Patent Description:
Heat exchangers are well known in many industries for a variety of applications. Heat exchangers that operate in high temperature environments, such as in modem aircraft engines, can have reduced service lives due to high thermal stress. Thermal stress can be caused by uneven temperature distribution within the heat exchanger or with abutting components, component stiffness and geometry discontinuity, and/or other material properties of the heat exchanger. The interface between an inlet/outlet manifold and the core of a heat exchanger can be subject to the highest thermal stress and the shortest service life.

In mobile applications, particularly for aerospace applications, it is desirable to use heat exchangers that provide a compact, low-weight, and highly-effective means of exchanging heat from a hot fluid to a cold fluid. Additive manufacturing techniques can be utilized to manufacture heat exchangers layer by layer to obtain a variety of complex geometries that may be desirable for such applications.

A heat exchanger according to the invention is provided in claim <NUM>.

A heat exchanger with interleaved manifolds and a layered core is disclosed herein. The heat exchanger includes at least two branched tubular manifolds mated to a honeycomb core. The manifolds have a fractal geometry such that there is a fractal relationship between consecutive levels of branching tubes within each manifold. That is, each consecutive level of tubes within the manifolds can be nearly the same as the previous level. The interleaved structure of the manifolds and core enables the heat exchanger to be additively manufactured as a single unit. The heat exchanger is described below with reference to <FIG>.

For purposes of clarity and ease of discussion, <FIG>, <FIG>, and <FIG> will be described together. <FIG> is a partial cut-away isometric view showing a front view of heat exchanger <NUM> with interleaved hot and cold flow layers. <FIG> is partial cut-away isometric view showing a rear view of heat exchanger <NUM>. <FIG> is a cross-sectional view of heat exchanger <NUM>. Heat exchanger <NUM> includes hot manifold <NUM> and cold manifold <NUM> fluidly connected to core <NUM>. ("Hot" and "cold" designations herein are used to refer to the relative temperature of fluid flowing through the hot and cold manifolds, respectively, but the designations can be reversed in alternative embodiments).

Hot manifold <NUM> includes hot fluid port <NUM>, hot primary fluid channel <NUM>, hot branched region <NUM>, hot secondary fluid channels <NUM>, and hot overlap region <NUM>. Transition region <NUM> forms an interface between hot manifold <NUM>, cold manifold <NUM>, and core <NUM>. Cold manifold <NUM> similarly includes cold fluid port <NUM>, cold primary fluid channel <NUM>, cold branched region <NUM>, cold secondary fluid channels <NUM>, and cold overlap region <NUM>. Core <NUM> includes hot core channels <NUM> within hot flow layers 40A-40N ("N" is used herein as an arbitrary integer) and cold core channels <NUM> within cold flow layers 44A-44N. Heat exchanger <NUM> interacts with hot fluid FH at hot manifold <NUM> and with cold fluid FC at cold manifold <NUM>.

Hot fluid port <NUM> forms an opening into the fluid system of hot manifold <NUM>. Specifically, hot fluid port <NUM> is configured as an opening into hot primary fluid channel <NUM>. Hot primary fluid channel <NUM> forms a first section of hot manifold <NUM>. Hot primary fluid channel <NUM> extends between hot fluid port <NUM> and hot branched region <NUM>. Hot branched region <NUM> forms an end of hot primary fluid channel <NUM> distal to hot fluid port <NUM>.

Hot secondary fluid channels <NUM> are fluidly connected to hot primary fluid channel <NUM> at hot branched region <NUM>. Though the examples of <FIG> and <FIG> show hot branched region <NUM> branching into four distinct layers of four hot secondary fluid channels <NUM>, it should be understood that in other examples, alternate configurations are possible, including more or fewer hot secondary fluid channels <NUM> extending from hot branched region <NUM>. Furthermore, hot secondary fluid channels <NUM> can extend radially from hot branched region <NUM> along a single plane or along multiple planes (to form a layered structure as shown in <FIG> and <FIG>).

Hot secondary fluid channels <NUM> extend between hot branched region <NUM> of hot manifold <NUM> and core <NUM>. Hot secondary fluid channels <NUM> can form a relatively straight path between hot branched region <NUM> and core <NUM> (i.e., so that hot manifold <NUM> and core <NUM> are oriented at <NUM> degrees) or the path can be curved, for example, as shown in <FIG> and <FIG> at overlap region <NUM>. Though the examples of <FIG> and <FIG> show hot secondary fluid channels <NUM> turning <NUM> degrees to interface with core <NUM>, it should be understood that in other examples, the angle between hot secondary fluid channels <NUM> and core <NUM> need not be <NUM> degrees.

As shown in <FIG> and <FIG>, cold manifold <NUM> can have a substantially similar configuration to hot manifold <NUM>. Cold fluid port <NUM> forms an opening into the fluid system of cold manifold <NUM>. Specifically, cold fluid port <NUM> is configured as an opening into cold primary fluid channel <NUM>. Cold primary fluid channel <NUM> forms a first section of cold manifold <NUM>. Cold primary fluid channel <NUM> extends between cold fluid port <NUM> and cold branched region <NUM>. Cold branched region <NUM> forms an end of cold primary fluid channel <NUM> distal to cold fluid port <NUM>.

Cold secondary fluid channels <NUM> are fluidly connected to cold primary fluid channel <NUM> at cold branched region <NUM>. Though the examples of <FIG> and <FIG> show cold branched region <NUM> branching into four distinct layers of four cold secondary fluid channels <NUM>, it should be understood that in other examples, alternate configurations are possible, including more or fewer cold secondary fluid channels <NUM> extending from cold branched region <NUM>. Furthermore, cold secondary fluid channels <NUM> can extend radially from cold branched region <NUM> along a single plane or along multiple planes (to form a layered structure as shown in <FIG> and <FIG>). As shown in the examples of <FIG> and <FIG>, hot manifold <NUM> and cold manifold <NUM> can include the same number of layers of hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM>, respectively.

Cold secondary fluid channels <NUM> extend between cold branched region <NUM> of cold manifold <NUM> and core <NUM>. Cold secondary fluid channels <NUM> can form a relatively straight path between cold branched region <NUM> and core <NUM> (i.e., so that cold manifold <NUM> and core <NUM> are oriented at <NUM> degrees) or the path can be curved, for example, as shown in <FIG> and <FIG> at overlap region <NUM>. Though the examples of <FIG> and <FIG> show cold secondary fluid channels <NUM> turning <NUM> degrees to interface with core <NUM>, such that cold manifold <NUM> is oriented at <NUM> degrees to hot manifold <NUM>, it should be understood that in other examples, the angle between cold secondary fluid channels <NUM> and core <NUM> need not be <NUM> degrees (i.e., hot manifold <NUM> and cold manifold <NUM> need not be oriented at <NUM> degrees). Furthermore, hot manifold <NUM> and cold manifold <NUM> can also be oriented along different planes with respect to each other and/or with respect to core <NUM> (rather than a coplanar orientation as shown in <FIG> and <FIG>).

As is most easily viewed in <FIG>, hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> are interleaved at hot overlap region <NUM> and cold overlap region <NUM>. Hot overlap region <NUM> and cold overlap region <NUM> can correspond to the curved portion (as described above) of hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM>, respectively. Between hot branched region <NUM> and hot overlap region <NUM>, layers of hot secondary fluid channels <NUM> are spaced apart such that a layer of cold secondary fluid channels <NUM> of cold manifold <NUM> can be disposed between two consecutive layers of hot secondary fluid channels <NUM>. Consecutive layers of cold secondary fluid channels <NUM> are similarly spaced apart. Thus, at hot overlap region <NUM> and cold overlap region <NUM>, layers of hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> form a stacked structure of alternating layers.

The stacked structure of alternating layers of hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> interfaces with core <NUM> at transition region <NUM>. Transition region <NUM> forms an end of both hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> that is distal to hot branched region <NUM> and cold branched region <NUM>. In alternative embodiments, hot manifold <NUM> and/or cold manifold <NUM> can be configured to include additional levels of branching and intervening fluid channels fluidly connected to hot secondary fluid channels <NUM> and/or cold secondary fluid channels <NUM> between hot branched region <NUM>, cold branched region <NUM>, and transition region <NUM>. In some examples, hot manifold <NUM> and cold manifold <NUM> can have a fractal geometry defining the branching relationship between sequential levels of fluid channels.

Hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> are tubular in structure to facilitate fluid flow. At transition region <NUM>, hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> transition from having a circular cross-sectional area to a hexagonal cross-sectional area. Further, each hot secondary fluid channel <NUM> is continuous with a corresponding hot core channel <NUM> with a hexagonal cross-section, and each cold secondary fluid channel <NUM> is continuous with a corresponding cold core channel <NUM> with a hexagonal cross-section. Thus, hot secondary fluid channels <NUM> and cold secondary fluid channels <NUM> and corresponding hot core channels <NUM> and cold core channels <NUM> form a continuous fluid network.

Hot core channels <NUM> form hot flow layers 40A-40N of core <NUM>. Each hot flow layer 40A-40N can correspond to a separate layer of hot secondary fluid channels <NUM> of hot manifold <NUM>. Similarly, cold core channels <NUM> form cold flow layers 44A-44N of core <NUM>. Each cold flow layer 44A-44N can correspond to a separate layer of cold secondary fluid channels <NUM> of cold manifold <NUM>. Thus, in the example of <FIG>, core <NUM> is shown to include four hot flow layers 40A-40N and four cold flow layers 44A-44N. Specifically, as is best viewed in <FIG>, a first layer of hot secondary fluid channels <NUM> can correspond to a first one of hot flow layers 40A-40N (e.g., hot flow layer 40A), and a first layer of cold secondary fluid channels <NUM> (with respect to the same arbitrarily chosen side of heat exchanger <NUM>) can correspond to a first one of cold flow layers 44A-44N (e.g., cold flow layer 44A).

Hot flow layers 40A-40N are spaced apart such that a single cold flow layer 44A-44N is disposed between two consecutive hot flow layers 40A-40N. Consecutive cold flow layers 44A-44N are similarly spaced apart. Thus, throughout core <NUM>, hot flow layers 40A-40N and cold flow layers 44A-44N form a stacked structure of alternating layers arranged along parallel planes corresponding to each of hot flow layers 40A-40N and cold flow layers 44A-44N. For example, as shown in <FIG>, <FIG>, and <FIG>, cold flow layer 44A is disposed between hot flow layer 40A and hot flow layer 40B. Though the example of <FIG> shows hot flow layers 40A-40N and cold flow layers 44A-44N are arranged such that all layers (e.g., each of hot flow layers 40A-40N and cold flow layers 44A-44N) are parallel and all individual hot core channels <NUM> and cold core channels <NUM> follow a straight path within core <NUM>, it should be understood that alternative core configurations are possible, including three-dimensional curved regions or separations within individual hot flow layers 40A-40N and/or cold flow layers 44A-44N.

In the examples of <FIG>, <FIG>, and <FIG>, core <NUM> is shown with a three-dimensional honeycomb geometry, but it should be understood that alternative embodiments can include other core types and/or geometries, particularly other layered geometries. Additionally, though the examples of <FIG> and <FIG> illustrate heat exchanger <NUM> as including a single hot manifold <NUM> and a single cold manifold <NUM> connected to core <NUM>, it should be understood that in other examples, heat exchanger <NUM> can include more than two manifold structures interfacing with core <NUM>. Multiple manifold structures can be arranged in a substantially similar manner to hot manifold <NUM> and cold manifold <NUM> and can form additional layers of an interface with core <NUM>.

The configuration and interleaved honeycomb geometry of core <NUM> is shown in greater detail in <FIG> is a cross-sectional view of heat exchanger <NUM> taken at plane A-A of <FIG>. Each of hot core channels <NUM> and cold core channels <NUM> can have a regular hexagonal cross-sectional area (i.e., all walls and all interior angles (not labelled in <FIG>) of each hot core channel <NUM> and cold core channel <NUM> can be congruent) defined by height T between opposite corners. Additionally,.

<FIG> shows core <NUM> with a uniform, interlocking, hexagonal cross-sectional geometry.

Adjacent hot core channels <NUM> are aligned such that a single wall forming a side of the cross-sectional hexagon is shared between adjacent hot core channels <NUM>. Multiple adjacent hot core channels <NUM> are aligned in this way to form one of hot flow layers 40A-40N. Similarly, adjacent cold core channels <NUM> are aligned such that a single wall forming a side of the cross-sectional hexagon is shared between adjacent cold core channels <NUM>. Multiple adjacent cold core channels <NUM> are aligned in this way to form one of cold flow layers 44A-44N.

Hot flow layers 40A-40N are arranged alternately with cold flow layers 44A-44N. As shown in <FIG>, an adjacent pair of hot flow layers 40A-40N and cold flow layers 44A-44N can be offset by half the width of one channel (e.g., hot core channels <NUM>, cold core channels <NUM>), such that the cross-sectional hexagons of the adjacent pair of hot flow layers 40A-40N and cold flow layers 44A-44N are interlocking. Hot-cold interfaces N define shared walls between adjacent ones of hot flow layers 40A-40N and cold flow layers 44A-44N (e.g., between hot flow layer 40A and cold flow layer 44A in <FIG>). When viewed in cross-section, hot-cold interface N can form a zigzag line with points corresponding to the interlocking corners of hot core channels <NUM> and cold core channels <NUM>. Because adjacent hot flow layers 40A-40N and cold flow layers 44A-44N are interlocking along hot-cold interface N, the distance between adjacent hot flow layers 40A-40N and cold flow layers 44A-44N ranges from the length of one side of an individual channel (e.g., hot core channels <NUM>, cold core channels <NUM>) to height T.

With continued reference to <FIG>, <FIG>, and <FIG>, heat exchanger <NUM> is configured to permit the transfer of heat between hot fluid FH and cold fluid Fc. For example, a transfer of heat can be associated with the use of hot fluid FH and/or cold fluid FC for cooling and/or lubrication of components in a larger system, such as a gas turbine engine or aerospace system. Hot fluid FH and cold fluid FC can be any type of fluid, including air, water, lubricant, fuel, or another fluid. Heat exchanger <NUM> is described herein as providing heat transfer from hot fluid FH to cold fluid FC; therefore, hot fluid FH is at a greater temperature than cold fluid FC at the point where hot fluid FH enters heat exchanger <NUM>. However, other configurations of heat exchanger <NUM> can include cold fluid FC at a greater temperature than hot fluid FC (and, thus, the "hot" and "cold" designations used herein would be reversed).

In the example of <FIG> and <FIG>, heat exchanger <NUM> is shown receiving hot fluid FH at hot fluid port <NUM> and discharging cold fluid FC at cold fluid port <NUM> (i.e., a counter-flow arrangement). In other examples, the direction of flow of hot fluid FH and/or cold fluid FC can be reversed such that hot fluid FH exits heat exchanger <NUM> at hot fluid port <NUM> and cold fluid FC is received by heat exchanger <NUM> at cold fluid port <NUM>. In yet other examples, heat exchanger <NUM> can be configured to interact with additional fluids, including along axes parallel or perpendicular to heat exchanger <NUM> (i.e., an additional counter-flow or a cross-flow arrangement, respectively, not shown in <FIG>).

Hot fluid port <NUM> of hot manifold <NUM> is configured to receive or discharge hot fluid FH. Hot fluid FH entering hot manifold <NUM> at hot fluid port <NUM> is channeled through hot primary fluid channel <NUM> to hot branched region <NUM>. At hot branched region <NUM>, hot fluid FH flows into hot secondary fluid channels <NUM>. From hot branched region <NUM>, hot fluid FH flows within hot secondary fluid channels <NUM> through hot overlap region <NUM> to the interface with core <NUM> at transition region <NUM>. In the examples of <FIG> and <FIG>, hot fluid FH flows directly from hot secondary fluid channels <NUM> into hot core channels <NUM> of hot flow layers 40A-40N.

Cold fluid port <NUM> of cold manifold <NUM> is configured to receive or discharge cold fluid FC. Cold fluid FC entering cold manifold <NUM> at cold fluid port <NUM> is channeled through cold primary fluid channel <NUM> to cold branched region <NUM>. At cold branched region <NUM>, cold fluid FC flows into cold secondary fluid channels <NUM>. From cold branched region <NUM>, cold fluid FC flows within cold secondary fluid channels <NUM> through cold overlap region <NUM> to the interface with core <NUM> at transition region <NUM>. In the examples of <FIG> and <FIG>, cold fluid FC flows directly from cold secondary fluid channels <NUM> into cold core channels <NUM> of cold flow layers 44A-44N. Heat transfer between hot fluid FH and cold fluid FC can occur largely along hot-cold interfaces N of core <NUM>.

In general, the interleaved structure of heat exchanger <NUM> retains the benefits of fractal geometry compared to traditional heat exchanger header configurations. Traditional heat exchanger headers, such as those with box-shaped manifolds, can have increased stress concentration at the interface between the manifold and the core, particularly at corners of the manifold where there is geometry discontinuity. The branching pattern of fractal heat exchanger manifolds, wherein each fluid channel is individually and directly connected to a passage in the core as shown in <FIG>, <FIG>, and <FIG>, can reduce this geometry discontinuity. Furthermore, each fluid channel in a fractal heat exchanger manifold (e.g., hot manifold <NUM> and cold manifold <NUM>) behaves like a slim beam with low stiffness in transverse directions and reduced stiffness in horizontal directions due to the curved shape at each branched region. Thus, hot manifold <NUM> and cold manifold <NUM> have increased compliance (i.e., reduced stiffness) and experience less thermal stress compared to traditional heat exchanger header configurations.

Furthermore, the honeycomb geometry of core <NUM> with interleaved hot flow layers 40A-40N and cold flow layers 44A-44N has large hot-to-cold interaction surfaces (e.g., along hot-cold interfaces N) for a given volume. That is, there is ample surface area for heat transfer between hot fluid FH and cold fluid FC to occur. Thus, in applications wherein volume is a limiting factor, a heat exchanger with a honeycomb core as described herein can have increased efficiency relative to traditional heat exchanger configurations.

Heat exchanger <NUM> (and/or any component parts, including hot manifold <NUM>, cold manifold <NUM>, and core <NUM>) can be formed partially or entirely by additive manufacturing. For metal components (e.g., nickel-based superalloys, aluminum, titanium, etc.) exemplary additive manufacturing processes include powder bed fusion techniques such as direct metal laser sintering (DMLS), laser net shape manufacturing (LNSM), electron beam manufacturing (EBM), to name a few, non-limiting examples. For polymer or plastic components, stereolithography (SLA) can be used. Additive manufacturing is particularly useful in obtaining unique geometries and for reducing the need for welds or other attachments (e.g., between a header and core). However, it should be understood that other suitable manufacturing processes can be used.

During an additive manufacturing process, heat exchanger <NUM> (and/or any component parts, including hot manifold <NUM>, cold manifold <NUM>, and core <NUM>) can be formed layer by layer to achieve varied tubular dimensions (e.g., cross-sectional area, wall thicknesses, curvature, etc.). Each additively manufactured layer creates a new horizontal build plane to which a subsequent layer of heat exchanger <NUM> is fused. That is, the build plane for the additive manufacturing process remains horizontal but shifts vertically by defined increments (e.g., one micrometer, one hundredth of a millimeter, one tenth of a millimeter, a millimeter, or other distances) as manufacturing proceeds. The examples of <FIG> and <FIG> show heat exchanger <NUM> already fully manufactured.

The interleaved geometry of heat exchanger <NUM> enables at least two fractal manifolds (e.g., hot manifold <NUM> and cold manifold <NUM>) to be directly and individually connected to a honeycomb core (e.g., core <NUM>). As such, heat exchanger <NUM> combines the benefits of both fractal and honeycomb geometries (as described above). The interleaved geometry also enables heat exchanger <NUM> to be additively manufactured as a single, monolithic unit. Additively manufacturing heat exchanger <NUM> as a single unit is particularly useful in that this process can reduce the need for welds, other attachments, or other manufacturing steps to combine components of heat exchanger <NUM> which would otherwise have been manufactured separately.

<FIG> is an isometric view of heat exchanger <NUM> including inlet and outlet manifolds and hot and cold flow layers. Heat exchanger <NUM> is substantially similar to heat exchanger <NUM>, and additionally includes core <NUM> disposed between fluidly connected hot inlet manifold <NUM>i and hot outlet manifold <NUM>o and between fluidly connected cold inlet manifold <NUM>i and cold outlet manifold <NUM>o.

In serial fluid communication with each of hot fluid inlet <NUM>i and hot fluid outlet <NUM>o (denoted in <FIG> with the applicable "i" or "o" subscript, but generally referred to herein solely by reference number) are hot primary fluid channel <NUM>, hot branched region <NUM>, hot secondary fluid channels <NUM>, and hot overlap region <NUM>. First transition region <NUM> forms an interface between hot inlet manifold <NUM>i, cold outlet manifold <NUM>o, and core <NUM>. In serial fluid communication with each of cold fluid inlet <NUM>i and cold fluid outlet <NUM>o (similarly denoted in <FIG> with the applicable "i" or "o" subscript, but generally referred to herein solely by reference number) are cold primary fluid channel <NUM>, cold branched region <NUM>, cold secondary fluid channels <NUM>, and cold overlap region <NUM>. Second transition region <NUM> forms an interface between hot outlet manifold <NUM>o, cold inlet manifold <NUM>i, and core <NUM>.

Hot core channels <NUM> of core <NUM> extend within hot flow layers 140A-140N between fluidly connected, corresponding hot secondary fluid channels <NUM>. Cold core channels <NUM> of core <NUM> extend within cold flow layers 144A-144N between fluidly connected, corresponding cold secondary fluid channels <NUM>. Generally, the ratio within heat exchanger <NUM> between inlet hot secondary fluid channels <NUM>i, hot core channels <NUM>, and outlet hot secondary fluid channels <NUM>o can be <NUM>:<NUM>:<NUM>, such that an individual inlet hot secondary fluid channel <NUM>i is connected to an individual hot core channel <NUM>, and the individual hot core channel <NUM> is connected to an individual outlet hot secondary fluid channel <NUM>o. The ratio between inlet cold secondary fluid channels <NUM>i, cold core channels <NUM>, and outlet cold secondary fluid channels <NUM>o can also be <NUM>:<NUM>:<NUM>, such that an individual inlet cold secondary fluid channel <NUM>i is connected to an individual cold core channel <NUM>, and the individual cold core channel <NUM> is connected to an individual outlet cold secondary fluid channel <NUM>o.

Thus, each of hot inlet manifold <NUM>i and hot outlet manifold <NUM>o can include interleaved layers of hot secondary fluid channels <NUM> directly and individually connected to interleaved hot flow layers 140A-140N of core <NUM>, as described above with reference to <FIG>, <FIG>, and <FIG>. Similarly, each of cold inlet manifold <NUM>i and cold outlet manifold <NUM>o can include interleaved layers of cold secondary fluid channels <NUM> directly and individually connected to interleaved cold flow layers 144A-144N of core <NUM>, as described above with reference to <FIG>, <FIG>, and <FIG>.

In the example of <FIG>, hot inlet manifold <NUM>i is oriented at <NUM> degrees to cold outlet manifold <NUM>o on the same side of core <NUM>. On the other side of core <NUM>, hot outlet manifold <NUM>o is oriented at <NUM> degrees to cold inlet manifold <NUM>i. Hot inlet manifold <NUM>i can be coplanar with and antiparallel to hot outlet manifold <NUM>o, such that the entire path from hot inlet manifold <NUM>i, through core <NUM>, and out hot outlet manifold <NUM>o forms an "S" shape. Cold inlet manifold <NUM>i can also be coplanar with and antiparallel to cold outlet manifold <NUM>o, such that the path from cold inlet manifold <NUM>i, through core <NUM>, and out cold outlet manifold <NUM>o forms a mirrored (i.e., "backwards") "S" shape.

In other words, hot outlet manifold <NUM>o is essentially transposed and mirrored across an axis through core <NUM> (not shown in <FIG>) with respect to hot inlet manifold <NUM>i. Similarly, cold outlet manifold <NUM>o is essentially transposed and mirrored across the same axis through core <NUM> with respect to cold inlet manifold <NUM>i. However, because the relative configuration of the manifolds (e.g., hot inlet manifold <NUM>i, hot outlet manifold <NUM>o, cold inlet manifold <NUM>i, cold outlet manifold <NUM>o) is dependent, in part, on the three-dimensional geometry of core <NUM>, it should be understood that in alternative embodiments, corresponding inlet and outlet manifolds can be oriented at different angles or even along different planes with respect to each other and/or with respect to core <NUM>.

In a manner that is substantially similar to that described above with reference to <FIG>, <FIG>, and <FIG>, heat exchanger <NUM> is configured to permit the transfer of heat between hot fluid FH and cold fluid FC. In the example of <FIG>, hot fluid FH enters heat exchanger <NUM> at hot fluid inlet <NUM>i. Hot fluid FH passes through the branching tubular network (hot primary fluid channel <NUM>i, hot branched region <NUM>i, hot secondary fluid channels <NUM>i, and hot overlap region <NUM>i) of hot inlet manifold <NUM>i, through core <NUM> within hot core channels <NUM>, to the branching tubular network (hot overlap region <NUM>o, hot secondary fluid channels <NUM>o, hot branched region <NUM>o, and hot primary fluid channel <NUM>o) of hot outlet manifold <NUM>o, and exits heat exchanger <NUM> at hot fluid outlet <NUM>o. Heat exchanger <NUM> is configured such that hot fluid FH encounters the same branching tubular network within hot outlet manifold <NUM>o as in hot inlet manifold <NUM>i in reverse order.

Additionally, in the example of <FIG>, cold fluid FC enters heat exchanger <NUM> at cold fluid inlet <NUM>i. Cold fluid FC passes through the branching tubular network (cold primary fluid channel <NUM>i, cold branched region <NUM>i, cold secondary fluid channels <NUM>i, and cold overlap region <NUM>i) of cold inlet manifold <NUM>i, through core <NUM> within cold core channels <NUM>, to the branching tubular network (cold overlap region <NUM>o, cold secondary fluid channels <NUM>o, cold branched region <NUM>o, and cold primary fluid channel <NUM>o) of cold outlet manifold <NUM>o, and exits heat exchanger <NUM> at cold fluid outlet <NUM>o. Heat exchanger <NUM> is configured such that cold fluid FC encounters the same branching tubular network within cold outlet manifold <NUM>o as in cold inlet manifold <NUM>i in reverse order. Thus, heat exchanger <NUM> can have a counter-flow arrangement with hot fluid FH and cold fluid FC flowing through heat exchanger <NUM> in opposite directions.

In another example, the direction of flow of hot fluid FH and/or cold fluid FC can be reversed such that hot fluid FH enters heat exchanger <NUM> at hot fluid outlet <NUM>o and exits at hot fluid inlet <NUM>i and/or cold fluid FC enters heat exchanger <NUM> at cold fluid outlet <NUM>o and exits at cold fluid inlet <NUM>i, respectively. In yet other examples, heat exchanger <NUM> can be configured to interact with additional fluids, including along axes parallel or perpendicular to heat exchanger <NUM> (i.e., an additional counter-flow or a cross-flow arrangement, respectively, not shown in <FIG>).

Thus, heat exchanger <NUM> is configured to facilitate the transfer of heat between hot fluid FH and cold fluid FC at core <NUM>. Hot fluid FH, exiting heat exchanger <NUM> at hot fluid outlet <NUM>o, and/or cold fluid FC, exiting heat exchanger <NUM> at cold fluid outlet <NUM>o, can have final temperatures (e.g., after heat transfer has occurred and equilibrium is reached) that are suitable for cooling and/or lubrication of components in a larger system, such as a gas turbine engine or aerospace system.

Claim 1:
A heat exchanger comprising:
a core;
a first manifold (<NUM>) comprising:
a primary fluid channel (<NUM>) extending between a fluid port and a first branched region;
a plurality of secondary fluid channels (<NUM>) fluidly connected to the primary fluid channel at the first branched region; and
a first overlap region (<NUM>) of the plurality of secondary fluid channels downstream of the first branched region and connected to the core at a first transition region; and
a second manifold (<NUM>) comprising:
a primary fluid channel (<NUM>) extending between a fluid port and a first branched region;
a plurality of secondary fluid channels (<NUM>) fluidly connected to the primary fluid channel at the first branched region; and
a first overlap region (<NUM>) of the plurality of secondary fluid channels downstream of the first branched region and connected to the core at a first transition region;
wherein each of the first and second manifolds has a fractal geometry;
wherein each of the plurality of secondary fluid channels of the first and second manifolds is tubular between the first branched region and the first transition region;
wherein the plurality of secondary fluid channels (<NUM>, <NUM>) of the first and second manifolds are interleaved at the first overlap region such that a first layer of secondary fluid channels of the first manifold forms a first flow layer within the core, a first layer of secondary fluid channels of the second manifold forms a second flow layer within the core, and the first flow layer is adjacent and parallel to the second flow layer;
wherein each of the plurality of secondary fluid channels of at least one of the first and second manifolds forms a curved path at the respective first overlap region;
wherein a cross-sectional area of each of the plurality of secondary fluid channels of the first and second manifolds changes at the first transition region such that the first transition region defines a perpendicular plane through the plurality of secondary fluid channels at which the cross-sectional area of each of the plurality of secondary fluid channels is hexagonal; and wherein the core is a three-dimensional honeycomb structure.