[0001] The present invention relates to a high-efficiency heat exchanger for boilers and
hot air generators.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] It is the object of the present invention to make a reduced size heat exchanger,
which increases energy efficiency at the same time.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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).
[0015] 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).
[0016] 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.
[0017] 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.
[0018] 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.
[0019] Advantageously, the heat exchanger 1 is made of stainless steel.
[0020] 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.
[0021] 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.).
[0022] 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.
1. 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.
2. 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).
3. 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).
4. 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.
5. 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).
6. 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.
7. 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).
8. 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).