WO2005028966A1

WO2005028966A1 - Heat exchanger

Info

Publication number: WO2005028966A1
Application number: PCT/EP2004/010537
Authority: WO
Inventors: Renato Montini
Original assignee: Renato Montini
Priority date: 2003-09-23
Filing date: 2004-09-20
Publication date: 2005-03-31
Also published as: ITVR20030047U1

Abstract

A heat exchanger (1), comprising at least one first exchange tube (2) and at least one second exchange tube (3), further comprising at least two coil turns arranged substantially at a cylindrical surface that lies around the longitudinal axis of the burner and respectively have a first end for connection to an inlet (5) of a fluid to be heated and a second end for connection to an outlet (6) for a heated fluid, the turns of said at least one first tube (2) being alternated with the turns of said at least one second tube (3), said heat exchanger further having spacer means (9) between adjacent turns.

Description

HEAT EXCHANGER Technical Field The present invention relates to a heat exchanger particularly suitable to be used in boilers for so-called domestic use. Background Art Traditionally, heat exchangers, especially for domestic applications, are substantially constituted by a tube that contains a fluid to be heated, generally water. The outer surface of the tube is subjected to the thermal action, in this case a heating action, produced by the combustion fumes generated by a burner. In practice, the function of the tube or tubes is to transfer heat from the fumes to the water. Various solutions have been proposed in order to improve heat exchange. First of all, an attempt has been made to increase the heat exchange surface of the tube or tubes by using, for example, a coiled tube; in other cases, the tube has been bent so that its generatrix lies along a cylindrical surface that is coaxial to the burner (in practice providing, by means of a tube portion, a plurality of turns). Naturally, with particular reference to the last type described, the tube is connected at its ends to respective connectors, which are connected to at least one inlet for the water to be heated and to at least one outlet for the heated water. Some solutions, especially adapted for boilers that have a horizontally-arranged burner, allow to use in series one or more modules, each constituted by a tube that forms coil turns and optionally has an oval (or otherwise flattened) cross-section. However, solutions of this kind, though being currently widely used, have problems, including the low specific power, which sometimes does not allow to keep space occupation below the threshold required for domestic applications.

Disclosure of the Invention The aim of the present invention is to eliminate or at least drastically reduce the drawbacks noted above in known types. Within this aim, an object of the invention is to provide a heat exchanger that can offer high reliability in operation. A further object of the invention is to provide a heat exchanger that can be applied to boilers having different power outputs and sizes. A further object of the present invention is to provide a heat exchanger that has a very simple structure and is highly durable. A still further important object is to provide a heat exchanger that has a competitive production cost, so as to be advantageous also from the economical standpoint. Another object of the invention is to provide a heat exchanger that has low consumption, high efficiency and low maintenance costs. This aim and these and other objects that will become better apparent hereinafter are achieved by a heat exchanger according to the invention, characterized in that it comprises at least one first exchange tube and at least one second exchange tube, which comprise at least two coil turns arranged substantially on a cylindrical surface that lies around the longitudinal axis of the burner and respectively have a first end for connection to an inlet of a fluid to be heated and a second end for connection to an outlet for a heated fluid, the turns of the first tube being alternated with the turns of the second tube, the heat exchanger further having spacer means between adjacent turns. Advantageously, a heat exchanger according to the invention is characterized in that the first exchange tube and the second exchange tube comprise at least one respective heat exchange portion that has a substantially oval transverse cross-section. Conveniently, a heat exchanger according to the present invention is characterized in that the spacer means are constituted by at least two comblike elements, which respectively have a supporting element, which, is arranged externally to said cylindrical surface and is substantially parallel to the longitudinal axis, each supporting element being associated with a plurality of spacers that protrude toward the longitudinal axis and are designed to be interposed between two adjacent turns. Brief description of the drawings Further characteristics and advantages of the invention will become better apparent from the description of preferred but not exclusive embodiments of a heat exchanger according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein: Figure 1 is a partially sectional side elevation view, taken along a longitudinal plane, of a boiler with a first embodiment of a heat exchanger according to the invention associated therewith; Figure 2 is a view, similar to Figure 1, of a second embodiment of the heat exchanger; Figure 3 is a view, similar to Figures 1 and 2, of a third embodiment of a heat exchanger according to the invention; Figure 4 is an enlarged-scale view of the spacer means; and Figure 5 is a sectional view, similar to Figure 4, of another embodiment of the heat exchanger according to the invention. In the examples of embodiments that follow, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other examples of embodiments. Moreover, it is noted that anything found to be already known daring the patenting process is understood not to be claimed and to be the subject of a disclaimer.

Ways to carrying out the Invention With reference to the figures , a heat exchanger according to the invention, generally designated by the reference numeral 1, comprises at least one first exchange tube 2 and at least one second exchange tube 3. Both the first exchange tube 2 and the second exchange tube 3 are shaped, at least at the central portion, so as to form coil turns and in particular they have at least two turns that lie on a cylindrical surface that is coaxial, during use, to the longitudinal axis of the burner 4 that is designed to be associated with the heat exchanger 1. Conveniently, as also clearly shown in Figures 1 to 3, the turns of the first exchange tube 2 are arranged, on the plane that lies diametrically to the cylindrical surface, so that they are alternated with the turns of the second exchange tube 3. Both the first exchange tube 2 and the second exchange tube 3 have a first end for connection to an inlet 5, in this particular case for the water to be heated, and a second end for connection to an outlet 6 for the heated water. Advantageously, with reference to the embodiments shown in Figures 1 and 2, between the first ends of the first exchange tube 2 and of the second exchange tube 3 and the inlet 5 there can be an upper manifold 7, designed to feed the water in input to the heat exchanger 1 ; in a fully similar manner, a lower manifold 8 is arranged between the second ends of the first exchange tube 2 and of the second exchange tube 3 and the outlet 6 and is adapted to send the liquid in output from the heat exchanger 1 to the outlet 6. Also according to the present invention, the heat exchanger 1 can have spacer means 9 between two adjacent turns. In particular, as clearly shown in the enlarged-scale sectional view of

Figure 4, the spacer means 9 can be constituted by at least two comb-like elements, conveniently arranged in diametrically opposite positions with respect to the longitudinal axis of the burner 4. The comb-like elements, according to a preferred embodiment, have a supporting element 10, which in the illustrated example is arranged outside the first exchange tube 2 and the second exchange tube 3; however, said supporting element 10 might also be arranged inside them. Conveniently, in both cases the supporting element 10 is substantially parallel to the longitudinal axis of the burner 4. A plurality of spacers 11 protrude from the supporting element 10, in the illustrated cases toward the longitudinal axis of the burner 4, and are designed to be interposed between two adjacent turns so as to keep them spaced. Conveniently, the spacers 11 can be arranged at right angles to the supporting element 10. Also according to the present invention, the first exchange tube 2 and the second exchange tube 3 have a respective heat exchange portion, which with reference to the figures substantially corresponds to the coil-shaped portion. Advantageously, the respective heat exchange portion has a substantially oval or otherwise flattened transverse cross-section. In order to allow heat exchange optimization, the major axis of the transverse cross-section is arranged substantially at right angles to the longitudinal axis of the burner 4. However, the transverse cross-section can be constituted, as clearly shown in Figure 4, by two flat portions 12 (arranged at right angles to the longitudinal axis of the burner 4), which are connected by means of respective end portions 13. With particular reference to the cross-section shown in Figure 5, the respective heat exchange portions can have a transverse cross-section provided with two inclined flat portions 20a and 20b, which diverge from the longitudinal axis of the burner 4 toward the supporting element 10 and the corresponding spacers 11. Conveniently, as clearly shown by Figure 5, the two inclined flat portions 20a and 20b are connected at their ends by means of respective curved end portions 22. With particular reference to the embodiment shown in Figure 2, it is also possible to provide means for reversing the flow of the fumes, which can be provided for example by inserting a reversing plate 14 inside the cylindrical surface on which the turns lie. Such reversing plate 14 is designed to force the flow of fumes to pass through the heat exchanger through the gaps provided between the adjacent turns, thus increasing efficiency. With reference to a further examplary embodiment, clearly shown in

Figure 3, it is possible to use, on a same boiler, a first heat exchanger 100 and a second heat exchanger 101. In this case, the first connection ends of the first tube 2 and of the second tube 3 of the first heat exchanger 100 are connected to the upper manifold 7, while the second ends of the first tube 2 and of the second tube 3 of the second heat exchanger are connected to the lower manifold 8. In particular, in this embodiment there is an intermediate manifold 14, which is connected in an upward region to the second ends of the tubes that constitute the first heat exchanger 100 and, in a downward region, to the first ends of the second heat exchanger 101. Operation of the heat exchanger according to the present invention is evident from what has been described above. All the characteristics of the invention described above as advantageous, convenient or the like may also be omitted or be replaced with equivalents. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. In this regard, the heat exchanger 1 can be constituted by more than two exchange tubes (for example four), so as to increase the specific power, allowing to provide a heat exchanger that is compact yet offers high power outputs. In practice it has been found that the invention has achieved the intended aim and objects in all of its embodiments. In particular, thanks to the use of two or more separate exchange tubes, a high specific power has been achieved by limiting load losses considerably. Moreover, the oval cross-section, and particularly the use of the oblique and diverging flat portions, of the heat exchange portion and the spacer means have allowed to increase efficiency considerably. In practice, the materials used, so long as they are compatible with the contingent use, as well as the shapes and dimensions, may be any according to requirements. All the details may further be replaced with other technically equivalent elements. The disclosures in Italian Utility Model Application No. VR2003U000047 from which this application claims priority are incorporated herein by reference.

Claims

CLAIMS 1. A heat exchanger, characterized in that it comprises at least one first exchange tube and at least one second exchange tube, which comprise at least two coil turns arranged substantially at a cylindrical surface that lies around a longitudinal axis of the burner and respectively have a first end for connection to an inlet of a fluid to be heated and a second end for connection to an outlet for a heated fluid, the turns of said at least one first tube being alternated with the turns of said at least one second tube, said heat exchanger further having spacer means between adjacent turns. 2. The heat exchanger according to claim 1, characterized in that said first exchange tube and said second exchange tube comprise at least one respective heat exchange portion having a substantially oval transverse cross-section. 3. The heat exchanger according to claim 1, characterized in that said spacer means comprise at least two comb-like elements, which have a respective supporting element arranged substantially parallel to said longitudinal axis, for a plurality of spacers that protrude toward said longitudinal axis and are designed to be interposed between two adjacent turns. 4. The heat exchanger according to one or more of the preceding claims, characterized in that said supporting element is arranged outside said cylindrical surface. 5. The heat exchanger according to one or more of the preceding claims, characterized in that said spacers lie on a plane that is substantially perpendicular to said longitudinal axis. 6. The heat exchanger according to one or more of the preceding claims, characterized in that said spacers lie along a direction that is substantially parallel to the plane of arrangement of the longer dimension of the transverse cross-section of said exchange tube. 7. The heat exchanger according to one or more of the preceding claims, characterized in that said heat exchange portions have a transverse cross-section that comprises two inclined flat portions that diverge from said longitudinal axis toward the outer surface of said cylindrical surface. 8. The heat exchanger according to one or more of the preceding claims, characterized in that said first ends of said first exchange tube and of said second exchange tube are connected to an upper manifold. 9. The heat exchanger according to one or more of the preceding claims, characterized in that said second ends of said first exchange tube and of said second exchange tube are connected to a lower manifold. 10. The heat exchanger according to one or more of the preceding claims, characterized in that it comprises an intermediate manifold, which is connected, at a first portion that is arranged upwardly during use, to said second ends of a first heat exchanger and, at a second portion that is arranged downwardly during use, to said first ends of a second heat exchanger. 11. The heat exchanger according to one or more of the preceding claims, characterized in that it comprises fume reversing means. 12. The heat exchanger according to one or more of the preceding claims, characterized in that said fume reversing means comprise a reversing plate, which is arranged inside said turns and lies on a plane that is substantially perpendicular to said longitudinal axis.