IT201600084075A1 - RADIANT DUCTS HEATING SYSTEM - Google Patents

Description

HEATING SYSTEM WITH RADIANT DUCTS

Field of application

The present invention refers to a heating system with radiant ducts, according to the preamble of the main independent claim n. 1.

The plant in question is intended to be used to heat rooms, generally large in buildings in general and, more particularly, industrial and commercial buildings, such as sheds, warehouses, hangars, supermarkets, shopping centers or other manufactured.

The plant according to the invention is therefore part of the thermotechnical sector of the production of heating and air conditioning systems.

State of the art

Radiant duct heating systems have been known and used for some time, especially in the industrial field, which include one or more closed-circuit radiant ducts adapted to be fixed to the ceiling or to a wall of a room to be heated and susceptible to be traversed internally by a heated carrier fluid, such as in particular exhaust gases mixed with burnt gases as better explained below, to heat, mainly by radiation, the underlying environment.

The radiant ducts, also referred to in the technical jargon of the sector as radiant tapes, consist of metal ducts, generally in aluminized steel, which develop inside the room to be heated with a length of a few tens of meters and in particular up to even 100-150 meters.

Such known systems generally comprise a burner adapted to heat the carrier fluid which is made to flow inside the radiant ducts. More in detail, the burner is inserted in a combustion chamber associated with the radiant ducts and is intended to be fed with a fuel and with combustion air to carry out a combustion reaction and develop hot fumes capable of being introduced into the radiant duct by heating the fluid. vector flowing in them. For this purpose, known systems also usually comprise a fan, operating on suction, adapted to circulate the vector fluid in the radiant ducts.

A heating system with radiant ducts of this known type is described for example in the IT patent 1266128. The system described therein comprises a closed circuit radiant duct formed by a delivery path and a return path, connected to each other to the respective ends to allow the circulation of a carrier fluid, in particular air and burnt gases, inside them. The system also comprises a burner inserted in a combustion chamber, which is partially housed inside an initial section of the delivery path of the radiant duct, first fuel supply means comprising jets of pressurized fuel gas connected to the burner to feed it with the fuel and second means for feeding a comburent, in particular air, associated with the burner to feed it with the comburent.

More in detail, the second feeding means comprise a feeding chamber, communicating with the combustion chamber and with the external environment, through which combustion air from the external environment is sucked into the burner.

The system also includes a fan operating on suction, which is arranged at the end of the return path of the radiant duct, near the burner. The fan of the system described therein is able to suck the carrier fluid that runs through the delivery path and the return path of the radiant duct and to blow part of this carrier fluid at the beginning of the delivery pipe to allow its recirculation.

The combustion air coming from the external environment is generally sucked into the burner due to the depression created by the jets of fuel gas under pressure inside the burner and due to the depression created by the fan on the delivery path of the radiant duct associated with the burner.

A drawback of this known heating system described in IT patent 1266128 lies in the risk of backfires.

In fact, if the depression created inside the delivery path of the radiant duct, and therefore in the combustion chamber, by the fan operating in suction is not sufficient, the burner is not able to suck in the quantity of comburent air necessary to burn the fuel. it is supplied, so that dangerous backfire phenomena may occur, with the risk of even explosions.

In order to limit the risk that such phenomena may occur, known systems of the type described above are equipped with a high-power fan, capable of ensuring the creation of a sufficient depression inside the delivery path of the radiant duct to ensure the intake of sufficient quantities of combustion air. However, this entails higher costs for the construction of the system, as well as higher maintenance and operating costs of the heating system itself.

Also known are heating systems with radiant ducts comprising a blown air burner. The latter is fed with a mixture of fuel and combustion air, which therefore reach the burner itself already premixed. The flame generated by this blown air burner is rather short, taking place over a limited space.

These last known heating systems have the main drawback of requiring high production costs since they must be equipped with a combustion chamber with optimal characteristics of resistance to thermal shocks to which the chamber itself is necessarily subjected during the operation of the system. and since they must be equipped with a fan and safety devices proper to a burner which is subject to specific and restrictive safety standards.

In the sector of the construction of radiant duct heating systems, the problem of limiting polluting agents and in particular nitrogen oxides NOx and their mixtures in the fumes emitted by the expulsion chimney is also particularly felt.

In order to limit this drawback, it is known from the patent application of the same applicant no. IT PD 2015A000036 a heating system equipped with a second fan (in addition to the one provided for the circulation of fumes) which takes air from the external environment and forcibly introduces it into a supply chamber where it mixes with the fuel to promote the combustion reaction.

The second fan is able to supply combustion air continuously and safely during the operation of the system to ensure substantially complete combustion of the fuel. The flow of combustion air blown by the second fan 8 favors a development in length of the flame generated by the burner and therefore favors a post-combustion of the recirculating vector fluid. The latter, occurring with an oxygen content lower than that necessary for complete combustion, causes a reduction in the flame temperature and therefore a reduction in the quantity of nitrogen oxides NOx and their mixtures present in the heated carrier fluid.

The latter solution has proved to be not free from drawbacks in practice and is rather expensive to implement due to the presence of a second fan. Furthermore, it does not allow the combustible mixture to be controlled precisely, especially in the post-combustion phase.

Presentation of the invention

In this situation, therefore, the object of the present invention is to overcome the drawbacks of the aforementioned known art, by providing a heating system with radiant ducts, which allows combustion to be controlled precisely by reducing the formation of polluting compounds.

A further object of the present invention is to provide a radiant duct heating system which is safe and operationally completely reliable.

A further object of the present invention is to provide a heating system with radiant ducts, which is simple and economical to make.

Another object of the present invention is to provide a heating system with radiant ducts, which is simple and inexpensive to maintain.

A further object of the present invention is to provide a heating system with radiant ducts, which has low operating costs.

Brief description of the drawings

The technical characteristics of the invention, according to the aforementioned purposes, are clearly verifiable from the content of the attached claims and the advantages thereof will be more evident in the detailed description that follows, made with reference to the attached drawings, which represent some purely exemplary embodiments. and non-limiting, in which:

Figure 1 shows a first perspective view of a heating system object of the present invention;

Figure 2 shows a second perspective view of the heating system of Figure 1 having been removed the smoke evacuation chimney to better illustrate the other characteristics;

Figure 3 shows a third perspective view of the heating system of Figures 1 and 2 having removed the smoke evacuation chimney to better illustrate the other characteristics;

- Figure 4 shows a fourth perspective view of the heating system of the previous figures, the smoke evacuation chimney and an upper casing having been removed to better illustrate the other characteristics;

- Figure 5 shows a fifth sectional view from above of the heating system of the previous figures having been removed the smoke evacuation chimney and an upper casing to better illustrate the other features;

Figure 6 shows a sixth perspective view of the heating system of the previous figures, the flue exhaust chimney and an upper casing having been removed to better illustrate the other characteristics;

Figure 7 shows a detail of the system according to the invention relating to a shutter in the open position;

- Figure 8 shows the detail of the system of Figure 7 with the shutter in the closed position.

Detailed description

With reference to the accompanying drawings, 1 has been indicated as a whole with the radiant duct heating system, object of the present invention.

The heating system 1 according to the invention is intended to be used to heat rooms of large cubic volume, or characterized by large surfaces usually in industrial or commercial buildings, such as sheds, hangars, warehouses, supermarkets, shopping centers, cinemas or similar.

In particular, unit 1 according to the present invention is intended to be installed inside or outside the room to be heated at a distance from the ground and with a suitably chosen orientation to ensure the desired heating of the whole room or of a selected area of the room. .

The heating system 1 object of the present invention comprises at least a radiant duct 2, connected at its ends by means of an initial section 2 'and a final section 2 "to an operating unit 100. The latter generates, by means of a vector flow F which it is circulated in a closed circuit composed of the radiant duct 2 and a first recirculation compartment 102 of the central 100, as clarified later in the present description.

The radiant duct 2 can be fixed to the ceiling or to a wall of a room to be heated, and is kept suspended and spaced from the ground, and is able to be traversed internally by a heated vector fluid F, to heat the room by radiation. same.

Obviously the radiant duct 2, instead of being fixed directly to the ceiling or to a wall, can also be fixed to beams or to columns or poles or to any structure capable of safely supporting the radiant duct 2 itself and therefore the system 1, without thereby departing from the scope of protection defined by this patent. The aforesaid radiant ducts 2, also referred to in the technical jargon of the sector with the term radiant tapes, are formed by metal ducts which develop with a length of some tens of meters and in particular up to 100-150 meters.

Advantageously, the aforementioned radiant ducts 2 are obtained starting from a continuous strip of metal material, for example of aluminized steel, which is formed in a spiral and fixed along its longitudinal edges in such a way as to create a tubular body, according to production processes per se known to those skilled in the art.

However, regret 1 illustrated in the attached figures and described in detail below preferably comprises a single radiant duct 2, of which, as mentioned, only the initial portion and the final portion connected to the operating center 100 are shown in the attached drawings, which through a compartment connector connects them in a closed circuit. More in detail, the radiant duct 2 of the system 1 illustrated in the attached figures comprises a distance section and an approach section with respect to the operating center 100, parallel to each other and connected at the distal end of the control unit 100 by a U-shaped fitting not shown. to allow the circulation of the vector fluid F inside them.

The operating center 100 of the plant 1 in accordance with the present invention also comprises at least the aforementioned burner 3, which is mounted inside a box-shaped body 101 of the same operating center 100 and is connected thanks to its combustion chamber , at the initial section 2 'of the radiant duct 2. The burner 3 is provided with a combustion chamber, in which a mixture of a fuel C and a comburent D is burned to generate, by means of a combustion reaction, combustion products P at high temperature suitable for being mixed with the vector fluid F which already flows internally through the radiant duct 2 to heat it.

The plant 1 is also provided with first means 4 for supplying the fuel C connected to the burner 3 to supply the latter with a flow rate of fuel C. The latter may be in gaseous form, and consist for example of methane, or it may be in liquefied form, and for example consist of LPG.

The first feeding means 4 may comprise a single-stage, two-stage or modulating valve assembly, ie capable of varying the quantity of fuel C according to the request of the environment to be heated.

Secondary means 5 for feeding the comburent associated with the burner 3 are also provided to feed it with the comburent D. The latter is preferably made up mainly of air, as better explained below.

The means for feeding the combustion agent D of the plant 1, according to the invention, comprise a fan 6 also housed in the box-like containment body 101 of the operating center 100. It is provided with a motor 60 and two fans indicated below as first impeller 61 and second impeller 62 connected to motor 60 by means of a common transmission shaft 63 to which they are keyed in succession spaced apart from each other. The first fan 61 is arranged in correspondence with the final section 2 "of the radiant duct 2 to create a depression throughout the radiant duct 2 arranged upstream so as to suck the vector fluid F from the initial section 2 'of the radiant duct 2. in this way, the vector fluid F circulates in a closed circuit comprising the radiant duct and completed by the connection compartment 102 arranged inside the box-like body for connection between the initial and final sections of the radiant duct 2.

Therefore, the first impeller 61 of the fan 6 is adapted to suck the vector fluid F from the radiant duct 2 and to blow this vector fluid F under pressure towards the inlet section 2 'through the connection compartment 102 and thus reintroduce the same vector fluid F. An expulsion chimney 80 is connected to the connection compartment 102 to expel part of this vector fluid F pushed under pressure by the first fan 61.

According to the invention, the box-like containment body 101 comprises at least a first dividing wall 103, which defines, together with the box-like body 101, the aforementioned first recirculation compartment 102, which connects the initial section 2 to each other. 'is the final section 2 "of the radiant duct 2 and houses the first fan 61 operating in suction to force the vector fluid F from the final section 2" to the initial section 2' thus making the vector fluid F circulate inside the radiant duct 2 , in a closed loop.

The box-like containment body 101 also comprises at least a second dividing wall 104, which, together with the first dividing wall 103, defines a second compartment 105 for supplying combustion air, in connection with the external environment. This second compartment 105 communicates with the burner 3, or with its combustion chamber 30, by means of at least a first opening 106 obtained in the first dividing wall 103 and houses the second fan 62 to force combustion air sucked from the external environment into the burner 3.

In accordance with the idea underlying the present invention, the first dividing wall 103 comprises at least a second opening 107 which places the first recirculation compartment 102 in communication with the second air supply compartment 105. The second fan 62 housed in the second compartment 105 is therefore capable of sucking into the latter through the aforementioned second opening 107 a fraction of the vector fluid F (and therefore of burnt gases) passing through the first recirculation compartment 102 to force it together with the combustion air sucked from the external environment into the burner through the first opening 106.

Advantageously, to allow an optimal suction and delivery action by the second fan 62, the second compartment 105 is divided by at least one internal wall 108, into a suction chamber 105 ', connected to the first compartment 102 by means of the second opening 107, and from a delivery chamber 105 "connected to the burner 3 by means of the first opening 106. The second fan 62 sucks the fraction of burned gas from the first compartment 102 which then injects into the burner 3 through the first opening 106 into the combustion chamber of the burner 3 , together with a flow of combustion air coming from the external environment (in particular through the opening 115 described below).

Advantageously, the aforesaid internal wall 108 comprises a first wall 108 'facing the first dividing wall 103 in front of the second opening 107, and a second wall 108 "placed in continuity with the first wall 108' and substantially facing a fourth opening 115 obtained in the body box 101 and in connection with the external environment.

There is also advantageously a third heating compartment 109, which is in communication with the external environment, is located adjacent to the first compartment 102 and is equipped with a third opening 110 in communication with the second compartment 105 to supply it with aspirated combustion air. from the preheated external environment in the third compartment 109.

More in detail, this third heating compartment 109 is preferably in the form of a duct placed at least partially around the first compartment 102, delimited by the containment body 101, by an at least partially annular wall 111, which faces the containment body 101, and from a peripheral edge 112 of the first dividing wall 103. The third opening 110 is formed in correspondence with the aforementioned peripheral edge 112 of the first dividing wall 103.

Advantageously, the second opening 107 which connects the first compartment 102 to the suction chamber 105 'of the second compartment 105 to allow the suction of a fraction of burnt gas by the second fan 62, is obtained with a plurality of side-by-side holes obtained on the first partition 103; similarly, also the third opening 110 to allow suction from the third compartment 109 always in the suction chamber 105 'of the second compartment 105 is obtained with a plurality of side-by-side holes, obtained on the peripheral edge 112 of the first dividing wall 103, preferably above of the plurality of holes of the second opening 107.

In accordance with a possible embodiment of the invention, the fourth opening 115 connects only the external environment with the third heating compartment 109, which in turn is connected to the second compartment 105 with the third opening 110 substantially located at the end of the duct defined by the third compartment 109 itself to force the external air to flow inside at least part of the duct of the third compartment 109 adjacent to the first hot compartment 102 before passing through the third opening sucked in by the second fan 62 of the fan 6. For this purpose, the duct of the third compartment 109 can be closed, for example with a closing wall 117 illustrated only in Figure 106, immediately after the third opening 110 at the opposite end with respect to the fourth opening 115 so as to force the external air to run through the entire duct of the third compartment 109.

In accordance with a preferential embodiment of the present invention, the fraction of burnt gas sucked through the second opening 107 from the first recirculation compartment 102 is adjustable. This allows the correct mixture of fuel and comburent to be calibrated in the burner 3 by introducing the correct fraction of burnt gases (therefore having little oxygen), which allows combustion to be obtained with the formation of reduced quantities of NOx. As is known, in fact, a slightly oxygen-poor combustion allows, if correctly calibrated, to reduce the formation of polluting compounds and in particular of NOx. However, if the amount of oxygen is reduced too much, for example due to an excessive addition of the flue gas fraction, the combustion leads to the formation of carbon monoxide which is also undesirable. By intercepting in an adjustable manner the passage of the fraction of burned gases sucked in by the second opening 107, it is possible to very finely adjust the mixture and therefore to control the combustion products in an optimal way.

For this purpose, the system 1 according to the invention advantageously comprises at least a first shutter 113, which is operated by a first actuator 114 to close / open the aforementioned second opening 107, in particular in an adjustable manner.

The box-like containment body 101 also includes the fourth opening 115, mentioned above, which puts the second compartment 105 in communication with the external environment.

This fourth opening 115 is for example obtained on a side wall of the containment body 101 to introduce air from the external environment directly into the suction chamber 105 'of the second compartment 105. Otherwise it can be made, also always on the same side wall of the body. containment 101, but moved at least partially in front of the third compartment 109 so as to introduce external ambient air into this third compartment in which the air heats up in contact with the walls delimiting the first compartment 102 before passing through the third opening 110 and re-entering heated in the suction chamber 105 'of the second compartment 105

In accordance with the embodiment illustrated in the attached figures, the fourth opening 115 is obtained on a wall of the containment body 101 and connects the external environment with the second compartment 105 and with the third compartment 109, in particular being divided into two start from the first partition 103.

Advantageously, the system 1 according to the invention also includes a second shutter, which is operated by a corresponding second actuator to close / open the aforementioned fourth opening 115.

In accordance with an embodiment not shown, the first and second actuators may coincide as well as the first and second shutter; in this case the second and third opening will be contiguous so that a single actuator can operate a single shutter in closing the second opening and simultaneously in opening the third opening and vice versa it can operate the shutter in opening the second opening and simultaneously closing the third opening .

For example, it may be envisaged that the flow of new hot fumes produced by the burner is of the order of 5-30% of the vector flow recirculating in the radiant duct 2 and in the first recirculation compartment 102. Furthermore, for example, the comburent D can be composed from 5-40% of vector fluid sucked by the first compartment 102 being the remaining part constituted by ambient air.

The technician of the sector, also through experimental tests and checks on the gases produced by the burners, will be able to optimize the percentages indicated above even with different values.

Finally, as shown by the attached figures, the second dividing wall defines with the box-like body a technical compartment 116, containing the motor 60 of the fan 6 as well as the first means 4 for supplying the comburent C and the provided an electronic control unit of the implant 1.

The aforesaid technical compartment 116 being separated from the first warm compartment 102 for circulation of the vector flow F from the second compartment 105 in which mainly ambient air flows, will be substantially cold and therefore will not require particular insulation for the motor 60, the first supply means 4 combustion agent C and an electronic control unit is provided.

Thanks to the present invention it is possible to produce a mixture of fuel and comburent capable of limiting the formation of pollutants in the combustion fumes and thanks to the use of at least one damper it is possible to carry out a very fine adjustment of the fraction of combustion gases which it is sent back to the combustion chamber or also by the quantity of ambient air that is always sent to the combustion chamber.

The use of a second fan 62 allows a constant supply of the combustion fluid with advantages both for the quality of combustion and for the efficiency of the radiant belts.

The choice of keying the two fans 61, 62 onto a single shaft 63 of a common motor also allows to obtain a compact and economically advantageous system to be built.

The invention thus conceived therefore achieves the intended aim and objects.

Obviously, in its practical embodiment, it may also assume forms and configurations different from the one illustrated above without thereby departing from the present scope of protection.

Furthermore, all the details can be replaced by technically equivalent elements and the dimensions, shapes and materials used can be any according to the needs.

Claims (11)

CLAIMS 1. Radiant duct heating system, which includes: at least one radiant duct (2) capable of being fixed to the ceiling or wall of a room to be heated and capable of being internally traversed by a heated vector fluid (F), from its initial section (2 ') to its section final (2 ”), to heat said room by irradiation; an operating unit (100) to generate the vector flow (F), connected to the two initial and final sections (2 ', 2 ") of said radiant duct (2) to create with it a closed circuit and comprising a box-like containment body (101); at least one burner (3) housed in said box-like containment body (101), associated with the initial section (2 ') of said at least one radiant duct (2), capable of burning a mixture of a fuel (C) and a comburent (D) to generate, by means of a combustion reaction, high temperature combustion products (P) suitable for being mixed with said carrier fluid (F) to heat it; first means (4) for feeding said fuel (C) connected to said at least one burner (3) to feed it with said fuel (C); second means (5) for feeding said comburent (D) associated with said at least one burner (3) to feed it with said comburent (D), comprising at least one fan (6) equipped with a motor (60), with a first fan (61) and a second fan (62) both connected to said motor (60) by means of a common transmission shaft (63); said a box-like containment body (101) comprising at least a first dividing wall (103), which, together with said box-like containment body (101), defines a first recirculation compartment (102) capable of connecting the initial section to each other (2 ') and the final section (2 ") of said radiant duct (2), and housing said first fan (61) operating in suction to force said vector fluid (F) from said final section (2") to said section initial (2 ') and then to circulate said vector fluid (F) inside said radiant duct (2); - at least a second dividing wall (104), which together with said first dividing wall (103) delimits a second air supply compartment (105) in connection with the external environment, and equipped with at least a first opening (106) of communication with said burner (3) formed in said first dividing wall (103); said second compartment (105) housing said second fan (62) to force combustion air sucked from the external environment into said burner (3); characterized in that said first partition wall (103) comprises at least a second opening (107) which places said first compartment (102) in communication with said second compartment (105), said second fan (62) being capable of sucking in said second compartment (105) through said second opening (107), a fraction of said carrier fluid (F) passing through said first compartment (102) to force it together with the combustion air drawn from the external environment into said burner (3) through said at least one first opening (106). 2. Heating system according to claim n. 1, characterized in that said second compartment (105) is divided by at least one internal wall (108) into a suction chamber (105 '), connected to said first compartment (102) by means of said at least one second opening (107), and from a delivery chamber (105 ") connected to said burner (3) by means of said at least one first opening (106). 3. Heating system according to claim n. 1, characterized in that it comprises at least a third heating compartment (109), which is in communication with the external environment, is located adjacent to said first compartment (102) and is equipped with at least a third opening (110) in communication with said second compartment (105) to supply it with combustion air sucked from the external environment preheated in said third compartment (109). 4. Heating system according to claim n. 3, characterized in that said third heating compartment (109) is a duct placed at least partially around said first compartment (102), delimited by said containment body (101), by an at least partially annular wall facing away from said body containment (101), and by a peripheral edge (112) of said first dividing wall (103). 5. Heating system according to claims no. 3 and 4, characterized in that said at least one third opening (110) is formed in correspondence with the peripheral edge (112) of said first dividing wall (103), and is in particular obtained from a plurality of through holes. 6. Heating system according to claim n. 1, characterized in that it comprises at least a first shutter (113) operated by a first actuator (114) to close / open said second opening (107), in particular in an adjustable manner. 7. Heating system according to claim n. 1, characterized in that said box-like containment body (101) includes a fourth opening (115) in communication with the external environment, which is at least partially in communication with said second compartment (105). 8. Heating system according to claim 7, characterized in that said fourth opening (115) is at least partly in direct communication with said third compartment (109), through which and through said third opening (110) it is in communication with said second compartment (105); in particular being divided into two parts by said first partition wall (103), one of which in communication with said second compartment (105) and one in communication with said third compartment (109). 9. Heating system according to claim n. 7, characterized in that it comprises a second shutter, which is operated by a corresponding second actuator to close / open said fourth opening (115). 10. Heating system according to claims no. 6 and 9, characterized in that said first and second actuators coincide and said first and second shutter coincide; said second and third opening being contiguous and intercepted in an adjustable way by said common damper so that the latter is capable of being activated in closing the second opening and simultaneously in opening the third opening and vice versa in opening the second opening and simultaneously closing the third opening. 11. Heating system according to claim n. 1, characterized in that said second dividing wall delimits with said box-like body a technical compartment containing the motor of said fan, a gas blowing unit and an electronic control unit.