Cooling system and method performed by the cooling system
The cooling system addresses the challenge of high heat density in compact electronics by using a magnetohydrodynamic pump and magnetic refrigerator to efficiently manage heat through a series of sections, ensuring effective cooling and preventing component degradation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- BRITISH TELECOM PLC
- Filing Date
- 2025-11-14
- Publication Date
- 2026-05-21
AI Technical Summary
There is a need for compact and efficient cooling systems that manage high heat density in spatially restricted environments, particularly for high-power electronics like GaN PAs in 5G communication systems, to prevent heat degradation and maintain a low profile.
A cooling system utilizing a magnetohydrodynamic pump and magnetic refrigerator with a coolant circuit, incorporating ferromagnetic particles and alternating current electromagnets, to efficiently transfer and cool heat through a series of thermally insulated and non-insulated sections, leveraging the magnetocaloric effect for temperature regulation.
The system provides effective heat management, preventing component degradation by maintaining low profile and weight, with reduced mechanical vibration and power consumption, achieving cooling below ambient temperature.
Smart Images
Figure EP2025083063_21052026_PF_FP_ABST
Abstract
Description
[0001] A36117
[0002] - 1 - COOLING SYSTEM
[0003] FIELD OF THE INVENTION
[0004] The present invention relates to a cooling system for the thermal management of a component.
[0005] BACKGROUND
[0006] There is a desire to reduce the size and cost of high power-density electronics. For example, printed circuit board antennae or antenna-in-package technologies used in 5G communication systems tend to be compact to avoid dielectric and RF losses. It is desirable to provide compact cooling systems that do not add substantial volume to the overall component.
[0007] There is also a desire for efficient and compact heat transfer techniques for devices, particularly those in spatially restricted environments. For example, high-density data centres comprise central processing unit (CPU) clusters in server racks close to each other. Heat transfer and cooling systems are used to manage the substantial heat generated by the high computing power.
[0008] SUMMARY OF INVENTION
[0009] In an aspect, there is provided a cooling system for thermal management of a component. The cooling system comprises: a coolant circuit comprising a plurality of sections; a magnetohydrodynamic pump configured to pump a coolant around the coolant circuit by applying a first electric field and a first magnetic field through a first section of the plurality of sections, the first magnetic field being applied by a first electromagnet of the magnetohydrodynamic pump, the first electromagnet being an alternating current electromagnet, the coolant being an electrically conducting fluid comprising ferromagnetic particles; a substrate comprising a second section of the plurality of sections, the second section being for fluidic communication of the coolant and for positioning adjacent the component; and a magnetic A36117
[0010] - 2 -refrigerator configured to, after heat is absorbed by the coolant in the second section of the coolant circuit, cool the coolant by a magnetocaloric effect.
[0011] The substrate may be a diamond heat spreader.
[0012] The second section may comprise a spiral channel or a pair of counterpropagating channels.
[0013] The cooling system may further comprise: a pair of electrodes configured to apply the electric field through the first section of the plurality of sections of the coolant circuit; and a controller configured to control a relative phase of an alternating current applied to the first electromagnet and an alternating current applied to the pair of electrodes.
[0014] The plurality of sections of the coolant circuit may comprise a third section and a fourth section, the third section being more thermally insulated relative to the fourth section. The magnetohydrodynamic pump may be configured to pump the coolant from the first section to the second section, from the second section to the third section, from the third section to the fourth section, and from the fourth section to the first section.
[0015] The magnetic refrigerator may be configured to cool the coolant by: applying a second magnetic field to the coolant in the third section whereby to heat the coolant. The second magnetic field may be greater than any magnetic field experienced by the coolant in the second section of the coolant circuit. The coolant may be heated as a result of the magnetocaloric effect and the relatively high thermal insulation of the third section. The magnetic refrigerator may be further configured to cool the coolant by: applying the second magnetic field or a third magnetic field to the coolant in the fourth section of the coolant circuit, wherein heat dissipates from the coolant in the fourth section as a result of the relatively low thermal insulation of the fourth section. The third magnetic field may be greater than any magnetic field experienced by the coolant in the second section of the coolant circuit.
[0016] The coolant that exits the fourth section may experience a magnetic field that is less than the second magnetic field or the third magnetic field, thereby further cooling as a result of the magnetocaloric effect. A thermal insulation of A36117
[0017] - 3 -the coolant as it is pumped from the fourth section to the first section may be greater than the thermal insulation of the fourth section.
[0018] The second magnetic field may be generated by a second electromagnet. The third magnetic field may be generated by a third electromagnet.
[0019] The cooling system may further comprise a further substrate. The first electromagnet may be integrated with the further substrate. The first electromagnet may be arranged as a coil integrated with the further substrate. The first section may comprise a first channel in an upper surface of the further substrate. The coil may be disposed opposite the first channel. The second electromagnet may be arranged as a coil integrated with the further substrate. The third section may comprise a second channel in an upper surface of the further substrate. The coil may be disposed opposite the second channel. The third electromagnet may be arranged as a coil integrated with the further substrate. The further substrate may be a substrate of a printed circuit board. The printed circuit board may be for receiving the component.
[0020] In a further aspect, there is provided a method performed by the cooling system of any preceding aspect. The method comprises: pumping, via the magnetohydrodynamic pump, coolant around the coolant circuit; absorbing, by the coolant in the second section of the plurality of sections, heat from the substrate; and cooling, by the magnetic refrigerator, the coolant after it is pumped through the second section.
[0021] BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 is a schematic illustration (not to scale) showing a cooling system for thermal management of a component;
[0023] Figure 2 is a schematic illustration (not to scale) showing a portion of the cooling system including a magnetohydrodynamic pump and a first section of a coolant circuit; A36117
[0024] -4 - Figure 3 is a schematic illustration (not to scale) showing a further portion of the cooling system including a second section of the coolant circuit and a substrate with the component mounted thereon;
[0025] Figure 4 is a schematic illustration (not to scale) showing a further portion of the cooling system including a third section of the coolant circuit and a first part of a magnetic refrigerator;
[0026] Figure 5 is a schematic illustration (not to scale) showing a further portion of the cooling system including a fourth section of the coolant circuit and a second part of the magnetic refrigerator; and
[0027] Figure 6 is a process flow chart showing certain steps of a method performed by the cooling system.
[0028] DETAILED DESCRIPTION
[0029] In power electronics, the demand to reduce size at increased power requires increasingly compact and efficient heat transfer techniques. For example, high-capacity mobile communications at frequencies of 26GHz or higher can be performed with Multiple-Input Multiple-Output (MIMO) beamforming using patch antenna arrays. Each antenna element of the antenna array tends to require an RF chain including a Monolithic Microwave Integrated Circuit (MMIC) Power Amplifier (PA). These antenna arrays can be mounted on the surface of, for example, aircraft, satellites, cars, or handheld devices. Thus, it is desirable that a structure including the patch antenna array, the RF chain, and any associated cooling system(s) is low profile and light weight.
[0030] In the frequency range of 26GHz or higher, Gallium Nitride (GaN) PAs are typically used because of their greater efficiency compared to conventional PAs, such as Gallium Arsenide (GaAs) PAs. However, GaN PAs tend to produce a large amount of heat in a small area around a transistor junction. Thus, near-junction cooling is desirable to avoid degradation of the GaN PAs. Furthermore, as described above, the patch antenna array, the RF chain, and any associated cooling systems are preferably kept compact and low-profile. Without sufficient cooling, the heat from the GaN PA may spread and cause the degradation of other components. A36117
[0031] - 5 - What will now be described with reference to Figures 1 to 5 is a cooling system that tends to address the aforementioned problems.
[0032] Figure 1 is a schematic illustration (not to scale) of an embodiment of a cooling system 100 for thermal management of a component 102.
[0033] The component 102 may be a power electronics device. For example, the component 102 may be a GaN PA for use in an RF chain.
[0034] The cooling system 100 comprises a coolant circuit 104, a magnetohydrodynamic (MHD) pump 114, a substrate 126, and a magnetic refrigerator 109.
[0035] The coolant circuit 104 comprises a plurality of sections. In particular, in this embodiment, the coolant circuit 104 comprises a first section 106, a second section 108, a third section 110, and a fourth section 112.
[0036] The coolant circuit 104 contains a coolant which travels through the coolant circuit 104 in use. The coolant is an electrically conductive fluid comprising ferromagnetic particles (i.e., an electrically conductive ferrofluid). A ferrofluid may be a stable colloidal suspension of nanometre-sized ferromagnetic particles in a carrier fluid. These particles are usually ferrites or alloys of iron, nickel and cobalt. The particles may have a diameter of less than or equal to 15nm. In a non-limiting example, the ferromagnetic particles may be gadolinium nanoparticles, and the electrically conductive fluid may be a gallium alloy liquid metal. More specifically, the electrically conductive fluid may be an alloy of gallium, indium, and tin, and the ferromagnetic particles may be a Gds(Si,Ge)4 alloy.
[0037] The MHD pump 114 is configured to pump the coolant around the coolant circuit 104. The direction of flow of the coolant through the coolant circuit 104 is depicted in Figure 1 by arrows 116, 118, 120, 122. More specifically, in this embodiment, the coolant is pumped from the first section 106 to the second section 108 as depicted by a first arrow 116, from the second section 108 to the third section 110 as depicted by a second arrow 118, from the third section 110 to the fourth section 112 as depicted by a third arrow 120, and from the fourth section 112 to the first section 106 as depicted by a fourth arrow 122. The MHD pump 114 may be considered to form a part of a magnetic system of the cooling system 100. The MHD pump 114 pumps the coolant by generating a first electric field and a first magnetic field. The MHD pump 114 applies the first electric field and the first magnetic field through the first section 106 of the coolant circuit 104. The MHD pump 114 comprises a first magnet 124 configured to generate the first magnetic field. In this embodiment, the first magnet 124 is an electromagnet, and preferably an alternating current (AC) electromagnet. The first section 106 and the MHD pump 114 are described in more detail later below with reference to Figure 2.
[0038] The substrate 126 comprises the second section 108. The second section 108 of the cooling system is, in this embodiment, a conduit through the substrate 126. The second section 108, i.e. the conduit, is for fluidic communication of the coolant through the substrate 126. The substrate 126 is configured to be positioned adjacent to (e.g., in contact with) the component 102. For example, the substrate 126 may be a heat spreader arranged to contact (e.g., receive) the component 102. In this embodiment, as described in more detail later below, in use, the coolant absorbs heat from the body of the substrate 126 as it travels through the second section 108, whereby to provide cooling to the component 102. The second section 108 is described in more detail later below with reference to Figure 3.
[0039] The magnetic refrigerator 109 is configured to cool the coolant as the coolant travels through the third section 110 and fourth section 112, and out of the fourth section 112. The magnetic refrigerator 109 is configured to cool the coolant by the magnetocaloric effect. Preferably, the magnetic refrigerator 109 cools the coolant to a temperature that is less than an ambient temperature.
[0040] In this embodiment, the third section 110 is more thermally insulated than the fourth section 112. For example, the third section 110 may be a thermally insulated channel for flow of the coolant, whereas the fourth section 112 may be coupled to a heat exchanger arranged to absorb heat from the coolant in the fourth section 112.
[0041] The magnetic refrigerator 109, the third section 110, and the fourth section 112 will be described in more detail later below with reference to Figure 4 and Figure 5. - 7 - Figure 2 is a schematic illustration (not to scale) of the first section 106 and the pump 114.
[0042] In this embodiment, the first section 106 is integrated with a printed circuit board (PCB). More specifically, the first section 106 is integrated with a PCB substrate 202. More specifically, the first section 106 is a first channel 208 formed in an upper surface 204 of the PCB substrate 202 along which the coolant may flow. The first channel 208 may be a microchannel (i.e., a channel with a diameter less than 1mm).
[0043] In this embodiment, as depicted in Figure 2, the first section 106 is the first channel 208 formed in the upper surface 204 of the PCB substrate 202. However, in other embodiments, some or all of the first channel 208 may be wholly inside the PCB substrate 202 (i.e., the first section 106 may be an enclosed passage or conduit formed through the PCB substrate 202).
[0044] In this embodiment, the MHD pump 114 comprises the first magnet 124, a pair of electrodes 212, a signal generator 214, a first amplifier 216, a second amplifier 217, and a phase controller 218.
[0045] The pair of electrodes 212 are disposed on the upper surface 204 of the PCB substrate 202. The electrodes 212 are positioned opposing one another at opposite side of the first channel 208, transversely across the width of the first channel 208. The electrodes 212 are configured to generate the first electric field between the electrodes 212, across the first channel 208.
[0046] The signal generator 214 and the first amplifier 216 are configured to respectively generate and amplify an AC signal applied to the electrodes 212, whereby to generate the first electric field.
[0047] The first magnet 124 is configured to generate the first magnetic field through the first channel 208. In this embodiment, the first magnet 124 is a planar coil that is disposed on a lower surface 206 of the PCB substrate 202, opposite to the upper surface 204. The planar coil may be formed of copper traces printed on the lower surface 206. The planar coil may define a spiral shape. The planar coil may be positioned directly under the first channel 208. Advantageously, positioning the planar coil directly under the first channel 208 tends to apply a homogeneous magnetic field across the first channel 208. - 8 - The signal generator 214 and the second amplifier 217 are configured to respectively generate and amplify an AC signal applied to the first magnet 124, whereby to generate the first magnetic field.
[0048] The phase controller 218 is configured to control a relative phase of the alternating current applied to the first magnet 124 compared to the alternating current applied to the pair of electrodes 212.
[0049] In this embodiment, as a result of the first magnetic field and the electric field, a Lorentz force is applied to the coolant in the first section 106, thereby pumping the coolant through the first section 106, and thus around the coolant circuit 104. The direction of flow of the coolant through the first section 106 (i.e., along the first channel 208) is depicted in Figure 2 by a fifth arrow 210.
[0050] Advantageously, the phase controller 218 tends to prevent a drift in relative phase between the signal received by the first magnet 124 and the signal received by the pair of electrodes 212.
[0051] The phase controller 218 may be coupled to a temperature sensor (not shown) for detecting a temperature of the component 102. Alternatively, or in addition, the phase controller 218 may be configured to receive a signal indicative of whether the component 102 is in use (i.e., if the component 102 is in a state in which it generates heat). The phase controller 218 may control a speed of coolant flow through the coolant circuit 104 by controlling the relative phase between the signal received by the first magnet 124 and the signal received by the pair of electrodes 212.
[0052] GaN PAs in antenna arrays are generally not in constant use, and instead operate based on a user demand, so heat output varies accordingly. Large temperature swings in the component may cause mechanical stress and component failure. Advantageously, the phase controller 218 may provide a means to control the speed of coolant flow through the coolant circuit 104 based on a temperature of the component 102 or based on whether the component 102 is in use.
[0053] Advantageously, the MHD pump 114 being an AC MHD pump tends to prevent electrolysis from occurring in the coolant. Furthermore, the AC MHD pump 114 tends to prevent the ferromagnetic particles being separated based A36117
[0054] - 9 -on size and / or composition (i.e., the AC MHD pump 114 tends to avoid electrophoresis in the ferrofluid). Yet further, the MHD pump 114 being an AC MHD pump tends to prevent the coolant from heating due to the magnetocaloric effect. In this respect, it is preferable that the AC signal is of sufficiently high frequency to avoid electrolysis, electrophoresis, and / or magnetocaloric heating.
[0055] Advantageously, the MHD pump 114 being integrated with the PCB substrate 202 tends to provide a PCB-based cooling system 100 where the pumping is done on the PCB itself. Furthermore, the first magnet 124 (which may be a substantially planar coil) may be directly fabricated onto the lower surface 206 of the PCB. Thus, a compact cooling system 100 is provided.
[0056] Advantageously, the MHD pump 114 has no moving parts. Thus, the cooling system 100 tends to be quiet with little mechanical vibration compared to conventional pumps, which may be used in compressor-based cooling systems. Furthermore, the MHD pump 114 tends to be more power-efficient than, for example, a compressor-based cooling system and less susceptible to damage resulting from moving parts.
[0057] Figure 3 is a schematic illustration (not to scale) of a cross-section of the substrate 126 with the component 102 disposed thereon.
[0058] The substrate 126 may be in direct contact with the component 102. The substrate 126 may be a heat spreader. The substrate 126 may be a diamond heat spreader. Advantageously, diamond heat spreaders tend to have a very high thermal conductivity. Thus, diamond heat spreaders tend to spread heat more evenly throughout the substrate 126 compared to conventional heat spreaders such as copper heat spreaders.
[0059] The substrate 126 comprises the second section 108, which may take the form of one or more conduits 302 through the substrate 126. The coolant flows through the one or more conduits 302, thereby absorbing heat from the body of the substrate 126. The substrate 126 may comprise a coolant inlet 304 and a coolant outlet 306.
[0060] The component 102 may be a GaN PA. As described above, a GaN PA may have a high heat flux at the transistor junction. Thus, there may be a small area of the substrate 126 proximate to the transistor junction which may be A36117
[0061] - 10 -hotter than the rest of the substrate 126. The inlet 304 may be positioned at or under the hotter region of the substrate 126 and spiral outwards, thereby absorbing heat from progressively less hot parts of the component 102 as it is pumped through the channel 302. Alternatively, the inlet 304 may be positioned at one end of the substrate 126, and the outlet may be positioned at an opposite end of the substrate 126. Alternatively, the substrate may include two inlets, each configured to receive a respective portion of the coolant; the coolant may then propagate through a pair of counter-propagating channels within the substrate 126. The counter-propagating channels may recombine at a common coolant outlet.
[0062] Figure 4 is a schematic illustration (not to scale) of the third section 110 of the coolant circuit 104 and a first part 109A of the magnetic refrigerator 109 acting thereon.
[0063] In this embodiment, the third section 110 is integrated with a printed circuit board (PCB). More specifically, the third section 110 is integrated with the PCB substrate 202. More specifically, the third section 110 is a second channel 402 formed in the upper surface 204 of the PCB substrate 202 along which the coolant may flow. The direction of flow of the coolant is depicted in Figure 4 by a sixth arrow 404. The third section 110 may be a microchannel (i.e., a channel with a diameter less than 1mm).
[0064] In this embodiment, as depicted in Figure 4, the third section 110 is the second channel 402 formed in the upper surface 204 of the PCB substrate 202. However, in other embodiments, some or all of the third section 110 may be wholly inside the PCB substrate 202 (i.e., the third section 110 may be an enclosed passage or conduit formed through the PCB substrate 202).
[0065] In this embodiment, the magnetic refrigerator 109 comprises a second magnet 406. The second magnet 406 is an electromagnet, preferably a direct current (DC) electromagnet. The second magnet 406 is configured to apply a second magnetic field to the coolant in the third section 110. The strength of the second magnetic field is preferably greater than that of a magnetic field experienced by the coolant in the second section 108. The second magnet 406 may be positioned on the PCB substrate 202 directly opposite (e.g., under) the second channel 402. In this embodiment, the second magnet 406 is a planar - 11 -coil disposed on the lower surface 206 of the PCB substrate 202. The planar coil may define a spiral shape. The planar coil may be formed from copper traces printed on the lower surface 206 of the PCB substrate 202.
[0066] Advantageously, positioning the second magnet 406 opposite the second channel 402 tends to allow for a substantially homogeneous magnetic field to be applied to the coolant throughout the second channel 402.
[0067] In this embodiment, in use, the coolant enters the third section 110 after it has passed through the second section 108 whereat heat is absorbed from the substrate 126. Upon entering the third section 110, the ferrofluid coolant experiences the second magnetic field applied thereto by the second magnet 406. Thus, the ferrofluid is further heated by the magnetocaloric effect.
[0068] Figure 5 is a schematic illustration (not to scale) of the fourth section 112 of the coolant circuit 104 and a second part 109B of the magnetic refrigerator 109 acting thereon.
[0069] In this embodiment, the fourth section 112 is integrated with a further substrate 502, which may be heat spreader or heat exchanger. The further substrate 502 may be a diamond heat spreader. The further substrate 502 comprises the fourth section 112, which may take the form of one or more conduits 504 through the further substrate 502. The coolant flows through the one or more conduits 504, thereby transferring heat to the relatively cooler body of the further substrate 502. Thus, the coolant is cooled as it flows through the fourth section 112.
[0070] In this embodiment, the magnetic refrigerator 109 comprises a third magnet 506. The third magnet 506 is an electromagnet, preferably a DC electromagnet. The third magnet 506 is configured to apply a third magnetic field to the coolant in the fourth section 112. The strength of the third magnetic field is preferably greater than that of a magnetic field experienced by the coolant in the second section 108. The strength of the third magnetic field may be the same as that of the second magnetic field. For example, the second and third magnets 406, 506 may be substantially identical and supplied with substantially identical electrical currents. The third magnet 506 may be positioned on the further substrate 502 proximate to the one or more conduits 504. In this embodiment, the third magnet 506 is a planar coil disposed on the lower surface of the further substrate 502. The planar coil may define a spiral shape. The planar coil may be formed from copper traces printed on the lower surface of the further substrate 502.
[0071] The one or more channels 504 may be relatively less thermally insulated than the channel 402 of the third section 110. The further substrate 502 is configured to absorb and dissipate heat from the coolant flowing therethrough. For example, the further substrate 502 is configured to cool the coolant to an ambient temperature.
[0072] In this embodiment, in use, after the coolant has passed through the fourth section 112 (whereat the coolant is cooled), the coolant exits the fourth section 112 and may return to the first section 116. On exiting the fourth section 112, the third magnetic field that was applied in the fourth section 112 is removed, or at least is reduced, from the coolant. This reduction or removal of the magnetic field from the coolant causes magnetic domains in the coolant to return to a random state, causing the coolant to cool down further. In other words, the coolant is further cooled as a result of the magnetocaloric effect.
[0073] Advantageously, in this way, the coolant may be cooled to a temperature below an ambient temperature of the system 100. Thus, an efficient cooling system 100 is provided.
[0074] In some embodiments, the further substrate 502 may be positioned on top of a portion of the PCB. The third magnet 506 may be integrated with the portion of the PCB. The further substrate 502 may be any suitable structure with high thermal conductivity. For example, the further substrate 502 may be a copper element. The further substrate 502 may comprise one or more fins (not shown). Alternatively, the further substrate 502 may be any other thermally conductive plate. The further substrate 502 may operate in conjunction with one or more external heat dissipating systems, for example a fan.
[0075] The cooling system 100 may comprise a further controller (not shown) configured to control the current supplied to the second magnet 406 and / or the - 13 -third magnet 506 based on one or more of: the temperature of the component 102, whether the component 102 is in use, and the temperature of the coolant. In some embodiments, the further controller and the phase controller 218 may be the same controller.
[0076] Advantageously, the fourth section 112 having a third magnet 506 being separate and independent of the second magnet 406 tends to facilitate assembly of a cooling system where the second magnet 406 is integrated with the PCB, and the third magnet 506 is integrated with the further substrate 502.
[0077] Advantageously, partitioning the magnetic refrigerator 109 into the third section 110 and the fourth section 112 tends to prevent or reduce thermal conduction between the third section 110 and the second section 108. Specifically, the insulated channel 402 of the third section 110 tends to prevent heat being conducted back to the substrate 126 in which the second section 108 is situated. The third section 110 provides a means to transport hot coolant away from the substrate 126 and the component 102 in an insulated channel 402 before the heat is dissipated in the fourth section 112.
[0078] Figure 6 is a process flow chart showing certain steps of an embodiment of a method performed by the cooling system 100.
[0079] At step s602 the MHD pump 114 pumps the coolant around the coolant circuit 104. In this embodiment, the coolant is pumped through the first section 106, from the first section 106 to the second section 108, through the second section 108, from the second section 108 to third section 110, through the third section 110, from the third section to the fourth section 112, through the fourth section 112, and from the fourth section 112 back to the first section 106.
[0080] At step s604, the coolant passing through the second section 108 absorbs heat from the substrate 126. Thus, the substrate 126 is cooled. The cooled substrate 126 cools the component 102.
[0081] At step s606 the magnetic refrigerator 109 cools the coolant received from the second section 108 and that passes through the third and fourth sections 110, 112.
[0082] In particular, in this embodiment, the coolant flowing through the third section 110 is heated by application of the second magnetic field, by the - 14 -magnetocaloric effect. As the heated coolant subsequently passes though the fourth section 112, heat from the heated coolant is dissipated by the further substrate 502 (which may be a heat exchanger or heat spreader) while the coolant is still placed in a strong magnetic field (i.e., the third magnetic field, which may be the same as or a similar to the second magnetic field). The cooled coolant then exits the magnetic refrigerator 109 and thus the relatively strong third magnetic field, causing further cooling of the coolant by the magnetocaloric effect.
[0083] In the above embodiments, the cooling system 100 is described with respect to cooling a GaN PA. In other embodiments, however, the cooling system may cool a different component. For example, the cooling system 100 may cool a central processing unit (CPU) or a graphics processing unit (GPU). Employing the cooling system 100 with a CPU or GPU may be particularly advantageous in high-density data centres such as cloud servers. In such data centres, CPU and / or GPU clusters tend to be located deep within the data centre. Thus, a PCB-based or otherwise compact cooling system may facilitate the transfer of heat to external heatsinks. For example, in such embodiments, the substrate 126 may be a cool plate in contact with the CPU / GPU, or the substrate may be an integrated heat spreader of the CPU. The cooling system may pump coolant, after it has absorbed heat from the substrate, to a heat exchanger in an external environment where the heat exchanger dissipates heat to the environment.
[0084] In the above embodiments, the coolant is pumped from the first section 106 to the second section 108, from the second section 108 to the third section 110, from the third section 110 to the fourth section 112, and from the fourth section 112 to the first section 106. In other embodiments, however, coolant is pumped from the first section 106 to the third section 110, from the third section 110 to the fourth section 112, from the fourth section 112 to the second section 108, and from the second section 108 to the first section 106.
[0085] In the above embodiments, the cooling system 100 is at least partially integrated with a PCB. In other embodiments, however, the cooling system 100 is not integrated with a PCB. In such embodiments, the coolant may be pumped A36117
[0086] - 15 -to and from the substrate 126 via channels or conduits in a different structure separate to the PCB.
[0087] In the above embodiments, the substrate 126 is a diamond heat spreader. In other embodiments, however, the substrate 126 may be a silicon carbide heat spreader, a copper heat spreader, or any other heat spreader suitable for conducting heat from the component 102.
[0088] In the above embodiments, the MHD pump 114 is integrated with the PCB. In other embodiments, however, the MHD pump 114 is not integrated with the PCB. For example, the MHD pump may be external to the PCB. Specifically, the pair of electrodes 212 and the first magnet 124 may be external to the PCB.
[0089] In the above embodiments, the first section 106 is integrated with the PCB. In other embodiments, however, the first section 106 is not integrated with the PCB. For example, the first section 106 may comprise one or more channels or conduits external to the PCB.
[0090] In the above embodiments, the third section 106 is integrated with the PCB. In other embodiments, however, the third section 106 is not integrated with the PCB. For example, the third section 106 may comprise one or more channels or conduits external to the PCB.
[0091] In the above embodiments, the first section 106 and the third section 110 are integrated with a common PCB substrate. In other embodiments, however, the first section 106 and the third section 110 are not integrated with a common PCB substrate. For example, the first section 106 may be integrated with a first substrate of the PCB, and the third section 110 may be integrated with a second substrate of the PCB.
[0092] In the above embodiments, the magnetic refrigerator 109 cools the coolant as it travels through the third section 110 and the fourth section 112. In other embodiments, however, the magnetic refrigerator 109 may cool the coolant travelling through a single section of the coolant circuit. In such an embodiment, the single section may be a conduit through a heat exchanger, wherein the heat exchanger is sufficiently large such that the ferrofluid may be further heated by the magnetocaloric effect and still be cooled to a desired A36117
[0093] - 16 -temperature (e.g. a near-ambient temperature) before exiting the heat exchanger.
[0094] In the above embodiments, the magnetic refrigerator 109 comprises a second magnet 406 and a third magnet 506. In other embodiments, however, the magnetic refrigerator 109 comprises a different number of magnets other than two, e.g. only a single magnet configured to apply a magnetic field to the coolant in the third section 110 and the fourth section 112.
[0095] In the above embodiments, the second magnet 406 is an electromagnet. In other embodiments, however, the second magnet is a different type of magnet other than an electromagnet.
[0096] In the above embodiments, the third magnet 506 is an electromagnet. In other embodiments, however, the third magnet is a different type of magnet other than an electromagnet.
Claims
A36117- 17 -CLAIMS1. A cooling system for thermal management of a component, the cooling system comprising:a coolant circuit comprising a plurality of sections;a magnetohydrodynamic pump configured to pump a coolant around the coolant circuit by applying a first electric field and a first magnetic field through a first section of the plurality of sections, the first magnetic field being applied by a first electromagnet of the magnetohydrodynamic pump, the first electromagnet being an alternating current electromagnet, the coolant being an electrically conducting fluid comprising ferromagnetic particles;a substrate comprising a second section of the plurality of sections, the second section being for fluidic communication of the coolant and for positioning adjacent the component; anda magnetic refrigerator configured to, after heat is absorbed by the coolant in the second section of the coolant circuit, cool the coolant by a magnetocaloric effect.
2. The cooling system of claim 1 , wherein the substrate is a diamond heat spreader.
3. The cooling system of any preceding claim, wherein the second section comprises a spiral channel or a pair of counter-propagating channels.
4. The cooling system of any preceding claim, further comprising:a pair of electrodes configured to apply the electric field through the first section of the plurality of sections of the coolant circuit; anda controller configured to control a relative phase of an alternating current applied to the first electromagnet and an alternating current applied to the pair of electrodes.A36117- 18 - 5. The cooling system of any preceding claim, wherein:the plurality of sections of the coolant circuit comprises a third section and a fourth section, the third section being more thermally insulated relative to the fourth section;the magnetohydrodynamic pump is configured to pump the coolant from the first section to the second section, from the second section to the third section, from the third section to the fourth section, and from the fourth section to the first section; andthe magnetic refrigerator is configured to cool the coolant by: applying a second magnetic field to the coolant in the third section whereby to heat the coolant; andapplying the second magnetic field or a third magnetic field to the coolant in the fourth section of the coolant circuit, wherein heat dissipates from the coolant in the fourth section as a result of the relatively low thermal insulation of the fourth section; whereinthe coolant that exits the fourth section experiences a magnetic field that is less than the second magnetic field or the third magnetic field, thereby further cooling as a result of the magnetocaloric effect.
6. The cooling system of claim 5, wherein the second magnetic field is generated by a second electromagnet.
7. The cooling system of claim 5 or 6, wherein the third magnetic field is generated by a third electromagnet.
8. The cooling system of any preceding claim further comprising a further substrate, wherein the first electromagnet is integrated with the further substrate.A36117- 19 - 9. The cooling system of claim 8, wherein the first electromagnet is arranged as a coil integrated with the further substrate.
10. The cooling system of claim 9, wherein the first section comprises a first channel in an upper surface of the further substrate, and wherein the coil is disposed opposite the first channel.
11. The cooling system of any of claims 8 to 10 when dependent on claim 6, wherein the second electromagnet is arranged as a coil integrated with the further substrate.
12. The cooling system of claim 11 , wherein the third section comprises a second channel in an upper surface of the further substrate, and wherein the coil is disposed opposite the second channel.
13. The cooling system of any of claims 8 to 12 when dependent on claim 7, wherein the third electromagnet is arranged as a coil integrated with the further substrate.
14. The cooling system of any of claims 8 to 13, wherein the further substrate is a substrate of a printed circuit board, and wherein the printed circuit board is for receiving the component.
15. A method performed by the cooling system of any of claims 1 to 14, the method comprising:pumping, via the magnetohydrodynamic pump, coolant around the coolant circuit;absorbing, by the coolant in the second section of the plurality of sections, heat from the substrate; andA36117- 20 - cooling, by the magnetic refrigerator, the coolant after it is pumped through the second section.