Patent Publication Number: US-2006005946-A1

Title: Arrangement and method for increasing heat transfer

Description:
FIELD OF THE INVENTION  
      The invention relates in general to an arrangement and method for cooling a heat source and more particularly to an arrangement comprising a power source.  
      Furthermore, the invention relates to software adapted to perform a method for cooling a heat source when executed on a computer.  
      Even further, the invention relates to the use of such a system.  
     BACKGROUND OF THE INVENTION  
      Today, cooling techniques are widely used for cooling heated objects or heat sources such as electronic components, CPUs, etc. At least two different techniques are used for the purpose of transferring heat from a heat source.  
      Corona or ion wind cooling techniques refer essentially to the movement of gas induced by collisions between ions away from the vicinity of a high voltage discharge electrode and the surrounding volume of gas. In ion wind cooling systems a wind is created, which is similar to that created by a fan.  
      Another cooling technique is described in U.S. Pat. No. 3,872,917. In U.S. Pat. No. 3,872,917 there is depicted how a flow of ionized air from a sharp high voltage electrode to a grounded heat source is created. The ionized air flows towards the heat source and creates a forced convection effect similar to that of a fan.  
      When the ionized air comes into contact with the heat source it may deposit particles onto the heat source. This effect is known as the black-wall effect and is a common problem found in air ionizers, where after a short period of time there is a residue build up on the collector electrode. This residue build up will act as thermal insulation, and severely limit the heat transfer co-efficient over a short period of time.  
      The ionized air becomes neutralised as it comes into contact with the grounded heat source and this results in an exiting flow of neutralised air molecules that carry heat away from the heat source in a random direction. This disadvantageously creates a multitude of design problems.  
      Further, the system according to U.S. Pat. No. 3,872,917 is difficult to employ in real applications, such as electronics cooling, because of non-containment of electric fields, increased space requirements, and complex positioning of components to make sure that ionized air flow to the heat source and not to any other component by accident.  
      Furthermore, the system according to U.S. Pat. No. 3,872,917 suffers from the disadvantage of metal emission that occurs at sharp points on high voltage electrodes, which requires unneeded maintenance of the system.  
     SUMMARY OF THE INVENTION  
      One aspect of the present invention relates to the problem of improving heat transfer from a heat source. More particularly, according to an aspect of the invention, the present invention relates to the problem of improving heat transfer from a heat source in a cost effective way.  
      This problem is solved by an arrangement comprising at least one heat source being adapted to transfer heat to at least one first element, a power source being provided for applying a first voltage to said first element, at least one second element having a second voltage, wherein an electric field, generated by a potential difference, between the first element and the second element, causes an ionized medium, heated by the first element, to move towards the second element, thereby achieving an increased heat transfer from the first element.  
      This solution effectively eliminates dust and particle collection on the heat source being cooled and can therefore prolong the cooling efficiency of the arrangement. The arrangement is thus self cleaning. This provides the positive effect that objects, such as components, which are cooled, are not negatively influenced by a polluted environment. Furthermore, as a synergy effect, the arrangement reduces or eliminates the build up of heat on surrounding components.  
      The arrangement advantageously provides uniform cooling over a surface area of the first element. This reduces hot spots and decreases thermal stresses on the heat source being cooled.  
      Advantageously, low cost materials are used, which together with low energy consumption provides a cost effective method for improving heat transfer from the heat source. Furthermore, the construction of the arrangement is simple and easy to implement into production lines. The arrangement requires low to no maintenance and also has longevity.  
      The arrangement can be utilized so that the movement of the ionized medium causes repulsion of a thermal boundary layer on a surface of the first element, thereby further increasing the heat transfer from the first element.  
      Another advantage of the present invention is the flexibility of the arrangement&#39;s design. It can be manufactured to cool small micro-processors and can also be used in large industrial cooling applications, including all shapes and sizes in between, including the cooling of irregularly-shaped surfaces. If, for example, fans are used in large or complex applications, multiple fans are required, increasing design complexity and causing an associated increase in production time and cost.  
      The arrangement can further be configured so that a control unit is arranged to control the potential difference between the first and second element, increasing heat transfer from the first element.  
      Preferably said the arrangement further comprises a dielectric element. Preferably said first element is electrically conductive.  
      Preferably the first voltage is applied to the first element, and the first element is separated from the heat source by the dielectric element.  
      Preferably the heat source is provided with a conductive protection element provided between the heat source and the dielectric element.  
      Preferably the second element is arranged so that the heat transfer is performed in a controlled way, in at least one particular direction.  
      Preferably the second element is grounded.  
      Preferably the applied first voltage is in the range of 1-100 kV.  
      Preferably the arrangement further comprises a control unit arranged for communication with the power supply and/or the second element, wherein the control unit is arranged to control the potential difference between the first element and the second element.  
      The arrangement is silent when used, which is preferable, for example, in areas where people live or work.  
      The arrangement can easily be integrated into existing cooling applications, which use, for example, a fan for cooling a heat source. It can further operate independently or be integrated into existing cooling applications. In fact, a previously-provided fan can be used for transporting an ionized heated medium from the surface of the first element. Even further, a medium being partly ionized can be supplied to the surface of the first element where it is heated and thereafter transferred from said surface, thereby enhancing efficiency of the heat transfer from the heat source.  
      According to one embodiment the heat transfer can be accurately regulated. This is particularly advantageous when the arrangement according to the invention is applied to systems where the heat source is sensitive for temperature variations.  
      According to one aspect of the invention the high voltage potential applied to the heat source, combined with the force of the electric field, causes electrons thermionic emission to occur at relatively low temperatures of the heat source.  
      Advantageously no black-wall effect occurs on the heat source, because ionized air is not flowing towards the heat source.  
      Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following details, as well as by practice of the invention. While the invention is described below, it should be understood that the invention is not limited to the specific details disclosed. The above-mentioned skilled persons having access to the teachings herein will recognise additional applications, modifications and embodiments in other fields, which are within the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of the present invention and further objects and advantages thereof, reference is now made to the following description of examples—as shown in the accompanying drawings, in which:  
       FIG. 1  schematically illustrates a cross-section view of an arrangement for heat transfer according to an aspect of the invention.  
       FIG. 2  illustrates an arrangement for cooling a heat source according to an aspect of the invention.  
       FIG. 3  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 4  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 5  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 6  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 7  illustrates an arrangement for removing heat from at least heat source according to an aspect of the invention.  
       FIG. 8  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 9  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 10  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 11  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 12  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 13  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 14  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 15  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 16  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 17  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 18  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 19  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 20  illustrates an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 21  is a graph illustrating cooling efficiency of an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 22  is a graph illustrating cooling efficiency of an arrangement for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 23   a  illustrates a flow chart of a method for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 23   b  illustrates a flow chart of a method for increasing heat transfer from a heat source according to an aspect of the invention.  
       FIG. 24  illustrates an apparatus according to an aspect of the invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       FIG. 1  schematically illustrates a cross-section view of an arrangement for heat transfer according to an aspect of the invention.  
      A heat source  140  is thermally coupled to a first element  110 . A dielectric element  120  is provided with the first element  110  on a first side thereof. The dielectric element  120  is provided with a third element  130  on a second side thereof. The dielectric element is provided between the heat source  140  and the first element  110 . The third element  130  is thermally coupled to the heat source  140 .  
      According to one embodiment the first element  110  is a conductive layer, which is provided on at least a part of the first side of the dielectric element  120 . The first element  110  is electrically conductive. The first element  110  is a metal, alloy or an electrically conductive material, such as stainless steel, conductive paint comprising for example silver Ag, cast iron, Al, Zn or other. The first element  110  can be attached to the dielectric element by means of spray coating, sputtering, moulding, stamping, plating, brazing, metallization, welding, thermal glue or other. The dielectric element  120  is arranged to transfer heat from the heat source  140  to the first element  110 . The dielectric element  120  is also arranged to insulate the heat source  140  from the high voltage applied to the first element  110 .  
      The dielectric element  120  is provided with the third element  130  on at least a portion of the second side thereof. The third element  130  is electrically conductive. The third element  130  may have the same composition as the first element  110 . The third element  130  can be attached to the dielectric element by means of spray coating, sputtering, moulding, stamping, welding, thermal glue or other. The dielectric element  120  is a solid, such as glass, dielectric refrigerant, plastic or an oxide of various metals, e.g. aluminium oxide. Alternatively the dielectric element is a combination of any dielectric materials. Alternatively, the dielectric element comprises a liquid or gas, such as dry air or distilled water, flourinert liquid or mineral or synthetic oil.  
      The dielectric material, according to an embodiment of the invention, is composed of a ceramic material like Aluminium Nitride, Aluminium Oxide, Boron Nitride, Magnesium Oxide, or Silicon Nitride.  
      Alternatively, the dielectric material, according to another embodiment of the invention, is composed of a compound comprising material of good thermal conductivity and a material of low electric conductivity, such as Boron Nitride powder mixed with polyester or epoxy.  
      The dielectric element can be a diamond wafer. The dielectric element may consist of composites like Diamond/Copper or Diamond/Silicon.  
      The heat source  140 , the third element  130 , the dielectric element  120  and the first element  110  are arranged for heat transfer from the heat source  140  to the first element  110  via the third element  130  and the dielectric element  120 .  
      A second element  150  is provided at a distance D from an assembly comprising parts  110 ,  120 ,  130  and  140 . D is a length between the first element and the second element  150 . The distance D may be chosen with reference to a specific application, in which a method according to the invention is to be used. The distance D between the first element  110  and the second element  150  is preferably slightly greater than that at which arching would occur for a particular potential difference V 1 −V 2  between the first element  110  and the second element  150 . According to one embodiment the distance D is 1 cm. According to another embodiment the distance D is variable between 0.5 and 5 cm. It should however be noted that the second element  150  is separated from the assembly comprising parts  110 ,  120 ,  130  and  140 . In particular the second part  150  is separated from the first element  110 . Alternatively, the second part  150  is a portion of an earthed enclosure, which is described below with reference to  FIG. 17 .  
      According to one embodiment the second element  150  is rotating around at least one axis. The second element can be a wheel or a conveyor belt. According to another embodiment the heat source is rotating around at least one axis. According to one embodiment the second element  150  is one or more wires.  
      According to on embodiment the second element  150  is grounded. The third element  130  is also grounded.  
      Dimensions and sizes of the heat source  140  and the elements with reference to  110 ,  120 ,  130  and  150  may vary within wide ranges. For example, the heat source  140  and the elements depicted with reference to  110 ,  120 ,  130  and  150  may be plate shaped, as illustrated with reference to  FIG. 1 , for illustrative purposes, wherein the elements  130 , 120  and  110  are piled on the heat source  140 . According to another embodiment the elements are block shaped or cylindrical, or a combination thereof. The elements may be irregularly shaped. Depending upon which application the arrangement is provided for a unique design may be applied.  
      A power source  100  is connected to the first element  110  via a wire  50 . Alternatively a line  50  can be used. The power source  100  is adapted to provide a direct current high voltage V 1  to the first element  110 . Alternatively the power source  100  is adapted to provide a direct current high pulse voltage to the first element  110 . The power source  100  is, according to one embodiment, a low amperage power source.  
      The power source  100  comprises a current limiter, which is a short-circuit protection device that automatically limits the current to a safe value. This is done when a current-limiting transistor senses an increase in load current. At this time the current-limiting transistor decreases the voltage on the base of a pass transistor in a regulator, causing a decrease in its conduction.  
      The applied voltage V 1  is provided so as to ionize a medium provided between the first element  110  and the second element  150 . In particular a part of the medium is ionized at the first element  110 . More in particular, a part of the medium is ionized within the thermal boundary layer provided at the surface of the first element  110 . A part of the medium is ionized within a laminar layer of the thermal boundary layer provided at the surface of the first element  110 . This will be described in further detail below.  
      The medium can be any medium which can be ionized between the first element  110  and the second element  150  and thereby be transported within the electric field in a direction away from the first element  110 . Preferably the medium is air.  
      A first sensor  101  is adapted for communication with a control unit  160  via a line  51 . The first sensor  101  is a temperature sensor adapted to measure a temperature T 1  of the heat source  140 . Alternatively the first sensor  101  is adapted to indirectly measure temperature T 1  at the third layer  130 . This is an indicative measurement of the actual temperature T 1  of the heat source  140 . The first sensor is adapted to communicate the measured value T 1  to the control unit  100 .  
      A second sensor  102  is adapted for communication with a control unit  160  via a line  52 . The second sensor  102  is a volume flow sensor adapted to measure a volume flow of the medium provided between the first element  110  and the second element  150 . Alternatively the second sensor  102  is adapted to detect mass flow of the medium provided between the first element  110  and the second element  150 . Alternatively the second sensor  102  is a temperature sensor adapted to measure a temperature T 2  of the medium. The temperature T 2  of the medium is an indirect indication of a temperature of the heat source  140 . The second sensor is adapted to communicate a measured value of a quantity or quality, as described above, to the control unit  160  via the line  52 . One quantity can be pressure. By measuring the pressure P between the first element  110  and the second element  150 , an indication of a corresponding mass flow or volume flow can be calculated. The calculation can be performed in the control unit  160 . According to one embodiment the second sensor  102  is arranged to measure a speed of the medium being transferred from the first element  110  towards the second element  150 .  
      As mentioned the third element  130  is grounded. The purpose of this is to protect the heat source  140  from possible capacitive discharge or static discharge within the arrangement.  
      The dielectric element  120  is adapted to serve as a barrier between the electrically conductive first element  110  and the heat source  140 , so as to protect the heat source  140  from possible corona discharge.  
      The heat source  140  can be any of a variety of different objects. For instance, according to one embodiment of the invention, the heat source is a central processing unit (CPU) or a chip provided in any apparatus, e.g. a computer, such as a micro-computer or a stationary PC or a laptop, CD player, DVD-player, TV, video player (such as VHS), game pad, multimedia box, or other stationary, portable or hand held devices.  
      The heat source can be a condenser, capacitor, or radiator, either in the sphere of industry or in everyday situations. The heat source can be part of a Peltier element. The heat source can be provided by a heat pipe or a plurality of heat pipes as will be described in further detail below. The heat source  140  can be a thermosyphon or a condenser in a water cooling system.  
      The heat source  140  can be provided in a heat pump, freezer, refrigerator, microwave oven, thermo-electrical refrigerator, or projector, such as an overhead, slide, or digital projector.  
      The heat source  140  can be used in cellular phone applications or within a radio base station, telephone switchboard, telephone exchange or teletype exchange.  
      Furthermore, the heat source  140  may be integrated in an air conditioning system, e.g. in a house, airplane or automobile.  
      Alternatively, the heat source is an electronic component such as a resistance, bobbin or iron core coil.  
      Alternatively, the heat source is an engine. Alternatively, the heat source is provided in a brake system in, for example, an automobile.  
      Alternatively, the heat source is a part of a resistor element used for heating a surrounding medium.  
      The power source  100  is arranged to provide the voltage Vito the first element  110 . The voltage V 1  is in the range of 1-100 kV. According to one embodiment V 1  is in the range 10-50 kV. According to another embodiment V 1  is in the range 30-40 kV.  
      Herein it is described that the elements  130  and  150 , respectively, are set to ground. An alternative term for ground is earth. The ground can be a specified, by a user chosen voltage. Ground preferably has a voltage of 0V. The voltage applied to the second element is a voltage V 2 . According to one embodiment V 2  is equal to 0V. According to another embodiment V 2  is equal to +5V. According to yet another embodiment V 2  is equal to −5V. According to yet another embodiment V 2  varies in the range between −100V to +100V. According to one embodiment the voltage V 2  is controllable by the control unit  160 .  
      The control unit  160  is adapted to control the power source  100  via a line  55 . The control unit  160  is arranged to control the power source  100  in dependence of a first signal S 1 . The control unit  160  is arranged to control the power source  100  in dependence of a second signal S 2 . Alternatively, the control unit  160  is arranged to control the power source  100  in dependence of both the first signal S 1  and the second signal S 2 . The control unit  160  is arranged to control the applied voltage provided between the first element  110  and the second element  150  in a predetermined way. For example the control unit  160  is arranged to regulate the heat transfer from the first element  110 . This can be made in various ways. One way is to transfer heat from the first element  110  to keep the temperature T 1  of the heat source at a constant level, for example 50 degrees Celsius, or 100 degrees Celsius.  
      With reference to  FIGS. 2-20  alternative arrangements of the present invention are described. The arrangements can be used in combinations for specific applications and are thus not limited to schematic illustrations as indicated in said figures.  
      A process of transferring heat from the heat source  140  to the first element  110  and/or from the first element to the ambient medium is known as cooling or heat transfer.  
      As high voltage is applied to the first element  110  from the high voltage power source  100 , there is a direct injection of free charges into the ambient medium, known as ionization. Furthermore, the ambient medium that is in direct contact with the first element  110  becomes ionized, causing the laminar thermal boundary layer surrounding the first element  110  to become ionized and, consequently repelled, by coulombic forces, away from the first element. This results in a disturbance of the lower laminar thermal boundary located directly at the surface of the first element  110 , thereby improving heat transfer since no protecting laminar thermal boundary layer is provided.  
       FIG. 2  illustrates an embodiment of an arrangement for cooling a heat source according to an aspect of the invention.  FIG. 2  illustrates an alternative assembly of the arrangement illustrated in  FIG. 1 . Here no grounded electrically conductive layer  130  is provided. The heat source  140  is grounded.  
      The second element  150 , according to this embodiment, is provided with a coating  152 , which functions as a catalyst. According to this embodiment the catalyst is gold (Au). Alternatively the catalyst can comprise Silver (Ag), Platinum (Pt) or Manganese Dioxide (MnO 2 ).  
      The coating  152  may alternatively be composed of Activated Carbon coatings, Manganese Oxide, Iodonium or Titanium Dioxide.  
      The coating  152  is provided on the second element  150  so as to reduce an amount of ozone created within the electric field E, for example in a case where the medium is air. The ozone created in the electric field E is moved towards the second element  150 , and thereby the coating  152 , by the ionized medium. At least a part of the ozone is converted to oxygen by the catalyst.  
      According to this embodiment the heat source  140  and the second element  150  are set to the same ground.  
       FIG. 3  illustrates an embodiment of an arrangement for cooling a heat source according to an aspect of the invention.  
      This arrangement is similar to the system presented in  FIG. 1 . However, the first element  110  on the first side of the dielectric medium  120  is provided with elongated elements  300 . The elongated elements  300  have an elongated shape. The elongated elements  300  are attached to the first element  110  at one end thereof. The pin elements can be pin-like or needle-like. The elongated elements  300  can either form part of the first element  110  by being integrated moulded, or being fixedly secured to the layer  110  by, for example, a welding process. Preferably the elongated members are composed of essentially the same material as the layer  110 .  
      The elongated elements  300  are oriented perpendicular to the first surface of the first element  110 . A length axis of the elongated elements  300 , respectively, is aligned with a direction pointing towards the second element  150  from the first element  110 .  
      A configuration of the elongated elements  300  may vary. For example one elongated element  300  per square cm is provided on the first element  110 . The configuration of the elongated elements  300  may be tailored.  
      It should be noted that a surface structure of the first element  110  may vary. For example, it can be roughened or contain holes. Alternatively, considering the elongated elements provided on the first element  110 , elements having a semi-spherical shape can be attached to the first element  110 , wherein a flat section thereof is attached to the surface of the first element  110 .  
      According to one embodiment the first element  110  is a heat sink. A heat sink structure makes it is possible to transfer more heat from the first element  110 . An increased heat dissipation of its surface, by virtue of the fact that there is an increased surface area, is enabled.  
      The second element  150  may be provided with elongated elements  302 . The elongated elements  302  may essentially be equivalent to the elongated elements  300 . The size of both the elements  300  and  302 , respectively, may not be uniform but vary some. The elongated elements  302  are attached to the second element  150  in a way similar to how the elongated elements  300  are attached to the first element  110 .  
      It should be noted that a surface structure of the second element  150  may vary. For example, it can be roughened or contain holes  153 . According to one embodiment the holes are through holes. According to one embodiment the second element is provided with a plurality of apertures. Two holes  153  are illustrated in the figure.  
      The through holes are adapted to lead the moving medium from one side of the second element  150  to another side of the second element  150 . Thereby the heated medium is transferred away from the heat source  140 .  
       FIG. 4  illustrates an embodiment of an arrangement for cooling a heat source according to an aspect of the invention.  
      An arrangement with reference to  FIG. 4  illustrates a fan which is provided so as to achieve a positive synergy effect of different aspects of heat transfer, namely to increase movement of the ionized heated medium towards the second element  150  from the first element  110 .  
      As illustrated in the figure the second element  150  is provided in a vicinity of the first element  110  at a first side thereof. The fan  460  is provided at a second side of the first element  110 .  
       FIG. 5  illustrates an embodiment of an arrangement for cooling of a heat source according to an aspect of the invention.  
      The fan  460  is arranged to move the ionized heated medium from the first element  110  through holes provided in the second element  150  (not shown) by having a rotating direction enabling increased heat transfer from the first element  110 .  
      Now referring to  FIG. 6 , which illustrates an alternative embodiment of an arrangement for removing heat from a heat source according to an aspect of the invention, the fan  460  causes an increased transfer of the ionized heated medium from the first element  110  towards the second element  150 , through the holes provided therein and away from the second element  150 .  
       FIG. 7  illustrates an embodiment of an arrangement for removing heat from at least heat source according to an aspect of the invention.  
      According to this embodiment of the invention a plurality of heat sources  140   a ,  140   b  and  140   c  are provided. It should be noted that the heat source  140   c  is not in physical contact with the third element as depicted with reference to for example  FIG. 1 . Heat is transferred via convection or radiation from the heat source  140   c  to the third element  130  and the dielectric layer, and thus to the first element  110 , via a medium provided around the heat source  140   c.    
      According to one embodiment the arrangement comprises 10 heat sources  140   a - j  (not shown), which are cooled off according to the present invention.  
       FIG. 8  illustrates an embodiment of an arrangement for removing heat from at least one heat source according to an aspect of the invention.  
      The arrangement comprises a plurality of heat sources  140   a - c  and two first element  110   a  and  110   b . The power source  100  is arranged to provide a voltage Via to the first element  110   a  via a wire  50   a . The power source  100  is arranged to provide a voltage V 1   b  to the first element  110   b  via a wire  50   b.    
      According to one embodiment of the voltages Via and V 1   b  are equal. According to another embodiment the voltages Via and V 1   b  are mutually different. According to yet another embodiment the voltages Via and V 1   b  are independently controlled by the controller  160  (not shown) by means of the power source  100 .  
       FIG. 9  illustrates the embodiment of an arrangement for removing heat from several heat sources according to an embodiment of the invention.  
      Herein three heat sources  140   a - c  are to be cooled. The dielectric element  120  is provided with two first elements  110   a  and  110   b  connected to the power source  100  via wire  50   a  and  50   b , respectively. Two second elements  150   a  and  150   b  are provided. The power source  100  is adapted to apply a second voltage V 2   a  to the second element  150   a  via a line  152   a . The power source  100  is adapted to apply a second voltage V 2   b  to the second element  150   b  via a line  152   b . The power source  100  is adapted to apply a first voltage Via to the first element  110   a  via the line  50   a . The power source  100  is adapted to apply a first voltage V 1   b  to the first element  110   b  via the line  50   b.    
      The control unit  160  is arranged to control the power source  100  via the wire  55 . The control unit is arranged to control the first voltages V 1   a , V 1   b  and the second voltages V 2   a , V 2   b . The control of the voltages V 1   a , V 1   b , V 2   a  and V 2   b  can be performed simultaneously. The control of the voltages V 1   a , V 1   b , V 2   a  and V 2   b  can be performed independently of each other. The control of the voltages V 1   a , V 1   b , V 2   a  and V 2   b  can be performed in dependence of measured information, such as a temperature T 4  measured at the first element  110   a  by a temperature sensor  104 . The temperature sensor  104  is adapted for communication with the control unit  160  by a line  54 .  
      Thus, the control unit  160  can control heat transfer from the first elements  110   a  and  110   b  towards the second elements  150   a  and  150   b  by controlling the power source  100  to apply the voltages Via, V 1   b , V 2   a  and V 2   b  as described above.  
       FIG. 10  illustrates the embodiment of an arrangement for removing heat from a heat source according to an embodiment of the invention.  
      Two additional second elements  150   c  and  150   d  are provided on the dielectric element  120 . The elements  150   c  and  150   d  are grounded. The heat source  140  is grounded. The elements  150   c  and  150   d  are provided so as to direct a flow of the ionized medium in specific directions and thus serve as a complement to the second element  150 . According to one embodiment the second elements  150   c  and  150   d  are elongated.  
      According to one embodiment the element  150   c  and  150   d  are replaced by a cylinder  150   e  (not shown) provided around the first element  110 . The cylinder  150   e  is provided on the dielectric element  120 .  
       FIG. 11  illustrates the embodiment of an arrangement for removing heat from a heat source with reference to  FIG. 1 .  
      Herein an illustration of the electric field is shown. As can be seen the electric field E according to this embodiment is essentially homogeneous between the first element  110  and the second element  150 .  
      In contrast,  FIG. 12  illustrates an embodiment of an arrangement for removing heat from a heat source according to an aspect of the invention wherein an in-homogeneous electric field E is generated between the first element  110  and the second element  150  by applying a high voltage to the first element  110 , while the second element  150  is earthed. Herein the second element  150  is relatively small in size compared with the first element  110 . According to this embodiment the second element  150  is elongated or needle-shaped.  
       FIG. 13  illustrates an embodiment of an arrangement for transferring heat from a heat source according to an aspect of the invention.  
      A heat pipe  170  is attached to the heat source  140  at a first end thereof. The heat pipe is earthed. The heat pipe is arranged to transfer heat, which heat is provided from the heat source. The heat pipe  170  is arranged to transfer heat from the first end to a second end. At the second end of the heat pipe the dielectric element  120  is provided. The first element  110  is in conductive contact with the dielectric element  120 . The first element  110  is a heat sink.  
      The second element  150  is forming an earthen enclosure around the first element  110 . The second element is preferably provided with a plurality of through holes. When applying a high voltage V 1  to the first element  110  by means of the power source  100  a movement of the ionized medium heated by the first element  110  is created. The heated ionized medium moves towards the second element and creates a volume flow through the holes in the second medium  150 , thereby transferring heat from the first element  110 .  
       FIG. 14  illustrates an embodiment of an arrangement for removing heat from a heat source according to an aspect of the invention.  
      The heat pipe  170  is thermally coupled to the heat source  140  at a first end thereof. The heat pipe is earthed. The heat pipe  170  is arranged to transfer heat from the first end, which heat is provided from the heat source, to a second end thereof according to a commonly known operation. At the second end of the heat pipe the dielectric element  120  is provided. The first element  110  is in thermal contact with the dielectric element  120 . According to one embodiment the first element  110  is a plate.  
       FIG. 15  illustrates an embodiment of an arrangement for removing heat from a heat source according to an aspect of the invention.  
      The dielectric element  175  and a dielectric fluid provided inside the heat pipe will serve as an insulator protecting against arching from the first element  110  and the heat source  140 .  
      The arrangement is essentially identical to the arrangement with reference to  FIG. 13 . However, the heat pipe  170  is provided with a dielectric element  175 . The heat pipe provided with the dielectric element  175  is depicted in greater detail below. The dielectric element  120  is not provided.  
       FIG. 16  schematically illustrates a heat pipe provided with a the first element  110  according to an aspect of the invention.  
      The heat pipe  170  is arranged to transfer heat from the heat source  140  (not shown) from a first end to a second end thereof. The second end is provided with the first element  110 . The can be manufactured out of a conductive material such as Cupper Cu. The first element  110  can be a heat sink.  
      A dielectric element  175  is arranged between the first and second end of the heat pipe  
       FIG. 17  illustrates an embodiment of an arrangement for removing heat from a heat source according to an aspect of the invention.  
      The dielectric medium  120  is thermally coupled to the third element  130 . The third element  130  is earthed. The third element  130  is formed as a closure open in one end, as shown in the figure. Alternatively the third element  130  is a closure comprising the depicted parts but the heat source  140 . The heat source  110  is in thermal contact with one side of the third element  130 , which is analogue to the teachings with reference to figures described above. The first element  110  has a triangular shape seen in a cross-sectional view. The first element  110  is a cone. Alternatively, the first element  110  is a tetrahedron. Alternatively, the first element  110  is a spherical triangle. Alternatively, the first element  110  is a frustum of right cone.  
      The second element  150  is provided with a flange and is forming a cap. The second element  150  is provided with a plurality of through holes (not shown). The flange is composed of a dielectric material. The medium runs through the arrangement along a helically configured path, as can be seen in the figure. The medium is heated and ionized as described above and further transferred towards the second element  150 .  
       FIG. 18  illustrates an arrangement for transferring heat from a heat source according to an aspect of the invention.  
      Three distanced elongated elements  300   a ,  300   b  and  300   c  are provided on the first element  110 , thereby creating separated electric fields E 1 , E 2  and E 3  respectively, when the first voltage V 1  is applied to the first element  110 .  
       FIG. 19  illustrates an arrangement for transferring heat from a heat source according to an aspect of the invention.  
      A similar set up of the arrangement as depicted with reference to  FIG. 17  is shown in  FIG. 20 . However, the medium has a flow directed from a base of the first element, along the surface of the first element  110 , towards the second element  150 . The ionization of the medium, as well as heat transfer from the first element  110  to the medium, takes place on or at the surface of the first element  110 .  
      Herein the first element  110  is a prism. Alternatively, the first element is an elongated element having a triangular cross section area.  
       FIG. 20  illustrates an arrangement for transferring heat from a heat source according to an aspect of the invention.  
      The arrangement illustrated in  FIG. 20  is essentially the same as the arrangement with reference to  FIG. 19 . However, the arrangement according to  FIG. 20  is provided with an inlet pipe  250  adapted to lead the medium through the third element  130  towards the first element  110 . Furthermore, the arrangement is provided with an outlet pipe  251  fixedly secured to the second element  150  at one end, which outlet pipe is adapted to lead the medium away from the second element  150 .  
      Alternatively, the outlet pipe  251  and the inlet pipe  250  are detachable arranged.  
       FIG. 21  illustrates two graphs NC 1  and A 1  indicating how the temperature T of the heat source varies per unit time t during cooling, according to one embodiment. It should be noted that cooling efficiency hereby disclosed are examples for illustrative purposes only. The graphs plot test data collected for two different cooling methods under essentially the same conditions, which is, for example, constant heating of the heat source  140  during cooling. The ambient temperature was 23° C. The applied voltage is 30 kV, ground potential is 0V. The temperature T of the heat source was measured as a function of time t.  
      A first graph NC 1  illustrates the case of natural convection. The temperature of the heat source stabilizes at a temperature T 2  after t 2  minutes.  
      A second graph A 1  illustrates the case of cooling according to an embodiment of the present invention ( FIG. 1 ). The temperature of the heated object stabilizes, or levels out, at a temperature T 1  after t 1  minutes. Here, an amount of cooling of the heat source  140  is essentially equal an amount of heat provided to the heat source  140 .  
      In this particular case T 1  is approximately 46 degrees Celsius and T 2  is approximately 147 degrees Celsius. In this particular case t 1  is approximately 7 minutes and t 2  is approximately 35 minutes.  
      It should be noted that different efficiencies may be achieved under other conditions, i.e. when applying a higher voltage V 1  to the first element  110 .  
       FIG. 22  illustrates cooling efficiency according to a test performed with reference to the set up according to  FIG. 1 . More particularly,  FIG. 22  illustrates two graphs NC 2  and A 2  indicating how the temperature T 1  of the heat source  140  varies per unit time t during cooling. In this test the heat source  140  was heated to 150 degrees Celsius and thereafter cooled using natural convection (NC 2 ). A second test was performed (graph A 2 ) under essentially the same conditions but using the cooling method.  
      The temperature of the heat source stabilizes at a temperature T 1  after t 2  minutes.  
      A second graph A 2  illustrates the case of cooling according to an embodiment of the present invention. The temperature of the heated object stabilizes, or levels out, at the temperature T 1  after t 1  minutes.  
      In this particular case, T 0  is 150 degrees Celsius, T 1  is about 35 degrees Celsius, t 1  is about 7 minutes, and t 2  is about 35 minutes.  
       FIG. 23   a  schematically illustrates a method according to an embodiment of the invention. The method starts, then performs the step s 230 , and thereafter ends.  
      The method step s 230  for improving heat transfer from at least one heat source in an arrangement comprising at least one first element and at least one second element; wherein said heat source is adapted to transfer heat to said first element; said method comprising the step of: 
          controlling heat transfer from the first element by applying an electric field between said first and second element.        

      According to one embodiment of the invention the method further comprises the step of: 
          controlling said heat transfer is performed in a predetermined way so that a movement of ionized medium, heated by the first element, causes a thermal boundary layer provided on a surface of the first element to be repelled off, and thereby further increase the heat transfer from the first element.        

      According to another embodiment of the invention the method further comprises the steps of 
          receiving a first signal comprising information about the heat transfer from the heat source, and     controlling said heat transfer in dependence of said first signal.        

      According to yet another embodiment of the invention the method comprises the step of 
          controlling said heat transfer by controlling said first or second provided voltage.        

       FIG. 23   b  illustrates a flowchart for removing heat from an object according to an aspect of the invention.  
      According to a first method step s 233  the first voltage V 1  is applied to the first element  110  and the second voltage V 2  is applied to the second element  150 . Next, a method step  235  follows.  
      In method step  235  at least one temperature measurement is detected indicating the temperature of the heat source  140 . Next, a method step  240  follows.  
      The method step  240  includes a choice of adjusting the applied voltages V 1  and V 2  or not. A decision is made in dependence of the temperature measurement according to step s 235 . If yes, a method step  245  follows. If no, a method step  250  follows.  
      The method step  245  includes adjustment of the applied voltages V 1  and V 2 . Next, the method step  250  follows.  
      The method step  250  includes a choice of interrupting the method. If yes, the method ends. If no, the method step s 235  follows.  
      With reference to  FIG. 24 , a diagram of one way of embodying an apparatus  700  is shown. The above-mentioned control unit  160  may include the apparatus  700 . The apparatus  700  comprises a non-volatile memory  720 , a data processing device  730  and a read/write memory  740 . The memory  720  has a first memory portion  750  wherein a computer program, such as an operating system, is stored for controlling the function of the apparatus  700 . Further, the apparatus  700  comprises a bus controller, a serial communication port, I/O-means, an A/D-converter, a time date entry and transmission unit, an event counter and an interrupt controller (not shown).  
      The data processing device  730  may be embodied by, for example, a microprocessor.  
      The memory  720  also has a second memory portion  760 . The program may be stored in an executable manner or in a compressed state.  
      When it is described that the data processing device  730  performs a certain function it should be understood that the data processing device  730  performs a certain part of the program which is stored in the memory  760  or a certain part of the program which is stored in the recording medium  762 .  
      The data processing device  730  may communicate with a data port  799  by means of a data bus  783 . The memory  720  is adapted for communication with the data bus  783  via data bus  785 . The separate non-volatile recording medium  762  is adapted to communicate with the data processing device  730  via data bus  789 . The read/write memory  740  is adapted to communicate with the data bus  783  via a data bus  785 .  
      Parts of the methods described with reference to  FIGS. 23   a  and  23   b  can be performed by the apparatus  700  by means of the data processing device  730  running the program stored in the memory portion  760 . When the apparatus  700  runs the program, parts of the method described with reference to  FIG. 23   a  and/or  FIG. 23   b  are executed.  
      When data is received on the data port  799  said input data is temporarily stored in the read/write memory  740 . When the received input data has been temporarily stored, the data processing device is set up to perform execution of code in a manner described above. According to one embodiment, data received on the data port  799  comprises information about heat transfer from the heat source. This information can be used by the apparatus  700  so as to control the applied voltage V 1  and/or V 2 , which controls heat transfer from the heat source  140 .  
      Induced flows in a dielectric fluid provided between the grounded heat source  140  and the element  110   
      According to one embodiment of the invention a dielectric fluid is provided between the heat source and the element  110 . Thereby an increased heat transfer between the heat source  140  and the element  110  is achieved. By applying a high voltage to the element  110  an irregular electric field is generated between the grounded heat source  140  and the underside of the heat exchanger. Thereby regions of unequal field intensities causing a flow in the dielectric fluid are created.  
      Therefore, the dielectric fluid does not only acts as an insulating barrier, but also acts as a means to efficiently transfer heat to the heat exchanger without mechanical means, such as a pump.  
      Use of a dielectric fluid is particularly useful in applications involving cooling of a microchip or the like, since there today is an urgent need to spread the heat efficiently away from such a small surface area.  
      According to one embodiment of the invention, by using a dielectric enclosure between the heat exchanger and the heat source, there is created a strong flow within the fluid using electrohydrodynamic forces, which causes one or several means of creating motion within fluids. Thereby heat can be spread more efficiently away from the heat source by creating a turbulent motion in the dielectric fluid.  
      Application of a high voltage to the element  110  provided on the heat source  140  provides the synergy effect that there is created a fluid motion between the element  110  and the heat source  140 , while increased heat transfer from the element  110  is achieved.  
      One example of an application may be in the design of a peltier element where the ceramic plates may be replaced by using a dielectric fluid as insulating medium between the thermopiles and the underside of a heat exchanger. When high voltage is applied to the heat exchanger a motion can be generated in the dielectric medium to enhance heat transfer to the heat exchanger and then also to the grounded collector electrode.  
      Another example may be that of a heat source which may be located at some distance to the heat exchanger. The heat exchanger may be located at some distance away from the heat source for a number of reasons including, but not limited to, space requirements. Here a flow is generated in the dielectric liquid to transport heat effectively from the heat source to the heat exchanger. The heat exchanger has a high voltage applied to it and not only creates a flow in the dielectric element barrier but also increased heat transfer from the heat exchanger to the ambient air.  
      The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated.