Thermal management apparatus and method

Abstract

An apparatus, comprising a component, comprising a plurality of physically distinct units arranged in a castellated structure; and a heat pipe, comprising: a first portion, each unit of the plurality of physically distinct units being affixed to and in thermal contact with the first portion; and a second portion configured to be operatively coupled to a heat exchanger.

Description

[0001] THERMAL MANAGEMENT APPARATUS AND METHOD

[0002] Field of the Invention

[0003] The present invention relates to a thermal management apparatus, system, method and power generation method.

[0004] Background

[0005] Heat pipes are passive heat transfer devices that employ a phase transition of a working fluid to convey thermal energy from an evaporator portion to a condenser portion of the heat pipe, when subject to a temperature difference.

[0006] Broadly, there are two categories of heat pipe: those that contain a wick (mainly capillary driven but can be gravity assisted) and those that do not (i.e., are wickless and are driven by other forces, such as gravity). Examples of wick-containing heat pipes include vapour chamber and variable or constant conductance heat pipes. Examples of wickless heat pipes include thermosiphons and oscillating heat pipes.

[0007] Figure 1 is a schematic illustration of a cross-section of a heat pipe 100, containing a wick 108. The heat pipe 100 includes an envelope 102, which is closed at each of its ends. The envelope comprises or defines an elongate channel 104 that sealingly contains a charge 106. The elongate channel 104 is illustrated in Figure 1 as being straight, but it will be understood that it can also be bent or curved. For a constant conductance heat pipe, the charge consists of a working fluid (i.e., a working liquid and the vapour of the working liquid), when in use. Below the freezing point of the working liquid, the charge in a constant conductance heat pipe is a solid. The heat pipe also includes a wick structure 108 at the envelope through which the working liquid can travel via capillary action. Example wick structures include metallic meshes or sintered powders. The wick structure can be integral to, or separate from, the envelope.

[0008] It will be understood that the term “heat pipe” is not limited to tubular designs only; heat pipes can have other external shapes, such as planar designs that are typical of vapour chambers. In planar designs, the envelope defines or comprises an “elongate” channel in the sense that the dimension of the channel in a direction between (or connecting)

[0009] 38306813-1opposing sides of the wick is much smaller than the dimension of the channel in any direction perpendicular thereto.

[0010] Figure 2 is a schematic illustration of a plan view of an alternative heat pipe 200, absent a wick. The heat pipe is an oscillating heat pipe. The heat pipe 200 includes an envelope 202, which is closed at each of its ends. The envelope comprises or defines an elongate channel 204 that sealingly contains a charge 206. As above, in use, the charge consists of a working liquid and the vapour of the working liquid. The elongate channel may be defined by grooves carved into top and / or bottom portions of the envelope, which are aligned and joined together during assembly. The elongate channel may form a closed loop or an open loop shape.

[0011] The elongate channel 204 is sized (i.e. , sufficiently narrow) so that, after charging the elongate channel with the working fluid, the working fluid is separated into a plurality of spatially alternating liquid 206a and vapour “slugs” 206b. That is, each liquid slug remains serially adjacent to two vapour slugs and each vapour slug remains serially adjacent to two liquid slugs along the elongate channel. As shown, the elongate channel 204 comprises one or more serpentine or II- bends 208.

[0012] In general, for any heat pipe design, working fluid is contained and sealed within the heat pipe. As noted above, below the freezing point, the charge is a solid (i.e., the liquid-gas two-phase mixture is absent below the freezing point). At any given temperature above the freezing point of the working fluid, the working fluid consists of a mixture of its liquid and its vapour (herein “working liquid” and “working vapour”). At thermodynamic equilibrium, the internal pressure of the heat pipe is the saturation pressure of the working fluid (i.e., the working vapour pressure) at the corresponding working fluid temperature.

[0013] If the heat pipe is subject to a temperature perturbation, the fraction of the working liquid and working vapour in the mixture will adjust to achieve equilibrium. For example, if the temperature of the working fluid increases, the fraction of the working fluid that is a vapour will increase, whereas, if the temperature of the working fluid decreases, the fraction of the working fluid that is a vapour will decrease. The internal pressure of the heat pipe adjusts in accordance with a saturation curve.

[0014] 38306813-1A pressure-temperature phase diagram of a typical working fluid for a heat pipe is shown in Figure 3. The y-axis is pressure; the x-axis is temperature. The boundary between the liquid and vapour phase regions (denoted in the Figure by L and V, respectively) is the saturation curve.

[0015] Referring to Figure 1, if a temperature difference exists across the heat pipe 100 (e.g., there is a “hot” end and a “cold” end), working liquid is caused to vaporise at the “hot” end and caused to flow towards the “cold” end, which is at a lower temperature and pressure (see the saturation curve from Figure 3). At the “cold” end, the vapour condenses back into a liquid. As a result, thermal energy is conveyed from the “hot” to the “cold” end of the heat pipe by the latent heat carried and released by the working vapour. The working liquid is drawn back to the hot end of the heat pipe through the wick by capillary action. In thermosiphons (a type of wickless heat pipe), the heat pipe is oriented so that gravity urges the condensed working liquid back to the hot end of the heat pipe. The working liquid then vaporises at the hot end of the heat pipe and the process repeats. For this reason, the “hot end” and “cold end” of the heat pipe are often referred to as the evaporator and condenser portions of the heat pipe, respectively.

[0016] Referring to Figure 2, if a temperature difference exists across the heat pipe 200 (e.g., there is a “hot” side and a “cold” side), liquid slugs at the hot side shrink in volume due to the phase change and the pressure of their adjacent gas slugs increases. At least initially, this drives flow of the slugs through the elongate channel away from the “hot” side and to the “cold” side of the heat pipe, where condensation takes place. At the cold side, liquid slugs grow in volume at the expense of their adjacent gas slugs. After a period of time, oscillatory heat pipes are characterised by an oscillatory motion of the slugs, switching between flowing from “hot-to-cold” and then from “cold-to-hot”. This oscillatory motion conveys thermal energy from the evaporator to the condenser side of the heat pipe. The energy is transported via both latent and sensible heat.

[0017] Variable conductance heat pipes, VCHs, are also known. In variable conductance heat pipes, the heat pipe sealingly contains a charge, consisting of a non-condensable gas, NCG, in addition to the working fluid. Below the freezing point of the working fluid, the heat pipe contains the NCG and the working fluid in its solid form. In use, the NCG resides at a reservoir located at the condenser portion of the heat pipe. If the cooling rate is too large, the vapour pressure at the condenser portion drops and the VCH is allowed

[0018] 38306813-1to expand to reduce the size of the condenser portion and hence reduce cooling. Likewise, if the cooling rate is too small, the vapour pressure at the condenser portion increases and the VCH is compressed to increase the condenser size (up to a maximum size).

[0019] Summary of the Invention

[0020] Aspects of the present invention provide an apparatus, a plasma confinement device, a system, a thermal management method, and a power generation method as set out by the appended set of claims.

[0021] According to a first aspect of the present invention, there is provided an apparatus. The apparatus comprises: a component, comprising a plurality of physically distinct units arranged in a castellated structure; and a heat pipe. The heat pipe comprises a first portion, each unit of the plurality of physically distinct units being affixed to and in thermal contact with the first portion; and a second portion configured to be operatively coupled to a heat exchanger.

[0022] In some examples, all of said units are substantially similar to one another in form.

[0023] In some examples, the first portion has a first surface area and the second portion has a second surface area, the second surface area being greater than the first surface area. The second surface area may be greater than the first surface area by a factor of at least 2.

[0024] The second portion may comprise a plurality of cooling fins or baffles. Each cooling fin or baffle may be at least partially embedded within the heat pipe.

[0025] The plurality of physically distinct units comprises ten or more units, or even thirty or more units.

[0026] A melting point of the component, at 0.1 MPa, may be greater than 1100°C.

[0027] A main constituent of a material of the component may be a metallic element, with an atomic number greater than or equal to 40.

[0028] 38306813-1The component may comprise or consist of a refractory metal (e.g., tungsten) or an alloy of a refractory metal (e.g., a tungsten alloy).

[0029] The heat pipe may be operative at temperatures in excess of 200°C.

[0030] In some examples, a portion of the first portion of the heat pipe is at least partially embedded in the castellated structure.

[0031] The first portion of the heat pipe may pass through each unit of the plurality of physically distinct units.

[0032] In some examples, the heat pipe has an elongate channel and the second portion of the heat pipe includes a longitudinal end portion of the elongate channel.

[0033] The heat pipe and / or the channel may follow a contour of a smooth external surface of the component.

[0034] In some examples, the apparatus comprises one or more heat exchangers operatively coupled to the second portion of the heat pipe. For example, the apparatus may comprise a first heat exchanger operatively coupled to a first longitudinal end portion of the elongate channel and a second heat exchanger operatively coupled to a second longitudinal end portion of the elongate channel.

[0035] The component may be or have a castellated armour.

[0036] In some examples, said units are arranged in a rectilinear array. The rectilinear array may be any one of: a rectangular array, a square array, a hexagonal array, or a triangular array.

[0037] In some examples, the heat pipe comprises a manifold section. The manifold section may be arranged adjacent to the second portion of the heat pipe.

[0038] In some examples, the plurality of physically distinct units of the component comprises a plurality of sets of such units, each set comprising a plurality of physically distinct units arranged in a castellated structure; and the apparatus comprises a plurality of heat pipes,

[0039] 38306813-1each heat pipe being associated with a respective one of the sets of units, each heat pipe comprising a first portion and a second portion, each unit of the respective associated set being affixed to and in thermal contact with said first portion, and said second portion of each heat pipe being configured to be operatively coupled to a heat exchanger. Optionally, the heat pipes of the plurality are arranged in an array, each heat pipe forming at least a portion of a row or column of said array.

[0040] In some examples, the apparatus comprises a heat exchanger, each heat pipe being operatively coupled to the heat exchanger at the second portion of said heat pipe.

[0041] In some examples, the apparatus comprises a plurality of heat exchangers, wherein each heat pipe is operatively coupled to at least one of the plurality of heat exchangers at a respective second portion of said heat pipe.

[0042] The or each heat pipe may have a working fluid comprising: water, or, any one of lithium, sodium, potassium, a sodium-potassium alloy, caesium, or any mixture of the foregoing metals.

[0043] In some examples, the or each heat pipe is affixed to the component by an interlayer; the or each heat pipe has an envelope comprising a first material having a first coefficient of thermal expansion, CTE; the component comprises a second material having a second CTE; and the interlayer comprises at least one material having a CTE intermediate between the first and second CTEs. The CTE may be measured under standard conditions and / or at operating temperature.

[0044] According to a second aspect of the present invention, there is provided a plasma confinement device, comprising the apparatus according to the first aspect. The component of the apparatus comprises the plurality of physically distinct units arranged in a castellated structure is a component of the plasma confinement device.

[0045] The component may be any of: a shielding layer for the plasma confinement device; a plasma facing component; a divertor; a limiter; a first wall component; a breeder blanket; a portion of any of the foregoing; an armour for any of the foregoing or for a portion thereof; or a thermal management component for any of the foregoing.

[0046] 38306813-1The plasma confinement device may be any of: a magnetic confinement device; a tokamak; a stellarator; a spheromak; a spherical tokamak; a magnetic mirror machine; a reversed field pinch device; a Z-machine; a Z-pinch device; a theta-pinch device; a screw pinch device; a fusor; or a polywell.

[0047] The or each heat pipe may extend radially with respect to a central axis of a plasma confinement chamber of the plasma confinement device.

[0048] According to a third aspect of the present invention, there is provided a system. The system comprises a heat source and the apparatus according to the first aspect thermally coupled to the heat source.

[0049] In some examples, the apparatus comprises one or more heat exchangers and one or more heat pipes, wherein the or each heat exchanger is operatively coupled to at least one of the heat pipes at the respective second portion or portions thereof.

[0050] The or each heat exchanger may be configured to carry coolant flow and the system further comprises a turbine configured to be driven by said coolant flow to generate electrical power.

[0051] According to a fourth aspect of the present invention, there is provided a thermal management method applied to the apparatus according to the first aspect. The method comprises receiving, by the heat pipe or heat pipes, thermal flux from a plurality of the physically distinct units of the component contemporaneously; and conveying thermal energy from at least a portion of the received thermal flux along or through the heat pipe or heat pipes towards a heat exchanger.

[0052] A magnitude of the thermal flux received by the or each heat pipe from said plurality of physically distinct units may vary with position across the first portion of said heat pipe.

[0053] Conveying at least a portion of the conveyed thermal energy towards a heat exchanger may comprise conveying at least a portion of the conveyed thermal energy into a heat exchanger, wherein the heat exchanger is operatively coupled to the second portion of the or each heat pipe.

[0054] 38306813-1The thermal energy conveyed to the heat exchanger may be provided as a thermal flux to the heat exchanger, and wherein the thermal flux across the second portion of the or each heat pipe is distributed more uniformly than the thermal flux received by the heat pipe is distributed across the first portion of the or each heat pipe.

[0055] The thermal flux to the heat exchanger may be distributed substantially uniformly across the second portion of the or each heat pipe.

[0056] The method may further comprise conveying at least a portion of the received thermal energy into the heat exchanger. The method may additionally comprise exhausting, using a coolant (or more generally a heat exchange fluid) carried by the heat exchanger, at least a portion of the thermal energy conveyed into the heat exchanger.

[0057] In some examples, the component comprises a material having a brittle-ductile transition temperature, DBTT, and a recrystallization temperature, RT, and wherein, during said method steps, the component is maintained at a temperature between DBTT and RT.

[0058] The heat pipe may be a variable conductance heat pipe.

[0059] In some examples, the method further comprises adjusting operating parameters of the heat exchanger to maintain the component at a temperature between DBTT and RT.

[0060] The component of the apparatus that comprises the plurality of physically distinct units arranged in a castellated structure is a component of a plasma confinement device. The method may then further comprise operating the plasma confinement device to generate a plasma; and receiving, by the component, energy from the plasma.

[0061] According to a fifth aspect of the present invention, there is provided a power generation method using the system according to the third aspect. The method comprises receiving, by the or each heat pipe, at least a portion of a thermal flux from the heat source; conveying thermal energy from at least a portion of the received thermal flux along or through the or each heat pipe and into the or each heat exchanger to heat coolant in said heat exchanger; and driving the turbine to turn and generate electrical power using flow of the heated coolant.

[0062] 38306813-1Brief description of the

[0063]

[0064] Figures 1 and 2 are schematic illustrations of a heat pipe.

[0065] Figure 3 is a pressure-temperature phase diagram for a working fluid.

[0066] Figure 4 is a schematic illustration of a thermal management apparatus in cross-section. Figures 5A, 5B and 5C are schematic illustrations showing a heat pipe and component. Figures 6A to 6D are schematic illustrations showing a heat exchanger and heat pipe. Figure 7 is a schematic illustration of a plasma confinement device in cross-section. Figure 8 is a schematic illustration of a divertor of a plasma confinement device.

[0067] Figures 9A to 9C are schematic illustrations of a thermal management apparatus in plan view.

[0068] Figure 10A is a schematic illustration of a heat exchanger in plan view, within which a plurality of heat pipes are arranged.

[0069] Figure 10B is a perspective view of a plurality of heat pipes.

[0070] Figure 11 is a flow diagram of a thermal management method.

[0071] Figure 12 is a schematic illustration of a power generation system.

[0072] Figure 13 is a flow diagram of a power generation method.

[0073] Detailed

[0074]

[0075] In some engineering scenarios, temperature hot spots in a component are problematic because they can lead to localised melting and / or promote high temperature failure modes (e.g., accelerated creep). While hot spots will naturally spread out over time, this is often unacceptably slow. In some examples, hot spots can necessitate periods of downtime, which, in some contexts (e.g., aerospace), is not always possible.

[0076] Hot spots are a particular problem for nuclear fusion plasma confinement devices, as thermal flux is concentrated at particular strike positions on an impingement surface of the component. Often, the location of maximum thermal flux at the impingement surface is not known and / or not easily determined in real time. Cooling systems (e.g., heat exchangers) for these components then overcompensate (i.e. , pump harder across the entire component) as a safety precaution.

[0077] The inventors have realised that by arranging a heat pipe in between the component and the heat exchanger, a spatially non-uniform thermal flux or thermal energy profile that

[0078] 38306813-1strikes the component can be transformed into a more spatially uniform thermal flux or energy profile at the heat exchanger.

[0079] As heat pipe-based thermal management systems have exceptionally high effective thermal conductivities, they are more effective at spreading out hot spots at the component than conventional coolant-based thermal management systems.

[0080] Another advantage of using heat pipes is that heat pipes are more compact than the coolant lines required for conventional thermal management systems. This is at least partly because heat pipes provide passive cooling and do not require a feed or return coolant line. In this regard, heat pipes may be advantageous where available space in the vicinity of the component is limited (as is the case in the context of a nuclear fusion reactor, for example).

[0081] In some examples, the surface area of contact between the heat exchanger and the heat pipe (e.g., approximately the surface area of the baffles 618 shown in Figures 6A to 6D) is greater than the surface area of contact between the heat pipe and the component (e.g., approximately the surface area of attachment portions 422a-i shown in Figure 4) by a factor N. N may be equal to or greater than, for example, 2, 5, or 10. As a result, the maximum temperature at the heat exchanger can be lowered considerably (as compared with the maximum temperature at the component), and the pumping requirements for the heat exchanger greatly reduced. This simplifies operation of the heat exchanger.

[0082] In some examples, the surface area of contact between the component and the heat pipe is preset (e.g., not adjustable without affecting the design of the component), and the factor N is controlled by adjusting a number, size, and spacing of cooling fins and / or baffles arranged in between the heat exchanger and the heat pipe.

[0083] In some examples, the thermal management apparatus includes a plurality of heat pipes, which are affixed to and in thermal contact with the component and which are arranged in a heat pipe array. The heat pipe array may span across a majority (e.g., more than 50%, 60%, 70%, 80%, or 90%) or all of a surface area of the component (e.g., of one side of the component).

[0084] 38306813-1The plurality of heat pipes may be arranged on any of the sides of the component (e.g., a bottom side, a top side, or any edge side). Typically, the component includes an impingement surface (e.g., a top side) for receiving an incident thermal flux. The one or more heat pipes may be affixed to the surface of the component that opposes the impingement surface (e.g., a bottom side).

[0085] The use of such heat pipe arrays also ensures effective cooling of the hot spot no matter its location at the component. This is particularly useful in the context of a plasma confinement device as the strike position of the plasma can be difficult to control and predict in real time.

[0086] Figure 4 is a cross-sectional view of a thermal management apparatus 400, according to an embodiment. The thermal management apparatus 400 comprises a component 402, a heat pipe 404 and a heat exchanger 406 operatively coupled to the heat pipe. In Figure 4, the heat pipe is shown as including a wick 408 but this is for illustrative purposes only. It will be understood that the heat pipe 404 may have a wick or may be wickless, and may be and of any known type.

[0087] In use, a thermal flux profile 410 is incident onto and strikes the component 402. An example thermal flux profile 410 is shown in Figure 4. The spatial distribution of the thermal flux (i.e. , the thermal flux profile) that strikes the component is non-uniform (i.e. , the magnitude of the thermal flux that strikes the incidence surface of the component varies with position across that surface) and the profile exhibits a peak or maximum. In some examples, the thermal flux profile is asymmetric and may be skewed in a direction towards heat exchanger 406. The thermal energy caused to flow from the component 402 to the heat exchanger 406 is denoted in the figure by the two large arrows labelled A, B.

[0088] The thermal flux profile 410 causes the component 402 to heat up in accordance with the thermal flux profile. That is, the thermal flux profile causes the component to heat up more at positions closer to the location of the peak of the thermal flux profile, as compared to positions that are further away from the peak. This generates a temperature hot spot 412 within the component (the boundary of which is denoted by the vertical dotted lines in the figure). The size of the hot spot 412 may be the full-width at half-

[0089] 38306813-1maximum, FWHM, of the temperature profile at the component. For asymmetric hot spots, an average FWHM can be used.

[0090] The heat pipe 404 is in thermal contact with the component 402. Two objects or systems are in thermal contact if thermal energy can be transferred between them, (e.g., if there exists a temperature difference between them and there is no barrier to thermal energy transfer between them). Heat pipe 404 therefore receives thermal energy from the component 402. The thermal flux profile received by the heat pipe (not shown in Figure 4) is, to a first approximation, similar in shape and size to profile 410. That is, the heat pipe receives a thermal flux that varies with position (e.g., along its length) and which exhibits a peak.

[0091] In turn, the heat pipe 404 and the working fluid within the heat pipe is heated in accordance with the thermal flux that it locally receives. This causes a region of greatest evaporation of the working fluid (denoted in Figure 4 by the darkened region 414 in wick 408) to form within the heat pipe and / or at the envelope 416 of the heat pipe. The region of greatest evaporation 414 within the heat pipe and the hot spot 412 within the component may be substantially co-located.

[0092] Heat pipes are sometimes referred to colloquially as “heat superconductors.” Heat is carried away rapidly from the evaporator region(s) of the heat pipe to the condenser region(s).

[0093] In the example of Figure 4, the evaporation rate of working fluid of the heat pipe 404 varies spatially across the mutual interface between the heat pipe 404 and the component 402 in accordance with the spatial distribution of the thermal flux that the heat pipe receives at that interface. The “heat superconductor” property of heat pipes makes heat pipe 404 effective at spreading out the heat from hot spot 412 of the component (the exact location of which may not be known) so that the thermal flux across the mutual interface between the heat pipe and the heat exchanger can be made relatively uniform, and less than the maximum thermal flux received by the heat pipe in the vicinity of the hot spot(s) of the component In this way, the heat exchanger 406 need not be designed to accommodate the maximum thermal flux received at the component 402, as would otherwise be the case absent the heat-spreading capability of the heat pipe 404.

[0094] 38306813-1The heated working gas (i.e. , the vaporised working liquid) moves along the heat pipe 404 towards the heat exchanger 406, where it condenses and releases its latent heat of condensation, which latent heat is extracted by the heat exchanger. In this way, thermal energy is transferred from the hot spot 412 within the component 402 to the heat exchanger. Notably, while the thermal flux received by the component and heat pipe has a non-uniform spatial distribution, the thermal flux profile received by the heat exchanger is more spatially uniform because the working gas can spread out effectively at the heat exchanger before condensing. In some examples, the thermal energy or flux received by the heat exchanger may be substantially spatially uniform. This simplifies the operation of the heat exchanger.

[0095] In addition, the heat exchanger is less affected by variations in the spatial size and shape of the thermal flux profile 410, the maximum temperature of the thermal flux profile, and / or the location of the hot spot 412 on the component because the heat exchanger receives a thermal energy that is proportional to the total thermal flux received by the heat pipe from the component.

[0096] In some examples (not shown), there may be a plurality of hot spots at the component 402 and / or heat pipe. This may arise, for example, if the position of the peak in the thermal flux profile 410 varies with time faster than the thermal management apparatus can remove the presence of the previous hot spot. The heat spreading concept described above may apply to any one or each of these one or more hot spots.

[0097] Returning to Figure 4 in more detail, the component 402 comprises a plurality of physically distinct units (i.e., which are spatially separated from each other) illustratively shown as 402a-402i. For simplicity, only components 402a, 402b, 402h and 402i are labelled in the figure.

[0098] The physically distinct units 402a-i are arranged in a castellated structure. It will be understood that the component may comprise any number of these units (e.g., more or fewer units than shown in the figure). In some examples, the component comprises a multiplicity of units (e.g., more than 10, more than 20, more than 30, or more than 50).

[0099] 38306813-1The units 402a-i are described as being castellated as they form an outer surface that includes a series of spaced ridges or ridgeways 418 (which to some extent may resemble the battlements of a medieval castle). For clarity, only four of the eight ridgeways are labelled in the figure. The units may take various forms, for example, each unit may be a block, a tile, a plate, or a monoblock.

[0100] Each of the plurality of units 402a-402i is in thermal contact with the heat pipe 404 and affixed to the heat pipe at or along a first portion 424 of the heat pipe. It will be appreciated that the heat pipe may be affixed either directly or indirectly to the plurality of units so long as the units and heat pipe remain in thermal contact. That is, the heat pipe and each unit may be in direct physical contact with one another, or they may be spatially separated from one another by one or more interlayers. Example interlayers include bonding materials between the heat pipe and component, such as solders, brazes, and adhesives. Alternatively, or in addition, the heat pipe and component may be bonded together via a further spacing interlayer which is then affixed to each of the component and heat pipe.

[0101] In the example shown, the first portion 424 of heat pipe 404 includes a plurality of physically distinct attachment portions 422a-i of the heat pipe 404. Each attachment portion 422a-i attaches a corresponding unit 402a-i of component 402 to heat pipe 404. For simplicity, only portions 422b and 422h are labelled in the figure. The first portion 424 also includes portions of the heat pipe 404 situated in between adjacent units (e.g., between unit 402a and 402b), which portions are co-located with the spaced ridgeways 418. The first portion 424 presents the surface area of contact or interface between the heat pipe 404 and the component 402 and through which thermal flux can pass between the component and the heat pipe.

[0102] The heat pipe 404 further includes a second portion 426, which is operatively coupled to the heat exchanger 406. The second portion presents the surface area of contact or interface between the heat pipe 404 and the heat exchanger 406 and through which thermal flux can pass between the heat pipe and the heat exchanger.

[0103] In use, the evaporator portion of the heat pipe 404 may include at least part of or all of the first portion 424.

[0104] 38306813-1In use, the condenser portion of the heat pipe may include at least part of or all of the second portion 426.

[0105] In use, an adiabatic portion of the heat pipe may include a third portion 428 of the heat pipe that is interposed between the first and second portions. A thermally insulating jacket (not shown) may be arranged around the third portion of the heat pipe (to minimise heat transfer into and out of that portion). The thermal flux incident onto the third portion of the heat pipe is expected to be negligible in comparison with the thermal flux incident onto the first portion of the heat pipe.

[0106] In Figure 4, the adiabatic portion 428 does not include any attachment portion to any one physically distinct unit 402a-i. In practice, however, the adiabatic portion 428 may include or encompass attachment portions to one or more of the physically distinct units 402a-i (e.g., to units 402h and 402i). During normal operation, these units are functionally redundant, in the sense that they are not expected to receive or extract any thermal flux. However, the one or more physically distinct units (e.g., units 402h and 402i) may receive an incident thermal flux from profile 410, if the profile is shifted towards the heat exchanger 406. This may happen under abnormal or unexpected conditions. Advantageously, it also means that less precise alignment of the component 402 with respect to the expected thermal flux profile 410 is required, thereby facilitating installation of the component.

[0107] In some examples, the heat pipe 404 is affixed to the component by an interlayer (not shown). The interlayer may be a solder, braze, ora separate material layer to be soldered or brazed between the body of the component and the heat pipe. Optionally, the coefficient of thermal expansion, CTE, for the interlayer is intermediate between the CTE of the envelope of the heat pipe and the CTE of the component. This reduces the induced thermal stresses in the apparatus during thermal loading. The CTE may be measured under standard conditions and / or at operating temperature.

[0108] In some examples, the heat pipe and the component are formed from the same material (e.g., a tungsten alloy). This advantageously avoids the need to design and / or select an interlayer with an intermediate CTE (which for some material combinations can be challenging).

[0109] 38306813-1In some examples, the thermal management apparatus 400 further comprises a controller 430 for adjusting the operating parameters of the heat exchanger. One or more temperatures sensors (not shown), for measuring a temperature of, or across, the component, may be incorporated into the apparatus for setting up a control loop (e.g., a feedback loop) with the controller.

[0110] The heat pipe 404 may be any known type of heat pipe. The heat pipe may include an elongate channel 420, as shown in Figure 4. The elongate channel may be straight or include one or more bends. The bends may be made up of one or more straight and / or curved sections. The external shape of the heat pipe may be made suitable to the particular application or installation; e.g., it may be smooth and / or include undulations. The heat pipe and / or its channel may follow or trace a contour of a smooth external shape of the component (e.g., the plasma-facing surface of the component). The contour may comprise one or more straight line segments, curves, or a combination of straight-and curved-line segments. The external shape of the heat pipe may be tubular or planar, with any cross-sectional shape (e.g., square, rectangle, hexagon, circle, etc.).

[0111] In an alternative embodiment, as shown in Figure 5A, a heat pipe 504 is partially embedded within a component 502. For simplicity, the component in Figure 5A includes five units 502a-502e rather than nine units as depicted in Figure 4. It will be understood that the component may include any number (e.g., a multiplicity) of units.

[0112] In Figure 5A, the attachment portions between the heat pipe 504 and units 502a-e are at least partially embedded within the units 502a-502e. If present, the interlayer is also embedded within the units 502-502e.

[0113] In a variant of Figure 5A, the heat pipe 504 may, as shown in Figure 5B, pass completely through each of the units 502a-e. Each of the units 502a-e in Figure 5B has an opening (not visible in Figure 5B) through which the heat pipe passes. In Figure 5B, the first portion of the heat pipe extends through each of the units of the component. The attachment portions between the heat pipe 504 and units 502a-e are embedded within and / or extend through each of the units. If present, the interlayer is also embedded within and / or extends through each of the units.

[0114] 38306813-1A perspective view of three units 502a-c from Figure 5B is shown in Figure 5C. As shown, the opening 506 (through which the heat pipe 504 passes or extends) and the heat pipe 504 are circular in cross-section. Other shaped cross-sections, such as square, rectangular, are possible. Square and rectangular openings, which have sharp corners, may be prone to stress concentrations and fatigue failure. In some examples, the opening and heat pipe are rectangular or square in cross-section with rounded corners. The dotted lines in Figure 5A, Figure 5B, and Figure 5C show the hidden lines of the edges of the units.

[0115] Figure 6A is a cross-sectional view of a heat exchanger 606, showing a heat pipe 604 arranged within the heat exchanger 606. For simplicity, only the second portion (e.g., the condenser portion) of the heat pipe 604 is shown and the first and third portions are omitted.

[0116] The heat exchanger 606 comprises a vessel 608, the vessel comprising a closed end 610, an open end 612, a peripheral wall 616 extending between the closed and open ends, and a plurality of spaced alignment fins 614.

[0117] The heat pipe 604 comprises a plurality of baffles 618, which extend outwardly relative to the heat pipe. The open end of the vessel is sealed closed against the periphery of the heat pipe so as to avoid loss of coolant from within the vessel during use.

[0118] In the configuration shown in Figure 6A, the second portion of the heat pipe 604 comprises a peripheral surface of the heat pipe contained within the vessel 608 and the plurality of baffles 618. In some examples, the combined surface area of the baffles and the peripheral surface of the heat pipe contained within the vessel (and thereby the total surface through which heat can be transferred to the heat exchanger 606) is greater than the surface area of contact between the heat pipe and the component 402 (i.e., at the first portion 424, which includes attachment portions 422a-i) or the surface area of the incidence surface of the component by a factor N, where N is greater than 1. For example, N may be equal to or greater than 2, 5, or 10. As a result, the thermal flux arriving at the heat exchanger can be lowered considerably as compared with the thermal flux impinging upon the incidence surface of the component, and the pumping requirements for the heat exchanger therefore greatly reduced.

[0119] 38306813-1A perspective view of the heat pipe 604, with only five baffles 618 for simplicity, is shown in Figure 6B. A cross-section along section A-A’, as shown by the dotted line in Figure 6A, is shown in Figure 6C. The baffles are shown as being circular in cross-section, although it will be understood that other shapes in cross-section are possible. The baffles may be embedded within, or otherwise affixed to the heat pipe (e.g., by welding or by brazing). In some examples (not shown), the baffles include one or more orifices to increase their surface area.

[0120] A cross-section along section B-B’, as shown by the dotted line in Figure 6A, is shown in Figure 6D. The alignment fins are shown as being generally rectangular in crosssection, with their ends shaped to conform to the curvature of the heat pipe 604 and the inner surface of the vessel wall 608. It will be understood that the heat pipe 604 and the inner surface of the vessel may, in some examples, be substantially planar. The alignment fins may be integrally formed on (i.e. , form part of) the peripheral wall 616 of the vessel 608 (e.g., through casting or additive manufacturing techniques). Alternatively, the alignment fins may be manufactured separately from the vessel 608 and subsequently affixed onto the peripheral wall (e.g., by welding or brazing).

[0121] Returning to Figure 6A, the baffles 618 and alignment fins 614 are spaced and arranged in size and shape such that, when the heat pipe is inserted into the vessel, the baffles align with and fit snugly (e.g., are flush with the fins) within the spaces between the fins. In the example shown, the fins and baffles are evenly spaced but in other examples (not shown), the fins and baffles may have corresponding non-uniform spacings.

[0122] The fins 614 facilitate alignment of the heat pipe 604 within the vessel 608, mechanically stabilise the heat pipe 604 within the vessel, and also promote efficient transfer of thermal energy away from the heat pipe (be that directly from the heat pipe envelope to the fin or via the baffle).

[0123] In use, a coolant (or, more generally, a heat exchange fluid), such a helium or carbon dioxide gas, is pumped through the vessel 608 via a respective inlet and outlet (not shown in Figure 6A). As shown by comparing Figures 6C and 6D, the coolant is able to flow in a compartment formed between adjacent baffles 618, and which comprises alignment fins 614. This is further illustrated in a plan-view in Figures 10A and 10B. The coolant therefore generally flows in a direction transverse to the elongate channel of the

[0124] 38306813-1heat pipe. The snug fit between the baffle and the vessel, as shown in Figure 6C, prevents or restricts coolant flow between adjacent compartments. This arrangement permits cooling of the heat pipe along the entire length of the evaporator portion.

[0125] In some examples, the heat pipe comprises a valve or a port 620 through which the working fluid and charge (if present) can be removed or replenished, as needed. This is particularly useful in the fusion context because ions and / or gases, such as those comprising hydrogen and / or helium, may diffuse and accumulate within the heat pipe, thereby affecting its performance over time. Periodic removal of these accumulated ions and / or gases and replenishment of the working fluid and NCG (if present) is desirable in this regard.

[0126] Baffles similar to the baffles 618 shown for heat pipe 604 in Figure 6A may be included at the second portions of heat pipes 404 and 504 shown in any one of Figures 4 and 5A to C. In addition, the heat exchanger 406 shown in Figure 4 may include the features (e.g., the alignment fins 614) of heat exchanger 606 from Figure 6A.

[0127] In alternative embodiments, the heat pipe 604 comprises a plurality of cooling fins, which extend outwardly relative to the heat pipe but which, unlike baffles 618, do not extend circumferentially around the heat pipe. In use, the heat exchange fluid is pumped through the vessel 608 via the respective inlet and outlet and into contact with each of the plurality of cooling fins within a unitary compartment formed within the vessel 608 (cf. the plurality of compartments defined by baffles 618). In such embodiments, the vessel 608 may or may not comprise alignments fins 614.

[0128] Figure 7 is a schematic illustration of a plasma confinement device 700 (e.g., a spherical tokamak) shown in cross-section. The figure is symmetrical both left-right and topbottom, and for clarity reference numerals have not been duplicated for symmetrical components. It will be understood that the plasma confinement device may, in other examples, be asymmetrical left-right and / or top-bottom.

[0129] The plasma confinement device 700 includes a lower divertor 710 and an upper divertor 720, which are arranged within a plasma confinement chamber 730. Upper refers to an upward direction relative to gravity, whereas lower refers to a downward direction relative to gravity. In use, a plasma 740 is generated within the plasma confinement chamber

[0130] 38306813-1and heat and ash are exhausted via one or both divertors. In some examples, the plasma confinement device may include one of a lower or an upper divertor.

[0131] Each of the lower and upper divertor include a plurality of divertor surfaces 710a, 710b, 710c: an inboard divertor surface 710a, an outboard divertor surface 710c, and an intermediary divertor surface 710b. The intermediary divertor surface 710b is shown in Figure 7 as planar. In some examples the intermediary divertor surface 710b may be dome-shaped and referred to as a dome surface. Outboard refers to a direction radially outward relative to a central axis 704 defined by a central column 702 of the plasma confinement device, whereas inboard refers to a direction radially inward relative to the central column.

[0132] The plasma confinement device 700 further comprises a magnetic confinement system (e.g., a plurality of poloidal field coils 706 and toroidal field coils (not shown)) to control the plasma 740.

[0133] Figure 8 is a schematic illustration of a lower divertor 710 in cross-section, substantially as shown in Figure 7 but with intermediary divertor surface 710b assuming a domed profile rather than a planar profile.

[0134] It is noted that Figure 8 shows a lower divertor of the plasma confinement device only. In some examples, the plasma confinement device may include both an upper and a lower divertor or only an upper divertor. If present, the upper divertor may include a corresponding set of divertor surfaces, for example, an upper inboard divertor surface, an upper outboard divertor surface, and an upper intermediary (e.g., dome) surface.

[0135] The lower divertor incorporates a thermal management apparatus according to an embodiment, denoted by reference numeral 800. The thermal management apparatus includes a heat pipe 804 (similar to heat pipes 404, 504, 604 in Figures 4, 5A-5C and 6A-6D respectively) and a first and a second heat exchanger 806a, 806b operatively coupled to a respective second portion of the heat pipe 804. Each second portion and heat exchanger 806a, 806b may be as shown in Figures 6A to 6D.

[0136] In some examples, each second portion of the heat pipe includes a longitudinal end portion of the elongate channel (if the elongate channel has ends). In other examples,

[0137] 38306813-1each second portion of the heat pipe includes one or more bends of the elongate channel (e.g., if the elongate channel forms a closed loop without ends). In a specific example, the one or more bends may be serpentine bends and the elongate channel traces a serpentine path.

[0138] In the context of a plasma confinement device, it is known to cool a divertor surface using a pumped coolant flow (typically water). One disadvantage of this approach is that the thermal management apparatus is bulky: coolant flow is one-directional and requires both coolant feed and return lines. This conflicts with the limited space available within plasma confinement devices. Heat pipes, on the other hand, do not require feed or return lines and the flow of the working fluid contained within the heat pipe can be in any direction (e.g., downwards toward the first exchanger and / or upwards towards the second heat exchanger). As such, while it has been impractical or impossible to include a second heat exchanger into conventional thermal management apparatuses for divertors within a plasma confinement device, the use of heat pipes in the configuration described in relation to Figures 4, 5A to 5C, 8, 9A, 9B, and 9C, for example, makes it possible.

[0139] The divertor surface 710a comprises a plurality of divertor units 802a-i (e.g., blocks, monoblocks, plates or tiles). The divertor is one example for components 402, 502. Further detail of the units is provided above in relation to Figures 4 and 5A to C and, for brevity, is not repeated here.

[0140] The arrows F in the figure denote the expected direction of the incident thermal flux originating from the plasma 740 (in Figure 8 only the lower portion of plasma 740 is shown) during operation. As shown, the thermal flux impinges on the divertor surface 710a at an oblique angle. As a result, the thermal flux may not only strike the units on their plasma-facing surfaces but also on their upper peripheral surfaces that extend between the plasma-facing surfaces and the surfaces facing away from the plasma.

[0141] The units 802a-i may be positioned and shaped so as to prevent heat flux F from directly striking heat pipe 804. In some examples, the spacing of the units 802a-i is designed to be small enough to prevent the thermal flux from striking the heat pipe directly. Alternatively, or in addition, the plasma-facing surface of each unit may be angled or bevelled (in the toroidal or poloidal direction) to shadow the spaces between the units

[0142] 38306813-1(e.g., the underlying heat pipe 804). That is, the units 802a-i may be shaped to be non-rectangular (e.g., trapezoidal or rhomboidal) in cross-section, with the plasma-facing surfaces angled so as to shade or shadow the spaces between the units 802a-i from thermal flux F. In yet further examples, the cross-section of the units 802a-i may be non-uniform to achieve a similar effect (e.g., conical in the toroidal or poloidal direction).

[0143] The arrows F in Figure 8 may be seen to represent vectors showing the direction of thermal flux originating from the plasma 740 during operation and impinging on divertor surface 710a. It will be appreciated that these thermal flux vectors each include a component (that is, a component of the vector) having a direction transverse to a longitudinal direction defined by the elongate channel of the heat pipe. Simply put, the thermal flux strikes the broad side of the heat pipe rather than striking the heat pipe end-on. The angle of incidence of the thermal flux vectors with respect to the or a longitudinal direction of the heat pipe or heat pipes (e.g., when the heat pipes are disposed in an array as described further below with reference to Figures 9B and 9C) may vary according to the particular arrangement of the heat pipe(s) in the plasma confinement device, as well as the location of the plasma within the confinement device, the shape of the plasma, and so forth. In some examples, the incident thermal flux may impinge on the divertor, or other plasma confinement device component (e.g., breeder blanket, limiter, etc. as described further below) in which the heat pipe or heat pipes are embedded, in a direction more or less oblique than shown in Figure 8, such as in a direction substantially perpendicular to the or a longitudinal direction of the heat pipe or heat pipes.

[0144] Turning to Figures 9A to 9C, plan views of, respectively, thermal management apparatuses 900, 910, 920, according to specific embodiments, are shown.

[0145] Each of the thermal management apparatuses 900, 910, and 920 includes a plurality of physically distinct component units (respectively, 902a-l, 912a-l, and 922a-l) in a castellated structure, one or more heat pipes (respectively, 904, 914, and 924), and one or more heat exchangers (respectively, 906, 916, and 926). The units 902a-l, 912a-l, 922a-l, each heat pipe 904, 914, 924, and each heat exchanger 906, 916, 926 may be substantially as described in relation to Figures 4, 5A to C, 6A to 6D. The difference is that the heat pipe of Figure 9A includes a manifold section 908, there are a plurality of

[0146] 38306813-1heat pipes in Figure 9B and 9C, and the heat exchanger 926 in Figure 9C is associated with a plurality of heat pipes 924.

[0147] Referring in more detail to Figure 9A, the heat pipe 904 includes a manifold section 908, from which a plurality of heat pipe branches 904a, 904b, 904c extend. Each of the heat pipe branches is operatively coupled to a respective one of a plurality of heat exchangers 906 (denoted 906a, 906b, 906c). The manifold section may be located in the adiabatic portion (i.e. , the third portion) of the heat pipe in proximity to the heat exchanger (e.g., adjacent to the second portion of the heat pipe). In Figure 9A, three heat exchangers and three heat pipe branches are shown, but it will be understood that there may be fewer or more heat exchangers and heat pipe branches. There may also be more heat pipe branches than heat exchangers (i.e., each or some of the heat exchangers may be shared amongst a plurality of heat pipe branches).

[0148] Turning to Figures 9B and 9C, the thermal management apparatuses 910, 920 each include a plurality of heat pipes arranged into an array (herein heat pipe array). In Figure 9B, there are three heat pipes 914 arranged into array, whereas in Figure 9C there are five heat pipes 924 arranged into array. It will be understood that the arrays can each include any number of heat pipes.

[0149] In Figure 9B, each heat pipe 914 is operatively coupled to a respective one heat exchanger 916a, 916b, 916c. In Figure 9C, each heat pipe 924 is operatively coupled to a shared or common heat exchanger 926.

[0150] Each heat pipe 914, 924 in Figures 9B and 9C is associated with a respective set (denoted 918a-c, 928a-e) of component units. For simplicity, only sets 918a and 918c are labelled in Figure 9B, and only sets 928a and 928e are labelled in Figure 9C. The units included in each of these sets is shown by the dotted lines in the figures. For thermal management apparatuses 900, 910, 920 that include a plurality of heat pipes 914, 924, the component 402, 502 may comprise all of the respective sets of units. Each of the respective sets of units may comprise a multiplicity of units (e.g., more than 10, more than 30, or more than 50 units).

[0151] In some examples, the heat pipe array spans across a majority (e.g., more than 50%, 60%, 70%, 80%, or 90%) or all of a surface area of the component (e.g., of one side).

[0152] 38306813-1For example, the heat pipe array can be arranged on any of the sides of the component. Typically, the component includes an impingement surface (e.g., a top side) for receiving an incident thermal flux and the heat pipe array is arranged in thermal contact with the surface of the component that opposes the impingement surface (e.g., its bottom side).

[0153] In the heat pipe array of Figure 9B, each heat pipe 914 forms a row or column of the heat pipe array. The plurality of physically distinct units 912a-l are then collectively arranged into a rectilinear array, with each unit being substantially similar to one another in form (i.e. , in shape and size) and each set 918a, 918b, 918c of units forming a row or column of the rectilinear array. The rectilinear array in Figure 9B is rectangular but, alternatively, the array may be square, hexagonal, or triangular, for example.

[0154] Turning to Figure 9C, each heat pipe 924 also forms a row or column of the heat pipe array, with each heat pipe extending radially from a notional centre 930. In the context of a plasma confinement device, the notional centre coincides with a central axis or core of the plasma confinement chamber of the plasma confinement device.

[0155] The heat pipes (and if applicable their elongate channels) in Figures 9B to 9C are shown as being straight in plan view but, in other examples, some or all of the heat pipes may trace a curved or serpentine path. That is, some or all of the heat pipes and / or elongate channels may include one or more curved (e.g., ll-bend) sections. The component may also include a planar or curved surface. As has been noted above, the heat pipe and / or its channel may follow or trace a contour of a smooth external shape of the component (e.g., the plasma-facing surface of the component). The contour may comprise one or more straight line segments, curves, or a combination of straight- and curved-line segments. Some or all of the heat pipes in Figure 9B to 9C may be similarly shaped.

[0156] Combinations of the thermal management apparatus 900, 910, 920 of Figures 9A to 9C are possible. For example, any one or more of the heat pipes in Figure 9B and 9C may include a manifold section from Figure 9A, and two or more (e.g., all) of heat pipe branches 904a, 904b, 904c in Figure 9A may each be operatively coupled to a common heat exchanger.

[0157] Figure 10A is a cross-sectional view of a heat exchanger 1006 in plan view, showing a plurality of heat pipes 1004 arranged within the heat exchanger 1006. The heat pipes

[0158] 38306813-1are arranged into an array. For simplicity, only the second portion of the heat pipe that is operatively coupled to the heat exchanger is shown and the first and third portions of the heat pipe are omitted. The heat exchanger and the second portion of the heat pipe may be substantially as described in relation to Figures 6A to 6D.

[0159] As shown, the heat exchanger 1006 comprises a vessel 1008, an inlet manifold 1010 and an outlet manifold 1012. Each of the heat pipes is associated with a plurality of baffles 1018. The baffles are most apparent in Figure 10B, which is a perspective view of the heat pipe array from Figure 10A, with the heat exchanger omitted for simplicity.

[0160] As may be seen by comparing Figure 10A and Figure 10B, each of the baffles 1018 is shared amongst the plurality of heat pipes 1004 such that a compartment or channel 1014 through which coolant may flow from the inlet manifold to the outlet manifold is formed between the baffles and the vessel. One such compartment or channel 1014 is shown in Figure 10A and denoted by the dashed lines.

[0161] In operation, coolant (or, more generally, heat exchange fluid) is pumped into the vessel 1008 via inlet manifold 1010, into each of a plurality of compartments or channels 1014, and out via the outlet manifold 1012. The coolant passes into and through each compartment or channel in parallel. The coolant passes over each of the heat pipes 1004 in series in a direction transverse to the elongate channel of each heat pipe. The flow of coolant through one compartment 1014 is denoted by an arrow in the figure.

[0162] In some examples, the component (e.g., components 402, 502 from, respectively, Figure 4 and Figures 5A-5C) may be a castellated armour or have a castellated armour. The castellated armour may protect the component itself, the heat pipe, non-armoured parts of the component, or any combination of these, from incident heat flux and may also protect against radiation damage, for example, from high-energy neutrons emitted by a fusion plasma. In the example of Figure 8, the component is the divertor 710 (or, alternatively, the inboard divertor surface 710a), and the units 802a-i are the castellated armour.

[0163] In general, an armour, such as castellated armour, is more heat resistant than that which it protects and a component may be considered to be armour if that component protects itself, the heat pipe or another component from incident thermal energy or thermal flux.

[0164] 38306813-1In some examples, a component is an armour if it is more heat resistant than the heat pipe. That is, the component is an armour if it can protect other parts of the apparatus (e.g., the envelope of the heat pipe) from the adverse effects (e.g., melting or softening) of an incident thermal flux. A component with greater heat resistance can withstand higher thermal fluxes without melting.

[0165] In some examples, the armour, such as a castellated armour, may act as a hydrogen isotope permeation barrier for the component or layer that it serves to protect.

[0166] A component may be heat resistant if the melting point of the material making up the component, at 0.1 MPa (1 bar), is greater than 1100°C (1373K), optionally greater than 1500°C (1773K), optionally greater than 2000°C (2273K).

[0167] The component may be heat resistant if it comprises a refractory metal, such as niobium, molybdenum, osmium, tantalum, tungsten or rhenium, or a refractory alloy comprising a mixture of one or more of these refractory metals.

[0168] Tungsten and tantalum are examples of materials that are resistant both to heat and to the high-energy neutrons emitted by, for example, a deuterium-tritium fusion plasma.

[0169] In some use cases, a low sputtering yield to incident particles (e.g., neutrons, protons) is also desirable. Materials with a lower sputtering yield erode less (i.e., lose less material), when subject to a given flux of incident particles. In the context of this disclosure, an armour has low sputtering yield, if its sputtering yield for neutrons or protons is less than either (1) the component which it protects (if the component has or comprises castellated or other armour for another component or for itself) or (2) the heat pipe (e.g., the envelope) which is affixed to the component.

[0170] Tungsten is an example of a material with a low sputtering yield. Other high atomic number metallic elements (>=40) also have acceptably low sputtering yields. In general, the component may include a metallic element as a main (i.e., the element with the highest atomic fraction) or sole (i.e., contains one element only, excluding trace elements) constituent, the metallic element having an atomic number greater than or

[0171] 38306813-1equal to 40 to achieve a low sputtering yield. Example non-metallics that exhibit low sputtering yield include carbon fibre composites (e.g., for the divertor) and beryllium (e.g., for the first wall of the plasma confinement device).

[0172] Operation of any of the thermal management apparatuses from Figures 4, 8, and 9A to 9C is now described, with reference to Figure 11.

[0173] Method 1100 comprises steps 1102 through 1110. In step 1102, the heat pipe receives a thermal flux or energy from a plurality of physically distinct units of the component contemporaneously. As has been noted above, one or more of the units of the component may be arranged in an adiabatic portion of the heat pipe (for which no or negligible thermal transfer is expected in normal operation). It will be understood, therefore, that the plurality of physically distinct units from which the heat pipe receives thermal energy may not, in some examples, include all the units of the component.

[0174] In some examples, a magnitude of the thermal energy or flux received by the heat pipe from the plurality of physically distinct blocks varies with position across the heat pipe (e.g., across the first portion of the heat pipe).

[0175] In step 1104, at least a portion of the energy from the received thermal flux is conveyed along or through the heat pipe (e.g., along the elongate channel of the heat pipe or defined by the heat pipe) and towards a heat exchanger.

[0176] In some examples, the thermal flux of heat conveyed from the heat pipe to the heat exchanger is distributed more uniformly across the second portion of the heat pipe at the heat exchanger than the thermal flux received by the heat pipe is distributed across the first portion of the heat pipe. In other words, the heat pipe serves to spread the input heat flux, which may have a peaked distribution or hot spot such as hot spot 412 in Figure 4, into a more uniform heat flux at the heat exchanger. In a specific example, the thermal flux is distributed substantially uniformly across the second portion of the heat pipe at the heat exchanger.

[0177] In some examples, the surface area of contact or interface between the heat exchanger and the heat pipe (and through which heat is transferred) is greater than the surface area of contact or interface between the heat pipe and the component by a factor N. For

[0178] 38306813-1example, N may be equal to or greater than 2, 5, or 10. As a result, the maximum temperature of the thermal flux or thermal energy profile received by the heat exchanger can be lowered considerably (as compared with the maximum temperature at the component), and the pumping requirements for the heat exchanger greatly reduced. This simplifies operation of the heat exchanger (or heat exchangers, in examples where there are more than one).

[0179] In optional step 1106, a portion of the energy from the received thermal flux is conveyed along or through the heat pipe (e.g., along or through the elongate channel) and into the heat exchanger, to which the heat pipe is operatively coupled.

[0180] In optional 1108, at least a portion of the thermal energy conveyed into the heat exchanger is exhausted from the heat exchanger using a coolant (or, more generally, a heat exchange fluid) carried by the heat exchanger. The coolant may be, for example, water, a molten metal (e.g., an alkali metal, such as lithium or alloy thereof), a molten salt, an inert gas (such as helium), or carbon dioxide. Mixtures of coolants are also possible.

[0181] If the thermal management apparatus includes a plurality of heat pipes, then the method of Figure 11 may apply to each of these plurality of heat pipes and their corresponding heat exchanger(s) contemporaneously. As has already been noted above, each of the plurality of heat pipes may be operatively coupled to the same or a different heat exchanger.

[0182] In some examples, it is beneficial if the component is maintained above a predetermined temperature during operation. In a specific example, the predetermined temperature is between the ductile-brittle transition temperature, DBTT, of the material comprising the component and the recrystallization temperature, RT, of that material.

[0183] In optional step 1110, the operating parameters of the heat exchanger are adjusted to maintain the component at a temperature between DBTT and RT. Example operating parameters of the heat exchanger include the coolant flow rate, the coolant pressure, and the coolant temperature. For instance, the coolant may be held at a constant temperature (e.g., 473K) and the coolant flow rate increased or decreased, depending on if more or less cooling is required.

[0184] 38306813-1Variable conductance heat pipes, suitably charged with a NCG, can further facilitate temperature control of the component between its DBTT and RT through their control over the condenser portion length. This may simplify operation of the heat exchanger (as compared to a constant conductance heat pipe).

[0185] If the component comprises tungsten, the component may be held within a temperature range of 523K to 1373K. If the envelope of the heat pipe comprises a copper alloy, for instance oxygen free Cu or CuCrZr alloy (e.g., 0.6-0.9wt% Cr, 0.07-0.15wt% Zr, Cu balance), then the heat pipe is maintained within a temperature range of 300K to 573K (i.e., between the irradiation embrittlement temperature and the irradiation enhanced creep temperature).

[0186] The disclosed thermal management apparatus is particularly useful in systems with a heat source that emits high thermal fluxes (e.g., greater than 1 MWnr2). An example system is a plasma confinement device, where thermal fluxes can be greater than 10 MWnr2and distributed non-uniformly across a plasma impingement surface (e.g., a plasma facing component). Thermal energy may be transferred to the plasma impingement surface by conduction, convection, or radiation.

[0187] Example plasma confinement devices include: a magnetic confinement device, such as a tokamak (spherical or otherwise), a stellarator, a spheromak, a magnetic mirror machine, and a reversed field pinch device; inertial confinement devices, such as indirect drive, direct drive, fast ignition, magneto-inertial fusion devices, and Z-machines; pinch devices, such as a Z-pinch, theta-pinch, or screw-pinch device; and inertial electrostatic confinement devices, such as fusors or polywells.

[0188] In a plasma confinement device, the thermal management apparatus may comprise any one or more of the following:

[0189] • a component (e.g., component from Figure 4, 5A to 5C, 8, 9A to 9C) comprising a plurality of physically distinct tungsten units (e.g., blocks, monoblocks, plates or tiles) arranged in a castellated formation. In a specific example, the width and length of each tungsten unit is 10 to 15 mm by 20 to 30 mm, the spacing between each of adjacent units is around 0.5 mm and the thickness of each tungsten unit is at least 5mm. The component may be any of: a shielding layer for the plasma

[0190] 38306813-1confinement device; a plasma facing component, PFC; a divertor; a limiter; a first wall component; a breeder blanket; a portion of any of these; an armour for any of the foregoing or for a portion thereof; or a thermal management component for any of the foregoing.

[0191] • one or more heat pipes, such as:

[0192] o a wick-containing heat pipe. The wick may be a multi-artery composite of silicon carbide, SiC. The envelope may be made from a material comprising tungsten, a vanadium, V, alloy, a niobium-zirconium alloy (such as Nb-1Zr wt%), a copper alloy (such as CuCrZr alloy, e.g., 0.6- 0.9wt% Cr, 0.07-0.15wt% Zr, Cu balance, or oxygen free Cu), or a steel (such as reduced activation ferritic martensitic, RAFM, steel). The working fluid may comprise or consist of: water, sodium, lithium, potassium, caesium, or a metallic alloy thereof, e.g., a sodium-potassium alloy, such as NaK. Optionally, the heat pipe can be charged with a noncondensable gas, such as helium. The heat pipe can be a vapour chamber or conventional tubular type heat pipe.

[0193] o One or more wickless heat pipes. The heat pipe can be an oscillating or thermosiphon type heat pipe.

[0194] o Each heat pipe (e.g., a tubular heat pipe) may have a maximum diameter of 25 mm and a length greater than 150 to 550 mm.

[0195] • The structural material for the heat exchanger may be a V-alloy, steel, or SiC.

[0196] • The coolant for the heat exchanger may be or comprise water, helium, or carbon dioxide. Other coolants are, however, possible.

[0197] SiC is a particularly useful wick for plasma confinement devices. It exhibits excellent thermal conductivity (comparable to brass) but poor electrical conductivity (it is classified as a semiconductor). The low electrical conductivity of the SiC reduces or suppresses magnetohydrodynamic, MHD, effects, which can act on electrically conductive fluids (e.g., liquid metals), when they traverse magnetic flux lines.

[0198] NaK is particularly beneficial as a working fluid for the heat pipe in a plasma confinement device because it is operative at room temperature. As a result, a heat pipe using NaK would not require preheating before use (i.e. , to melt any solid charge).

[0199] 38306813-1More generally, the charge or working fluid can include or consist of any of: water, or a metal comprising an alkali metal, such as: lithium, sodium, potassium, caesium, or a mixture thereof.

[0200] The heat pipe may be operative within a temperature range of 150 to 300°C (423 to 573K) for water, from around 400°C (673K), for caesium, and up to around 1300°C for alkali metal mixtures. In some examples, the heat pipe is operative from room temperature (typically 20°C to 25°C) to 700°C, 1000°C, or 1300°C. It will be understood that these temperature ranges are not exhaustive: the heat pipe may be operative at temperatures down to its freezing point at the given pressure.

[0201] Figure 12 is a schematic illustration of a power generation system 1200. The system includes a heat source 1202, the thermal management apparatus 400, 800, 810, 900, 910, 920 described above in relation to any of the foregoing embodiments, which is thermally coupled to the heat source, and a turbine 1206. The turbine is operatively coupled to one of the one or more heat exchangers of the apparatus. In general, there may be a plurality of turbines operatively coupled to each heat exchanger. In some examples, the system 1200 is or includes any one of the plasma confinement devices referred to above.

[0202] Figure 13 is a flow diagram of a power generation method 1300 carried out by power generation system 1200.

[0203] In step 1302, one or more heat pipes receive at least a portion of a thermal energy emitted by a heat source. In some examples, the heat source may be plasma, such as a nuclear fusion plasma, which impinges upon (i.e. , strikes) an impingement surface of the component (e.g., a divertor in a tokamak) at a strike point. The plasma may impinge upon the impingement surface of the component at an oblique or perpendicular angle thereto.

[0204] Prior to or contemporaneously with step 1302, plasma operating parameters may be controlled or adjusted to generate or sustain a plasma within the plasma confinement device. The strike point of the plasma on the component may vary continuously with time. As a result, one or more hot spots may develop at the component.

[0205] 38306813-1In step 1304, at least a portion of the received thermal energy is conveyed along or through each or the heat pipe (e.g., along or through the elongate channel of each or the heat pipe) and into the or each heat exchanger. Coolant carried by the heat exchanger is heated up in step 1304.

[0206] In step 1306, a turbine is driven to turn by the flow of the heated coolant in order to generate electrical power.

[0207] Although the invention has been described in terms of specific embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure, which are contemplated as falling with the scope of the appended claims. Each feature disclosed or illustrated in the present application may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein. It will be understood that the numbering in the method flow diagrams is not intended to impose a strict ordering of those steps.

[0208] Aspects of the invention are summarised by the following numbered clauses:

[0209] 1. A phase-transition mediated heat pipe partially embedded in a castellated armour.

[0210] 2. The heat pipe of clause 1 wherein a first portion of the heat pipe passes through the armour and a further portion or portions (e.g., the second or the third portion as described above) of the heat pipe extends away from the armour.

[0211] 3. The heat pipe of clause 2 wherein the castellated armour comprises a plurality of monoblocks arrayed along a length of the first portion of the heat pipe.

[0212] 4. The heat pipe of clause 2 wherein the heat pipe is operatively coupled to a heat exchanger in a vicinity of the second portion of the heat pipe.

[0213] 5. Apparatus comprising a plurality of the heat pipes of clause 1 and a component for a plasma confinement device (for nuclear fusion), wherein the component has armour comprising the armour wherein the heat pipes are partially embedded.

[0214] 38306813-16. The apparatus of clause 5 wherein the armour is wholly or partially integrated into the component.

[0215] 7. The apparatus of clause 5 wherein the component is for a plasma confinement device having, at least approximately, a toroidal, spherical, circular, or other geometric symmetry around a central axis, and wherein each of the heat pipes has a long axis disposed in a direction substantially radial with respect to a point on the central axis.

[0216] 8. The apparatus of clause 5 wherein the component has a plasma-facing surface and wherein each of the heat pipes has a long axis disposed in a direction substantially parallel to a smooth surface approximating the plasma-facing surfaces.

[0217] 9. The apparatus of clause 8 wherein the plasma-facing surface of the component is coincident with a surface of the armour.

[0218] 10. A system comprising the apparatus of clause 5 and a plasma confinement device wherein the component is disposed.

[0219] 11. The system of clause 10 wherein the component, as disposed in the plasma confinement device, has a surface facing a plasma confinement region of the plasma device, and wherein each of the heat pipes has a long axis substantially parallel to a smooth surface approximating the surface of the component facing the plasma confinement region of the plasma device.

[0220] 12. Apparatus comprising:

[0221] a heat exchanger; and

[0222] a plurality of the heat pipes of clause 1 disposed in an array or manifold and operatively coupled to the heat exchanger.

[0223] 13. In a system comprising the apparatus of clause 5 operatively coupled to a heat exchanger and further comprising a plasma confinement device wherein the component is disposed, a thermal management method comprising:

[0224] receiving heat at the component from a plasma contained by the plasma confinement device during operation of the system;

[0225] conveying at least a portion of the received heat to the heat exchanger through the heat pipes; and

[0226] exhausting at least a portion of the conveyed heat away from the heat exchanger.

[0227] 38306813-114. The method of clause 13 wherein the armour is of a material having a brittle-ductile transition temperature and a re-crystallisation temperature, and wherein during performance of the method the armour is substantially maintained at a temperature above the brittle-ductile transition temperature of the armour material and below the recrystallisation temperature of the armour material.

[0228] 15. The method of clause 13 wherein, in the apparatus of clause 5, the component has a plasma-facing surface and each of the heat pipes has a long axis disposed in a direction substantially parallel to a smooth surface approximating the plasma-facing surface, and wherein receiving heat at the component comprises receiving, from a plasma contained by the plasma confinement device during operation of the system, heat from a heat flux incident on the plasma-facing surface of the component.

[0229] 16. The apparatus of clause 5 wherein the component is one of a plasma-facing component, a divertor, a limiter, a first wall, a shield, a breeder blanket, a portion or segment of any of these, an armour part for any of these or for a portion or segment thereof, or a thermal management component for any of the foregoing.

[0230] 17. The heat pipe of clause 1 wherein the armour comprises a refractory metal or an alloy of a refractory metal.

[0231] 18. The heat pipe of clause 18 wherein the refractory metal comprises tungsten.

[0232] 19. The heat pipe of clause 1 wherein the heat pipe has a working fluid comprising one or more of caesium, potassium, sodium, NaK, and lithium.

[0233] 20. The apparatus of clause 10 wherein the plasma confinement device is one of aa magnetic confinement device, such as a tokamak (spherical or otherwise), a stellarator, a spheromak, a magnetic mirror machine, and a reversed field pinch device; inertial confinement devices, such as indirect drive, direct drive, fast ignition, magneto-inertial fusion devices, and Z-machines; pinch devices, such as a Z-pinch, theta-pinch, or screw-pinch device; and inertial electrostatic confinement devices, such as fusors or polywells.

[0234] 21. The apparatus of clause 5 and further comprising a heat exchanger operatively coupled to a plurality of the heat pipes.

[0235] 38306813-122. The heat pipe of clause 2 wherein the first portion of the heat pipe is proximal to a first end of the heat pipe and the second portion of the heat pipe is proximal to a second, opposite end of the heat pipe.

[0236] 23. A system comprising:

[0237] the apparatus of clause 4, wherein the heat exchanger is configured to carry a flow of coolant; and

[0238] a power-producing subsystem, operatively coupled to the heat exchanger, comprising a turbine configured to be driven by the coolant.

[0239] 24. The heat pipe of clause 2 wherein a first portion of the heat pipe passes through the armour and the or each further portions (e.g., the second or the third portion as described above) of the heat pipe extend away from the armour.

[0240] 25. Apparatus comprising the heat pipe of clause 24 and first and second heat exchangers operatively coupled to the heat pipe, respectively, in vicinities of the second portions of the heat pipe (e.g., at either longitudinal end of the heat pipe). 26. In the heat pipe of clause 2, a method comprising:

[0241] receiving heat from the castellated armour into the heat pipe in a vicinity of the first portion of the heat pipe; and

[0242] conveying at least some of the received heat through the heat pipe to the second portion of the heat pipe.

[0243] 27. A method for thermal management of a component for a plasma confinement device, the component having castellated armour comprising the armour of the heat pipe of clause 2, the method comprising:

[0244] receiving, from the armour of the heat pipe, an input non-uniform heat flux into the first portion of the heat pipe; and

[0245] providing a substantially uniform output heat flux out of the second portion of the heat pipe.

[0246] Further aspects of the present invention are summarised by the following numbered clauses:

[0247] 101. A phase-transition mediated heat pipe attached to and in thermal contact with a plurality of physically distinct pieces or units of a castellated armour.

[0248] 38306813-1102. The heat pipe of clause 101 wherein a first portion of the heat pipe is disposed in a vicinity of the castellated armour and a further portion (e.g., the second or third portion described above) of the heat pipe juts away from the armour.

[0249] 103. The heat pipe of clause 101 partially embedded in the castellated armour.

[0250] 104. The heat pipe of clause 101 having an exterior surface adjacent to an exterior surface of the castellated armour.

[0251] 105. The heat pipe of clause 101 wherein the heat pipe passes through the armour. 106. The heat pipe of clause 101 wherein the pieces are substantially similar to one another.

[0252] 107. The heat pipe of clause 101 wherein the pieces are arrayed (e.g., in a rectilinear array) across a surface of the heat pipe.

[0253] 108. The heat pipe of clause 101 wherein the pieces are arrayed along a length of a portion of the heat pipe.

[0254] 109. The heat pipe of clause 101 wherein each of the pieces comprises a tile, a plate, a block or a monoblock.

[0255] 110. The heat pipe of clause 101 wherein the heat pipe has first and second portions, the castellated armour being attached to the heat pipe exclusively in a vicinity of the first portion.

[0256] 111. The heat pipe of clause 101 wherein the heat pipe is operatively coupled to a heat exchanger in a vicinity of the second portion.

[0257] 112. The heat pipe of clause 101 wherein the castellated armour comprises a refractory metal or an alloy of a refractory metal.

[0258] 113. The heat pipe of clause 112 wherein the refractory metal comprises tungsten. 114. The heat pipe of clause 101 wherein the heat pipe has a working fluid comprising water or a metal.

[0259] 115. The heat pipe of clause 114 wherein the working fluid comprises lithium, sodium, potassium, NaK, or caesium, or any mixture thereof.

[0260] 116. The heat pipe of clause 101 wherein an interlayer is disposed between the heat pipe and the armour.

[0261] 38306813-1117. The heat pipe of clause 116 wherein the heat pipe has an envelope comprising a first material having a first coefficient of thermal expansion (CTE), the armour comprises a second material having a second CTE, and the interlayer comprises one or more materials each having a CTE intermediate between the first and second CTEs.

[0262] 118. The heat pipe of clause 101 wherein the castellated armour is armour for a component of a plasma confinement device.

[0263] 119. Apparatus comprising a plurality of the heat pipes of clause 101 and a component for a plasma confinement device (e.g., for nuclear fusion), wherein the component has armour comprising the armour of the heat pipes.

[0264] 120. The apparatus of clause 119 wherein the armour of the component is wholly or partially integrated into the component.

[0265] 121. The apparatus of clause 119 wherein the armour of the component is distinct from the component.

[0266] 122. The apparatus of clause 119 wherein the component is one of a plasma-facing component, a divertor, a limiter, a first wall, a shield, a breeder blanket, a portion or segment of any of these, armour or an armour part for any of these or for a portion or segment thereof, or a thermal management component for any of the foregoing.

[0267] 123. The apparatus of clause 119 wherein the armour of the component comprises a layer and wherein each of the heat pipes has a long axis substantially parallel to the layer.

[0268] 124. The apparatus of clause 119 wherein the component has a plasma-facing surface, and wherein each of the heat pipes has a long axis substantially parallel to a smooth surface approximating the plasma-facing surface.

[0269] 125. The apparatus of clause 124 wherein the plasma-facing surface of the component is coincident with a surface of the armour.

[0270] 126. The apparatus of clause 119 wherein the component has a plasma-facing surface, and wherein each of the heat pipes follows a contour of a smooth surface approximating the plasma-facing surface.

[0271] 127. The apparatus of 126 wherein the contour comprises one or more straight line segments, curves, or a mixture of these.

[0272] 128. In the heat pipe of clause 102, a method comprising:

[0273] 38306813-1receiving heat into the heat pipe from the castellated armour; and conveying at least some of the received heat through the heat pipe from the first portion of the heat pipe to the second portion of the heat pipe.

[0274] 129. The method of clause 128 wherein receiving heat into the heat pipe comprises receiving heat into the heat pipe contemporaneously from the plurality of pieces.

[0275] 130. Apparatus comprising a heat exchanger operatively coupled to one or more of the heat pipes of clause 101.

[0276] 131. In the apparatus of clause 30, a thermal management method comprising:

[0277] receiving heat at the armour of the one or more heat pipes;

[0278] conveying at least a portion of the received heat to the heat exchanger through the one or more heat pipes; and

[0279] exhausting at least a portion of the conveyed heat from the heat exchanger.

[0280] 132. The method of clause 131 wherein the armour is of a material having a brittle-ductile transition temperature and a re-crystallisation temperature, and wherein during performance of the thermal management method the armour is substantially maintained at a temperature above the brittle-ductile transition temperature of the armour material and below the re-crystallisation temperature of the armour material.

[0281] 133. The method of clause 131 wherein the apparatus of clause 130 is disposed in a plasma confinement device comprising a component having armour comprising the armour of the one or more heat pipes, and wherein receiving heat at the armour of the one or more heat pipes comprises receiving heat at the armour from a plasma contained by the plasma confinement device during operation of the plasma confinement device.

[0282] 134. A system comprising the apparatus of clause 119 and a plasma confinement device wherein the component is disposed.

[0283] 135. The system of clause 134 wherein the plasma confinement device is one of a magnetic confinement device, such as a tokamak (spherical or otherwise), a stellarator, a spheromak, a magnetic mirror machine, and a reversed field pinch device; inertial confinement devices, such as indirect drive, direct drive, fast ignition, magneto-inertial

[0284] 38306813-1fusion devices, and Z-machines; pinch devices, such as a Z-pinch, theta-pinch, or screwpinch device; and inertial electrostatic confinement devices, such as fusors or polywells.

[0285] 136. The system of clause 134 wherein the plasma confinement device has, at least approximately, a toroidal, spherical, circular or other geometric symmetry around a central axis and wherein the component, as disposed in the plasma confinement device, has a surface nearest to the central axis, and wherein each of the heat pipes has a long axis substantially parallel to a smooth surface approximating the surface nearest to the central axis.

[0286] 137. The system of clause 134 wherein the component, as disposed in the plasma confinement device, has a surface facing a plasma confinement region of the plasma device, and wherein each of the heat pipes has a long axis substantially parallel to a smooth surface approximating the surface of the component facing the plasma confinement region of the plasma device.

[0287] 138. In the system of clause 134, a method comprising:

[0288] operating the device to confine a plasma therein;

[0289] generating heat from the confined plasma;

[0290] providing a portion of the generated heat to the armour through one or more of conduction, convection, or radiation; and

[0291] conveying at least a portion of the heat flux incident on the armour through the heat pipes.

[0292] 139. The method of clause 138 wherein the providing comprises providing a heat flux incident on the armour, the heat flux comprising heat radiated from the plasma onto the armour.

[0293] 140. A method for thermal management of a component for a plasma confinement device, the component having castellated armour comprising the armour of the heat pipe of clause 101, the method comprising:

[0294] a. receiving, from the armour of the heat pipe, an input non-uniform heat flux into a first part of the heat pipe; and

[0295] b. providing a substantially uniform output heat flux out of a second part of the heat pipe.

[0296] 38306813-1141. The method of clause 140 wherein the receiving comprises receiving the input heat flux in a direction substantially perpendicular to a long axis of the heat pipe.

[0297] 142. The method of clause 140 wherein the first and second parts are, respectively, first and second segments of the heat pipe disposed at opposite ends of the heat pipe, the heat pipe being attached to the armour in a vicinity of the first segment, and wherein the receiving comprises receiving an input heat flux distributed non-uniformly over the first segment, and the providing comprises providing an output heat flux distributed substantially uniformly over the second segment.

[0298] 38306813-1

Claims

CLAIMS:

1. An apparatus, comprising:a component, comprising a plurality of physically distinct units arranged in a castellated structure; anda heat pipe, comprising:a first portion, each unit of the plurality of physically distinct units being affixed to and in thermal contact with the first portion; anda second portion configured to be operatively coupled to a heat exchanger,wherein the first portion of the heat pipe passes through each unit of the plurality of physically distinct units, andwherein the first portion has a first surface area, and the second portion has a second surface area, the second surface area being greater than the first surface area.

2. An apparatus according to claim 1, wherein all of said units are substantially similar to one another in form.

3. An apparatus according to claims 1 or 2, wherein the second surface area is greater than the first surface area by a factor of at least 2.

4. An apparatus according to any one of claims 1 to 3, wherein the second portion comprises a plurality of cooling fins or baffles.

5. An apparatus according to claim 4, wherein each cooling fin or baffle is at least partially embedded within the heat pipe.

6. An apparatus according to any one of the preceding claims, wherein the plurality of physically distinct units comprises ten or more units.

7. An apparatus according to any one of the preceding claims, wherein the plurality of physically distinct units comprises thirty or more units.

8. An apparatus according to any one of the preceding claims, wherein a melting point of the component, at 0.1 MPa, is greater than 1100°C.38306813-19. An apparatus according to any one of the preceding claims, wherein a main constituent of a material of the component is a metallic element, the metallic element having an atomic number greater than or equal to 40.

10. An apparatus according to any one of the preceding claims, wherein the component comprises a refractory metal or an alloy of a refractory metal.

11. An apparatus according to claim 10, wherein the refractory metal comprises tungsten.

12. An apparatus according to any one of the preceding claims, wherein the heat pipe is operative at temperatures in excess of 200°C.

13. An apparatus according to any one of the preceding claims, wherein at least a portion of the first portion of the heat pipe is at least partially embedded in the castellated structure.

14. An apparatus according to any one of the preceding claims, wherein the heat pipe has an elongate channel and the second portion of the heat pipe includes a longitudinal end portion of the elongate channel.

15. An apparatus according to any one of the preceding claims, wherein the heat pipe and / or the channel follow a contour of a smooth external surface of the component.

16. An apparatus according to any one of the preceding claims, further comprising one or more heat exchangers operatively coupled to the second portion of the heat pipe.

17. An apparatus according to claim 16, when dependent on claim 14, wherein a first heat exchanger is operatively coupled to a first longitudinal end portion of the elongate channel and a second heat exchanger is operatively coupled to a second longitudinal end portion of the elongate channel.

18. An apparatus according to any one of the preceding claims, wherein the component is or has a castellated armour.38306813-119. An apparatus according to any one of the preceding claims, wherein said units are arranged in a rectilinear array.

20. An apparatus according to claim 19, wherein the rectilinear array is any one of: a rectangular array, a square array, a hexagonal array, or a triangular array.

21. An apparatus according to any one of the preceding claims, in which the heat pipe comprises a manifold section.

22. An apparatus according to claim 21, wherein the manifold section is arranged adjacent to the second portion of the heat pipe.

23. An apparatus according to any one of the preceding claims,wherein the plurality of physically distinct units of the component comprises a plurality of sets of such units, each set comprising a plurality of physically distinct units arranged in a castellated structure; andwherein the apparatus comprises a plurality of heat pipes, each heat pipe being associated with a respective one of the sets of units, each heat pipe comprising a first portion and a second portion, each unit of the respective associated set being affixed to and in thermal contact with said first portion, and said second portion of each heat pipe being configured to be operatively coupled to a heat exchanger.

24. An apparatus according to claim 23, wherein the heat pipes of the plurality are arranged in an array, each heat pipe forming at least a portion of a row or column of said array.

25. An apparatus according to any one of claims 23 or 24 and further comprising a heat exchanger, each heat pipe being operatively coupled to the heat exchanger at the second portion of said heat pipe.

26. An apparatus according to any one of claims 23 or 24, comprising a plurality of heat exchangers, wherein each heat pipe is operatively coupled to at least one of the plurality of heat exchangers at a respective second portion of said heat pipe.38306813-127. An apparatus according to any one of the preceding claims, wherein the or each heat pipe has a working fluid comprising: water, or, any one of lithium, sodium, potassium, a sodium-potassium alloy, caesium, or any mixture of the foregoing metals.

28. An apparatus according to any one of the preceding claims, wherein:the or each heat pipe is affixed to the component by an interlayer;the or each heat pipe has an envelope comprising a first material having a first coefficient of thermal expansion, CTE;the component comprises a second material having a second CTE; and the interlayer comprises at least one material having a CTE intermediate between the first and second CTEs.

29. A plasma confinement device comprising the apparatus of any one of claims 1 to 28, wherein the component of the apparatus comprising the plurality of physically distinct units arranged in a castellated structure is a component of the plasma confinement device.

30. A plasma confinement device according to claim 29, wherein the component is any of: a shielding layer for the plasma confinement device; a plasma facing component; a divertor; a limiter; a first wall component; a breeder blanket; a portion of any of the foregoing; an armour for any of the foregoing or for a portion thereof; or a thermal management component for any of the foregoing.

31. A plasma confinement device according to claims 29 or 30, being any of: a magnetic confinement device; a tokamak; a stellarator; a spheromak; a spherical tokamak; a magnetic mirror machine; a reversed field pinch device; a Z-machine; a Z-pinch device; a theta-pinch device; a screw pinch device; a fusor; or a polywell.

32. A plasma confinement device according to any one of claims 29 to 31, wherein the or each heat pipe extends radially with respect to a central axis of a plasma confinement chamber of the plasma confinement device.

33. A system comprising:a heat source; andthe apparatus of any one of claims 1 to 28 thermally coupled to the heat source.38306813-134. A system according to claim 33, wherein the apparatus comprises one or more heat exchangers and one or more heat pipes, wherein the one or more heat pipes includes the heat pipe recited in claim 1, wherein the or each heat exchanger is operatively coupled to at least one of the heat pipes at the respective second portion or portions thereof.

35. A system according to claim 34, wherein the or each heat exchanger is configured to carry coolant flow and the system further comprises a turbine configured to be driven by said coolant flow to generate electrical power.

36. A thermal management method applied to the apparatus of any one of claims 1 to 28, the method comprising:receiving, by the heat pipe or heat pipes, thermal flux from a plurality of the physically distinct units of the component contemporaneously; and conveying thermal energy from at least a portion of the received thermal flux along or through the heat pipe or heat pipes towards a heat exchanger.

37. A method according to claim 36, wherein a magnitude of the thermal flux received by the or each heat pipe from said plurality of physically distinct units varies with position across the first portion of said heat pipe.

38. A method according to claim 36 or 37, wherein conveying at least a portion of the conveyed thermal energy towards a heat exchanger comprises conveying at least a portion of the conveyed thermal energy into a heat exchanger, wherein the heat exchanger is operatively coupled to the second portion of the or each heat pipe.

39. A method according to claim 38, wherein the thermal energy conveyed to the heat exchanger is provided as a thermal flux to the heat exchanger, and wherein the thermal flux across the second portion of the or each heat pipe is distributed more uniformly than the thermal flux received by the heat pipe is distributed across the first portion of the or each heat pipe.38306813-140. A method according to claim 39, wherein the thermal flux to the heat exchanger is distributed substantially uniformly across the second portion of the or each heat pipe.

41. A method according to any of claims 38 to 40, wherein the method further comprises:conveying at least a portion of the received thermal energy into the heat exchanger.

42. A method according to claim 41, further comprising:exhausting, using a coolant carried by the heat exchanger, at least a portion of the thermal energy conveyed into the heat exchanger.

43. A method according to any one of claims 36 to 42, wherein the component comprises a material having a brittle-ductile transition temperature, DBTT, and a recrystallization temperature, RT, and wherein, during said method steps, the component is maintained at a temperature between DBTT and RT.

44. A method according to claim 43, wherein the heat pipe is a variable conductance heat pipe.

45. A method according to claim 43 or 44, further comprising:adjusting operating parameters of the heat exchanger to maintain the component at a temperature between DBTT and RT.

46. A method according to any one of claims 36 to 45, wherein the component of the apparatus comprising the plurality of physically distinct units arranged in a castellated structure is a component of a plasma confinement device, and further comprising:operating the plasma confinement device to generate a plasma; and receiving, by the component, energy from the plasma.

47. A power generation method using the system of claim 35, the method comprising:receiving, by the or each heat pipe, at least a portion of a thermal flux from the heat source;conveying thermal energy from at least a portion of the received thermal flux along or through the or each heat pipe and into the or each heat exchanger to heat coolant in said heat exchanger; and38306813-1driving the turbine to turn and generate electrical power using flow of the heated coolant.38306813-1

Images