RU2849787C2 - Heat exchanger - Google Patents

Abstract

FIELD: heat exchanger.

SUBSTANCE: heat exchanger (1, 1') comprises: a gas-tight casing (2), at least one tube (4) made of a material with good thermal conductivity, inside which a fluid medium intended for heating can circulate, wherein said tube (4) is wound in a spiral shape, forming a spiral winding (40) with a longitudinal axis (X-X') located inside said casing (2), means for supplying and/or producing hot gases inside said casing (2), such as a burner (3), to form a combustion chamber (26) therein, this spiral winding (40) being designed to leave a gap (45) between two adjacent turns, said at least one tube (4) having opposite front (41) and rear (42) sides, an inner surface (43) facing the longitudinal axis (X-X’) and an outer surface (44) facing the casing (2), wherein said front side (41) and said rear side (42) are flat or substantially flat and are located on both sides of the gap (45).

EFFECT: one tube (4) has on its front side (41) and/or on its rear side (42) a shoulder (46) on its front side (41) and/or on its rear side (42), which extends from the inner surface (43) of the tube towards its outer surface (44) over part of the height (H1) of the cross-section of this tube (4), as well as over the entire length or almost the entire length of this tube (4).

7 cl, 7 dwg

Description

Field of technology to which the invention relates

The invention relates to the field of heat exchangers, in particular, heat exchangers used to produce industrial hot water or water for a heating network.

More specifically, the invention relates to a heat exchanger comprising a casing, means for supplying and/or producing hot gases within this casing, forming a combustion chamber, and at least one spirally wound tube, which is located in this combustion chamber and within which a fluid medium, such as water, intended for heating, circulates.

State of the art

Such a heat exchanger is already known from prior art. In this type of heat exchanger, the spiral winding of the tube is designed in such a way as to leave a small gap between adjacent turns. Hot gases generated within or fed into the winding pass through these gaps from the inside to the outside of the heat exchanger and are then removed through a designated exhaust pipe.

As hot gases pass through these gaps, they heat the walls of the tube turns located on both sides of the gap and also heat the fluid circulating in the tube.

However, it is noted that, in particular in the case where the tube has an elongated cross-section with a flat or substantially flat front side and back side, the space between two adjacent turns can become contaminated and even clogged over time, as slag, that is, soot and unburned particles carried by hot gases, settles in it.

This complete or partial clogging of some gaps leads to an increase in the pressure of the gases circulating inside the combustion chamber, which requires an increase in the speed of the fan that forces the air/fuel mixture into the burner or forces hot air into the chamber, and, consequently, an increase in the electrical consumption of this fan.

This clogging of some gaps also leads to a reduction in the heat exchange area between the fluid medium intended for heating and the hot gases and, consequently, to such heating of the fluid medium circulating in the tube that is not uniform along its length and leads to a decrease in the efficiency of the heat exchanger.

In addition, the efficiency of the heat exchanger decreases over time as the gaps become contaminated.

Finally, given this clogging, it's also necessary to regularly clean these spaces. This maintenance operation is time-consuming and labor-intensive.

Document US 2015/0153067 already discloses a heating apparatus equipped with a door with a built-in burner. This apparatus contains a tube within which a heating fluid can circulate. This tube is wound in a spiral, forming a helical winding, the turns of which are spaced apart by a distance that allows the passage of hot gases produced by the burner. These distances are calibrated using dotted bosses formed on one of the flat sides of the tube, as shown in the figures in this document.

However, this document does not mention or describe the implementation of a shoulder for collecting soot and slag on the front and/or rear side of this tube on a portion of the height of the cross-section of this tube from the side of the inner surface of the tube and along the entire length of the tube or almost along the entire length of the tube.

Document EP 3 141 838 also discloses a heat exchanger containing a coiled tube located inside a closed chamber and surrounding a burner. The spacing between the coils is calibrated using a toothed comb located on the outer surface of the tube.

This tube also has numerous fins on its inner surface, designed to increase the contact surface and heat exchange between the hot gases produced by the burner and the tube, and consequently, the fluid circulating within it to be heated. These fins are located on the ends of the tube's inner surface (on its small sides).

This document does not describe the shoulder on the front and/or back of the soot and slag collection tube.

Disclosure of the essence of the invention

The invention is intended to propose a heat exchanger that allows solving the above-mentioned problems and, in particular, limiting contamination of the spaces between two adjacent turns of the tube of this heat exchanger.

In this regard, the object of the invention is a heat exchanger comprising:

- a gas-tight casing equipped with a sleeve for removing gaseous combustion products,

- at least one tube made of a material with good thermal conductivity, inside which a fluid medium intended for heating, such as water, can pass, and this tube is wound in a spiral so as to form a spiral winding with a longitudinal axis X-X’, and this winding is located inside the said casing,

- means for supplying and/or producing hot gases within said housing, such as a gas or liquid fuel burner, to form a combustion chamber therein,

and this spiral winding is made in such a way that it leaves a gap between two adjacent turns,

wherein said at least one tube has an opposite front side and a rear side, an inner surface facing the longitudinal axis X-X’ and an opposite outer surface facing the casing, wherein said front side and said rear side are flat or substantially flat and are located on both sides of the gap.

According to the invention, said at least one tube has a shoulder on its front side and/or on its back side, wherein this shoulder extends from the inner surface of the tube in the direction of its outer surface over a portion of the height of the cross-section of this tube, and this shoulder also extends either along the entire length of said at least one tube located in said combustion chamber, or along the entire length of said at least one tube located in said combustion chamber, with the exception of the first or last turn of the spiral winding, and each gap between two adjacent turns is calibrated either by means of a comb tooth inserted into the gap between two turns from the side of the outer surface of the tube, or by means of several projecting elements, such as lugs, made on the front side and/or on the back side of said at least one tube, wherein each projecting element made on a turn of the tube rests respectively on the back side and/or the front side of the adjacent turn in such a way that the shoulder allows to collect soot and slags carried away by hot gases that pass through the gaps.

This shoulder collects soot or slag produced by the burner's combustion gases, while keeping the space between the two adjacent turns open. Hot gases can continue to pass through this space and heat the water circulating in the spiral winding.

Therefore, this shoulder allows to slow down the rate of coil fouling, limit the increase in pressure in the combustion chamber, avoid excessive electrical consumption of the heat exchanger, maintain the efficiency of the heat exchanger and increase the intervals between maintenance/cleaning operations performed on the heat exchanger tube.

According to other preferred and non-limiting features of the invention, considered separately or in combination:

- the shoulder extends along a height measured from the inner surface, which is approximately one third of the height of the cross-section of the tube.

- the gap between two adjacent turns, measured where the shoulder(s) are(are) located, is wider than the gap between two adjacent turns, measured where there is no shoulder.

- a disc-shaped reflector is installed inside the spiral winding, hermetically sealed with respect to gases, and this disc-shaped reflector forms a condensation chamber inside the casing, which is located between the said disc-shaped reflector and the bottom of the casing, and a combustion chamber, which is located between the said disc-shaped reflector and the front part of the casing, on which a door is installed, containing the said means for supplying and/or producing hot gases, and the shoulder is made exclusively on the tube, or on the tubes, or on a section of the tube, which is located in the combustion chamber.

- the gap between two adjacent turns is calibrated by means of several projecting elements, such as bosses, made on the front side and/or on the back side of said at least one tube, wherein each projecting element made on a turn of the tube rests respectively on the back side and/or on the front side of the adjacent turn, and each projecting element is made on a part of the front side and/or the back side that does not contain a shoulder.

- the gap between adjacent turns is calibrated by means of several projecting elements, such as bosses, made on the front side or on the back side of said at least one tube, wherein the projecting elements and the shoulder are made on opposite sides of the tube, wherein the projecting elements rest on a section of the side of the tube that does not contain the shoulder.

- the specified tube is hydroformed.

Brief description of the drawings

Other distinctive features, objects and advantages of the invention will be more apparent from the following description, which is purely illustrative and not restrictive and which should be read with reference to the accompanying drawings, in which:

Fig. 1 shows the claimed heat exchanger, in which there is only a combustion chamber, a longitudinal sectional view;

Fig. 2 shows a part of the tube of the claimed heat exchanger, a perspective view;

Fig. 3 shows a condensation heat exchanger according to the invention, a longitudinal sectional view;

Fig. 4 shows a comb, perspective view;

Fig. 5 shows in detail three turns of a tube in accordance with the invention, with the section being made at the level of the tides, cross-sectional view.

Fig. 6 shows in detail three turns of a tube in accordance with the invention, with the cut being made at a point of the tube that does not have lugs, a cross-sectional view;

Fig. 7 shows in detail three turns of a tube according to another embodiment of the invention, in cross-sectional view.

Implementation of the invention

The following is a description of the first embodiment of the invention, with reference to Fig. 1, which depicts a heat exchanger 1 containing only a combustion chamber. In this figure, it is shown in its normal position of use.

This heat exchanger 1 comprises a casing 2, means for supplying and/or producing hot gases within said casing, and at least one tube 4, within which a fluid medium, in particular water, intended for heating, circulates. This water circulation is ensured by a pump, not shown in the figures.

Casing 2 has a general tubular shape and is located along the longitudinal axis X-X'. As is known, in its upper portion, it has a sleeve 21 for removing gaseous combustion products and in its lower portion, an outlet opening connected to a condensate removal channel 22.

The casing 2 is closed at its rear end by a bottom 23, equipped on its inner side with a disk 230 made of heat-insulating material.

In the front part of the casing 2, a front part 24 is fixed. It contains a central opening, designed with the possibility of being closed by a door 25.

Tube 4 is made of a heat-conducting material, such as metal. It is wound in a spiral, forming a helical winding 40, and is positioned within casing 2 such that its longitudinal axis X-X' coincides with the longitudinal axis X-X' of casing 2.

The means for producing hot gases preferably comprises a burner 3, such as a gas or liquid fuel burner. This burner 3 is preferably tubular and is located within the casing 2 and within the winding 40 such that its longitudinal axis X-X' coincides with the longitudinal axis X-X' of the casing 2.

Burner 3 is fixed on the inside of door 25.

The means for supplying hot gases (not shown in the figures) comprise a burner located outside the heat exchanger and a fan secured to the door 25 for forcing hot gases into the casing 2 into the spiral winding 40.

Thus, the space located inside the winding 40 forms a combustion chamber 26.

Tube 4 has two ends, forming an inlet and an outlet, through which the fluid to be heated is supplied and removed, respectively. One of these outlets 400 is shown in Fig. 2.

Tube 4 has an elongated cross-section, which may be oval or rectangular, or rectangular with small sides that may be protruding and curved (as shown in the figures) or may be protruding and V-shaped.

Thus, the tube 4 has opposite front side 41 and rear side 42.

Conventionally, in the further text of the description and in the claims, the term “front side” denotes the side facing forward of the heat exchanger, that is, toward the front part 24, while the term “rear side” denotes the side facing backward of the heat exchanger, that is, toward the bottom 23.

In addition, the tube 4 has an inner surface 43 facing the axis X-X’ and the combustion chamber 26 (or the burner 3, when present), and an opposite outer surface 44 facing the casing 2. These inner 43 and outer 44 surfaces correspond to the small sides of the tube 4.

Preferably, as shown in the figures, the front 41 and rear 42 sides are flat and parallel to each other. However, depending on the cross-sectional shape of the tube 4, these front 41 and rear 42 sides may not be strictly flat, but only substantially flat (e.g., slightly curved).

Preferably, in order to simplify the connection of the winding 40 between the front part 24 and the bottom 23 or the disk 230, the winding of the tube 4 is performed in such a way that the major axis Y-Y' of the cross-section of the tube is perpendicular to the longitudinal axis X-X' of the helical winding 40. However, this major axis Y-Y' may also be slightly inclined relative to the longitudinal axis X-X' of the helical winding 40, without going beyond the scope of the invention.

The spiral winding 40 has a series of adjacent turns, and between two adjacent turns there is a gap 45, the value of which is calibrated, as will be described below. Inside this winding 40, the front side 41 and the back side 42 of the tube 4 are located on either side of the gap 45, as shown in Figs. 1 and 3.

Hot gases exit combustion chamber 26, passing through gaps 45 in an inside-out direction, as shown by arrows i. In doing so, they heat the walls of tube 4, particularly the front 41 and rear 42 sides, and consequently the water circulating in this tube. The gases are then expelled through sleeve 21 (see arrows ii).

According to the invention, as shown more clearly in Fig. 2, 5 and 6, the tube 4 has on its front side 41 and/or on its rear side 42 a shoulder 46. This shoulder 46 extends from the inner surface 43 in the direction of the outer surface 44 on a portion of the height H1 of the cross-section of the tube 4.

In Fig. 2 it is evident that this shoulder 46 extends along a height H2 (measured from the inner surface 43), which is less than the height H1. In other words, as shown in Fig. 5 and 6, taking into account the presence of the shoulder 46, the outer width L2 of the cross-section of the tube 4, measured at the level of the shoulder 46, is less than the outer width L1 of the cross-section of the tube 4, measured in the part of the tube where there is no shoulder 46.

Preferably, the height of H2 is approximately one third of the height of H1.

The shoulder 46 may extend along the entire length of the tube 4. Preferably, as shown in Fig. 2, this shoulder 46 is continuous.

However, it may preferably not extend along this entire length (but only along almost the entire length), in particular, it may not extend on the first and/or on the last turn of the winding 40, in order to simplify the installation of this winding in the casing 2. Thus, for example, in Fig. 1 it can be seen that the first turn of the winding, pressed against the front part 24, does not have this shoulder 46. The same may apply to the last turn of the winding, pressed against the bottom 23 and to the plate 230 in the case when the shoulder 46 is made on the back side 42.

It is also possible to provide one shoulder 46 on the front side 41 and another shoulder 46 on the back side 42 of the tube 4, as shown in Fig. 7. In this case, the outer width of the cross-section of the tube 4, measured at the level of the shoulders 46, is designated L3, wherein L3 is less than the width L1.

The shoulder 46 makes it possible to create a niche for collecting soot and slag carried away by the hot gases passing through the spaces 45. The gap (or width) between two adjacent turns, measured at the level of this shoulder 46, is designated E1 when the shoulder 46 is present only on the front side 41 (see Figs. 5 and 6) or only on the back side 42, and is designated E2 when there is one shoulder 46 on the front side 41 and one shoulder 46 on the back side 42 (see Fig. 7).

This gap E1, E2 is thus wider than the gap (or width) E3 between two adjacent turns, measured where shoulder 46 is absent, allowing for the retention of slag in shoulder 46 while leaving room for the passage of hot gases. Consequently, winding 40 becomes contaminated less quickly, reducing the frequency of cleaning operations.

Preferably, the gaps 45 between two adjacent turns are calibrated in such a way that they are all identical, so that the hot gas flows circulating in them are uniform and so that the heating of the fluid is uniform along the entire length of the tube.

According to a first embodiment of the invention, the gaps 45 can be calibrated using one or more combs 5, such as the comb shown, for example, in Fig. 4.

This comb 5 has a plurality of parallel teeth 50. This comb 5 is located relative to the winding 40 in such a way that each of its teeth 50 enters the gap 45 from the side of the outer surface 44 of the tube 4 in order to calibrate this gap 45. Thus, each tooth 50 comes into contact with the front side 41 of one turn of the tube 4 and with the back side 42 of the adjacent turn of the tube 4. Preferably, the teeth 50 do not reach the level of the shoulder 46.

According to a second embodiment of the invention, the gaps 45 can be calibrated using protruding elements, such as bosses 47 (corrugations) formed on the front side 41 of the tube 4 (as shown in Figs. 1, 2 and 5) or on the back side 42 (not shown in the figures). These bosses are preferably evenly distributed along the entire length of the tube in order to obtain gaps 45 of constant width.

Each protruding element, formed on the front side 41 and/or on the rear side 42 of the tube 4, rests respectively on the rear side 42 and/or the front side 41 of the adjacent turn.

In the case where the bosses 47 and the shoulder 46 are made on the same front or rear side of the tube 4, for example on the front side 41, as shown in Fig. 2, then the bosses 47 are preferably made on the section 49 of the side of the tube that does not contain the shoulder 46 (see also Fig. 5).

In the case where the protruding elements (such as bosses 47) and shoulder 46 are made on opposite sides of tube 4 (for example, shoulder 46 on front side 41, and protruding elements on back side 42 or vice versa), then the protruding elements rest on section 49 of the side of the tube that does not contain shoulder 46.

A second embodiment of the claimed heat exchanger is described below with reference to Fig. 3. This figure shows a condensation heat exchanger, designated by the general reference numeral 1'.

Elements identical to those described for heat exchanger 1 have the same numerical designations and their detailed description is omitted.

This heat exchanger 1’ differs from the heat exchanger 1 in that it contains a disc-shaped reflector 6, located inside the spiral winding 40 of the tube 4 perpendicular to the axis X-X’ in such a way that it forms inside the casing 2, on the one hand, a combustion chamber 26, which is located between the door 25 and this reflector 6 and in which hot gases are produced or into which hot gases are supplied, and, on the other hand, a condensation chamber 27, which is located between the reflector 6 and the bottom 23 of the casing 2.

In this case, it should be noted that the gas removal sleeve 21 is connected to the condensation chamber 27.

The reflector 6 comprises a disk 61 made of heat-insulating material, mounted on a reinforcement made of a thin metal sheet 62, equipped with a radial peripheral flange 63.

The reflector 6 is installed inside the winding 40 of the tube 4 in such a way that its flange 63 is inserted and located hermetically with respect to the gases in the gap 45 existing between the last turn of the tube 4, located in the combustion chamber 26, and the first turn of the tube 4, located in the condensation chamber 27.

Preferably, the shoulder 46 is formed only on the turns of the tube 4 that are in the combustion chamber 26, and not on the turns of the tube that are in the condensation chamber 27.

Indeed, as indicated above, the hot gases produced by the burner 3 leave the combustion chamber 26, passing through the spaces 45 remaining in the turns of the tube 4 located in this combustion chamber 26 (see arrows i), and the slags are retained in the shoulder 46. Then the hot gases enter the casing 2 and are directed to the outer surface 44 of the turns of the tube located in the condensation chamber 27 (see arrows iii). These hot gases pass through the spaces 45 formed between the turns, this time in the direction from the outside to the inside towards the condensation chamber 27 (see arrows iv). These hot gases no longer contain slags, so there is no need for the shoulder 46.

In the two embodiments described above, heat exchanger 1 or 1' comprises a single tube 4 wound in a spiral. In the case of condensing heat exchanger 1', one portion of the turns of the single tube 4 is located in combustion chamber 26, and the other portion of the turns are located in condensation chamber 27.

However, it is possible to provide several tubes 4, each wound in a spiral and arranged next to one another so that their corresponding longitudinal axes X-X' are coaxial. In this case, the various tubes 4 are connected to each other via collectors.

In the particular case of a condensation heat exchanger 1’, one or more tubes 4 can be provided in the combustion chamber 26 and one or more tubes 4 in the condensation chamber 27.

Tube 4 can be manufactured using various methods. Two non-limiting examples of manufacturing methods are provided below.

For example, a tube can be produced by extrusion of a metal, such as aluminum extrusion.

Preferably, it can also be obtained by hydroforming.

In this regard, reference can be made, for example, to patent FR 2700608, registered in the name of the applicant.

The advantage of this method is the possibility of varying the cross-sectional profile of tube 4 along the entire spiral winding 40 and, in particular, forming shoulder 46 only on a certain part of the length of tube 4. In particular, this method makes it possible to create shoulder 46 only on the turns that are in combustion chamber 26 in the case of condensation heat exchanger 1’.

In addition, this method also makes it possible to obtain a tube in which the sides of the first turn and the last turn are flat, which allows for a simpler design of the bottom and front part of the heat exchanger.

Claims (14)

1. Heat exchanger (1, 1’) containing: - a gas-tight casing (2) equipped with a sleeve (21) for removing gaseous combustion products, - at least one tube (4) made of a material with good thermal conductivity, inside which a fluid medium intended for heating, such as water, can circulate, and this tube (4) is wound in the form of a spiral, forming a spiral winding (40) with a longitudinal axis (X-X’), and this spiral winding (40) is located inside the said casing (2), - means for supplying and/or producing hot gases inside said casing (2), such as a burner (3) on gas or liquid fuel, to form a combustion chamber (26) therein, and this spiral winding (40) is made so that a gap (45) remains between two adjacent turns, wherein said at least one tube (4) has a front side (41) and a rear side (42) opposite each other, an inner surface (43) facing the longitudinal axis (X-X’), and an opposite outer surface (44) facing the casing (2), wherein said front side (41) and said rear side (42) of the tube (4) are flat or substantially flat and are located on both sides of the gap (45), characterized in that said at least one tube (4) has on its front side (41) and/or on its rear side (42) a shoulder (46), and this shoulder (46) extends from the inner surface (43) of the tube in the direction of its outer surface (44) on a portion of the height (H1) of the cross-section of this tube (4), and this shoulder (46) also extends either along the entire length of said at least one tube (4) located in said combustion chamber (26), or along the entire length of said at least one tube (4) located in said combustion chamber (26), with the exception of the first or last turn of the spiral winding (40), wherein each gap (45) between two adjacent turns is calibrated either by means of a tooth (50) of a comb (5) inserted into the gap (45) between two turns from the side of the outer surface (44) of the tube (4), or by means of several projecting elements, such as lugs (47), made on the front side (41) and/or on the back side (42) of said at least one tube (4), wherein each projecting element made on a turn of the tube (4) rests respectively on the back side (42) and/or the front side (41) of the adjacent turn so that the shoulder (46) provides the possibility of collecting soot and slag carried away by hot gases that pass through the gaps (45). 2. A heat exchanger (1, 1’) according to claim 1, characterized in that the shoulder (46) extends along a height (H2), measured from the inner surface (43), which is approximately one third of the height (H1) of the cross-section of the tube (4). 3. A heat exchanger (1’) according to paragraphs 1 or 2, characterized in that the gap (E1, E2) between two adjacent turns, measured where the shoulder(s) (46) is(are) located, is wider than the gap (E3) between two adjacent turns, measured where there is no shoulder (46). 4. A heat exchanger (1, 1’) according to any one of paragraphs 1-3, characterized in that a disc-shaped reflector (6) is installed hermetically with respect to gases inside the spiral winding (40), wherein this disc-shaped reflector (6) forms a condensation chamber (27) inside the casing (2), which is located between the said disc-shaped reflector (6) and the bottom of the casing (2), and a combustion chamber (26), which is located between the said disc-shaped reflector (6) and the front part (24) of the casing (2), on which a door (25) is installed, containing the said means for feeding and/or producing hot gases, wherein the shoulder (46) is made exclusively on the tube (4), or on the tubes (4), or on a section of the tube (4), which is located in the combustion chamber (26). 5. A heat exchanger (1, 1') according to any one of claims 1 to 4, characterized in that the gap (45) between two adjacent turns is calibrated by means of several protruding elements, such as lugs (47), made on the front side (41) and/or on the back side (42) of said at least one tube (4), wherein each protruding element made on a turn of the tube (4) rests respectively on the back side (42) and/or on the front side (41) of an adjacent turn, wherein each protruding element is made on a part (49) of the front side and/or the back side that does not contain a shoulder (46). 6. A heat exchanger (1, 1') according to any one of claims 1 to 4, characterized in that the gap (45) between adjacent turns is calibrated by means of several protruding elements, such as bosses (47), made on the front side (41) or on the back side (42) of said at least one tube (4), wherein the protruding elements and the shoulder (46) are made on opposite sides of the tube (4), wherein the protruding elements rest on a section (49) of the side of the tube that does not contain the shoulder (46). 7. A heat exchanger (1, 1’) according to any one of paragraphs 1-6, characterized in that said tube (4) is manufactured by hydroforming.