AN ELECTROMAGNETIC PUMP

The invention relates to an electromagnetic pump for the propulsion of an electrically conductive liquid in one or more channels, wherein a DC current is supplied transversely to the channel and a DC magnetic field is supplied transversely to the direction of flow, or wherein a magnetic travelling field is applied longitudinally of the channel, said magnetic travelling field generating propulsion in the electrically conductive liquid by means of self-induction in the liquid, and wherein the electromagnetic pump is coupled to a profile having one or more channels.

An electromagnetic pump generates propulsion of an electrically conductive liquid in a pipe, in which a DC current is supplied transversely to the pipe and a DC magnetic field is supplied transversely to the direction of flow.

Such a pump, which is known e.g. from US Patent No. 5,763,951, is unique in that there are no movable parts in the operation of the pump, which means in principle that it is indestructible.

The efficiency of such a pump depends on how much electric current runs in the liquid fed, as it is the interaction between an electric current and a magnetic field which contributes to the generation of movement of the electrically conductive liquid.

Cooling of ICs, processors and the like is necessary owing to the efficiency of these components. However, cooling of such components involves costs.

A well-known and traditional way of cooling ICs, processors and the like is to use cooling profiles having fins, to which an air flow is transferred from a blower.

A drawback of the use of cooling profiles, which may be made as extruded profiles, is that the heat from the component to be cooled takes place through heat conduction through the profile out to the ambient air, there being great temperature differences from the contact area of the profile with the component to be cooled and out to the area where the profile gets into contact with the air.

Another and more efficient way of cooling circuit components is the use of so-called heat pipes, which are known e.g. from US Patent Application No. 2007/0095507. In this manner, heat is absorbed from the one end (the hot end) of a heat pipe, where liquid evaporates, and is transferred to the other end (the cold end), where the liquid condenses. The liquid returns to the hot end by means of a porous material, a so-called wick, which may consist of ceramic metal oxides.

An advantage of the use of heat pipes is that a uniform temperature can be created on the cold side of it. This form of cooling also involves some limitations. Depending on where heat pipes are to be used, they must be designed according to their use. An important factor is the thickness of the wick, which is proportional to the thermal resistance. In practice, it should preferably be as thin as possible, but a thinner wick creates greater pressure losses, which sets limits to the heat transmission.

Another type of cooling is the use of water cooling. Water cooling of PC's, processors and the like is inexpedient in many ways, partly because water is a very poor thermal conductor, and partly because it is a relative expensive form of cooling in practice.

Accordingly, an object of the invention is to provide a cooling system, which is more efficient, and which is relatively inexpensive to manufacture.

The object of the invention is achieved in that the electromagnetic pump is coupled to a profile having one or more channels, and that the electromagnetic pump is constructed such that it has the same cross-section as the profile.

When, as stated in claim 2, the profile is configured such that one or more channels extend side by side in one or more layers and are distributed across the cross-section of the profile, a great flexibility is achieved with respect to the ability of dimensioning the electromagnetic pump for a given task.

When, as stated in claim 3, the channels of the profile are configured with a rectangular cross-section, it is possible to create a large opening area having a great width and a small height, so that the counterpressure is kept down at a reasonable level.

When, as stated in claim 4, a cooling head having the same cross-section as the profile is integrated in the profile, it is ensured that the cooling head does not have to be made separately.

To make the cooling power of the electromagnetic pump more effective, it is advantageous, as stated in claim 5, that the pump housing of the electromagnetic pump is made of a weakly electrically conductive material, and, as stated in claim 6, that the cooling head is made in part of a highly heat conductive material.

When, as stated in claim 8, the area around the pump housing is anodized or treated similarly, it is ensured that the current from the electrodes does not run out into the aluminium, of which the profile may be made.

Further expedient embodiments of the invention are defined in claims 7 and 9 - 13.

The invention will now be explained more fully with reference to the draw- ing, in which

fig. 1 shows the principle of an electromagnetic pump,

fig. 2 shows the principle of an extruded profile for the cooling system according to the invention,

fig. 3 shows the principle of the construction of the electromagnetic pump for the embodiment shown in fig. 2,

fig. 4 shows the parts of fig. 2 and fig. 3 assembled,

fig. 5 shows a complete cooling system according to the invention,

fig. 5a shows slitted cooling fins,

fig. 6 shows the principle of an extruded cooling system having an electromagnetic pump according to the invention in a second embodiment, while

fig. 7 shows the principle of an extruded cooling system having an electromagnetic pump according to the invention in a third embodiment,

fig. 8 shows the principle of an extruded cooling system having chan- nels in layers,

fig. 9 shows an embodiment of an electromagnetic pump having channels in layers, and

fig. 10 shows a cooling system assembled from the parts shown in fig. 8 and fig. 9.

In fig. 1 , the numeral 2 designates a section of a pipe through which a conductive liquid is transported. The pipe 2 has a constriction 8 (which is advantageously constructed to be rectangular), with which an electrical con- ductor (electrode) 3 is connected, to which a positive or negative current may be supplied in the direction of the arrow 4.

A magnetic circuit is inserted perpendicularly to the electrical conductor at the constriction 8. The magnetic circuit is formed by a magnet, e.g. a per- manent magnet or an electromagnet composed of a magnet 5 which is provided with a winding 6 on part of its surface.

As is known from the science of magnetism, a conductor supplied with current and being present in a magnetic field will be affected by a force. Since an electrically conductive liquid is present in the pipe, this liquid will be caused to move, if a DC current is supplied to the liquid and a DC magnetic field is applied perpendicularly to the current. Such a setup is also called an electromagnetic pump.

It should be observed in this connection that the electromagnetic pump can also run AC current and AC magnetic field, if current and field alternate at the same time.

Clearly, the higher the electric current, the faster the flow rate of the liquid at the same field strength. Therefore, it is important to use a liquid having an extremely good electrical conductivity, as, otherwise, the voltage for

driving the current will be problematically high.

Advantageously, a suitable liquid consists of a mixture of the alkali metals sodium (Na) and potassium (K).

It may be mentioned by way of example that the mixture has an electrical conductivity of about 40 microohms -cm at the eutectic point.

Since, as mentioned, the liquid (NaK) has excellent thermodynamic and cooling-technical properties, the electromagnetic pump according to the invention may find application in a setup as shown in fig. 2.

Fig. 2 shows the principle of an extruded object according to the invention in a first embodiment. Here, the profile 1 is bent into a shape which may be used for the cooling of a CPU in a PC. In fig. 2, the numeral 9 designates a section of an extruded profile, with a cooling head 10 integrated in the same unit. As will be seen, the profile has four rounded corners 1A, 1 B, 1C, and 1 D, there being a gap 1 E between the two corners 1C, 1 D. Moreover, the profile has a cooling head 10 and channels 11 which extend side by side in a plane, and in which conductive liquid may be transported. The cooling head is intended to cool an IC circuit 14. Advantageously, the profile may be made of aluminium, since it is extremely suitable for being extruded.

To create flow in the channels 11 , an electromagnetic pump is mounted in the gap 1 E between an inlet 12 and an outlet 13 of the profile 1.

Such an electromagnetic pump is shown in fig. 3. Here, the electromagnetic pump 15 is shown with three channels 11 in a plane, such that it is suited for the propulsion of the medium in the extruded profile having three chan- nels 11 , shown in fig. 2, as the electromagnetic pump may be inserted into the gap 1 E.

Another number of channels than three arranged in a plane is also possible, according to the cooling task to be solved.

For example, in some applications, it is an advantage to have just a single channel, which makes the configuration of the pump very simple,

In this structure of the profile 1 , as illustrated in fig. 2, and of the pump 15, as illustrated in fig. 3, it is possible to extrude the channels 11 with a very small height, which is particularly important when a highly heat conductive medium, such as sodium and potassium, is pumped. As electromagnetic pumps cannot generate any great pressure, the width of the channels may be increased, thereby creating a large opening area, as a result of which the counterpressure in the profile may be minimized.

In fig. 3, the numeral 15 designates a section of the electromagnetic pump having electrodes 7, where the one may advantageously be used as a filling stub. As will be seen, the pump has two partitions 17 with holes 18 to optimize the travel of electrons between the electrodes 7. It should be men- tioned that the permanent magnets are omitted in fig. 3, but, normally, but not necessarily, they will be disposed at the top and at the bottom of the pump 5. The pump is made of a weakly electrically conductive material, which might be stainless steel.

The extruded profile of fig. 2 is also shown in fig. 4, where the pump of fig. 3 is built together with the profile. In fig. 4, the numeral 9 designates a section of the extruded profile 1 , where a cooling head 10 and the electromagnetic pump 15 are integrated in the same unit. The liquid is conveyed through the internal channels in the profile and through the cooling head 10, where the liquid absorbs the energy from an IC 14. The liquid is conveyed in the channels by the electromagnetic pump 15. Here, the pump 15 is shown with the

electrodes 7 and a permanent magnet 24.

Since aluminium conducts the current efficiently, anodization or a similar treatment may advantageously be applied around the pump housing in or- der to enhance the electrical resistance from the medium and out into the material of the extruded profile.

Fig. 5 also shows the extruded object, as is shown in fig. 2, but now shown in a complete setup, where the profile 21 is mounted with slitted fins 19 and a blower 20. The electromagnetic pump 15 is seated at the top. The profile 21 has mounted thereon fins 19, which may advantageously be mounted at the same time as a coherent stack. When, as shown in fig. 5A, slitted fins 19 to be mounted on the profile 21 are used, a better and more uniform heat transfer is generated from the medium and out to the fins. The slit is configured with the same cross-section as the profile 21. This structure of the fins provides further advantages in terms of production, as it may be decided freely whether the pump or the fins are to be mounted first.

Fig. 6 shows the principle of an extruded object according to the invention in a second embodiment. In fig. 6, the numeral 36 designates a section of an extruded profile, where a cooling head 37 and a heat exchanger 38 are integrated in the same unit. A conductive liquid is transported in a channel 39 in the longitudinal direction of the entire profile. The liquid is conveyed into the channel 39 and into the cooling head 37, where the liquid absorbs the energy from an IC 40. The liquid is conveyed further in the channel 39, which terminates at the centre of the profile. Then, the liquid is conveyed back to the inlet of the channel 39 at the cooling head 37 via an external connecting pipe (not shown). An external, electromagnetic pump is mounted on this connecting pipe. The rest of the profile is constructed so that the energy absorbed from the IC 40 is conveyed as efficiently as possible forwards to the ambient air, which is conveyed through the channels

41 and past the external area of the profile. Advantageously, the object may be made of aluminium, since it is extremely suitable for being extruded. Covers are mounted at the ends of the profile, so that the channels for the liquid are closed.

Fig. 7 shows the principle of a pump according to the invention in a further embodiment. In fig. 7, the numeral 52 designates a section of an extruded profile, where the electromagnetic pump, as described in connection with fig. 6, is integrated in a heat exchanger 62. The profile may advantageously be constructed so as to be a secondary pump chamber 56. A permanent magnet 59 is provided between the cooling head 58 and a pump chamber 54. The magnetic lines of flux strongly affect both the lower pump chamber and the upper pump chamber. The liquid is conveyed into a channel 55 and into the cooling head 58, and optionally into the secondary pump chamber 56, where the liquid absorbs the energy from an IC 57, following which the liquid is conveyed up into the pump chamber 54, where the primary propulsion is created. The liquid is conveyed further in the channel 55. The rest of the profile is constructed such that the energy absorbed from the IC is conveyed as efficiently as possible to the ambient air, which is conveyed through channels 61 and past the external area of the profile. With this form of structure, it is possible in principle to eliminate costs for the cooling head and the pump chamber. The return flow of the liquid from the centre 53 of the profile to the cooling head 58 takes place via a connecting pipe (not shown), as described in connection with fig. 6.

It should moreover be mentioned that the difference between the embodiments of fig. 6 and fig. 7 is that the embodiment of fig. 6 operates with a separate electromagnetic pump, while the embodiment of fig. 7 has an incorporated electromagnetic pump.

Fig. 8 shows a further embodiment of an extruded profile object according

to the invention. In the figure, the numeral 1 designates a section of the extruded profile which is configured with an upper channel and a lower channel 11 , where the cooling head 10 is integrated in the lower channel. The cooling head is intended to cool the IC 14. A pump 15 is mounted at the end 12 of the profile 1 to create propulsion of the cooling medium in the channels 11.

Such an electromagnet pump is shown in fig. 9. Here, the electromagnetic pump 15 is shown with two channels, so that it is optimized for the propul- sion of the medium in the profile, shown in fig. 8, which has two channels. Another number of channels which is optimum for a given application to be cooled, is also possible, of course.

In fig. 9, the electromagnetic pump is designated 15, with the electrodes 7 for the pumping of the medium in the lower one of the channels 11. The permanent magnets are omitted in the figure, but they will primarily be disposed above and below the pump 15. The pump is made of a weakly electrically conductive material, such as e.g. stainless steel.

Fig. 10 also shows the extruded profile 1 of fig. 8, where the pump 15 of fig. 9 is built together with the profile. A manifold 23 is mounted at each end of the profile, so that the conductive liquid may circulate between the upper and lower channels.

In fig. 10, the numeral 1 designates a section of the extruded profile with the integrated cooling head 10, with which the electromagnetic pump 15 and the manifold 23 are connected, so as to provide an assembled unit. The liquid is conveyed through the internal channels in the profile and through the cooling head, where the liquid absorbs the energy from the IC 14. The liquid is pumped around in the channels by the electromagnetic pump 15. The pump is shown with the electrodes 7 and a permanent mag-

net 24. A manifold 23 is mounted at the end of the profile and the pump, thereby establishing a connection between the upper and lower channels. The profile of fig. 10 may advantageously be extruded with cooling fins on the upper part, so that the heat absorbed from the IC may efficiently be conveyed to the surroundings. Alternatively, a heat exchanger may be mounted on the profile.