CN115111585A

CN115111585A - Radiant strip heating device

Info

Publication number: CN115111585A
Application number: CN202210290626.5A
Authority: CN
Inventors: P·L·凯姆波尔米; S·斯珀拉尼
Original assignee: Ypresend LLC
Current assignee: Ypresend LLC
Priority date: 2021-03-23
Filing date: 2022-03-23
Publication date: 2022-09-27
Also published as: GB202204000D0; IT202100007040A1; FR3121201A1; GB2607411A

Abstract

The application discloses radiation strip heating device, the device includes: the radiation tube comprises a conveying tube, a return tube and a connecting piece for connecting the conveying tube and the return tube; a first burner for heating the fluid in the radiant tube; a fan for recirculating the heating fluid inside the radiant tube, wherein the fan comprises a volute having a delivery opening, which is directly connected to the delivery tube.

Description

Radiant strip heating device

Technical Field

The present invention relates generally to the field of heating based on the transfer of heat by radiation. More particularly, the present invention relates to a radiant strip heating apparatus.

Background

Heating systems based on the transfer of heat by radiation are known. Thus, the heating of the area within the environment is performed by emitting electromagnetic radiation in the infrared frequency range by a thermal surface (radiation surface) which is generated by and forms part of the device itself.

The advantage of these devices is that the environment is heated without having to heat all the air present. This enables the supply of heat only where needed, directly heating the radiating object, with a significant saving in energy, thus reducing losses due to emissions, and with direct effect due to low thermal inertia.

These devices are mainly used for heating large volumes of space, such as industrial warehouses, hangars, storage warehouses or commercial sites.

Radiant strip heating devices are well known devices and have been used successfully for decades in areas involving large space heating. These devices typically use as a heat source a combustible gas and/or diesel fuel that is converted by a burner into high temperature combustion products. These products are then conveyed and pushed by fans into the pipes forming the actual radiant heating circuit. The combustion products then heat the walls of the tubes of the circuit, thereby heating them to a temperature typically in the range of 150 ℃ to 350 ℃. The hot surfaces of the pipes, which have a high emission index through surface treatment, will diffuse the heat by radiation into the surrounding space, heating all objects radiated by them.

From the point of view of the overall design, these devices are generally constituted by a main unit, called burner box, which contains all the components to be used for combustion and for management and control: a recirculation chamber or plenum containing the combustion chamber with the actual burner, a main fan or recirculation fan, radiant tube connection fittings (output and return), and flue gas discharge connections. Finally, the box components are completed by an electrical control panel with electronic means for controlling and managing the machine and safety devices.

The burners used can be of different types and are associated with the use of gaseous fuel, some machines using air duct burners, in which the combustion agent (air) required for combustion is sucked in and mixed with the fuel by means of the vacuum created by the effect obtained by the circulation induced by the main recirculation fan.

In other cases, a blown air burner is used. In this case, the introduction of the combustion agent (air) is carried out by means of a fan associated with the burner, which draws air from the outside environment and introduces it into the burner head where it is mixed with the fuel.

At present, the demand for increasingly efficient and ecological machines has led to the use of new burners which have the advantage of having a much wider regulation range and of performing very clean combustion (with very low concentrations of unburnt products and pollutants, in particular with respect to nitrogen oxides or NOx).

Burners of the above type, which have been known for some time and are used for example in hot water boilers, are called "premix burners", because the fuel and the combustible air are sucked in by a fan and mixed together before reaching the burner head. The burner head generally comprises a metal cylinder with holes of various shapes and diameters, depending on the thermal power of the burner and/or of the combustion chamber inside which it is inserted. Some manufacturers of these burners have perforated metal cylinders lined with metal mesh or fabric made of metal alloy fibers that are resistant to the high temperatures generated by combustion.

Thus, the hot gases produced by combustion are introduced into the radiant circuit through the outlet nozzle. The radiant circuit, varying in length from 20m to 100 and 150m, follows a coiled path in the room to be heated, designed to cover all the areas that have to be heated. The circuit usually terminates in a U-bend and the same path is followed by a return pipe which extends alongside the transfer pipe and then returns to the burner box.

WO2006/120717 discloses a heating device with radiant tubes.

DE3814897a1 discloses a device for heating a room by means of a tube radiator.

Disclosure of Invention

The applicant has studied carefully the radiant strip heating system.

The applicant has noted that in the known systems the return pipe is connected to a plenum chamber or collection chamber in which the fume recirculation fans or main fans of the radiating strips are housed, so as to connect together the return pipe, the conveying pipe and the fume discharge pipe. The majority of the hot flue gas stream is recycled back into the radiant section. The local recirculation of the fumes is a distinctive feature of the radiant strips, which makes them distinct from the radiant tubes from which they originate, with the result that these machines are more efficient and are able to guarantee a more uniform distribution of the temperature along the whole path.

The applicant has noticed that the recirculation of the fumes into the plenum (which connects together the suction and delivery of the radiant circuit and the fume discharge pipe) is not optimal and requires difficult conditioning operations in order to correctly balance the pressure and the recirculation throughput. It usually requires the insertion of baffles to properly direct the flow, which complicates the design of the object.

The applicant has identified the object of simplifying the entire air delivery and recirculation system.

According to the invention, the plenum is no longer present inside the machine.

According to the present invention, the transfer port of the scroll of the main fan is directly connected to the transfer pipe.

According to a first aspect, the present invention envisages a radiant strip heating device comprising:

a radiant tube comprising a delivery tube, a return tube and a connector for connecting the delivery tube to the return tube,

a first burner for heating the fluid in the radiant tube,

a fan for recirculating the heating fluid inside the radiant tube,

wherein the fan includes a volute having a delivery port that is directly connected to the delivery tube.

According to an embodiment, the heating device further comprises a first combustion chamber and a first combustion head inside the first combustion chamber.

According to an embodiment, the first combustion chamber is inserted directly inside the transfer duct, in the vicinity of the transfer opening of the fan, instead of being inserted in the connecting plenum.

According to an embodiment, the first combustion chamber is inserted into the transfer tube in an intermediate position along the transfer tube, instead of into the connecting plenum.

According to an embodiment, the heating device further comprises a fume emission outlet opposite the volute of the fan.

According to an embodiment, the first combustion chamber is closed and comprises an outlet for discharging flue gases directly outwards from the first combustion chamber.

According to an embodiment, the heating device further comprises a second burner having a second combustion chamber and a second combustion head inside the second combustion chamber.

According to an embodiment, the second combustion chamber is arranged in the return conduit.

According to an embodiment, the first burner is of the air duct type or of the blown air type or of the premix type, wherein fuel and combustion air are sucked and mixed together by a fan before reaching the first combustion head.

According to an embodiment, the fan is a single inlet centrifugal fan.

Drawings

The invention will be more apparent from reading the following detailed description, provided by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a radiant strip heating apparatus according to an embodiment of the present invention;

figure 2 is a general section through a radiant circuit of a heating device according to the invention;

figure 3 is a cross-sectional view through a radiant tube module and a combustion chamber according to the present invention;

figure 3.1 is a cross-sectional view of a radiant tube module and a combustion chamber according to a first variant of the invention;

figure 4.1 is a schematic view of a radiant strip heating apparatus according to a first variant of the invention;

figure 4.2 is a schematic view of a radiant strip heating apparatus according to a second variant of the invention; and

fig. 4.3 is a schematic view of a radiant strip heating apparatus according to a third variation of the invention.

Detailed Description

The present invention contemplates a significant simplification of the overall air recirculation and delivery system. According to the invention, the plenum chamber is no longer present inside the device, since the delivery opening of the volute of the main fan will be directly connected to the delivery duct.

Thus, a combustion chamber designed with suitable dimensions according to the thermal power to be managed will be inserted directly into the delivery pipe. The associated burner will be connected to the combustion chamber. The burner can also be of the air duct type, of the blown air type or of the premixed type.

An embodiment of a radiant strip heating apparatus 10 according to the present invention will first be described with reference to fig. 1, 2 and 3.

The apparatus 10 includes a radiant tube having a delivery tube 12 and a return tube 16 connected together. For example, the delivery tube 12 and the return tube 16 may be connected together by a U-shaped connector 14, as shown in FIG. 1. As mentioned above, the transfer tube 12 and the return tube 16 may extend parallel to each other, or may extend along different paths.

The apparatus 10 further comprises a burner 20, a combustion chamber 22, a burner head 24 inside the combustion chamber 22, fuel supply means 30, means 40 for recirculating the combustion products and a flue gas outlet 50 for discharging flue gas 52.

As shown in fig. 1, the combustion chamber 22 with the head 24 of the burner is inserted directly into the transfer tube 12.

The means for recirculating the combustion products preferably comprises a fan 40. Preferably, the fan 40 is a single inlet centrifugal fan. The fan 40 includes a volute having a delivery opening.

The fuel supply 30 includes a valve 32 for intercepting fuel (e.g., gaseous fuel or diesel).

The burner 20 may be of different types. For example, it may be an air duct burner, in which the combustion agent (air) required for combustion is drawn in and mixed with the fuel by means of a vacuum created by the effect obtained by the circulation triggered by the main recirculation fan. Air 34 for combustion is indicated by arrows.

According to the present invention, the delivery port 44 of the volute 42 of the fan 40 is directly connected to the delivery pipe 12. The expression "directly connected" (or the like) means that the transfer duct is connected to the volute of the fan without a plenum or chamber. However, there may be an adapter connector and/or a washer or a plurality of washers.

This approach provides various advantages.

First, the structure of the device is significantly simplified, since the number of components is reduced.

Another particularly advantageous aspect of this solution is the increased cooling of the combustion chamber 22 due to the air flow 441, which air flow 441 is conveyed directly above the combustion chamber 22 by means of a rotational turbulent motion generated by the air exiting from the delivery opening 44 of the fan, which delivery opening 44 is directly connected to the delivery duct 12.

The invention can equally well be applied to radiant strips using any burner technology.

The invention also results in a significant improvement in the distribution/mixing of the just-burned combustion products and the recycled products along the first conveying section inside the radiant tube.

Along the first duct section, the less hot return flue gases 441 recirculated by the main fan 40 surround and help to keep the

hotter gases

201, 221 exiting from the combustion chamber in the centre of the transfer tube 12, thus preventing them from coming into contact with the walls of the transfer tube and overheating them. This effect therefore reduces the thermal stresses of the pipe along the first portion, thus increasing its working life, and also ensures a better distribution of the heat along the first portion of the path of the radiant circuit.

In this way, by inserting the combustion chamber directly inside the conveyor pipe, instead of in the plenum chamber for connection with the fan, the return pipe, the conveyor pipe and the fume emission outlet, the combustion chamber 22 can be located anywhere in the radiant circuit and/or more than one combustion chamber can be inserted, in order to better balance the heat distribution in said radiant pipe and therefore in the environment to be heated.

Fig. 2 is a general sectional view through a radiant circuit of the heating device 10 according to the invention. The figure shows the transfer and return

conduits

12 and 16 and the combustion products a and B inside them. An outer frame 1, an insulating layer 2 and an optional layer of reflective material 3 may be provided (the layer of reflective material 3 facing the delivery/return conduit 12, 16).

Figure 3 is a cross-sectional view through a radiant tube module according to the present invention. Fig. 3 shows the burner 20, burner head 24 and combustion chamber 22. The combustion chamber 22 is inserted directly into the transfer tube 12.

Figure 3 also shows a recirculation fan 40. The delivery opening 44 of the volute of the fan is directly connected to the delivery pipe 12.

In the embodiment shown in fig. 3, the flue gas discharge duct 50 is mounted on the fan volute 42, but according to other embodiments it may be mounted in another location.

Figure 3 also shows the end portion of the return duct 16 connected to the fan 40. The large-sized arrow A, B indicates the combustion products being conveyed from the conveying pipe to the return pipe.

Figure 3 also shows a less hot return flue gas 441 which is recirculated 441 by the main fan and which surrounds the first transfer duct section 12 and helps to keep the hotter gases 201,221 leaving the combustion chamber 22 in the centre of the duct. As mentioned above, this prevents the particularly hot flue gases from coming into contact with the walls of the conveying pipe 12 and overheating them.

Fig. 4.1 shows a first variant of the radiant strip heating apparatus 10 according to the invention. The main difference with the configuration shown in fig. 1 is the location of the burner 20 and thus the location of the burner head 24 and the combustion chamber 22. In fact, unlike the configuration shown in FIG. 1, the burner 20 is located at an intermediate position along the transfer tube 12. The flue gas discharge pipe 50 may still be in the same position as in the configuration of figure 1 or in a different position. In any event, the transfer tube 12 is directly connected to the outlet 44 of the volute 42 of the fan 40.

Fig. 3.1 is similar to fig. 3, but relates to the configuration shown in fig. 4.1. Similar or functionally equivalent parts have been denoted by the same reference numerals as used in fig. 3, and a detailed description thereof will be omitted.

Fig. 4.2 is a schematic view of a radiant strip heating apparatus 10 according to a second variant of the invention. The difference from the first variant shown in fig. 4.1 is that two burners 20 are provided, and correspondingly two combustion chambers 22 'and two burner heads 24' are provided. The first combustion chamber may be located at an intermediate position along the transfer duct 12 and the second combustion chamber 22' may be located at any position along the return duct 16. This configuration may be advantageous, for example, in the case where the passage followed by the delivery and return pipes is particularly long and therefore there may be significant cooling of the combustion products. The second burner may also be considered a backup burner when the first burner is not functioning or when it has to be serviced. The second burner may also be turned on at system start-up, but may also be turned off when certain conditions are reached (e.g. a given temperature in the environment to be heated).

It is obvious that it is also possible to provide more than two burners, for example three or four burners, along the transfer and/or return ducts.

Another variant of the device according to the invention, as shown in fig. 4.3, is to use a closed combustion chamber 22, i.e. with an outlet for discharging the fumes directly outwards from said combustion chamber. This is therefore clearly free of fumes circulating in the radiant tunnel. Thus, only the hot air will now pass along (both the delivery and return) the radiation pipes.

The air will be kept constantly recirculating by the main fan 40 and thus heated when in contact with the combustion chamber. With this solution, an indirect heat exchange radiant heating system can be obtained, in which only hot air (and no combustion products) passes along the radiant tubes.

Radiant tubes are installed inside the house to be heated and, depending on the intended use of said house, the fumes present inside the radiant tubes may sometimes constitute a risk or danger factor, while the hot air present alone does not constitute any type of restriction.

By applying the latter solution, it is also possible to control the temperature of the air flow inside the tubes to a lower temperature value than can be generated by direct heat exchange by adjusting the power of the burner. In fact, in the case of direct heat exchange, the fumes below a certain temperature will inevitably produce condensation, with the formation of water inside the duct. In contrast, according to the third modification, the temperature in the house to be heated can be adjusted more accurately.

Claims

1. A radiant strip heating apparatus (10) comprising:

a radiant tube comprising a delivery tube (12), a return tube (16) and a connection (14) for connecting the delivery tube (12) with the return tube (16);

a first burner (20) for heating the fluid in the radiant tube;

a fan (40) for recirculating the heated fluid inside the radiant tubes,

wherein the fan (40) comprises a volute (42) having a delivery opening (44), the delivery opening (44) being directly connected to the delivery tube (12).

2. The radiant strip heating apparatus (10) according to claim 1, further comprising: a first combustion chamber (22) and a first combustion head (24) within the first combustion chamber (22).

3. The radiant strip heating apparatus (10) according to claim 2, wherein: the first combustion chamber (22) is inserted directly inside the transfer duct (12) in the vicinity of the transfer opening (44) of the fan (40), instead of being inserted into the connecting plenum.

4. The radiant strip heating apparatus (10) according to claim 2, wherein: the first combustion chamber (22) is inserted inside the transfer tube (12) in an intermediate position along the transfer tube (12) instead of being inserted in the connecting plenum.

5. The radiant strip heating apparatus (10) according to claim 3 or 4, further comprising: a flue gas discharge outlet (50) opposite the volute (42) of the fan (40).

6. The radiant strip heating apparatus (10) according to any one of claims 1-4, wherein: the first combustion chamber (22) is closed and includes a flue gas exhaust outlet (50) for exhausting flue gas directly outwardly from the first combustion chamber (22).

7. The radiant strip heating apparatus (10) according to any one of the preceding claims, further comprising: a second burner (20'), said second burner (20') having a second combustion chamber (22') and a second combustion head (24') inside said second combustion chamber (22 ').

8. The radiant strip heating apparatus (10) according to claim 7, wherein: a second combustion chamber (22') is arranged in the return pipe (16).

9. The radiant strip heating apparatus (10) according to any one of the preceding claims, wherein: the first burner (20) is of the air duct type or of the blown air type or of the premix type, in which fuel and combustion air are sucked in by a fan and mixed together before reaching the first burner head.

10. The radiant strip heating apparatus (10) according to any one of the preceding claims, wherein: the fan (40) is a single inlet centrifugal fan.