WO2007112763A1

WO2007112763A1 - Method and apparatus for cooling and ventilation

Info

Publication number: WO2007112763A1
Application number: PCT/EP2006/003014
Authority: WO
Inventors: Anna BORGSTRÖM; Roderick Barrett
Original assignee: Aureola Swedish Engineering Ab
Priority date: 2006-04-03
Filing date: 2006-04-03
Publication date: 2007-10-11

Abstract

The invention provides a silent cooling method and apparatus for transporting and ventilating air in an electronic enclosure, wherein a first (11 ; 21; 31; 41) electrode, with a substantially smaller leading surface, and a second (13; 23; 33; 43) electrode are placed at a distance from each other. A high voltage difference between the two electrodes forms an intense inhomogeneous electric field. Air close to the second electrode (13; 23; 33; 43) will become ionized and be set in motion by the inhomogeneous electric field. This will cause an overall movement of air in the direction of the inhomogeneous electric field and the invention will act as a suction fan, drawing out heated air from within the enclosure.

Description

Method and apparatas for eøoIlMg and wafilafioin

Technical field

The present invention relates to a silent cooling method and apparatus utilizing ion wind for transportation and ventilation of air in an enclosure, such as computers, servers, laptops, TV's etc.

In electronic enclosures such as that of personal computers, laptops, servers, flat screen televisions, industrial and medical electronic enclosures etc., there is a constant need to expel warm air that is generated by various components inside the enclosure. Without sufficient expulsion of the warm air from an electronic enclosure, the increased thermal loads on various components, sensitive to excessive heat, may result in failure of these components. It is also advantageous to be able to direct cooler air from outside an enclosure to within the enclosure.

Fans are traditionally used for expelling warm air inside an electronic enclosure, but there are a number of reasons why fans, in most cases, are undesired. This includes excessive noise, vibration and erratic useful life lengths. Often, the only way to reduce the need for a fan is to utilise designs that maximise natural convection flow within an enclosure.

An example of this could be an electronic enclosure that is designed to have air vents at the base and top of the enclosure. The heated air inside the enclosure will rise because of natural convection, simply described as a buoyancy effect which causes warm air to rise. As this warm air flows up and exits the enclosure at the top, cooler air Is drawn in from the base of the enclosure. These designs, however, Iiave a relatively low efficiency. There is also a need to be able to expel air from an enclosure through various geometries of air vents of the enclosure. For example, there may be a long rectangular air vent where a fan will not be able to expel air through the entire area of the air vent.

In the prior art there are techniques that use what is commonly known as the "corona" or "ion wind" effect, which essentially relates to the movement of air by a combination of ionization and the use of an inhomogenβous electric field, for the purpose of transporting or ventilating air. These techniques have primarily been in- tended for removing warm air away from around a heat source.

As described in US 3,699,387, when a needle or a wire/wires shaped emitter electrode is connected to a high voltage source and placed at a certain distance from a substantially larger grounded collector electrode, e.g. a conducting surface area, a high intensity inhomogeneous electrical field is formed between the emitter and the collector electrode.

The electrical field intensity will diverge from high intensity at the emitter electrode to a lower intensity at the collector electrode. The high potential gradient, which will be higher at the sharp surface of the needle or wire than elsewhere, will cause charge to gather on this sharp surface and develop a corona that will start to ionize air molecules in its vicinity making them conductive.

When the charged particles in the air and around the corona are subjected to the electrical field they will be attracted to and start drifting towards the grounded col- lector electrode, where they will discharge and neutralize.

As the air ions move towards the collector electrode they will cause an overall movement of air in the same direction. This air flow is referred to as "ion wind" or "corona- wind". Using ion wind techniques in practical applications has proven difficult for a number of reasons.

One of the reasons is that during the ionization at the emitter electrode with high electric field intensity there will also be a significant amount of metal emission from the sharp surface edge of the emitter electrode, which will start to degrade the emitter electrode and will after a short period of time have worn down the sharp surface area rendering the device practically useless and in need of maintenance. Although various materials can slightly prolong the useful life of a sharp emitter electrode, the useful life length is still sufficiently short to render the device imprac- tical for most commercial applications.

Another reason is that when a corona forms on the emitter electrode it also often contributes to electromagnetic interference and the emission of ozone and other toxic pollutants. A disturbing noise, like a hissing or spitting sound, can also be heard when a corona is formed. This is because the distance between the two electrodes is often designed to be just beyond the distance at which break-down or arching of the two electrodes occurs in order to maximize the efficiency of the airflow. The removal of the corona requires either a reduction of the voltage potential between the electrodes or that the distance between them is increased. However, when the corona is removed the air flow dramatically reduces.

Further, as described in US 5,982,102, when trying to implement an ion wind system, for example, in an electronics application, the system would have to be shielded by an electrically conductive casing in order to protect other sensitive equipment in the application. However, by doing so it could lead to the attraction of the ionized air by the conductive casing, and thus dragging the air flow from its desired direction. An object of the present invention is to provide a durable and effective ion wind machine with an largely extended useful life length, which can generate and control air flow within an electronic enclosure and expel warm air from within the enclosure to outside of the enclosure or draw in cool air from outside the enclosure to within the enclosure, and hereby lowering the air temperature within the enclosure.

The object of the present invention is achieved by providing a cooling apparatus for transporting and ventilating air in an electronic enclosure comprising at least a first and a second electrode placed at a distance from each other, wherein the first electrode has a substantially smaller leading surface than the second electrode and there is a voltage difference between the two electrodes causing air to flow in a direction from the first electrode to the second electrode.

The first electrode is connected to a ground source arid the second electrode is connected to a power source arranged to provide a high voltage potential to the second electrode in such a way that a intense inhomogeneous electrical field is formed di- verging from the first to the second electrode.

By not having the ionization occurring at the high electric field intensity, as described in the prior art, but instead at a lower intensity level at the substantially larger conductive surface area, the previously troublesome effect of metal emission on the emitter electrode is almost entirely eliminated. This means that the present invention can operate for a significantly longer period of time in comparison to the prior art.

Corona can now also be eliminated without impacting negativsϊy on the efficiency of the air flow. Therefore the present invention can be easier to implement in a sea- sitive electronic application by generating limited electromagnetic interference and resulting in a silent ventilation system. Another benefit of the elimination of the corona is that practically no ozone or other toxic pollutants is emitted.

The first electrode may comprise a needle, a wire, a blade, an arrangement of wires or any other suitable form as long as it has a substantially smaller leading surface then the second electrode. The second electrode may comprise a conductive wire mesh, grid or other electrically conductive material having a shape with a substantially larger leading surface then the first electrode and that allows air to pass through or around it.

Preferably the apparatus is provided with a power source that is arranged to apply a positive or negative voltage having a magnitude of between 3 kV and 40 kV and a low current output of around 50 μA to 1 mA to the second electrode.

Preferably the electrodes may be fastened to non-conductive dielectric frame, which may be encased in a grounded conductive, metal box with ventilation holes for air flow, wherein said grounded conductive, metal box may be coated with insulation. This can shield surrounding objects from electrical fields generated from the appara- tus without affecting the performance of the apparatus in a negative way.

Alternatively, a third electrode may be provided to form a subsequent guiding electric field between the second electrode and the third electrode, on the opposite side of the second electrode relative to the first electrode. This third electrode may be a part of a grounded, outer metal shielding (e.g. a computer chassis) or form part of a heat exchanger surface.

Preferably the dimensions of the apparatus conform to standard fan bracket dimensions used for electronic cooling and ventilation. The object of the invention is further achieved by using a method for transporting and ventilating air in an electronic enclosure, using an apparatus comprising a first and second electrode placed at a distance from each other, wherein the first electrode has a substantially smaller leading surface than the second electrode and there is a voltage difference between the two electrodes, said method being characterized by the step of providing a voltage to at least one of said first and second electrode in such a way as to form an intense inhornogeneous electric field diverging from the first to the second electrode.

Preferably the method also comprises the step of controlling said transportation and ventilation of air in an electronic enclosure by regulating the voltage potential levels of at least one of said first and second electrode.

Preferably the method further comprises the step of receiving a signal comprising information about the air from the electronic enclosure, and the step of regulating the voltage potential levels of at least one of said first and second electrode in dependence of said received signal.

The object of the invention is further achieved by using a computer programme product for use in a control unit for controlling an apparatus comprising a first and second electrode placed at a distance from each other, wherein the first electrode has a substantially smaller leading surface than the second electrode and there is a voltage difference between the two electrodes, which comprises computer readable code means, which when run in the control unit causes the control unit to control the voltage of at least one of said first and second electrode in such a way as to form an intense inhomogeneous electric field diverging from the first to the second εlec-

the computer programme product also comprises control means for eon- iroiilng the voltage potential levels of at least aoe of said first and second electrode Preferably the computer programme pfoduet further comprises code means for receiving a signal comprising information about the air from an electronic enclosure and controlling the voltage potential levels of at least one of said first and second electrode in dependence of said signal.

Preferably the computer programme product comprises code means which is stored on a readable storage medium.

Brief description of the drawings

Fig. 1 shows a schematic view of an ion wind machine according to the present invention.

Fig. 2 shows a view of an embodiment of the present invention.

Fig. 3 shows a view of an embodiment of the present invention.

Fig. 4a-b shows an embodiment of the present invention with the electrodes fastened to a non-conductive frame and inserted in a conductive, metal box.

Fig. 5 shows the conductive, metal box with ventilation holes for air flow.

Fig. 6 shows the present invention inserted in a standard computer chassis.

Fig. 7 shows an apparatus according to the present invention inserted in an electronic enclosure.

Fig. 3 shows two apparatuses according to the present invention inserted in an electronic enclosure. §

Fig. 9 shows two apparatuses according to the present invention inserted in an electronic enclosure, positioned so as to working in synergy with the natural convection.

Fig. 10 shows an apparatus according to the present invention inserted in an elec- tronic enclosure, between an air vent and a heat exchanger.

Fig. 11 shows an apparatus according to the present invention inserted in an electronic enclosure_^ positioned on the side of a heat exchanger opposite an air vent.

Fig. 12 shows two apparatuses according to the present invention inserted in an electronic enclosure, one positioned between an air vent and a heat exchanger and the second one positioned on the side of the heat exchanger opposite the air vent

Fig. 13 shows an apparatus according to the present invention positioned on the out- side of an electronic enclosure, facing an air vent close to a heat exchanger.

Fig. 14 shows two apparatuses according to the present invention, one positioned on the outside of an electronic enclosure, facing an air vent close to a heat exchanger and the second one inserted on the opposite side in the electronic enclosure.

Fig. 15 shows an apparatus according to the present invention inserted in an electronic enclosure and a heat attachment from an inside heat source to an outside heat exchanger.

Fig. 1 illustrates a first embodiment demonstrating the ion wind technique according to the present invention. The embodiment includes an air duct 12 and two electrodes 11 and 13, The first electrode is a needle 11, positioned in the air duel: 12 and at a distance from, as well as pointing in the direction of, the second electrode, which is a substantially larger conductive surface area 13, such as a mesh or a grid, spanning across the entire cross-sectional area of the air duct 12. The needle 11 is connected to a ground source and the substantially larger conductive mesh 13 is connected to a high voltage power source 15.

When a high voltage is applied to the substantially larger conductive mesh 13, a high intensity electrical field is formed around the sharp point 18 of the grounded needle 11, which will diverge towards the high voltage mesh 13. Ionization will occur at the high voltage mesh 13, developing a cloud of ions, which will envelope the high voltage mesh 13. Most of the ions will develop in the inho- mogeneous electric field 14 in the air around the high voltage mesh 13 on the side facing the needle 11.

Because of the diverging inhomogeneous electric field 14 between the grounded needle 11 and the high voltage mesh 13, the ionized air will be moved by an elec- trophoretic effect from the region of high intensity to a region of low intensity, causing an overall movement of air in the direction 17 from the needle 11 electrode to the high voltage mesh 13. The invention can be said to work as a suction fan.

Fig. 2 illustrates a second embodiment of the present invention. In this embodiment the first electrode consist of a thin wire 21, stretching across an air duct 22, and positioned at a distance from the second electrode, which is a substantially larger conductive wire mesh 23, lying flat across, and perpendicular to the cross-section of the air duct 22. The wire electrode 21 is connected to a ground source and the substan- tially larger flat conductive mesh 23 electrode is connected to a high voltage power source 2§,

'Mien a high voltage is applied to the substantially larger flat conductive mesh 23 , the ionization and the inhomogeneous electric field, as described earlier in the first embodiment, will cause an overall movement of air in the direction 27 from the wire electrode 21 to the hisfo voltage mesh 23. With this arrangement it is possible to design a very thin ventilation device for use in, for example, a small electronic enclosure, such as a desktop computer.

Fig. 3 illustrates a third embodiment of the present invention. In this embodiment the first electrode consist of a wire mesh 31, spanning across the entire cross- sectional area of an air duct 32, and positioned at a distance from the second electrode, which is also a conductive wire mesh 33, spanning across the entire cross- sectional area of the air duct 32. The spacing, however, between the wire elements of the first electrode are substantially larger than the spacing of the wire elements of the second electrode.

The wire mesh electrode 31 is connected to a ground source and the substantially smaller spaced wire mesh 33 electrode is connected to a high voltage power source 35. Also, a regulation system 36, as described in the following, is connected to the high voltage power source 35. When a high voltage is applied to the substantially smaller spaced wire mesh 33, the ionization and the inhomogeneous electric field, as described earlier in the first embodiment, will cause an overall movement of air in the direction 37 from the wire mesh electrode 31 to the high voltage, smaller spaced wire mesh 33.

Fig. 4a-fo illustrates a fourth embodiment of the present invention. In this embodiment the first electrode consist of a thin wire 41, stretching across an air duct 42, and positioned at a distance from the second electrode, which is a substantially larger conductive mesh 43, spanning across the entire cross-sectional area of the air duct 42. The thin wire electrode 41 is connected to a ground source and the substantially larger conductive mesh 43 electrode is connected to a high voltage power source 45. Also, a third grounded electrode 4§ may be present just outside the open end of the air duct 42 parallel to and positioned behind the conductive mesh 43 electrode, relative to the thin wire electrode 41. Ia this case, the third electrode 4© is a part of an outer metal shielding. When a high voltage is applied to the substantially larger conductive mesh 43, the ionization and the inhomogeneous electric field, as described earlier in the first embodiment, will cause an overall movement of air in the direction 47 from the thin wire electrode 41 to the high voltage conductive mesh 43.

Additionally, if a third grounded electrode 4§ is present, a homogeneous electric field 44 will form between the conductive mesh 43 electrode and the third grounded electrode 4CJ₅ on the opposite side of the conductive mesh 43 electrode relative to the thin wire electrode 41 and can help attract the ionized air from the conductive mesh 43 electrode in a controlled direction.

A third grounded electrode 40 can of course in a similar way be arranged to provide a subsequent homogeneous electric field 44 in all of the described embodiments.

In Fig. 4b the thin wire electrode 41 and the substantially larger, conductive mesh 43 electrode are encased in and fastened to a non-conductive frame 46, i.e. a dielectric housing, preferably made of plastic, and inserted in a conductive, metal box 50 also shown in Fig. S.

The conductive, metal box 50 will have holes for ventilation 59 in both of the opposite sides extending across the air duct 42 in Fig. 4a-b, so the air can flow freely through the box, from one side to another. It will also be coated in an electrically insulating material and connected to a ground source (not shown), e.g. the same grounding as the thin wire electrode 41 in Fig. 4a, or perhaps to the chassis of a computer in which the ventilation device may be provided. This way of shielding the apparatus from outside electronic interference, as well as protecting the outside electronic components from the electromagnetic field generated on the inside, is of course applicable to all of the described embodiments. Further, one of the sides of the conductive, metal box 5© extending across the air duct 42 in Fig. 4a-Ib>, can be arranged to provide the third electrode, as described in the previous embodiment. In Fig. 6 the ion wind air flow unit 6§ can be seen inserted in an electronic enclosure, in this case inside a standard computer chassis 69. The warm air generated by various components inside the computer will be transported in the direction 67 from the inside of the enclosure to the outside surroundings. The dimensions of the ion wind air flow unit 60 can of course be adapted to fit inside a multitude of different enclosures, such as laptops, servers, flat screen televisions, industrial and medical electronic enclosures etc.

In all embodiments, the outer metal shielding surrounding the conductive, metal box, e.g. the chassis of a computer or a simple protective casing, can be coated with a catalyst, which can react with and degrade any potential ozone that may be produced under extreme conditions and convert at least a part of the ozone into oxygen. Example of catalysts may include, but are not limited to, Gold (Au), Silver (Ag)₅ Platinum (Pt) and Manganese Dioxide (MnO 2). The coating may alternatively be composed of Activated Carbon coatings, Manganese Oxide, Iodonium or Titanium Dioxide.

It should be pointed out that hazardous levels of ozone emission does not occur during normal operating conditions and that the catalyst coating is to been seen rather as a safety precaution which can provide emergency treatment of ozone if ever for some reason it is produced.

The outer metal shielding can also provide for a homogeneous electric field between the high voltage mesh on the inside of the insulated, conductive box and its grounded shielding on the outside. This can aid in guiding the air flow from the inside to the outside of the electronic enclosure and also help in limiting ionized air from flowing directly into the enclosure, which is an important aspect since this could disrupt and interfere with other electronic components.

The preferred voltage applied to the grid or mesh in the above mentioned embodiments is a positive or negative -/oltage høviαg a magnitude of between. 3 IcV io 40 .-.Y &aά a low current 3iapυi of arouod 50 μA to 1 mA, depending on the she of the air flow device. The ground source in the above mentioned embodiments can be separated from the grounding of the high voltage power source, see below.

There are countless of way to vary the size, shape and form of the cooling apparatus of the present invention, it could be made thin, long, rectangular, circular etc. all depending on the electronic enclosure into which it is to be implemented. Although the dimensions of the casing preferably conform to standard fan bracket dimensions, i.e. 60 mm x 60 mm, 80 mm x 80 mm, 120 mm x 120 mm, this is not intended to be construed in a limiting sense.

The present invention can also be seen as to incorporate a system comprising several of these ion wind air flow units, where all of them share the same high voltage power supply or have separate high voltage power supplies. These power sources, whether joined in one or separate, can be equipped with a regulation system, as the one shown in Fig. 3, to control the potential difference between the electrodes in order to prevent break-down or arching and provide further safety mechanisms rendering the system safe to touch.

The regulation system can also be used to monitor different variables such as humidity and temperature and adjust the voltage potential accordingly. It could, for ex- ample, be implemented in the form of a computer programme running in a processing unit of the regulation system.

It should be noted that, although only shown in Fig. 3, the regulation system is of course applicable to all embodiments of the described embodiments.

In the detailed description above it is described that the first electrode is set to ground. Aa alternative term for ground is earth.

The ground can be specified by a user chosen voltage, although a voltage of OV is often preferred. This means that the voltage applied to the first electrode in the present invention can, in one case, be equal to OV and in other cases be equal to +5V, -5V or even vary in the range of between -100V to +100V. ϊt can also be controllable by the regulation control system, which adjusts the poten- tial difference between the two electrodes.

Fig. 7 illustrates an air flow device 71 according to the present invention inserted at an air vent 73 in an electronic enclosure 7S and used to draw in cooler air from outside the enclosure 75 to within the enclosure 75, as indicated by arrows. In most cases the ionized air can be sufficiently neutralized by a third electrode, as previously described, so as to not impact negatively on electrically sensitive components within the enclosure.

Fig. 8 illustrates two air flow devices 81-82 according to the present invention in- serted at air vents 83-84 in an electronic enclosure 85 and used to draw in cooler air from outside the enclosure 85 to within the enclosure 85, as well as, either direct or expel warm air from within the enclosure 85 to outside the enclosure 85, as indicated by arrows.

Fig. 9 illustrates two air flow devices 91-92 according to the present invention inserted at air vents 93-94 in an electronic enclosure 95, positioned so as to work in synergy with the natural convection within the enclosure 95.

Cooler outside air can be directed into the enclosure 95 near the base and heated air can be directed out of the enclosure 95 near the top, as indicated by arrows, thereby enhancing the existing natural convection flow of heated air 99 within the enclosure

FIg. 1© illustrates an air flow device Iδ'l according to the present invention inserted at an air vent 1(0)3 in an electronic enclosure IiS₉ positioned on one side of a heat exchanger 107, connected, to a heat source 10¹S, so as to create a suction of heated sir surrounding the heat exchanger 107 in a direction outside the enclosure 1⁽0)5, as indicated by arrows.

An air flow device 111 could also be, as illustrated in Fig. 11, positioned on the side of a beat exchanger 117, connected to a heat source 116, opposite to the air vent

113 of the enclosure 115, so as to push the heated air from the heat exchanger 117 to outside the enclosure 11 S, as indicated by arrows.

Air flow devices 121-122 could further, as illustrated in Fig. 12, be positioned, on both sides of a heat exchanger 127, connected to a heat source 126, to both suck and push heated air surrounding the heat exchanger 127 to outside the enclosure 12S₅ as indicated by arrows.

In the cases involving a heat exchanger, there would be a heat source such as a CPU, or other electronic component adapted to transfer heat to the heat exchanger. The heat source can be adapted to transfer heat to the heat exchanger via direct contact, one or more heat-pipes, a heat spreader, a vapour system, a liquid pumped system, or a thermosyphon type system.

The heat exchanger surface would preferably be grounded, for example to the chassis. Preferably, the heat exchanger surface could also be used as the third electrode, as previously described.

Fig. 13 illustrates an air flow device 131 according to the present invention posi- tioned at an air vent 133 of an electronic enclosure 135 and on one side of a heat exchanger 137, and used to draw in and direct cooler air from outside the enclosure 13S towards the heat exchanger 157 within the enclosure OS. Additionally, as illustrated in FIg. 14, it could, in this case, also be advantageous to lisve a second ak flow device 141 according to the present invention, positioned In such a way so as to expel heated air within the enclosure 145 to a direction outside the enclosure 145.

Fig. 15 illustrates an air flow device 151 according to the present invention inserted at an air vent 153 in an electronic enclosure 155 and used to expel warm air from within the enclosure to outside the enclosure, as indicated by arrows. A heat source within the enclosure 155 can be adapted to transfer heat to a heat exchanger 157 surface located outside the enclosure ISS. The air flow device 151 could be used to draw heated air from within the enclosure 155 to a direction out- side the enclosure 155, and more specifically in a direction towards a heat exchanger 157 located on the outside of the enclosure 155. The air that is expelled from the enclosure 155 can thus induce a forced convection of airflow onto the heat exchanger 157 surface and increase the cooling of the heat exchanger 157.

Claims

1. An apparatus for transporting and ventilating air in an electronic enclosure comprising at least a first (11 ; 21 ; 31; 41) and a second (13; 23; 33; 43) electrode placed at a distance from each other, wherein the first electrode (11; 21 ; 31 ; 41) has a substantially smaller leading surface than the second electrode (13; 23; 33; 43) and there is a voltage difference between the two electrodes causing air to flow in a direction from the first electrode (11 ; 21; 31; 41) to the second electrode (13; 23; 33; 43),

the first electrode (11; 21; 31; 41) is connected to a ground source, the second electrode (13; 23; 33; 43) is connected to a power source (15; 25; 35; 45) arranged to provide a high voltage potential to the second electrode

(13; 23; 33; 43) in such a way that an intense inhomogeneous electrical field is formed diverging from the first (11; 21; 31; 41) to the second electrode (13; 23; 33; 43) .

2. An apparatus according to claim 1₃ wherein said first electrode (11 ; 21 ; 31 ;

41) comprises a needle, a wire, mesh, blade or an arrangement of wires.

3. An apparatus according to claim I₃ wherein said second electrode (13; 23; 33; 43) comprises a conductive wire mesh, grid or other electrically conduc- tive material having a shape that allows air to pass through or around said second electrode (13; 23; 33; 43).

4. An apparatus according to claim 1-3, wherein the power source is arranged to apply a positive or a negative voltage having a magnitude of between 3 IcV and 40 kV and a low current output of around 50 μA to 1 mA to the second electrode (13; 23; 33; 43).

5. An apparatus according to claim 1-4, wherein the apparatus further comprises an electrically conductive protective housing for shielding surrounding objects from electrical fields generated from the apparatus.

6. An apparatus according to claim 5, wherein said protective housing comprises a non-conductive dielectric frame (46) to which said first (11 ; 21; 31; 41) and second electrode (13; 23; 33; 43) are fastened.

7. An apparatus according to claim 6, wherein said protective housing further comprises a grounded conductive, metal box (50) with ventilation holes (49) for air flow in which said non-conductive dielectric frame (46) is encased.

8. An apparatus according to claim 7, wherein said grounded conductive, metal box (50) is coated with insulation.

9. An apparatus according to claim 1-8, comprising a third electrode (40) ar- ranged to provide a subsequent guiding electric field between the second electrode (13; 23; 33; 43) and the third electrode (40), on the opposite side of the second electrode ( 13 ; 23 ; 33 ; 43) relative to the first electrode ( 11 ; 21 ; 31 ;

41).

10. An apparatus according to claim 9, wherein said third electrode is a part of a grounded, outer metal shielding (e.g. a computer chassis).

11,An₁ apparatus according to any of the previous claims, wherein the dimensions of the apparatus conform to standard fan bracket dimensions.

12. A method for transporting and ventilating air in an electronic enclosure, using an apparatus comprising a first (11; 21; 31 ; 41) and second electrode (13; 23; 33; 43) placed at a distance from each other, wherein the first electrode (11; 21 ; 31 ; 41) has a substantially smaller leading surface than the second electrode (13; 23; 33; 43) and there is a voltage difference between the two electrodes, said method being

the step of providing a voltage to at least one of said first (11; 21; 31; 41) and second electrode (13; 23; 33; 43) in such a way as to form an intense inho- mogeneous electric field diverging from the first (l l; 21; 31; 41) to the second electrode (13; 23; 33; 43).

13. A method according to claim 12, comprising the step of: . controlling said transportation and ventilation of air in an electronic enclosure by regulating the voltage potential levels of at least one of said first (11; 21; 31; 41) and second electrode (13; 23; 33; 43).

14. A method according to claim 12-13, further comprising the steps of:

- receiving a signal comprising information about the air from the electronic enclosure, and

- regulating the voltage potential levels of at least one of said first (11; 21; 31; 41) and second electrode (13; 23; 33; 43) in dependence of said received signal.

15. A computer programme product for use in a control unit for controlling an apparatus comprising a first (11; 21; 31 ; 41) and second electrode (13; 23; 33; 43) placed at a distance from each other, wherein the first electrode (11; 21 ; 31 ; 41 ) has a substantially smaller leading surface than the second elec- trode (13; 23; 33; 43) and there is a voltage difference between the two electrodes, which comprises computer readable code means, which when run in the control unit (36) causes the control unit to control the voltage of at least one of said first (11; 21; 31; 41) and second electrode (13; 23; 33; 43) in such a way as to form an intense inhomogeneous electric field diverging from the first (11; 21; 31; 41) to the second electrode (13; 23; 33; 43).

16. A computer programme product according to claim 15, comprising control means for controlling the voltage potential levels of at least one of said first (11; 21; 31; 41) and second electrode (13; 23; 33; 43).

17. A computer programme product according to any of the claims 15-16, further comprising code means for receiving a signal comprising information about the air from an electronic enclosure and controlling the voltage potential lev- els of at least one of said first (11; 21; 31; 41) and second electrode ( 13 ; 23 ;

33; 43) in dependence of said signal.

18. A computer programme product according any of the claims 15-17, wherein said code means is stored on a readable storage medium.

19. An electronic device comprising at least one unit generating heat

it comprises an apparatus according to any of the claims 1-10 for generating a controlled flow of air from within the enclosure to the outside of the enclosure or vice versa.