An electromagnetic pump

The invention relates to an electromagnetic pump for propelling an electrically conducting liquid in at least two pipes, wherein an electric current is applied via two electrodes which are arranged perpendicularly to the pipes, and a magnetic field is applied perpendicularly relative to the direction of the electric current.

Such an electromagnetic pump is known e.g. from US Patent No. 5 763 951 and from US Patent Application No. 2005/0160752.

It is described in the last-mentioned publication how electromagnetic pumps may be arranged in series or in parallel in setups in which the electromagnetic pumps are independent units.

Since, advantageously, the electromagnetic pumps are used for the cooling of circuit elements, such as microprocessors, IC circuits and the like, it is an advantage if they are fed with electric current from these circuit elements.

Normally, however, it is relatively low currents which may be derived from such circuit elements, which means that the electric current which may be supplied to the electromagnetic pump, has a size which causes the flow of liquid in the electromagnetic pump to be so low that a sufficient cooling cannot be achieved.

Accordingly, an object of the invention is to provide an electromagnetic pump, in which the flow of liquid may be increased and be made sufficiently large by the supply of current from the stated circuit elements.

The object of the invention is achieved by an electromagnetic pump of the type defined in the introductory portion of claim 1 , which is characterized in

that a housing is inserted between the pipes, so that the liquid in the pipes is conveyed into the housing and from there out of the housing back into the pipes, and that the electrodes are arranged at two opposed sides of the housing.

In this manner, it is possible to establish a sufficient pumping effect by the use of a relatively low current through the liquid.

When, as stated in claim 2, the pipes have different inside diameters, it is possible to adapt the electromagnetic pump for the cooling of several circuit elements, said circuit elements requiring a greater or a smaller cooling effect.

To ensure that the current in the electrically conducting liquid is affected optimally, i.e. flows linearly between the electrodes, it is advantageous, as stated in claim 3, that an inwardly protruding barrier is provided inside the housing between the pipes, and, as stated in claim 4, that the inwardly protruding barriers are disposed at the two sides of the housing where the pipes enter and leave the housing, and, as stated in claim 5, that there is a distance between opposed barriers at the two sides of the housing.

As an alternative to the provision of the barriers in the housing, it may be an advantage in terms of production, if, as stated in claim 6, the housing is provided with constrictions in the form of notches between the pipes.

It is also an advantage, if, as stated in claim 7, the barriers or the constrictions at each side of the housing are connected with each other by means of a current conductor, as this results in a very linear current course between the electrodes.

To ensure that the greatest possible current flows through the liquid, it is

moreover expedient, as stated in claim 8, that the housing is made of an electrically insulating or slightly electrically conducting material, and, as stated in claim 9, that the barriers are made of an electrically insulating or slightly electrically conducting material.

In a practical implementation of the invention for the cooling of microprocessors, IC circuits and the like, it is expedient, as stated in claim 10, that the pipes and the housing form a closed circuit, in which a heat exchanger as well as a cooling plate are inserted between the pipes.

As mentioned, the invention also relates to a use. This use is defined in claim 11.

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

fig. 1 shows the principle of the structure of an electromagnetic pump,

fig. 2 shows the principle of an electromagnetic pump according to the invention,

fig. 3 shows the electromagnetic pump of fig. 2, seen from above,

fig. 4 shows a variant of the electromagnetic pump of fig. 2,

fig. 5 shows a variant of the electromagnetic pump of fig. 4,

figs. 6A-6C show the current course between the electrodes in various embodiments of an electromagnetic pump,

fig. 7 shows a physical setup in which the electromagnetic pump of figures 2 - 5 is included.

In fig. 1 , the numeral 1 designates a section of a pipe through which a con- ducting liquid is transported. The pipe 1 has a constriction 8 (which may advantageously be configured as a rectangle), to which an electrical conductor (an electrode) 3 is connected, to which a positive or negative current may be applied in the direction of the arrow 4.

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

As will be known from the science of magnetism, a conductor which receives current and is present in a magnetic field, will be affected by a force. Since an electrically conducting liquid is present in the pipe, this liquid will be caused to move if a DC current and DC magnetic filed, applied perpendicularly to the current, are applied to the liquid. Such a setup is also known under the designation an electromagnetic pump.

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

Clearly, the greater the electric current is, the faster the rate of flow of the liquid will be at the same field strength. Therefore, it is important to use a liquid having an extremely good electric conductivity, since, otherwise, the voltage to drive the current will be problematically high.

A suitable liquid advantageously consists of a mixture of the alkali metals

sodium (Na) and potassium (K). By way of example it may be mentioned that the mixture has an electric conductivity of about 40 microohm-cm at the eutectic point.

To ensure a better pumping effect, the setup shown in fig. 1 may be changed, so that the pipe 1 is replaced by five pipes connected in parallel, as illustrated in figure 2 (seen from above in figure 3).

Electrically conducting liquid may be transported through these pipes 9A, 9B, 9C, 9D, 9E to a housing 11 having a compartment 15 and from there further through the pipes 9F, 9G, 9H, 9I ₁ 9J in the direction of the arrows 1 OA, 10B, 10C, 10D, 10E in a closed circuit, whose practical structure will be explained in connection with figure 7.

Inside the housing 11 , two sets of barriers 12A, 12B 12C, 12D and 12E, 12F, 12G, 12H may be, but are not necessarily, arranged at two opposed sides of the housing, as also shown in figure 2, so that the barriers of the one set are spaced from the barriers of other set, whereby current in the liquid may be transferred between the electrodes 3.

In order to ensure that the liquid gets the greatest possible pumping effect, the housing 11 and the barriers 12A, 12B, 12C, 12D and 12E, 12F, 12G, 12H are made of an insulating or slightly conducting electrical material, which means that the current between the electrodes, shown at 13A, 13B, 13C, 13D, 13E, will run in the liquid under an optimal magnetic influence.

Instead of providing the housing with barriers, these may be replaced by constrictions in the form of notches configured in the housing, as shown in figure 4, said constrictions being designated 13A, 13B, 13C, 13D, 13E, 13F, 13G and 13H. This results in a simpler structure of the housing in terms of manufacture.

Hereby, the air present in the notches will serve as an insulator.

Finally, the embodiments shown in figures 2 and 4 may be modified by inserting current conductors between the barriers or the constrictions. This is illustrated in figure 5, which shows current conductors 14A, 14B, 14C, 14D, which are inserted in the embodiment shown in figure 4.

With reference now to figures 6A - 6C, it will be explained how the current will run between the electrodes in an electromagnetic pump.

Figure 6A shows the current course of an electromagnetic pump having a housing without barriers or notches, while figure 6B shows the current course if two barriers or two notches are inserted into the housing (these two embodiments are not shown in the drawing), while figure 6C shows the basic current courses of the embodiments shown in figures 2 - 4, where four barriers or four notches are inserted into the housing.

As will be seen, the current course with four barriers or constrictions will ensure that the greatest possible amount of current will run centrally under the magnet of the electromagnetic pump, which, in turn, ensures the greatest flow through the electromagnetic pump.

With reference now to figure 7, it will be explained how the electromagnetic pump is included in a setup for the cooling of an electrical component.

The pipes 9A, 9B, 9C, 9D and 9E recur in the figure, which, as will be seen, are connected with the housing 11 , which, in turn, is connected with the pipes 9F, 9G, 9H, 9I ₁ 9J, which are connected with a cooling plate 18 and a heat exchanger 16, with a microprocessor, an IC circuit or the like 17 mounted on top of the cooling plate 18.

The figure also shows the electrodes 3, 3A as well as the magnet 5, which, as explained before, provides the flow in the liquid which is cooled by the heat exchanger 14.