GB2026238A

GB2026238A - Cooling apparatus for electrical elements

Info

Publication number: GB2026238A
Application number: GB7925223A
Authority: GB
Original assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Priority date: 1978-07-21
Filing date: 1979-07-19
Publication date: 1980-01-30
Also published as: CA1138562A; BR7904617A; FR2431769B1; FR2431769A1; SE443475B; DE2902771A1; NL7905603A; SE7906190L; ATA428579A; AT383228B

Abstract

A cooling apparatus for high- power semiconductors with fluid cooling, especially for track-bound vehicles or railroads and for generator excitation. The disk-shaped semiconductor elements to be cooled are in pressure contact with metallic cooling elements and are arranged, in conjunction therewith, in flow channels 23. The cooling agent flows through such cooling elements which comprise, perpendicular to their contact surface with the semiconductor elements, head conducting elements in a plug or plate configuration. These heat conducting elements produce a turbulent fluid flow. The cooling element base or floor can have a non-uniform wall thickness. Two substantially identical cooling elements can be in heat conducting contact with one another by means of their heat conducting elements, and a flow conducting plate, arranged between such cooling elements, can be employed as electrical contact. <IMAGE>

Description

SPECIFICATION Cooling apparatus for electrical elements The present invention relates to a cooling apparatus for electrical components, especially semi-conductor elements, of the power electronics art.

Generally speaking, the cooling apparatus comprises at least one assembly or group of structural components containing at least one semiconductor element and at least one cooling element. These elements are operatively connected with one another in mutual, heat conducting and electrical pressure contact, the assembly having a heat absorbing cooling fluid circulating thereabout.

During the operation of semiconductor components or elements, such as for instance high-current diodes and thyristors, electrical power losses arise which lead to temperature increases at the semiconductior body. With increasing power for each semiconductor element and with increasing frequency there is an increase of that electrical power losses which have been converted into heat. It amounts to approximately one percent of the transmitted electrical power. With infrequent overloads manufactures of semiconductor components permit, for instance, barrier layer-temperatures up to 2500C for silicon rectifiers.Prior to destruction such lose their blocking capacility in the forward direction at apprximately 1 60 C. For safety reasons the temperature should not exceed about 125 C. The build-up of heat in the semiconductor is dependent upon the power loss as a function of time and the thermal conductivity or dissipation and heat storage capacbilities of the semiconductor elements.

Cooling agents are employed when working with current intensities exceeding 100 amperes. Both air and also liquid coolants are conventionally utilized.

Liquid cooling systems, owing to the danger of corrosion, are designed to work in a closed circulation system with recooling by untreated water or air.

The semiconductor bodies are in heat conducting relationship with cooling bodies having cooling ribs and formed of aluminium, aluminium alloys, copper or copper alloys or another suitable metal, having a low thermal resistance.

Cooling devices for semiconductor elements are especially used in high-power or high-performance current rectifiers in the field of energy generation, energy distribution, in industrial applications and at vehicles. In this respect, there are employed thyristors having a continuous limiting current of > 700 amperes and a peak blocking voltage of > 3200 volts.

Further developments in current rectifier installations has resulted in the production of current rectifier arrays or groups operating at increasingly greater power and at the same time of more space-saving configuration, there being attained power outputs exceeding 50 MW. Such requires good heat dissipation or conduction within very narrow space requirements.

Air cooling is the simplest type of cooling in terms of preparing and monitoring the cooling agent and the accessibility to the semiconductor components or elements. Such frequently requires air filters which, during periodic serice or maintenance times, must be dismantled, cleaned, dried and again installed. In the case or current rectifiers having power outputs exceeding 2 MW and for the operation of semiconductor elements, for instance in current rectifier banks or arrays at railroad vehicles, requiring special protection against contamination by metallic braking dust and so forth and also against moisture attack from fog, rain and snow, liquid cooling systems can be more suitable than cooling systems.

Since liquids have much smaller heat transfer co-efficients than air, it is possible to get by with much smaller heat transmitting services when using liquid coolers. Water possesses more favourable heat transfer coefficients than, for instance oil. Due to the danger of frost and the electrical conductivity of the water there is preferably employed an electrically insulating coolant, such as transformer oil.

Now in German Patent Publication No. 2,640,000 it is known to employ internally cooled heat transfer elements, so-called cooling cells or cans, having an oil circulation cooling for heat conduction or dissipation. In the flow path of the cooling liquid there are arranged, essentially perpendicular to the cell floors, plugs connected by their or a similar material with such cell floors. These plugs possess a square cross-section and have a diagonal thereof extending transversely with respect to the flow direction. Due to this arrangement of the plug-diagonals transversely with respect to the flow direction turbulance phenomena arises, leading to an improved transfer of the heat which is to be withdrawn from the cell floors to the liquid.Such type cooling cells do however require a relatively high pressure for the liquid circulation, since the openings for the influx and efflux of the cooling liquid have a small cross-section. Sealing problems particularly arise by virtue of the hose connections needed for the liquid infeed and outfeed lines.

In German Patent Publication No. 2,160,997 there is furthermore known to the art to arrange externally cooled, large surface heat transfer elements between neighbouring semiconductor elements in heat conducting relationship and to accommodate such in a liquid container or vessel filled with oil.

In accordance with this invention, there is provided a cooling apparatus for electrical components, especially semiconductor elements of the power electronics art, comprising: at least one group of structural components containing at least one electrical element and at least one cooling element; said elements being in mutual, heat conducting and electrical pressure contact with one another; a heat-absorbing cooling fluid surrounding said structural component group; a flow channel within which there are arranged said electrical element and the cooling element within said heat-absorbing cooling fluid; and said flow channel being surrounded in a surface-like manner by walls or longitudinal partitions.

An embodiment to be described herein comprises a cooling apparatus for semiconductor elements of the power electronics art, possessing a relatively simple construction which is favourable as concerns fabrication economics and rendering possible an improved heat dissipation or removal in relation to heretofore known cooling devices. The semiconductor element and the cooling element are arranged within a heat absorbing cooling fluid in a flow channel and surrounded in an aerial manner by walls or longitudinal partitions of the flow channel.

The cooling fluid or coolant can be gaseous or vaporous, especially can be SF6-gas or a hydrogenair mixture.

A particularly noteworthly advantage of the embodiment of cooling apparatus resides in the fact that the arrangement of the group of structural components containing the cooling and semiconductor elements within the flow channels affords high cooling efficiency both for liquid and also gaseous coolants.With this cooling apparatus it is possible to attain, with liquid cooling, comparatively small thermal resistances of less than 0.03 K/W using aluminium cooling elements and less than 0.02 WW with copper cooling elements, and with air cooling there can be obtained thermal resistances of less than 0.05 We with aluminum cooling elements and less than 0.04 we with copper cooling elements. Afurther advantage of the embodiment is in terms of the fact that within a flow channel there is afforded an improved heat dissipation or conductance from the cooling elements to the cooling fluid.

An advantage of the employed elements, which in their construction are similar to the heretofore known cooling cells or cans, resides in the fact that they do not require any special cooling element encapsulation. Therefore, they are easier and simpler to fabricate than such cooling cells. The inlet and outlet openings for the cooling fluid in the cooling element can be designed to be largerthan with the cooling cells, so that the pressure gradient for each cooling element is smaller. Consequently, the fluid pressure and the power output which must be expended by the circulating pump or ventilator, as the case may be, are smaller. Sealing problems at the cooling elements do not arise, since such are immersed in the fluid or the fluid circulates thereabout.Due to short line paths for the heat which is to be dissipated within the cooling elements there is obtained, within very small space, a high cooling efficiency. A particular advantage of the cooling elements resides in the fact that they can be stacked upon one another. The cooling apparatus does not require special maintenance and, with small space requirements of the group of structural components, ensures for their easy exchangeability and high longevity of service life.

Said embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates in vertical sectional view a cooling apparatus containing a number of groups of structural components containing semiconductor elements and cooling elements within a cooling fluid container; Figure 2 is a horizontal sectional view, according to the sectional line Il-Il of Figure 1, illustrating the principle of a clamping system having two groups of structural components; Figure 3 is a horizontal sectional view, taken substantially along the line Ill-Ill of Figure 2, showing a partitioned cooling element having square heat conduction or dissipation elements, Figure 4 shows a cooling element in sectional view, taken substantially along the line IV-IV of Figure 3;; Figure 5 is a bottom plan view of a cooling element shown in the arrangement of Figures 3 and 4; Figure 6 is a schematic horizontal sectional view of a cooling element having rhomboid heat conduction or dissipation elements; Figure 7 is a sectional view, taken substantially along the line VIl-VIl of Figure 6 of the cooling element thereof; Figures 8 and 9 are respective schematic horizontal sectional views of two further constructions of cooling elements having plate-shaped heat conduction elements; and Figure 10 illustrates in schematic horizontal sectional view a cooling element having zig-zag shaped heat conduction or dissipation elements.

Describing now the drawings, the exemplary embodiment of invention cooling apparatus shown in Figure 1 will be seen to comprise a container 13 filled with a suitable cooling fluid or medium or fluid coolant 14, for instance transformer oil, SF6-gas, air of a hydrogen-air mixture. Within such container 13 there are arranged adjacent and above one another a number of groups of structural components or elements 6 which are to be cooled. These component groups 6 are located in flow channels 23 or equivalent structure which are bounded by vertical lengthwise partitions or walls 20 and connected with horizontal transverse partitions 21. The group of structural components 6, best seen by referring to Figure 2, are to be conceived as arranged, together with their clamping device of Figure 1, perpendicular to the plane of the drawing towards the rear.The cooling fluid 14 flows, in the direction of the arrow A, from below towards the top through such flow channels or ducts 23. Between superimposed arranged longitudinal partitions 20 there are provided sealing elements 26 formed of any suitable elastic, for instance rubber-like or elastomeric material, which enable a flow of the cooling fluid 14 essentially in the flow direction A between superimposed arranged rows of the component groups 6.

The cooling fluid 14 can be maintained in a forced flow, with a pump 17 when working with a liquid coolant and a ventilator or the like when working with a gaseous fluid, through an external heat exchanger 18, a fluid inlet channel 15, a fluid filter 27, through the flow channels 23 in the container or vessel 13 and a fluid outlet channel 16. By means of not particularly shown, but conventional electrical lines the group of structural components 6 are connected with terminal contacts 19 at the top of the container 13.

Now as best seen by referring to Figure 2, the component group 6 can contain a number of tandemly arranged semiconductor elements 4, flow guide plates 5, for instance, formed of sheet metal, and cooling elements 1,which are pressed against one another at their contact surfaces in a statically defined clamping device. Such clamping device comprises, by way of example, essentially two transverse or crossties 10 or equivalent structure, both of the tension bolts 12, the two segmented pressure or contact spheres 8 or equivalent structure, the spring 9 and the tightening or clamping screw or threaded bolt 11 or the like. With such type clamping device or clamping means it is possible to clamp, with a predetermined tension, a group of components 6 by means of the transverse 10 and the clamping screw 11.The spring force of the spring 9 or equivalent resilient element is dimensioned such that the contact pressure exerted upon the elements of the structural group 6 remains within permissible threshold values, even with the greatest possible temperature fluctuations which are contemplated to be encountered. Such are dependent upon the diameter of the active portion of the semiconductor elements 4.

The semiconductor elements 4 of essentially diskshaped configuration, are cooled at both faces by metallic cooling elements 1 having good thermal conductance or heat dissipation properties. When working with small semiconductor elements a one sided cooling may be sufficient. The disk surfaces of such semiconductor elements 4 are in electrical and heat conducting connection with corresponding contact surfaces 24 of the cooling element base or floor 2 of the cooling element 1, as best seen by referring to Figure 5. In order to improve the heat transfer action it is possible to arrange between the disk surfaces of the semiconductor elements 4 and the cooling element bases floors 2 not particularly shown, good heat conducting, thin metal layers or foils, for instance formed of lead, nickel, aluminum, gold, silver or alloys, while utilizing one or a number of such metals.Such type metal layers can be applied, for instance by electrolytic separation or precipitation, vapour deposition and cathode atomization upon the contact semiconductor disk.

Between neighboring semiconductor elements 4 of a group of structural components or elements 6 there are arranged two cooling elements 1, the bases or floors 2 of which, in each case, are in pressure contact with the disk surfaces of the semiconductor elements 4 and their heat conduction or dissipation plugs or pins, that is to say, the heat conduction elements 3 are in pressure contact with one another.

Between both of these cooling elements 1 and between the cooling elements 1 at both ends of the structural group 6 and the segmented pressure or contact spheres 8 there can be arranged the flow conducting plates 5, simultaneously usable as electrical contacts. The current infeed brackets of such current conduction or conducting plates 5 protrude from the lateral boundary of the cooling elements 1, as best seen by referring to Figure 3. By incorporating such flow type conducting plates 5 it is possible to dispense with the use of other electrical connection elements. With the structural group 6, illustrated in Figure 2, the semiconductor elements 4 are arranged in a Graetz bridge circuit configuration; they can however also be connected, for instance, in series for other fields of application.

As best seen by referring to the left-hand portion of Figure 2, partitions or separation walls 22 are arranged transversely with respect to the flow channels 23 and they are connected with the trans verse partitions or walls 20 arranged along the structural group 6 and at a slight spacing with respect thereto between the traverses or crossties 10 of the clamping device. The partitions 22 insure that a fluid circulation through the flow channel 23 is accomplished essentially only through the recesses between the heat conducting plugs or elements 3 in the cooling elements 1. They prevent that there occurs in the flow channel 23 a flow essentially about the semiconductor elements 4 and about the segmented pressure spheres 8 of the clamping device.The partitions 20, 21, 22 consist of an electrical insulator, preferably formed of a suitable plastics material resistant to, as needed, SF6, oil and pressure.

As best seen by referring to Figures 3 to 10, the cooling elements 1 posses a gradratic configuration and essentially consist of a cooling element base or floor 2 and arranged oriented perpendicular to the plane of the contact surface 24 of the cooling element base or floor 2, substantially rod-shaped heat conducting plugs 3 or equivalent structure having a square or rhomboid cross-section or heat conducting or dissipation elements 3 formed as plate-shaped or undulated elements. At the cooling element floors or bases 2 there can be arranged, externally of such contact surface 24, turbulating pins 7 or equivalent structure which improve the heat conductance from the cooling element 1 to the cooling fluid 14. They are particularly suitable when using liquid coolants.The heat conducting elements 3 are connected by the material from which they are formed or idential or like material with the cooling element bases. Their cross-section can reduce with increasing spacing from the cooling element bases 2. It must at least be so large that there is insured over such heat conducting elements 3 a faultless force transmission by means of the clamping device.

Plug-shaped or pin-shaped heat conducting elements 3 advantageously have a diagonal thereof disposed transversely with respect to the flow direction A of the cooling fluid 14. When using rhomboid-shaped heat conducting plugs orthe like the shorter diagonal is aligned transversely with respect to the flow direction A. The heat conducting plugs are advantageously arranged at the same spacing from one another. For each square centimeter of surface perpendicular to the lengthwise direction of such plugs there is present, for instance, one heat conducting plug 3. The connection or connecting portion for the heat conducting plug 3 with the cooling element floor or base 2 is preferably shaped so as to be ogival or convergingly pointed.

Due to this configuration there is obtained a good heat transfer from the cooling element base to the heat conducting plug 3 or the like.

As best seen by referring to Figure 4, the cooling element base 2 can have an irregular or non-uniform wall thickness. Preferably the periphery or, as shown in broken lines, the central and the peripheral region of the cooling element base can have a lesser wall thickness than the region disposed therebetween.

Consequently, there is obtained a further improvement in the heat conductance. The length 1 of the heat conducting elements amounts to two-fold to eig htfold, preferably four-fold to sixfo Id, the maximum thickness dofthe cooling element base or floor 2.

There can be mounted, as by moulding or casting, by way of example, the longitudinal partitions 20 at the cooling elements 1, as such has been illustrated in Figures 6 to 10. These longitudinal or lengthwise partitions 20 augment the dissipation of heat to the cooling fluid.

The cooling elements 1 also can have a rectangular or plate-shaped configuration, and the longer side of the rectangle can have a length amounting to three to twenty times the length of the shorter side of the rectangle. Moreover, the shorter side of the rectangle or the narrow side of the plate, as the case may be, can be oriented essentially transversely with respect to theflow direction A of the cooling fluid, as illustrated in Figure 8, or can deviate from such direction by an angle of preferably less than 45 , as shown in Figure 9.

The heat conducting elements 3 are arranged in rows parallel to one another. Heat conducting ele ments of neighbouring rows are offset relative to one another, i.e. in the flow direction A of the fluid coolant aligned with the gap of neighbouring heat conducting elements within the preceding or subse quent row. Plug-shaped heat conducting elements of a row can be arranged partially in the intermediate spaces of the heat conducting elements of a neigh bouring row, as shown in Figure 6.

According to another construction, it is possible for the heat conducting elements to be oriented essentially in the flow direction A of the fluid coolant, and structured so as to be of surface-like or aereal configuration in an undulated or zig-zag shape, as shown in Figure 10.

What is important for the different shapes of the heat conducting elements is that there is present a slight flow resistance for the cooling fluid or coolant with relatively pronounced turbulence. In order to obtain a high cooling capacity or efficiency the heat exchange surfaces are also relatively large, their cross-section small and the transport paths of the heat or thermal energy to be removed are main tained as short as possible within the cooling element. As large as possible number of cooling surfaces are to be provided as close as possible to the heat source.

There will now be explained the mode of opera tion of the inventive cooling apparatus based upon the showing of Figures 1 and 2. By means of the circulation pump or the ventilator 17, a fluid coolant 14 is conveyed through the flow channels 23. The component groups 6, arranged in the flow channels 23, have the circulated coolant flowing thereabout and the electrical power losses, released in the form of heat by the semiconductor elements 4, are absorbed by the fluid coolant 14, removed and delivered to the surroundings by means of an external heat exchanger 18.By virtue of the parti tions 22 arranged transversely with respect to the direction of flow in the flow channels 23, the fluid coolant flows essentially through the cooling elements 1 or, as the case may be, through compound cooling elements 25 formed of two identical or similar cooling elements 1, and, if desired, having arranged therebetween a flow guide plate 5. The cooling elements are in heat conducting and electrical connection with one another by means of their heat conducting elements 3. The heat which is to be removed is predominantly transmitted from the heat conducting plugs or elements 3 to the turbulently flowing fluid coolant, and the flow essentially is directed perpendicular to the direction of orientation of the heat conducting elements.

When using hydrogen or a hydrogen-air mixture as the fluid coolant, there are to be employed specialty steels or coverings for the housing and lines in order to avoid the passage of hydrogen ions.

When using air as the fluid coolant there is unnecessary a closed fluid circulation system employing heat exchanger, particularly then when there does not exist any danger as concerns moisture and frost.

To counteract against possible contamination of the semiconductor elements there is then required an air filter 27 for cleaning the infed air. Air velocities of 4 mix to 12 m/s are standard. The pressure gradient within a heat conducting element is dependent upon the throughflow rate of the fluid medium and upon the modibilty of the fluid molecules, i.e., upon the temperature.

Of course, the subject matter of the invention is not so limited to what has been shown in the drawings. Thus, for instance, the container 13 for the cooling fluid or coolant 14 can be provided with cooling ribs, by means of which the heat can be transferred to the surroundings or to the prevailing air stream, and the fluid circulation system is arranged within such container or vessel. The heat conducting elements 3 of the cooling elements 1 also can be, for instance, circular, oval, star-shaped or parallelpiped. Their axes can be at an angle, differing from 90 , with respect to the plane of the contact surface 24 of the cooling element base 2. The number of heat conducting plugs per square centimeter (cm2) of cooling element base surface can be greater or smaller than one. The cooling element base can have a uniform wall thickness. The partitions or walls 20, 21 of the flow channels 23 can be arranged at an angle with respect to the container walls which differs from 900. Also, it is possible to use as the coolant different cooling agents than those herein mentioned.

Claims

1 A cooling apparatus for electrical components, especially semiconductor elements of the power electronics art, comprising: at least one group of structural components containing at least one electrical element and at least one cooling element; said elements being in mutual, heat conducting and electrical pressure contact with one another; a heat-absorbing cooling fluid surrounding said structural component group; a flow channel within there are arranged said electrical element and the cooling element within said heat-absorbing cooling fluid; and said flow channel being surrounded in a surface like manner by walls or longitudinal partitions.

2. The cooling apparatus as defined in claim 1, wherein: said heat-absorbing cooling fluid is a heat absorbing liquid; and said at least one group of structural components being arranged within the heat-absorbing liquid in the flow channel.

3. The cooling apparatus as defined in claim 1 or 2, further including: a container filled with the cooling fluid within which there are arranged the groups of structural components in mutually spaced relationship from one another; transverse partitions provided between adjacently arranged flow channels and between walls of the container and such flow channels; said longitudinal partitions being arranged essen tially parallel to the direction of flow of the cooling fluid along such groups of structural components and connected with said transverse partitions; partition means provided in each flow channel essentially transversely with respect to the direction of flow of the cooling fluid therein and transversely with respect to said longitudinal partitions; and said partition means shutting-off, in the flow direction within the flow channel, essentially all of the channel regions except those in which there are provided the cooling elements.

4. The cooling apparatus as defined in claim 3, wherein: said groups of structural components are arranged adjacent one another at a mutual spacing.

5. The cooling apparatus as defined in claim 3 or 4, wherein: said groups of structural elements are arranged in storeys above one another.

6. The cooling apparatus as defined in claim 3, 4 or 5, wherein: said longitudinal partitions are arranged at the cooling element.

7. The cooling apparatus as defined in claim 6, further including: sealing elements arranged between said longitu dinal partitions; and said longitudinal partitions being arranged in tandem in the direction of flow of the cooling fluid.

8. The cooling apparatus as defined in claim 3, further including: sealing elements arranged between said longitu dinal partitions; and said longitudinal partitions being arranged in tandem in the direction of flow of the cooling fluid.

9. The cooling apparatus as defined in any preceding claim, further including: heat conducting elements for heat conductively and electrically connecting two identical ones of said cooling elements with one another and forming a composite cooling element; and an electrical conductive flow guide element arranged between the cooling elements of the composite cooling element.

10. The cooling apparatus as defined in claim 9, wherein: said flow guide element is a flow guide plate.

11. The cooling apparatus as defined in preceding claim, wherein: said cooling fluid is at an excess pressure.

12. The cooling apparatus as defined in any preceding claim, wherein: said cooling fluid is an electrically insulating cooling liquid.

13. The cooling apparatus as defined in claim 12.

wherein: said electrically insulating cooling liquid is oil.

14. The cooling apparatus as defined in any one of claims 1 to 12, wherein: the cooling fluid is gaseous or vaporous.

15. The cooling apparatus as defined in claim 14, wherein: said cooling fluid is SF8-gas.

16. The cooling apparatus as defined in claim 14, wherein: said cooling fluid is a hydrogen-air mixture.

17. A cooling element for semiconductor elements of the power electronics art for use with a cooling fluid comprising: a cooling element base; heat conducting elements oriented essentially perpendicular to said cooling element base and connected therewith; and the connection portion of said heat conducting elements at the cooling element base possessing a predetermined configuration.

18. The cooling element as defined in claim 17, wherein: said predetermined configuration of said connection portion is substantially ogival.

19. The cooling element as defined in claim 17, wherein: said predetermined configuration of said connection portion is essentially covergingly pointed.

20. The cooling element as defined in claim 17, wherein: said heat conducting elements serve for a cooling apparatus of the type defined in claim 1.

21. The cooling element as defined in claim 17, wherein: said heat conducting elements are essentially plug-shaped or rod-shaped in configuration; said heating conducting elements having a rhomboid or square cross-sectional configuration; and said heat conducting elements having a diagonal thereof aligned essentially transversely with respect to the direction of flow of the cooling fluid.

22. The cooling element as defined in claim 17, wherein: said heat conducting elements possess a substantially plate-shaped or surface-shaped configuration; and a narrow side of such heat conducting elements being oriented essentially transversely with respect to the direction of flow of the cooling fluid.

23. The cooling element as defined in claim 22, wherein: said heating conducting elements possess an essentially undulated configuration viewed in the direction of flow of the cooling fluid.

24. The cooling element as defined in claim 22, wherein: said heat conducting elements possess as essentially zig-zag configuration viewed in the direction of flow of the cooling fluid.

25. The cooling element as defined in claim 17, 21 or 22, wherein: said heat conducting elements are arranged in rows essentially parallel to one another; and the cross-sectional surface of the heat conducting elements reducing with increasing spacing from the cooling element base.

26. The cooling element as defined in claim 21, wherein: said heat conducting elements being arranged in rows; and the heat conducting elements of neighbouring rows being offset with respectto one another.

27. The cooling element as defined in claim 17, 21 or 22, wherein: the wall thickness of the cooling element base decreases towards the peripheral region thereof; and said cooling element base at its central and peripheral region having a lesser wall thickness than in the intermediately dispositioned region.

28. The cooling element as defined in claim 17, 21 or 22, wherein: the ratio of the maximum length of the heat conducting elements to the maximum thickness of the cooling element base is in the order of approximately 2 to 8.

29. The cooling element as defined in claim 28, wherein: said ratio is in the order of 4 to 6.

30. The cooling element as defined in claim 17, 21 or 22, further including: turbulation pins arranged to protrude out of the peripheral region of cooling element base at the side of such cooling element base situated opposite the heat conducting elements.

31. A cooling apparatus substantially as herein described with reference to the accompanying drawings.

32. A cooling element substantially as herein described with reference to the accompanying drawings.