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> relates to a heat exchanger for an internal combustion engine. <CIT> relates to tubular heat exchangers. <CIT> relates to heat exchangers.

A counter-flow heat exchanger comprising a heat exchanger core including an inner wall and an outer wall radially outward and spaced apart from the inner wall. A first flow path is defined within the inner wall and a second flow path is defined between the inner wall and the outer wall. The heat exchanger core includes a primary flow inlet, a primary flow outlet and a middle portion therebetween. The inner and outer walls are concentric at the primary flow inlet of the heat exchanger core. The inner wall defines a first set of channels extending axially from the primary flow inlet to the middle portion of the heat exchanger core gradually diverging away from a radial center of the heat exchanger core as the inner wall extends away from the primary flow inlet. The inner wall and the outer wall define a second set of channels extending axially from the primary flow inlet to the middle portion of the heat exchanger core converging toward the radial center of the heat exchanger core.

In accordance with certain embodiments, the inner wall is corrugated to form the first and second sets of channels. Respective channels of the first and second sets of channels can alternate circumferentially with one another. The heat exchanger core is a circular cylinder. At the primary flow inlet of the heat exchanger core, in a cross-section taken perpendicular to a primary flow direction, the inner and outer walls define an annulus therebetween including the second flow path. A diameter of the heat exchanger core at the primary flow inlet is smaller than a diameter of the heat exchanger core in the middle portion. At least one channel of the first set of channels can split into multiple sub-channels to maintain a width smaller than a maximum threshold. At least two channels of the second set of channels can unite into a single joined channel to maintain a width greater than a minimum threshold.

It is contemplated that at least one of the first and second flow paths can include vanes to assist with flow distribution. The heat exchanger core can be substantially linear and can define a longitudinal axis between the primary flow inlet and the primary flow outlet. A radial center of the inner wall can be aligned with the longitudinal axis. Additional cylindrical walls can be disposed radially inward from the outer wall and concentric with the heat exchanger core. The additional cylindrical walls can be radially spaced apart from one another and are in fluid communication with the first and second flow paths. Annular ring sections can be defined between two adjacent cylindrical walls. Each annular ring section can include a portion of a channel from the first set of channels and a portion of a channel from the second set of channels. The portion from the first set of channels in a first annular ring section can be offset radially and circumferentially from the portion from the first set of channels in a second annular ring section. The second annular ring section can be adjacent to the first annular ring section. The portion from the second set of channels in the first annular ring section can be offset radially and circumferentially from the portion from the second set of channels in the second annular ring section. The additional cylindrical walls can be circular cylindrical walls. The additional cylindrical walls can be disposed in the middle portion of the heat exchanger core. The inner and outer walls can be concentric at the primary flow outlet of the heat exchanger core.

The heat exchanger core can be cylindrical, wherein at an outlet of the heat exchanger core, in a cross-section taken perpendicular to a primary flow direction, an annulus can be defined between the inner and outer walls. From the middle portion of the heat exchanger core to the primary flow outlet, the first set of channels can extend axially away from the middle portion to the primary flow outlet converging toward the radial center of the heat exchanger core and the second set of channels can extend axially away from the middle portion to the primary flow outlet diverging away from the radial center of the heat exchanger core. In accordance with another aspect, a method of manufacturing a counter-flow heat exchanger core includes forming a heat exchanger core body using additive manufacturing. The heat exchanger core body is similar to the heat exchanger core described above. Additive manufacturing can be via direct metal laser sintering.

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 to which the subject invention appertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described by way of example only 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 in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Other embodiments of imaging systems in accordance with the disclosure, or aspects thereof, are provided in <FIG>, as will be described. Embodiments of heat exchanger <NUM> provide a fractal heat exchanger core that results in increased performance, and reduced size and weight as compared with traditional plate fin heat exchangers.

As shown in <FIG>, 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 inner 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> and an outer wall <NUM> radially outward and spaced apart from inner wall <NUM>. A first flow path <NUM> is defined within inner 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> 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> 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 132a is offset radially and circumferentially from portion <NUM>' from first set of channels <NUM> in a second annular ring 132b section. Second annular ring section 132b is adjacent to first annular ring section 132a. Portion <NUM>' from the second set of channels <NUM> in first annular ring section 132a is offset radially and circumferentially from portion <NUM>' from second set of channels <NUM> in second annular ring section 132b.

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, direct metal laser sintering, 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 (<NUM>) comprising:
a heat exchanger core (<NUM>) including an inner wall (<NUM>) and an outer wall (<NUM>) radially outward and spaced apart from the inner wall (<NUM>), wherein a first flow path (<NUM>) is defined within the inner wall (<NUM>) and a second flow path (<NUM>) is defined between the inner wall (<NUM>) and the outer wall (<NUM>), wherein the heat exchanger core (<NUM>) includes a primary flow inlet (<NUM>), a primary flow outlet (<NUM>) and a middle portion (<NUM>) therebetween, wherein the inner and outer walls (<NUM>, <NUM>) are concentric at the primary flow inlet (<NUM>) of the heat exchanger core (<NUM>), wherein the inner wall (<NUM>) defines a first set of channels (<NUM>) extending axially from the primary flow inlet (<NUM>) to the middle portion (<NUM>) of the heat exchanger core (<NUM>) gradually diverging away from a radial center of the heat exchanger core (<NUM>) as the inner wall (<NUM>) extends away from the primary flow inlet (<NUM>), and wherein the inner wall (<NUM>) and the outer wall (<NUM>) define a second set of channels (<NUM>) extending axially from the primary flow inlet (<NUM>) to the middle portion (<NUM>) of the heat exchanger core (<NUM>) converging toward the radial center of the heat exchanger core (<NUM>) wherein the heat exchanger core is a circular cylinder, wherein at the primary flow inlet of the heat exchanger core, in a cross-section taken perpendicular to a primary flow direction, the inner and outer walls define an annulus therebetween including the second flow path, and wherein a diameter of the heat exchanger core at the primary flow inlet is smaller than a diameter of the heat exchanger core in the middle portion.