A heat exchanger

Abstract

A heat exchanger for cooling a fluid. The heat exchanger comprising a first end and a second end, and a tapered structure such that one end is narrower than the other end. A plurality of components form the heat exchanger including a core body, a first shell surrounding the core body, a second shell surrounding the first shell, an outer body surrounding the second shell, a plurality of slits provided on at least one of the plurality of components forming the heat exchanger, wherein the slits are configured to allow a fluid to pass through for cooling, and a liquid channel provided between the first and second shells, the liquid channel configured to receive a liquid to cool the fluid passing through the heat exchanger.

Description

[0001] A HEAT EXCHANGER

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a heat exchanger. More particularly, but not exclusively, it relates to a heat exchanger for a cryocooler.

[0004] BACKGROUND OF THE INVENTION

[0005] Cryogenic systems are used for producing, maintaining and storing cryogenic liquids or cryogens, which are liquefied gases, and other substances at very low temperatures. Cryogens are produced by liquefying gases by cooling them until they change state to liquid. Cryogenic systems are now widely used in a number of different industries as they have proven to be useful in many different processes.

[0006] A main component of cryogenic systems are heat exchangers. Heat exchangers are used to transfer heat to or from a working fluid flowing through the system. As fluid passes through a heat exchanger, the fluid may be cooled towards a desired temperature.

[0007] A specific type of heat exchanger in a cryocooler system is an aftercooler. Aftercoolers in some systems dissipate heat from a cold head and transfers the heat energy externally from the system.

[0008] Heat exchangers come in different shapes, designs, and are manufactured from different materials. The purpose of such designs is typically for improving cooling performance for system use cases.

[0009] Heat exchangers may also be used in non-cryogenic settings. For example, cooling hot gas from a compressor.

[0010] In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

[0011] For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

[0012] It is an object of the present invention to provide a heat exchanger which overcomes or at least partially ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014] According to a first aspect of the invention, there is provided a heat exchanger for cooling a fluid comprising: a first end and a second end, wherein the heat exchanger comprises a tapered structure such that one end is narrower than the other end and wherein the heat exchanger comprises: a longitudinal axis; a plurality of components forming the heat exchanger comprising: a core body; a first shell surrounding the core body; a second shell surrounding the first shell; an outer body surrounding the second shell; a plurality of slits provided on at least one of the plurality of components forming the heat exchanger, wherein the slits are configured to allow a fluid to pass through for cooling; and a liquid channel provided between the first and second shells, the liquid channel configured to receive a liquid to cool the fluid passing through the heat exchanger.

[0015] In some configurations, the heat exchanger comprises a generally frustoconical shape.

[0016] In some configurations, the plurality of slits extend generally parallel the longitudinal axis of the heat exchanger.

[0017] In some configurations, the plurality of slits are provided on at least one of the walls of the at least one of the plurality of components.

[0018] In some configurations, the plurality of slits are provided on the first shell. In some configurations, the plurality of slits are provided on the second shell.

[0019] In some configurations, the plurality of slits are provided on two of the components forming the heat exchanger.

[0020] In some configurations, the plurality of slits are provided on both the first shell and the second shell such that heat from the fluid passing through the slits can transfer to the liquid in the liquid channel via either side of the channel.

[0021] In some configurations, the first shell is an inner shell and the second shell is an outer shell.

[0022] In some configurations, the first shell and the second shell are concentric such that they have a common centre along a longitudinal axis of the heat exchanger.

[0023] In some configurations, the first end is a top end of the heat exchanger and the second end is a bottom end of the heat exchanger.

[0024] In some configurations, one or both of the first shell and the second shell comprises a taper towards one end of the heat exchanger.

[0025] In some configurations, one or both of the first shell and the second shell comprises a taper towards the first end of the heat exchanger.

[0026] In some configurations, the heat exchanger further comprises a liquid channel inlet configured to allow entry of liquid to flow into the heat exchanger and into the liquid channel, and a liquid channel outlet configured to allow exit of liquid to flow out of the heat exchanger from the liquid channel.

[0027] In some configurations, both the liquid channel inlet and the liquid channel outlet are located at or towards the second end.

[0028] In some configurations, the liquid channel inlet and liquid channel outlet are coaxial and are spaced the same or approximately the same distance from the second end.

[0029] In some configurations, the liquid channel inlet and the liquid channel outlet are on generally opposite sides of the heat exchanger.

[0030] In some configurations, the liquid channel is a helical flow channel.

[0031] In some configurations, the liquid channel has double heliconical flow path for heat exchange fluid to travel up and down between the inner and outer shells.

[0032] In some configurations, the liquid channel is arranged around at least the core body and the first shell. In some configurations, the heat exchanger further comprises a third shell surrounding the second shell.

[0033] In some configurations, the heat exchanger further comprises a second liquid channel located between the third shell and the outer body.

[0034] In some configurations, the core body comprises a hollow interior.

[0035] In some configurations, one or more of the following are directly adjacent and joined together: a) the core body and first shell; b) the first shell and the second shell; and c) the second shell and the outer body.

[0036] In some configurations, a weld, braze, gasket or O-ring seals the components that are directly adjacent together.

[0037] In some configurations, the heat exchanger is formed from aluminium.

[0038] In some configurations, the heat exchanger is an aftercooler.

[0039] In some configurations, the slits are configured to receive one or a combination of helium gas, neon gas, argon gas, krypton gas, hydrogen gas, or nitrogen gas.

[0040] According to another aspect of the invention, there is provided a pulse tube cryocooler comprising: a regenerator; a pulse tube; a compressor; and a heat exchanger as provided in any one of the previous clauses;

[0041] According to another aspect of the invention, there is provided a Stirling cryocooler comprising: a regenerator; a heat exchanger as claimed as provided in the previous clauses; and a Stirling piston configured to be at least partially received within the hollow interior of the core body.

[0042] According to another aspect of the invention, there is provided a method of forming a heat exchanger comprising: forming a plurality of components comprising a core body, a first shell, a second shell and an outer body as claimed in any one of claims 1 to 28; forming slits on at least one of the plurality of components of the heat exchanger; and assembling and joining the plurality of components together to form the heat exchanger.

[0043] In some configurations, wire EDM is used to form the slits.

[0044] In some configurations, the plurality of components of the heat exchanger are joined together by welding or brazing.

[0045] According to another aspect of the invention, there is provided a heat exchanger for cooling a fluid comprising: a plurality of components forming the heat exchanger comprising: a first shell; a second shell; a liquid channel provided between the first and second shells, the liquid channel configured to receive a liquid to cool a fluid passing through the heat exchanger; and a plurality of slits are provided on at least the first shell and second shell, wherein the slits are configured to allow the fluid to pass through for cooling such that heat from the fluid passing through the slits can transfer to the liquid in the liquid channel via either side of the channel.

[0046] In some configurations, the heat exchanger comprises a first end and a second end, the heat exchanger comprises a tapered structure such that one end is narrower than the other end and wherein the heat exchanger comprises a longitudinal axis.

[0047] Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

[0048] As used herein the term "and / or" means "and" or "or", or both.

[0049] As used herein "(s)" following a noun means the plural and / or singular forms of the noun.

[0050] The term "comprising" as used in this specification and claims means "consisting at least in part of". When interpreting statements in this specification and claims which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The invention will now be described by way of example only and with reference to the drawings in which:

[0053] Figure 1 shows a cross section of a heat exchanger.

[0054] Figure 2 shows a cross section of a pulse tube cold head coupled to the heat exchanger.

[0055] Figure 3 shows a cross section of a Stirling cold head coupled to the heat exchanger.

[0056] Figure 4 shows an exploded view of the cross section of the heat exchanger.

[0057] Figure 5 shows a perspective view of a first shell of the heat exchanger with a helical flow pathway.

[0058] Figure 6 shows a perspective view of a first shell of the heat exchanger.

[0059] Figure 7 shows a cross section of the first shell of the heat exchanger.

[0060] Figure 8 shows a perspective view of a second shell of the heat exchanger.

[0061] Figure 9 shows a close up view of the second shell with slits.

[0062] Figure 10 shows a perspective view of an outer body of the heat exchanger.

[0063] Figure 11 shows a cross section of the outer body of the heat exchanger.

[0064] Figure 12 shows a cross section of a three-shelled heat exchanger.

[0065] Figure 13 shows an end view of the three-shelled heat exchanger.

[0066] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0067] According to various aspects of the present invention as illustrated in figures 1 -13, there is provided a heat exchanger 100 which will now be described. It will be appreciated that these figures illustrate the general principles of the structure and construction, and that the invention is not limited to the precise configurations illustrated.

[0068] Figure 1 shows a heat exchanger 100. The heat exchanger 100 is part of a system to transfer heat to or from a working fluid for heating or cooling of the fluid. In some configurations, the heat exchanger 100 is configured to cool the working fluid. In some configurations, the working fluid is helium. In other configurations, the working fluid may be hydrogen, oxygen, air, hydrocarbon gases, carbon dioxide, neon gas, argon gas, krypton gas, or nitrogen gas. The working fluid may be a combination of more than one gas.

[0069] In some configurations, such as in a cryocooling application, the heat exchanger is configured to transfer heat away from a fluid to cool the fluid as it passes through the heat exchanger.

[0070] In some configurations, the cryocooler is a pulse tube cryocooler 1000 having a pulse tube cold head. In some configurations, the heat exchanger 100 is located between a pressure wave generator which produces a gas pressure wave, and a pulse tube 201 which provides cooling to the system. In some configurations, the heat exchanger 100 is bolted or otherwise fixed to a top plate of the cryocooler. An example of a pulse tube cold head 200 coupled with a heat exchanger 100 is shown in figure 2, and discussed in more detail later in the specification.

[0071] In other configurations, the cryocooler is a Stirling cryocooler 2000 having a Stirling cold head. The heat exchanger 100 may be located between a pressure wave generator and the Stirling cold head 300. A Stirling cryocooler may provide more cooling power than a pulse tube cryocooler. In these configurations however, there may be an increased need to remove or reject heat from the cold head of the cryocooler. An example of a Stirling cold head coupled with a heat exchanger 100 is shown in figure 3, and discussed in more detail later in the specification.

[0072] In some configurations, the heat exchanger 100 is an aftercooler in a cryocooler system. The aftercooler is configured to remove heat from the cryocooler assembly which may be generated within the system such as by compressor. The aftercooler design as described herein may be particularly useful in a Stirling cryocooler, to reject heat from the cryocooler.

[0073] It should be appreciated the heat exchanger 100 may be used in other such devices as a compressor.

[0074] As shown in figure 1, there is a heat exchanger 100. The heater exchanger has a generally frustoconical shape. The heat exchanger 100 has a first end 101 and a second end 102. The heat exchanger 100 has a tapered structure such that one end is narrower than the other end. I.e. the heat exchanger 100 narrows from the second end 102 to the first end 101 along an axial direction (axial axis shown by the dotted line in figure 4). In some configurations, the first end 101 is located the top of the heat exchanger 100, and the second end 102 is the bottom, i.e. the top end 101 of the heat exchanger 100 is narrower in diameter and / or has a smaller cross-sectional area compared to the bottom end 102.

[0075] The tapered structure of the heat exchanger 100 can provide advantages over a cylindrical structure. For example, a tapered heat exchanger 100 can provide a larger heat exchange area near the bottom end 102, making the heat exchanger 100 more effective at cooling.

[0076] Additionally, the taper towards the top end 101 may reduce the length of the flow path through the heat exchanger 100. In a configuration where the heat exchanger 100 is used in a cryocooling application, the tapered shape may allow for a pressure wave generator with a larger diameter diaphragm to be used.

[0077] In some configurations, a plurality of components form the heat exchanger 100 comprising a core body 103, a first shell 110, a second shell 120 and an outer body 130, as best shown in figure 4 showing an exploded view of four forementioned components of the heat exchanger 100.

[0078] In some configurations, the heat exchanger 100 is formed from only the four components: the core body 103, the first shell 110, the second shell 120 and the outer body 130. In other configurations, the heat exchanger 100 may include other components, for example as shown in figures 12 and 13 and explained in more detail later.

[0079] The heat exchanger 100 comprises a core body 103. In some configurations, the core body 103 comprises a hollow interior 107. The hollow interior 107 of the core body 103 may receive at least partially a piston 301 of a Stirling cold head, as shown in figure 3. In other configurations, the core body 103 may be solid e.g. in application to a linear pulse tube cryocooler. In configurations where the inner shell 1 10 is a separate component to the core body 103 this provides for the ability to create slits 104 on the inner shell. Slits 104 may made by EDM wirecutting which relies on cutting from the edge of the material, a close-up view of such slits 104 are shown in figure 9. With reference to figure 7, the shells have fins 108 as provided by the slits 104. In some configurations, for example those where the heat exchanger 100 is used in a cryocooling application, the piston 301 may move with a reciprocal motion within or partly within the hollow interior 107. In such configurations, the piston 301 may drive a flow of a fluid through the heat exchanger 100 and cryocooling system.

[0080] The heat exchanger 100 further comprises a first shell 110 and a second shell 120 surrounding the core body 103. The first shell 110 is located around the core body 103. In some configurations the first shell 1 10 engages with and is directly adjacent the core body 103.

[0081] The second shell 120 is located around the first shell 1 10. In some configurations the second shell 120 engages with and is directly adjacent the first shell 1 10.

[0082] As shown in figure 1 , a liquid channel 115 is provided between the first shell 1 10 and the second shell 120. The liquid channel 1 15 is sandwiched between the two shells 1 10, 120. The liquid channel 115 provides a region and / or pathway for a heat exchange fluid to pass through to carry heat away (or to) components of the heat exchanger. As the liquid channel 115 is between two components (e.g. the first and second shells 110, 120) heat may be transferred efficiently as the heat can transfer to / from the fluid from two sides of the liquid channel 1 15.

[0083] In some configurations, as shown in figure 5, the liquid channel 1 15 is a radial flow channel to allow supply and return of heat exchange fluid to circulate through the liquid channel 1 15 between first and second shells 1 10, 120. As provided by the arrows and lines in figure 5, a pathway of the heat exchanger is shown. The heat exchange fluid can flow in from a region towards the bottom of the heat exchanger 100 and follow a helical flow path up (as shown by dot-dash lines) to the top of the heat exchanger, and then back down (as shown by a solid line) towards the bottom of the heat exchanger to exit the liquid channel 1 15. In these configurations a double heliconical flow path (travelling up and down between the shells) is provided.

[0084] In some configurations, there are two distinct flow paths, a first flow path comprising a helical, heliconical, double helical or double heliconical element and a radial element, and a second flow path being axial through the hollow interior 107. As described above, the second flow path is provided by or partially provided by the slits. In some configurations, a liquid flows through the first flow path and a gas flows though the second flow path. In some configurations, the first flow path has a radial inlet element and a radial outlet element, Between the inlet element and outlet element of the first flow path there may be an upwards heliconical element, followed by a downwards heliconical element as shown in figure 5.

[0085] In some configurations, a liquid pathway may be defined liquid pathway 116 as provided in figure 5 to guide the heat exchanger fluid to travel in a particular way or direction between the shells. In other configurations, the liquid path is not defined as shown in figure 6 where the outer surface of the inner 110 is smooth. Other pathways may be provided on this surface to provide the desired heat transfer performance or other performance.

[0086] The geometric features of liquid flow channel 115 as provided by the first and second shells 110, 120 can promote consistent flow and temperature distribution through the heat exchanger.

[0087] As shown by the entry and exit of the flow path, the liquid channel inlet 105 and outlet 106 are both provided towards the bottom / first end 101 of the heat exchanger 100. In some configurations, the liquid channel inlet 105 and the liquid channel outlet 106 are aligned coaxially, such that they share a common central axis.

[0088] The heat exchanger 100 has a longitudinal axis. In some configurations, the first shell 110 and the second shell 120 are concentric such that they have a common centre along the longitudinal axis.

[0089] In some configurations, the heat exchanger 100 the general shape of the heat exchanger body is rotationally symmetric. In other configurations, the heat exchanger 100 is not rotationally symmetric.

[0090] In some configurations, the first shell 110 comprises a taper towards one end of the heat exchanger 100.

[0091] In some configurations, the second shell 120 comprises a taper towards one end of the heat exchanger 100.

[0092] In some configurations, both the first shell 110 and the second shell 120 tapers towards the first end 101 of the heat exchanger 100. In some configurations, the first shell 110 is an inner shell and the second shell 120 is an outer shell. The first / inner shell 1 10 being adjacent the core body 103, and the second / outer shell 120 being adjacent the outer body 130 of the heat exchanger 100.

[0093] In some configurations, a liquid channel 115 is provided between the first and second shells 110, 120. The liquid channel 115 is configured to receive water to cool a fluid passing through the heat exchanger 100. In some configurations, the liquid for cooling configured to enter and exit the liquid channel 1 15 is water. In some configurations, the water is water including additives such as a glycol based antifreeze-anticorrosive. It is anticipated other appropriate liquids may pass through the liquid channel 1 15 for cooling.

[0094] The liquid channel 115 in some configurations, is a helical flow channel, providing a passageway for cooling liquid e.g. waterto flow around the heat exchanger 100. The liquid channel 1 15 is arranged around at least the core body 103 and the first shell 1 10 of the heat exchanger 100.

[0095] In some configurations, the heat exchanger 100 further comprises an outer body 130 located around the second shell 120. In some configurations, the outer body 130 is the top plate of the cryocooler or compressor and serves to mount the heat exchanger to the rest of the machine and contain a helium pressure wave.

[0096] In some configurations, two or more of the described four components (core body 103, a first shell 110, a second shell 120 and an outer body 130) may be manufactured as a single component e.g. by advanced manufacturing techniques such as additive manufacturing.

[0097] In one configuration, the heat exchanger 100 has a dimension of an inside diameter being approximately 50mm, and outside diameter of approximately 200mm and a height of approximately 200mm.

[0098] In some configurations, the heat exchanger 100 has one or more additional shells. As shown in figure 12, there is a heat exchanger 100 with, a core body 103, a first shell 1 10, a second shell 120, a third shell 130, and an outer body 130. Compared to the earlier configuration described, this configuration includes an additional, third shell 130 (surrounding the second shell 120). As a result, there are also two liquid channels. A first liquid channel 115 between the first and second shells 1 10, and a second liquid channel 1 17 between the third shell, and outer body 140, 130. This configuration provides additional cooling as an additional liquid channel 117 is present and there is an increased cooling surface area.

[0099] The heat exchanger 100 has a liquid channel inlet 105, configured to allow entry of water to flow into the heat exchanger and into the liquid channel 1 15.

[0100] The heat exchanger 100 also has a liquid channel outlet 106, configured to allow exit of liquid e.g. water to flow out of the heat exchanger from the liquid channel 115.

[0101] As shown in figure 10, the liquid channel inlet 105 and liquid channel outlet 106 may be provided through the outer body 130. The inlet 105 and 106 may be provided by one or more of the outer body 130, second shell 120 and first shell 1 10.

[0102] In some configurations, the liquid channel inlet 105 is located at or towards the first end 101 of the heat exchanger 100. The first end 101 being the bottom end of the heat exchanger 100. In other configurations, the liquid channel inlet 105 is located at or towards the second end 102 of the heat exchanger 100.

[0103] In some configurations, the liquid channel outlet 106 is located at or towards a first end 101 of the heat exchanger 100. In other configurations, the liquid channel outlet 106 is located at or towards the second end 102 of the heat exchanger 100.

[0104] In some configurations, both the liquid channel inlet 105 and the liquid channel outlet 106 are located at the first / bottom end 101 of the heat exchanger 100. This design allows both entry and exit at the bottom end 101 of the heat exchanger 100. This may conveniently enable liquid entry and exit from a top plate of a pressure wave generator in configurations where the heat exchanger is located above the pressure wave generator.

[0105] Having both the liquid channel inlet and outlet 105, 106 at the bottom end 102 of the heat exchanger 100 can provide an advantage in assembly. It may allow cooling in-out conveniently connected within the top plate assembly of a cryocooler and assembly is not reliant on establishing a connection at the top of the heat exchanger. In some cryocooling applications, providing the liquid channel inlet and outlet 105, 106 at the top end 101 may be unwieldy as the liquid channels and any associated connecting channels would be located close to the cryocooling apparatus. As such it may be advantageous for both the liquid channel inlet and outlet 105,106 to be located to the bottom end 102 of the heat exchanger 100. In some configurations, the liquid channel inlet 105 and the water liquid channel outlet 106 are on generally opposite sides of the heat exchanger, as shown in figure 1 .

[0106] In some configurations, the liquid channel inlet 105 and liquid channel outlet 106 are co-planar and are spaced the same or approximately the same distance from the second end. In some configurations, the liquid channel inlet 105 has a diameter between 5mm and 30mm. In some configurations, the liquid channel inlet 105 and the liquid channel outlet 106 are collinear.

[0107] In some configurations, the liquid channel outlet 106 has a diameter between 5mm and 30mm for inlet or outlet.

[0108] In some configurations, gas flows from one end of the heat exchanger 100 to the other end. As the gas passes through the heat exchanger 100, heat is removed to cool the gas. The narrow internal slits 104 are provided for axial gas flow.

[0109] In some configurations, a plurality of slits 104 are provided in the heat exchanger 100 to allow gas to flow through, best shown in close-up figure 7. The slits 104 extend longitudinally along the heat exchanger 100. The slits 104 extend generally parallel the longitudinal axis of the heat exchanger 100. In some configurations, the slits 104 extend between the first end 101 and the second end 102 of the heat exchanger 100. The slits 104 are configured to allow gas for cooling to pass through the heat exchanger 100 where heat is transferred from the gas to the nearby liquid flowing through the liquid channel 115.

[0110] Slits 104 are provided on at least of one of the components forming the heat exchanger 100. In some configurations, the plurality of slits 104 are provided on at least one of the walls of the at least one of the plurality of components. The slits 104 may be provided on a surface of a wall of the component.

[0111] In some configurations, the respective component and slits 104 are formed as a single integral component. This should be understood that in these configurations, the slits 104 are formed on a single body of material e.g. the inner and / or outer shells 110, 120.

[0112] In some configurations, slits 104 are provided on two of the components forming the heat exchanger 100.

[0113] In some configurations, the first shell 1 10 comprises slits 104 on an inner wall 1 11 of the first shell 110, as shown in figure 6. In some configurations, the second shell 120 comprises slits 104 on an outer wall 121 of the second shell 11 1 , as shown in figure 8.

[0114] As shown in figures 1 and 4, in some configurations, slits 104 are provided on both the first shell 1 10 and the second shell 120 such that the slits and thus flow of gas is provided on both sides of the liquid channel 1 15. As gas flows through the slits 104, on either side of the liquid channel 1 15, the liquid flowing through the channel will absorb the heat from the gas passing through thus cooling it. Heat transfers from the gas to the liquid which is within the liquid channel 115. Slits 104 on both sides of the liquid channel 1 15 may have benefits such as more cooling surface area and shorter conduction path between flow streams, thus providing more effective heat exchange with reduced driving temperature difference whilst also reducing the volume of gas within the slits 104.

[0115] The slits 104 are narrow slots provided on wall surfaces of components of the heat exchanger 100. The slits 104 may have a width between 0.2mm and 2mm.

[0116] It should be appreciated that the number of slits may be a function of design drivers to produce the optimal heat exchanger performance. There may be a balance between number of slits, flow area, conductive area through non-slit material and cost to produce the slits. In some configurations, the slits 104 are provided by wire-cut EDM (electrical discharge machining). It should be appreciated by a person skilled in the art that other methods for forming the slits 104 may be used such as additive manufacturing or sawing.

[0117] In some configurations the heat exchanger 100 comprises a metal body. In some configurations, the heat exchanger 100 is aluminium as it has suitable heat transfer characteristics, is cost efficient, and facilitates ease of manufacturing. The heat exchanger 100 may be formed from other suitable high conductivity materials such as copper.

[0118] Following the description of the structure of embodiments of the present invention described above, a general description of the method of forming the heat exchanger 100 will now be described.

[0119] In some configurations, the heat exchanger 100 is formed by providing a core body 103, first shell 110, a second shell 120 and an outer body 130 as herein described. In these configurations, the heat exchanger 100 is configured to extract heat reliably, while improving ease of manufacturing and / or limiting the likelihood of leaks in the system. The arrangement, geometry and materials of the components of the heat exchanger 100 facilitate good heat transfer and therefore a lower driving temperature difference is required. The heat transfer geometry may include features such as the surface area, roughness, turbulence, conductive path length and area) and material conductivity.

[0120] Heat transfer is driven from a hot fluid to the cooling fluid (in some configurations, helium to water / coolant) by a temperature difference. The rate of heat transfer is determined by the temperature difference as well as the specifics of the heat transfer geometry (surface area, roughness, turbulence, conductive path length and area) and material conductivity. The heat exchanger 100 aims to transfer more heat from one fluid to the other with a lower temperature difference to drive it. In some configurations, cooling water is delivered at a specific temperature (e.g. at a maximum of 35 degrees Celsius), this water is to cool the helium (or other working fluid) in the heat exchanger 100.

[0121] The slits 104 may allow the volume of working fluid (fluid to be cooled) within the heat exchanger 100 to be lower while achieving effective heat exchange. As such, the slits 104 may allow for the ratio of cooling fluid to working fluid to be greater. The slits 104 may also increase the surface area of the heat exchanger 100 that is adjacent to the working fluid. When the heat exchanger 100 is used as part of a cryocooler system, the slits 104 can improve the cooling performance of the cryocooler by ensuring the pressure wave generated by the pressure wave generator is efficiently transferred through the heat exchanger 100.

[0122] The components of the heat exchanger 100 are machined / manufactured to provide the desired geometry to provide the desired flow pathways for the fluid being cooled, the liquid for cooling, and to allow heat transfer. This may include one or a combination of the following amongst other features: slits 104 provided to allow fluid flow, a liquid channel 1 15 for the liquid for cooling, and liquid channel inlet 105 and liquid channel outlet 106 for entry and exit of the liquid.

[0123] The components may be machined by a CNC (computer numerical control) machine, lathes and milling machines for example.

[0124] To provide the slits 104 on some of the components of the heat exchanger 100, wirecut EDM (electrical discharge machining) may be used.

[0125] The first shell 1 10 is fixed to the outer surface of the core body 103. Then the second shell 120 is fixed to the outer surface of the first shell 1 10.

[0126] In some configurations, an outer body 130 is provided. The outer body 130 is fixed to the outer surface of the second shell 120.

[0127] The components of the heat exchanger 100 may be fixed / sealed together by welding, brazing, gasket or O-ring seals or other methods known to a person skilled in the art to join the components. In some cryocooling applications, it may be advantageous for the components to be welded or brazed together to reduce the likelihood of leakages under extreme pressures and temperatures.

[0128] The components should be joined together in such a way as to reduce the likelihood of axial leakage (e.g. of the helium gas) between components. The risk of leakage may be reduced by the heat exchanger 100 as there are a limited number of components joined together and therefore fewer points of failure and potential leak pathways. In the event of a leak, helium gas could leak into the cooling water. If there is a leak, over time the working pressure of helium in the cryocooler could reduce - eventually to a point where the cryocooler performance would diminish, potentially to the point of a fault and stop working.

[0129] Further, this design reduces the parts requiring welding, which can reduce associated manufacturing costs, time and allow for a repeatable performance of the heat exchanger.

[0130] As provided above, in some configurations, the heat exchanger 100 is part of a cryocooler assembly.

[0131] In some configurations, the cryocooler assembly is a pulse tube cryocooler 1000 as shown in figure 2. In some configurations the pulse tube cryocooler 1000 has a pulse tube 201 , a regenerator 202, a pressure wave generator, and the heat exchanger 100. The cryocooler 1000 also has inertance tubes, and buffer volumes. In such a configuration it is advantageous for the liquid channel inlet 105 and the liquid channel outlet 106 to be directed radially outwards from the heat exchanger 100 rather than above or below the pressure wave generator of the cryocooler assembly may be located directly below the heat exchanger 100. The same advantage applies to other configurations in which the heat exchanger 100 is part of a cryocooler assembly or other assembly. In other configurations, the cryocooler assembly is a Stirling cryocooler 2000 as shown in figure 3. In these configurations the Stirling cryocooler may have a Stirling piston 301 , a regenerator 302, a pressure wave generator, and the heat exchanger 100.

[0132] It should be appreciated the heat exchanger 100 may be used with a range of different cryocooler assemblies.

[0133] In summary, it should be appreciated, the heat exchanger 100 which includes the above-mentioned features can function to effectively transfer heat to or from a working fluid, while balancing and potentially improving the ease and cost of manufacturing.

[0134] In configurations where there are only a few components required to be welded or otherwise joined together to form the heat exchanger 100, the number of potential leak pathways are reduced compared to other heat exchangers such as compared to shell-and- tube heat exchangers. The reduced number of components associated with the heat exchanger also allows for a more repeatable manufacturing and performance of the heat exchanger. Additionally, the reduced number of components allows for ease of disassembly and reassembly for cleaning and maintenance of the heat exchanger 100. This may extend the lifetime of the heat exchanger 100.

[0135] Further advantages may be provided by the more specific features of the design including having slits 104 provided on both sides of the liquid channel 1 15, on the first shell 1 10 and second shell 120. Efficient heat transfer may be achieved as heat is absorbed on both sides of the liquid channel 115.

[0136] Another feature that may provide advantages over other designs is having the entry and exit (liquid channel inlet 105 and liquid channel outlet 106), at the bottom end 101 of the heat exchanger 100.

[0137] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims.

[0138] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Claims

CLAIMS1 . A heat exchanger for cooling a fluid comprising: a first end and a second end, wherein the heat exchanger comprises a tapered structure such that one end is narrower than the other end and wherein the heat exchanger comprises: a longitudinal axis; a plurality of components forming the heat exchanger comprising: a core body; a first shell surrounding the core body; a second shell surrounding the first shell; an outer body surrounding the second shell; a plurality of slits provided on at least one of the plurality of components forming the heat exchanger, wherein the slits are configured to allow a fluid to pass through for cooling; and a liquid channel provided between the first and second shells, the liquid channel configured to receive a liquid to cool the fluid passing through the heat exchanger.

2. The heat exchanger as claimed in claim 1 wherein the heat exchanger comprises a generally frustoconical shape.

3. The heat exchanger as claimed in any one of the previous claims wherein the plurality of slits extend generally parallel the longitudinal axis of the heat exchanger.

4. The heat exchanger as claimed in any one of the previous claims wherein the plurality of slits are provided on at least one of the walls of the at least one of the plurality of components.

5. The heat exchanger as claimed in any one of the previous claims wherein the plurality of slits are provided on the first shell.

6. The heat exchanger as claimed in any one of the previous claims wherein the plurality of slits are provided on the second shell.

7. The heat exchanger as claimed in any one of the previous claims wherein the plurality of slits are provided on two of the components forming the heat exchanger.

8. The heat exchanger as claimed in any one of the previous claims wherein the plurality of slits are provided on both the first shell and the second shell such that heat from the fluid passing through the slits can transfer to the liquid in the liquid channel via either side of the channel.

9. The heat exchanger as claimed in any one of the previous claims wherein the first shell is an inner shell and the second shell is an outer shell.

10. The heat exchanger as claimed in any one of the previous claims wherein the first shell and the second shell are concentric such that they have a common centre along a longitudinal axis of the heat exchanger.1 1 . The heat exchanger as claimed in any one of the previous claims wherein the first end is a top end of the heat exchanger and the second end is a bottom end of the heat exchanger.

12. The heat exchanger as claimed in any one of the previous claims wherein one or both of the first shell and the second shell comprises a taper towards one end of the heat exchanger.

13. The heat exchanger as claimed in claim 12 wherein one or both of the first shell and the second shell comprises a taper towards the first end of the heat exchanger.

14. The heat exchanger as claimed in any one of the previous claims further comprising a liquid channel inlet configured to allow entry of liquid to flow into the heat exchanger and into the liquid channel, and a liquid channel outlet configured to allow exit of liquid to flow out of the heat exchanger from the liquid channel.

15. The heat exchanger as claimed in claim 14 wherein both the liquid channel inlet and the liquid channel outlet are located at or towards the second end.

16. The heat exchanger as claimed in claim 15 wherein the liquid channel inlet and liquid channel outlet are coaxial and are spaced the same or approximately the same distance from the second end.

17. The heat exchanger as claimed in any one of claims 14 to 16 wherein the liquid channel inlet and the liquid channel outlet are on generally opposite sides of the heat exchanger.

18. The heat exchanger as claimed in any one of the previous claims wherein the liquid channel is a helical flow channel.

19. The heat exchanger as claimed in the previous claim wherein the liquid channel has double heliconical flow path for heat exchange fluid to travel up and down between the inner and outer shells.

20. The heat exchanger as claimed in any one of the previous claims wherein the liquid channel is arranged around at least the core body and the first shell.

21. The heat exchanger as claimed in any one of the previous claims further comprising a third shell surrounding the second shell.

22. The heat exchanger as claimed in claim 21 further comprising a second liquid channel located between the third shell and the outer body.

23. The heat exchanger as claimed in any one of the previous claims wherein the core body comprises a hollow interior.

24. The heat exchanger as claimed in any one of the previous claims wherein one or more of the following are directly adjacent and joined together: a) the core body and first shell; b) the first shell and the second shell; andc) the second shell and the outer body.

25. The heat exchanger as claimed in claim 24 wherein a weld, braze, gasket or O-ring seals the components that are directly adjacent together.

26. The heat exchanger as claimed in any one of the previous claims wherein the heat exchanger is formed from aluminium.

27. The heat exchanger as claimed in any one of the previous claims wherein the heat exchanger is an aftercooler.

28. The heat exchanger as claimed in any one of the previous claims wherein the slits are configured to receive is one or a combination of helium gas, neon gas, argon gas, krypton gas, hydrogen gas, or nitrogen gas.

29. A pulse tube cryocooler comprising: a regenerator; a pulse tube; a compressor; and a heat exchanger as claimed in any one of the previous claims;30. A Stirling cryocooler comprising: a regenerator; a heat exchanger as claimed in any one of claims 1 to 28; and a Stirling piston configured to be at least partially received within the hollow interior of the core body.31 . A method of forming a heat exchanger comprising: forming a plurality of components comprising a core body, a first shell, a second shell and an outer body as claimed in any one of claims 1 to 28; forming slits on at least one of the plurality of components of the heat exchanger; andassembling and joining the plurality of components together to form the heat exchanger.

32. The method as claimed in the previous claim wherein wire EDM is used to form the slits.

33. The method as claimed in any one of claims 31 or 32 wherein the plurality of components of the heat exchanger are joined together by welding or brazing.

34. A heat exchanger for cooling a fluid comprising: a plurality of components forming the heat exchanger comprising: a first shell; a second shell; a liquid channel provided between the first and second shells, the liquid channel configured to receive a liquid to cool a fluid passing through the heat exchanger; and a plurality of slits are provided on at least the first shell and second shell, wherein the slits are configured to allow the fluid to pass through for cooling such that heat from the fluid passing through the slits can transfer to the liquid in the liquid channel via either side of the channel.

35. The heat exchanger as claimed in claim 34 wherein the heat exchanger comprises a first end and a second end, the heat exchanger comprises a tapered structure such that one end is narrower than the other end and wherein the heat exchanger comprises a longitudinal axis.

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