EP2884201A1

EP2884201A1 - High-efficiency heat exchanger for boilers and hot air generators

Info

Publication number: EP2884201A1
Application number: EP14197365.1A
Authority: EP
Inventors: Lorenzo Vergani
Original assignee: Apen Group SpA
Current assignee: Apen Group SpA
Priority date: 2013-12-13
Filing date: 2014-12-11
Publication date: 2015-06-17
Also published as: ITMI20132086A1; RU2014149802A

Abstract

A heat exchanger (1) is described comprising a combustion chamber (3), suitable to receive a burner (111), and a plurality of heat exchanger tubes (4) connected to said combustion chamber (3) and to one another by means of two tube plates (5, 6) of which at least one provided with a manifold (7) for releasing the combustion products. Each tube (4) of said plurality of heat exchanger tubes (4) has a flattened profile over its entire length and the combustion chamber (3) has a cylindrical shaped body.

Description

The present invention relates to a high-efficiency heat exchanger for boilers and hot air generators.
Heat exchangers comprising a combustion chamber, suitable to receive a burner, an exhaust fume chamber and a plurality of heat exchanger tubes communicating with the two chambers are known. Such heat exchangers are designed to be coupled with hot air generators to exploit the combustion products, such as fumes and aqueous vapor, to exchange thermal energy with the surrounding environment.
In particular, a heat exchanger comprising a plurality of tubes connected to one another and a combustion chamber by means of two tube plates, one front and one rear, is known from patent EP-1429085 ; the front plate is then provided with a manifold suitable to be connected to a chimney flue for expelling the combustion products.
The heat exchanger described in patent EP-1429085 is characterized in that it comprises heat exchanger tubes having circular section ends, said ends being at the connection points to the respective tube plates, and an intermediate portion in which the section becomes elliptical. The heat exchanger tubes are grouped on two opposite sides of the combustion chamber, which is drop-shaped, and in particular are arranged at the tapered part of said combustion chamber.
Furthermore, a heat exchanger comprising a plurality of heat exchanger tubes with a serpentine configuration, which have a flat, narrow central section, while the end portions have a circular section, is known from patent US-5271376 .
In both mentioned heat exchangers, as in many heat exchanger assemblies, the greater dimension is related to the size of the combustion chamber, which cannot be reduced any further without reducing energy efficiency or, in the worst cases, causing malfunctions due to the excessive overheating of the heat exchanger.
Furthermore, the circular geometry of the tube sections at their ends limits the compacting thereof because appropriate spaces are required to weld the surfaces to the plates and, at the same time, to allow the passage of fumes generated by combustion.
Wanting to reduce the volume occupied by the heat exchanger, while maintaining the geometry of the tubes described above unchanged, the only way is to reduce the number of the tubes themselves; however, this compromises performance and energy efficiency.
It is the object of the present invention to make a reduced size heat exchanger, which increases energy efficiency at the same time.
According to the present invention, said object is reached by means of a heat exchanger comprising a combustion chamber, suitable to receive a burner, and a plurality of heat exchanger tubes connected to said combustion chamber and to one another by means of two tube plates at least one of which is provided with a manifold for releasing the combustion products, said heat exchanger being characterized in that each tube of said plurality of heat exchanger tubes has a flattened profile over its entire length and in that said combustion chamber has a cylindrically shaped body.
The features and the advantages of the present invention will be apparent from the following detailed description of a practical embodiment thereof, illustrated by way of non-limitative example in the accompanying drawings, in which:

figure 1 is a perspective view of a heat exchanger according to the present invention;
figures 2a, 2b, respectively, show a heat exchanger tube comprised in the heat exchanger in figure 1 and a section view of the same tube taken along line II-II of figure 2a;
figure 3 is a side view of the heat exchanger in figure 1;
figure 4 is a front view of the heat exchanger in figure 1;
figure 5 is a rear view of the heat exchanger in figure 1;
figure 6 is a top view of the heat exchanger in figure 1;
figure 7 is a section view of the heat exchanger taken along line VII-VII in figure 3;
figure 8 is a section view of the heat exchanger taken along line VII-VII in figure 4;
figure 9 is a perspective view of a heat exchanger according to the present invention with the coupling of a burner.

Figure 1 shows a heat exchanger 1 according to the present invention. Said heat exchanger 1 substantially comprises a combustion chamber 3, suitable to receive a burner 111 (figure 9), and a plurality of heat exchanger tubes 4 connected to one another and to said combustion chamber 3 by means of two tube plates, one rear tube plate 5 and one front tube plate 6. For example, the burner 111 is a gas burner of the pre-mixed, low polluting emissions type.
In particular, both the combustion chamber 3 and the heat exchanger tubes 4 are connected to the rear tube plate 5, while only the heat exchanger tubes 4 are connected to the front tube plate 6 (figures 1, 3, 8). Said front tube plate 6 is also provided with a manifold 7 (figures 1, 4) for connecting to a chimney flue (not shown in the figures) suitable to release the combustion exhaust products.
Each of the tubes 4 of said plurality of tubes 4 has a flattened profile over its entire length (figure 2a, 2b), so that each tube comprises two substantially flat surfaces, an upper surface 12 and a lower surface 13, with a dimension prevalently along a single dimension, i.e. the horizontal dimension, while guaranteeing the same heat exchanging surface as a tube with circular/elliptical section comprised in the known heat exchangers. As easily understandable, the dimensions of a heat exchanger having tubes 4 with flattened profile are considerably reduced (figure 3).
Said heat exchanger tubes 4 also comprise a plurality of deformations 2 suitable to cause tortuous fume paths along the heat exchanger tube 4. In particular, the deformations 2 are made on the upper surface 12 and on the lower surface 13 of the tube 4 and may have appropriate geometries; for example, said deformations 2 may be shaped as oblique segments with respect to the length of the heat exchanger tube 4, said segments being mutually staggered (figure 2a).
Preferably, the heat exchanger tubes 4 (figure 7) are arranged in rows 8, each comprising at least two tubes 4, said rows 8 being stacked so that the tubes 4 between two adjacent rows 8 are horizontally staggered. Furthermore, as shown in figure 7, the tubes 4 are advantageously arranged over a single side of the combustion chamber 3.
Said combustion chamber 3 has a substantially cylindrical shaped body comprising a first base 9 connected to said rear tube plate 5 and a second base 10 provided with appropriate housing 11 suitable to insert the burner 111 (figure 9). A junction element 15, connected between said front tube plate 6 and said second base 10 of the combustion chamber 3, supports the structure of the heat exchanger 1.
The circular section of the combustion chamber 3 offers heat distribution uniformity by optimizing the production process and increasing the energy efficiency of the heat exchanger 1.
Advantageously, the heat exchanger 1 is made of stainless steel.
During operation, the fumes generated by the combustion caused by the burner 111 cross the rear tube plate 5 and, through the heat exchanger tubes 4, reach inside the front tube plate 6 (see the arrows in figure 8); in said front tube plate 6, the fumes reach condensation temperatures and are ejected by means of the chimney flue (not shown in the figure). In this manner, part of the heat is surrendered by the combustion chamber 3 and part is surrendered by the heat exchanger tubes 4, thus exchanging thermal energy with the surrounding environment. The flattened profile of the tubes 4 over their entire length allows a higher thermal efficiency because the fume speed is increased by virtue of such a conformation thus increasing the realized thermal exchange.
The heat exchanger 1 described above may be used for heating environments, e.g. in combination with a fan for generating a hot air flow (hot air generators) or similarly can be inserted as a module in a more complex machine, such as an air treatment unit (U.T.A.).
In both applications, by virtue of the geometry of the heat exchangers 4 and their arrangement on a single side of the combustion chamber 3, the thermal efficiency is increased and the dimensions of the heat exchanger 1 are reduced at the same time.

Claims

Heat exchanger (1) comprising a combustion chamber (3), suitable to receive a burner (111), and a plurality of heat exchanger tubes (4) connected to said combustion chamber (3) and to one another by means of two tube plates (5, 6) at least one of which is provided with a manifold (7) for releasing the combustion products, said heat exchanger (1) being characterized in that each tube (4) of said plurality of heat exchanger tubes (4) has a flattened profile over its entire length and in that said combustion chamber (3) has a cylindrically shaped body.
Heat exchanger (1) according to claim 1, characterized in that said heat exchanger tubes (4) comprise a plurality of deformations (2) suitable to cause tortuous fume paths along the heat exchanger tube (4).
Heat exchanger (1) according to claims 1 and 2, characterized in that each of said heat exchanger tubes (4) comprises two flat surfaces, an upper surface (12) and a lower surface (13), and in that said deformations (2) are realized on said upper surface (12) and on said lower surface (13).
Heat exchanger (1) according to claims 1-3, characterized in that said deformations (2) are shaped as oblique segments with respect to the length of the heat exchanger tubes (4), said segments being mutually staggered.
Heat exchanger (1) according to claims 1-4, characterized in that said heat exchanger tubes (4) are arranged over a single side of said combustion chamber (3).
Heat exchanger (1) according to anyone of the preceding claims, characterized in that said heat exchanger tubes (4) are arranged in rows (8) each comprising at least two tubes (4), said rows (8) being stacked so that the heat exchanger tubes (4) between two adjacent rows (8) are horizontally staggered.
Heat exchanger (1) according to anyone of the preceding claims, characterized in that both the combustion chamber (3) and the heat exchanger tubes (4) are connected to the rear tube plate (5), and in that only the heat exchanger tubes (4) are connected to the front tube plate (6).
Heat exchanger (1) according to anyone of the preceding claims, characterized in that a junction element (15), connected between said front tube plate (6) and a base (10) of the cylindrically shaped body of the combustion chamber (3), supports the structure of the heat exchanger (1).