WO2013068991A1

WO2013068991A1 - Heating radiator element made op die-cast aluminium

Info

Publication number: WO2013068991A1
Application number: PCT/IB2012/056310
Authority: WO
Inventors: Orlando NIBOLI; Maurizio BOLOGNA; Fabio Sassi; Francesco Franzoni
Original assignee: Fondital S.P.A.
Priority date: 2011-11-09
Filing date: 2012-11-09
Publication date: 2013-05-16
Also published as: EA025798B1; EA201490936A1; ES2557191T3; WO2013068991A8; CN104053964A; CN104053964B; PT2776774E; ITMI20112028A1; EP2776774A1; PL2776774T3; EP2776774B1

Abstract

A heating radiator element (1) made of die-cast aluminium, extending along a longitudinal axis (A) and having a monolithic die-cast aluminium structure (15), has a tubular body (2) and connections (7) which protrude from opposite lateral sides (20) of the body (2) along respective central axes (X) to connect the element (1) to other similar elements and/or to an external hydraulic system; at least one connection (7) arranged at an upper end (3) of the element (1) has a continuous annular lateral surface (21), without radial projections and defining an annular channel (22) which completely surrounds the connection (7) and is delimited at the rear by the side (20) of the element (l).

Description

"HEATING RADIATOR ELEMENT MADE OF DIE-CAST ALUMINIUM"

TECHNICAL FIELD

The present invention concerns a heating radiator element made of die-cast aluminium.

BACKGROUND ART

In general, a radiator for heating buildings consists of a battery of radiator elements positioned side by side, normally (although not necessarily) produced separately and then assembled to form a radiator of appropriate dimensions . Typically, each radiator element has a main body which is essentially tubular and provided with an inner chamber in which ^■ a hot fluid circulates (commonly, water) . * Some main types of radiator element are particularly widespread, which are characterised essentially by the component material and by some structural features due to the production technology. In fact, the manufacturing technologies and materials directly affect the structure of the radiator elements and their heat exchange mechanisms .

Performance requirements actually have to be reconciled with production requirements. For these reasons, solutions adopted on radiator elements of a certain type cannot be immediately reproduced on radiators of other types .

Radiators made of die-cast aluminium (in which the radiator element consists of a monolithic body made of aluminium or aluminium alloy obtained by die-casting) are characterised with respect to other types, for example aluminium radiators produced by extrusion (consisting of an extruded central body to which two end headers are subsequently fixed) or radiators made of cast iron or other metallic materials, not only by the production technologies but also by some structural characteristics, which are due to the materials used and the production techniques .

In the specific sector of die-cast aluminium radiator elements, the general configuration of the single radiator element is substantially consolidated and consists essentially of a tubular body provided with inner water chamber and hydraulic connections arranged at the opposite ends of the element; from the water chamber, along a centreline plane of the element, two opposite aluminium partitions branch off, supporting a front plate and a rear plate respectively; a plurality of heat exchange fins protrude from the tubular body.

One of the reference parameters commonly used to characterise a radiator element is the specific power per unit of weight, i.e. the ratio between the thermal power emitted by the radiator element and transferred to the environment (measured according to specific standards, for example EN 442) and the weight of the element (which is the fundamental parameter directly affecting production costs) .

It is a common belief in the sector that the die-cast aluminium radiator elements currently available have now reached the limits of their performance and can be improved no further, or only minimally.

Furthermore, all solutions potentially capable of improving the efficiency of a radiator element must be compatible with the overall dimensions of the radiator elements, which are generally restricted, since consolidated market standards have to be complied with, in particular in terms of width (maximum width of the element, normally defined by the distance between the free ends of the hydraulic connections arranged at the same end of the element) , depth (distance between the front and rear plates) and centre distance (distance between the centres of the hydraulic connections) . The current design criteria for die-cast aluminium radiator elements have resulted in products with specific powers considered at the moment to be satisfactory and practically non- improvable .

The technicians of the Applicant, however, have ascertained that the known solutions still have significant margins for improvement, which can be achieved by completely changing the approach to the problem of the increase in specific power.

DISCLOSURE OF INVENTION

One object of the present invention is to provide a die-cast aluminium heating radiator element which has a high thermal performance, superior to that of a traditional radiator element of comparable dimensions and weight, and complying with the market dimensional standards.

The present invention therefore relates to a die-cast aluminium heating radiator element as essentially defined in the attached claim 1 and, in its preferred embodiments, in the dependent claims .

Compared to known radiator elements, the radiator element of the invention has decidedly superior performance, with the same footprint and dimensions, and specifically a superior specific power .

The improvement in performance is obtained by a particular shape of the area of the hydraulic connections of the element, shaped so as to favour heat exchange between the aluminium and the air with respect to the heat exchange between the water (circulating inside the radiator element) and the aluminium, as in the known art which considers the water/aluminium exchange the critical aspect to be improved in order to increase the performance of the radiator element. In a radiator element, the heat is transferred to the environment to be heated in three successive stages: first, the heat is transferred by the water that circulates inside the radiator element (namely in the water chamber) to the walls of the water chamber by forced convection; the heat is then transferred by conduction to the inside of the aluminium structure of the radiator element, passing from the walls of the water chamber to the other parts of the element (fins, partitions, plates) ; lastly, the heat is transferred from the aluminium to the air of the environment in which the radiator element is installed essentially by natural convection (in addition to radiation but to a significantly lesser and substantially negligible extent) . The radiator element therefore includes a water circuit, defined by the water chamber and by the hydraulic connections that connect the element to adjacent elements and/or to an external hydraulic system, and an air circuit, defined by the volumes available for passage of the air around the aluminium structure of the element.

According to the current common knowledge of the phenomena of heat exchange in a radiator element, and specifically a die-cast aluminium radiator element, the most effective heat exchange part is considered the high temperature part between the water and the aluminium. The known art consequently prescribes an increase in the temperature and the dimensions of the water/aluminium exchange surfaces. This approach is overall unfavourable to heat exchange between the aluminium structure of the radiator element and the surrounding air, since it limits the space available and therefore the speed and efficiency of the aluminium/air heat exchange .

Actually, the technicians of the Applicant have realised that the critical aspect for increasing the efficiency of the radiator element (its specific power) is the heat exchange between the aluminium and the air, and not the heat exchange between the water and the aluminium.

According to the invention, therefore, the transmission of heat is increased between the aluminium of the radiator element and the air that laps its surfaces, specifically in the critical area around the hydraulic connections, in particular those at the upper end of the element .

The invention derives from the adoption of a new approach to the problem of increasing the specific power of a radiator element made of die-cast aluminium.

Instead of trying to increase the heat exchange at high temperature between the water circulating in the element and the aluminium structure (for example, by increasing the metallic surfaces at high temperature, and/or by increasing the dimensions of the water chamber) , as in the common teachings of the known art, according to the invention priority is given to the heat exchange between the aluminium structure and the surrounding air. In fact it has surprisingly been found that it is the aluminium/air heat exchange that represents the critical stage in the overall heat exchange of the radiator element.

In particular, it has been recognised that a traditional radiator element has critical areas in which the speed of the air that laps the surfaces of the element is relatively low, and in these areas the heat exchange can be improved.

Specifically, a critical area for the aluminium/air heat exchange is the area surrounding the hydraulic connections, especially those arranged at the upper end of the element. According to the design criteria generally accepted in the sector, to increase the power of a radiator element it is necessary to increase the heat exchange surfaces in contact with the hot water, and therefore in particular to provide exchange surfaces (fins, partitions, etc.) which develop from the water chamber and from the hydraulic connections.

In fact, the traditional radiator elements have metal exchange elements which extend from the outer lateral surface of the connections and connect it in particular to an upper fin which also (and mainly) has aesthetic functions.

Examples of known solutions of this type, available on the market, are illustrated in figures 1 and 2.

In reality, it has been ascertained that this type of solution increases the weight and dimensions of the hydraulic connection without a significant increase in the effective exchange surface .

The radiator element according to the invention, on the other hand, allows a more uniform and complete utilisation of the available exchange surfaces, improved utilisation also of the aesthetic fin normally positioned at the top of the element and improved utilisation of the lateral surface of the connection, in addition to the area of the partition above the connection . In this way, significant advantages are achieved in terms of heat exchange performance and efficiency, confirmed by experimental data: the whole of the lateral surface of the connection is effectively exploited for the aluminium/air heat exchange; the entire surface of the partition above the hydraulic connection can be used for the heat exchange; the space freed around the hydraulic connection can be used to develop additional finned surfaces (which do not interrupt the channel around the connection) .

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will appear clear from the description of the following non- limiting embodiment examples, with reference to the figures of the accompanying drawings, in which:

figures 1 and 2 are partial lateral schematic views of known radiator elements;

- figure 3 is a perspective schematic view of a heating radiator element made of die-cast aluminium according to the invention;

figure 4 is a lateral schematic view of an upper end portion of the radiator element of figure 3;

- figure 5 is a lateral schematic view of a variation of the radiator element of figures 3-4.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to figures 3 and 4, a heating radiator element 1 made of die-cast aluminium comprises a substantially tubular monolithic body 2 made of aluminium (said term also comprising aluminium alloys) by means of a die-casting process.

The element 1 and the body 2 extend substantially along a longitudinal axis A (in use, substantially vertical) between two axially opposed ends 3 , ; the body 2 is provided with a main inner water chamber 5 for passage of the water, radially delimited by a lateral wall 6 arranged around the axis A and closed axially at respective opposite longitudinal ends; advantageously, but not necessarily, the body 2 has a cross section (perpendicular to the axis A) substantially oval, elliptic or in any case elongated along an axis, and the lateral wall 6 of the body 2 which delimits the chamber 5 is tapered towards one of the ends 3 , 4. The ends 3 , 4 of the element 1 are provided with respective pairs of connections 7 which protrude from opposite sides of the body 2 along respective central axes X parallel to each other and substantially perpendicular to the axis A to connect the element 1 to other similar elements and/or to an external hydraulic system; the connections 7 are shaped for example (but not necessarily) like cylindrical sleeves with circular section and are internally provided with transverse through ducts 8 , communicating with the chamber 5.

The element 1 comprises a system 10 of heat exchange fins.

In particular, the system 10 comprises: a pair of partitions 11 which protrude diametrically opposite from the lateral wall 6 along a longitudinal centreline plane of the element 1; a front plate 12 and a rear plate 13 , arranged at respective ends of the partitions 11 and substantially perpendicular to the partitions 11 and parallel to the axis A, optionally formed of several sectors or portions of plate separated by slits and/or apertures; a plurality of lateral fins 14 which protrude from the body 2, namely from the lateral wall 6 and/or from the partitions 11.

The element 1 has a width L (maximum width of the element 1, given by the distance between the opposite free ends of each pair of connections 7 aligned along an axis X) , a depth P (distance between the plates 12, 13) and a centre distance I (distance between the central axes X of the connections 7) .

The body 2, including the connections 7, and the system 10 define as a whole an aluminium structure 15 of the element 1. The entire structure 15 constitutes a monolithic piece produced by die-casting.

The element 1 includes a water circuit 16, defined by the main chamber 5 delimited by the wall 6 and by the ducts 8 of the connections 7; and an air circuit 17, defined by the volumes available for passage of the air around the structure 15. With specific reference to figure 4, the connections 7 protrude from opposite lateral sides 20 of the body 2 along the axes X; each of the connections 7 arranged at the upper end 3 of the element 1 has a continuous annular lateral surface 21 closed in a ring, which extends from the side 20 and is without interruptions and/or radial projections protruding from it and defines an annular channel 22 which completely surrounds the connection 7 and is delimited at the rear by the side 20 of the element.

The connection 7 is attached to the respective side 20 by means of a root edge 23 and the side 20 extends all around the root edge 23; the channel 22 therefore has an end wall 24 defined by the portion of the side 20 which surrounds the root edge 23.

Preferably, but not necessarily, the connection 7 has central symmetry with respect to the central axis X and has a lateral wall of uniform thickness around the central axis X.

At least one deflecting element 25 faces a portion of the lateral surface 21 of the connection 7 and is radially spaced from the lateral surface 21 to define a portion of the channel 22.

In the example of figure 4, the deflecting element 25 includes an upper heat exchange fin 26, arranged above the connection 7 and radially spaced from it to define an upper portion of the channel 22 around the connection 7; the fin 26 extends from the side 20 and is not connected to the lateral surface 21 of the connection 7.

In the variation of figure 5, in which the details similar or identical to those already described are indicated by the same numbers, the deflecting element 25 includes one or more lateral heat exchange fins 27, arranged on one or respective sides of the connection 7 to define respective portions of the channel 22 around the connection 7; the lateral fins 27 extend from the side 20 of the element 1 and are not connected to the lateral surface 21 of the connection 7.

Lastly, it is understood that further modifications and variations can be made to the radiator element described and illustrated here which do not depart from the scope of the attached claims.

Claims

1. A heating radiator element (1) made of die-cast aluminium, extending along a longitudinal axis (A) and having a monolithic structure (15) made of aluminium by die-casting, comprising a tubular body (2) and connections (7) that extend from opposite lateral sides (20) of the body (2) along respective central axes (X) for connecting the element (1) to other similar elements and/or to an external hydraulic system; the element (1) being characterized in that at least one connection (7) arranged at an upper end (3) of the element (1) has a continuous annular lateral surface (21) , without radial projections and defining an annular channel (22) that surrounds completely the connection (7) and is delimited at the back by the side (20) of the element (1) .

2. The element according to claim 1, wherein the connection (7) is connected to the side (20) by means of a root edge (23) and the side (20) of the element (1) extends all around said root edge (23) .

3. The element according to claim 1 or 2, wherein at least one deflecting element (25) faces a portion of the lateral surface (21) of the connection (7) and is spaced radially apart from said lateral surface (21) for defining a portion of the channel (22) .

4. The element according to one of the preceding claims, wherein the connection (7) has central symmetry with respect to the central axis (X) .

5. The element according to one of the preceding claims, wherein the connection (7) has a lateral wall having uniform thickness around the central axis (X) .

6. The element according to one of the preceding claims, and provided with an upper heat exchange fin (26) , arranged over the connection (7) and radially spaced apart therefrom for defining an upper portion of the channel (22) around the connection (7) ; the fin (26) extending from the side (20) of the element (1) and being not connected to the lateral surface (21) of the connection (7) .

7. The element according to one of the preceding claims, and provided with one or more heat exchange lateral fins (27) , arranged on one or respective sides of the connection (7) for defining respective portions of the channel (22) around the connection (7); the lateral fins (27) extending from the side (20) of the element (1) and being not connected to the lateral surface (21) of the connection (7) .