WO2015015369A1

WO2015015369A1 - Aluminium radiator with elliptical finned tubes

Info

Publication number: WO2015015369A1
Application number: PCT/IB2014/063332
Authority: WO
Inventors: Giuseppe VELLER; Luca MENEGUZZO
Original assignee: Convett S.R.L.
Priority date: 2013-07-31
Filing date: 2014-07-23
Publication date: 2015-02-05
Also published as: ITVI20130201A1; EP3028286A1; EP3028286B1

Abstract

The invention concerns a radiator element (100) suitable, for example, for cooling electrical transformers by means of a cooling oil, comprising at least one tubular component (101) suited to contain a cooling fluid and to allow this fluid to circulate between its two opposite ends. This tubular component (101) comprises a plurality of main external longitudinal ribs (120) with predefined cross section, projecting from its outer surface.

Description

ALUMINIUM RADIATOR WITH ELLIPTICAL FINNED TUBES.

TECHNICAL FIELD OF THE PRESENT INVENTION

The present invention concerns the field of cooling techniques using a cooling fluid.

In particular, the present invention concerns the cooling techniques that use cooling oil to cool electrical devices like, for example, power and distribution electrical transformers. In greater detail, the present invention concerns an oil or fluid radiator in general, in particular for cooling devices of the above mentioned type.

STATE OF THE ART

Different types of radiators are known in the art for cooling electrical devices like transformers and similar devices.

A first type of radiators is constituted by panel radiators. These radiators essentially comprise one or more panels, each obtained by joining (for example, welding) two metallic half-shells at the level of their edges. Each one of the half- shells is obtained by cutting a portion of sheet having a suitable length from a coil, as well as by pressing each portion of sheet in such a way as to give it the desired shape, essentially the shape of a half-shell. The number of panels can obviously vary depending on the required performance, in particular depending on the desired heat dissipation. Obviously, during use, the two opposite ends of each panel are connected respectively to a delivery manifold and to a discharge or outlet manifold, wherein the delivery and discharge manifolds are mutually connected respectively by means of a main delivery and discharge manifold. The cooling oil coming from the transformer thus circulates by natural convection . between the two opposite ends of each panel and transfers heat towards the outside through the metal.

A second type of radiators is constituted by the so-called tubular radiators. In this case, each radiator is produced by using tubular units (for example, made of carbon steel) and assembling them in such a way as to form individual elements made up of a plurality of tubular units. The tubes or tubular units of each element are connected through a delivery cap and a return cap respectively connected (for example, welded) at the opposite ends of each single tube of the element, as well as by connecting the delivery caps through a delivery manifold and the return caps through a return manifold. In this way, the cooling oil coming from the transformer flows into the delivery caps through the manifold and then reaches the return caps through the single tubes, successively flowing out of the radiator through the return or outlet manifold.

The radiators of the known type described above, even if useful for several types of applications, however entail several drawbacks that can be summed up as follows.

A first inconvenience or drawback of panel radiators regards their efficiency (in terms of heat dissipation), which is rather limited, especially in the case of radiators characterized by a high number of panels and/or panels positioned very near each other. Substantially, in these cases the heat dissipated by a panel is at least partially reabsorbed by the adjacent panel. The direct consequence of this reduced efficiency is that for a particular application (for example, for cooling an electrical transformer) it is necessary to increase the number of panels (however, in this case dissipation efficiency is further reduced) and/or the dimensions of the same. In this last case, however, problems arise that are due to the increase in weight and make the radiator difficult to handle during both transport and operation. £¾.

The known panel radiators have also a structural problem, in fact they are made in such a way that they do not include lowered portions (elements that make it possible to place the flange of the inlet or delivery manifold at a lower height compared to the inlet manifold itself) larger than 400-500mm. ¾

In fact, the technicians in charge with sizing the radiators for a transformer always plan to interface with the transformer tank with a distance between centers that is not always the same as that of the radiator. The tank, in fact, sometimes allows for coupling distances between centers that are much smaller than the optimal dimension for radiators, a dimension that must be studied taking in consideration the thermal misalignment between the active part of the transformer and the thermal center of gravity of the radiators.

Therefore, the radiator has the first two or three elements lowered to the maximum dimension allowed by the size of the transformer tank, while the other elements that make up the entire radiator are raised in order to better exploit the radiator by increasing oil circulation in a natural convection regime (the higher the thermal misalignment, the faster the oil flow and the better the heat dissipation obtained, as the so-called "hydronic load" determined by the fluid density variation caused by the temperature variation is higher).

Regarding radiators of the type with panels, a further problem that characterizes them derives from the fact that they cannot be tested under pressures exceeding 2-2.5 bars. In fact, higher pressures deform the piece. Technical specifications (for example, the TERNA specification) are already available that set testing pressures at 350kPa (3,5Bar), therefore these specifications exclude the use of panel radiators.

With regard to tubular radiators, instead, these have a heat dissipation efficiency that is even 30% higher than that of panel radiators; furthermore, they make it possible to face structural problems in a more proper manner (it is possible to make portions lowered even by 1000-1 100mm) and they resist even testing pressures of 9 bars.

On the other hand, tubular radiators are penalized by a quality/cost ratio that sometimes leads users to prefer panel radiators even if they offer lower performance levels. In fact, the welding and assembly technology used to make tubular radiators is certainly more expensive than the welding technology used to make panel radiators, which are much simpler to weld and manufacture.

Finally, the radiators of both types, if made of iron, have problems related to resistance to corrosion that make them unsuitable for cooling power and/or distribution electrical transformers located (as it often happens) in places with varying and more or less aggressive environmental conditions (classified according to standard EN ISO 12944-2). Therefore, protection systems are required that should be provided with coatings (painted and if necessary zinc- plated) having increasingly important and expensive final thicknesses in economic and even environmental terms. For example, for a class C5M application - marine environment with a high content of salts - nominal thicknesses equal to 320 um are required.

Finally, there are often size and transport problems that, both during transport and disassembly of the radiators from the transformer and in the site where the transformer is used, make it necessary to resort to solutions with complex layouts due, in fact, to the considerable volume occupied by the cooling system of the transformer.

It is therefore one object of the present invention to overcome the drawbacks mentioned above and observed in the known radiators of the state of the art.

In particular, the aims and objects of the present invention can be summed up as follows.

It is a first object of the present invention to reduce or at least limit the final cost of the radiator.

The second aim or object of the present invention is to improve the radiator's resistance to corrosion, reducing the quantity of paint to be used with benefits in terms of environmental protection and in terms of production time and thus of offer to the user.

A further object of the present invention is to considerably reduce the overall dimensions of the entire cooling system (including the radiator), offering the user the opportunity to solve the increasingly frequent problems related to the space available for the installation of transformers.

It is another object of the present invention to considerably simplify the logistic aspects, especially regarding the transport of transformers and of their cooling system, with consequent reductions in transport costs.

It is another object of the present invention to produce a system that from the thermal point of view is capable of reducing the inertia of the transformer system, reducing the transient at the level of the voltage peaks and consequently reducing the localized temperature increase, in particular at the level of the windings, allowing on the contrary an extension of the transformer's useful life (reduced dilatations, mechanical stress, losses due to the Joule effect).

Finally, a direct consequence of the aspects described above is the reduction of the overall quantity of oil that is necessary, with evident advantages in terms of direct costs emerging during production, but also indirect environmental advantages that can be noticed successively in relation- with decommissioning and/or oil regeneration operations.

The aims and objects mentioned and described above are achieved by means of a radiator suited to cool, for example, electrical transformers as claimed in claim 1.

Further advantages will also be obtained by means of the further embodiments of the present invention defined in the dependent claims.

DESCRIPTION OF THE PRESENT INVENTION

The present invention can be particularly and conveniently applied in the field of cooling systems for electrical devices and/or equipment, for example power and distribution electrical transformers. Therefore, this is the reason why examples of application of the radiator according to the invention to the specific field of cooling system for electrical transformers are described and/or mentioned here below.

It should however be noted that the possible applications of the radiator according to the present invention are not limited to the specific case of electrical transformers or devices in general.

On the contrary, the present invention can advantageously be applied to all those cases in which the user wishes to cool a system generating passive heat by means of a cooling fluid.

The present invention is based on the general concept that the drawbacks or disadvantages that are typical of the solutions known in the art (in particular of both panel and tubular radiators according to the known art) can be overcome or at least minimized by making a tubular radiator in which the radiating surface of the tubular elements is increased compared to that of traditional tubular elements with substantially elliptical cross section. In particular, according to the present invention, the radiating and/or heat exchange surface of the tubular elements can be conveniently increased (thus improving dissipation efficiency) by properly modifying the cross section of the tubular elements. In greater detail, the present invention intends to provide the tubular elements (at least one of them) with external longitudinal ribs or fins.

The present invention is based on a further consideration according to which heat dissipation can be increased by using aluminium and/or aluminium-based light alloys to make the tubular components. In fact, since aluminium is characterized by high heat conductivity, the heat of the cooling fluid inside the tubes will be effectively dissipated, especially owing to the presence of the ribs or fins mentioned above.

Furthermore, the present invention is based on the further consideration according to which by making the tubular elements from section bars (for example, in extruded aluminium) the problems (at least part, if not all of them) related to logistic aspects, overall dimensions, weight, economic aspects of the radiators of the known type can be overcome or at least reduced; furthermore the radiator's resistance to corrosion will be increased, so that it will be possible to avoid the painting and/or zinc-plating operations that otherwise would be necessary, for example in the case of iron radiators.

Based on the considerations expressed above, a first embodiment of the present invention comprises a radiator element according to claim 1, meaning a radiator element suited, for example, to cool electrical transformers by means of a cooling oil, said radiator element comprising at least one tubular component suited to contain a cooling fluid and to allow this fluid to circulate between its two opposite ends, wherein said at least one tubular component comprises a plurality of main external longitudinal ribs or fins with predefined cross section and projecting from the outer surface of said at least one component.

Preferably, said at least one component is made of aluminium or an aluminium alloy or in any case a material with heat conductivity exceeding 100 W/m K.

Still preferably, said at least one component is constituted by a portion of an extruded section bar with predefined length.

According to a variant embodiment, said at least one component can have a substantially elliptical cross section.

According to a further variant embodiment of the invention, said radiator comprises a plurality of said components.

Preferably, said components are divided into groups made up of a predefined number of said components, the components of each single group being in communication with one another through a first delivery cap and a second return cap that are respectively in communication with the opposite ends of each one of said components, the delivery caps of each group being in communication with each other through a delivery manifold, the return caps of each group being in communication with each other through a return manifold.

Still preferably, at least one of said main external ribs of said at least one tubular component has a substantially oval ring-shaped cross section.

According to a further variant and/or embodiment, at least one of said main external ribs of said at least one tubular component comprises a plurality of secondary external ribs that extend from the outer surface of said at least one main external rib.

According to a further variant, said at least one main external rib of said at least one tubular component comprises two secondary external ribs that extend from the free end of said at least one main rib opposite said tubular component in such a way as to form a predefined internal angle.

If necessary, said at least one main external rib of said at least one tubular component may comprise two secondary external ribs that respectively extend from the opposite outer surfaces of said at least one main rib.

In the same way, said at least one tubular component may even comprise a plurality of internal longitudinal ribs with predefined cross section, projecting from the inner surface of said at least one component.

Again, according to an alternative solution, at least two of said internal ribs respectively project from opposing portions of the inner surface of said at least one component.

According to a further alternative, said at least two external ribs respectively extend from the opposing vertices of said at least one tubular component with elliptical cross section.

Alternatively, at least one of said internal ribs can extend between opposite portions of the inner surface of said at least one tubular component and/or the free ends of the secondary external ribs of said at least one tubular component that extend from at least one of the opposing outer surfaces of said component with substantially elliptical cross section may respectively lie on a plane that is parallel to the main plane of symmetry of said at least one tubular component. Finally, further embodiments of the invention are defined in the dependent claims.

The invention also concerns a preferably oil-cooled electrical transformer comprising a radiator element, wherein said radiator element is constructed according to the description provided above and/or the concepts claimed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated here below through the following description of some of its embodiments represented in the attached drawings. It should however be noted that the present invention is not limited to the embodiments represented in the drawings; on the contrary, the purpose and the scope of the present invention include all those variants or modifications of the embodiments represented and described herein that will result to be clear, obvious and immediate to the expert in the art. In particular, in the attached drawings:

- Figures 1 and 2 show perspective views of a radiator according to an embodiment of the present invention;

- Figure 3 shows a perspective view of a detail of the radiator according to an embodiment of the present invention;

- Figure 4 shows an exploded view of a radiator according to an embodiment of the present invention;

- Figures 5, 6, 7, 8, 9 and 10 show sectional views of a tubular component of the radiator according to corresponding embodiments of the present invention. DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT

INVENTION

In Figures 1 and 2 the radiator according to the present invention is identified by reference number 100. In particular, the radiator 100 comprises a plurality of tubes or tubular components 101, each one of which is suited to contain a cooling fluid (generally a cooling oil) and to allow said fluid to circulate inside it, essentially from one end to the opposite end. The tubular components 101, in particular, are placed in fluid-dynamic connection with one another through a plurality of upper caps 102 and lower caps 103, as well as through an upper manifold 104 and a lower manifold 105. In greater detail, the tubular components 101 (in total in the number of one hundred and eight, but the total number can obviously vary according to the needs and/or circumstances) are divided into groups or elements, each element or group comprising a predefined number of tubular components 101 (equal to nine in the example represented herein, but also in this case the number of tubular components making up each group can vary according to the needs and/or circumstances). For each group of tubular components 101 there are an upper or delivery cap 102 and a lower or return cap 103. An end portion of each tubular component 101 is housed in the delivery cap 102, while the opposite end portion of the same tubular component 101 is housed in the return cap 103. It can thus be inferred that the cooling fluid flowing into the delivery cap 102 will reach the return cap 103 through the tubular components 101 that, in fact, are respectively connected to the delivery cap 102 and the return cap 103. Furthermore, the delivery caps 102 are mutually connected through a delivery manifold 104, while the return caps 103 are mutually connected through a return manifold 105. It can thus be inferred that the cooling fluid flowing in through the delivery manifold 104 will be distributed among the various delivery caps 102 and from there, through the tubular components 101, will reach the return caps 103, from which it will exit through the return manifold 105. For the connection of the delivery manifold 104 to the main cooling system there is a connection flange 106, while a connection flange 107 allows connection to the same main system of the return manifold 105. While a detailed description of the main system mentioned above is omitted for the sake of brevity, it should be noted that said main system will be such as to allow the cooling fluid to capture or absorb the passive heat emitted, for example, by an electrical device (in particular, by an electrical transformer) so that the absorbed heat will be transferred and dissipated towards the outside through the radiator 100.

Figures 1 and 2 show also a hook or ring 108 for lifting and handling the radiator 100, as well as a valve 109 arranged on the delivery manifold 104 and a valve 1 10 arranged on the return manifold 105. The valve 109 can serve, for example, to allow the outflow of air bubbles from the radiator, bubbles that would hinder the circulation of the cooling fluid, or even to allow the fluid to be topped up, while the lower valve 1 10 can serve to empty the radiator 1 10.

From the detail shown in Figure 3 it is possible to observe a first important characteristic of the radiator according to the present invention, meaning the fact that the tubular components 101 (described in greater detail below with reference to other figures) are provided with longitudinal ribs or fins suited to increase the radiating and/or heat exchange surface of each tubular component 101. In this way, it is possible to increase the dissipation efficiency of the radiator.

The exploded view of Figure 4 makes it possible to observe some important details of the radiator 100. In particular, it can be inferred from Figure 4 that each one of the delivery caps 102 is formed by two opposite half-shells 102s and 102d that are joined in such a way as to form a hollow element, and in particular in such a way as to define housing seats, each one having a shape corresponding to that of the cross section of a tubular component 101. In this way, as already mentioned, the end portion of a tubular component 101 can be accommodated in the housing seat of the cap 102 defined by the two opposite and joined half-shells 102s and 102d. Furthermore, each one of the two half-shells 102s and 102d comprises a portion, substantially in the shape of a semicircle, suited to accommodate the upper manifold 104. In particular, also the upper manifold 104 is formed by two opposite half-shells, of which only the half-shell 104s is shown in the figure. The mutual connection of the delivery caps 102 is thus obtained by arranging the two opposite half-shells of the manifold so as to define a substantially tubular element, and by arranging them in the semicircular seats provided in the caps. Obviously, the tightness of the radiator, intended to avoid cooling fluid leakages, can be obtained by means of several solutions among those known in the art, for example by welding, glueing, etc. the various component parts. Said solutions do not fall within the scope of the present invention, therefore their detailed description is omitted for the sake of brevity. The explanation provided above in relation to the upper or delivery caps 102 and the upper or delivery manifold 104 obviously applies also to the return caps 103 and the return manifold 105.

Among the materials suited to be used to make the radiator 100 according to the present invention, aluminium and/or aluminium-based light alloys are certainly worth mentioning. In particular, the materials with heat conductivity exceeding lOOW/m K have proven to be among the most suitable ones. Aluminium, in fact, is characterized by high heat conductivity and therefore it is particularly suitable for making the tubular components 101 that, as will be explained below, can be conveniently produced by cutting portions of section bars, for example extruded section bars, having predefined length. In the same way, aluminium and/or light alloys can be used to make the caps 102, 103 and/or the manifolds 104 and 105, as aluminium is particularly advantageous when used to make the half-shells of both the caps and the manifolds. Obviously, using aluminium and/or light alloys means obtaining clear advantages in terms of weight reduction and/or limitation. As already mentioned, Figure 5 illustrates a very important characteristic of the radiator according to the present invention; Figure 5, in fact, shows a cross sectional view of one of the tubular components 101 of the radiator. Said tubular component 101 has a substantially elliptical cross section, meaning that it has two opposite curved portions joined to each other at the level of two opposite vertices. The tube 101 with substantially elliptical cross section thus defines an inner volume V suited to contain a cooling fluid (for example, oil) and to allow said fluid to circulate inside it (substantially from one end to the other of the tube 101 and thus perpendicularly to the plane of Figure 5). Main external ribs 120 extend from the outer surface of the tubular component 101, in particular from the outer surface of each one of the opposite curved portions of the tube 101, in a substantially perpendicular direction with respect to the plane of symmetry P of the main body, with substantially elliptical cross section, of the tube 101. Each one of said external ribs or fins 120 has substantially the shape of an oval ring (in cross section and thus parallel to the plane of the figure), with two portions of the outer plane and parallel surface joined by an end curved portion. It can thus be understood that, thanks to the presence of the main external ribs 120, the radiating surface of the tubular component 101 will be increased, and consequently the dissipation efficiency of the component 101 will also be improved. Obviously, the number, shape and location of the main external ribs, as well as their dimensions (length perpendicular to the plane P and width parallel to the plane P) may vary according to the needs and/or circumstances as well as to the special applications for which the radiator can be intended. For example, the oval ring shape (in cross section) of the ribs 120 may vary, as it is also possible to have ribs in a different shape on the same component 101. The location of the ribs and their mutual distance may also vary, as it is possible, for example, to have ribs that extend forming an angle different from a straight angle with respect to the plane P, as well as ribs 120 that extend towards the outside at the level of or in proximity to the vertices of the main body with substantially elliptical cross section.

Figure 5 shows also two internal ribs 121 that extend from the inner surface of the component 101, each at the level of one of the vertices of the ellipse and substantially having the aim to increase the rigidity of the component 101. It should be noted that in the embodiment shown in Figure 5 the ends of the ribs 120 extending from the outer surface of one of the curved portions of the component 101 lie on a plane PI, while the ends of the ribs that extend from the outer surface of the other curved portion (opposite the first one) lie on a plane P2 parallel to the plane PI, the planes PI and P2 thus being parallel to the plane of symmetry P of the tube 101.

There are thus two factors that according to the present invention make it possible to improve the dissipation efficiency of the radiator, and precisely the presence of the external longitudinal ribs or fins (where the word longitudinal means that the ribs or fins or tabs extend in a direction parallel to the longitudinal extension of the tubular component), as well as the possible use of aluminium or an aluminium-based alloy to make the tubular components 101, which improves heat transmission from the cooling fluid to the tubular component 101. Furthermore, the use of aluminium makes it possible to employ portions of section bars, for example extruded section bars, with predefined length, with obvious advantages in terms of simplified radiator assembly operations and at limited prices. In practice, it will be sufficient to cut portions of section bars with predefined length and to assemble them together with the caps and the manifolds, as previously described.

In Figure 3 it is also possible to observe that the longitudinal extension of the external ribs or fins 120 is smaller than the overall extension of the tubular component 101 ; in fact, it can be understood from Figure 3 that the ribs 120 are present only on the centre portion of each tubular component 101, while they are absent at the level of the end portions. In this way, the end portions of the tubular component 101 can be housed more easily in the respective delivery cap 102 and return cap 103. Obviously, in the case of manufacture of the tubular components by cutting portions of a section bar with predefined length it will be necessary to remove the ribs or fins 120 at the level of the ends of each portion, an operation that on the other hand can be easily carried out through known solutions, like for example milling or similar operations.

In the embodiment shown in Figure 6 (in which component parts already described above with reference to other figures are identified by the same reference numbers), the difference with respect to the embodiment shown in Figure 5 is given by the shape of the two opposite internal ribs 121 that in this case extend more markedly towards the inside of the tubular component 101 respectively from its two opposite vertices. In this case, the two ribs 121, in addition to increasing the rigidity of the tubular component 101, make it also possible to increase the inner surface of the tubular component 101 in contact with the cooling oil, with evident advantages in terms of improved heat transmission from the oil to the component 101, and thus of heat dissipation from the component 101 towards the outside. Obviously, also in this case, the shape, size and location of the internal ribs may vary according to the needs and circumstances.

A further embodiment of the present invention is shown in Figure 7, in which, as usual, component parts or characteristics that have already been described above with reference to other figures are identified by the same reference numbers. In this case, the tubular component 101 comprises a plurality of further internal ribs 122 in addition to the internal ribs 121 that extend towards the inside, each from one of the two vertices of the tubular component 101 with substantially elliptical cross section. In particular, the internal ribs 122 extend from the opposite inner surfaces of the two curved portions 100 of the tubular component 101, respectively. Increasing the number of the internal ribs, as well as changing their shape, size and location, if necessary, means further increasing the inner surface of the tubular component 101 in contact with the cooling fluid and thus heat transmission from the cooling fluid to the tubular component, with consequent heat dissipation towards the outside thanks to the heat conductivity of the material and to the external ribs 120 described above.

The solution adopted according to the further embodiment of the invention illustrated in Figure 8 makes it possible to further improve heat dissipation from the tubular component 101 towards the outside. In this case, in fact, each one of the main external ribs 120 (one or more of them depending on the needs and/or circumstances) is provided with secondary external ribs 123 (in variable number, size and shape) that extend from the outer plane and opposite surfaces of the main rib 120 in a direction that is substantially perpendicular to the longitudinal extension of the main external rib 120, and thus substantially parallel to the plane of symmetry of the tubular component 101 with substantially elliptical cross section. Obviously, also the direction according to which the secondary external ribs or fins 123 extend may vary according to the needs and/or circumstances. For example, Figure 10 shows a particular embodiment, in which each one of the main external ribs 120 (one or more of them) comprises two secondary ribs 125 extending from the free end (opposite the main body of the tubular component 101) of the rib 120 according to predefined angles, in particular in such a way that the cross section of the rib 120 is substantially Y-shaped.

According to a further embodiment of the invention shown in Figure 9, the tubular component 101 is provided with internal ribs 124 that extend between the two opposite inner surfaces respectively of the two curved portions of the main body of the tubular component 101, said ribs, if necessary, being connected to each other, for example, as shown in Figure 9, through a connection or coupling portion substantially parallel to the longitudinal axis of symmetry of the tubular component 101.

It has thus been shown through the above description that the radiator according to the present invention makes it possible to overcome or at least minimize the drawbacks of the radiators according to the known art, and thus to achieve the set objects. In particular, the radiator according to the present invention will be characterized by high dissipation efficiency (thanks to the internal and/or external ribs or fins of the tubular components) and even thanks to the fact that the tubular components are made of aluminium or an aluminium-based alloy. The radiator according to the present invention can furthermore be assembled through simple and inexpensive operations, in particular in the case where the tubular components are obtained from section bars (for example, extruded section bars) by cutting portions with predefined length. Moreover, the radiator according to the present invention will be characterized by high resistance to corrosion as well as by reduced or limited weight and overall dimensions.

Obviously, even if the radiator according to the present invention has been illustrated through the description of its embodiments shown in the figures, the present invention is not limited to the embodiments described herein and shown in the figures. For example, it will be clear for the experts in the art that the solutions described herein and illustrated in the drawings can be changed and/or combined with one another; for example, while the external ribs or fins 120 and 123 are shown in Figure 8 in combination with the internal ribs 121, all the possible shapes, sizes and locations of the internal ribs 121 can be combined with the external ribs 120 and 123 of Figure 8. In the same way, all the possible external ribs described herein can be combined with one or more of the solutions provided for the internal ribs.

Finally, according to an embodiment not illustrated in the figures, the external ribs or fins can be at least partially hollow, meaning that each of them can be such as to define an inner volume that communicates with the inner volume of the main body of the tubular component.

The invention concerns also a preferably oil-cooled electrical transformer comprising a radiator element, wherein said radiator element is made according to the description provided above.

Although the present invention has been illustrated above through the detailed description of some of its embodiments, shown in the drawings, the present invention is not limited to the embodiments described above and shown in the drawings; on the contrary, further variants of the described embodiments fall within the scope of the present invention, which is defined in the claims expressed below.

Claims

1. Radiator element (100) suitable, for instance, for cooling electrical transformers by means of a cooling oil, said radiator element (100) comprising at least one tubular component (101) suited to contain a cooling fluid and to allow said cooling fluid to circulate between its two opposite ends, characterized in that said at least one tubular component (101) comprises a plurality of main external longitudinal ribs (120) with predefined cross section, projecting from the outer surface of said at least one component (101).

2. Element according to claim 1, characterized in that said at least one component (101) is made of aluminium or an aluminium alloy or a material with heat conductivity exceeding 100 W/m K.

3. Element according to any of claims 1 and 2, characterized in that said at least one component (101) is obtained from a portion of a section bar with predefined length, for instance an extruded section bar.

4. Element according to any of claims from 1 to 3, characterized in that said at least one component (101) has a substantially elliptical cross section.

5. Element according to any of claims from 1 to 4, characterized in that it comprises a plurality of said components (101).

6. Element according to claim 5, characterized in that said components (101) are divided into groups made up of a predefined number of said components, the components (101) of each single group communicating with one another through a first delivery cap (102) and a second return cap (103) that respectively communicate with the opposite ends of each one of said components (101), the delivery caps (102) of each group being in communication with each other through a delivery manifold (104), the return caps (103) of each group being in communication with each other through a return manifold (105).

7. Element according to any of claims from 1 to 6, characterized in that at least one of said main external ribs (120) of said at least one tubular component (101) has a substantially oval ring-shaped cross section.

8. Element according to any of claims from 1 to 7, characterized in that at least one of said main external ribs (120) of said at least one tubular component (101) comprises a plurality of secondary external ribs (123, 125) that extend from the outer surface of said at least one main external rib (120).

9. Element according to claim 8, characterized in that said at least one main external rib (120) of said at least one tubular component comprises two secondary external ribs (125) that extend from the free end of said at least one main external rib (120) opposite said tubular component (101) so as to form a predefined internal angle.

10. Element according to claim 8, characterized in that said at least one main external rib (120) of said at least one tubular component (101) comprises two secondary external ribs (123) that respectively extend from the opposite outer surfaces of said at least one main rib (120).

1 1. Element according to any of claims from 1 to 9, characterized in that said at least one tubular component (101) comprises a plurality of internal longitudinal ribs (121) with predefined cross section, projecting from the inner surface of said at least one component (101).

12. Element according to claim 10, characterized in that at least two of said internal ribs respectively extend from opposite portions of the inner surface of said at least one component (101).

13. Element according to claim 12, characterized in that said at least two internal ribs (121) respectively extend from the opposite vertices of said at least one tubular component (101) with elliptical cross section.

14. Element according to any of claims from 1 1 to 13, characterized in that at least one of said internal ribs extends between opposite portions of the inner surface of said at least one tubular component (101).

15. Element according to any of claims from 4 to 14, characterized in that the free ends of the secondary external ribs (120) of said at least one tubular component (101) that extend from at least one of the opposite outer surfaces of said component with substantially elliptical cross section respectively lie on a plane that is parallel to the main plane of symmetry P of said at least one tubular component (101).