WO2010133227A2

WO2010133227A2 - A pump housing for an electromagnetic pump

Info

Publication number: WO2010133227A2
Application number: PCT/DK2010/000064
Authority: WO
Inventors: Martin Kloster; Morten Espersen
Original assignee: Danamics Aps
Priority date: 2009-05-19
Filing date: 2010-05-19
Publication date: 2010-11-25
Also published as: DK200900637A; WO2010133227A3

Abstract

When a pump housing for an electromagnetic pump for the propulsion of a conductive liquid in a cooling circuit, in particular for the cooling of electrical components, said pump housing comprising an upper part and a lower part which assembled constitute a pump chamber having an internal surface, said lower part being provided with openings for pipes for the cooling circuit, said openings pointing inwards to the pump chamber, said pump housing being additionally provided with two openings for electrodes, said electrodes pointing inwards to the pump chamber and being arranged on opposed sides of the pump housing and being equipped with electrodes (8), is improved to the extent that the internal surface (5) of the pump chamber (4) is provided with a coating (10) having electrically insulating properties, it is ensured that the electrical scattering losses are reduced significantly. When, additionally, electrodes having a low transition resistance and being capable of ensuring a good contact face to the conductive cooling liquid are provided, electrical losses in electrodes and in the body of the pump housing may advantageously be reduced.

Description

A PUMP HOUSING FOR AN ELECTROMAGNETIC PUMP

The present invention relates to a pump housing for an electromagnetic pump for the propulsion of a conductive liquid in a cooling circuit, in par- ticular for the cooling of electronic components, said pump housing comprising an upper part and a lower part which assembled constitute a pump chamber having an internal surface, said lower part being provided with openings for pipes for the cooling circuit, said openings pointing inwards to the pump chamber, said pump housing being additional provided with two openings for electrodes, said openings pointing inwards to the pump chamber and being arranged on opposed sides of the pump chamber and being equipped with electrodes.

The prior art

The applicant's Danish Patent Application No. PA 2008 01351 discloses a pump housing for an electromagnetic pump for pumping a cooling liquid in a closed circuit for the cooling of electronic components. The application describes a pump housing which is basically configured in the same man- ner as the pump housing of the present application. The openings for the cooling pipes are disposed at opposed ends on the lower side of the base part of the pump housing. This position has been selected so as to achieve a simplified production and mounting of the electromagnetic pump. At the same time, a good distance from the electrodes and out to the pipes is achieved, so that the resistance in the body of the pump housing is increased, which reduces the power loss slightly.

One of the drawbacks of this structure is that there is still a relatively high power loss, so that the pump loads the power supply inexpediently much.

Measurements on the pump have shown that there is a great power loss, as a portion of the current follows other paths than the desired one. The current paths have been found to extend from the electrodes partly through the pump housing out to the pipe connections, partly through the conductive cooling liquid out to the pipe connections and directly between the electrodes. Only the latter current path is desirable.

Another drawback is that the transition resistance from the electrodes to the conductive liquid is relatively great because of the small diameter of the electrodes.

The object of the invention

It is the object of the invention to improve a pump housing for an electromagnetic pump of the type stated in the opening paragraph, so that the electrical current paths which do not contribute to driving or maintaining the liquid flow are reduced as much as possible.

It is a further object of the invention to provide electrodes which have a low transition resistance, and which are additionally capable of ensuring a good contact face to the conductive cooling liquid and a linear current travel between the electrodes.

Summary of the invention

The objects stated above are achieved by a pump housing as described in the introductory portion of claim 1 , which is characterized in that the end of the electrodes facing inwards toward the pump chamber is equipped with a pole shoe which extends into the pump chamber and into the conductive liquid, thereby ensuring that the contact area between the electrode and the conductive liquid in the pump chamber is increased, whereby the transition resistance between the electrode and the liquid is reduced. When, as stated in claim 2, the pole shoe is configured as a fork having one or more leaf-shaped prongs, and the width of the prongs decreases toward the free ends of the prongs, it is ensured that the contact area between the pole shoe and the conductive liquid is increased additionally, and that the electrodes extend further into the pump chamber so that a greater part of the current may be guided more directly between the electrodes, which results in a smaller scattering loss.

When, as stated in claim 3, the surface of the pole shoe is polished so as to be completely smooth, a further improvement of the contact conditions between the liquid and the pole shoe is achieved.

When, as stated in claim 4, the outer pipe and the central conductor are equipped with a soldered joint at the end which faces away from the open- ing, the resistance between the central conductor and the body of the pump chamber is advantageously increased.

As stated in claim 5 and claim 6, it is moreover expedient that the outer pipe and the central conductor are configured with a circular cross-section, and that the outer pipe is made of stainless steel, and that the central conductor is made of copper.

The drawing

Exemplary embodiments of the invention will be explained more fully below with reference to the drawing, in which:

fig. 1 shows a pump housing with an exposed pump chamber in perspective,

fig. 2 shows a section through a pump housing, seen from the side, fig. 2a shows a section through an alternatively embodied pump housing, seen from the side,

fig. 3 shows a replacement diagram which describes the current paths in a pump housing,

fig. 4 shows a replacement diagram which describes the current paths in an improved pump housing,

fig. 5 shows the structure of an electrode equipped with a pole shoe,

fig. 6 shows the pole shoe seen from the side, and

fig. 7 shows the basic current path between electrodes having pole shoes.

Detailed description of the invention

The improvements of a pump housing according to the invention are shown in figures 1 - 7.

Fig. 1 shows the lower part 2 of a pump housing 1 of stainless steel having an exposed pump chamber 4, where the barriers 9 and a portion of the internal surface 5 of the pump chamber are visible. Further, it is shown that the openings 7 for the electrodes 8 are arranged on the side of the lower part. The electrodes 8 are copper conductors, and they are not shown.

Fig. 2 shows a section through the pump housing 1 , seen from the side. It is shown that the lower part 2 and the upper part 3 are assembled, and that they form a pump chamber 4. The openings 6 for cooling pipes are shown arranged on the lower side of opposed ends of the lower part, and an opening 7 for an electrode is shown. A coating 10 of metal oxide has been applied to the internal surface 5 of the pump chamber 4. The internal surface 5 does not only comprise the boundaries of the chamber, but also the surface on the barriers 9.

Fig. 2a shows a section through an alternatively embodied pump housing 1. It is shown here that the lower part 2 and the upper part 3 are assembled, and that they form a pump chamber 4. The openings 6 for cooling pipes are shown arranged on the lower side of opposed ends of the lower part. Fur- ther, it is shown that the openings 7 for the electrodes are arranged on the upper part 3 together with the barriers 9. A coating 10 of metal oxide has been applied to the internal surface 5 of the pump chamber 4.

Fig. 3 shows a replacement diagram, which illustrates the current paths and the current losses in a pump housing without insulating coatings, lsp represents the scattering current at the inlet and the outlet of the pump chamber, If represents the current in the liquid between the electrodes 8, and Ig represents the current in the body of the pump housing. Rsp represents the resistance for the scattering current, Rf represents the resistance in the liquid, and Rg represents the resistance through the body of the pump housing.

Only If generates propulsion in the liquid, lsp is undesired, because it does not contribute to propulsion or, at worst, causes complex forces and pres- sure conditions which counteract the propulsion. Ig, too, is a considerable source of loss.

E represents the induced electromotive voltage, which is generated when the current-conductive liquid in motion passes the magnetic field in the pump chamber. The induced electromotive voltage is normally expressed by E = B^*L^*v, wherein B is the field strength of the magnetic field, L is the length between the electrodes in the direction of the current, and v is the velocity of the liquid. Measurements have shown that, in practice, E is a function of a pump constant multiplied by the total current which is fed to the pump. Thus, it is a factor which gains increasing importance at high liquid flow rates and high magnetic fields.

Since the strength of the magnetic field B depends on the size of the air gap in the magnetic circuit, and the pump chamber is disposed in the air gap, the field strength B also depends on the height of the pump chamber. Therefore, it might be an advantage to reduce the height of the pump chamber so that the air gap would be smaller, since the force driving the liquid is determined by F = B^*L^*I.

However, an increase of the magnetic field also has drawbacks, since the induced electromotive voltage E increases with the result that the current If is reduced. The same effect may be observed at high liquid velocities and to a smaller degree at an increase of the width of the pump chamber.

Therefore, the present pump housing structure puts a limit on how high liquid velocities and magnetic fields may be realized for a given width of the pump housing. If the optimal geometrical configuration of the pump chamber and the magnetic field is exceeded, then the current If driving the liquid is reduced by the voltage E, so that the propulsion of the liquid is also reduced.

A number of other electric and magnetic phenomena, such as e.g. Hall effect, upstream electron drifting and phase shifting, also affect the function of the pump, but to a smaller degree. In a reasonably adapted geometrical design of the present pump housing, the current distribution in the current paths will be as follows:

If = 20% lsp = 40%

Ig = 40%.

This distribution, however, is not very optimal. It would be desirable to reduce the currents lsp and Ig relative to If in order to thereby achieve a more expedient current load of the power supply. One of the improvements in order to solve the above-mentioned problems is that the pump chamber 4 has been coated with a metal oxide 10.

Useful metal oxides are aluminium oxide (AI2O3), zirconium oxide (ZrO2) or yttrium oxide (Y2O3), all of which have electrically insulating properties, and which are resistant to heat and corrosive liquids. The metal oxides also lend themselves to being applied by known industrial methods.

The insulating coating in the pump chamber reduces lsp to a significant degree. For the current losses to be reduced additionally, Ig has to be reduced. This may be done best by increasing Rg significantly inter alia by establishing a great resistance between the electrodes and the body of the pump housing.

A solution is to make a joint between electrode and pump housing with a non-conductive material. This may be done by coating both the electrodes 8 and the openings 7 for the electrodes with one of the metal oxides and then baking them together at a high temperature. Hereby, Rg in the replacement diagram may be removed completely. However, this solution is complicated and expensive. A preferred solution of increasing Rg, as shown in fig. 5, is to build an electrode 8 concentrically, so that it comprises an outer pipe 11 of stainless steel in which a central conductor 12 of copper coated with a metal oxide is arranged. The outer pipe and the central conductor are joined by a solder 13 at the end which faces away from the pump housing. The electrode 8 may now be joined with the pump housing 1 by a soldered joint 14 between the outer pipe and the pump housing. The resistance in the outer pipe to the walls of the pump housing is considerably greater than the resistance in the central conductor. In a replacement diagram, the resulting resistance will be very great, resulting in a low loss in the body of the pump housing.

The replacement diagram for a pump housing with coating and concentric electrodes is shown in fig. 4. Rsp is now very great, because the internal surfaces of the pump chamber are coated with a metal oxide, and the cur- rent Ig through the body of the pump housing has been reduced significantly by the introduction of the resistances R(E1) and R(E2) originating from the outer pipe 11 of the electrodes.

The configuration of the liquid-touching geometry of the electrodes is of significant importance in an insulated pump chamber, because the part of the current which previously ran through the body and out into the liquid between the electrodes, and which contributed to maintaining a liquid flow, now runs no longer. The transition resistance to the liquid must be reduced in order to compensate for the removal of this current path.

When, as shown in fig. 5, the electrodes 8 are equipped with pole shoes 15 of copper, the contact surface may be increased. The configuration of the pole shoe is important, however, because, in addition to the necessity of increasing the contact face to the liquid, the pole shoe must also contribute to directing the current into the liquid, so that the current will more easily run linearly between the electrodes. Further, it must be configured such that that it does not create barriers or turbulence in the liquid when the liquid passes the pole shoe.

In this connection, it is important that the surface of the pole shoe is smooth, so that, when passing, the liquid obtains a good flowability around and contact to the pole shoe. The surface may be polished so as to be smooth, but it may also be treated with a coating which is smooth and electrically conductive.

When, as shown in fig. 6 and fig. 7, the pole shoe 15 is configured as a fork having one or more leaf-shaped prongs 16, and the prongs are configured such that the width of the prongs decreases toward the free ends of the prongs, not only a good contact face is achieved, but barriers and turbulence in the liquid are moreover avoided, and, in addition, it is possible to direct the current If more directly and linearly between the electrodes.

With the stated improvements of the pump housing, a reasonably adapted geometrical design will make it possible to achieve a current distribution as follows:

Ig = 5% lsp = 10% If = 85%.

With this distribution, it is now possible to reduce the total consumption of current significantly without reducing the liquid propulsion by the pump at the same time.

Attempts at additionally increasing the magnetic field strength B, the liquid velocity v or both will cause the induced electromotive voltage E to increase strongly. This increase, however, will counteract the current If and make it escape from the pump chamber and seek out to the connection pipes of the pumps. This creates a new current path for waste. In other words, there is a limit to how flat the pumps may be constructed in spite of the improvements which have been imparted to the pump housing.

Claims

PATENT CLAIMS

1. A pump housing for an electromagnetic pump for the propulsion of a conductive liquid in a cooling circuit, in particular for the cooling of electrical components, said pump housing comprising an upper part and a lower part which together constitute a pump chamber having an internal surface, said lower part being provided with openings for pipes for the cooling circuit, said openings pointing inwards to the pump chamber, said pump housing being additionally provided with two openings for electrodes, said openings pointing inwards to the pump chamber and being arranged on opposed sides of the pump housing and being equipped with electrodes, wherein the internal surface (5) of the pump chamber (4) and the openings (7) for the electrodes are provided with a coating (10) having electrically insulating properties, wherein the electrodes (8) are constructed concentrically and comprise an outer pipe (11) which surrounds a central conductor (12), and wherein a coating (10) having electrically insulating properties is arranged between the outer pipe and the central conductor, characterized in that the end of the electrodes (8) facing inwards toward the pump chamber (4) is equipped with a pole shoe (15) which extends into the pump chamber and into the conductive liquid flowing through the pump chamber.

2. A pump housing according to claim 1 , characterized in that the pole shoe (15) is made of copper and is configured as a fork having one or more leaf-shaped prongs (16), and that the width of the prongs decreases toward the free ends of the prongs.

3. A pump housing according to claims 1 - 2, characterized in that the surface of the pole shoe (15) is polished or has an electrically conductive coating applied thereto.

4. A pump housing according to claim 1 , characterized in that the outer pipe (11) and the central conductor (12) are equipped with a soldered joint (13) at the end which faces away from the opening (7).

5. A pump housing according to claim 1 or 4, characterized in that the outer pipe (11) and the central conductor (12) are configured with a circular cross-section.

6. A pump housing according to claim 1 , 4 or 5, characterized in that the outer pipe (11) is made of stainless steel, and that the central conductor (12) is made of copper.