Patent Description:
Heat exchangers are used in a variety of systems, for example, in engine and environmental control systems of aircraft. These systems tend to require continual improvement in heat transfer performance, reductions in pressure loss, and reductions in size and weight. Heat exchangers typically include a plate/fin construction in the core of the heat exchanger.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for systems and methods that allow for improved heat exchangers. The present invention provides a solution for these problems. <CIT> disclose a counter-flow heat exchanger according to the preamble of claim <NUM> and relates to a 3D printed heat exchanger.

The objects of the present invention are solved by the features of the independent apparatus claim <NUM>.

The objects of another aspect of the invention are solved by the features of the independent method claim <NUM>.

These and other features of the systems and methods of the subject invention will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

So that those skilled in the art will readily understand how to make and use the devices and methods preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:.

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a perspective view of an exemplary embodiment of a heat exchanger core in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Other embodiments of heat exchanger core in accordance with the disclosure, or aspects thereof, are provided in <FIG>, as will be described. Embodiments of heat exchanger <NUM> and <NUM> provide a heat exchanger core that results in increased performance, and reduced size and weight as compared with traditional heat exchangers.

As shown in <FIG> and <FIG>, a counter-flow heat exchanger core <NUM> includes a second wall <NUM> defining a longitudinal axis A. The counter-flow heat exchanger core <NUM> is configured and adapted to have oil flow and air flow separated into a counter-flow arrangement. The heat exchanger core <NUM> includes a first wall <NUM> radially outward and spaced apart from the second wall <NUM>. The first flow path <NUM>, e.g. the air flow path, includes a primary flow inlet <NUM> and a primary flow outlet <NUM> downstream from the primary flow inlet <NUM>. The air flows through primary flow inlet <NUM> and then through channels <NUM> to outlet <NUM>. Channels <NUM> totally fill the air side of the heat exchanger core <NUM>, meaning that they extend the entire length in the longitudinal direction of core <NUM> from primary flow inlet <NUM> to primary flow outlet <NUM> such that there are no header sections within core <NUM>. The arrows <NUM> schematically show the flow direction of the first flow path <NUM>. The heat exchanger core <NUM> includes a plurality of circumferentially spaced apart at least partially hollow vanes <NUM> extending in a radially inward direction from the first wall <NUM>. Each of the hollow vanes <NUM> includes a first vane wall <NUM> and a second vane wall <NUM>. Vanes <NUM> have a wavy cross-sectional profile as they extend radially from second wall <NUM> to first wall <NUM>, as shown in <FIG>. Vanes <NUM> stop at the center C of the first wall. Hollow portions 112a of vanes <NUM> stop at the second wall <NUM>. From second wall <NUM> inwards toward center C, the vanes <NUM> have solid portions 112b. The solid portions 112b of vanes <NUM> provide increased heat transfer area, similar to fins <NUM>, described below. Those skilled in the art will readily appreciate that in some embodiments second wall <NUM> is simply formed by the hollow portions of the adjacent circumferentially spaced apart vanes <NUM> abutting one another, or spaced apart vanes <NUM> may not abut one another, but do join together at a solid annulus of material.

As shown in <FIG>, the heat exchanger core <NUM> includes a plurality of non-linear fins <NUM>, e.g., wavy fins, extending between two of the hollow vanes <NUM>. The wavy air fins <NUM> provide increased heat transfer area, thereby improving the thermal performance of the entire heat exchanger core <NUM>. The longitudinal component of each wavy air fin <NUM> extends in a substantially circumferential direction. The wavy circumferentially extending fins <NUM> have negligible influence on pressure loss, making them more desirable. Each of the plurality of non-linear fins <NUM> are equally spaced apart from adjacent fins <NUM> in a radial direction. The wavy air fins <NUM> will reduce thermal stresses on core <NUM> and its components when thermal expansion scenarios occur by easing expansion. For example, as the heat exchanger core <NUM> heats up vanes <NUM>, second wall <NUM>, and/or first wall <NUM> may expand. The wavy fins are more flexible, thereby providing easier expansion during these scenarios.

With reference now to <FIG>, the heat exchanger core <NUM> includes a housing wall <NUM> radially outward from the first wall <NUM>. The housing wall <NUM> defines a second flow path inlet <NUM> and a second flow path outlet <NUM>. The second flow path outlet <NUM> is downstream from the second flow path inlet <NUM>. The heat exchanger core <NUM> includes a second flow path <NUM> defined between the second flow path inlet <NUM> and the second flow path outlet <NUM>. Oil enters to the heat exchanger by inlet <NUM>. Each vane <NUM> defines an inlet <NUM>, e.g. an oil inlet, an outlet <NUM>, e.g. an oil outlet, and a flow channel <NUM> therebetween. Flow channel <NUM> defines an axial component of second flow path <NUM> along longitudinal axis A opposite to the flow direction of the first flow path <NUM>. The second flow path <NUM> flows within the hollow vanes <NUM> from oil inlet <NUM> to oil outlet <NUM> between the first vane wall <NUM> and second vane wall <NUM> of each of the hollow vanes <NUM>. The general flow direction of the second flow path <NUM> is schematically shown by arrows <NUM>. The channels <NUM> of the first flow path <NUM> are concentrically arranged between the outer surfaces of adjacent vanes <NUM> and wavy air fins <NUM>.

As shown in <FIG> and <FIG>, a fluid distributor inlet annulus <NUM> is defined between the first wall <NUM> and the housing wall <NUM>. The fluid distributor inlet annulus <NUM> is in fluid communication with the second flow path <NUM> of each of the hollow vanes <NUM>. The heat exchanger core <NUM> includes a distribution tank <NUM> on one side of the inlet annulus <NUM> downstream from the inlet <NUM>. Once oil enters at second flow path inlet <NUM>, the oil fills the distribution tank <NUM> and then goes through the oil channel inlets <NUM> of each vane <NUM> into each flow channel <NUM>.

With continued reference to <FIG> and <FIG>, a fluid distributor outlet <NUM> is defined in the first wall <NUM> and the housing wall <NUM> downstream from the fluid distributor inlet annulus <NUM> and the circumferentially spaced apart hollow vane <NUM>. The second flow path outlet <NUM> is downstream from the second flow path inlet <NUM> and the fluid distributor outlet annulus <NUM>. The heat exchanger core <NUM> includes a collecting tank <NUM> on one side of the fluid distributor outlet annulus <NUM> upstream from the second flow path outlet <NUM>. Oil goes through the flow channels <NUM> and out the respective outlets <NUM> of each vane <NUM> and then accumulates via fluid distributor outlet annulus <NUM> in the collecting tank <NUM> and then out the second flow path outlet <NUM>. The second flow path inlet <NUM> and the second flow path outlet <NUM> are spaced apart from one another along the longitudinal axis A. The second flow path inlet <NUM> and a second flow path outlet <NUM> are offset from one another by <NUM> degrees.

As shown in <FIG>, another embodiment according to the invention of the non-linear fins <NUM> is shown. In the embodiment of <FIG>, non-linear fins <NUM> more proximate to the center C are spaced farther apart from one another than the non-linear fins <NUM> more proximate to the first wall <NUM>. This is different from the constant spacing between fins <NUM> of <FIG>. The spacing in <FIG> is to keep the hydraulic diameter (ln) between the non-linear fins <NUM> constant, which makes the actual distance between fins <NUM>, in the radial direction, vary. In some embodiments, the hydraulic diameter (ln+<NUM>) between two of the fins, 220b and 220c, is based on the hydraulic diameter (ln) between the previous two fins, 220a and 220b. For example, the hydraulic diameter between fins 220b and 220c can be calculated using the following equation: ln+<NUM>=ln x <NUM>, where ln is the hydraulic diameter between the previous two fins, 220a and 220b. Those skilled in the art will readily appreciate that the equation above is an exemplary relationship and may be different depending on the circumstances, e.g., depending on material stiffness or other fluid parameters. The non-linear fins <NUM> are variably spaced apart in a radial direction from center C to the first wall <NUM>. This generally results in the non-linear fins <NUM> being further apart from one another when they are nearer to the center C and longitudinal axis A and closer to one another when they are closer to first wall <NUM>.

By utilizing a counter-flow configuration, heat exchanger core <NUM> provides for reduced size and increased performance by better balancing the hot and cold fluids running through core <NUM>, e.g. through first and second flow paths <NUM> and <NUM>, respectively. Heat exchanger <NUM> also increases the heat exchanger effectiveness for a given overall heat transfer area. The counter-flow configuration enables high temperature and high pressure operation by reducing the temperature differential across the heat exchanger planform since the cold side outlet and hot side inlet are aligned with one another.

It is contemplated that a method of manufacturing a counter-flow heat exchanger core, e.g. heat exchanger core <NUM>, includes forming heat exchanger core <NUM> using additive manufacturing such as, selective laser melting (SLM), for example. It is contemplated that powder bed fusion processes can be used (e.g. direct metal laser sintering (DMLS), electron beam melting, selective heat sintering, or the like), or other categories of additive manufacturing can also be used. It is contemplated that the heat exchanger core can be manufactured in the flow direction, e.g. along longitudinal axis A to avoid horizontal surfaces. Heat exchanger core <NUM> can be manufactured as a single piece, e.g. without any brazing or weld joints.

As shown in <FIG>, another embodiment of a counter-flow heat exchanger <NUM> includes a heat exchanger core <NUM> that defines a longitudinal axis X. Heat exchanger core <NUM> includes a primary flow inlet <NUM>, a primary flow outlet <NUM> and a middle portion <NUM> therebetween. The primary flow direction is indicated schematically by the arrow <NUM>. Heat exchanger core <NUM> is circular cylinder that includes conical tapering portions at its inlet and outlet, <NUM> and <NUM>, respectively. A diameter of heat exchanger core <NUM> at primary flow inlet <NUM> is smaller than a diameter of the heat exchanger core <NUM> in middle portion <NUM>. It is also contemplated that the diameter of core <NUM> at inlet <NUM> and in middle portion <NUM> can be the same, e.g. core <NUM> can have a constant diameter. Heat exchanger core <NUM> has circular cross-sections along its length, e.g. those taken perpendicular to the flow direction and longitudinal axis X. It is contemplated that heat exchanger core <NUM> can have a variety of other suitable shapes, for example, it can be an oval cylinder, an elliptical cylinder, a rectangular cylinder, or a square cylinder. In accordance with some embodiments, additional elliptically shaped walls, similar to additional walls <NUM> can be used inside a rectangular cylinder core. The heat exchanger core is substantially linear and defines a longitudinal axis between the primary flow inlet and the primary flow outlet. A radial center of the second wall is aligned with the longitudinal axis.

As shown in <FIG>, a cross-section of heat exchanger core <NUM> at primary flow inlet <NUM> is shown. At primary flow inlet <NUM>, heat exchanger core <NUM> includes an inner wall <NUM>, e.g. a second wall, and an outer wall <NUM>, e.g. a first wall, radially outward and spaced apart from inner wall <NUM>. A first flow path <NUM> is defined within inner wall <NUM> and outer wall <NUM> and a second flow path <NUM> is defined between inner wall <NUM> and outer wall <NUM>. Inner and outer walls, <NUM> and <NUM>, respectively, define an annulus <NUM> that includes second flow path <NUM>. Inner and outer walls <NUM> and <NUM>, respectively, are cylindrical and concentric at primary flow inlet <NUM> of heat exchanger core <NUM>. Inner and outer walls, <NUM> and <NUM>, respectively, are concentric at primary flow outlet of the heat exchanger core.

As shown in <FIG>, as inner wall <NUM> extends away from primary flow inlet <NUM> it becomes corrugated and defines a first set of channels <NUM> extending axially from primary flow inlet <NUM> to middle portion <NUM> of heat exchanger core <NUM> diverging away from a radial center A of heat exchanger core <NUM>. Inner wall <NUM> and outer wall <NUM> define a second set of channels <NUM>, e.g. channels defined between first and second vane walls, extending axially from primary flow inlet <NUM> to middle portion <NUM> of heat exchanger core <NUM> converging toward radial center A of heat exchanger core <NUM>. Respective channels <NUM> and <NUM> of the first and second sets of channels <NUM> and <NUM>, respectively, alternate circumferentially with one another to provide additional surface area for heat transfer. In accordance with the embodiment of <FIG>, two channels <NUM> from first set of channels <NUM> alternate with one channel <NUM> from second set of channels <NUM>. First and second flow paths <NUM> and <NUM>, respectively, include vanes <NUM> to assist with flow distribution with only minimal pressure drop.

With reference now to <FIG>, as inner wall <NUM> extends further axially away from flow inlet <NUM> toward and into middle portion <NUM>, channels <NUM> of the first set of channels <NUM> split into multiple sub-channels <NUM> to maintain a width smaller than a maximum threshold. At least two channels <NUM> of the second set of channels <NUM> unite into a single joined channel <NUM> to maintain a width greater than a minimum threshold.

As shown in <FIG>, additional cylindrical walls <NUM>, e.g. fins, are disposed radially inward from outer wall <NUM> and are concentric with heat exchanger core <NUM>. Additional cylindrical walls <NUM> are radially spaced apart from one another and are in fluid communication with first and second flow paths <NUM> and <NUM>, respectively. Additional cylindrical walls <NUM> are circular cylindrical walls. Additional cylindrical walls <NUM> are disposed in middle portion <NUM> of the heat exchanger core <NUM>. It is also contemplated that additional cylindrical walls like cylindrical walls <NUM> could be used in other portions of heat exchanger core <NUM>.

As shown in <FIG>, in accordance with an embodiment of core <NUM>, annular ring sections <NUM> are defined between two adjacent additional walls <NUM> are circumferentially offset with respect to an adjacent annular ring so that a checker-board pattern is formed, e.g. alternating first and second flow paths <NUM> and <NUM>, respectively, in a radial direction as well as in a circumferential direction. The cross-section of <FIG> is taken at a similar location as the cross-section of <FIG>. Each annular ring section <NUM> includes a portion <NUM>' of one of channels <NUM> from first set of channels <NUM> and a portion <NUM>' of one of channels <NUM> from second set of channels <NUM>. Portion <NUM>' from first set of channels <NUM> in a first annular ring section 332a is offset radially and circumferentially from portion <NUM>' from first set of channels <NUM> in a second annular ring 332b section. Second annular ring section 332b is adjacent to first annular ring section 332a. Portion <NUM>' from the second set of channels <NUM> in first annular ring section 332a is offset radially and circumferentially from portion <NUM>' from second set of channels <NUM> in second annular ring section 332b.

With reference now to <FIG>, at outlet <NUM> of the heat exchanger core <NUM> inner and outer walls <NUM>, and <NUM>, respectively, are similar to how they were arranged at inlet <NUM>, shown in <FIG>, e.g. at a cross-section taken perpendicular to longitudinal axis X at outlet <NUM> inner and outer walls <NUM>, and <NUM>, respectively, would be concentric circles. To transition back to concentric circles, from middle portion <NUM> of the heat exchanger core <NUM> to primary flow outlet <NUM>, the first set of channels <NUM> extends axially away from middle portion <NUM> to the primary flow outlet <NUM> converging back toward radial center A of heat exchanger core <NUM> and second set of channels <NUM> extends axially away from middle portion <NUM> to primary flow outlet <NUM> diverging away from radial center A of the heat exchanger core. By utilizing a counter-flow configuration, heat exchanger <NUM> provides for reduced size and increased performance by better balancing the hot and cold fluids running through core <NUM>, e.g. through first and second flow paths <NUM> and <NUM>, respectively. Heat exchanger <NUM> also increases the heat exchanger effectiveness for a given overall heat transfer area. The counter-flow configuration enables high temperature and high pressure operation by reducing the temperature differential across the heat exchanger planform since the cold side outlet and hot side inlet are aligned with one another. By gradually transitioning from the inlet <NUM>, as shown in <FIG>, to the core <NUM>, as shown in <FIG>, pressure drops can be reduced and there is not a large discontinuity in stiffness or thermal response as in traditional headering.

It is contemplated that a method of manufacturing a counter-flow heat exchanger core, e.g. heat exchanger core <NUM>, includes forming heat exchanger core <NUM> using additive manufacturing such as, SLM or DMLS, for example. It is contemplated that the heat exchanger core can be manufactured in the flow direction, e.g. along longitudinal axis X to avoid horizontal surfaces. It is also contemplated that instead of being a linearly extending cylinder, the heat exchanger could be built along a sinusoidal path creating wavy or ruffled sets of channels as opposed to straight ones for increased heat transfer or bend around obstructions.

Claim 1:
A counter-flow heat exchanger core (<NUM>) comprising:
a first wall (<NUM>) defining a longitudinal axis;
a first flow path (<NUM>) defined within the first wall, wherein the first flow path includes a primary flow inlet (<NUM>) and a primary flow outlet (<NUM>) downstream from the primary flow inlet;
at least two hollow vanes (<NUM>) circumferentially spaced apart and extending in a radially inward direction from the first wall (<NUM>), wherein each of the at least two hollow vanes includes a first vane wall (<NUM>) and a second vane wall (<NUM>);
a second flow path defined within the at least two hollow vanes between the first vane wall and second vane wall of each of the at least two hollow vanes; and
at least one fin extending between two of the at least two hollow vanes (<NUM>);
characterized in that the at least one fin is at least one non-linear fin that includes a plurality of non-linear fins (<NUM>) between two of the hollow vanes, wherein the plurality of non-linear fins are variably spaced apart in a radial direction to the first wall.