Thermal management apparatus and method

Abstract

An apparatus comprising: a component comprising a plurality of physically distinct units; and a heat pipe in thermal contact with each unit of the plurality of physically distinct units. The heat pipe comprises: a channel; a first portion affixed to each unit of the plurality of physically distinct units; and a second portion opposing the first portion in a direction transverse to a direction defining a major dimension of the channel. The second portion is 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 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 a channel in the sense that the dimension of the channel (a minor dimension) in a direction between (or

[0009] 38305906-1connecting) opposing sides of the wick is much smaller than the dimension of the channel (a major dimension) 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] 38305906-1A 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] 38305906-1to 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, comprising: a component comprising a plurality of physically distinct units; and a heat pipe in thermal contact with each unit of the plurality of physically distinct units. The heat pipe comprises a channel, a first portion affixed to each unit of the plurality of physically distinct units, and a second portion opposing the first portion in a direction transverse to a direction defining a major dimension of the channel. The second portion is configured to be operatively coupled to a heat exchanger. The first portion may be configured as an evaporator portion of the heat pipe (e.g., functionally adapted to promote evaporation of the working fluid). The second portion may be configured as the condenser portion of the heat pipe (e.g., specially adapted to promote condensation of the working fluid). In a specific example, the first and second portions are spaced apart from one another by a distance corresponding to a minor dimension of the channel (e.g., spaced apart by a distance equal to the thickness of the heat pipe).

[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] In some examples, the second portion comprises a plurality of fins. Each fin may be at least partially embedded within the heat pipe.

[0025] 38305906-1In some examples, 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. A main constituent of a material comprising the component may be a metallic element, the metallic element having an atomic number greater than or equal to 40. A body of the component may comprise or consist of a refractory metal (e.g., tungsten) or an alloy of a refractory metal (e.g., a tungsten alloy).

[0027] The heat pipe may be designed to be operative at temperatures in excess of 200°C.

[0028] The component may be or have a castellated armour.

[0029] In some examples, the units are arranged to form a castellated structure.

[0030] In some examples, the units are arranged in a rectilinear array, such as any one of: a rectangular array, a square array, a hexagonal array, or a triangular array.

[0031] The heat pipe and / or the channel of the heat pipe may follow a contour of a smooth external surface of the component.

[0032] In some examples, the apparatus further comprises one or more heat exchangers operatively coupled to the second portion of the heat pipe.

[0033] In some examples, the apparatus comprises a plurality of heat pipes each in thermal contact with the component at a respective plurality of physically distinct units of the component. In such examples, each heat pipe comprises a channel, a first portion affixed to each unit of the respective plurality of physically distinct units, and a second portion opposing the first portion in a direction transverse to a dimension defining the major dimension of the respective channel. The second portion of each heat pipe may be configured to be operatively coupled to a heat exchanger.

[0034] In some examples, the plurality of heat pipes are arranged in an array, each heat pipe forming at least a portion of a row or column of said array.

[0035] 38305906-1In some examples, the apparatus comprises a heat exchanger operatively coupled to each heat pipe at the respective second portion of said heat pipe.

[0036] 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.

[0037] The or each heat pipe may be interposed between the heat exchanger and the component so as to space the heat exchanger and the component apart in a direction transverse to a direction defining the major dimension of the channel.

[0038] 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.

[0039] 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 material having a CTE intermediate between the first and second CTEs. The CTE may be measured under standard conditions and / or at operating temperature.

[0040] According to a second aspect of the present invention, there is provided a plasma confinement device, comprising the apparatus according to the first aspect.

[0041] 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 thereof; an armour for any of the foregoing or a portion thereof; or a thermal management component for any of the foregoing.

[0042] The 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.

[0043] 38305906-1According 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.

[0044] The apparatus of the system may comprise 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.

[0045] The or each heat exchanger of the system 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.

[0046] 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 the plurality of physically distinct units of the component contemporaneously; conveying thermal energy from at least a portion of the received thermal flux along the channel of the or of each heat pipe; and conveying at least a portion of the conveyed thermal energy towards a heat exchanger in a direction transverse to a direction defining the major dimension of the channel of the or each heat pipe.

[0047] A magnitude of 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.

[0048] 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.

[0049] The 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 heat pipe is distributed more uniformly than the thermal flux received by the heat pipe is distributed across the first portion of the heat pipe.

[0050] 38305906-1The thermal flux at or to the heat exchanger is distributed substantially uniformly across the second portion of the heat pipe.

[0051] In some examples, the method further comprises exhausting, using a coolant carried by the heat exchanger, at least a portion of the thermal energy conveyed into the heat exchanger.

[0052] The component may comprise 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.

[0053] The method may further comprise adjusting operating parameters of the heat exchanger to maintain the component at a temperature between DBTT and RT.

[0054] The method may further comprise operating a plasma confinement device to generate a plasma; and receiving, by the component, energy (e.g., thermal energy) from the plasma.

[0055] According to a fifth aspect of the present invention, there is provided a power generation method using the system according to the second 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 the channel of the or of each heat pipe and into the or each heat exchanger in a direction transverse to a direction defining a major dimension of said channel to heat coolant in said heat exchanger; and driving a turbine to turn and generate electrical power using flow of the heated coolant.

[0056] Brief description of the Drawings

[0057] Figures 1 and 2 are schematic illustrations of a heat pipe.

[0058] Figure 3 is a pressure-temperature phase diagram for a working fluid.

[0059] Figure 4A is a schematic illustration of a thermal management apparatus in crosssection.

[0060] Figure 4B is a perspective view of the thermal management apparatus.

[0061] Figure 5 is a schematic illustration of a thermal management apparatus in cross-section. Figure 6 is a schematic illustration of a thermal management apparatus in cross-section.

[0062] 38305906-1Figure 7 is a schematic illustration of a plasma confinement device in cross-section. Figures 8A and 8B are schematic illustrations of a divertor of a plasma confinement device.

[0063] Figures 9A to 9B are schematic illustrations of a thermal management apparatus in plan view.

[0064] Figure 10 is a method flow diagram.

[0065] Figure 11 is a schematic illustration of a power generation system.

[0066] Figure 12 is a method flow diagram.

[0067] Detailed description

[0068] 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.

[0069] 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.

[0070] 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 strikes the component can be transformed into a more spatially uniform thermal flux or energy profile at the heat exchangers. 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.

[0071] In particular, the channel of the heat pipe is oriented, with respect to the component and heat exchanger, such that thermal energy extracted from a hot spot at the component is conveyed along a direction defining a major dimension of the channel away from the hot

[0072] 38305906-1spot as well as being conveyed in a direction transverse to the direction defining the major dimension of the channel and into the heat exchanger.

[0073] As a result, the disclosed thermal management apparatus spreads the thermal energy received by the component in a vicinity of a hot spot over a larger area or volume at the heat exchanger. This promotes thermal extraction at the heat exchanger side of the apparatus at lower pumping powers, thereby simplifying operation of the heat exchanger.

[0074] In some examples, the surface area of contact between the heat exchanger and the heat pipe (e.g., approximately the surface area of the cooling fins 618 shown in Figure 6 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 4A) 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.

[0075] 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 arranged in between the heat exchanger and the heat pipe.

[0076] 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).

[0077] The 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).

[0078] 38305906-1The 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.

[0079] Figure 4A 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. The heat pipe includes a channel 420, which may be elongate. The channel has a plurality of dimensions, which dimensions include a major dimension (e.g., a length) and a minor dimension (e.g., a thickness). The major dimension is greater than the minor dimension. Although not visible in cross-section, the channel also includes a further dimension (e.g., a width). The further dimension is equal to or less than the major dimension but may be smaller, greater, or equal to the minor dimension. The heat exchanger and component are spaced apart in a direction defining the minor dimension (e.g., a thickness direction).

[0080] As shown, the heat pipe spaces apart the heat exchanger 406 and the component 402 in a direction transverse to a direction defining a major dimension of the channel. In a specific example, the channel is elongate and the heat exchanger 406 and the component 402 are spaced apart by the heat pipe in a direction transverse to the elongate channel. In Figure 4A, 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 of any known type.

[0081] 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 4A. 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 by the arrows within channel 420 in the figure. It will be understood that these arrows represent a simplified view of the flow of thermal energy.

[0082] 38305906-1The 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 halfmaximum, FWHM, of the temperature profile at the component. For asymmetric hot spots, an average FWHM can be used.

[0083] 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 4A) 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.

[0084] 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 region of greatest evaporation of the working fluid (denoted in Figure 4A 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.

[0085] 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).

[0086] In the example of Figure 4A, the evaporation rate of working fluid within 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

[0087] 38305906-1component (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.

[0088] The heated working gas (i.e. , the vaporised working liquid) moves through the heat pipe 404 away from the hot spot 412 along a direction defining a major dimension of the channel of the heat pipe 404, and also moves through the heat pipe 404 towards the heat exchanger 406 in a direction transverse to the direction defining the major dimension of the channel (or, in other words, in a direction defining the minor dimension of the channel).

[0089] In a specific example, the channel is elongate and the working gas moves away from the hot spot along the length of the channel and towards the heat exchanger in a direction across the thickness direction of the channel. As another example, if the heat pipe is of a planar design rather than a tubular design (e.g., where the heat pipe is a vapour chamber), the working gas spreads out across the planar area of the channel and moves toward the heat exchanger in a direction across the thickness direction of the channel.

[0090] At heat exchanger 406, the working gas condenses and releases its latent heat of condensation, which latent heat is extracted by the heat exchanger.

[0091] In this way, thermal energy is transferred from the hot spot 412 within the component 402 to the heat exchanger. Notably, as thermal energy is conveyed along a direction defining the major dimension of the channel (e.g., along the elongate channel) as it is conveyed to the heat exchanger, the thermal energy originating from the hot spot 412 is spread over a greater area at the heat exchanger 406. The greater area is denoted by the grey region 428 within the wick 408 of the heat pipe in the vicinity of heat exchanger 406.

[0092] In some examples (not shown), there may be a plurality of hot spots at the component 402 and / or heat pipe 404. This may arise, for example, if the position of the peak in the

[0093] 38305906-1thermal 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.

[0094] Returning to Figure 4A 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 component 402a and 402i are labelled in the figure.

[0095] 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).

[0096] The 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, ora monoblock. Each unit has a thickness (in a thickness direction towards the heat pipe), a width and a length (in a plane orthogonal to the thickness direction).

[0097] 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.

[0098] 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

[0099] 38305906-1portion 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 being are co-located with the spaced ridgeways 418. The first portion 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.

[0100] The heat pipe 404 further includes a second portion 426, which is operatively coupled to the heat exchanger 406. The second portion opposes (i.e. , faces opposite to) the first portion in a direction transverse to a direction defining the major dimension of the channel of the heat pipe. That is, the first portion is on the other side of the heat pipe in the transverse direction of the channel (rather than in the longitudinal direction of the channel). In a specific example, the channel is elongate and the first portion opposes the second portion in a direction transverse to the elongate channel. The first and second portion of the heat pipe may both extend along (i.e., in the direction defined by) a direction defining the major dimension of the channel.

[0101] 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.

[0102] In use, the evaporator portion of the heat pipe 404 may include at least part of or all of the first portion 424.

[0103] In use, the condenser portion of the heat pipe may include at least part of or all of the second portion 426.

[0104] A perspective view of the thermal management apparatus from Figure 4A but showing three units 402a-c, rather than nine units, is shown in Figure 4B. The channel 420 is shown as being rectangular in cross-section but it will be understood that other shapes in cross-section are possible. A coolant line 430 that extends through the heat exchanger is also shown.

[0105] 38305906-1In 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.

[0106] 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). The CTE may be measured under standard conditions and / or at operating temperature.

[0107] The heat pipe 404 may be any known type of heat pipe. The heat pipe channel 420 may be elongate or planar; if elongate, it may be straight or include one or more bends, which may be made up of one or more straight and / or sections. The external shape of the heat pipe may be made suitable to the particular application or installation; e.g., it may be smooth or include undulations. The heat pipe and / or its channel (if elongate) 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.).

[0108] In an alternative embodiment, as shown in Figure 5, the heat pipe 504 is partially embedded within the component 502. For simplicity, the component in Figure 5 includes five units 502a-502e rather than nine units, as depicted in Figure 4A. It will be understood that the component may include any number (e.g., a multiplicity) of units.

[0109] In Figure 5, the attachment portions between the heat pipe 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.

[0110] 38305906-1In Figures 4A, 4B, and 5, the heat pipe 404 spans across the entirety of the component (i.e., units 402a-i). In some examples, the heat pipe 504 may span across a majority (i.e., more than 50%, 60%, 70%, 80%, 90%, or 95%) of the component.

[0111] The channels 420 in Figures 4A, 4B, and 5 are shown as being straight but in practice, the channels and / or the heat pipe 404 may include one or more bends. The bends may be contained within a plane that is equidistant from the heat exchanger and component or contained within a plane at an oblique angle thereto.

[0112] If the channel includes one or more bends, the major dimension of the channel is a total length of the channel, following those one or more bends. The direction defining the major dimension of the channel will, therefore, define a plurality of directions, which vary along the length of the channel. “Along” the channel and “longitudinal” should be interpreted accordingly. Where the bends of the heat pipe lie substantially in a plane, then the direction transverse to the direction defining the major dimension of the channel, namely, through the thickness of the channel, remains the same regardless of the bends. For example, in an x-y-z Cartesian coordinate system, if the bends of the heat pipe are in a plane defined as the x-y plane, then transverse direction through the thickness of the heat pipe is along the z axis.

[0113] Figure 6 is a schematic illustration of a thermal management apparatus 600, according to an embodiment. The thermal management apparatus comprises a component 602 having a plurality of units 602a-e, a heat pipe 604, and a heat exchanger 606. The thermal management apparatus may be substantially as described in relation with Figures 4A, 4B, and 5, but, in this variant, the apparatus comprises a plurality of spaced fins 618 for ensuring efficient thermal transfer between the heat pipe 604 and the heat exchanger 606.

[0114] As shown in Figure 6, the fins 618 are embedded within the heat pipe at its second portion and extend into the heat exchanger 606. In alternative examples, the fins are affixed to and extend away from a peripheral surface of the heat pipe and into the heat exchanger 606. The fins may have any shape in cross-section (e.g., circles, squares, rectangles). The fins may be integrally formed on (i.e., form part of) the envelope of the heat pipe (e.g., through casting or additive manufacturing techniques). Alternatively, the

[0115] 38305906-1fins may be manufactured separately from the heat pipe and subsequently affixed onto the envelope (e.g., by welding or brazing).

[0116] In the example shown, the fins 618 are evenly spaced but in other examples (not shown), the fins may have a non-uniform spacing.

[0117] As shown, the heat exchanger 606 comprises a plurality of coolant lines 630. Each coolant line extends in between two adjacent fins 618. In an alternative example (not shown), the heat exchanger comprises a hollow pressure vessel into which the fins 618 extend. Coolant may then flow through the inside of the pressure vessel and establish direct contact with the fins.

[0118] As the fins 618 extend across the interface between the heat exchanger 606 and the heat pipe 604, they also advantageously provide a degree of mechanical stabilisation to the thermal management apparatus.

[0119] 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.

[0120] The plasma confinement device 700 further 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 and 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.

[0121] 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

[0122] 38305906-1outward 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.

[0123] 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.

[0124] Figure 8A 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.

[0125] It is noted that Figure 8A 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.

[0126] 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 4A-4B, 5 and 6 respectively) and a heat exchanger 806 operatively coupled to the second portion of the heat pipe.

[0127] The inboard divertor surface 710a comprises a plurality of constituent units 802a-i (e.g., blocks, monoblocks, plates or tiles). The divertor is one example for component 402, 502. Further detail of the units is provided above in relation to Figures 4A, 4B and 5 and, for brevity, is not repeated here.

[0128] The arrows F in the figure denote the expected direction of the incident thermal flux originating from the plasma 740 (in Figure 8A, only the lower portion of plasma 740 is shown) during operation. As shown, the thermal flux impinges 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.

[0129] 38305906-1The 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 F from striking the heat pipe 804 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 (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).

[0130] The arrows F in Figure 8A 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 9A-9B) 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 8A, such as in a direction substantially perpendicular to the or a longitudinal direction of the heat pipe or heat pipes.

[0131] Figure 8B schematically illustrates a close-up view of a thermal management apparatus 810, generally similar to apparatus 800 from Figure 8A but situated at outboard divertor surface 710c. Divertor surface 710c comprises units (e.g., monoblocks of tungsten or other refractory metal) 812a-i in a castellated formation. For simplicity, only units 812a and 812i are labelled in the figure. Nine units are illustrated but it will be understood that there may be more or fewer. The units are affixed to heat pipe 814 which, in turn, is

[0132] 38305906-1affixed and operatively coupled to heat exchanger 816, which comprises a heat sink body through which coolant line 818 runs. In operation, the units receive incident thermal flux F from the plasma. Heat is transferred in the minor direction across the heat pipe 814 from the units 812a-i to the heat exchanger 816. Coolant flows through coolant line 818, for example in the direction illustrated by the arrows shown inside coolant line 818 (it being understood that the coolant may be designed to flow in either direction through coolant line 818). The flowing coolant carries heat away from heat exchanger 836 to outside the plasma confinement device for further use (e.g., to generate electric power) and / or exhaust. For ease of maintenance, the divertor surface units 812a-i and heat pipe 814 can be configured together as a single replaceable assembly 820.

[0133] Figure 9A and 9B show plan views of, respectively, thermal management apparatuses 900 and 910 according to specific embodiments. In Figure 9A, thermal management apparatus 900 includes a plurality of physically distinct component units 902a-l in a castellated structure, a plurality of heat pipes 904, and a heat exchanger 906. In Figure 9B, thermal management apparatus 910 includes a plurality of physically distinct component units 912a-l in a castellated structure, a plurality of heat pipes 914, and a plurality of heat exchangers 916a-c. In these figures, the units 902a-l, 912a-l, each heat pipe 904, 914, and heat exchangers 906, 916a-c may be substantially as described in relation to Figures 4A, 4B, 5, ad 6. The difference is that the apparatuses each include a plurality of heat pipes, which are operatively coupled either to a shared common heat exchanger (as in Figure 9A) or to respective individual heat exchangers (as in Figure 9B).

[0134] Referring in more detail to Figures 9A and 9B, the thermal management apparatuses 900 and 910 each include a plurality of heat pipes (respectively, 904 and 914) that are arranged into an array (respectively, 908 and 918), which may be termed a heat pipe array. In Figures 9A and 9B, there are three heat pipes shown, but it will be understood that the array can include any number of heat pipes. In Figures 9A and 9B, the heat pipes are also shown as rectangular in shape, but it will be understood that other shapes (e.g., square) are possible.

[0135] There may or may not be a spacing between each row and / or column of the heat pipe array.

[0136] 38305906-1In Figure 9A, each heat pipe 904 is operatively coupled to a common heat exchanger 906. In Figure 9B, each heat pipe 914 is operatively coupled to a respective one heat exchanger 916a, 916b, 916c.

[0137] Each heat pipe 904, 914 in Figures 9A and 9B is associated with a respective set (denoted 908a-c, 918a-c) of units 902a-i, 912a-i. For simplicity, only sets 908a and 908c are labelled in Figure 9A, and only set 918b is labelled in Figure 9B. The units included in each of these sets is shown by the dotted lines in the figures. For thermal management apparatuses 910, 920 that include a plurality of heat pipes, 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).

[0138] 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 of the component). For 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).

[0139] In the heat pipe arrays of Figure 9A and 9B, each heat pipe 904, 914 forms a row or column of the heat pipe array. The plurality of physically distinct units 902a-i, 912a-i 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 908a, 908b, 908c, 918a, 918b, 918c of units forming a row or column of the rectilinear array. The rectilinear arrays in Figure 9A and 9B are rectangular but, alternatively, the array may be square, hexagonal, or triangular, for example. It will be understood that the component may comprise any number of the units 902a-l, 912a-l in any arrangement.

[0140] The heat pipes (and if applicable their elongate channels) in Figures 9A to 9B 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.

[0141] 38305906-1Combinations of the thermal management apparatus 900, 910 shown in Figures 9A and 9B are possible. For example, the apparatus may include a plurality of heat exchangers, with a subset of those heat exchangers being associated with one respective heat pipe, and another subset being associated with a plurality of heat pipes.

[0142] In some examples, the component (e.g., components 402, 502 from, respectively, Figures 4A-4B and Figure 5) 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 8A, the component is the divertor 710 (or, alternatively, the inboard divertor surface 710a), and the units 802a-i are the castellated armour. Likewise, in the example of figure 8B, the component is the outboard divertor surface 710c, and the units 812a-l are the castellated armour.

[0143] 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.

[0144] In 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.

[0145] 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.

[0146] 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).

[0147] 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. Tungsten and tantalum are examples

[0148] 38305906-1of material that are resistant both to heat and to the high-energy neutrons emitted by, for example, a deuterium-tritium fusion plasma.

[0149] 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.

[0150] 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 comprise 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 equal 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).

[0151] Operation of any of the thermal management apparatuses from Figure 4A, 6, 8A, 8B, 9A and 9B is now described with reference to Figure 10.

[0152] Method 1000 comprises steps 1002 through 1012. In step 1002, the heat pipe receives a thermal flux or energy from a plurality of physically distinct units of the component contemporaneously. 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.

[0153] 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).

[0154] 38305906-1In step 1004, at least a portion of the energy from the received thermal flux is conveyed along or through a direction defining a major dimension of the channel (e.g., an elongate channel) of the heat pipe.

[0155] In step 1006, at least a portion of the conveyed thermal energy is conveyed towards a heat exchanger (e.g., heat exchanger 406, 606, 806, 906) in a direction transverse to a direction defining the major dimension of the channel (e.g., transverse to the elongate channel of the heat pipe). It will be understood that steps 1004 and 1006 may take place contemporaneously.

[0156] The combination of steps 1004 and 1006 helps to spread the heat flux that the heat exchanger receives over a larger area or volume, which promotes thermal extraction at lower pumping powers. That is, the thermal flux 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.

[0157] 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 example, 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).

[0158] In optional step 1008, a portion of the energy from the received thermal flux is conveyed into the heat exchanger in a direction transverse to a direction defining the major dimension of the channel (e.g., in a direction transverse to the elongate channel).

[0159] 38305906-1In optional step 1010, 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 to which the heat pipe is operatively coupled.

[0160] The coolant (or heat exchange fluid) 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 the coolants are also possible.

[0161] If the thermal management apparatus includes a plurality of heat pipes, then the method of Figure 10 may apply to each of these plurality of heat pipes and their corresponding heat exchanger 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.

[0162] 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.

[0163] In optional step 1012, 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.

[0164] 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 (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).

[0165] 38305906-1In some examples, the thermal management apparatus further comprises a controller (not shown) 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., feedback loop) with the controller.

[0166] The disclosed thermal management apparatus is particularly useful in systems with a heat source that emits high thermal fluxes (e.g., greater than 1MWm-2). An example system is a plasma confinement device, where thermal fluxes can be greater than lOMWrrr2and 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.

[0167] 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.

[0168] In a plasma-confinement device, the apparatus may comprise any one of more of the following:

[0169] • a component (e.g., component from Figure 4A, 5, or 9), 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 confinement 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 a portion thereof; or a thermal management component for any of the foregoing.

[0170] • one or more heat pipes, such as:

[0171] 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

[0172] 38305906-1comprising 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.

[0173] o One or more wickless heat pipes. The heat pipe can be an oscillating or thermosiphon type heat pipe;

[0174] • The structural material for the heat exchanger may be a V-alloy, steel, or SiC.

[0175] • The coolant for the heat exchanger may be, or comprise, water, helium, or carbon dioxide. Other coolants are, however, envisaged.

[0176] SiC is a particularly useful wick for plasma confinement devices, as 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.

[0177] 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).

[0178] More 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.

[0179] 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.

[0180] 38305906-1In some examples, the component and the heat pipe form a replaceable unit 820, which can be mounted and unmounted from the heat exchanger.

[0181] Figure 11 is a schematic illustration of a power generation system 1100. The system includes a heat source 1102, the thermal management apparatus 400, 600, 800, 810, 910, 920 described above thermally coupled to the heat source, and a turbine 1106. The turbine is operatively coupled to the heat exchanger 506 of the apparatus. In some examples, the system includes any one of the plasma confinement devices referred to above. In general, there may be a plurality of turbines operatively coupled to each heat exchanger. In some examples, the system 1100 is or includes any one of the plasma confinement devices referred to above.

[0182] Figure 12 is a flow diagram of a power generation method 1200 carried out by power generation system 1100.

[0183] In step 1202, one or more heat pipes receive at least a portion of a thermal energy emitted by 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.

[0184] Prior to or contemporaneously with step 1202, 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.

[0185] In step 1204, at least a portion of the received thermal energy is conveyed along the direction defining the major dimension of the channel (e.g., along or through the elongate channel) of each or the heat pipe and into the or each heat exchanger in a direction transverse to said direction defining the major dimension of the channel (e.g., transverse to said elongate channel). Coolant carried by the heat exchanger is heated up in step 1204.

[0186] 38305906-1In step 1206, a turbine is driven to turn by the flow of the heated coolant in order to generate electrical power.

[0187] 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.

[0188] Aspects of the present invention are summarised by the following numbered clauses:

[0189] 1. A phase-change mediated heat pipe attached to and in thermal contact with a plurality of physically distinct pieces of a castellated armour, the heat pipe having first and second heat transfer surfaces disposed on opposite sides of a long axis of the heat pipe, at least one of the first and second surfaces or a mean surface therebetween being substantially parallel to the long axis, the heat pipe being attached to the armour in a vicinity of the first surface.

[0190] 2. The heat pipe of clause 1 operably coupled to a heat exchanger in a vicinity of the second surface.

[0191] 3. The heat pipe of clause 1 wherein the heat pipe comprises an envelope and a wick, the envelope including the first and second surfaces, the wick running along the long axis.

[0192] 4. The heat pipe of clause 1 wherein the pieces are substantially similar to one another in form.

[0193] 5. The heat pipe of clause 1 wherein the pieces are disposed in a rectilinear array on the first surface.

[0194] 6. The heat pipe of clause 5 wherein the rectilinear array is one of a rectangular array, a hexagonal array, or a triangular array.

[0195] 7. A method comprising:

[0196] 38305906-1receiving heat into the heat pipe of clause 1 from the armour at the first surface; and

[0197] distributing at least a portion of the received heat substantially uniformly over the second surface.

[0198] 8. The method of clause 7 wherein the receiving comprises receiving heat distributed nonuniformly over the first surface.

[0199] 9. The method of clause 8 wherein the receiving comprises receiving heat concentrated in a vicinity of a point on the first surface.

[0200] 10. The method of clause 7 wherein the distributing comprises conveying the portion of the received heat through the heat pipe from the first surface to the second surface. 11. The method of clause 7 and further comprising transferring at least a portion of the conveyed heat to a heat exchanger operatively coupled to the heat pipe at the second surface.

[0201] 12. The method of clause 11 wherein transferring comprises transferring the heat in a direction substantially perpendicular to the long axis of the heat pipe.

[0202] 13. The method of clause 12 wherein the transferring comprises transferring a substantially uniform heat flux across the second surface.

[0203] 14. The method of clause 13 wherein the receiving comprises receiving a first heat flux into the heat pipe at the first surface from a portion of the armour in a vicinity of a point on the first surface; and the transferring comprises transferring a second heat flux out of the heat pipe at the second surface, the second heat flux having a lower power per unit area than the first heat flux.

[0204] 15. In an apparatus comprising the heat pipe of clause 1 and a plasma confinement device (for nuclear fusion) comprising a divertor having armour comprising the armour attached to the heat pipe, the method of clause 14 wherein the receiving comprises receiving the first heat flux from a portion of the armour in a vicinity of a strike point of the divertor during operation of the plasma confinement device.

[0205] 16. 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 attached to the heat pipes.

[0206] 17. The apparatus of clause 16 wherein the armour is wholly or partially integrated into the component.

[0207] 38305906-118. The apparatus of clause 16 and further comprising a heat exchanger operably coupled to the heat pipes at the second surfaces thereof.

[0208] 19. In a system comprising the apparatus of clause 18 and further comprising a plasma confinement device wherein the component is disposed, a thermal management method comprising:

[0209] receiving heat at the component from a plasma contained by the plasma confinement device during operation of the system;

[0210] conveying at least a portion of the received heat to the heat exchanger through the heat pipes; and

[0211] exhausting at least a portion of the conveyed heat away from the heat exchanger.

[0212] Further aspects of the present invention are summarised by the following numbered clauses:

[0213] 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.

[0214] 102. 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 second portion of the heat pipe juts away from the armour.

[0215] 103. The heat pipe of clause 101 partially embedded in the castellated armour.

[0216] 104. The heat pipe of clause 101 having an exterior surface adjacent to an exterior surface of the castellated armour.

[0217] 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.

[0218] 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.

[0219] 108. The heat pipe of clause 101 wherein the pieces are arrayed along a length of a portion of the heat pipe.

[0220] 109. The heat pipe of clause 101 wherein each of the pieces comprises a tile, a plate, a block or a monoblock.

[0221] 38305906-1110. 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.

[0222] 111. The heat pipe of clause 110 wherein the heat pipe is operatively coupled to a heat exchanger in a vicinity of the second portion.

[0223] 112. The heat pipe of clause 101 wherein the castellated armour comprises a refractory metal or an alloy of a refractory metal.

[0224] 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 one of water, a gas, or a liquid metal.

[0225] 115. The heat pipe of clause 114 wherein the working fluid comprises a liquid metal, the liquid metal being one of lithium, sodium, potassium, NaK, or caesium, or any mixture thereof.

[0226] 116. The heat pipe of clause 101 wherein an interlayer is disposed between the heat pipe and the armour.

[0227] 117. 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.

[0228] 118. The heat pipe of clause 101 wherein the castellated armour is armour for a component of a plasma confinement device.

[0229] 119. Apparatus comprising a plurality of the heat pipes of clause 101 and a component for a plasma confinement device, wherein the component has armour comprising the armour of the heat pipes.

[0230] 120. The apparatus of clause 119 wherein the armour of the component is wholly or partially integrated into the component.

[0231] 121. The apparatus of clause 119 wherein the armour of the component is distinct from the component.

[0232] 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

[0233] 38305906-1segment 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.

[0234] 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.

[0235] 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.

[0236] 125. The apparatus of clause 124 wherein the plasma-facing surface of the component is coincident with a surface of the armour.

[0237] 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.

[0238] 127. The apparatus of 126 wherein the contour comprises one or more straight line segments, curves, or a mixture of these.

[0239] 128. In the heat pipe of clause 102, a method comprising:

[0240] receiving 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.

[0241] 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.

[0242] 130. Apparatus comprising a heat exchanger operatively coupled to one or more of the heat pipes of clause 101.

[0243] 131. In the apparatus of clause 130, a thermal management method comprising:

[0244] receiving heat at the armour of the one or more heat pipes;

[0245] conveying at least a portion of the received heat to the heat exchanger through the one or more heat pipes; and

[0246] exhausting at least a portion of the conveyed heat from the heat exchanger.

[0247] 38305906-1132. 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.

[0248] 133. The method of clause 131 wherein the apparatus of clause 30 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.

[0249] 134. A system comprising the apparatus of clause 119 and a plasma confinement device wherein the component is disposed.

[0250] 135. The system of clause 134 wherein the plasma confinement device is one of a magnetic confinement device, a tokamak, a stellarator, a spheromak, a mirror machine, a field-reversed configuration device, or a Z-pinch device.

[0251] 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.

[0252] 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.

[0253] 138. In the system of clause 134, a method comprising:

[0254] operating the device to confine a plasma therein;

[0255] generating heat from the confined plasma;

[0256] providing a portion of the generated heat to the armour through one or more of conduction, convection, or radiation; and

[0257] 38305906-1conveying at least a portion of the heat flux incident on the armour through the heat pipes.

[0258] 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.

[0259] 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:

[0260] a. receiving, from the armour of the heat pipe, an input non-uniform heat flux into a first part of the heat pipe; and

[0261] b. providing a substantially uniform output heat flux out of a second part of the heat pipe.

[0262] 141. 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.

[0263] 142. The method of clause 140 wherein the providing comprises providing the output heat flux in a direction substantially perpendicular to a long axis of the heat pipe.

[0264] 143. The method of clause 140 wherein first and second parts are, respectively, first and second heat transfer surfaces disposed on opposite sides of a long axis of the heat pipe, the heat pipe being attached to the armour in a vicinity of the first surface, and wherein the receiving comprises receiving an input heat flux distributed non-uniformly over the first surface, and the providing comprises providing an output heat flux distributed substantially uniformly over the second surface.

[0265] 38305906-1

Claims

37CLAIMS:

1. An apparatus comprising:a component comprising a plurality of physically distinct units; and a heat pipe in thermal contact with each unit of the plurality of physically distinct units, the heat pipe comprising:a channel;a first portion configured as an evaporator portion of the heat pipe, which first portion is affixed to each unit of the plurality of physically distinct units; anda second portion configured as a condenser portion of the heat pipe, which second portion opposes the first portion in a direction transverse to a direction defining a major dimension of the channel, the second portion configured to be operatively coupled to a heat exchanger, wherein the first and second portions are spaced apart from one another by a distance corresponding to a minor dimension of the channel.

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 any one of claims 1 to 2, wherein 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.

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

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

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

7. An apparatus according to any one of the preceding claims, wherein the plurality of physically distinct units comprises ten or more units.38305906-1388. An apparatus according to any one of the preceding claims, wherein the plurality of physically distinct units comprises thirty or more units.

9. 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.

10. An apparatus according to any one of the preceding claims, wherein a main constituent of a material comprising the component is a metallic element, the metallic element having an atomic number greater than or equal to 40.

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

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

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

14. An apparatus according to any one of the preceding claims, wherein the component is or has a castellated armour.

15. An apparatus according to any one of the preceding claims, wherein said units are arranged to form a castellated structure.

16. An apparatus according to any one of the preceding claims, wherein said units are arranged in a rectilinear array.

17. An apparatus according to claim 16, wherein the rectilinear array is any one of: a rectangular array, a square array, a hexagonal array, or a triangular array.38305906-118. An apparatus according to any one of the preceding claims, wherein the heat pipe and / or the channel of the heat pipe follow a contour of a smooth external surface of the component.

19. 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.

20. An apparatus according to any one of the preceding claims, comprising a plurality of heat pipes, wherein the plurality of heat pipes includes the heat pipe recited in claim 1, wherein each heat pipe of the plurality is in in thermal contact with the component at a respective plurality of physically distinct units of the component, each heat pipe comprising:a channel;a first portion affixed to each unit of the respective plurality of physically distinct units; anda second portion opposing the first portion in a direction transverse to a dimension defining the major dimension of the respective channel, the second portion configured to be operatively coupled to a heat exchanger, wherein the first and second portions are spaced apart from one another by a distance corresponding to a minor dimension of the channel.

21. An apparatus according to claim 20, wherein the plurality of heat pipes are arranged in an array, each heat pipe forming at least a portion of a row or column of said array.

22. An apparatus according to any one of claims 20 to 21, comprising a heat exchanger operatively coupled to each heat pipe at the respective second portion of said heat pipe.

23. An apparatus according to any one of claims 20 to 21, 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.38305906-124. An apparatus according to claim 22 or 23, wherein the or each heat pipe is interposed between the heat exchanger and the component so as to space the heat exchanger and the component apart in a direction transverse to a direction defining the major dimension of the channel.

25. 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.

26. 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 material having a CTE intermediate between the first and second CTEs.

27. A plasma confinement device, comprising the apparatus of any one of claims 1 to 26.

28. A plasma confinement device according to claim 27, 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 thereof; an armour for any of the foregoing or a portion thereof; or a thermal management component for any of the foregoing.

29. A plasma confinement device according to claims 27 or 28, 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.

30. A system comprising:38305906-1a heat source; andthe apparatus of any one of claims 1 to 26 thermally coupled to the heat source.

31. A system according to claim 30, wherein 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.

32. A system according to claim 31, 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.

33. A thermal management method applied to the apparatus of any one of claims 1 to 26, the method comprising:receiving, by the heat pipe or heat pipes, thermal flux from the plurality of physically distinct units of the component contemporaneously; conveying thermal energy from at least a portion of the received thermal flux along the channel of the or of each heat pipe; andconveying at least a portion of the conveyed thermal energy towards a heat exchanger in a direction transverse to a direction defining the major dimension of the channel of the or each heat pipe.

34. A method according to claim 33, wherein a magnitude of 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.

35. A method according to claim 33 or 34, 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.

36. A method according to claim 35, wherein the thermal energy conveyed to the heat exchanger is provided as a thermal flux to the heat exchanger, and38305906-142wherein the thermal flux across the second portion of the heat pipe is distributed more uniformly than the thermal flux received by the heat pipe is distributed across the first portion of the heat pipe.

37. A method according to claim 36, wherein the thermal flux to the heat exchanger is distributed substantially uniformly across the second portion of the heat pipe.

38. A method according to any one of claims 35 to 37, further comprising:exhausting, using a coolant carried by the heat exchanger, at least a portion of the thermal energy conveyed into the heat exchanger.

39. A method according to any one of claims 33 to 38, 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.

40. A method according to claim 39, further comprising:adjusting operating parameters of the heat exchanger to maintain the component at a temperature between DBTT and RT.

41. A method according to any one of claims 33 to 40 further comprising:operating a plasma confinement device to generate a plasma; and receiving, by the component, energy from the plasma.

42. A power generation method using the system of claim 31, 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 the channel of the or of each heat pipe and into the or each heat exchanger in a direction transverse to a direction defining a major dimension of said channel to heat coolant in said heat exchanger; and driving a turbine to turn and generate electrical power using flow of the heated coolant.38305906-1

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