Patent Description:
Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) include a variety of heat exchangers.

Examples of gas turbine engine heat exchangers are found in: <CIT>, "HIGH TEMPERATURE PLATE FIN HEAT EXCHANGER"; <CIT>, "HEAT EXCHANGER BELL MOUTH INLET"; and <CIT>, "METHOD FOR MANUFACTURING A CURVED HEAT EXCHANGER USING WEDGE SHAPED SEGMENTS".

An example positioning of such a heat exchanger provides for the transfer heat from a flow (heat donor flow) diverted from an engine core flow to a bypass flow (heat recipient flow). For example, air is often diverted from the compressor for purposes such as cooling. However, the act of compression heats the air and reduces its cooling effectiveness. Accordingly, the diverted air may be cooled in the heat exchanger to render it more suitable for cooling or other purposes. One particular example draws the heat donor airflow from a diffuser case downstream of the last compressor stage upstream of the combustor. This donor flow transfers heat to a recipient flow which is a portion of the bypass flow. To this end, the heat exchanger may be positioned within a fan duct or other bypass duct. The cooled donor flow is then returned to the engine core (e.g., radially inward through struts) to pass radially inward of the gas path and then be passed rearward for turbine section cooling including the cooling of turbine blades and vanes. The heat exchanger may conform to the bypass duct. The bypass duct is generally annular. Thus, the heat exchanger may occupy a sector of the annulus up to the full annulus.

Other heat exchangers may carry different fluids and be in different locations. For example, instead of rejecting heat to an air flow in a bypass duct, other heat exchangers may absorb heat from a core flow (e.g., as in recuperator use).

Among recently proposed annular heat exchangers are those in <CIT>, "HEAT EXCHANGERS" and <CIT>, "Methods of cooling a fluid using an annular heat exchanger". Document <CIT> discloses a heat exchanger according to the preamble of claim <NUM>.

According to an aspect of the present invention, there is provided a heat exchanger for heat exchange between a first fluid and a second fluid in accordance with claim <NUM>.

Optionally, the fiber members comprise glass fibers.

Optionally, the fiber members comprise woven fiber tape.

Optionally, for each stage of a plurality of stages of the tubes, the fiber members comprise: a first fiber member between alternate legs of the tube sections; and a second fiber member between alternate legs of the tube sections and out of phase with the first fiber member.

Optionally, the first fiber member and second fiber member comprise woven fiber tape.

Optionally, the support further comprises: a further fiber member between the fiber members and the end plate.

Optionally, the support is a first support and the heat exchanger comprises a second support spaced from the first support and comprising: fiber members passing between legs of the tube sections; and an end plate.

Optionally, the heat exchanger further comprises means for maintaining a spacing between the first support and the second support.

Optionally, the support end plate comprises a metallic body.

Optionally, the plurality of tube sections have flattened intermediate portions along their first legs and second legs.

Optionally, the manifold comprises a plate stack.

Optionally, the plurality of tube sections are positioned in a plurality of stages from upstream to downstream along a flowpath of the second fluid.

Optionally, the manifold has a convex outer surface from which the plurality of tube sections extend.

Optionally, a turbine engine includes the heat exchanger and further comprises a gas path passing gas across exteriors of the plurality of tube sections.

Optionally, the turbine engine further comprises: a recuperator including the heat exchanger.

Optionally, a method for using the heat exchanger comprises: passing a first fluid flow through interiors of the tubes; and passing a second fluid flow along a second flowpath across exteriors of the tubes, wherein: the passing of the first flow and the second flow thermally expands the length of the tube sections to cause a sliding interaction between the tubes and the fiber members.

Optionally, passing the second flow is passing of combustion gases in a gas turbine engine.

<FIG> shows a heat exchanger <NUM> providing heat exchange between a first flowpath <NUM> (<FIG>) and a second flowpath <NUM> and thus between their respective first and second fluid flows <NUM> and <NUM>. In the example embodiment, the flowpaths <NUM>, <NUM> are gas flowpaths passing respective gas flows <NUM>, <NUM>. In the illustrated example, the first flow <NUM> enters and exits the heat exchanger <NUM> as a single piped flow and the flow <NUM> is an axial annular flow surrounding a central longitudinal axis <NUM> (<FIG>) of the heat exchanger. <FIG> also shows an axial direction <NUM> as a generally downstream direction along the second flowpath <NUM>. In a coaxial duct within a gas turbine engine, the axis <NUM> may be coincident with a centerline of the engine and an axis of rotation of its spools, the direction <NUM> is an aftward/rearward direction, and a radial direction is shown as <NUM>.

The heat exchanger <NUM> has a first flow inlet <NUM> (<FIG>) and a first flow outlet <NUM> along the first flowpath <NUM>. The example inlet and outlet are, respectively, ports of an inlet manifold <NUM> and an outlet manifold <NUM>. Example manifolds are metallic (e.g., nickel-based superalloy). The inlet manifold and outlet manifold may each have a respective fitting 30A, 30B providing the associated port <NUM>, <NUM>. Each manifold <NUM>, <NUM> further has a body piece 32A, 32B extending circumferentially about the axis <NUM> from the associated fitting 30A, 30B and port <NUM>, <NUM>. The example manifolds have continuously curving arcuate form.

The example heat exchanger <NUM> is a continuous full annulus heat exchanger. An alternative but otherwise similar heat exchanger may be circumferentially segmented into a plurality of segments (e.g., four segments or three to eight segments). Each segment may, itself, be identified as a heat exchanger. Depending upon situation, the segments may be plumbed to have respective first flow <NUM> segments in parallel, in series, or two totally different first flows.

As is discussed further below, the manifolds <NUM> and <NUM> are portions of a larger manifold assembly (manifold) <NUM> which comprises a stack <NUM> of plates discussed below in addition to the body pieces 32A, 32B.

A plurality of heat transfer tubes <NUM> each extend between a first end <NUM> (<FIG>) and a second end <NUM> at ends of respective legs <NUM> and <NUM>. Portions of the tubes at the ends <NUM> and <NUM> are received in the manifold stack <NUM>. The tubes are bent to be generally U-shaped in planform having respective distal turns <NUM> (<FIG>). The example turns are about <NUM>°. Interiors of the tubes fall along the associated branch of the first flowpath <NUM> to pass an associated portion of the first flow <NUM>. Central exposed exterior surfaces of the tubes are along the second flowpath <NUM> in heat exchange relation with the second flow <NUM>.

In the example implementation, the manifold assembly <NUM> is a combined inlet, outlet, and transfer manifold including the overall heat exchanger inlet and outlet manifolds <NUM>, <NUM>. The transfer manifold function involves transferring from one stage of tubes to the next. In the <FIG> example, there are three stages of tubes. The transfer manifolds (and their associated plenums) thus lack immediate external communication. <FIG> shows the inlet manifold <NUM> having an inlet plenum 46A feeding the first legs <NUM> of the first stage 40A of tubes. A transfer plenum 46B transfers output of the first stage 40A second legs <NUM> to a transfer plenum 46C which feeds the first legs of the tubes of the second tube stage 40B. A transfer plenum 46D receives the output of the second stage 40B second legs and passes it to a transfer plenum 46E which feeds the third stage 40C first legs. A discharge plenum 46F of the discharge manifold <NUM> receives the output of the third stage 40C second legs <NUM> for discharge from the outlet <NUM>.

As is discussed further below, the stack <NUM> of plates (<FIG>) extends between a first axial end <NUM> and a second axial end <NUM>. Each of the plates has a pair of opposite faces (axially-facing or radially/circumferentially extending), an inner diameter (ID) surface, and an outer diameter (OD) surface. In the example embodiment, the plates are stacked with the aft (downstream along the example second flowpath <NUM>) face of one plate contacting and secured to the forward/upstream face of the next. From upstream-to-downstream along the second flowpath <NUM> or fore-to-aft in the axial direction <NUM>, the end sections or portions of groups of the tube legs are mounted in pockets <NUM> (<FIG>) formed between the mating plates.

In the example, the tubes of each stage are circumferentially in phase with the tubes of the other stages. However, other configurations may have the tubes of each stage staggered to relative to the adjacent stage(s) to provide out-of-phase registry with the tubes of the adjacent stage fore or aft (e.g., each tube of a given stage is circumferentially directly between two adjacent tubes of each of the two adjacent stages). In the example, the bent tubes have a first face <NUM> (<FIG>) and a second face <NUM> (e.g., facing toward and away from a viewer when viewing the tube as a "U") with a centerplane <NUM> parallel to and between the faces. The example plane is at an angle θ relative to a transverse (circumferential in the annular embodiment) direction <NUM>. Example θ (when not <NUM>° of <NUM>°) is about <NUM>°, more broadly <NUM>° to <NUM>°.

<FIG> shows pockets <NUM> at the plate junctions accommodating the tube leg end sections. With example circular-section tubing, the pockets <NUM> are essentially right circular cylindrical pockets split evenly between the two plates and provided by respective semicylindrical grooves <NUM> (<FIG>) in the two faces. The grooves (or pocket segments/sections) <NUM> have surfaces <NUM> and extend between the associated OD surface <NUM> of a plate on the one hand and a plenum 46A-F discussed above on the other hand.

With the example arcuate manifold configuration, the tubes in each group circumferentially diverge from each other in the radial direction from the manifold assembly <NUM>. Despite this radial fanning arrangement, each group may be identified as a "row" as is common practice with tube-bank heat exchangers. Depending upon implementation, the two legs of each tube may be parallel to each other with the divergence occurring only between adjacent legs of different tubes or the legs of a given tube may slightly diverge. The former (legs of a given tube parallel to each other) may make assembly easier.

The plates of the stack <NUM> (<FIG>) include a first end plate <NUM>, a second end plate <NUM>, and one or more intermediate plates. Depending on implementation, the intermediate plates may be the same as each other or different from each other. In the illustrated example, the intermediate plates are: first and second penultimate plates <NUM> and <NUM> respectively adjacent the first and second end plates <NUM> and <NUM>; and alternating first intermediate plate(s) <NUM> and second intermediate plate(s) <NUM>.

For full annular heat exchangers there may be a thousand or more tubes per row. Even for a smaller segment of a circumferentially segmented heat exchanger, there may be hundreds of tubes per row or more in the segment. There may be at least an example twenty in a segment (whether stand-alone or assembled with other segments such as sectors discussed above) or a range of twenty to one thousand or twenty to two hundred). An example number of rows is at least two or at least three. Upper limits may be influenced by diminishing return on heat transfer and by increasing fluidic losses along both flowpaths. Thus, an example upper limit on rows is ten with a likely sweet spot of three to six rows.

The manifold <NUM> has an outer diameter (OD) surface from which the tubes protrude. This outer diameter surface is formed by the combined outer diameter (OD) surfaces <NUM> (<FIG>) of the plates (inner diameter (ID) surfaces shown as <NUM>). In the example, the end plates <NUM> and <NUM> have flat first end faces forming the axial ends <NUM> and <NUM> and second (axially inboard/interior) faces including the groove <NUM> surfaces <NUM>. <FIG> shows such a second face of the end plates <NUM>, <NUM> having the grooves <NUM> in an outer diameter section <NUM> (between intact portions <NUM> of a planar face) and having a relieved inner diameter section <NUM>. The inner diameter section cooperates (with a similar section of the axially outboard face of the mating penultimate plate <NUM>, <NUM>) to form an annular portion of the associated plenum 46A, 46F in combination with an adjacent annular outwardly-open channel in the inlet or outlet manifold body piece 32A, 32B.

The adjacent face of the respective penultimate plate <NUM>, <NUM> is similarly configured to and represented by the <FIG> illustration. The opposite face (axially inboard) of each penultimate plate <NUM>, <NUM> has a similar outboard portion <NUM> (<FIG>) but an intact inboard portion <NUM> leaving an intermediate portion forming an annular channel <NUM> radially therebetween for forming one half of the associated transfer plenum 46B, 46C, 46D, 46E. <FIG> shows the intact nature of the section <NUM> having a face <NUM> coplanar with intact portions of the outboard portion between the grooves <NUM>.

The first intermediate plates <NUM> have two faces (<FIG>) of similar geometry to the penultimate plate <NUM>, <NUM> inboard faces of <FIG> but having an intermediate channel-forming section <NUM> differing from section <NUM> by having a plurality of through-holes <NUM>. Through-holes <NUM> provide transfer from one stage to the next.

The second intermediate plate(s) <NUM> have both faces similar to the <FIG> face and lacking such through-holes <NUM>.

Aerodynamic forces from the second flow <NUM> as well as other vibrations may cause deleterious resonant behavior in the tubes. Accordingly, it is desirable to support the tubes at one or more radial locations outboard of the manifold <NUM>. <FIG> shows an outer diameter support assembly <NUM> and an intermediate support assembly <NUM>. The number of support assemblies may depend upon numerous factors including the radial span of the tubes.

Each support assembly <NUM>, <NUM> includes one or more fiber members engaging the tubes. The fiber members help maintain spacings of the tubes, preventing/damping potentially damaging vibrations while accommodating differential expansion of the tubes (e.g., the tubes can radially slide relative to the fiber members). In the illustrated example, each support comprises pairs of fiber members interwoven with the tube legs. Example fiber members are in strip form such as woven straps or tapes. Example fiber material is glass fiber. Alternative forms include woven twisted threads and non-woven batts (batting).

In this example, the OD support <NUM> has pairs of fiber straps engaging groups of tube legs out of phase with each other. For example, with the outer support, there are pairs of associated proximal (closer to the manifold) fiber straps <NUM> (<FIG>) and distal fiber straps <NUM>. <FIG> shows the fiber straps as having proximal edges <NUM> and distal edges <NUM> (<FIG>). In the example, the proximal fiber strap <NUM> distal edge abuts the distal fiber strap <NUM> proximal edge. <FIG> also shows a woven fiber strap <NUM> at one end of the tube array. This may have a height equivalent to the combined heights of the other straps on a given stage.

An example of a woven sheet material that may be cut into strips/straps <NUM>, <NUM>, <NUM> is "Fiberglass Fabric Gasket Sheet" of USA Sealing, Buffalo, NY.

Thread instead of such straps may be particularly relevant to finer tubes with smaller spacings. An example twisted fiberglass thread is "Chemical-Resistant High-Temperature Thread" of McMaster-Carr, Aurora, OH. Typically sold as PTFE coated. the PTFE may ease interweaving of the thread with the tubes but may be baked off pre-use. If such thread is directly used, is particularly likely that there are many more than two spanwise stacked threads.

Alternative fiber material includes carbon fiber and ceramic fiber. Glass has advantages of durability over ceramic and temperature capability over carbon fiber.

In the example, the intermediate support <NUM> (<FIG>) has similar proximal straps <NUM> and distal straps <NUM>.

The OD support further includes metallic end plates <NUM>, <NUM> and the intermediate support includes similar end plates <NUM>, <NUM>. Each support may be axially held together by fasteners <NUM> such as bolt <NUM> and nut <NUM> combinations extending through axial holes in the stack. The fiber members are shown particularly schematically because actual configurations may have the fiber members locally compressed to conform where contacting, tubes, plates, and other fiber members. Additionally, axial spacers (not shown) such as axial metallic struts may, under compression, bridge the end plates to maintain their axial/longitudinal spacing and prevent overcompression by the fasteners. Or the fasteners themselves may maintain the spacing such as via intermediate nuts. Or struts alone may be fastened to the end plates by fasteners, welding, or the like. Additional overwrapping or other means for further radially containing/constraining the fiber members may be provided.

<FIG> further shows radial straps or struts <NUM>, <NUM> (e.g., metallic) securing supports <NUM>, <NUM>, <NUM>, <NUM> to each other and to the manifold <NUM> to maintain spacing. The example radial straps <NUM>, <NUM> may be secured via the fasteners <NUM> to the associated supports and may be similarly secured to the manifold or may be brazed, welded, or diffusion bonded to the manifold. In alternative embodiments, the straps only connect the supports to each other and not to the manifold and/or may connect to radially outboard environmental structure (e.g., an outer duct wall).

Depending upon implementation, the fiber straps <NUM>, <NUM>, <NUM> may be retained against becoming dislodged such as via additional through-fasteners (not shown) similar to the fasteners <NUM>. For example, at a given transverse position (circumferential in the annular embodiment) there may be two radially-spaced through-fasteners associated with the respective two radial positions of fiber straps <NUM>, <NUM>.

In variations, there may different interweavings of the fiber straps relative to the tubes. This may depend upon tube orientation.

In further variations, there simply could be fiber layers extending transversely (circumferentially for the annular heat exchanger) between stages and/or between legs of a given stage. For example, with the <FIG> angled configuration, the alternative could include alternating sets of layers between tube stages and layers between the legs of a given tube stage.

Similarly, other variations could involve axial interweaving and/or diagonal interweaving.

Although separate weaves and layers are shown, there may be a continuous weave progressing from one stage to another or otherwise from one group of tubes or tube legs to another. For example, a weave might proceed axially through an axial group of tube legs from one axial end of the heat exchanger to the other then turn and come back along the next axial group, etc..

In use, differential thermal expansion may cause relative sliding of the tubes and fiber members. The particular direction of motion may depend on several factors including the temperatures of the fluid flows. An example temperature domain may involve peak temperature in the range of <NUM> to <NUM> for placement in a combustion gas flow. When used as an intercooler, temperatures may be about <NUM>.

Example tube outer diameters are <NUM> to <NUM>, more broadly <NUM> to <NUM>. Example tube radial protrusions (radial span between manifold OD and turn OD) are at least <NUM>, more particularly <NUM> to <NUM>.

Component materials and manufacture techniques and assembly techniques may be otherwise conventional. The tubes may be formed by extrusion or sheet metal rolling techniques, cut to length, and bent to shape. The manifold components may be machined from ingot stock or may be forged and machined or may be cast and machined. Fiber straps may be woven via conventional techniques. Metal straps and supports may be cut and bent from sheet or strip stock.

Depending upon implementation, assembly of the fiber members to the tubes may be performed before assembly of the tubes to the manifold or manifold components or after, or during. In an example of pre-assembly, groups of tubes may be held in a fixture and the fiber strap(s) may be pre-formed into a wave and slid past the ends of the tube legs.

Material may be compatible with operational conditions. Example tube, manifold, support <NUM>, <NUM>, and strap <NUM>, <NUM> material are stainless steels and nickel-based superalloys.

Elements shown as individual pieces may be formed as multiple pieces and then integrated (e.g., via casting annular manifold segments and integrating into a full annulus such as by welding, diffusion bonding, and the like).

The heat exchanger may be assembled in layers starting with a plate at one end of the manifold stack and the associated fiber member(s) at the end(s) of their stack(s). The tubes may be put in place and subsequent layers built up. Depending upon implementation, the tubes may be placed flat atop exposed faces of the plates and fiber member(s) or may need to be inserted radially inward.

On stack completion, the bolts <NUM> or other fasteners (if present) may be inserted through pre-drilled holes (or the fasteners may have been preinstalled and used to help align subsequent blocks during stacking). Nuts <NUM> may be attached and tightened.

The plates of the manifold may be secured to each other such as via brazing, diffusion bonding, or welding, or may be secured such as by using fasteners as with the bolts.

In some embodiments/uses, the first flow <NUM> may be a pumped liquid and may remain a pumped liquid. In alternative embodiments/uses, the first flow may be a gas or may start out as a liquid and may be fully or partially vaporized.

An example specific use situation is in a recuperator or waste heat recovery wherein the first flow <NUM> is of the recuperator working fluid (e.g., carbon dioxide). The heat exchanger <NUM> may be used as a heat absorption heat exchanger in the hot section of the engine (e.g., absorbing heat from combustion gases (as the second flow <NUM>) in an exhaust duct downstream of the turbine). Alternatively, the heat exchanger may be used as a heat rejection heat exchanger (e.g., rejecting heat to air (as the second flow <NUM>) in a fan duct or other bypass).

<FIG> schematically illustrates a gas turbine engine <NUM>, including the heat exchanger <NUM> in a waste heat recovery system (recuperator) <NUM>. The example engine is an aircraft propulsion engine, namely a turbofan. The engine has a fan section <NUM>, one or more compressor sections <NUM>, a combustor section <NUM> and one or more turbine sections <NUM>, sequentially along a primary fluid flowpath (core flowpath). The fan also drives air along an outboard bypass flowpath. The example engine is a two-spool engine with the low spool directly or indirectly (e.g., via reduction gearbox) driving the fan. Example combustors are annular combustors and can-type combustor arrays.

A downstream section of the core flowpath provides the second flowpath <NUM>. Downstream of the turbine section <NUM> is an exhaust casing <NUM> which exhausts combustion gas (as the fluid flow <NUM>) into an ambient atmosphere downstream of the turbine.

In order to recapture the waste heat from the combustion gas flow <NUM> and convert the waste heat to work, the heat exchanger <NUM> is positioned within the exhaust casing <NUM>. The first flowpath <NUM> is a leg of a supercritical CO<NUM> (sCO<NUM>) bottoming Brayton cycle (referred to herein as the waste heat recovery system <NUM>). The heat exchanger <NUM> is connected to transfer heat from the turbine exhaust to the waste heat recovery system <NUM>, and the waste heat recovery system <NUM> converts the heat into rotational work (which may be used for various purposes such as driving an electrical generator (not shown) to power aircraft systems). The waste heat recovery system <NUM> may additionally recuperate waste heat within the recovery system <NUM> and is referred to as a recuperating bottoming cycle.

The waste heat recovery system <NUM> has a turbine <NUM> with an inlet <NUM> connected to an output of the heat exchanger <NUM>. The turbine <NUM> expands the heated working fluid (CO<NUM> or other cryogenic fluid <NUM>) and expels the heated working fluid through a turbine outlet <NUM>. The expelled working fluid is passed through a relatively hot passage of a recuperating heat exchanger <NUM>, and is passed to a relatively hot passage of a heat rejection heat exchanger <NUM>. The heat exchanger <NUM> may be positioned to reject thermal energy from the working fluid to ambient air (e.g., fan bypass air). After passing through the heat rejection heat exchanger <NUM>, the working fluid is passed to an inlet <NUM> of a compressor <NUM>. The compressor <NUM> (driven by the turbine <NUM> (e.g., co-spooled)) compresses the working fluid, and passes the compressed working fluid from a compressor outlet <NUM> to a cold passage of the recuperating heat exchanger <NUM>.

During operation of the waste heat recovery system <NUM>, the compressor <NUM> compresses the working fluid, and passes the compressed working fluid through the recuperating heat exchanger <NUM> and the heat exchanger <NUM>, causing the compressed working fluid to be heated in each of the heat exchangers <NUM>, <NUM>. The heated working fluid is provided to the inlet <NUM> of the turbine <NUM> and expanded through the turbine <NUM>, driving the turbine <NUM> to rotate. The rotation of the turbine <NUM> drives rotation of the compressor <NUM> and of an output shaft <NUM>. The output shaft <NUM> may be mechanically connected to one, or more, additional turbine engine systems and provides work to those systems using any conventional means for transmitting rotational work. Additionally or alternatively, the rotational work can be converted into electricity and used to power one or more engine or aircraft systems using a conventional electrical generator system coupled to the output shaft.

Numerous variations may be implemented. For example, whereas the <FIG> heat exchanger is full annulus, the heat exchanger and/or various of its components may be circumferentially segmented. At a minimum, the fiber member(s) may be formed as segments of an annulus with each fiber member(s) stage being assembled as a circumferential array of segments. The segments of each sequential stage may be out of phase with each other to improve structural rigidity. The circumferentially segmented fiber member(s) stage may held mounted in annular form by the front and rear plates and/or by mounting to environmental structure.

Although shown with transversely-extending fiber member(s) (circumferential in the annular example) other fiber member(s) orientations may be provided including axially-extending.

Although each <FIG> tube is oriented diagonally (e.g., the legs are axially and circumferentially offset from each other) other configurations may involve tubes wherein the legs are not axially offset from each other or not circumferentially offset from each other. That latter example may be particularly amenable to the aforementioned axially-extending alternative block configurations.

Although the example fiber member(s) capture portions of the legs leaving the turn protruding out from the associated fiber member(s) alternative examples may involve embedding the turn in the associated fiber member(s).

Although discussed in the context of an annular heat exchanger other configurations are possible. For example, in a rectangular duct a bank of tubes may extend parallel from a straight/flat manifold. Depending upon implementations, there may be two opposite banks extending in opposite directions such as from opposite faces of a single central manifold.

As an example of several such variations, <FIG> and <FIG> show a heat exchanger <NUM> that is not full annulus but, extends between ends <NUM>, <NUM> transverse to the flowpath <NUM>. Additionally, rather than being an arcuate segment (e.g., in a situation where multiple segments are assembled end-to-end to form an annulus) the heat exchanger is straight (e.g., rectangular in footprint looking up or down the flowpath <NUM>). Additionally, the legs of a given tube are oriented similarly transverse to the second flowpath <NUM> rather than at an angle (θ is <NUM>° vs the ~<NUM>° of <FIG>). <FIG> and <FIG> show a downstream direction <NUM> of the flowpath <NUM>, a direction <NUM> outward from the manifold, and a transverse direction <NUM> normal thereto.

The tube support <NUM> (<FIG>) comprises fiber members passing between legs of the tube sections. For each stage of tubes, the fiber members include a proximal fiber member <NUM> (closer to the manifold <NUM>) and a distal fiber member <NUM>. In the example, for each stage of tubes, the fiber members <NUM> and <NUM> are exactly out-of-phase with each other. Thus, when one fiber member <NUM>, <NUM> passes in front of a tube leg, the other passes behind that tube leg. From stage-to-stage, the fiber members <NUM> and <NUM> may be in-phase with the corresponding members of the adjacent stages. <FIG> shows how this results in nesting of the fiber members of adj acent rows. To better illustrate the interweaving of the members and tube legs, <FIG> thus is not a true sectional view where the fiber members of one or two adjacent stages would be cut. Rather it's a cutaway by entirely removing the fiber members of the tube stages that are above the view lane.

Example fiber members <NUM>, <NUM> are woven fiber straps. Alternative fiber members may be as discussed above.

Optionally, at ends of the stack, fiber members such as straps or batts (batting) <NUM> (<FIG>) may intervene between the end plate(s) <NUM>, <NUM> the adjacent members <NUM>, <NUM>. The end plates may sandwich the tubes and fiber members and be secured via fasteners as discussed above.

In the example, the manifold <NUM> (<FIG>) has, at each fore-to-aft stage location, a pair of plenums <NUM>, <NUM> separated from each other by a wall <NUM>. Tube end portions may be of different lengths so that one end portion of each tube is in communication with the first plenum <NUM> and another in communication with the second plenum <NUM>.

As a further variation, intermediate portions of the tube legs are shown flattened transversely to the flowpath <NUM> to improve rigidity and aerodynamic stability and increase thermal exposure while limiting restriction of the flow <NUM>. A flattening elongates such intermediate sections of the tubes in the direction of the flowpath <NUM>.

If an intermediate support is present, an adjacent portion of the tube may be undeformed and of circular cross-section. Or, a different weave may be used to accommodate.

<FIG> and <FIG> show supports, straps, and fasteners similar to those in <FIG>. Not shown are the overall inlet and outlet ports and plenum-to-plenum transfer apertures similar to those of the <FIG> embodiment.

Also, regarding use variations, some variations may have a fuel as the first fluid flow <NUM>. Although the heat exchanger may transfer heat to a conventional liquid fuel (e.g., kerosene-type jet fuels (such as Jet A, Jet A-<NUM>, JP-<NUM>, and JP-<NUM>), the heat exchanger may be used for future fuels such as liquid hydrogen, potentially vaporizing that fuel.

Where a measure is given in English units followed by a parenthetical containing SI or other units, the parenthetical's units are a conversion and should not imply a degree of precision not found in the English units.

Claim 1:
A heat exchanger (<NUM>) for heat exchange between a first fluid (<NUM>) and a second fluid (<NUM>) and comprising:
a plurality of tube sections (<NUM>), each comprising:
an interior for passing the first fluid (<NUM>);
an exterior for exposure to the second fluid (<NUM>);
a first leg (<NUM>);
a second leg (<NUM>); and
a turn (<NUM>) joining the first leg (<NUM>) to the second leg (<NUM>); and
a manifold (<NUM>), wherein the first leg (<NUM>) and the second leg (<NUM>) of each of the tube sections (<NUM>) are mounted to the manifold (<NUM>) and in communication therewith, characterised in that the heat exchanger (<NUM>) further comprises:
a support (<NUM>, <NUM>) comprising:
fiber members (<NUM>, <NUM>, <NUM>, <NUM>) engaging the tubes by
passing between the legs (<NUM>, <NUM>) of the tube
sections (<NUM>); and
a first end plate (<NUM>, <NUM>);
and a second end plate (<NUM>, <NUM>) sandwiching the fiber members (<NUM>, <NUM>, <NUM>, <NUM>) and plurality of tube sections (<NUM>) between the first end plate (<NUM>, <NUM>) and the second end plate (<NUM>, <NUM>).