Patent Description:
Heat exchangers are used in various contexts to transfer heat from one fluid stream to another, for heating, cooling or both. While various configurations of heat exchangers exists, there always remains room for improvement. In aircrafts, for instance, weight can be a significant concern, in addition to footprint (volume), durability, reliability and costs. Lower weight can sometimes be achieved by improving heat transfer efficiency. One strategy to improve efficiency is to divide the flow into a number of flow path, and thereby facilitate heat transfer between the narrower flow paths and the other fluid as compared to between a single larger flow path and the other fluid. This approach can, however, pose design challenges.

<CIT> discloses a heat exchanger according to the preamble of claim <NUM> and describes an exhaust gas heat exchanger and sealing device for the same.

<CIT> discloses a prior art tubular boiler heat exchanger for two fluids, at least one of which is at least partially evaporated.

<CIT> discloses a prior art heat exchanger having a coaxial or concentric tube construction.

<CIT> discloses a prior art counterflow heat exchanger.

<CIT> discloses a prior art heat exchanger with an annular coolant chamber.

<CIT> discloses a prior art tubular heat exchanger.

<CIT> discloses a prior art tube body and heat exchanger formed by using the same.

<CIT> discloses prior art improvements in methods of connecting groups of concentric tubes.

<CIT> discloses a prior art double pipe type heat exchanger, manufacturing method and heat pump.

In one aspect, there is provided a heat exchanger as set forth in claim <NUM>.

In a further embodiment of the above, the first inlet has the first mouth, the first outlet has a third mouth dividing internally into a second number of passages, the adapter is a first adapter, further comprising a second adapter having a fourth mouth secured to the third mouth.

In a further embodiment of any of the above, a periphery of the second mouth is welded to the periphery of the first mouth.

In a further embodiment of any of the above, the passages each have a circular cross-section and extend lengthwisely from a corresponding location within the periphery of the mouth.

In a further embodiment of any of the above, the second fluid circuit further comprises a plurality of outer passages circumferentially interspersed with the passages of the first fluid circuit in the heat transfer region.

In a further embodiment of any of the above, the arm is a first arm, the first housing further having a second arm having a third mouth at a proximal end, the adapter is a first adapter, wherein the sleeve is a first sleeve, the second housing further having a second sleeve receiving the second arm therein in the assembled configuration, further comprising a second adapter having a fourth mouth secured to the third mouth.

In a further embodiment of any of the above, the first arm and second arm are parallel to one another and fluidly interconnected by a transversally-extending mixing cavity.

In a further embodiment of any of the above, the second fluid circuit has a segment extending transversally between the first and second sleeves.

In a further embodiment of any of the above, the segment is a mixing cavity formed between the second housing and the first housing.

In a further embodiment of any of the above, the second fluid circuit further comprises a circumferential spacing between the arm and the sleeve.

In a further embodiment of any of the above, an outer surface of the arm further comprises a plurality of grooves defined therein and extending along the length of the arm.

In a further embodiment of any of the above, the mixing cavity has an aperture closed by a plug or cover.

In a further embodiment of any of the above, the first housing and the second housing are brazed to one another at the base and at the proximal ends of the arms.

In another aspect, there is provided a method of assembling a heat exchanger as set forth in claim <NUM>.

In a further embodiment of any of the above, said engaging the proximal end of the arm further includes, simultaneously, engaging a proximal end of a second arm into a distal opening of a second sleeve, along a length of the second sleeve, and out a proximal opening of the second sleeve, the proximal end of the second arm having a third mouth.

In a further embodiment of any of the above, the first and second sleeves are structurally interconnected by a transversal member at the distal end, and the first and second arms are structurally interconnected by a transversal member at the distal end, further comprising brazing a periphery of the transversal member interconnecting the sleeves to a corresponding periphery of the structural member interconnecting the arms.

<FIG> illustrates a gas turbine engine <NUM> of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan <NUM> through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases around the engine axis <NUM>, and a turbine section <NUM> for extracting energy from the combustion gases.

The compressor <NUM>, fan <NUM> and turbine <NUM> have rotating components which can be mounted on one or more shafts. Bearings <NUM> are used to provide smooth relative rotation between a shaft and casing (non-rotating component), and/or between two shafts which rotate at different speeds. An oil lubrication system <NUM> including an oil pump <NUM>, sometimes referred to as a main pump, and a network of conduits and nozzles <NUM>, is provided to feed the bearings <NUM> with oil. Seals <NUM> are used to delimit bearing cavities <NUM> and contain the oil. A scavenge system <NUM> having cavities <NUM>, conduits <NUM>, and one or more scavenge pumps <NUM>, is used to recover the oil from the bearing cavities <NUM>, which can be in the form of an oil foam at that stage. The oil pump <NUM> typically draws the oil from an oil reservoir <NUM>, and a heat exchanger <NUM>, can be used in the return line to cool the oil with air or another fluid such as fuel, for instance.

Generally, the heat exchanger <NUM> can have two fluid circuits distinct from one another from the point of view of fluid circulation (i.e. the fluids do not mix within the heat exchanger) and one or more region where the two fluid circuits are placed in thermal exchange contact with one another, meaning that during operation, heat from the hotter one of the circulating fluids is transferred to the colder one of the circulating fluids across some form of structure which separates the fluid circuits from one another. Both cross-flow and concurrent flow configurations are possible. In the cross-flow configuration, the first fluid circulates in a direction opposite the direction of the second fluid, whereas in the concurrent flow configuration both fluids circulate in the same orientation. Different ones of these configurations can be preferable in different embodiments, and the choice is left to the designer of a specific embodiment.

<FIG> presents a portion of an example heat exchanger <NUM> and more specifically a portion surrounding a heat transfer region <NUM>. As presented generally in <FIG>, the heat exchanger <NUM> includes at least three components : a first housing <NUM> having an arm <NUM>, a second housing <NUM> having a sleeve <NUM> having a hollow tube open at both ends and configured for receiving the arm <NUM>, and an adapter <NUM> configured for being secured to the tip of the arm <NUM>, also referred to as the proximal end <NUM> of the arm. The arm <NUM> has a first, internal, fluid path for conveying a first fluid along the heat transfer region <NUM>. In this embodiment, a second fluid path if formed internally to the sleeve <NUM>, and externally to the arm <NUM>, otherwise said between the structure/wall of the sleeve <NUM> and the structure of the arm <NUM>, when the heat exchanger <NUM> is in the assembled configuration, such as shown in <FIG>. Another adapter <NUM> can be integrated to the second housing <NUM>, in fluid flow communication with the hollow of the sleeve <NUM>/second fluid path. The first fluid path can form part of a first circuit including a first inlet and a first outlet (only one of which is shown in <FIG>, associated to the adapter <NUM>), whereas the second fluid path can form part of a second circuit including a second inlet and a second outlet (only one of which is shown in <FIG>, associated to the adapter <NUM>).

In this specification, the expression "proximal" will be used to refer to the region where the arm <NUM> protrudes from the sleeve <NUM>, and the expression "distal" can be used to refer to the other end <NUM> of the length of the arm <NUM>, to facilitate reference in the text below. Accordingly, the sleeve <NUM> can be said to have an internal cavity, or hollow, extending from a proximal opening at the proximal end, to a distal opening at the distal end, and configured to receive the arm therein.

In the illustrated embodiment, the proximal end <NUM> of the arm <NUM>, shown enlarged on <FIG>, can have a larger conduit portion, which will be referred to as a "mouth" <NUM> herein, which manifolds into a plurality of internal passages <NUM> to favor heat transfer efficiency with the other fluid. Similarly, the arm <NUM> has a generally cylindrical outer face <NUM> into which a number of circumferentially interspaced lengthwise-oriented grooves <NUM> are formed, creating a plurality of outer passages of the second fluid path in the heat transfer region <NUM>. This latter plurality of passages can be referred to herein as the outer passages, though it will be understood that they are internal to the sleeve <NUM>, and in fact partially defined by the sleeve <NUM>. In this embodiment, and perhaps as best seen in <FIG>, the grooves <NUM>/outer passages and many of the inner passages <NUM> (except the central one here) are circumferentially interspersed, which can be beneficial from the point of view of heat transfer efficiency.

Several reasons can motivate the use of an adapter <NUM> as a distinct component (see <FIG>) to be later assembled to the proximal end <NUM> of the arm <NUM> (see <FIG>). Indeed, in some embodiments, it can be preferred to manufacture the arm <NUM> by machining. In this case, one may need free lengthwise access to each one of the cross-sectional positions of the internal passages <NUM> from the proximal side of the arm <NUM>, to be able to drill each one of the internal passages along the length of the arm <NUM>. On the other hand, the adapter <NUM> can be provided with a port <NUM> and a coupler <NUM> which may prevent the desired access for the machining operation if it is not provided as a separate component to be later assembled. Moreover, in embodiments such as the one presented in <FIG>, the connector structure <NUM>, which can be required to satisfy fluid connection standards associated to the environment of use and/or for other considerations, may be transversally larger than the internal cross-sectional diameter of the sleeve <NUM>, and thereby prevent introduction of the arm <NUM> into the sleeve <NUM> if not provided as a separate component to be later assembled. Other restrictions specific to certain embodiments may also exist and motivate the use of an adapter as a distinct component.

When an adapter <NUM> is provided as a distinct component, the question arises as to how to establish a durable, reliable, low weight, low cost, leak-proof joint between the adapter <NUM> and the proximal end <NUM> of the arm <NUM>, and more specifically between the adapter <NUM> and the plurality of internal passages <NUM>. In some embodiments, not shown, it can be considered to use a plurality of distinct tubes to form the internal passages as opposed to machining. However, this may require forming individual weld joints between each end of each tube and some form of housing, which may not be satisfactory in some embodiments due to, for instance, the additional costs associated to the multiple weld joints including welding and inspection.

In an embodiment such as presented in <FIG>, it was preferred to establish the connection between the adapter <NUM> and the proximal end <NUM> of the arm with a single assembly step. In the illustrated, in addition to the individual internal passages <NUM> which can each individually be created along the length of the arm by drilling, a larger conduit portion which will be referred to as a mouth <NUM>, is also formed at the proximal end <NUM> of the arm <NUM>. The mouth <NUM> can also be machined by introducing a larger diameter machining tool into the proximal end <NUM> of the arm <NUM>, for instance. The mouth <NUM> can then manifold into the plurality of internal passages <NUM>. Moreover, outer passages <NUM> can be machined into the outer diameter <NUM> of the generally cylindrical geometry of the arm <NUM> by machining. In alternate embodiments, the cross-sectional shape of the arm can vary, and can be generally rectangular for instance, instead of circular.

In a cylindrical geometry, the mouth <NUM> can have a circular tip. The adapter can be provided with a first end <NUM> having generally the same geometry as the mouth <NUM>, such as, for this specific example, a cylindrical wall terminating at a circular tip (see cross-section of <FIG>), and the first end <NUM> of the adapter <NUM> can be welded to the circular tip of the mouth <NUM>. It will be understood, however, that in alternate embodiments, different approaches can be preferred, and it can be preferred to assemble the adapter to the proximal end of the arm by brazing, or even bolting flanges protruding transversally to the fluid path to one another, amongst other possible techniques.

As further shown in <FIG>, the second adapter <NUM> can be transversally oriented and lead into the cavity formed between the sleeve <NUM> and the arm <NUM>. In this embodiment, the diameter of the cylindrical geometry of the arm can be smaller than the internal diameter of the sleeve to provide a spacing <NUM> between the arm <NUM> and the sleeve <NUM> in which the second fluid can circulate circumferentially in addition to circulating lengthwisely along the grooves <NUM>.

<FIG> present a first complete example embodiment of a heat exchanger <NUM> integrating the concepts presented above, and which can be used, for instance, as an air/oil heat exchanger. In this embodiment, the first fluid circuit <NUM> and the second fluid circuit <NUM> are both generally U-shaped and are close to coinciding in the heat transfer regions <NUM>, <NUM>. Indeed, while maintaining distinct passages from the fluid-circulation point of view, two distinct heat exchange regions <NUM>, <NUM> are provided in which heat can be transferred from the first fluid to the second fluid at a relatively high rate, across the structure of two, corresponding arms <NUM>, <NUM> engaged with respective sleeves <NUM>, <NUM>.

Indeed, the first housing <NUM> generally includes a first arm <NUM> and a second arm <NUM>, which can each individually, generally be constructed such as the arm <NUM> presented above. Both arms <NUM>, <NUM> are parallel and structurally interconnected by a structural member which will be referred to herein as a base <NUM> which has a first cavity <NUM> formed therein. The cavity <NUM> can be fluidly connected to the internal passages of both arms <NUM>, <NUM>, and act as a mixing chamber during operation, to further favor heat exchange efficiency along the second arm <NUM>, such as best seen in <FIG>.

The heat exchanger <NUM> can further include both a first adapter <NUM> and a second adapter <NUM>, each one of the adapters being generally like adapter <NUM> and secured to the proximal end of a corresponding arm <NUM>, <NUM>.

The first fluid circuit <NUM> can thus extend from a port provided in the second adapter <NUM>, into a first inlet which can be in the form of a mouth <NUM>, can divide downstream of the mouth <NUM> into a first set of internal passages, recombine in the mixing chamber <NUM>, re-divide into a second set of internal passages extending along the second arm <NUM>, exit the internal passages into a first mouth <NUM> acting as a first outlet, and exit the heat exchanger <NUM> through a port in the first adapter <NUM>.

The two sleeves <NUM>, <NUM> can also be structurally interconnected by a transversal connecting segment <NUM>, which can alternately be referred to as a structural member, forming a distally-open channel in the second housing, the distally-open channel also fluidly connecting the hollows of the two sleeves <NUM>, <NUM>. A second mixing chamber <NUM> can be provided in the form of a spacing formed between the inner surface of the connecting segment <NUM> and the corresponding outer surface of the base <NUM>. Indeed, the base <NUM> and the channel can be configured for the distal opening of the channel to become closed by the base when in the assembled configuration such as shown in <FIG>.

The second fluid circuit <NUM> can extend from a port provided in a second inlet to communicate with the spacing formed between the first arm <NUM> and the first sleeve <NUM>, and the lengthwise outer passages formed in the first arm <NUM>, extend along the length of the first arm <NUM>, communicate with the second mixing chamber <NUM> and then with the spacing formed between the second arm <NUM> and the second sleeve <NUM>, extend along the length of the second arm <NUM>, and to a transversally-oriented second outlet and more specifically across a port thereof. The latter presents a concurrent-flow configuration. For establishing a cross-flow configuration, the second inlet and second outlet can be interchanged, for instance, or the first inlet and the first outlet can be interchanged.

The first cavity <NUM> can also be machined in the base by introducing a drilling tool transversally into the base, and the hole can then be closed by a plug <NUM>, which can be secured in place in a watertight fashion by brazing or welding for instance.

In an alternate embodiment shown in <FIG>, the first cavity <NUM> can be machined by milling a groove into the bottom of the base, for instance, and the groove can then be closed by capping, e.g. by welding a cap <NUM> onto the distal end of the base.

Returning to <FIG>, the proximal ends <NUM>, <NUM> of the arms <NUM>, <NUM> have an outer diameter designed to closely fit the internal diameter of the proximal ends of the sleeves <NUM>, <NUM> to form a close fit, and a watertight seal can be established between the corresponding peripheries by brazing, to name one example. Similarly, the connecting segment <NUM> of the second housing <NUM> and the base <NUM> of the first housing <NUM> can be shaped with a common periphery, allowing them to snugly engage and closely fit with one another, and a watertight seal can be established around the periphery by brazing, to name one example. In this example, the common periphery between the inner surface of the connecting segment <NUM> and the outer surface of the base <NUM> is obround, with two semi-circular features each at a corresponding transversal end, and a straight segment therebetween, though it will be understood that various other shapes can achieve a suitable result.

In this example, the adapters <NUM>, <NUM>, <NUM>, <NUM> are provided with a coupler <NUM>, which is configured for connecting with another component of the gas turbine engine. The coupler <NUM> has a broadened cross-section with a central aperture serving as a port, and two additional apertures. The coupler <NUM> can be configured to establish a watertight connection with a similar coupler feature of another device or conduit, and be secured to it by engaging bolts or the like into the two additional apertures, with a seal sandwiched between the abutting planar faces of the couplers.

<FIG> present a second complete example embodiment of a heat exchanger <NUM> integrating the concepts presented above. In this embodiment, the first and second fluid circuits <NUM>, <NUM> are both generally linear and generally coincide, though the second fluid circuit <NUM> may be said to have a widened U shape due to its transversally oriented inlet and outlet. Indeed, while maintaining distinct passages from the fluid-circulation point of view, a common heat exchange region <NUM> is provided in which heat can be transferred from the first fluid to the second fluid at a relatively high rate, across the structure of the arm.

The heat exchanger <NUM> can further include both a first adapter <NUM> and a second adapter <NUM>, the first adapter <NUM> being secured to the proximal end <NUM> of the arm <NUM>, and the second adapter <NUM> being secured to the distal end <NUM> of the arm <NUM>. In another embodiment, not shown, it can be preferred to include only a first adapter as an initially separate component later assembled to the arm, and to machine the second adapter integrally with the other machining operations performed on the arm, as even if the connector is wider than the internal cross-sectional area of the sleeve, the second adapter does not need to be engaged into the internal area of the sleeve at any time, only the proximal end of the arm is engaged at assembly, until it protrudes from the proximal end of the sleeve. However, in the illustrated embodiment, there was a challenge in forming an internal cavity similar to the mouth <NUM> to fluidly combine the individual flows of the internal passages, and for this reason, it was preferred to use a second adapter distinct from the initial structure of the arm, to form a second mouth <NUM>, and to later weld the second adapter <NUM> to the corresponding mouth <NUM>.

It was found that achieving multiple inner passages with low number of pieces can help in limiting the amount of weld/braze joints and thereby limit the number of NDT inspection points and potential failure points between circuits. It can provide satisfactory heat transfer efficiency by providing greater surface area between air and oil.

Claim 1:
A heat exchanger (<NUM>) comprising :
a first fluid circuit extending from a first inlet to a first outlet, at least one of the first inlet and the first outlet having a first mouth (<NUM>) dividing internally into a number of passages (<NUM>) within a periphery,
a second fluid circuit fluidly distinct from the first fluid circuit, extending from a second inlet to a second outlet, the second fluid circuit in thermal exchange contact with the number of passages (<NUM>) in a heat transfer region (<NUM>) of the heat exchanger (<NUM>), and
an adapter (<NUM>) having a second mouth secured to the first mouth (<NUM>) in a manner to establish internal fluid flow communication therewith,
wherein the first fluid circuit extends within a first housing (<NUM>), the first housing (<NUM>) having an arm (<NUM>) having a length extending from a proximal end (<NUM>) to a distal end (<NUM>), the mouth at the proximal end (<NUM>), and
the second fluid circuit extends between the first housing (<NUM>) and a second housing (<NUM>), the second housing (<NUM>) having a sleeve (<NUM>) configured for receiving the arm (<NUM>) of the first housing (<NUM>) therein into an assembled configuration,
characterized in that:
the proximal end (<NUM>) of the arm (<NUM>) protrudes from the sleeve (<NUM>) and receives the adapter (<NUM>), and the proximal end (<NUM>) of the arm (<NUM>) has an outer diameter designed to closely fit an internal diameter of the proximal end (<NUM>) of the sleeve (<NUM>) to form a close fit.