[0009] In some embodiments, of the heat exchanger, each of the plurality of coolant channels has at least a portion of cross-sectional area in a shape defined by satisfying a plurality of boundary conditions defining one or more functional or structural properties of the wall. In some embodiments, the plurality of boundary conditions include: at least one thermal condition that the wall must satisfy; at least one structural condition that the wall must satisfy; at least one material property about the wall that the wall must satisfy; and at least one material property of the coolant channels that the plurality of coolant channels must satisfy. In some embodiments, the plurality of boundary conditions is a first plurality of boundary conditions applied to a first location of the coolant channels, and each of the plurality of coolant channels has at least a portion of cross-sectional area at a second location in a second shape defined by satisfying a second plurality of boundary conditions that are different than the first plurality of boundary conditions.

[0010] In some embodiments of the heat exchanger the plurality of coolant channels vary in pitch angle at different locations within the wall.

[0011] In some embodiments of the heat exchanger at least one of the plurality of coolant channels includes a first cross-sectional area at a first location shaped in a first shape, and a second cross-sectional area at a second location shaped in a second shape. In some embodiments, the first shape is a bean shape, and the second shape is an ellipse shape.

[0012] In some embodiments of the heat exchanger the plurality of coolant channels vary in size of cross-sectional area at different locations within the wall.

[0013] In some embodiments of the heat exchanger the wall is shaped as a cylinder.

[0014] In some embodiments of the heat exchanger the wall includes a flat plate housing at least a portion of the plurality of coolant channels.

[0015] In some embodiments of the heat exchanger the housing is manufactured as a single piece using additive manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Some embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings. [0017] FIG. 1 provides a description of a traditional coolant system that serves as a point of comparison to highlight the novel and nonobvious features of the present disclosures.

[0018] FIG. 2 shows a fuel diverter have a uniform annular radius.

[0019] FIG. 3 shows a fuel diverter in the shape of a decreasing radius annulus, according to some embodiments.

[0020] FIG. 4 shows an illustration of fluid being delivered through each channel out of the fluid diverter.

[0021] FIG. 5 shows an illustration of a flow vector simulation of the direction and magnitude of the liquid as it enters the offshoot passages from the fluid diverter, according to some embodiments.

[0022] FIG. 6 shows a semi-transparent view of the bottom of an engine utilizing a heat exchanger of the present disclosures.

[0023] FIG. 7 shows a closer view of the fuel diverter that has a much smaller radius by the end of it, as it wraps around the circumference of the bottom of the engine.

[0024] FIGS. 8a and 8b show cross sections of typical cooling channels and their heat transfer properties.

[0025] FIGS. 9, 10, and 11 depict trapezoidal passages as cross-sectional areas of cooling passages, in and according to some embodiments of the present disclosures.

[0026] FIG. 12 shows a bean shape for a cross-sectional area of the cooling passages, according to some embodiments.

[0027] FIG. 13 illustrates how the top portions of the cooling passages may be shaped more like circles or ovals. [0028] FIG. 14 shows a top-down view of the regenerative cooling passages according to some embodiments.

[0029] FIGS. 15-16 show different views of how the pitch, cross-sectional shape, and sizes of the cooling passages may change as the channels flow up along the chamber walls of a structure, according to some embodiments.

[0030] FIG. 17 depicts an example of a cross-sectional area of a bean coolant channel.

[0031] FIG. 18A shows what a cylinder wall looks like with rectangular coolant channels, while FIG. 18B shows an example of what the cylinder looks like with bean- shaped channels.

[0032] FIG. 19 shows the thermal contours for the results of the rectangular cross sectional channel.

[0033] FIG. 20 shows the thermal contours for the results of the circular cross sectional channel.

[0034] FIG. 21 shows the thermal contours for the results of the bean-shaped cross sectional channel.

[0035] FIG. 22 shows magnified visual results of the rectangular cross section to accentuate the temperature banding.

[0036] FIG. 23 shows magnified visual results of the circular cross section to accentuate the temperature banding.

[0037] FIG. 24 shows magnified visual results of the bean-shaped cross section to accentuate the temperature banding.

[0038] FIGS. 25 and 26 show an example of a flat plate from different angles having bean-shaped coolant channels, according to some embodiments. [0039] FIGS. 27 and 28 show a flat plate on the top surface with bean-shaped coolant channels, but with a wavy surface on the bottom that coincides with the concave geometry of the bean shapes.

[0040] FIG. 29 shows a flowchart of an example methodology for developing a structural heat exchanger having any number of coolant channels, with any variety of cross-sectional shapes, built to satisfy varying needs of a variety of industrial applicabilities, according to some embodiments.

[0041] FIG. 30 is a block diagram illustrating components of a machine, according to some example embodiments, able to read instructions from a machine- readable medium and perform any one or more of the methodologies discussed herein.

DETAILED DESCRIPTION

[0042] Coolant systems for various industrial applications rely on traditional, subtractive, manufacturing methods for their production. As a result, their designs reflect the limitations of the manufacturing methods employed. High performance industrial devices are typically created in more than one piece, and are welded or fastened together, using o-rings or other gaskets to seal high pressure regions. These designs exhibit numerous failure points.

[0043] Producing coolant systems through additive manufacturing (AM) offers a multitude of previously unseen improvements. The ability to print a series of heat exchanger channels in a single piece using AM techniques increases durability and usability while reducing weight. The speed at which additive manufacturing methods are able to produce components outpaces even the most agile traditional manufacturing operation, as well. The ability to produce novel geometries, which were not previously achievable using traditional manufacturing, has opened the door to countless performance improvements. [0044] Indeed, the additive manufacturing approach enables the production of even the most complex geometries. This allows designers to create optimized structures without the burden of designing for traditional manufacturing techniques.

[0045] Aspects of the present disclosure are presented for a structural heat exchanger design with optimal heat transfer and cooling properties that may be created using additive manufacturing techniques. The heat exchanger may be generated as a single piece, having no joints, fasteners, or any other areas that could present a risk for damage. The designs, and principles for deriving the designs, as described herein may also reduce weight of the industrial device, due to eliminating the need for fasteners and other extraneous hardware. In general, the weight of the industrial device may be optimized to also preclude the inclusion of extraneous material around needed structures. Also, the industrial device may be designed to be highly energy efficient, with optimal flows for fuel and other fluid with minimal head loss while maintaining higher pressures.

[0046] In some embodiments, a structural heat exchanger is presented that utilizes liquid fuel as a coolant as it travels through the perimeter of a high temperature engine chamber. The shapes of the coolant channels, starting from the fuel diverter and flowing through the heat exchanger passages, may be configured to change angles as it travels to the top of the high temperature engine chamber, to account for areas of the chamber that may demand higher cooling properties. In some embodiments, the fuel diverter that allows initial passage of the fuel through the coolant channels may be configured to drive passage of the fluid up through the coolant channels with uniform pressure, even as the volume of fluid decreases the farther the fluid travels from the initial entry point. In some embodiments, this may be implemented as a fuel diverter shaped in an annulus with a gradually decreasing radial cross-section.

[0047] In some embodiments, the cross-sectional area of the coolant channels may be specifically shaped to satisfy certain objectives or boundary conditions. For example, a boundary condition may specify that the coolant channels should produce uniform thermal flux, to reduce heat strain on any particular point along and within the wall of the industrial device. In some embodiments, this may be achieved by generating the coolant channels to have cross-sectional areas in the shape of a trapezoid, or in other cases a bean shape. In some embodiments, the trapezoidal or bean shape of the coolant channels may be gradually converted to an oval or circular shape along the course of the channel as the coolant channels approach the fuel injector portion of the engine and the fluid is about to be dispensed.

[0048] In some embodiments, a method is presented for deriving designs of the coolant channels based on satisfying multiple boundary condition properties. These properties can include having an inner wall meet a certain heat flux condition, having the wall containing the channels meet a certain heat capacity, having a certain portion of the channels reach a particular pressure condition, and changing these properties at various different locations along the path of the channels, to meet various needs at particular locations.

[0049] In some embodiments, a structural heat exchanger includes a plurality of coolant channels that have varying cross-sectional areas. In addition, for any single coolant channel, the cross-sectional area may change shape gradually, to satisfy changing boundary conditions at those locations. In some embodiments, the layout of the coolant channels may be in the shape of a cylinder, a flat plate, a wavy plate, or other arrangement consistent with the principles of the present disclosure.

[0050] The structural heat exchanger according to various embodiments described herein may be used in a wide variety of non-limiting industrial applications, including: gas generator turbomachinery, power generation heat exchanges, automotive engines, HVAC units, server cooling modules, and applications with needs for high performance heat exchange, like power plant reactors and various vehicles with high demand for power. [0051] FIG. 4 provides a description of a traditional engine design that supplies context for coolant channels in a heat exchanger and serves as a point of comparison to highlight the novel and nonobvious features of the present disclosures. Here, shown is a cross-sectional shape of typical regenerative cooling channels, using traditional manufacturing. The multi-material traditional manufacturing tends to result in rectangular regen cooling channels.

[0052] As previously mentioned, aspects of the present disclosure provide for a structural heat exchanger with regenerative coolant channels, typically housed in an engine that is designed and manufactured in ways that address any and all of these issues found in typical engine design and manufacturing.

[0053] Referring to FIGS. 2-7, embodiments of a fuel diverter are discussed that address a number of the issues described, according to some embodiments.

[0054] Referring to FIG. 2, a fuel diverter with a uniform annular radius is shown. The fuel diverter may be positioned at the bottom of the engine, to allow fuel to flow up along the walls of the engine to act as coolant before the fuel is injected at the top of the chamber. The grayscale gradient shows a turbulence simulation of regenerative cooling through an additively manufactured engine. Non-uniform turbulence present in the diverting section of this engine indicates an ineffective diverter design.

[0055] Referring to FIG. 3, a fuel diverter in the shape of a decreasing radius annulus is presented, according to some embodiments. In order to reduce turbulence and ensure an equal mass flow of fuel to each of the regenerative cooling channels that are fed by the fuel diverter (e.g., 48 total cooling channels), a decreasing radius annulus fuel diverter may be used. The annulus begins with a diameter equal to that of the fuel inlet and decreases proportionally to the amount of fuel that is diverted off into each of the branching channels. This results in a constant pressure annulus with equal mass flow delivered to each channel. This ensures the even cooling of the chamber wall by the regen cooling and subsequently, the proper distribution of fuel injected by the attached fuel injector passages. Standard diverting passageways do not account for pressure drops due to turbulence. This results in unexpected and uneven distributions of mass flows among the various identical diverting channels. Such a non-uniform distribution of fluid can result in potentially destructive hotspots and instabilities.

[0056] FIG. 4 shows an illustration of fluid being delivered through each channel out of the fluid diverter. The grayscale gradient shows that the pressure drop at each passage is identical, which is in part due to the decreasing radius of the annulus.

[0057] FIG. 5 shows an illustration of a flow vector simulation of the direction and magnitude of the liquid as it enters the offshoot passages from the fluid diverter, according to some embodiments. As shown, the directions of the fluid offshoot are generally uniform, in that the turbulent flow is generally evenly distributed as it enters the passage. In addition, the magnitude of each flow vector is generally the same length, indicating generally uniform pressure as well. This illustration may be representative at each passageway, due to the decreasing radius of the fluid diverter.

[0058] In general, the diverter geometries depicted in FIGS. 4 and 5 demonstrate how the decreasing annular diverter can feed a desired mass flow rate to an arbitrary number of passages. It maintains a directional flow of fuel at all times where the flow direction and the fluid pathway, determined by the geometric domain, are maximally uniform. This design is capable of feeding many orifices with a desired mass flow rate. The branching orifices may be identical or may vary in size, if a specific non-uniform distribution of mass flows among the orifice is desired. The decreasing annular diverter is capable of maintaining the desired mass flow rates over a wide range of input conditions, such as pressure or mass flow rate. It can also be used to deliver optimal flow rates of various fluid phases, reacting, or unsteady flows, by taking these changes into account when producing a constant pressure annulus.

[0059] The diverter design of the present disclosures may also be applied to other fluid passages, according to some embodiments. For example, the decreasing radius annulus design of the diverter described herein may be applied to an injector orifice interface, or in general any set of fluid passages that utilizes one or few fluid entry points and delivers fluid to many or multiple fluid passages with substantially uniform pressure drop.

[0060] Referring to FIG. 6, shown is a semi-transparent view of the bottom of an engine, illustrating the fuel diverter 610 in the context of other components, according to some embodiments. These include the fuel inlet 605 and the nozzle 615. The multiple coolant channels are also shown. As shown, and with a closer view in FIG. 7, the fuel diverter 610 has a much smaller radius by the end of it, as it wraps around the circumference of the bottom of the engine. In some embodiments, the end of the fuel diverter may be connected to the beginning, to form a closed loop, while in other cases the ends are disconnected. FIG. 7 also shows how the fuel inlet is coupled to the entry passage of the fuel diverter.

[0061] Referring to FIGS. 8A-16, embodiments of regenerative cooling channels are discussed that address a number of the issues described above, according to some embodiments.

[0062] Regenerative (or regen) cooling is widely used in as a means of removing heat from an engine chamber inner wall. Cooling channels reside within an inner wall, which may be contained generally in a casing or housing structure as part of the whole engine or other structure. A pressurised fluid is fed through the channels embedded within, or wrapped around, a chamber wall. The fluid is used as a moderating fluid into which heat flows. This process cools the chamber wall: preventing material degradation, melting, undesirable phase transitions or grain transformation, and increasing component longevity.

[0063] Standard regen cooling schemes include: wrapping the chamber in small fluid-transporting channels, manufacturing rectangular channels into the wall of the engine, and manufacturing circular channels into the engine wall. Additive manufacturing allows for the implementation of numerous advanced channel designs which may not be producible using traditional manufacturing methods.

[0064] Referring to FIGS. 8A and 8B, cross sections of typical cooling channels, and their heat transfer properties, are shown. Rectangular channels are commonly used because of their ease of fabrication and good heat transfer properties. Rectangular channels also provide a large gas-side wall surface area for increased heat transfer as opposed to other geometric shapes. However, this method is not optimal because of the poor temperature distribution caused by the rectangular shape. The sharp edges of the rectangular channels cause stress concentrations at the corners of each individual channel, as evidenced by the uneven color gradient at the corners in FIG. 8B. While stress concentrations caused by sharp edges are unfavorable, this method is still commonly used because of the ease of manufacturing.

[0065] Circular channels are structurally favorable according to certain criteria, since they distribute the pressure force in all directions, preventing stress

concentrations. Similarly, the maximized surface area of a circular channel enhances heat flow into the moderating fluid. However, arrays of circular channels, distributed azimuthally about the axis of the chamber, produce uneven distributions of temperature along the inner wall off the chamber material itself, resulting in significant thermal stress.

[0066] While more optimal from a pressurized and thermal perspective, non- circular and non-rectangular geometries for the coolant channels are much more difficult to create using traditional manufacturing techniques. The performance, durability, and longevity benefits they provide are outweighed by increased

manufacturing costs and additional pieces or components needed to create such advanced geometries. However, these geometries can be created rapidly and precisely through additive manufacturing at a very low cost. [0067] Trapezoidal passages depicted in FIGS. 9, 10, and 11 and according to some embodiments of the present disclosures, offer some benefits of both circular and rectangular passages. They are also easily producible through additive manufacturing. Greater gas side wall surface area enable greater heat transfer into the moderating fluid. Rounded edges and a narrowed cross section closer to the outer wall provides increased management of stresses due to high differentials in pressure, caused by the high fluid pressure within the channels, and thermal considerations, which lead to thermal stresses through spatial variances in thermal expansion. FIG. 9 depicts the thermal profile along the inner wall of a trapezoidal regenerative cooling channel during normal use. The trapezoidal channels reduce temperature gradients along the inner wall. FIG. 10 shows a graphical simulation of the thermal flux of trapezoidal coolant channels. As shown, the temperature gradients around the coolant channels are more even throughout, reducing any stress points along any corners or edges. FIG. 11 shows another illustration of the thermal flux in an elongated portion of the trapezoidal coolant channel design. Even when the channel is curved, the thermal flux properties remain constant along the same portion of the respective edges and corners.

[0068] One novel idea for a regenerative cooling channel comes from the discovery that an even temperature profile could be achieved with a non-constant channel cross section. Through novel design methods, a cross section with a near-even temperature profile was created. This shape will be referred to as a "bean" shape, and one example implementation of the coolant channels with this shape is shown in FIG. 12. Pressure distribution is uniform within the bean channel. Distribution of equivalent stresses is not uniform throughout the wall section, but is optimized to a minimum by the bean channel for the given thermo-structural boundary conditions, according to some embodiments.

[0069] Other variants to the bean shape may be contemplated by the present disclosures herein, such as the cross-sectional area having a "macaroni" shape with the inner and outer wall edges of the coolant channel shaped in a parallel concave pattern (also like the bean), but with the lateral sides more straight (to look like the profile of a bent piece of macaroni), rather than curved (like the bean). Variants that gradually morph between these various shapes are also contemplated, as additive manufacturing can allow for each cross-sectional layer to gradually change shape between one another.

[0070] FIG. 13 illustrates how the top portions of the cooling passages may therefore be shaped more like circles or ovals, to account for this. Thus, in some embodiments, the cooling passages are designed to gradually transition from a shape designed for cooling and better heat transfer (e.g., trapezoid or bean shape) to a more uniform shape before the fluid finishes traveling. In addition, the shape of the passages toward the beginning of the passages, i.e., as the fuel is delivered from the fuel diverter to each of the cooling passages, may be more like the oval shape, and then may gradually change to the more cooling-optimal shape. These transitions will be described in more detail, below.

[0071] FIG. 14 shows a top-down view of the regenerative cooling passages, according to some embodiments.

[0072] FIGS. 15-16 show different views of how the pitch, cross-sectional shape, and sizes of the cooling passages may change as the channels flow up along the chamber walls, according to some embodiments. Typically, cooling channels using traditional manufacturing are never varied with any of these degrees. However, due to properties available in additive manufacturing techniques, these cooling channels can be adjusted in various ways to account for the different needs at different points along the engine walls.

[0073] In general, variations in channel cross section shape, size, and pitch can be used to specifically tune the turbulence and therefore the heat transfer. This can be used to control the heat transfer as well as the temperature and pressure of the moderating fluid. This is particularly important for ensuring that the temperature and pressure of a supercritical moderating fluid is past the critical point and gasification or liquidation is avoided, as these are potentially damaging to the engine. Increasing and decreasing the cross sectional area of the channel enables the axial optimization of heat transfer into the fluid.

[0074] FIG. 15 shows a bottom-up view of the cooling channels, with their different pitch angles and shape changes at the varying sections, according to some embodiments. This view shows just the portion rising into the throat (see FIG. 16), as the remaining portions of the channels flowing out of the throat widen and thus would be out of view. From this perspective, the changing angle along a single channel indicates a changing pitch. Also, it can be seen that the cross-sectional area of a single channel changes, from a circular area to a bean shape.

[0075] FIG. 16 shows a closer view of the throat area of the cooling passages, according to some embodiments. As shown, cooling passages are arranged helically, and at this juncture, the pitch angle is changed to be more horizontal (i.e., increased), in addition to the passages being closer together, as well as the sizes of the channels decreased. In general, none of these properties are easily reproducible using traditional manufacturing techniques.

[0076] Further Details on the "Bean" Coolant Channel

[0077] This section discusses various features inherent to the use of bean shaped fluid channels within heat exchangers.

[0078] As background and as previously mentioned in part, fluid heat exchangers use coolant filled channels to transfer heat from a solid to the cooler fluid.

Traditionally, the channels have been limited to rectangular and circular designs. While rectangular channels have heat transfer rates greater than those of circular channels, their corners are structural weak points due to stress concentrations. To avoid choosing between structural stability and efficient heat transfer, engineers have attempted to modify the rectangular geometry to achieve better structural traits without sacrificing heat transfer, but the results yielded little actual benefit. [0079] Through research and development, an enhanced channel cross section has been developed: the bean. Pictured in FIG. 17, the bean is shaped exactly as its name implies. The shape combines the structural curves of the circular channel with the high surface area of the rectangular channel to create a highly efficient and structurally sound heat transfer channel. FIG. 17 depicts an example of a cross-sectional area of a bean coolant channel.

[0080] In addition to combining the structural benefits of both traditional geometries, the bean shaped channel provides a more even heat transfer across the length of the wall. It lacks the extreme peaks and valleys in temperature inherent to the standard geometries. This even distribution reduces thermal stresses in the wall caused by large thermal gradients and non-uniform rates of thermal expansion.

[0081] Simulations were conducted to compare the effectiveness of heat transfer between the rectangular, circular, and bean shaped channels. A cylinder with an annular cross section and cooling channels running along the length was modeled for each geometry. These channels were designed so that the individual channel cross sections, the total fluid domain area, and the minimum distance from the inner wall were near equal. The rectangular channel simulation geometry in FIG. 18A serves as a

representative example for all three. FIG. 18A shows what the cylinder looks like with rectangular channels, while FIG. 18B shows an example of what the cylinder looks like with bean-shaped channels. It therefore can be similarly contemplated how the circular and other shaped channels would be positioned around the cylinder as well.

[0082] In one example set of simulations, ANSYS 17.1 was used to conduct steady state coupled fluid-heat transfer simulations to capture the heat transfer effects of both convection and conduction. Nickel was used for the solid, while liquid kerosene was used for the liquid. The inside wall of the geometry was set to 726 °C, while the outside wall along with the top and bottom faces were modeled as insulated. The inlets were defined with a total mass flow rate 0.2 kg/s and a temperature of 27 °C. [0083] Thermal contours for the results of each geometry can be found in FIGS. 19, 20, and 21, for the rectangular cross sectional channel, the circular cross sectional channel, and the bean-shaped cross sectional channel, respectively. The thermal advantages of using rectangular cooling channels over circular ones can be seen through the lower temperatures, as well as less heat penetration through the wall. Table 1, below, confirms these visual indicators, as both the average and minimum

temperature of the rectangular channels are lower when compared to those of the circular channels' . However, according to FIG. 21, the bean' s increase in efficiency is clearly evident. The bean effectively cools the chamber compared to both geometries while maintaining the structurally advantageous curves of the circular geometry. Table 1 validates the bean' s superiority with the lowest minimum and average temperatures at 490.28 °C and 561.36 °C, respectively.

[0084] Table 1 : Temperature results for the rectangular, circular, and bean channels

[0085] When the result visuals are magnified to accentuate the temperature banding, as seen in FIGS. 22, 23, and 24, for the rectangle, circle, and bean-shaped cross sectional channels, respectively, the even distribution of heat transfer in the bean channels is easily seen. The grayscale gradient shows more clearly the banded temperature contours of each of the different types of cross-sectional channels. While the rectangular channels may have an exceptional geometry in regard to heat transfer rate, they have incredibly uneven temperature gradients along their walls. The circular geometry improves upon this uneven heat transfer, but is subpar in its cooling. The bean shows itself to be more effective in both important metrics.

[0086] Recent advances in simulation and optimization software, combined with additive manufacturing, have allowed for the creation of optimized bean shaped fluid heat exchanger geometries. These bean shaped fluid channels combine the best of both rectangular and circular cooling channels. They have the superior heat exchanging ability of rectangular channels while maintaining the strength characteristics of the circular channels. In addition, this geometry also allows for the more even extraction of heat, which in turn helps reduce thermal stress within the wall being cooled. These characteristics enable the bean geometry to be far superior to the circular and rectangular designs of the past.

[0087] Additional Example Embodiments of Structural Heat Exchanger [0088] Multiple Channel Implementation

[0089] In some embodiments, structural heat exchanger channels may be combined in a truss-like arrangement including trapezoidal or bean-shape channel cross sections, combined in a way to satisfy a particular set of advanced boundary conditions. This may include large pressure or heat fluctuations across a plate wherein the gas side wall may alternate from one face of the heat exchanger to the other. This embodiment is exceedingly practical for counter-current heat exchanger flows where alternating channels are fed by outgoing or returning coolant.

[0090] Flat Plate

[0091] Bean channel heat pipes may be implemented into non-circular cross section geometries. These may include flat or curved plates as well as more

complicated, predictably varying geometries. FIGS. 25 and 26 show an example of a flat plate from different angles having bean-shaped coolant channels, according to some embodiments. As another example, FIGS. 27 and 28 show a flat plate on the top surface with bean-shaped coolant channels, but with a wavy surface on the bottom that coincides with the concave geometry of the bean shapes. In this example embodiment, the thermal properties of the bottom surface allow for more uniform temperature loss along the bottom surface.

[0092] Nonuniform Heat

[0093] The structural heat exchanger can be easily implemented for thermal boundary conditions which change along the principal component of the coolant flow and channel direction. For thermal boundary conditions which are spatially and/or time varying in a direction primarily perpendicular to the major component of the coolant flow or channel direction, there must be additional treatment of the channel geometries. Channel sizing must be modified to increase flow velocity and therefore turbulence at the cost of pressure drop. This is accomplished by smoothly transitioning each heat exchanger channel to corresponding bean-like geometry with a reduced or increased cross sectional area to increase or decrease flow velocity corresponding to the peak thermal load present across the heat exchanger surface at a particular location.

Alternatively, increased mass flow can be delivered to channels with spatially and/or time varying thermal loads.

[0094] Nonuniform Flow

[0095] In an ideal heat exchanger, coolant can be fed to uniform channels such that each channel has either identical mass flow, or a specific distribution of flow corresponding to the thermal loading. However, if an even and steady distribution of coolant across all channels is not possible, alterations to the channel geometries may be made to take this into account. These modifications may take the form of resized and/or reshaped bean channels corresponding to the heat flux and flow available.

[0096] Example Industrial Applications

[0097] The following are descriptions of uses for various types of the heat exchanger of the present disclosure: [0098] Gas generator turbo machinery: coolant channels may be embedded into cylindrical walls of a compressor or expander cycle (or within the blades themselves).

[0099] Power Generation Heat Exchanges: cylindrical structural heat exchanger with and without conforming internal surfaces are ideal for transporting heat from a working fluid into a moderating fluid (or coolant)

[00100] Automotive Engines: Cylindrical heat exchanger used within each combustion cylinder. The channels may have identical boundary conditions to an engine thruster. The fuel or coolant can be used to remove heat from the wall, enabling higher operating temperatures and reduced thermal losses.

[00101] HVAC unit: The flat plate may be used in HVAC systems as opposed to standard fin and pipe heat exchanger.

[00102] Server cooling: The bean cooling channels can be used in high

performance computing environments to pull heat from a chip, instead of a combustion environment. The flat plate employing the coolant channels may also be used in this case.

[00103] Other examples of the structurally optimized heat exchangers of the present disclosures may also be applied in jet engines, tooling bits, mining bits, brake disk rotors, and injection molds.

[00104] Example Method of Generating Coolant Channels

[00105] This section discusses a computer-implemented method for generating and deriving the various cross-sectional areas of the coolant channels described herein. As previously mentioned, the structures housing the channels may be additively manufactured, meaning the structure may be constructed layer by layer using known additive manufactured techniques, like a 3D printer accessing a CAD file with all of the properties and specifications for where to place the solid material to form the structure with the channels. Developing that CAD file, for example, is a non-trivial task that a computer-implemented method of the present disclosure is able to develop.

Furthermore, the method may gradually change the cross-sectional area of any and all channels, layer by layer, to form different shapes at different locations along the same channel (see e.g., FIG. 15).

[00106] Referring to FIG. 29, flowchart 2900 provides an example methodology for developing a structural heat exchanger having any number of coolant channels, with any variety of cross-sectional shapes, built to satisfy varying needs of a variety of industrial applicabilities. In some cases, a computer-implemented method for designing a structural heat exchanger could be made by manually designing the shapes and structures. However, in order for a structural heat exchanger to be better suited to satisfy the cooling properties desired for a given use case, more precise engineering should be employed. Flowchart 2900 provides an example for how a computer goes about generating such a structural heat exchanger to satisfy the specified needs.

[00107] At block 2905, one or more boundary conditions are defined and accessed by a computer configured to implement the method, according to some embodiments. These inputs may be provided by human engineers who have computed the various needs, or who may be following specifications provided by other authorities. Various CAD or CAE (Computer Aided Engineering) tools may be used to calculate and then determine these boundary conditions. The boundary conditions can include any number of the following non-limiting examples:

[00108] Thermal: Heat Flux, Ambient/Initial Temperatures, Coolant Flow Rate, Surface Roughness, Radiative Heating/Cooling

[00109] Structural: Internal Pressure, Channel Pressure, External Pressure, Structural Loadings

[00110] Material Properties of Structure: Density, Tensile/Yield Strength, Fracture Toughness, Thermal Conductivity, Thermal Expansion, Thermal Diffusivity, Emissivity, Melting/Boiling Point, Built-in Internal Stresses, Heat Capacity, Specific Heat, Gain Morphology and Phase Change Information

[00111] Material Properties of Coolant: Density, Thermal Conductivity, Thermal Diffusivity, Emissivity, Melting/Boiling Point, Heat Capacity and Specific Heat

[00112] Material properties will vary in temperature and/or pressure. Not all properties listed are necessary. An accurate listing of these material properties, and others, varying over temperature and pressure will result in simulation results that are highly representative of the physical environment seen by the heat exchanger.

[00113] As an example, the structural heat exchanger boundary conditions which create an optimal environment for bean channel implementation include:

An interior (gas side wall) high heat flux condition;

A high heat capacity, low temperature coolant flowing rapidly through the channels while maintaining a liquid phase state;

A pressure condition Pcc>Pw>Po,

Where:

Pec: Pressure inside coolant channel;

Pw: Pressure seen by high heat flux wall;

Po: Ambient pressure at exterior of heat exchanger.

[00114] The computer utilized these boundary conditions and conducted the methodology described herein to derive the bean-shaped geometry that has proven to be a superior coolant channel.

[00115] In some embodiments, multiple sets of boundary conditions may be defined, each for different locations of the heat exchanger in order to meet different cooling needs at the various locations. The boundary conditions therefore can be made specific to different locations. [00116] At block 2910, initial geometry of the structural heat exchanger housing the coolant channels may be created with the aides of CAD and CAE tools, according to some embodiments. This may be viewed as like an initial seed starting value, where an initial approximate guess as to what the best geometry might be can be inputted and received by the computer. A human developer may help create an initial geometry which roughly satisfies all boundary conditions. In some embodiments, the computer may provide suggestions using known solutions that it can verify roughly satisfy the boundary conditions to some threshold degree. A channel count and size may be selected, depending on the available coolant mass flow. This should be done to minimize boundary layers within cooling channels as well as prevent edge cases such as supersonic flow.

[00117] At block 2915, the general channel shape may be defined. Again, this may also be defined by a human engineer with the input received by the computer, or the computer may be configured to suggest a suitable shape, based on the initial boundary conditions. Again, this may be viewed as an initial seed starting value, where the initial approximate guess as to what the best shape should be can be provided in the computer. For example, the general bean channel shape may be defined, characterized by an inner and outer edge typically with differing radii of curvature and a curved portion connecting these edges on either side to form a closed channel.

[00118] At block 2920, with the initial parameters and objectives defined, the computer may now conduct one or more optimization simulations on at least a subset of the heat exchanger geometry. In some cases, this involves running coupled

computational fluid dynamics and finite element analysis (CFD/FEA) simulations. The computer may simulate either a representative subset or the entire heat exchanger geometry in order to further define boundary conditions and determine the thermal loading of the fluid.

[00119] At block 2925, the computer may then conduct optimization simulations on slices of the deconstructed heat exchanger geometry. The whole geometry may be first decomposed into slices by the computer running the simulations. These slices may represent sets of layers created through additive manufacturing. For example, the slices may be horizontal layers of the heat exchanger shown in either FIGS. 18A or 18B. The computer may then utilize macro boundary conditions from the previous step in block 2920 to run a geometric optimization of the internal channels and/or the wall structure they reside in. In other words, the optimization techniques may be isolated to smaller sections of the heat exchanger geometry. The coupled CFD/FEA simulations may be performed on each of the slices, according to some embodiments.

[00120] For example, in the case of the converging diverging nozzle (see e.g., FIG. 16), this is represented by changes to the inner and outer diameter of various slices rings. Given that the thermostructural characteristics of the optimized beans vary with the wall thickness and bean spacing, it is important to optimize each slice ring.

Additionally, the layer by layer method follows the trajectory of the fluid and therefore is capable of taking the heating of the coolant (reduced thermal conductivity over distance) into account.

[00121] In the process of refining the shapes of the channels and the geometry overall, the computer may create a structure that changes the cross-sectional area of the coolant channels at various locations. For example, for areas that have lower need for cooling properties but have higher need for uniform mass flow, or that feed into other more uniform shapes, the heat exchanger may have channels whose cross-sectional area gradually changes from a bean shape to an oval shape.

[00122] Furthermore, the pitch angle of the coolant channels may be changed, to account for the boundary conditions. For example, as shown in FIG. 22, different sections of the single heat exchanger piece have parallel channels that change their pitch angle flowing upward, based on different cooling needs at the different locations. Surface area by the aggregate coolant channels is increased when the pitch angle is made less steep (more horizontal), which can thereby increase the heat transfer rate. [00123] During the simulations, the computer simulates the geometry multiple times, and each time small changes to the geometry are made by either the computer or with assistance by a human operator to attempt to meet a set performance criteria. The simulation is then run again to see if the changes were effective. The process repeats until the criteria are met. At block 2930, the computer may determine whether there is convergence and an optimization goal has been satisfied. If they have not, then the process may repeat, starting back at block 2920. Convergence may be achieved when the geometry and the channel shapes stop changing after the simulations are run and adjustments are made. The computer may optimize each slice repeatedly until one or more of the following optimization goals are met:

Matching with prescribed factor of safety criterion;

Low stress concentrations between channels;

Minimal divergence of thermal gradients along the inner wall representing thermal stresses; and

Symmetric channels given symmetric flow and thermal conditions.

[00124] At block 2935, assuming that the optimization goal has been met and convergence of the structure is achieved, the resulting heat exchanger is then analyzed. The analysis is performed to ensure, via testing or coupled system simulation that, performance criteria are met and operating conditions set. This helps ensure that the resulting cross sections are smoothly assembled and that all constituents as well as the geometry as a whole are manufacturable based on the feature-specific resolutions of the additive manufacturing device. In some cases, if this analysis reveals flaws, then repeat simulation optimization as necessary.

[00125] Embodiments of the present disclosure also include example techniques for producing any and all of the various components of the structural heat exchanger embodiments as described herein. In addition, embodiments also include any and all software or other computer-readable media used to program machines for

manufacturing said components, and embodiments are not so limited.

[00126] Referring to FIG. 30, the block diagram illustrates components of a machine 3000, according to some example embodiments, able to read instructions 3024 from a machine-readable medium 3022 (e.g., a non-transitory machine-readable medium, a machine-readable storage medium, a computer-readable storage medium, or any suitable combination thereof) and perform any one or more of the methodologies discussed herein, in whole or in part. Specifically, FIG. 30 shows the machine 3000 in the example form of a computer system (e.g., a computer) within which the instructions 3024 (e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine 3000 to perform any one or more of the methodologies discussed herein may be executed, in whole or in part.

[00127] In alternative embodiments, the machine 3000 operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 3000 may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a distributed (e.g., peer-to-peer) network environment. The machine 3000 may include hardware, software, or combinations thereof, and may, as example, be a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a cellular telephone, a smartphone, a set-top box (STB), a personal digital assistant (PDA), a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing the instructions 3024, sequentially or otherwise, that specify actions to be taken by that machine. Further, while only a single machine 3000 is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute the instructions 3024 to perform all or part of any one or more of the methodologies discussed herein.

[00128] The machine 3000 includes a processor 3002 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a radio-frequency integrated circuit (RFIC), or any suitable combination thereof), a main memory 3004, and a static memory 3006, which are configured to communicate with each other via a bus 3008. The processor 3002 may contain microcircuits that are configurable, temporarily or permanently, by some or all of the instructions 3024 such that the processor 3002 is configurable to perform any one or more of the methodologies described herein, in whole or in part. For example, a set of one or more microcircuits of the processor 3002 may be configurable to execute one or more modules (e.g., software modules) described herein.

[00129] The machine 3000 may further include a video display 3010 (e.g., a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, a cathode ray tube (CRT), or any other display capable of displaying graphics or video). The machine 3000 may also include an alphanumeric input device 3012 (e.g., a keyboard or keypad), a cursor control device 3014 (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, an eye tracking device, or other pointing instrument), a storage unit 3016, a signal generation device 3018 (e.g., a sound card, an amplifier, a speaker, a headphone jack, or any suitable combination thereof), and a network interface device 3020.

[00130] The storage unit 3016 includes the machine-readable medium 3022 (e.g., a tangible and non-transitory machine-readable storage medium) on which are stored the instructions 3024 embodying any one or more of the methodologies or functions described herein, including, for example, any of the descriptions of FIGS. 1-29. The instructions 3024 may also reside, completely or at least partially, within the main memory 3004, within the processor 3002 (e.g., within the processor's cache memory), or both, before or during execution thereof by the machine 3000. The instructions 3024 may also reside in the static memory 3006.

[00131] Accordingly, the main memory 3004 and the processor 3002 may be considered machine-readable media 3022 (e.g., tangible and non-transitory machine- readable media). The instructions 3024 may be transmitted or received over a network 3026 via the network interface device 3020. For example, the network interface device 3020 may communicate the instructions 3024 using any one or more transfer protocols (e.g., HTTP). The machine 3000 may also represent example means for performing any of the functions described herein, including the processes described in FIGS. 1-29.

[00132] In some example embodiments, the machine 3000 may be a portable computing device, such as a smartphone or tablet computer, and have one or more additional input components (e.g., sensors or gauges) (not shown). Examples of such input components include an image input component (e.g., one or more cameras), an audio input component (e.g., a microphone), a direction input component (e.g., a compass), a location input component (e.g., a GPS receiver), an orientation component (e.g., a gyroscope), a motion detection component (e.g., one or more accelerometers), an altitude detection component (e.g., an altimeter), and a gas detection component (e.g., a gas sensor). Inputs harvested by any one or more of these input components may be accessible and available for use by any of the modules described herein.

[00133] As used herein, the term "memory" refers to a machine-readable medium 3022 able to store data temporarily or permanently and may be taken to include, but not be limited to, random-access memory (RAM), read-only memory (ROM), buffer memory, flash memory, and cache memory. While the machine-readable medium 3022 is shown in an example embodiment to be a single medium, the term "machine- readable medium" should be taken to include a single medium or multiple media (e.g., a centralized or distributed database 115, or associated caches and servers) able to store instructions 3024. The term "machine-readable medium" shall also be taken to include any medium, or combination of multiple media, that is capable of storing the instructions 3024 for execution by the machine 3000, such that the instructions 3024, when executed by one or more processors of the machine 3000 (e.g., processor 3002), cause the machine 3000 to perform any one or more of the methodologies described herein, in whole or in part. Accordingly, a "machine-readable medium" refers to a single storage apparatus or device, as well as cloud-based storage systems or storage networks that include multiple storage apparatuses or devices. The term "machine- readable medium" shall accordingly be taken to include, but not be limited to, one or more tangible (e.g., non-transitory) data repositories in the form of a solid-state memory, an optical medium, a magnetic medium, or any suitable combination thereof.

[00134] Furthermore, the machine-readable medium 3022 is non-transitory in that it does not embody a propagating signal. However, labeling the tangible machine- readable medium 3022 as "non-transitory" should not be construed to mean that the medium is incapable of movement; the medium should be considered as being transportable from one physical location to another. Additionally, since the machine- readable medium 3022 is tangible, the medium may be considered to be a machine- readable device.

[00135] Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated.

Structures and functionality presented as separate components in example

configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

[00136] Certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute software modules

(e.g., code stored or otherwise embodied on a machine-readable medium 3022 or in a transmission medium), hardware modules, or any suitable combination thereof. A

"hardware module" is a tangible (e.g., non-transitory) unit capable of performing certain operations and may be configured or arranged in a certain physical manner. In various example embodiments, one or more computer systems (e.g., a standalone computer system, a client computer system, or a server computer system) or one or more hardware modules of a computer system (e.g., a processor 3002 or a group of processors 3002) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein.

[00137] In some embodiments, a hardware module may be implemented mechanically, electronically, or any suitable combination thereof. For example, a hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations. For example, a hardware module may be a special-purpose processor, such as a field programmable gate array (FPGA) or an ASIC. A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations. For example, a hardware module may include software encompassed within a general-purpose processor 3002 or other programmable processor 3002. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[00138] Hardware modules can provide information to, and receive information from, other hardware modules. Accordingly, the described hardware modules may be regarded as being communicatively coupled. Where multiple hardware modules exist contemporaneously, communications may be achieved through signal transmission (e.g., over appropriate circuits and buses 3008) between or among two or more of the hardware modules. In embodiments in which multiple hardware modules are configured or instantiated at different times, communications between such hardware modules may be achieved, for example, through the storage and retrieval of information in memory structures to which the multiple hardware modules have access. For example, one hardware module may perform an operation and store the output of that operation in a memory device to which it is communicatively coupled. A further hardware module may then, at a later time, access the memory device to retrieve and process the stored output. Hardware modules may also initiate communications with input or output devices, and can operate on a resource (e.g., a collection of

information).

[00139] The various operations of example methods described herein may be performed, at least partially, by one or more processors 3002 that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors 3002 may constitute processor-implemented modules that operate to perform one or more operations or functions described herein. As used herein, "processor-implemented module" refers to a hardware module implemented using one or more processors 3002.

[00140] Similarly, the methods described herein may be at least partially processor-implemented, a processor 3002 being an example of hardware. For example, at least some of the operations of a method may be performed by one or more processors 3002 or processor-implemented modules. As used herein, "processor- implemented module" refers to a hardware module in which the hardware includes one or more processors 3002. Moreover, the one or more processors 3002 may also operate to support performance of the relevant operations in a "cloud computing" environment or as a "software as a service" (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines 3000 including processors 3002), with these operations being accessible via a network 3026 (e.g., the Internet) and via one or more appropriate interfaces (e.g., an API).

[00141] The performance of certain operations may be distributed among the one or more processors 3002, not only residing within a single machine 3000, but deployed across a number of machines 3000. In some example embodiments, the one or more processors 3002 or processor-implemented modules may be located in a single geographic location (e.g., within a home environment, an office environment, or a server farm). In other example embodiments, the one or more processors 3002 or processor-implemented modules may be distributed across a number of geographic locations.

[00142] Unless specifically stated otherwise, discussions herein using words such as "processing," "computing," "calculating," "determining," "presenting,"

"displaying," or the like may refer to actions or processes of a machine 3000 (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or any suitable combination thereof), registers, or other machine components that receive, store, transmit, or display information. Furthermore, unless specifically stated otherwise, the terms "a" or "an" are herein used, as is common in patent documents, to include one or more than one instance. Finally, as used herein, the conjunction "or" refers to a non-exclusive "or," unless specifically stated otherwise.

[00143] The present disclosure is illustrative and not limiting. Further

modifications will be apparent to one skilled in the art in light of this disclosure and are intended to fall within the scope of the appended claims.