ITBO20100636A1 - HEAT EXCHANGER, IN PARTICULAR FOR CONDENSING BOILERS - Google Patents

Description

DESCRIPTION

â € œHEAT EXCHANGER, ESPECIALLY FOR CONDENSING BOILERSâ €

The present invention relates to a heat exchanger, in particular, to a heat exchanger to be used in condensing boilers.

In other words, the heat exchanger which is the main object of the present invention finds an advantageous, but not exclusive application in the construction of condensing boilers, to which the following description will make explicit reference without thereby losing generality.

In fact, as is well known, in Europe construction is evolving towards the design and construction of houses with ever lower energy requirements for heating.

The individual States, urged by the European Community through the issuance of binding Directives, proceed to adapt by issuing laws, decrees and implementing regulations that incentivize the construction of houses with increasingly lower energy needs, encouraging, or even, obliging employment. of condensing boilers.

The condensing boiler market is therefore developing rapidly, generating an offer of solutions at increasingly reduced costs.

Currently on the market there are condensing boilers with exchangers made with different materials and different technologies:

1. stainless steel exchangers using straight smooth or finned tubes;

2. heat exchangers made of stainless steel using smooth tubes wrapped in serpentine;

3. aluminum exchangers using smooth or finned tubes;

4. aluminum exchangers using the die-casting technique;

5. heat exchangers made of aluminum by ground casting.

All these solutions, with the exception of the last one, have been created to obtain modular products; in order to be able to realize different power sizes with the same basic components.

These are solutions that involve the use of single tubes, often finned with the addition of welded fins, always contained inside containers which are themselves made up of several parts; all united through the use of complex manifolds, in turn made up of several parts.

The present invention falls within the field of heat exchangers referred to in point (4).

In fact, the solution object of the present invention is based on the aluminum die casting technology, less expensive than the earth casting technology, to obtain a heat exchanger with a drastic reduction in the number of components required and therefore with a significant reduction of costs.

Therefore, according to the present invention there are provided a heat exchanger, as claimed in claim 1, and a condensing boiler comprising the aforementioned heat exchanger as defined in claim 10.

For a better understanding of the present invention, some preferred embodiments are now described, purely by way of non-limiting examples and with reference to the attached drawings, in which:

Figure 1 illustrates a three-dimensional view of a first embodiment of a heat exchanger according to the present invention inserted in a condensing boiler;

- figure 2 shows an exploded view of the condensing boiler of figure 1;

Figure 3 shows an enlarged detail of the heat exchanger of Figures 1, 2 seen from a first observation point;

- figure 4 shows the detail of figure 3 seen from a second observation point;

figure 5 illustrates a front view of the detail shown in figures 3, 4;

figure 6 shows a plan view of the detail shown in figures 3, 4, 5;

Figure 7 illustrates a three-dimensional view of a section of some details included in the condensing boiler of Figure 1;

figure 8 shows a plurality of elements inserted in the heat exchanger illustrated in figure 1;

Figure 9 illustrates a three-dimensional view of a second embodiment of a heat exchanger according to the present invention inserted in a condensing boiler; And

- figure 10 shows an exploded view of the condensing boiler in figure 9.

In Figure 1, 100 indicates as a whole a condensing boiler comprising a heat exchanger 10, made according to the dictates of the present invention, on which a traditional burner 50 is mounted.

Figure 2 shows an exploded view of the condensing boiler 100 shown in figure 1.

The heat exchanger 10 in turn comprises three essential parts:

- a direct exchange element, the so-called main body 11;

- a series of indirect exchange elements, called inserts 12; and

- a container 13, which, as we shall see, contains inside both the main body 11 and the inserts 12; it should also be noted that the container 13 is provided with a cold water inlet fitting 13a and a hot water outlet fitting 13b (figures 1, 2).

In this first embodiment the container 13 has an axial-symmetrical shape which allows it to resist the internal pressures of the water with minimal mechanical stresses.

In the condensing boiler 100, as is known, there are two fluids in circulation which exchange heat: - the exhaust gases produced in the burner 50, and

- the water from the heating circuit that flows inside the heat exchanger 10.

The main body 11 constitutes the element of heat exchange between exhaust gas and water. This main body 11 is preferably, but not necessarily, obtained as one piece by means of a single aluminum die-casting operation.

The exhaust gases are generated during the combustion process, which occurs in a known manner in the burner 50 through a combustion process of the air / combustible gas mixture pushed inside the burner 50 itself by a fan (not visible).

The container 13 contains, together with the main body 11, the water of the hydraulic circuit and collects the exhaust gases coming from the burner 50.

The exhausted gases, after exchanging heat with water, according to a method that will be better seen later, are discharged from an outlet 13c (figures 1, 2), and sent to a chimney (not visible). Since, as mentioned, the boiler 100 is of the condensing type, some elements, such as water vapor, contained in the exhaust gases condense before being discharged into the atmosphere. The condensate produced, in turn, is removed from the heat exchanger 10 with the usual systems (see below).

As shown in particular in Figures 3, 4, the main body 11 comprises a substantially cylindrical and finned combustion chamber 14, at least partially.

From the bottom of the combustion chamber 14 a series of channels 15 run by the exhaust gases branch downwards and terminate at an end flange 16 parallel to the bottom of the combustion chamber 14. The flow of exhausted gases in the channels 15 takes place according to a first direction identified by an arrow (F1). In this case the direction (F1) is vertical.

As shown in particular in Figure 6, each channel 15 is defined by a pair of vertical baffles 17a, 17b, substantially parallel to each other, which in plan and in the case of the embodiment shown in Figures 1-8, are of a € œcordsâ €, parallel to each other, of a circumference (CIR) that encloses the main body 11. In the same way, each pair of vertical baffles 17b, 17a also defines a duct 18 closed above and below by parallel walls, respectively, to the bottom of the combustion chamber 14 and to the end flange 16.

Therefore the exhaust gas channels 15 alternate with the water pipes 18 to be heated. It should also be noted that, while the exhaust gas channels 15 do not communicate with each other but all with the outlet 13c of the container 13, the water pipes 18 are in hydraulic communication with each other (see below).

More specifically, as shown in greater detail in figures 3, 4, in the main body 11 there are also some horizontal dividing baffles 19, parallel to the end flange 16 and to the bottom of the combustion chamber. 14. These horizontal dividing baffles 19 obviously do not interrupt the flow of exhaust gases according to the arrow (F1).

As will be seen better in the following, in the main body 11 there are also vertical dividers 20, which, together with the horizontal dividers 19 and the internal wall (SUPI) of the container 13 (see also figures 6, 7) , of the zones 21a, 21b, 21c, 21d within which the passage of the water takes place which is obliged to pass through these zones 21a, 21b, 21c, 21d in directions perpendicular to the channels 15 crossed by the exhaust gases (see below). In other words, the water passes through the zones 21a, 21b, 21c, 21d in directions (F2), substantially horizontal and perpendicular to the aforementioned direction (F1) of the exhaust gases.

As shown in particular in Figures 3, 4, both the horizontal dividers 19 and the vertical dividers 20 are provided with relative gaskets 19a, respectively 20a, which, when the main body 11 is mounted inside the container 13 , rest on the inner surface (SUPI) of the container 13 itself, defining regions in which there cannot be the passage of water between one zone 21a, 21b, 21c, 21d and the other.

As shown in particular in Figures 3, 4, recesses 22a, 22b (Figure 3) are made in correspondence with each horizontal partition 19, and on an ideal external surface (SUPE) (Figure 2), which is substantially cylindrical in the main body 11, 22c (figure 4) having the purpose of allowing the passage of water from the zone 21a furthest from the combustion chamber 14 to the next 21b closest to the combustion chamber 14, to finally reach the zone 21d that surrounds and embraces the chamber combustion chamber 14 itself. Evidently, the gaskets 19a, 20a, serve to ensure that the outflow of water between one area 21a, 21b, 21c, 21d and the other, occurs using only the recesses 22a, 22b, 22c.

In other words, it is as if the zones 21a, 21b, 21c, 21d constituted sorts of overlapping `` floors '' joined together, two by two, by the recesses 22a, 22b, 22c, which, therefore, represent sort of â € œscaleâ € between one â € œpianoâ € and the other. This is to allow the water to flow from the inlet fitting 13a towards the outlet fitting 13b (figure 1), after having undergone the desired heating during the outflow into the ducts 18 and in a cavity (INT) defined, on one side, from the aforementioned internal surface (SUPI) of the container 13, and, on the other, from the recesses 22a, 22b, 22c and from the spaces (SP1), (SP2), SP3), (SP4), (SP5) (figure 7) left empty by the channels 15, which do not always, in use, rest on the internal surface (SUPI) of the container 13 (Figure 7).

As always shown in figures 3, 4 the water flows preferably in directions (F2) substantially perpendicular to the direction (F1) of the flow of the exhaust gases, with paths in parallel or in series within each single zone 21a, 21b, 21c, 21d as needed.

In reality, the set of ducts 18 gives rise to a path for the water substantially in a horizontal labyrinth, except for the vertical passages constituted by the recesses 22a, 22b, 22c of transit from an area 21a, 21b, 21c, 21d to the other.

Figure 3 shows a solution having the zone 21a divided into four conduits 18 run by the water in parallel in one direction, followed by three conduits 18 run in parallel in the opposite direction.

Zone 21b, immediately above zone 21a, is divided into 18 ducts, initially in parallel and subsequently in series.

Finally, the zone 21c, below the combustion chamber 14, comprises a plurality of ducts 18 crossed by the water only in series.

This subdivision of the various zones 21a, 21b, 21c, 21d was made with the aim of having higher water speeds, and therefore lower thermal inputs per unit of mass of water in transit, in order to reduce the risk of boiling of the water itself is minimal. In fact, especially in the areas close to the combustion chamber 14, due to the large amount of heat that is transferred there by the exhaust gases, there is a danger that the water will boil.

To overcome this drawback, the solution shown in particular in figures 5, 7 was adopted.

In fact, in at least some of the ducts 18 run in parallel by the water and in correspondence of a plane perpendicular to the direction of the water flows, there are bulkheads 30 having an adequate number of calibrated circular holes 31 (or calibrated slots ) whose dimensions are determined in such a way as to obtain water flows equally distributed among the individual pipes 18 affected by the flow of water in the same direction.

The bulkheads 30 with the relative calibrated circular holes 31 can be obtained in one piece with the main body 11 during the same die-casting operation.

In fact, in the absence of such perforated bulkheads 30 there would be preferential flows in some ducts 18 with respect to others forming part of the same `` block '' of parallel channels, with a consequent worsening of the overall heat exchange between the exhaust gases and the water in transit.

For example, if we refer to the first four ducts 18 (figure 3, bottom left) of zone 21a, in the absence of these perforated bulkheads 30, the two ducts 18 that are closest to the inlet fitting 13a of the ™ cold water would be extremely favored with respect to the remaining two ducts 18 which are further away from this connection 13a, even triggering a recirculation of water between the outermost duct 18 and the adjacent one, with the result of penalizing the heat exchange towards the latter channels 18 maintained at a higher average temperature.

Hence the usefulness / need to ensure, as far as possible, the uniformity of the speed of the water flows in the various ducts 18 through the use of the aforementioned perforated bulkheads 30.

As illustrated in Figures 2, 3, in correspondence with the combustion chamber 14 there are two through holes 35, 36 for the passage of the ignition electrode 37 and the detection electrode 38, and a window 39 for viewing the combustion chamber 14.

The main body 11 is held in position with respect to the container 13 by means of an adequate number of screws (not shown) which fix it to the latter.

In this way it is possible to disassemble the burner 50 from the heat exchanger 10 making sure that the heat exchanger 10 itself remains assembled in any case.

Preferably, but not necessarily, the internal surfaces of the channels 15 crossed by the exhaust gases are undulated so as to increase the exchange surface on the exhaust gas side with the same size of each individual channel 15.

Furthermore, a plurality of pairs of inserts 12 are placed in the channels 15 crossed by the exhaust gases, having walls which are in turn wavy so as to form an interspace, measured in the direction of the exhaust gas flow, of uniform thickness and sufficiently small to forcing every smallest portion of the exhausted gases to lick the walls of the channels 15 and release heat by forced convection.

Each insert 12 has dimensions and shapes such as to allow it an adequate coupling with the respective channel 15. Furthermore, as shown in figure 2, a first insert 12 of each pair is inserted in the respective channel 15 from above, while an identical second insert 12, which completes the pair, is inserted in the same channel 15 from below.

Each insert 12 has on its surface an adequate number of protruding fins 41 (figure 8), with respect to the adjacent corrugated surfaces of the channel 15 in which it is inserted, so as to come into contact with the corresponding corrugated surface of the channel 15 and transmit for conduction the heat collected by the exhaust gases.

By using the inserts 12, a significant improvement in the exhaust gas / water heat exchange is achieved by acting on two levels:

- on the one hand, the quantity of heat transmitted by conduction is increased between the inserts 12 which heat up and the surfaces of the ducts 18 on which the protruding fins 41 rest;

- on the other hand, heat exchange is also improved by convection between the exhausted gases themselves in transit which, due to the conformation of the fins 41 themselves, are pushed towards the walls of the ducts 18.

We now describe the path of the fluids involved in the heat exchange.

The cold water enters the boiler 100 through the inlet fitting 13a obtained on the container 13 in the zone 21a farthest from the combustion chamber 1; the water then runs in parallel a first part of the ducts 18 of this area 21a, passes to the next block of ducts 18 in the same area through a space (of the type (SP)) left free by the ends of the exhaust gas channels 15 and the internal surface (SUPI) of the container 13; it runs in parallel with the latter ducts 18 of the same zone 21a in the opposite direction to the previous one; the water then passes to the next zone 21b through the recess 22a (figure 3) obtained in the horizontal partition 19 that separates the two adjacent zones 21a, 21b; once all the ducts of this zone 21b have been covered, the water goes back to the next zone 21c, located below the combustion chamber 13, through the recess 22c (figure 4) obtained in correspondence with the first duct 18 of this affected zone 21c by the flow of water.

The water then flows into all the ducts 18 of this zone 22c placed in series with each other, and finally rises, through the special recess 22b (figure 3), in the annular zone 21d located outside the combustion chamber 14 until reaching the hot water outlet fitting 13b.

As shown in particular in Figure 7, an air / combustible gas mixture enters the combustion chamber 14 exiting the burner 50, feeds the previously activated combustion process, transforming itself into combustion products.

The exhaust gases, in turn, transfer heat to the finned walls of the combustion chamber 14 and enter the cavities existing between the corrugated walls of the channels 15 of the heat exchanger 10 and the corresponding inserts 12, further yielding heat until the temperature is reached. dew corresponding to the atmospheric pressure and therefore condensing the vapor fraction contained in them; finally, the exhausted gases leave the cavities of the channels 15 and collect in a compartment 42 (figure 7) below the main body 11 to be sent, finally, outside the boiler 100 through the outlet 13c, while the condensate which has formed in the compartment 42 is evacuated through a suitable conduit (not shown).

According to a further embodiment of the present invention illustrated in Figures 9, 10, on the other hand, a boiler 100 * has been provided having a container 13 * with an essentially rectangular perimeter shape (PR), with the walls adequately reinforced and stiffened and with an adequate number of fixing points with screws (not shown) in order to withstand the internal pressures of the water (in this case the ducts 15 * and the ducts 18 * are parallel to the lower side of the perimeter (PR). Therefore, the channels 15 * and the ducts 18 * can be considered in a certain sense the â € œcordsâ € of the perimeter (PR) of the container 13 *.

Incidentally, the present invention can be applied to main bodies perimeter events (PR) of any shape (circular, elliptical, square, rectangular, etc.).

As shown in figure 10, the internal surface of the container 13 * has no recesses and the sealing gaskets necessary to contain the water and to divert the water flows inside it are assembled on the main body 11 * substantially in the same way seen for the first embodiment illustrated in figures 1-8.

The main advantages of the boiler, and of the respective heat exchanger, objects of the present invention are the following:

- ease of assembly of the condensing boiler consisting of only three main devices, namely a burner, a main boiler body and a container;

- ease of making the main body of the heat exchanger by means of a simple aluminum die casting;

- ease of making the container by means of a simple die-casting in aluminum or in a plastic material;

possibility of obtaining the bulkheads in one piece with the relative calibrated holes during the die-casting process relative to the main body;

- possibility of eliminating unwanted water recirculation inside the heat exchanger, minimizing the risk of boiling water in the heat exchanger itself;

- possibility of obtaining an optimal exhaust gas / water heat exchange by adopting a substantially vertical flow, from top to bottom, of the exhaust gases combined with a substantially horizontal flow of the water to be heated; And

- possibility of obtaining an optimal heat exchange by adopting inserts in the exhaust gas passage channels, inserts that have an adequate number of protruding fins on their surface.

Claims (12)

CLAIMS 1. Heat exchanger (10; 10 *), in particular for condensing boilers (100; 100 *), comprising two components assembled together: - a main body (11; 11 *); and - a container (13; 13 *); heat exchanger (10; 10 *) characterized by the fact that said main body (11; 11 *) is formed in a single piece, and has a first plurality of channels (15; 15 *) for the passage of exhaust gas according to a first direction (F1), and a second plurality of conduits (18; 18 *) for the passage of water whose fluid threads flow in accordance with second directions (F2), called second plurality of conduits (18; 18 * ) being arranged in a labyrinth, and in such a way that said second directions (F2) are substantially perpendicular to said first direction (F1). 2. Heat exchanger (10; 10 *), as claimed in claim 1, characterized in that said main body (11; 11 *) is obtained from a single aluminum die-casting operation. 3. Heat exchanger (10; 10 *), as claimed in any one of the preceding claims, characterized in that each channel (15; 15 *) crossed by the exhaust gases is defined by a pair of vertical baffles (17a, 17b ; 17a *, 17b *) substantially parallel to each other, which in plan are strings parallel to each other by a perimeter (CIR; PR) of any shape enclosing said main body (11; 11 *). 4. Heat exchanger (10; 10 *), as claimed in claim 3, characterized in that each pair of said vertical baffles (17b, 17a; 17b *, 17 ° *) further defines a duct (18; 18 *) of the water closed above and below by walls substantially parallel to each other. 5. Heat exchanger (10; 10 *), as claimed in any one of the preceding claims, characterized in that in said main body (11; 11 *) dividers (19, 20; 19 *) are provided, which along with the inner wall (PARI; PARI *) of said container (13; 13 *), they delimit areas (21a, 21b, 21c, 21d) within which the passage of water takes place, which is forced to travel through said zones (21a, 21b, 21c, 21d; 21a *, 21b *) in directions substantially perpendicular to said channels (15; 15 *) crossed by the exhaust gases. 6. Heat exchanger (10), as claimed in claim 5, characterized in that recesses (22a, 22b, 22c) having the purpose to allow the passage of water between one area (21a, 21b, 21c, 21d) and the other. 7. Heat exchanger (10; 10 *), as claimed in claim 6, characterized by the fact that the water also flows in a cavity (INT; INT *) defined, on one side, by the internal surface (SUPI ; SUPI *) of said container (13; 13 *), and, on the other, by recesses (22a, 22b, 22c) and spaces ((SP1), (SP2), SP3), (SP4), ( SP5)) left empty by said channels (15; 15 *), which do not always rest on said internal surface (SUPI; SUPI *) of said container (13; 13 *). 8. Heat exchanger (10; 10 *), as claimed in any one of claims 5-7, characterized in that the water preferably flows in directions (F2) substantially perpendicular to the direction (F1) of gas flow exhausted, with paths in parallel or in series within each single zone (21a, 21b, 21c, 21d) according to need. 9. Heat exchanger (10), as claimed in any one of the preceding claims, characterized in that in at least some of said ducts (18), and in correspondence of a plane perpendicular to the direction of the water flows, there are bulkheads (30) having openings (31) whose dimensions are determined in such a way as to obtain water flows equally divided between the individual ducts (18) affected by the flow of water in the same direction. 10. Heat exchanger (10; 10 *), as claimed in any one of claims 1-8, characterized in that a plurality of inserts (12; 12 *) provided with protruding fins (41; 41 *) which touch the walls of said ducts (18; 18 *). 11. Condensing boiler (100; 100 *) characterized in that it comprises at least one heat exchanger (10; 10 *) as claimed in claims 1-10. 12. Condensing boiler (100; 100 *), as claimed in claim 11, characterized in that it comprises only four main devices, namely a burner (50; 50 *), a main body (11; 11 *), inserts (12; 12 *) and a container (13; 13 *) of this main body (11; 11 *).