GB2608989A

GB2608989A - Variable cooling system

Info

Publication number: GB2608989A
Application number: GB2109735.7A
Authority: GB
Inventors: Deodhar Rajesh; Shi Juntao
Original assignee: IMRA Europe SAS
Current assignee: IMRA Europe SAS
Priority date: 2021-07-06
Filing date: 2021-07-06
Publication date: 2023-01-25
Anticipated expiration: 2041-07-06
Also published as: GB2608989B; GB202109735D0

Abstract

A cooling system 300 comprises a channel 310 comprising a ferrofluid, a variable permanent magnet 330 configured to exert a magnetic field on part of the ferrofluid within the channel to cause the ferrofluid to flow within the channel, and an electromagnet 335 configured to exert a magnetic field pulse on the variable permanent magnet to alter its magnetisation and cause a change in the rate of flow of the ferrofluid within the channel. The electromagnet preferably comprises an electrical coil which may be coiled about the variable permanent magnet. A heat exchanger 340 may be arranged proximate to the channel to transfer heat away from the ferrofluid. The cooling system may also comprise temperature sensors 350a, 350b and a controller. The variable cooling system provides adjustable temperature management for a heat source 320 without impacting efficiency. A method and a computer-readable medium comprising instructions to carry out the steps of the cooling system are also provided.

Description

Variable Cooling System

Field of the Invention

The invention generally relates to cooling systems, cooling methods and computer-readable media. More specifically, a ferrofluid is able to circulate within a channel at a variable rate based on the

strength of an external magnetic field.

Background

Temperature management in mechanical and electrical systems has long been an important area of research. Excessive heating of components can lead to performance degradation and eventually component failure, and as such, managing the temperature in mechanical and electrical systems is imperative in order to prolong component life.

One approach for temperature management involves water cooling, whereby water is pumped along a channel in the vicinity of the component requiring cooling. Heat is transferred from the component to the water, and the heated water is transported away from the component due to the pump.

More recently, cooling systems using a ferrofluid in place of water have been employed in a similar manner. The ferrofluid is located within the channel and a permanent magnet applies a magnetic field to the ferrofluid. Heat is transferred from a component to the ferrofluid and the combination of the heating of the ferrofluid and the magnetic field applied by the permanent magnet creates a Kelvin body force within the ferrofluid which causes the ferrofluid to flow within the channel, thereby transporting the heated ferrofluid away from the component. Unlike in water-based systems, ferrofluid-based systems do not require a traditional pump in order for the ferrofluid to circulate. Instead, the rate of flow of the ferrofluid within the channel is dependent on the strength of the external magnetic field exerted on the ferrofluid by the permanent magnet.

One disadvantage of such a system is that the rate of flow of the ferrofluid within the channel cannot be altered, as the strength of the external magnetic field is fixed. Accordingly, alternative systems where the permanent magnet is replaced by a solenoid have been proposed. By varying the electrical current passing through the solenoid, the strength of the external magnetic field can be altered, thereby allowing the rate of flow of the ferrofluid to be altered. However, as the solenoid requires an electrical current in order to generate a magnetic field, an electrical current must be continuously supplied to the solenoid in order for the ferrofluid to flow within the channel. This not only increases the energy usage for the cooling system, but the Joule heating of the solenoid when in use effectively negates any efficiency advantages that a ferrofluid-based cooling system provide.

The present inventors have identified an improved approach for ferrofluid-based cooling which allows for variable flow rates without appreciably decreasing overall efficiency.

Summary of the Invention

Aspects of the invention are set out in the accompanying claims.

According to a first aspect there is provided a cooling system comprising: a channel comprising a ferrofluid; and a variable permanent magnet, wherein the variable permanent magnet is a permanent magnet with variable magnetisation, wherein the variable permanent magnet is configured to exert a magnetic field on at least a portion of the ferrofluid within the channel to cause the ferrofluid to flow within the channel, wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet The cooling system of the first aspect further comprises an electromagnet configured to exert a magnetic field pulse on the variable permanent magnet to alter the magnetisation of the variable permanent magnet, wherein altering the magnetisation of the variable permanent magnet causes a change in the rate of flow of the ferrofluid within the channel.

In this manner, a cooling system is provided that does not require a pump, and whereby the rate of flow of the cooling liquid can be adjusted without significantly impacting the efficiency or effectiveness of the cooling system. In particular, this cooling system does not require the supply of constant electrical power in order to function, nor does the cooling system suffer from added heat as a result of Joule heating. By adjusting the rate of flow of the ferrofluid, the cooling performance of the system can be adjusted, such that the efficiency of the cooling system can be continually maximised.

In some aspects, the electromagnet comprises an electrical coil, wherein the electrical coil is configured to generate the magnetic field in response to an electrical current. In this manner, the magnetic field pulse used to alter the magnetisation of the variable permanent magnet may be generated using a pulse of electrical current, providing an arrangement that is implementable without specialised equipment.

Further in this aspect, the cooling system may further comprise a source of electrical current, wherein the source of electrical current is configured to provide a pulse of electrical current to the electrical coil to generate the magnetic field. In other words, the source of electrical current may in some aspects be considered to form part of the cooling system, but in other aspects the source of electrical current may not form part of the cooling system but might be considered as an entity separate from the cooling system. The source of electrical current may be, for example, a battery or substantially any other entity that can provide electrical current to a coil such as a capacitor, a mains electrical connection, or a signal generator connected to a separate power source. In this manner, the pulse of electrical current can be generated with fine control as and when it is required, in order to alter the magnetisation of the variable permanent magnet, and hence alter the rate of flow of the ferrofluid.

Further advantageously in this aspect, the pulse of electrical current is between 1 and 1000 milliseconds long. In this manner, the magnetisation of the variable permanent magnet may be altered using only a short pulse of electrical current, thereby avoiding Joule heating of the coil and the extra energy expenditure associated with continually powering an electrical coil.

In some aspects, the electrical coil is coiled about the variable permanent magnet. Such an arrangement is compact in size, thereby allowing the cooling system to be used in smaller-scale applications. This arrangement also ensures that the electromagnet is in close proximity to the variable permanent magnet, thereby minimising the size of the current required to alter the magnetisation of the variable permanent magnet.

Advantageously, the cooling system may further comprise a heat exchanger (or heat sink) arranged proximate to the channel, the heat exchanger configured to transfer heat away from the ferrofluid. As such, the cooling performance of the cooling system can be improved as the heat exchanger is able to effectively dissipate heat out of the cooling system, thereby cooling the heated ferrofluid.

The heat exchanger may be arranged such that a thermally conductive pathway exists between the channel and the heat exchanger. For example, the heat exchanger may be in direct contact with the channel such heat can be transferred from the ferrofluid, to the walls of the channel, and directly to the heat exchanger. In other examples, one or more other thermally conductive components may be provided between the channel and the heat exchanger.

In some aspects, the variable permanent magnet is arranged proximate to at least a portion of the channel. For example, the variable permanent magnet may be arranged in contact with the channel itself. Alternatively, the variable permanent magnet may be located in a position so as to exert a magnetic field on a portion of the channel. The magnet may be located, for example, up to 5cm, 10cm, 20cm, or 30cm away from the channel, or may be located any other suitable distance away from the channel such that the strength of the magnetic field exerted by the variable permanent magnet on the ferrofluid is enough to drive thermomagnetic convection of the ferrofluid.

Advantageously in some aspects, the cooling system further comprises one or more temperature sensors configured to detect a temperature of the ferrofluid at one or more locations within the channel, and a controller configured to receive temperature data from the one or more temperature sensors, and further configured to cause the electromagnet to exert a magnetic field pulse on the variable permanent magnet based on the temperature data. In this manner, the rate of flow of the ferrofluid may be dynamically adjusted based on the real-time temperature of the ferrofluid, thereby adjusting the cooling performance of the cooling system. As such, the efficiency of the cooling system can always be maximised.

For example, the controller may generate a signal that is sent to a signal generator which generates an electrical current that is provided to an electromagnet, thereby causing the electromagnet to generate a magnetic field. The controller may, for example, include one or more processors, a memory and an input/output (I/O) interface. The controller may generate an electrical current sent to the electromagnet itself, or may generate a signal that is sent to a further entity (such as a signal generator) to generate the electrical current (or other suitable signal).

Further in this aspect, the controller may be configured to cause the electromagnet to exert a magnetic field pulse on the variable permanent magnet based on the temperature of the ferrofluid at the one or more locations within the channel rising above or falling below a predetermined threshold. For example, the rate of flow of the ferrofluid can be increased in response to an increase in temperature above a particular threshold, or the rate of flow of the ferrofluid can be decreased in response to a decrease in temperature below a particular threshold. As such, precise control of the rate of flow of the ferrofluid is possible, allowing for increased cooling efficiency.

In some aspects, the variable permanent magnet has a coercive force of between 100 and 1000kA/m. As such, the coercive force of the variable permanent magnet is large enough that the variable permanent magnet is able to maintain its magnetisation in the absence of a magnetic field exerted by the electromagnet, but also low enough that the magnetisation of the variable permanent magnet can be altered by a magnetic field generated by the electromagnet.

According to a second aspect of the invention, there is provided a method comprising: providing a channel comprising a ferrofluid; and causing the ferrofluid to flow within the channel by providing a variable permanent magnet that exerts a magnetic field on at least a portion of the ferrofluid within the channel, wherein the variable permanent magnet is a permanent magnet with variable magnetisation, and wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet; and changing the rate of flow of the ferrofluid by exerting a magnetic field pulse on the variable permanent magnet to alter the magnetisation of the variable permanent magnet, wherein the magnetic field pulse is exerted by an electromagnet.

In this manner, a cooling method is provided that does not require pumping of the cooling fluid, and whereby the rate of flow of the cooling liquid can be adjusted without significantly impacting the efficiency or effectiveness of the cooling system. In particular, this cooling method does not require the supply of constant electrical power in order to function, nor does the cooling system suffer from added heat because of Joule heating. By adjusting the rate of flow of the ferrofluid, cooling performance can be adjusted, such that the cooling efficiency can be continually maximised.

Advantageously, the method may further comprise: determining a temperature of the ferrofluid at one or more locations within the channel; and determining that the temperature of the ferrofluid at the one or more locations within the channel has risen above or fallen below a predetermined threshold; wherein changing the rate of flow of the ferrofluid is performed based on determining that the temperature of the ferrofluid at the one or more locations in the channel has risen above or fallen below a predetermined threshold. In this manner, the rate of flow of the ferrofluid may be dynamically adjusted based on the real-time temperature of the ferrofluid, thereby adjusting the cooling performance of the cooling system. As such, the efficiency of the cooling system can always be maximised, as precise control of the rate of flow of the ferrofluid is possible.

In some aspects, exerting a magnetic field pulse on the variable permanent magnet comprises providing an electrical current to an electrical coil. In this manner, the magnetic field pulse used to alter the magnetisation of the variable permanent magnet may be generated using a pulse of electrical current, providing an arrangement that is implementable without specialised equipment and which reduces inefficiencies and unwanted heating.

Advantageously in this aspect, the electrical coil is coiled about the variable permanent magnet. As such, the size of the current required to alter the magnetisation of the variable permanent magnet is minimised.

According to a third aspect of the invention, there is provided a computer-readable medium comprising instructions which, when executed by one or more processors, cause the processors to carry out the steps of: generating a signal causing an electromagnet to generate a magnetic field pulse to alter a magnetisation of a variable permanent magnet; wherein the variable permanent magnet is a permanent magnet with variable magnetisation, and wherein the variable permanent magnet is configured to exert a magnetic field on at least a portion of a ferrofluid within a channel to cause the ferrofluid to flow within the channel, wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet; and wherein altering the magnetisation of the variable permanent magnet causes a change in the rate of flow of the ferrofluid within the channel.

In this manner, a cooling arrangement is provided that does not require pumping of the cooling fluid, and whereby the rate of flow of the cooling liquid can be adjusted without significantly impacting the efficiency or effectiveness of the cooling arrangement. In particular, this cooling arrangement does not require the supply of constant electrical power to an electromagnet (or similar component) in order to function, nor does the cooling system suffer from added heat because of Joule heating. By adjusting the rate of flow of the ferrofluid, cooling performance can be adjusted, such that the cooling efficiency can be continually maximised.

Advantageously, the computer-readable medium may further comprise instructions which, when executed by one or more processors, cause the processors to further carry out the steps of: determining a temperature of a ferrofluid at one or more locations within a channel; determining that the temperature of the ferrofluid at the one or more locations has risen above or fallen below a predetermined threshold; and based on determining that the temperature of the ferrofluid at the one or more locations has risen above or fallen below a predetermined threshold, generating the signal causing the electromagnet to generate the magnetic field pulse.

In this manner, the rate of flow of the ferrofluid may be dynamically adjusted based on the real-time temperature of the ferrofluid, thereby adjusting the cooling performance of the cooling system. As such, the efficiency of the cooling system can always be maximised, as precise control of the rate of flow of the ferrofluid is possible.

In some aspects, the computer-readable medium may further comprise instructions which, when executed by one or more processors, cause the processors to further carry out the steps of: receiving temperature data from one or more temperature sensors located at the one or more locations; wherein determining the temperature of a ferrofluid at one or more locations within the channel is based on the received temperature data. As such, the temperature data and processing may be carried out at the entity that generating a signal causing an electromagnet to generate a magnetic field pulse, providing for a standalone entity capable of executing the above-described steps, providing ease of use.

Advantageously in some aspects, generating a signal causing the electromagnet to generate a magnetic field pulse comprises providing a pulse of electrical current to an electrical coil. In this manner, the magnetic field pulse used to alter the magnetisation of the variable permanent magnet may be generated using a pulse of electrical current, providing an arrangement that is implementable without specialised equipment and which reduces inefficiencies and unwanted heating.

In some aspects, generating a signal causing the electromagnet to generate a magnetic field pulse comprises providing a signal to a source of electrical current to cause the source of electrical current to provide a pulse of electrical current to an electrical coil. Accordingly, the exact duration and timing of the pulse of electrical current maybe finely controlled, allowing for precise control of the rate of flow of the ferrofluid.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the following figures.

In accordance with one (or more) embodiments of the present invention the Figures show the following: Figure 1 shows a cooling system according to a first comparative example comprising a permanent magnet arranged to exert a constant magnetic field on a ferrofluid within a channel.

Figure 2 shows a cooling system according to a second comparative example comprising a solenoid arranged to exert a magnetic field on a ferrofluid within a channel, when supplied with an electric current.

Figure 3 shows a cooling system according to a first example teaching of the disclosure, comprising a variable permanent magnet.

Figure 4 shows a flowchart of a cooling method according to a second example teaching of the disclosure.

Figure 5 shows a computer system according to a third example teaching of the disclosure.

Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to". The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. It will also be recognised that the invention covers not only individual embodiments but also combination of the embodiments described herein.

The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Detailed Description

Figure 1 illustrates a cooling system 100 according to a first comparative example. The cooling system 100 includes a channel 110 comprising a ferrofluid. A ferrofluid is a colloidal fluid of magnetic particles and is therefore susceptible to an external magnetic field. The cooling system 100 is located in the vicinity of a heat source 120. The heat source 120 may be a mechanical or electrical component that generates heat during use. Some of said heat is transferred from the heat source 120 to a portion of the ferrofluid within the channel 110. This causes the magnetic susceptibility of the heated portion of the ferrofluid to decrease, meaning the ferrofluid has a non-uniform magnetic susceptibility.

The cooling system 100 further includes a permanent magnet 130. The permanent magnet 130 exerts a magnetic field on at least a portion of the ferrofluid within the channel 110. The combination of the magnetic field created by the permanent magnet 130 and the heating of the ferrofluid by the heat source 120 (causing the ferrofluid to have a non-uniform magnetic susceptibility) creates a Kelvin body force within the ferrofluid, leading to thermomagnetic convection of the ferrofluid within the channel 110. In this manner, the ferrofluid flows within the channel 110 without requiring an active pumping system or a constant supply of electrical power. Rather, the rate of flow of the ferrofluid within the channel 110 is dependent at least partly on the strength of the magnetic field exerted on the ferrofluid by the permanent magnet.

The cooling system further comprises a heat exchanger (or heat sink) 140. In this manner, the heated ferrofluid flows through the channel 100 to the heat exchanger 140. The heat transferred to the ferrofluid by the heat source 120 may then be transferred to the heat exchanger 140 and then out of the cooling system 100.

In the first comparative example of Figure 1, permanent magnet 130 is located upstream of the heat source 120 and may be located downstream of the heat exchanger 140. As the channel 110 is a closed channel, the permanent magnet might, in some interpretations, be seen as also being downstream of the heat source 120. However, for the purposes of brevity, "upstream" should be understood as meaning the length of the channel 110 from the heat source 120 to the permanent magnet 130 in a direction of flow of the ferrofluid is greater than a length of the channel 110 from the heat source 120 to the permanent magnet 130 in a direction opposite the direction of flow of the ferrofluid. The term "downstream" should be understood as having the opposite meaning. Furthermore, while the terms "upstream" and "downstream" are explained above in relation to the heat source 120 and the permanent magnet 130, these terms may be equally applied, mutatis mutandis, to any other components included in the cooling system or otherwise, such as heat exchanger 140. The direction of flow of the ferrofluid within the channel 110 is shown by the arrows in Figure 1.

The rate of flow of the ferrofluid in the cooling system 100 of Figure 1 cannot be readily changed when desired. As explained above, the rate of flow of the ferrofluid depends on the strength of the magnetic field exerted on the ferrofluid by the permanent magnet 130. This is not changeable in the cooling system 100.

Figure 2 illustrates a cooling system 200 according to a second comparative example. The cooling system 200 includes a channel 210 comprising a ferrofluid, similar to channel 110 of the cooling system 100 of Figure 1. The cooling system 200 is located in the vicinity of a heat source 220. The cooling system further includes a solenoid 230, instead of the permanent magnet 130 used in the cooling system 100 of Figure 1. The solenoid 230 may be wound around a portion of the channel 210, as shown in Figure 2, or may be located proximate to the channel 230. The cooling system 200 may also include a heat exchanger (or heat sink) 240 similar to heat exchanger 140.

In the cooling system 200, an electrical current is supplied to the solenoid 230, thereby causing the solenoid 230 to create a magnetic field. This magnetic field interacts with the ferrofluid and act to induce a Kelvin body force and cause thermomagnetic convection, in a similar manner to the magnetic field created by the permanent magnet 130 of the cooling system 100 of Figure 1.

However, the strength of the magnetic field created by the solenoid 230 is dependent on the size of the electrical current provided to the solenoid 230. As such, the strength of the magnetic field can be varied when desired by varying the size of the electrical current provided to the solenoid, thereby varying the rate of flow of the ferrofluid within the channel 210.

However, in order to supply a magnetic field, the solenoid 230 requires a constant supply electrical current. Furthermore, when supplied with electrical current, the coil of the solenoid 230 will experience Joule heating, thereby introducing more heat into the cooling system 200 and the ferrofluid within the channel 210. These two factors reduce the efficiency and the effectiveness of the cooling system 200 of Figure 2.

Figure 3 illustrates a cooling system 300 according to a first teaching of the disclosure. The cooling system 300 includes a channel 310 including a ferrofluid in similar manner to channels 110 and 210.

In some examples, the ferrofluid comprises between approximately 2% and 18% ferromagnetic particles by volume. The cooling system 300 is provided to dissipate heat away from heat source 320. For example, the channel 310 may be located proximate to the heat source 320 or may be arranged such that a conductive pathway exists between the channel 310 and the heat source 320.

The cooling system 300 further includes a variable permanent magnet 330 (for example located upstream of the heat source 320). Variable permanent magnet 330 is a permanent magnet with a variable magnetisation. As an example, variable permanent magnet may be a permanent magnet with a coercive force (i.e. magnetic coercivity) of between 100 and 1000kA/m, preferably between 100 and 700kA/m (for example, NdFeB magnets may not necessarily be suitable for use as the variable permanent magnet 330 of the cooling system 300 due to having too large a coercive force).

A variable permanent magnet with a relatively low coercive force such as this is programmable, such that its magnetisation can be changed, but also maintains its magnetisation state once programmed. The strength of the magnetic field exerted by the variable permanent magnet 330 on the ferrofluid within the channel 310 is dependent on the magnetisation of the variable permanent magnet 330.

The cooling system further comprises an electromagnet 335. In the cooling system 300, the electromagnet 335 is a coil wrapped around the variable permanent magnet 330, however other implementations are possible. For example, the electromagnet 335 may be substantially any other form of electromagnet that produces a magnetic field in response to an electric current. The electromagnet 335 is located such that when provided with an electrical current, the electromagnet 335 exerts a magnetic field on the variable permanent magnet. A coil 335 wrapped around the variable permanent magnet 330 achieves this purpose while minimising the footprint of the electromagnet 335, however the electromagnet 335 may be separate from the variable permanent magnet 330 and located, for example, proximate to or within a short distance (such as 10cm) of the variable permanent magnet 330.

In response to a pulse (for example between 1 and 1000ms long) of electrical current, the electromagnet 335 generates a magnetic field pulse which is exerted on the variable permanent magnet 330. This magnetic field pulse alters the magnetisation of the variable permanent magnet 330, thereby altering the strength of the magnetic field generated by the variable permanent magnet 330. By altering the strength of the magnetic field generated by the variable permanent magnet 330, the rate of flow of the ferrofluid within the channel 310 can therefore be altered.

This is particularly advantageous as the ferrofluid can flow within the channel 310 without requiring a constant power source (in contrast to the cooling system 200 of Figure 2), and the rate of flow of the ferrofluid can be adjusted (in contrast to the cooling system 100 of Figure 1) using a short pulse of electrical current, rather than requiring a continual supply of electrical current (in contrast to the cooling system 200 of Figure 2) which would introduce further heat into the system. The cooling system 300 therefore has a dynamically adjustable ferrofluid flow rate, without significantly reducing the effectiveness or efficiency of the cooling, and without requiring an active pumping device.

The cooling system 300 may, as shown in Figure 3, additionally include a heat exchanger (or heat sink) 340 which may be similar to heat exchangers 140 and 240, in order to more effectively dissipate heat away from the cooling system 300. The channel 310 may additionally be thermally insulated except for the portions of the channel 310 arranged to be heated by the heat source 320 and arranged to interface with the heat exchanger 340. Furthermore, as shown in Figure 3, the cooling system 300 may additionally include one or more temperature sensors 350a, 350b arranged to detect (or measure) the temperature of the ferrofluid. As such, the rate of flow of the ferrofluid may be adjusted based on the temperature of the ferrofluid, thereby allowing fine control of cooling performance based on real-time temperature information, such that the cooling efficiency can always be maximised.

The cooling system 300 may be provided in a number of different scenarios. For example, the cooling system 300 may be used to cool one or more mechanical components of an automobile, or an aeroplane. Alternatively, the cooling system 300 may be used to cool electrical components which, for example, produce heat via Joule heating.

Figure 4 illustrates method 400 according to a second example teaching of the disclosure. The method 400 includes a step 410 of providing a channel comprising a ferrofluid. The method further includes a step 420 of causing the ferrofluid to flow within the channel by providing a variable permanent magnet that exerts a magnetic field on at least a portion of the ferrofluid within the channel, wherein the variable permanent magnet is a permanent magnet with variable magnetisation, and wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet. In addition, the method includes the step 430 of changing the rate of flow of the ferrofluid by exerting a magnetic field pulse on the variable permanent magnet to alter the magnetisation of the variable permanent magnet, wherein the magnetic field pulse is exerted by an electromagnet.

The method 400, may, in some example, further include the steps of determining a temperature of the ferrofluid at one or more locations within the channel, and determining that the temperature of the ferrofluid at the one or more locations within the channel has risen above or fallen below a predetermined threshold, wherein changing the rate of flow of the ferrofluid is performed based on determining that the temperature of the ferrofluid at the one or more locations in the channel has risen above or fallen below a predetermined threshold.

Figure 5 illustrates a computing device 500 according to a third example teaching of the disclosure. The computing device 500 includes one or more processors 510, a memory 520, and one or more input/output (I/O) interfaces 530. The I/O interface may be configured to receive and transmit one or more instructions and to communicate with the one or more processors 510 and/or the memory 520 to execute particular steps. For example, the I/O interface may be configured to generate an electrical signal to be transmitted to a signal generator (which in turn supplies a pulse of electrical current to an electromagnet, such as the electromagnet 335 of Figure 3), or the I/O interface may generate such a pulse of electrical current itself.

The computing device 500 may include a computer-readable medium comprising instructions which, when executed by one or more processors 510, cause the processors to generate a signal causing an electromagnet to generate a magnetic field pulse to alter a magnetisation of a variable permanent magnet; wherein the variable permanent magnet is a permanent magnet with variable magnetisation, and wherein the variable permanent magnet is configured to exert a magnetic field on at least a portion of a ferrofluid within a channel to cause the ferrofluid to flow within the channel, wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet; wherein altering the magnetisation of the variable permanent magnet causes a change in the rate of flow of the ferrofluid within the channel.

The computer-readable medium may, for example, be a non-transitory computer-readable medium such as the memory 520 on which said instructions are stored, which when executed by the one or more processors 510 cause the one or more processors 510 to execute the above steps. The instructions may, in some cases, be stored on any other non-transitory computer-readable medium which is or is not part of the computing device 500. Additionally or alternatively, the computer-readable medium may be a transitory computer-readable medium such as a signal between the memory 520 and the one or more processors 510 which cause the one or more processors 510 to execute the above steps, or a signal generated by I/O interface 530. Such a transitory computer-readable medium may be transported over a network or via substantially any other means towards the one or more processors 510 or from I/O interface 530.

Therefore, from one perspective, there has been described cooling systems and methods including providing a channel comprising a ferrofluid, providing a variable permanent magnet that exerts a magnetic field on at least a portion of the ferrofluid within the channel, and an electromagnet configured to exert a magnetic field pulse on the variable permanent magnet to alter the magnetisation of the variable permanent magnet, wherein altering the magnetisation of the variable permanent magnet causes a change in the rate of flow of the ferrofluid within the channel.

Claims

Claims 1. A cooling system comprising: a channel comprising a ferrofluid; a variable permanent magnet, wherein the variable permanent magnet is a permanent magnet with variable magnetisation, wherein the variable permanent magnet is configured to exert a magnetic field on at least a portion of the ferrofluid within the channel to cause the ferrofluid to flow within the channel, wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet; and an electromagnet configured to exert a magnetic field pulse on the variable permanent magnet to alter the magnetisation of the variable permanent magnet, wherein altering the magnetisation of the variable permanent magnet causes a change in the rate of flow of the ferrofluid within the channel.
2. The cooling system of claim 1, wherein the electromagnet comprises an electrical coil, wherein the electrical coil is configured to generate the magnetic field in response to an electrical current.
3. The cooling system of claim 2, further comprising: a source of electrical current, wherein the source of electrical current is configured to provide a pulse of electrical current to the electrical coil to generate the magnetic field.
4. The cooling system of claim 3, wherein the pulse of electrical current is between 1 and 1000 milliseconds long.
5. The cooling system of any of claims 2-4, wherein the electrical coil is coiled about the variable permanent magnet.
6. The cooling system of any preceding claim, further comprising: a heat exchanger arranged proximate to the channel, the heat exchanger configured to transfer heat away from the ferrofluid.
7. The cooling system of any preceding claim, wherein the variable permanent magnet is arranged proximate to at least a portion of the channel.
8. The cooling system of any preceding claim, further comprising: one or more temperature sensors configured to detect a temperature of the ferrofluid at one or more locations within the channel; and a controller configured to receive temperature data from the one or more temperature sensors, and further configured to cause the electromagnet to exert a magnetic field pulse on the variable permanent magnet based on the temperature data.
9. The cooling system of claim 8, wherein the controller is configured to cause the electromagnet to exert a magnetic field pulse on the variable permanent magnet based on the temperature of the ferrofluid at the one or more locations within the channel rising above or falling below a predetermined threshold.
10. The cooling system of any preceding claim, wherein the variable permanent magnet has a coercive force of between 100 and 1000kA/m.
11. A method comprising: providing a channel comprising a ferrofluid; causing the ferrofluid to flow within the channel by providing a variable permanent magnet that exerts a magnetic field on at least a portion of the ferrofluid within the channel, wherein the variable permanent magnet is a permanent magnet with variable magnetisation, and wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet; and changing the rate of flow of the ferrofluid by exerting a magnetic field pulse on the variable permanent magnet to alter the magnetisation of the variable permanent magnet, wherein the magnetic field pulse is exerted by an electromagnet.
12. The method of claim 11, further comprising: determining a temperature of the ferrofluid at one or more locations within the channel; and determining that the temperature of the ferrofluid at the one or more locations within the channel has risen above or fallen below a predetermined threshold; wherein changing the rate of flow of the ferrofluid is performed based on determining that the temperature of the ferrofluid at the one or more locations in the channel has risen above or fallen below a predetermined threshold.
13. The method of claim 11 or claim 12, wherein exerting a magnetic field pulse on the variable permanent magnet comprises providing an electrical current to an electrical coil.
14. The method of claim 13, wherein the electrical coil is coiled about the variable permanent magnet.
15. A computer-readable medium comprising instructions which, when executed by one or more processors, cause the processors to carry out the steps of: generating a signal causing an electromagnet to generate a magnetic field pulse to alter a magnetisation of a variable permanent magnet; wherein the variable permanent magnet is a permanent magnet with variable magnetisation, and wherein the variable permanent magnet is configured to exert a magnetic field on at least a portion of a ferrofluid within a channel to cause the ferrofluid to flow within the channel, wherein a rate of flow of the ferrofluid is based on the magnetisation of the variable permanent magnet; and wherein altering the magnetisation of the variable permanent magnet causes a change in the rate of flow of the ferrofluid within the channel.
16. The computer-readable medium of claim 15, wherein the computer-readable medium further comprising instructions which, when executed by one or more processors, cause the processors to further carry out the steps of: determining a temperature of a ferrofluid at one or more locations within a channel, determining that the temperature of the ferrofluid at the one or more locations has risen above or fallen below a predetermined threshold; and based on determining that the temperature of the ferrofluid at the one or more locations has risen above or fallen below a predetermined threshold, generating the signal causing the electromagnet to generate the magnetic field pulse.
17. The computer-readable medium of any of claims 15-16, wherein the computer-readable medium further comprising instructions which, when executed by one or more processors, cause the processors to further carry out the steps of: receiving temperature data from one or more temperature sensors located at the one or more locations; wherein determining the temperature of a ferrofluid at one or more locations within the channel is based on the received temperature data.
18. The computer-readable medium of any of claims 15-17, wherein generating a signal causing the electromagnet to generate a magnetic field pulse comprises providing a pulse of electrical current to an electrical coil.
19. The computer-readable medium of any of claims 15-17, wherein generating a signal causing the electromagnet to generate a magnetic field pulse comprises providing a signal to a source of electrical current to cause the source of electrical current to provide a pulse of electrical current to an electrical coil.