Heat exchanger

Abstract

An assembly for retrofitting an immersion heater boss 304 of a tank system (fig. 1, 102) with a thermal transfer system 116, comprising a connector body 302 through which an immersion heating element

Description

Technical field This application relates to heating systems, in particular for domestic use. Background Data centres release significant amounts of energy each year in the form of heat. It is desirable to make use of this energy for a useful purpose. One way is to distribute the compute units of the data centre in people’s homes and use them to heat their water, thereby assisting people experiencing fuel poverty. GB2576035 describes an approach to thermally couple a compute unit to vented hot water tanks for this purpose. In the UK, vented hot water tanks are being largely replaced by unvented ones. Unvented tanks (which are usually cylinders) receive cold water directly from the mains water supply at mains pressure, which, in general, translates to improved pressure and water distribution in the home, as compared with vented systems. The cold water is then heated by passing hot water through a boiler coil immersed in water within the tank and / or using an electric heating element immersed in the water within the tank. This is referred to as an immersion heating element. As tanks are usually unvented (i.e. it is part of a sealed system), they should be capable of withstanding elevated fluid pressures (typically around 3 to 6 bar) caused by the heating of the water (e.g., to 60 to 85°C) which it holds. For this reason, conventional unvented cylinders include a protective outer casing arranged around the thermal insulation layer of the pressure vessel wall. There is a problem with how to thermally couple a compute unit to the pressure vessel in a cost effective manner. Plumbing operations are costly and associated with risks (e.g., leaks) and so plumbing is not a viable option to address this problem. Summary of the Invention Aspects of the present invention provide an assembly for retrofitting (i.e. modifying to include a feature not present at manufacture), a method of retrofitting an immersion heater boss, a method of retrofitting a tank, a system, a method of installing the system, a method of providing the assembly, and a computer program product, as set out by the appended set of claims. Each of the aspects describe or facilitate an approach for transferring heat from a heat source into a tank using the immersion heater boss port as an access point for the thermal transfer system. The first aspect describes the components for modifying an existing an immersion heater boss so that it is suitable as such an access point. The second aspect describes how to retrofit an as-manufactured immersion heater boss so that it becomes suitable as an access point. The third aspect describes how to retrofit the as-manufactured tank so that it is suitable for being thermally coupled with the thermal transfer system and which involves retrofitting the as-manufactured immersion heater boss. The fourth aspect describes a system in which the thermal transfer system is thermally coupled to the tank through the immersion heater boss port. The fifth aspect relates to installation of such a system. The sixth and seventh aspects relate to how the assembly according to the first aspect is provided (i.e. manufactured). According to a first aspect of the invention, there is provided an assembly for retrofitting an immersion heater boss of a tank. The assembly includes a connector body, having an opening through which the immersion heater element of the immersion heater boss can pass freely (i.e. without being unobstructed), a fluid inlet hole for receiving an inflow pipe, and a fluid outlet hole for receiving a return pipe. The connector body includes respective coupling means (e.g., one at each of its opposing ends) for releasably securing the connector body to the immersion heater boss and to the immersion heater. The assembly further includes a fluid coupling element configured to engage with an inner edge of the connector body to provide an inlet fluid channel and an outlet fluid channel in fluid communication with the fluid inlet hole and fluid outlet hole, without preventing free passage of the immersion heater through the opening of the connector body. That is, when the fluid coupling element is engaged against the inner edge of the connector body, it remains possible to pass the immersion heater element through the opening defined by the connector body. The assembly is specially adapted for retrofitting an immersion heater boss such that, when the retrofit (or modified) boss is coupled to the immersion heater boss port of a tank, it can be used as an access point for fluidly coupling a first part of a thermal transfer system, which is arranged outside of the tank, to a second part of a thermal transfer system, which is located within the tank. The first part of the thermal transfer system may include an inflow pipe extending from a heat source (e.g. a compute unit) to the fluid inlet hole of the boss, and a return pipe extending from the fluid outlet hole to the heat source. The second part of the thermal transfer system may include a “tank” pipe (i.e. a pipe arranged within the tank), which fluidly couples the fluid inlet hole, inlet fluid channel, outlet fluid channel, and fluid outlet hole together. Advantageously, this approach does not cause any damage to the thermal insulation and protective casing of the tank, which surrounds the pressure vessel wall of the tank. The safety of the system remains uncompromised and so tedious safety inspections following the retrofit can be largely avoided. In some examples, the fluid coupling element is configured such that, when it is engaged against the inner edge of the connector body, it permits fluid flow between (i) the fluid inlet hole and the inlet fluid channel; and (ii) the fluid outlet hole and the outlet fluid channel, regardless of its rotational position with respect to the connector body. That is, the fluid coupling element can be arranged in any one of a plurality of rotational positions relative to the connector body, while maintaining fluid communication between (i) the fluid inlet hole and the inlet fluid channel; and (ii) the fluid outlet hole and the outlet fluid channel. This improves the ease with which the immersion heater boss can be retrofitted: exact alignment between the fluid inlet and outlet holes and the inlet and outlet fluid channels, respectively, is not required. Moreover, any pipe, which is to be coupled or fitted to the fluid coupling element and which would extend within the tank during use, can be rotated with respect to the connector body (and fluid inlet and outlet hole) to facilitate installation without colliding with the inner walls of the tank. A rotational position refers to an angular position of the fluid coupling element relative to the connector body, with respect to a rotation axis which extends through the opening defined by the connector body (i.e., which is coincident with a centre line of the opening). Put differently, the fluid coupling element is operable to rotate about the rotation axis relative to the connector body by a predetermined angle (i.e. through a range of different rotational positions). As has already been noted, this facilitates installation. In some examples, the inlet and outlet fluid channels extend completely around the rotation axis so that the fluid coupling element can be arranged in any rotational position with respect to the connector body. That is, the inlet and outlet fluid channel have perfect, or infinite rotational symmetry, and the predetermined angle has no upper threshold, per se. In some examples, to save material costs, it is desirable that the predetermined angle is less than an upper threshold. Example thresholds are 180, 150, 90, and 70 degrees. In general terms, the predetermined angle may be between 1 and 360 degrees, more preferably between 2 and 90 degrees. To achieve the rotational invariance (across a range of angles), the fluid coupling element may define an inlet pocket and an outlet pocket. The inlet and outlet pocket form part of the inlet and outlet fluid channel, respectively, when the fluid coupling element is engaged against the inner edge of the connector body. The pocket may be a recess. The inlet and outlet pocket extend around the rotation axis to thereby define a plurality of different rotational positions, each of which the fluid inlet hole and the fluid outlet hole can respectively fluid couple to. In a specific example, the inlet and outlet pocket extend circumferentially about the rotation axis, although the path traced by the pocket need not necessarily be curved. The angle subtended by the inlet and / or outlet pocket may be greater than or equal to the predetermined angle. In some examples, the inner edge of the connector body includes a groove or a lip to aid in locating the fluid coupling element into a position in which the fluid inlet hole and fluid outlet hole overlap with the inlet and outlet pocket, respectively. Overlap here is intended to mean that the respective hole and pockets, when overlapping, are in fluid communication. In some examples, the fluid coupling element includes a complementary feature (e.g., a groove if the connector body has a lip, and a lip if the connector body has a groove) which engages against the groove or lip to further promote the ease of assembly. In some examples, the inlet and outlet fluid hole in the connector body are offset with respect to one another along with respect to a direction coincident with the rotation axis. In general, the holes are offset by a distance sufficient to prevent the inlet pocket from overlapping with the outlet fluid hole, when it overlaps the inlet fluid hole. Ultimately, this helps maximise the predetermined angle that the fluid coupling element can be rotated relative to the connector body. In a specific example, a portion of the inlet fluid channel and outlet fluid channel is provided by a respective opening that extends through a body of the fluid coupling element. The inlet pocket is fluidly connected with this portion of the inlet fluid channel, and the outlet pocket is fluidly connected with this portion of the outlet fluid channel. In general, immersion heater bosses for domestic unvented or vented tanks have a diameter less than 100mm. The components of the assembly are of a similar order of magnitude in size. In a specific example, the inlet fluid channel and the outlet fluid channel each have a diameter in the range 5mm to 30mm, more preferably 10 to 22mm. In some examples, the assembly includes a retaining element for releasably or reversibly securing the fluid coupling element against the inner edge of the connector body. This ensures that the fluid coupling element can remain in position, regardless of its orientation in space (i.e. with respect to the direction of gravity). In a specific example, the retaining element is a circlip, which permits rotation of the fluid coupling element but restricts or prevents axial motion of the fluid coupling element (along the rotation axis) relative to the connector body. According to a second aspect of the invention, there is provided a method of retrofitting an immersion heater boss. The method includes providing a connector body, as described above in relation to the first aspect, engaging a fluid coupling element against an inner edge of the connector body to provide an inlet fluid channel and an outlet fluid channel in fluid communication with the fluid inlet hole and the fluid outlet hole of the connector body respectively, and then coupling the connector body to the immersion heater boss. This retrofit boss can be thought of as an “extended” boss, which further comprises a connector body and an inlet and outlet for fluid flow. According to a third aspect of the invention, there is provided a method of retrofitting a tank, comprising a port on which an immersion heater boss with an immersion heater element is installed. The method comprises decoupling the immersion heater boss from the port of the tank, and providing the connector body, as described in relation to the first aspect. The connector body is then coupled to the port and a fluid coupling element is engaged against an inner edge of the connector body to provide an inlet fluid channel and an outlet fluid channel in fluid communication with the fluid inlet hole and the fluid outlet hole, respectively. Thereafter, a pipe (referred to as a tank pipe as, after installation, it is located within the tank) is inserted through the opening provided by the connector body and into the tank. The tank pipe defines two open ends and in some examples forms a U-shape. The two open ends are secured to the inlet fluid channel and outlet fluid channel, respectively, thereby fluidly connecting the fluid inlet hole and the fluid outlet hole of the connector body. Next, the immersion heater boss, with an immersion heater element, is coupled to the connector body. The result is a tank with a modified immersion heater boss that is specially adapted to be, or form part of, a thermal transfer system. In some examples, the method further comprises securing an inflow pipe and a return pipe to the fluid inlet hole and the fluid outlet hole, respectively. Thereafter, it is possible to pass a fluid (i.e. a coolant) into the inflow pipe, through the retrofit boss via the fluid inlet hole and inlet fluid channel, into the tank through the port, through the tank pipe and back out from the tank via the port, outlet fluid channel and outlet fluid hole within the retrofit boss, and then away from the tank along the return pipe. In other words, the tank has been retrofit with a thermal transfer system, using the immersion heater boss as an access point for fluidly coupling a first part of a thermal transfer system, outside of the tank, to a second part of the thermal transfer system, located within the tank. The first part of the thermal transfer system includes the inflow pipe extending from a heat source (e.g. a compute unit) to the fluid inlet hole of the boss, and the return pipe extending from the fluid outlet hole and optionally to the heat source. The second part of the thermal transfer system may include a “tank” pipe (i.e. a pipe arranged within the tank), which fluidly couples the fluid inlet hole, inlet fluid channel, outlet fluid channel, and fluid outlet hole together. Advantageously, a portion of the thermal energy generated as waste by the compute unit can be used to heat up water in the tank. According to a fourth aspect, there is provided a system. The system may be regarded a heating system because, in use, it can be used to heat water in the tank. The system includes a tank, comprising a port on which a boss (i.e. the retrofit or extended boss referred to above) with an immersion heater element is installed. The system also comprises a compute unit as a heat source. The compute unit includes a thermal transfer system for transferring thermal energy generated by the compute unit into the tank. The thermal transfer system defines a channel for fluid flow, which extends from the compute unit into, and out from, the tank through the port and boss of the tank. The system advantageously facilitates the transfer of thermal energy from a heat source (i.e. the compute unit) to the tank (which typically will be filled with water). The system can, therefore, be used to transfer heat generated as waste by the compute unit to the tank in order to heat water. This is especially useful in a domestic context, i.e. for heating water at people’s homes but it also finds use in a commercial setting (e.g., in hotels, offices, etc.). During use, typically water will be used as the coolant within the channel defined by the thermal transfer system but other fluids are also envisaged. In some examples, the thermal transfer system includes an inflow pipe extending from the compute unit to a fluid inlet hole of the boss, a return pipe extending from a fluid outlet hole of the boss to the compute unit, and a tank pipe arranged within the tank, which fluidly connects the fluid inlet and fluid outlet hole. According to a fifth aspect of the present invention, there is provided a method of installing the system according to the fourth aspect. The method includes inserting a first portion of the thermal transfer system into the tank via the port; coupling the boss (i.e. the extended or retrofit boss referred to above) to the tank; fluidly coupling the first portion of the thermal transfer system to an inlet fluid hole and an outlet fluid hole of the boss; and coupling a second portion of the thermal transfer system, which resides outside the tank and which extends from the compute unit, to the inlet fluid hole and the outlet fluid hole of the boss or connector body to thereby provide a channel for fluid to flow from the compute unit into and out from the tank via the port and the boss. According to a sixth aspect of the invention, there is provided a method of providing the assembly according to the first aspect. The assembly being a process selected from a group comprising: casting, injection moulding, power metallurgy processing (sintering, hot or cold isostatic pressing and sintering), and / or additive manufacturing. Possible additive manufacturing techniques include 3-D printing; Direct metal laser sintering; Selective Laser sintering; Stereolithography; Fused deposition modelling; Field assisted sintering technique; Spark assisted sintering; Electron beam sintering; and / or Direct metal deposition. If additive manufacturing techniques are used, the method of providing the assembly may include a step of obtaining an electronic file representing a geometry of the or each component making up the assembly according to the first aspect; and controlling an additive manufacturing apparatus to generate, over one or more additive manufacturing steps, the or each component according to the geometry specified in the electronic file. According to a seventh aspect of the present invention, there is provided a computer program product, comprising executable instructions stored thereon, which, when executed by a processor, cause the processor to control a manufacturing apparatus (e.g., an additive manufacturing apparatus) to generate the or each component making up the assembly according to the first aspect. According to further aspects of the present invention, there is provided a retrofit immersion heater boss, a retrofit tank obtained by the methods of the second and third aspect. There is also provided a compute unit and a method of heating water. The retrofit immersion heater boss includes the unmodified immersion heater boss (i.e. as-manufactured), with the connector body coupled thereon, and the fluid coupling element engaged against its inner edge. The connector body and fluid coupling element being as described above in relation to the first aspect. The retrofit tank includes the unmodified tank (i.e. as-manufactured), with the retrofit immersion heater boss replacing the unmodified immersion heater boss. The retrofit tank may further include a tank pipe which fluidly connects the fluid inlet hole and fluid outlet hole of the connector body, as described above. The compute unit comprises a thermal transfer system configured to transfer thermal energy generated by a processor of the compute unit away from processor. The thermal transfer system defines a channel for fluid flow (i.e. a coolant) which extends from the compute unit into, and out from, a tank through a port defined in the tank and through a boss coupled to that port. The compute unit may further comprise one or more communications interface(s) for receiving computing tasks; a power supply unit for receiving a mains power supply and output power for powering a CPU and or GPU and or TPU of the compute unit. The processor(s) of the compute unit may be coupled to memory, such as non-volatile memory. The method of heating water contained within a tank, the tank comprising a port for receiving a boss containing an immersion heating element, the method comprising: executing a computing task on the compute unit; transferring at least a portion of the heat generated by the compute unit into the tank, using a thermal transfer system which carries a flow of a coolant, wherein the thermal transfer system defines a channel for coolant to flow, which extends from the compute unit (i.e. where it is in thermal contact with the compute unit, more specifically the processor(s) of said unit) into, and out from, the tank through the port and the corresponding boss of the tank. Brief Description of the Drawings Aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a heating system; Figure 2 is a block diagram of a compute unit; Figure 3 is a perspective view of a retrofit immersion heater boss; Figure 4 is a perspective view of a connector body; Figure 5A is a perspective view of a fluid coupling element; Figure 5B is a perspective view of a partial longitudinal cross section of the retrofit immersion heater boss from Figure 3; Figure 6 is a perspective view of a retaining element; Figure 7, 8, 9, and 10 are method flow diagrams; Figure 11 is a perspective view of a fluid coupling element; Figure 12 is a perspective view of a partial longitudinal cross section, showing the coupling element from Figure 11 fitted within the connector body from Figure 4; Figure 13A is a perspective view of a connector body; and Figure 13B is a perspective view of a partial longitudinal cross section, showing a retrofit immersion heater boss. Detailed Description In general terms, this disclosure relates to retrofitting a tank system so that it (and specifically the water contained within the tank of the system) is suitable for being thermally coupled to an external heat source, such as a compute unit arranged outside of the tank. The thermal coupling between the compute unit and the tank enables the transfer of thermal energy, which is released by the compute unit as it executes computing tasks, to the tank. Energy that would otherwise be wasted from the compute unit is, therefore, used for a useful purpose - heating up water contained with the tank. A problem with unvented water tanks is that they include a protective casing arranged around the thermal insulation of the pressure vessel. This obfuscates direct (i.e. where direct contact is established) thermal coupling between the compute unit and wall of the pressure vessel. The protective casing is required to ensure the elevated pressures expected for unvented cylinders can be accommodated safely. But it will be understood that proposed approach can be applied to other forms of cylinders too (e.g., vented cylinders). Instead of removing (and damaging) the thermal insulation and casing, this disclosure proposes using a port of the tank, specifically the port for the immersion heater element, as an access point for a thermal transfer system for transferring heat from the compute unit into the tank. The embodiments described herein refer to an “inlet or inflow” side, and “an outlet or return” side. It will be understood that these terms are interchangeable because they depend on the direction of fluid flow through the thermal transfer system during use, rather than any feature inherent to the system itself. Figure 1 is a schematic illustration of a heating system 100, according to an embodiment. The heating system includes an unvented tank system 102, which comprises an unvented tank 104 with a thermal insulation 106 and a protective casing 108 arranged around it. The thermal insulation is arranged between the unvented tank and the casing. As has already been noted, this makes effective thermal coupling to the unvented tank difficult, without locally removing the insulation and the protective casing. The system further comprises a compute unit 110, which functions as a heat source, and a boss 112 which is threadedly coupled to a port 114 of the unvented tank. At and immediately around the port, the tank system is absent or lacks the thermal insulation and protective casing. As shown, the compute unit is thermally coupled to the unvented tank (and any fluid it contains, such as water) by a thermal transfer system 116, which extends from the compute unit 110 into the unvented tank 104 via the boss and port, and then back out from the unvented tank again via the boss 112 and the port 114. The thermal transfer system 116 includes a first portion 116a arranged within the unvented tank, a second portion 116b arranged outside the unvented tank, and a third portion 116c arranged within the boss. Each of the first, second, and third portions include (i) an inflow or inlet side and (ii) a return or outlet side. The thermal transfer system collectively defines a channel for coolant to flow: (a) from the compute unit to the boss; (b) from the boss into the unvented tank; (c) through the unvented tank and out from the unvented tank via the port and the boss; (d) away from the boss. The thermal transfer system may form a closed loop, although it is also envisaged that the system could be coupled at one end to a coolant supply (such as a mains water supply) and to a drain at the other end. In an example, the first portion 116a of the thermal transfer system comprises a tank pipe, which is shaped to form a ll-bend (or comprises a ll-bend) and which defines two open-ends. One of the open ends extend from the inlet fluid channel into the unvented tank, and the other of the open ends extends from outlet fluid channel into the unvented tank. In some examples, opposing sections of the ll-bend are mechanically coupled with each other using a bracket to improve robustness. The pipe may be made from copper or a copper-based alloy. In Figure 1, the port is shown located on a lateral side of the tank, and as a result, the tank pipe extends into the tank before running along the lateral side wall of the tank. It will be understood that the port can, alternatively, be located at the top side of the tank and in that case, the tank pipe may extend directly downwards toward the bottom side of the tank. In an example, the second portion of the thermal transfer system comprises an inflow pipe that extends from the compute unit and connects with the fluid inlet hole of the boss 112, and a return pipe that connected with the fluid outlet hole of the boss and extends away from it. The return pipe may extend towards the compute unit and / or form a closed loop with the inflow pipe. That is, fluid may be able to flow from the return pipe and the inflow pipe (outside of the unvented tank). In some examples, the return pipe and inflow pipe are mechanically coupled to each other using a bracket to improve robustness. In an example, the third portion of the thermal transfer system comprises an inlet fluid channel and an outlet fluid channel. These channels may be generated by the fluid coupling element as it engages against the inner edge of the connector body (as described in more detail below). The inlet fluid channel fluidly connects one end of the tank pipe to the fluid inlet hole. The outlet fluid channel fluidly connects one end of the tank pipe to the fluid outlet hole. The system 100 advantageously facilitates the transfer of heat from the compute unit 110 (which functions as a source of heat) to the unvented tank 104. In an example, the thermal energy carried by coolant that flows through or around the thermal transfer system 116 can be used to heat water or other fluid contained in the unvented tank. In general, the port 114 of the unvented tank, which is used as the access point for the thermal transfer system, is the port, which was originally intended for an (as-manufactured) immersion heater boss. This port is found on most, if not all, unvented tanks. As-manufactured immersion heater bosses include an immersion heating element and a cap portion from which the immersion heating element extends. The cap portion includes a threaded portion for coupling to the port of the tank and for forming a sealed connection therebetween. This ensures no loss of pressure (e.g., in the form of water vapour) from the unvented tank, during heating. As-manufactured bosses are not suitable as an access point for the thermal transfer system (since they include no access points for the thermal transfer system). The boss 112 shown in Figure 1 is a retrofit or modified immersion heater boss, as shown in Figure 3, for example. In use, the heating element extends into the unvented tank and is at least partially submerged in the water held within the tank. The boss in Figure 1 is shown without an immersion heating element for simplicity. Figure 2 is a block diagram of the compute unit 110, according to an embodiment. The compute unit comprises: a mains power supply 110a for providing power to the unit; and a bus 110b to which processor(s), such as a CPU 110c (Central Processing unit), GPU(s) (Graphics Processing unit) and / or TPU(s) (Tensor Processing unit) 110d; non-volatile memory 110e; working memory 11 Of; and a communication interface 110g are coupled. Optionally, the compute unit comprises one or more temperature sensors 110h. In a specific example, the temperature sensors are arranged to sense a temperature of fluid flowing through the thermal transfer system 116 downstream and upstream of the unvented tank. Any suitable temperature sensors, such as thermocouples or thermistors, can be used for this purpose. Referring back to Figure 1, the processor(s) of the compute unit may be in thermal contact (either directly or indirectly) with a portion of the thermal transfer system in order to promote efficient heating of the coolant within the thermal transfer system. The non-volatile memory 110e stores operating system code for communicating with a remote server in order to receive and execute computing tasks. The non-volatile memory 110e may also receive and store code and / or data for local execution of a task on the CPU and / or GPU(s) / TPU(s). In some embodiments, the compute unit includes a relay control interface 110i for providing wired and / or wireless control of a relay or similar controllable switch. The relay may be used to control an immersion heater. In use, the compute unit 110 receives and executes tasks under remote control (e.g., via a remote server to which the compute unit is wirelessly connected). Execution of these tasks using the compute unit generates heat from the PCU and / or GPU(s) / TPU(s). A typical compute unit, such as those found in conventional data centres, generate a few hundred watts in the form of heat. Examples of computing tasks include: rendering (e.g. for an animation), modelling (e.g., climate change modelling, chemical modelling, such as for drug discovery, biochemical modelling, such as protein folding), a machine learning task (e.g., federated learning), and / or a cryptocurrency mining task (e.g., a proof of work puzzle). In some implementations, the one or more temperature sensors 110h can be used to provide a feedback loop, such that the compute unit can controllably heat (or allow cooling of) the coolant flowing through the thermal transfer system and / or the water contained within the unvented tank to a predetermined temperature. This may involve allocating computing tasks to the CPU, GPU and / or TPU according to the expected power consumption of the computing task. As an example, if the temperature within the tank is below the predetermined temperature, the compute unit can be remotely controlled to employ a larger number of cores, use a greater clock speed, and / or be provided with more computing tasks to execute on its CPU and / or GPU and TPU. Figure 3 is a perspective view of a retrofit or modified immersion heater boss 112 (herein boss). The boss includes a connector body 302, an as-manufactured immersion heater boss 304 with an immersion heating element 306, a fluid coupling element 308, and a retaining element 310 in the form of a circlip. As shown, the connector 302 defines a (hollow) opening through which the immersion heating element 306 of the as-manufactured immersion heater boss 304 extends. The connector body also includes a first and a second threaded coupling. The first threaded coupling (not visible in Figure 3) is for securing the connector body to the as-manufactured immersion heater boss. All as-manufactured immersion heater bosses include a coupling, such as a threaded portion, for securing the “as-manufactured” boss to the unvented tank. This coupling can be used to connect the connector body and as-manufactured boss together. The second threaded coupling is for securing the connector body to the threaded coupling provided by the port of the unvented tank. The threading type of the second threaded coupling is complementary to the threading type provided by the port, i.e., it can be either “male” or “female”. As a result, the connector body includes two threaded couplings: one of male type and one of female type. In Figure 3, the fluid coupling element 308 is shown engaged against an inner edge or surface of the connector body 302, which is defined by the opening through the connector body. The retaining element 310, which is a circlip in Figure 3 extends around the remaining inner edge or surface of the connector body and engages against the fluid coupling element 308 to secure it in place. The fluid coupling element is shown in more detail in Figure 5A and 5B. It suffices to say here that the fluid coupling element 308 is for providing a fluid channel for fluidly coupling the first and second portions 116a, 116b of the thermal transfer system together to thereby facilitate the flow of a fluid into and out from the unvented tank via the boss 112 and port 114 of the unvented tank. In Figure 3, the first and second portions of the thermal transfer system 116a, 116b are shown connected to the fluid coupling element 308 and the connector body 302, respectively. The as-manufactured immersion heater boss generally refers to the immersion heater boss of the unvented tank, before it has been modified to include the connector body shown in Figure 3. For most, if not all, practical examples, this is the immersion heater boss, which was previously installed or intended to be installed on the unvented tank. The immersion heating element shown in Figure 3 is in the form of a ll-bend, which has been folded back on itself once. Other shapes of immersion heating element are, however, envisaged. Figure 4 is a perspective view of a connector body 302, according to an embodiment. The connector body defines an opening 402 through which an immersion heating element can extend (as for example shown in Figure 3). The connector body comprises a first and a second coupling portion 404a, 404b (one at each of its opposing ends) for securing the connector body to (i) the as-manufactured boss 304 and (ii) the port of the unvented tank, respectively. In the example shown, the coupling portions are a male and female type threading. In some examples, the first and second coupling portions are axially offset to provide more space for the immersion heating element 306 during installation. The connector body further defines a fluid inlet hole and a fluid outlet hole 406a, 406b into which the second portion 116b (i.e. the inflow pipe and the return pipe) of the thermal transfer system can be received or otherwise fluidly connected (e.g., by soldering, braising, threaded connection, or a push-fit fastener, such as a Speedfit® connector). As shown, the fluid inlet and fluid outlet holes 406a, 406b are offset or staggered with respect to a longitudinal axis, defined by the opening through the connector body. In some examples, the connector body defines a hex-flange, for example, at the end of the connector which is to be secured against the as-manufactured boss 304. This facilitates assembly of the connector body and the boss 304. In some examples, the connector body includes a groove or a lip, which facilitates locating of the fluid coupling element into a position in which it can fluidly couple the first and second portions 116a, 116b of the thermal transfer system together. Preferably, although not necessarily, the fluid coupling element includes a complementary feature (i.e. a lip or groove) for mating with this groove or lip. In some examples, the connector body includes a groove 410 or ridge, which facilitates the securement of the retaining element within the connector body. The retaining element then includes a complementary feature for mating with this groove or ridge. Figure 5A is a perspective view of the fluid coupling element 308, according to an embodiment. The fluid coupling element defines an inlet pocket 502 and an outlet pocket 504, an inlet opening 506 extending through the body of the fluid coupling element from the inlet pocket 502, and an outlet opening 508 extending through the body of the fluid coupling element from the outlet pocket 504. The first portion 116a (e.g., a tank pipe) of the thermal transfer system can be received or otherwise fluidly connected (e.g., by a press fitting, a threaded connection, grub screws, or other mechanical fastener) to these inlet and outlet openings 506, 508. The tank pipe generally comprises a ll-bend (or is formed into a ll-bend shape) and defines two open-ends. The flow paths 510, 512 for coolant are denoted by a dotted arrow. The fluid coupling element is shown as being generally arcuate in shape (when viewed longitudinally, i.e. along a longitudinal axis defined by the opening of the connector body). This curved shape helps ensure that the abutment between the fluid coupling element and the inner edge of the connector body is a flush one. This maximises the space available for the immersion heating element 306 to pass through the opening 402 of the connector body and it also ensures that the fluid inlet channel and fluid outlet channel are fluid tight. More generally, the fluid coupling element may define any abutment surface, which has a profile complementary to the inner edge or surface of the connector body to provide this flush fitting. Figure 5B is a partial longitudinal cross section 500 of the modified immersion heater boss 112 from Figure 3. Figure 5B shows the flush fitting between the fluid coupling element 308 and the connector body 302. Referring to Figure 5B, when the fluid coupling element 108 engages against the inner edge of the connector body, an inlet fluid channel 514 (not completely visible) and an outlet fluid channel 516 is provided. These channels are fluid tight, meaning that fluid flowing within them cannot leak or otherwise escape. The inlet fluid channel is fluidly coupled or connected to the fluid inlet hole of the connector body. The outlet fluid channel is fluidly coupled or connected to the fluid outlet hole of the connector body. The dotted line in Figure 5B shows the outlet fluid channel 512. More specifically, the inlet fluid channel 514 extends from the inlet fluid hole 406a of the connector body to the first portion of the thermal transfer system 116a. The inlet fluid channel includes the inlet pocket 502 and the inlet opening 506 through the fluid coupling element. The outlet fluid channel 516 extends from the first portion of the thermal transfer system 116a to the outlet fluid hole 406b (which is partially visible in Figure 5B). The outlet fluid channel includes the outlet opening 508 through the fluid coupling element and the outlet pocket 504. In this way, fluid can flow from the inlet fluid hole into the inlet pocket, along the inlet opening and into the first portion of the thermal transfer system, and subsequently, from the first portion of the thermal transfer system into and along the outlet opening to the outlet pocket, through the outlet pocket to the outlet fluid hole. In some examples, the fluid coupling element 308 is rotatable relative to the connector body, with respect to the longitudinal axis. For this reason, the longitudinal axis is also referred to as a rotation axis herein. This facilitates assembly of the fluid coupling element and the connector body as the fluid coupling element 308 can be rotated into a plurality of different angular positions, each of which the aforementioned inlet and outlet fluid channels are provided. In the specific example shown in Figure 5A, the inlet and outlet pocket 502, 504 extend circumferentially around the longitudinal or rotation axis. That is, the pockets each define an arc segment of a circle. The angle subtended by this arc segment is between 5 degrees to 90 degrees, more preferably 20 to 70 degrees. As noted above, this range of different angles (i.e. different angular positions) facilitates assembly of the fluid coupling element and the connector body because the inlet fluid hole or outlet fluid hole of the connector body can fluidly couple with the respective pocket over a range of different angles. If a pipe forming the second portion 116b of the thermal transfer system is to be fluidly connected to the fluid inlet and outlet holes 406a, 406b of similar diameter, the maximum angle by which the fluid coupling element 308 can rotate with the connector body will be smaller. In general, this angle is around 1 to 3 degrees. More generally, the inlet and outlet pocket extend around the rotation axis so that, when the fluid coupling element is rotated with respect to the connector body, a plurality of different rotational positions are defined, each of permits the fluid coupling between (i) the fluid inlet hole and the fluid outlet hole; and (ii) the inlet pocket and outlet pocket, respectively. In the specific example shown, the fluid coupling element can be rotated up to around 70 degrees relative to the connector body without affecting the flow of fluid through the inlet fluid and outlet fluid channels. The retaining element 310 shown in Figure 5B may allow rotation but otherwise prevent motion along the longitudinal axis (i.e. axial movement of the fluid coupling element 308 relative to the connector body). Figure 6 is a perspective view of a retaining element 310, according to an embodiment. In the specific example shown, the retaining element is a circlip. The circlip includes a partial or incomplete ring 602, which terminates at either end with a plier member 604a, 604b. The ring may have an outer diameter which is slightly greater than the internal diameter of the opening through the connector body so that the ring is deformed, as it is fitted within the connector body. This deformation tends to urge the plier members 604a, 604b outward or away from one another and into contact with the fluid coupling element, when in use. This secures or holds the fluid coupling element effectively in place during use. It will be understood that the circlip of Figure 6 and fluid coupling element of Figure 5A will, when fitted within the connector body, extend completely around the inner circumferential edge of the opening through the connector body. In some examples, the ring includes a groove or ridge 606 running along all or a portion of its peripheral or exterior edge. The connector body may include a complementary ridge or groove for mating with this feature 606. The groove or ridge 606 improves securement of the retaining element within the connector body by restricting axial movement of the retaining element. Figure 7 is a method flow diagram 700, describing how to retrofit an as-manufactured immersion heater boss so that it is suitable as an access point for the aforementioned thermal transfer system. In step 702, a connector body is provided, for example as shown in Figure 4. In step 704, a fluid coupling element, for example, as shown in Figure 5A, is located within the connector body so as to engage against its inner edge. This engagement provides or generates a fluid-tight inlet fluid channel and a fluid-tight outlet fluid channel, which are in fluid communication with the fluid inlet hole and the fluid outlet hole, respectively. In step 706, the connector body is coupled to the as-manufactured immersion heater boss to thereby form the retrofit immersion heater boss. This may involve turning or screwing the as-manufactured heater boss onto the threaded coupling provided by the connector body. Figure 8 is a method flow diagram 800, describing how to retrofit an as-manufactured unvented tank so that it can be thermally coupled with an external heat source (e.g., a compute unit). The unvented tank includes a port on which an as-manufactured immersion heater boss is installed. In step 802, the as-manufactured immersion heater boss is decoupled or removed from the port of the unvented tank. This may involve unscrewing the boss from its threaded connection with the port. In step 804, a connector body is provided, for example as shown in Figure 4, and then coupled to the port of the unvented tank. This may involve screwing or turning the connector body onto the threaded coupling provided by the port. If the port is located on a lateral wall of the tank, it desirable that the fluid inlet and outlet holes 406a, 406b are directed downwards (i.e. coincident with the direction of gravity), following this coupling operation. This facilitates insertion of the first portion of the thermal transfer system (e.g., a tank pipe defining two open ends and which forms a II-shape) into the unvented tank, for example, by avoiding colliding into the inner walls of the tank. While one or more spacers can be interposed between the connector body and the unvented tank for this purpose, it is not a convenient solution. A rotatable coupling element addresses this problem: the coupling element and the first portion of the thermal transfer system can rotate with respect to the connector body to facilitate insertion of the first portion of the thermal transfer system within the tank. In step 806, the first portion of the thermal transfer system (e.g. a tank pipe defining two open ends and which forms a U-shape) is inserted through the opening in the connector body and into the unvented tank. In step 808, a fluid coupling element, for example, as shown in Figure 5A, is located within the connector body so as to engage against its inner edge. This engagement provides or generates a fluid-tight inlet fluid channel and a fluid-tight outlet fluid channel, which are in fluid communication with the fluid inlet hole and the fluid outlet hole, respectively. In step 810, the first portion 116a of the thermal transfer system is fluidly connected to the inlet fluid channel and outlet fluid channel. This may involve securing or connecting one end of the tank pipe to the inlet fluid channel and the opposing end of the tank pipe to the outlet fluid channel. In step 812, the as-manufactured immersion heater boss is coupled to the connector body. This may involve turning or screwing the as-manufactured heater boss onto the threaded coupling provided by the connector body. In some examples, the method further comprises, in optional step 814, coupling the second portion 116b of the thermal transfer system to the inlet fluid hole and the outlet fluid hole of the connector body to thereby provide a channel for fluid to flow from the compute unit into and out from the unvented tank via the port and the boss. Figure 9 is a method flow diagram, describing how to provide or manufacture the components, which form the retrofit immersion heater boss in Figure 3 (but excluding the as-manufactured immersion heater boss and its heating element). In step 902, the method comprises providing a fluid coupling element, connector body and optionally a retaining element, as described in relation to Figure 5A, 4, and 6, respectively. Although this is described as a unitary step, it will be understood that the fluid coupling element and connector body can be fabricated in different steps and using a different manufacturing technique. The components can be provided by a process selected from a group comprising: casting, injection moulding, power metallurgy processing (sintering, hot or cold isostatic pressing and sintering), and / or additive manufacturing. Possible additive manufacturing techniques include 3-D printing; Direct metal laser sintering; Selective Laser sintering; Stereolithography; Fused deposition modelling; Field assisted sintering technique; Spark assisted sintering; Electron beam sintering; and / or Direct metal deposition. If the process involves additive manufacturing, the method may further comprise a step of obtaining an electronic file representing a geometry of the or each component; and controlling an additive manufacturing apparatus to generate, over one or more additive manufacturing steps, the or each component according to the geometry specified in the electronic file. Figure 10 is a method flow diagram, describing how to heat water contained within an unvented tank using the system shown in Figure 1. In step 1002, a computing task is executed by the compute unit. This process releases heat. Ordinarily, this would be regarded as a waste product of the computation. In step 1004, coolant is flowed or passed around or through a thermal transfer system, as shown in Figure 1 for example. The thermal transfer system includes a channel which extends from the compute unit, in particular from a position in thermal contact with the compute unit, into the unvented tank containing water via the port and retrofit boss of the unvented tank. Heat generated by the compute unit can therefore be transferred to the coolant and then to the water within the unvented tank. It will be understood that the channel is fluid-tight so that coolant flowing through the thermal transfer system remains isolated from the water contained within the unvented tank. Figure 11 is a perspective view of a fluid coupling element 1100, according to an alternative embodiment. The fluid coupling element 1100 may substitute the fluid coupling element 308 in the system shown in Figure 1. The fluid coupling element 1100 is in the form a sleeve, which is insertable into the connector body 400. Preferably, although not necessarily, the fit between the fluidcoupling element and the connector body is fluid-tight. The sleeve includes a rib 1108 extending around its peripheral or exterior surface, which is arranged between an upper 1106a and lower lip 1106b. The rib acts as a partition between the upper and lower lips, which defines an inlet pocket 1102 and an outlet pocket 1104, which extend around the sleeve. The rib and lips may extend radially around 5mm. In some examples, a gasket or similar elastomeric seal can be provided against the rib to facilitate the formation of a fluid-tight seal with the connector body. As shown, one of the lips (the upper lip 1106a in Figure 11) includes two cut-out portions: one for an inlet and one for an outlet. The rib includes one cut-out portion (either for the inlet or outlet). This defines two axial channels 1110, 1112, which form part of the inlet fluid channel and outlet fluid channel, when the sleeve is inserted into the connector body. One of the axial channels extends through the upper lip 1106a into the outlet pocket, and one which extends through the upper lip 1106a into the inlet pocket. The axial channels are also sized to receive the inlet and outlet side of the first portion 116a of the thermal transfer system. In the specific example shown, the inlet and outlet pocket 1102, 1104 extend completely around the longitudinal axis of the sleeve so that the fluid coupling element can be arranged in any rotational position with respect to the connector body, without affecting the fluid coupling between (i) the fluid inlet hole of the connector body and inlet pocket; and (ii) the fluid outlet hole of the connector body and the outlet pocket. Figure 12 is a perspective view of a partial longitudinal cross section, showing the fluid coupling element of Figure 11A fitted within the connector body 302 (e.g., as shown in Figure 4). The outlet side of the first portion 116a and the second portion 116b of the thermal transfer system are shown received within the axial channel 1112 and outlet fluid hole 406b, respectively. Figure 13A is a perspective view of a connector body 1300, according to an alternative embodiment. The connector body is a variant of the connector body shown in Figure 4, in which the inner surface of the connector body is specially shaped to receive the first portion 116a of the thermal transfer system. More specifically, the connector body comprises internal boss surfaces 1302a, 1302b, 1302b, which are arranged to define a first slot 1304a for receiving an inlet side of the first portion 116a of the thermal transfer system, and a second slot 1304b for receiving an outlet side of the first portion 116a of the thermal transfer system. The fluid inlet hole (not shown) and fluid outlet hole 406b are located within the space defined by the first and second slot, respectively. Turning to Figure 13B, a perspective view of a retrofit immersion heater boss 1400 is shown. The retrofit immersion heater boss comprises a fluid coupling element 1402 fitted within a variant of the connector body 1300 of Figure 13A, comprising an internal retaining element boss surface 1412, and held in place with a retaining element 1404. In this embodiment, the first portion 116a of the thermal transfer system constitutes (or functions as) the fluid coupling element. A plurality of brackets 1414 are shown between the inlet and outlet side of the first portion of the thermal transfer system. The brackets help ensure robustness. In the specific example shown, the first portion 116a of the thermal transfer system is a pipe 1402, comprising a ll-bend and having flattened or swaged ends 1406a, 1406b. The ends are shown as open in Figure 13B but it will be understood that they will be plugged, covered or otherwise blocked (e.g., by crimping). Each of its ends or end portions is sized to snugly fit into the respective slot 1304a, 1304b defined by the connector body. The pipe also includes two openings (which are not visible in Figure 13B): one for fluidly coupling to the fluid inlet hole of the connector body and the other for fluidly coupling to fluid outlet hole of the connector body. As a result, when the pipe 1402 is arranged against the inner edge of the connector body, an inlet fluid channel and an outlet fluid channel is defined in fluid communication with the fluid inlet and fluid outlet holes. In some examples, the pipe 1402 is held securely in place using a retaining element 1404, which in Figure 13B is shown in the form of a clip. The clip comprises a body, which is shaped to snugly fit over the pipe 1402 and internal boss surfaces 1302a, 1302b, when the pipe is arranged against the inner edge of the connector body. In some examples, the clip includes curled ends 1408 and a tab 1410. The curled ends 1408 are press fit into the space between boss surfaces 1302c, 1412 to secure the retaining element in place. To an extent, the curled ends also impart strength to the clip. The tab extends away from the body of the clip to define an abutment surface that abuts against the end of internal boss surface 1302b as the clip is inserted into the connector body (in the direction denoted by the arrow in Figure 13B). This facilitates ease of assembly of the retrofit immersion heater boss 1400. In a specific use case, the unvented tank may be made according to a UK standard and the components described above are adapted for the UK standard. Other standards (e.g. US and European standards) are, of course, possible. The example dimensions provided below are for an unvented tank according to a UK standard. Connector body dimensions: • Opening 402: inner diameter is around 60 to 65 mm; • Body length along the longitudinal axis: around 40 to 70 mm; • Fluid inlet hole and fluid outlet hole diameter 406a, 406b: around 10 to 25 mm (depending on the method of fitting the inflow pipe and return pipe to the holes 406a, 406b). For a Speedfit® connector, larger hole sizes are required (20mm or more); • Coupling portions 404a, 404b: inner diameter is 2-¼ inch (57mm) British Standard Pipe, BSP, Thread,; outer diameter ~2.6 inch (66mm); thread length around 8 to 12 mm. BSP refers to the tube diameter which is to be coupled with the coupling portion (i.e. thread). The inner diameter, of the coupling portion, will be different to the BSP value. It will be understood that 2-1 / 3 inch BSP thread is one example of a thread size. Other thread sizes, such as 1-3 / 4 inch inner diameter BSP, are also possible and widely used in the UK. ; • hex-flange 408: minimal diameter (i.e., between opposing flat edges) of around 85mm; • axial offset between the coupling portions: from 0 to 3mm; and • groove 410 - an inner diameter of around 60 to 65 mm, with a width of around 2 to 3mm. In a specific example, 63.00mm by 2.15mm. Tank pipe dimensions an outer diameter of around 10mm. If swaged, the cross section of the pipe may be 12.5 by 4 mm. Inlet fluid channel and outlet fluid channel a diameter in the range of 5mm to 22mm. Although the invention has been described in terms of preferred 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 illustration herein. It will be understood that the numbering of the method flow diagrams is not intended to impose a strict ordering of those steps. For example, the embodiments described refer to an unvented tank but it will be understood that the approach described can be applied to other forms of tank, e.g., vented tanks and tanks without thermal insulation. For example, method steps 806 to 810 may take place substantially at the same time.

Claims

1. An assembly for retrofitting an immersion heater boss of a tank, the assembly comprising:a connector body, comprising:an opening through which an immersion heater element of the immersion heater boss can pass freely;a fluid inlet hole and a fluid outlet hole; andrespective coupling portions for releasably securing the connector body to the immersion heater boss and to the tank; anda fluid coupling element configured to engage with an inner edge of the connector body to provide an inlet fluid channel and an outlet fluid channel in fluid communication with the fluid inlet hole and fluid outlet hole, respectively, without preventing free passage of the immersion heater element of the immersion heater boss through the opening of the connector body.

2. The assembly according to claim 1, in which the fluid coupling element, when engaged against the inner edge of the connector body, is operable to rotate about a rotation axis relative to the connector body by a predetermined angle, while maintaining fluid communication between (i) the inlet fluid channel and fluid inlet hole; and (ii) the outlet fluid channel and the fluid outlet hole.

3. The assembly according to claim 1 or 2, in which the fluid coupling element defines an inlet pocket and an outlet pocket, which form part of the inlet and outlet fluid channel, respectively, when the fluid coupling element is engaged against the inner edge of the connector body,wherein, the inlet and outlet pocket extend around the rotation axis so as to define a plurality of different rotational positions, and for each of these rotational positions, the fluid inlet hole and fluid outlet hole can respectively fluidly couple to the inlet pocket and outlet pocket.

4. The assembly according to claim 3, in which the inner edge of the connector body includes a groove or a lip for locating the fluid coupling element into a position in which the fluid inlet hole and fluid outlet hole overlaps with the inlet and outlet pocket, respectively.

5. The assembly according to claim 3 or 4, in which the inlet and outlet pocket extend circumferentially about the rotation axis.

6. The assembly according to any one of claims 3 to 5, when dependent on claim 2, in in which an angle subtended by the inlet and / or outlet pocket is greater than or equal to the predetermined angle.

7. The assembly according to any one of claims 2 to 6, in which the predetermined angle is between land 360 degrees, more preferably between 2 and 90 degrees.

8. The assembly according to any one of claims 2 to 7, wherein the inlet and outlet fluid hole are offset with respect to one another along the rotation axis.

9. The assembly according to any one of the preceding claims, in which a portion of the inlet fluid channel and a portion of the outlet fluid channel are each defined by a respective opening, which extends through a body of the fluid coupling element.

10. The assembly according to any one of the preceding claims, in which the inlet fluid channel and outlet fluid channel have a diameter in the range of 5mm to 30mm, more preferably 10 to 22mm.

11. The assembly according to any one of the preceding claims, comprising a retaining element configured to releasably secure the fluid coupling element against the inner edge of the connector body.

12. The assembly according to claim 11, wherein the retaining element is a circlip.

13. A method of retrofitting an immersion heater boss, comprising: providing a connector body, comprising:an opening through which an immersion heater element of the immersion heater boss can pass freely;a fluid inlet hole and a fluid outlet hole; anda coupling element for releasably securing the connector body to the immersion heater boss;engaging a fluid coupling element against an inner edge of the connector body to provide an inlet fluid channel and an outlet fluid channel in fluid communication with the fluid inlet hole and the fluid outlet hole, respectively; andcoupling the connector body to the immersion heater boss.

14. A method of retrofitting a tank, comprising a port on which an immersion heater boss with an immersion heater element is installed, the method comprising:decoupling the immersion heater boss from the port of the tank;providing a connector body, comprising:an opening through which an immersion heater element of the immersion heater boss can pass freely;a fluid inlet hole and a fluid outlet hole; andrespective coupling elements for releasably securing the connector body to the immersion heater boss and to the port;coupling the connector body to the port;engaging a fluid coupling element against an inner edge of the connector body to provide an inlet fluid channel and an outlet fluid channel in fluid communication with the fluid inlet hole and the fluid outlet hole, respectively;inserting a pipe through the opening in the connector body into the tank;securing the pipe to the inlet fluid channel and the outlet fluid channel to thereby fluidly connect the fluid inlet hole with the fluid outlet hole; andcoupling the immersion heater boss to the connector body.

15. A system, comprising:a tank, comprising a port on which a boss with an immersion heater element is installed; anda compute unit, comprising a thermal transfer system configured to transfer thermal energy generated by the compute unit into the tank, wherein, the thermal transfer system defines a channel for fluid flow, which extends from the compute unit into, and out from, the tank through said port and boss.

16. The system according to claim 15, in wherein the channel for fluid flow comprises an inflow pipe extending from the compute unit to a fluid inlet hole of the boss, a return pipe extending from a fluid outlet hole of the boss, and a tank pipe arranged within the tank, which fluidly connects the fluid inlet and fluid outlet hole.

17. A method of installing the system according to claims 15 or 16, comprising:inserting a first portion of the thermal transfer system into the tank via the port;coupling the boss to the tank;fluidly coupling the first portion of the thermal transfer system to an inlet fluid hole and outlet fluid hole of the boss; andcoupling a second portion of the thermal transfer system, which resides outside the tank and which extends from the compute unit, to the inlet fluid hole and the outlet fluid hole of the boss to thereby provide a channel for fluid to flow from the compute unit into and out from the tank via the port and the boss.

18. A method of providing the assembly of any one of claims 1 to 12, wherein the assembly is provided by a process selected from a group comprising:casting;injection moulding;a powder metallurgy route, comprising:sintering; orhot or cold isostatic pressing and sintering; and / oran additive manufacturing route, comprising:3-D printing;Direct metal laser sintering;Selective Laser sintering;Stereolithography;Fused deposition modelling;Field assisted sintering technique;Spark assisted sintering;Electron beam sintering; and / or Direct metal deposition.

19. The method of claim 18, being an additive manufacturing route, wherein the method comprises:obtaining an electronic file representing a geometry of the or each component making up the assembly of any one of claims 1 to 12; andcontrolling an additive manufacturing apparatus to generate, over one or more additive manufacturing steps, the or each component according to the geometry specified in the electronic file.5 20. A computer program product comprising computer executable instructions that,when executed by a processor, cause the processor to control a manufacturing apparatus to generate the or each component making up the assembly of any one of claims 1 to 12.

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