Patent Description:
Vehicles may generate and be subject to significant amounts of heat in operation. Cooling systems have been used to reduce the temperatures in parts of vehicles. These cooling systems may take the form of active systems, such as heat exchangers, or passive systems.

Heat exchangers are systems that are designed to transfer heat between two different media. Typically, there is a heat exchanging medium in the heat exchanger for transferring the heat from one region to another region. The heat exchanging medium may be solid or a fluid. Heat exchangers may be used for vehicles to provide active cooling to structure and/or equipment or remove heat from heat sensitive equipment.

There is a need to create an improved "active" skin cooling system for use with vehicles that generate and be subject to significant amounts of heat in operation.

According to a first aspect, there is provided a heat exchanger according to accompanying claim <NUM>.

In one example, the heat exchanger comprises an inlet port for receiving said fluid and an outlet port for allowing the fluid to exit the heat exchanger.

In one example, the inlet port is coupled to the first channel and the outlet port is coupled to the second channel.

The inlet port and the outlet port may be arranged at the proximal end of the set of channels. In other examples the inlet port is arranged at the proximal end of the set of channels and the outlet port is arranged at the distal end of the set of channels.

In one example, the set of channels comprises a third channel defined by the first skin and the wall, wherein the wall located between the second channel and the third channel comprises a second at least one aperture to allow fluid to pass through the wall from the second channel to the third channel.

The inlet port may be connected to the first channel at the proximal end of the set of channels and the outlet port may be connected to the third channel at the distal end of the set of channels. The second at least one aperture may be located towards the proximal end of the set of channels. The first at least one aperture may be towards the distal end of the set of channels.

The set of channels may follow a non-linear path between the proximal end and the distal end. The first channel and the second channel may be parallel curves relative to each other. The non-linear path may be substantially sinusoidal. The wall may be bonded to the first skin and the second skin. The inclined section may be inclined at an angle of approximately <NUM> to <NUM> degrees relative to the first longitudinal section and the second longitudinal section. The wall may have a thickness of between <NUM> and <NUM>. The first skin and the second skin may be formed of a titanium alloy.

According to another aspect not covered by the claims, there is provided a method of manufacturing a heat exchanger, wherein the heat exchanger is manufactured using diffusion bonding and superplastic forming.

It will be appreciated that relative terms such as top and bottom, upper and lower, and so on, are used merely for ease of reference to the Figures, and these terms are not limiting as such, and any two differing directions or positions and so on may be implemented.

<FIG> shows an illustrative example of a plan view of a heat exchanger <NUM>. In the example shown, the heat exchanger <NUM> comprises a set of channels <NUM>. There are six sets of channels <NUM> shown in the example in <FIG>, but in other examples, more or fewer than six sets of channels <NUM> may be used. The set of channels <NUM> has a proximal end <NUM> and a distal end <NUM>.

The set of channels <NUM> comprises a first channel <NUM> and a second channel <NUM>. The first channel <NUM> and the second channel <NUM> are fluidly coupled to allow fluid to pass from the first channel <NUM> to the second channel <NUM>.

The set of channels <NUM> are located between a first skin <NUM> and a second skin <NUM> of the heat exchanger <NUM>, which are shown in more detail in <FIG>.

In the example shown in <FIG>, in addition to the plurality of sets of channels <NUM> comprising the first channel <NUM> and the second channel <NUM>, there are also two isolated channels <NUM> that do not receive fluid. The isolated channels <NUM> are exterior channels that may act as static pressure vessels and are not subjected to fluid flow, in use. In this example, the two additional channels <NUM> are located towards the side of the heat exchanger <NUM> such that the set of channels <NUM> is located between the two additional channels <NUM>.

In the example shown in <FIG>, fluid may enter the heat exchanger <NUM> via one or more inlet ports <NUM> and exit the heat exchanger <NUM> via one or more outlet ports <NUM>. In other examples, fluid may enter the heat exchanger via an opening the in first skin or the second skin.

<FIG> shows that there may be one or more wall sections <NUM> separating the first channel <NUM> and the second channel <NUM> of each set of channels <NUM>. The wall sections <NUM> between the first channel <NUM> and the second channel <NUM> of the set of channels <NUM> may comprise one or more holes or apertures <NUM> to enable fluid to pass from the first channel <NUM> to the second channel <NUM>. The apertures are described in more detail in relation to <FIG>.

<FIG> shows a section view through the example of the heat exchanger <NUM> in <FIG> as taken along section markers A-A in <FIG>. <FIG> shows an example of the first skin <NUM> and the second skin <NUM> with the at least one of pair of channels <NUM> located between the first skin <NUM> and the second skin <NUM>.

In some examples, the first skin <NUM> is a lower skin located above the first channel <NUM> and the second channel <NUM> and the second skin <NUM> is an upper skin located below the first channel <NUM> and the second channel <NUM>. The first skin <NUM> and the second skin <NUM> are shown as being substantially planar in this example, but in other examples, the profile of the skin platen <NUM> and second skin <NUM> may not be planar and may be shaped so as to fit the shape of the apparatus that requires cooling.

In some examples, the wall <NUM> is a single continuous element that extends across and defines a plurality of sets of channels <NUM>. However, in the other examples, the wall <NUM> may comprise a plurality of discrete elements, with an element of the wall <NUM> located between adjacent first channels <NUM> and second channels <NUM>.

The wall <NUM> may have a shaped profile so as to define the plurality of first and second channels <NUM>, <NUM>, together with the first skin <NUM> and the second skin <NUM>, in the heat exchanger <NUM>. In one example, the wall <NUM> comprises a warren girder profile in cross-section, as shown in detail in <FIG> and <FIG>.

<FIG> shows a portion of an example of a wall <NUM> having a warren girder or corrugated profile in cross section. In this example, the wall <NUM> is a continuous element comprising a plurality of longitudinal sections <NUM>, <NUM> separated by a plurality of inclined sections or webs <NUM>, <NUM>. In this example, the plurality of longitudinal sections <NUM>, <NUM> are arranged along two planes such that alternate longitudinal sections <NUM>, <NUM> are arranged on different planes, i.e. a first longitudinal section <NUM> and a second longitudinal section <NUM> are arranged on different planes are connected by an inclined section <NUM>, <NUM>. A first set of alternating longitudinal sections <NUM> are arranged along a first plane and a second set of alternating longitudinal sections <NUM> are arranged along a second plane. The first set of alternating longitudinal sections <NUM> are coupled to or bonded with the first skin <NUM> and the second set of alternating longitudinal sections <NUM> are coupled to or bonded with the second skin <NUM>.

The wall <NUM> forms a repeating pattern of first longitudinal sections <NUM> and second longitudinal sections <NUM> connected by one or more inclined webs <NUM>, <NUM>. The wall <NUM> is corrugated and the at least one set of channels <NUM> are defined by a first platen <NUM>, a second platen <NUM> and the corrugated wall <NUM>.

<FIG> shows an example of a portion of the wall <NUM> between the first skin <NUM> and the second skin <NUM>. The first channel <NUM> is defined by the wall <NUM> and the first skin <NUM> and the second channel <NUM> is defined by the wall <NUM> and the second skin <NUM>. A first set of longitudinal sections <NUM> of the wall <NUM> are connected to or bonded with the second skin <NUM> and a second set of longitudinal sections <NUM> are connected to or bonded with the first platen <NUM>. In some examples, the angle of the inclined section or web <NUM>, <NUM> is approximately <NUM> degrees relative to the longitudinal sections <NUM>, <NUM> of the wall <NUM> and first skin <NUM> or second skin <NUM>. However, in other examples, the angle of the incline section <NUM>, <NUM> may range from approximately <NUM> degrees to approximately <NUM> degrees relative to the longitudinal sections <NUM>, <NUM> of the wall <NUM> and first skin <NUM> or second skin <NUM>. The geometry is applicable to DB/SPF manufacture as the angles result in manageable levels of superplastic strain in the wall <NUM>. A 30degree angle of the inclined section or web <NUM>, <NUM> would nominally result in an SPF strain of <NUM>% and a halving of original thickness in the horizontal plane prior to forming.

Forming a heat exchanger from only three layers, in this case the first skin <NUM>, the second skin <NUM> and the wall <NUM>, means that ultrasonic testing can be carried out on the heat exchanger <NUM> to check the heat exchanger has formed correctly. Further, ultrasonic testing can be used to test for any structural irregularities during the life of the heat exchanger.

As shown in <FIG>, as the first channel <NUM> is defined by a first skin <NUM> and a wall <NUM>; and the second channel <NUM> is defined by a second skin <NUM> and the wall <NUM>. For example, as shown in <FIG>, the first channel <NUM> is defined by the longitudinal section <NUM> and the inclined sections <NUM>, <NUM> of the wall <NUM> and the first skin <NUM>. Further, the second channel <NUM> is defined by the longitudinal section <NUM> and the inclined sections <NUM>, <NUM> of the wall <NUM> and the second skin <NUM>. As a result of this example, fluid passing through the first channel <NUM> has a large contact surface area with the first skin <NUM>. As such, if the first skin <NUM> is subject to the hot side of the heat exchanger <NUM> that requires cooling, then more of the heat can be absorbed by the fluid passing through the first channel <NUM>. The fluid will then pass through the first at least one aperture <NUM> in the wall <NUM> separating the first channel <NUM> and the second channel <NUM>. The second channel <NUM> has a large contact surface area with the second skin <NUM>. As a result, some of the heat may be transferred from the fluid to the second skin <NUM>, which may be at a lower temperature compared with the first skin <NUM> but with the intention that the cooling effect is high in channel <NUM> and that the higher proportion of the heat transferred from the first skin <NUM> will remain with the fluid as it then flows along the second channel <NUM> and is not transferred excessively into the cooler skin <NUM> but is instead transferred with the fluid as it exits the heat exchanger <NUM>. In one example, the fluid that exits the heat exchanger <NUM> may pass into a secondary heat exchanging device (e.g. a radiator or similar).

In one example, the first skin <NUM> and the second skin <NUM> each have a thickness of approximately <NUM> but in practice, any thickness may be considered depending on the application. The distance between the inside face of the first platen <NUM> and the inside face of the second platen may be approximately <NUM> but could be perhaps as much as <NUM>. The material thickness is designed to accommodate a pressure of approximately 20bar. The wall <NUM> may have a thickness of between about <NUM> and <NUM> depending on the application. For a ground-based cooling system where weight is not of consequence the wall <NUM> could be <NUM> thick. For an air vehicle a wall would more typically be between <NUM> and <NUM>. This web thickness therefore de-risked the manufacturing quality to add strength to the channels under working conditions.

In one example, the first channel <NUM> is suitable for receiving a coolant fluid via an inlet port <NUM>. The second channel <NUM> may be connected to an outlet port <NUM> for allowing the coolant fluid to leave the second channel <NUM>. In some examples, the inlet port <NUM> may be integrated with the first channel <NUM> and the outlet port <NUM> may be integrated with the second channel <NUM>. In other examples the inlet port <NUM> and the outlet port <NUM> may be plumbed using a pipe connector to the first channel <NUM> and the second channel <NUM>.

In one example the inlet port <NUM> is substantially cylindrical. The outlet port <NUM> may be substantially cylindrical. The substantially cylindrical inlet port <NUM> includes an inner diameter <NUM>, defining a hole <NUM>, and an outer diameter <NUM>. In one example, the inlet port has a hole <NUM> of approximately <NUM> and an outer diameter of approximately <NUM>.

The inlet port <NUM> provides a method for allowing a coolant fluid to transit from a source of fluid to the heat exchanger <NUM>. Due to the significant pressures in use in the heat exchanger <NUM>, associated pipework through which the coolant fluid is provided to the inlet port <NUM> may be welded to the interface of the inlet port <NUM>. To be able to weld the associated pipework to the inlet port <NUM>, an area around the welded location had to be created to accommodate the pipework, weld and associated heat generated during this process. These criteria generated the cross-sectional area required to securely support and manage the heat load during assembly.

In one example, the at least one inlet port <NUM> and the at least one outlet port <NUM> are alternately arranged at the proximal end <NUM> of the at least one set of channels <NUM>, such that an outlet port <NUM> is arranged in between two inlet ports <NUM>.

In the example shown in <FIG>, the inlet and outlet ports <NUM>, <NUM> are connected directly into the set of channels <NUM>. However, in other examples, the inlet ports <NUM> and outlet ports <NUM> are connected through the first skin <NUM> and/or second skin <NUM>.

In other examples, the set of channels <NUM> comprises a plurality of channels such that the fluid and the outlet port may be at either the proximal or distal end of the set of channels <NUM>. Alternatively, the inlet or outlet ports <NUM>, <NUM> may be arranged such that the fluid is transferred through the external platens or the ends of the channels.

<FIG> shows an example of one or more apertures <NUM> in the wall <NUM> between the first channel <NUM> and the second channel <NUM> of the set of channels <NUM>. In one example, the first channel <NUM> and the second channel <NUM> are fluidly coupled via the one or more apertures <NUM> located in the wall <NUM> between the first channel <NUM> and the second channel <NUM>. The one or more apertures <NUM> are formed in the inclined section <NUM> of the wall <NUM>. In <FIG>, the apertures <NUM> are shown as being circular shaped, but other shapes are envisaged.

In some examples, the one or more apertures <NUM> are arranged towards the distal end of the at least one set of channels <NUM>. In one example, there are a plurality of apertures <NUM> spaced at between <NUM> and <NUM> along the wall between the inlet channel and outlet channel, but other sizes are envisaged depending on the application of the heat exchanger.

The apertures may be of variable size depending on the required fluid transfer rates and pressures. Specifically, in the case where there is a plurality of apertures the apertures may optimally be smaller towards the proximal end and progressively increase in size towards the distal so as to ensure that each aperture permits the desired share of the total flow to pass. In one example, the apertures will be made circular at the stage of manufacturing the wall <NUM> (or core sheet) in the DB/SPF process, but the effect of superplastic forming will then cause the circular form to be uniaxially extended to an ellipse shape. Alternatively, an elliptical hole with the major axis transverse to the superplastic strain direction such that a circular final hole form will result after forming. The thickness of the material at the location where the gas transfer holes are introduced may also be of additional thickness in order that the tendency for local thinning due to superplastic straining is counteracted.

One method of manufacturing the heat exchanger is using a DB/SPF process. The apertures <NUM> will be "gas transfer holes" introduced in the core pack by simple hole drilling of the core sheet (which results in the wall <NUM> in the heat exchanger <NUM>) at the detail manufacturing stage and before the application of stop-off compound to locally prevent the diffusion bonding of sheets so as to facilitate the subsequent formation of three dimensional structure by superplastic inflation of the core pack within an SPF tool cavity. There are various techniques to manage the apertures <NUM> so as to avoid excessive elongation during SPF. In the example of the heat exchanger <NUM> being used with an air vehicle, avoiding excessive elongation could be important as the core sheet will be as thin as possible for light weighting reasons. For ground-based systems the core thickness may be substantial and strain around the holes should not be excessive. The DB stage can cause the first platen <NUM> to form into the hole in the core sheet, which forms the wall <NUM>, and then seal the hole and potentially diffusion bond together (noting that the area has a layer of stop-off applied).

The example of <FIG> also shows an example of a chamfer located at the distal end of the heat exchanger <NUM>. In one example, the chamfer is angled between <NUM> to <NUM> degrees, more particularly between <NUM> degrees and <NUM> degrees. The chamfer may result from the build orientation of Selective Laser Melting manufacturing, which may be used to manufacture the heat exchanger <NUM>. The heat exchanger may be built in the vertical direction upwards. The nature of this build orientation provides a self-supporting method of manufacture which is optimised at <NUM> degrees.

<FIG> shows an example of an elevation B-B as indicated by markers B-B in <FIG>. In this example, the inlet ports <NUM> and the outlet ports <NUM> are arranged in an alternating nature at the proximal end <NUM> of the at least one set of channels <NUM>. For conciseness, not all of the inlet ports <NUM> and outlet ports <NUM> have been indicated with reference signs. Further, the centre line through the inlet ports <NUM> may be offset from a centre line of the outlet ports <NUM> by approximately <NUM>.

Referring to <FIG>, there is shown a plan cross-sectional view of the heat exchanger <NUM>. The arrows in <FIG> indicate the flow of fluid, such as coolant fluid, into the first channel <NUM>, through the at least one aperture <NUM> in the wall <NUM>, and out of the second channel <NUM> via an inlet port <NUM> and the outlet port <NUM> respectively. Note that for conciseness, not all inlet ports <NUM> and outlet ports <NUM> include arrows indicating fluid flow. However, in practise, each of the inlet ports <NUM> may receive a fluid flow and each of the outlet ports <NUM> may eject the fluid. In this example, the apertures <NUM> located towards the distal end of the set of channels <NUM>, i.e. towards the opposite end of the set of channels <NUM> from the inlet port <NUM>. In the example shown in <FIG>, there are five apertures <NUM> shown in the wall <NUM> between the first channel <NUM> and the second channel <NUM>. However, in other examples, there may be more or fewer than five apertures <NUM> between each wall <NUM> separating the first channel <NUM> and the second channel <NUM> of the set of channels <NUM>.

As can be seen in <FIG>, each set of channels <NUM> is separated by a section of wall <NUM> that does not contain an aperture. Therefore, each set of channels <NUM> is fluidly isolated from the other sets of channels <NUM>.

In one example, as fluid enters that heat exchanger <NUM> via the inlet port <NUM>, it travels along the first channel <NUM> from the proximal end of the set of channels <NUM> towards the distal end of the set of channels channel <NUM>. The apertures in the wall <NUM> between the first channel <NUM> and the second channel <NUM> enable the fluid to pass through the wall <NUM> comprising the apertures <NUM>.

Once the fluid has passed to the second channel <NUM>, it moves from the distal end of the set of channels <NUM> to proximal end of the set of channels <NUM>, i.e. the part of the second channel <NUM> that is adjacent to the outlet port <NUM>. The fluid then exits the heat exchanger <NUM> via the outlet port <NUM>.

In one example a boundary wall <NUM> bounds the heat exchanger <NUM> such that as the fluid approaches the extreme distal end of the first channel <NUM>, any fluid that has not already passed through the one or more apertures <NUM> will impinge upon the boundary wall <NUM> and then pass through the one or more apertures <NUM>, for example, the most distal aperture <NUM>.

<FIG> shows an alternative example of a part of a heat exchanger <NUM>. The heat exchanger <NUM> may have a different arrangement of apertures <NUM>, inlet ports <NUM> and outlet ports <NUM> such that the fluid may take a different path through the heat exchanger <NUM>. For example, as shown in <FIG>, the fluid may enter the first channel <NUM> at the proximal end <NUM> of the set of channels <NUM> and pass through a section of the first channel <NUM>. The fluid may then pass through the at least one aperture <NUM> in the wall <NUM> located between the first channel <NUM> and the second channel <NUM>. In this example, the fluid will then continue in substantially the same direction from the proximal end <NUM> to the distal end <NUM> of the set of channels <NUM> along the second channel <NUM> and exit the second channel <NUM> at the distal end <NUM> of the set of channel <NUM>. In this example, the fluid effectively travels from the proximal end <NUM> to the distal end <NUM> of the set of channels <NUM> without turning back on itself. The inlet port <NUM> may be coupled with the first channel <NUM> at the proximal end <NUM> of the set of channels <NUM> and the outlet port <NUM> may be coupled with the second channel <NUM> of the set of channels <NUM> at the distal end <NUM> of the set of channels <NUM>.

<FIG> shows an alternative example of a part of the heat exchanger <NUM>. In this example, the set of channels <NUM> comprises a first channel <NUM>, a second channel <NUM> and a third channel <NUM>. The third channel <NUM> is defined by the first skin <NUM> and the wall <NUM>. The wall <NUM> located between the second channel <NUM> and the third channel <NUM> comprises a second at least one aperture <NUM> to allow fluid to pass through the wall <NUM> from the second channel <NUM> to the third channel <NUM>. The heat exchanger <NUM> may have a different arrangement of apertures <NUM>, inlet ports <NUM> and outlet ports <NUM> such that the fluid may take a different path through the heat exchanger <NUM>. For example, as shown in <FIG>, the fluid may enter the first channel <NUM> at the proximal end <NUM> of the set of channels <NUM> and pass through a section of the first channel <NUM>. The fluid may then pass through the at least one aperture <NUM> in the wall <NUM> located between the first channel <NUM> and the second channel <NUM>. In one example, the at least one aperture <NUM> between the first channel <NUM> and the second channel <NUM> of the set of channels <NUM> is located towards the distal end <NUM> of the set of channels <NUM>. In this example, the fluid will then impinge on an end wall and travel along the second channel <NUM> from the distal end <NUM> to the proximal end <NUM> of the heat exchanger <NUM>. The fluid may then pass through the one or more apertures <NUM> located between the second channel <NUM> and a third channel <NUM>. In one example, the at least one aperture <NUM> located between the second channel <NUM> and the third channel <NUM> may be located toward the proximal end <NUM> of the set of channels <NUM>. In this example, the fluid will then travel from the proximal end <NUM> to the distal end <NUM> along the third channel <NUM> and exit through the heat exchanger <NUM> at an outlet port <NUM>.

In other examples, the set of channels <NUM> may include a fourth channel (not shown) and the fluid may pass through at least one aperture in a wall located between the third channel <NUM> and the further channel and then reverse in direction again. The fluid may travel to the other end of the heat exchanger and exit through an outlet port <NUM>.

In one example, the fluid may follow a substantially linear path as it flows in the channels, i.e. the walls <NUM> of the channels are straight. However, in other examples, as shown in <FIG>, the set of channels <NUM> may follow a non-linear path, i.e. the first channels <NUM> are non-linear as they extends from right to left in <FIG> and the second channels <NUM> are non-linear as they extend from left to right in <FIG>. The non-linear path of the inlet channel <NUM> and the outlet channel <NUM> introduces a turbulence to the fluid flow, which is required to follow a non-linear path through the first channel <NUM> and the second channel <NUM>. In other words, the set of channels <NUM> may have a non-linear path.

As shown in <FIG>, the inlet channel <NUM> and the outlet channel <NUM> may comprise parallel curves relative to each other. In other words, the inlet channel <NUM> and the outlet channel <NUM> are substantially the same shape, but are translated relative to each other.

The manufacturing method of DB/SPF is capable of making non-linear channels simply through the adoption of a stop-off pattern of suitable geometry. Conversely, linear channels may also be formed.

As shown in <FIG>, the fluid follows a substantially meandering path as it travels through the first channel <NUM> and the second channel <NUM>. In other words, the fluid may follow a non-linear path in the heat exchanger <NUM>. <FIG> shows an example of the detail of the path of the first channel <NUM> and the second channel <NUM> in more detail. In the example shown in <FIG>, the first channels <NUM> and second channels <NUM> follow a substantially sinusoidal path, defined by substantially sinusoidal walls <NUM>. In this example, the wall <NUM> is corrugated in a first direction to form a plurality of sets of channels <NUM> and non-linear in a second direction such that the plurality of sets of channels <NUM> are non-linear.

The non-linear or meandering path followed by the walls <NUM> (and hence the set of channels <NUM>) creates a turbulent fluid path for the coolant fluid to increase heat transfer of the heat exchanger <NUM>. The turbulent fluid flow is more efficient for heat transfer compared with the laminar fluid flow because effectively, in laminar flow, fluid is moving in distinct streamlines. That means that the heat transfer is from one "layer" of the fluid to a cooler one, essentially by heat conduction. In contrast, in turbulent flow the fluid particles are not moving along streamlines but are mixing from one layer to others, which means that there is physical transport of fluid from higher to lower temperatures and vice versa, which significantly increases the heat transfer.

The non-linear or meandering path followed by the first channel <NUM> and the second channel <NUM> increases the turbulence in the fluid flow by preventing or reducing the formation of laminar layers of fluid. As such, the heat exchanger works <NUM> to effectively remove heat from a region on one side of the heat exchanger <NUM>, for example, from the region adjacent the first skin <NUM> and transferred via the heat exchanger <NUM> to the region adjacent the second skin <NUM>.

In one example, the coolant fluid used with the heat exchanger <NUM> is Argon. However, for a light-weight application, a liquid phase coolant would run at a much lower operating pressure and so have less penalty in terms of structural weight. In one example the liquid phase coolant is Syltherm <NUM> heat transfer fluid. The use of Syltherm <NUM> heat transfer fluid enables the pressure in the heat exchanger to be substantially reduced.

In the example shown in <FIG>, there are two additional channels <NUM> located towards the edges or sides of the heat exchanger <NUM>. These additional channels <NUM> may or may not be associated with a port to enable a fluid to be received in the additional channels <NUM>. These outer additional channels <NUM> may be the result of the manufacturing method, which requires additional space around the at least one plurality of pairs of channels <NUM>. These outer channels <NUM> do not form an active part of the heat exchanger <NUM>.

In one example, the plurality of channels <NUM> are made from three sheets of material formed into a tool cavity, i.e. the first skin <NUM>, the second skin <NUM> and the wall <NUM>. In one example, the first skin <NUM>, the second skin <NUM> and the wall <NUM> is a titanium diffusion bonded titanium alloy, such as Ti-6Al-4V, as this has excellent creep performance at a desired operating temperature, for example <NUM> degrees Celsius, of the heat exchanger <NUM>, allowing a high skin temperature. A temperature of <NUM> degrees Celsius represents the region of stagnated flow around leading edge aircraft skins for hypersonic flight, at the set test conditions. The titanium alloy material, therefore reducing load on cooling system solution. Further, Ti-6Al-4V retains its material strength under the high temperature conditions. In addition, Ti-6Al-4V is also compatible with the Diffusion Bonding and Superplastic Forming method, which may be used for the manufacture of the heat exchanger <NUM>.

DB/SPF (Diffusion Bonding and Superplastic Forming) is a process for the economic production of three-dimensional objects and sandwich structures. One characteristic of DB/SPF is an extremely high level of formability. A separating agent or "stop-off", such as yttria is placed on defined areas between material sheets, such as titanium alloys. In the example shown in <FIG>, the stop-off <NUM> is applied to the sections of the first skin <NUM> and the second skin <NUM> at the flat-sheet details stage prior to assembly of the sheets for diffusion bonding. This then results in sections of the wall <NUM> being unbonded in the final product. In contrast, the areas of the first skin <NUM> and the second skin <NUM> in which the stop-off material <NUM> is not applied results in a diffusion bond between the wall <NUM> and the first skin <NUM> and the second skin <NUM> in the finished product <NUM>. Once the stop-off has been applied to the relevant internal sections of the first skin <NUM> and the second skin <NUM>, temperatures of over <NUM> and pressure are applied and the unmasked areas are bonded by Diffusion Bonding. In the example shown in <FIG>, the first set of alternating longitudinal sections <NUM> of the wall <NUM> are bonded to the second skin <NUM> and the second set of alternating longitudinal sections <NUM> of the wall <NUM> are bonded to the first skin <NUM>. The sections of the first skin <NUM> and the second skin <NUM> to which the stop-off <NUM> is applied are not bonded to the wall <NUM>. This technique provides broad freedom for an operator to produce geometry of the heat exchanger <NUM> to suit the design. The diffusion bonded "flat-pack" so produced is assembled in a Superplastic Forming tool and with a means of introducing argon gas for the purposes of inflating the structure so as to cause the skin sheets to form outwards into an internal die mould tool and in so doing cause the internal walls <NUM> to be stretched from their initial horizontal planar aspect into inclined angular walls <NUM>. The holes <NUM> that are subsequently to be used for the transfer of fluid between the channels may conveniently be used to facilitate the transfer of forming gas across the heat exchanger during the SPF part of the manufacturing process. The pressurised forming gas itself may be introduced through the same ports as will subsequently be used for the entry and exit of the heat exchanger media.

The SPF/DB process enables the production of thin-walled but rigid designs. The process is governed by specifically developed SPF-parameters and an advanced tooling concept in which the thickness of the panel is controlled as required. This method conforms to the best replication of the actual environment to which the heat exchanger <NUM> would be exposed.

A test has been conducted to determine the heat transfer by the heat exchanger <NUM>. A John Shaw <NUM> Tonne press may be arranged with a first platen and second platen areas with a fixed base and a moving upper "slide" operated from a central singular double-acting hydraulic cylinder able to open and close the press and apply a closure force of up to <NUM> Tonnes. In one example, the first platen and the second platen is made up of five individual segments running left to right and with each segment further sub-divided into three zones front to rear.

Hence, in this example, each platen (first and second platens) comprises <NUM>-off individual temperature control zones (<NUM> in total). In this example the platen area is <NUM> x <NUM> with an effective heated area of <NUM> x <NUM>, where temperature is controlled to within ±<NUM>. The heater power is nominally set at <NUM>. 5W/cm<NUM> per platen surface. The platens are heated by embedded electric cartridge elements with each zone controlled via a pair of thermocouples also embedded within each zone of the platen body. The press displays the set point temperature and actual temperature of each individual platen zone together with the percentage of maximum power being input to each zone.

The press has three independent argon gas pressure lines. Gas pressures of up to ~<NUM> psi (<NUM> Bar) may be applied on each gas line using Tescom gas control valves. Each gas line has a gas flow meter to record flow, as well as pressure monitoring gauges. The SPF-DB tooling is maintained in a closed position using tonnage that is modulated based on the pressure applied and the plan view area that the gas pressure is applied over together with an over-arching "seal force" that maintains a programmable net closure force regardless of pressure. The "hot zone" of the press is closed via vertically moving front and rear access doors and non-moving side panels that provide a blast-proof working zone capable of withstanding an un-contained rupture of the component. However, unanticipated movement of the upper slide structure due to inadequate hydraulic force would also provide automatic cycle abort to vent the working pressure.

A description of the testing of the heat exchanger <NUM> is described below. The test was conducted by:.

During the initial phase of the experiment the coolant gas was incrementally increased to the following flow rates: <NUM>, <NUM> & <NUM> Standard Litres Per Minute. In order to maintain the desired pressure in the system it was necessary to increase the demanded pressure from the Argon farm from <NUM> bar (300psi) to <NUM> bar (350psi). At each of the flow rates it was necessary to adjust the throttle valve to balance the flow and pressure in the system. The first platen <NUM> may be subject to a temperature of approximately <NUM> degrees Celsius in use.

Heaters were used to simulate temperatures that the first skin <NUM> and the second skin <NUM> may experience in use. The test was to expose the heat exchanger <NUM> to a representative environment of a hypersonic flight envelope (thermodynamic only) as indicated below. Note that each number in the table represents a corresponding plan view area of the first platen and the second platen respectively.

Test runs of at least <NUM> minutes were completed at the nominal condition (<NUM> Standard Litres Per Minute, <NUM> barg, approximately <NUM> inlet temperature for the coolant fluid entering the inlet ports <NUM>), and the two flow rate variations of <NUM> Standard Litres Per Minute and <NUM> Standard Litres Per Minute (SLPM).

In this test example, the coolant fluid was Argon gas. At 440SLPM there was a temperature increase of the coolant fluid between the inlet port <NUM> and the outlet port <NUM> of just less than <NUM>, which demonstrates that the tested heat exchanger <NUM> is capable of drawing thermal energy imparted by press platen into the coolant fluid while maintaining an acceptable temperature of the structure of the heat exchanger. The coolant fluid outlet temperature is approximately <NUM>.

Utilising the gas temperature and pressure it is possible to determine the thermodynamic and transfer properties of the coolant fluid, in particular the specific heat at constant pressure (Cp), with which when combined with the mass flow rate (m) and change in gas temperature across the test article (ΔT) it is possible to calculate the heat transferred into the gas (Q). In both cases for 440SLPM there was approximately <NUM>. 49kW transferred into the gas stream.

The test was run again at 420SLPM. The runs were conducted as follows:.

At 420SLPM there was a temperature increase of the coolant fluid between the inlet port <NUM> and the outlet port <NUM> of just under <NUM>, and approximately <NUM> less than at 440SLPM. This clearly demonstrates that the heat exchanger <NUM> is capable of drawing thermal energy imparted by press platen into the gas stream while exhibiting a small difference to the 440SLPM runs.

Utilising the gas temperature and pressure it is possible to determine the thermodynamic and transfer properties of the Argon gas. With which when combined with the flow rate and change in gas temperature across the test article it is possible to calculate the heat transferred into the gas. In both cases for 420SLPM there was approximately <NUM>. 46kW transferred into the gas stream. This is approximately <NUM>. 03kW less than at 440SLPM.

The test was run again at 400SLPM. The runs were conducted as follows:.

At 400SLPM there was a temperature increase of the coolant fluid between the inlet port <NUM> and the outlet port <NUM> of just less than <NUM>, and approximately a further <NUM> less than at 420SLPM. This clearly demonstrates that the heat exchanger was capable of drawing thermal energy imparted by press platen into the gas stream while exhibiting a small difference to the 420SLPM runs. Additionally this supports the trend of a reduction of 20SLPM resulting in a <NUM> decrease in the gas temperature difference across the heat exchanger.

Utilising the gas temperature and pressure it is possible to determine the thermodynamic and transfer properties of the coolant fluid. With which when combined with the flow rate and change in gas temperature across the test article it is possible to calculate the heat transferred into the gas. In both cases for 400SLPM there was approximately <NUM>. 43kW transferred into the gas stream. This is approximately <NUM>. 03kW less than at 420SLPM and approximately <NUM>. 06kW less than at 440SLPM.

Based on the initial calculations of the heat transfer into the gas flow a linear relationship to the mass flow is evident.

The table below is a Summary of Heat Transfer Calculated for Various Flow Rates:.

<FIG> shows an example of the relationship between heat transfer and mass flow rate. As can be seen from <FIG>, the heat transfer to the coolant fluid follows a linear relationship dependent upon mass flow.

Claim 1:
A heat exchanger (<NUM>) for an aircraft skin, the heat exchanger comprising a plurality of sets of channels (<NUM>) having a proximal end and a distal end, each of the sets of channels comprising:
a first channel (<NUM>) defined by a first skin (<NUM>) and a wall (<NUM>); and
a second channel (<NUM>) defined by a second skin (<NUM>) and the wall (<NUM>), wherein:
the wall (<NUM>) is a continuous corrugated element comprising a plurality of first longitudinal sections (<NUM>) coupled to the first skin (<NUM>) and a plurality of second longitudinal sections (<NUM>) coupled to the second skin (<NUM>);
the first and second longitudinal sections (<NUM>, <NUM>) are connected in a repeating pattern by a plurality of inclined sections (<NUM>, <NUM>);
the inclined section (<NUM>) located between the first channel (<NUM>) and the second channel (<NUM>) of each respective set of channels (<NUM>) comprises at least one aperture (<NUM>) to allow fluid to pass through the inclined section (<NUM>) from the first channel to the second channel; and,
each set of channels (<NUM>) is separated by a section of a wall (<NUM>) that does not contain an aperture such that each set of channels (<NUM>) is fluidly isolated from the other sets of channels.