GB2313660A

GB2313660A - Gas burner for use with radiant tube heater

Info

Publication number: GB2313660A
Application number: GB9711081A
Authority: GB
Inventors: Michael John May
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-29
Filing date: 1997-05-29
Publication date: 1997-12-03
Anticipated expiration: 2017-05-29
Also published as: DE19722172A1; GB2313660B; GB9611215D0; GB9711081D0

Description

2313660 IMPROVEMENTS IN AND RELATING TO GAS BURNERS This invention relates

to gas burners and the use of such burners in radiant tube heater systems.

Gas-fired radiant tube heater systems are commonly used to heat large internal areas, such as factories, workshops, warehouses and the like. They usually comprise one or more gas burners which discharge hot combustion products into a radiant carrier tube. Heat from the combustion products is transferred to the carrier tube which then radiates that heat outwards. The systems are generally located near the ceiling and are normally provided with U- or V-shaped reflectors so as to ensure that the heat radiated by the carrier tube is directed downwards. Fan means are generally provided to induce a flow of air into and along the carrier tube so as to draw the hot combustion products therealong and to exhaust the cooled combustion products from the carrier tube and out of the building.

The simplest form of gas burner operates on the same principle as a bunsen,burner. Combustible gas is discharged from a gas jet into a tubular nozzle. The flow of gas draws air into ports at the base of the nozzle, forming a gas/air mixture which combusts as it leaves the nozzle outlet. The air ports are so sized relative to the gas flow to try to ensure a gas/air mixture which optimises the combustion process. The nozzle directs the flame, or combustion zone, into the end of the carrier tube. Currently available burners which operate on the Ilbunsen burner" principle are generally too expensive and powerful for use on a scale smaller than that of factories, such as in offices or domestic applications.

The present invention provides a gas burner for use with a radiant tpbe heater system, comprising means for directing a flow of a combustible mixture of gas and primary air towards a zone where the mixture combusts in the form of a longitudinal flame, means being provided to induce a flow of air to draw said flame 2 out of the burner, wherein the burner comprises a baf f le to restrict the ingress of secondary air to the combustion zone at least at the base portion thereof, the baffle extending in the longitudinal direction of the combustion zone and having an open end for the egress of the combustion zone and air ports adjacent the base of the combustion zone for the ingress of secondary air, the directing means and the baffle being contained within a housing, and the open end of the baffle being substantially aligned with but spaced inwardly from an opening in the housing.

In a known burner, the baffle extends into the carrier tube of the heater system. Connection of such a burner to a carrier tube system is time consuming and complex as flame sensors need to be fitted to the carrier tube to monitor the output from the baffle. This prior arrangement is also aesthetically unsatisfactory, particularly for domestic or office uses, as wires leading from the sensors to the burner must run over the outside of the carrier tube. However, the burner of the invention is advantageous relative to such a configuration as the baffle is disposed within the housing of the burner and the burner is thus a self-contained unit. The sensors may therefore also be disposed within the housing of the burner and the associated wiring can be concealed in the housing.

The burner of the invention may be operable to provide heating power in a range appropriate for applications of a smaller scale than factories, which is preferably between 3 and 30kW. It may accommodate variations in the total heat output, merely by adjusting the overall flow of air to match the gas flow rate, without any loss in efficiency or cleanliness. It may easily be fitted to existing radiant tube heater systems merely by removing the old burner and replacing it with one in accordance with the invention, and the burner can easily be removed for maintenance or cleaning as required, without requiring any modification to the carrier tube itself. The burner is capable of using most forms of combustible gases, or mixtures thereof.

3 The present invention further provides a method of heating space within a building comprising generating a supply of heated gas, inducing the heated gas to flow through a radiant carrier tube, and disposing at least one substantially planar reflector adjacent to the carrier tube to direct heat radiation emitted from the carrier tube into said space.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a sectional side view of a known gas burner; Figure 2 is a perspective view of a known gas-fired radiant tube heating system including the burner of Figure 1; Figure 3 is a sectional side view of a gas burner in accordance with the invention; Figures 4 and 5 are sectional end and plan views, respectively, of a radiator of a heater system in accordance with the invention; and Figure 6 is a sectional plan view of another radiator configuration of the invention.

A known burner configuration is shown in Figure 1. it comprises a burner box 2 (only partially illustrated), a nozzle 4 and a baf f le 6. The baf f le 6 is mounted within a radiant carrier tube 8 of a heater system. The burner box contains control means for the burner. It also receives a gas supply line and may also house fan means to blow air through the system, as an alternative to the usual arrangement where a fan located at the far end of the carrier tube 8 draws air into the system. Four primary air ports 10 (only one shown) are formed in the nozzle 4.

A cpmbustible gas flow G, consisting of natural gas, propane, or a mixture of propane, butane and air is fed into the nozzle from the box 2. This draws primary air through the ports 10 forming a combustible mixture which is ignited at the end of 4 the nozzle 4 to form a flame or combustion zone which extends to the right of the Figure. A controlled amount of secondary air is drawn into the baf f le 6 through ports 12, which air aids the combustion process. The baffle 6 precludes the ingress of any further, tertiary air into the combustion zone until the flame reaches outlet 14, whereupon tertiary air contacts the combustion zone. This tertiary air mixes with the combustion zone to assist the combustion process and also entrains the combustion zone, drawing it and the hot combustion products into and along the carrier tube 7.

Properties of the combustion zone and the products of combination are monitored using one or more f lame sensors 16. Gas f low into the burner is measured using two pressure sensors 17. The pressure difference therebetween is proportional to the gas f low. The output f rom the sensors is f ed back to the control means in the box 2 along wires (not shown) which must pass over the outside of the burner to avoid heat damage. This configuration is not aesthetically attractive, which is an important consideration in domestic and off ice applications. Also, installation of such a burner onto a carrier tube 8 is time consuming and expensive as the sensors 16 and the mounting 18 need to be fitted individually onto the carrier tube.

Figure 2 illustrates a known heater system incorporating the burner 2 of Figure 1. This type of system is normally suspended by wires 20 from the ceiling of factories or other large internal areas. In the illustrated configuration, the carrier tube 8 is formed into a U-shape and has fan means 22 at its outlet for drawing gas therethrough. The carrier tube is mounted in a reflector 24 having a generally U-shaped cross-section.

A gas burner 25 according to the invention is shown in Figure 3, It comprises a housing 26 which is divided by partition plates 28 and 30. The forward end of the housing is removably mounted to the distal end of the carrier tube 8. The housing 26 is divided into a three compartments 32, 34 and 36.

The compartments 32 and 36 house the gas supply line (not shown) and can also house fan means.

The compartment 34 of the housing 26 is substantially airtight, having only an exit opening 38 for the flame to pass into the carrier tube 8 and a number of ports 40 in the partition plate 28 to allow combustion air and air for entraining the hot combustion products and drawing them along the radiant carrier tube 8 to enter the forward compartment 34. The size and number of ports 40 is dictated by the heat output of the burner and means (not shown) may be provided to open or close one or more of ports 40 so as to vary the amount of air entering forward compartment 34, thereby to accommodate any change in the heat output.

The open end 14 of the baffle 6 is close to the end of the carrier tube 8 but does not extend thereinto. This enables plane sensors 16 to be positioned in f ront of the open end of the baffle 6 whilst being mounted within the housing 26. Pressure sensors 17 can also be provided within the housing 26. Thus, the burner unit 25 is self-contained and can be readily mounted to a carrier tube 8. Any wiring associated with the sensors is concealed within the housing, creating a neater and more compact appearance which is desirable in domestic or office applications.

The gas burner 25 can be readily adapted to give a different output range by changing nozzle 4 and partition 28 (for one with a different number and/or size of air ports 40) and by changing the suction produced by the fan means. Fine adjustment of the combustion process can also be effected by providing means to adjust one or more of the size and/or number of primary air ports 10, of secondary air ports 12 and the length of the baf f le 6. These adjustment means could be automated and controlled by a suitable pontroller, such as a microprocessor, either to maintain the radiant heat output, or distribution thereof, constant, or to vary these appropriate.

6 A radiator 41 for use in a hot gas heater system is shown in Figures 4 and 5, in sectional side and plan views, respectively. An alternative radiator arrangement is shown in Figure 6. Although the radiators described herein are preferably used with a gas burner of the present invention, they may also be suitable for use with other burner configurations. A reflector 42 is mounted adjacent to the carrier tube 8. The outer surface of the reflector is insulated. This may be achieved economically by inserting metal foil 44 between the reflector 42 and a panel 46. Preferably, an emitter panel 48 is also included to enclose the carrier tube 8 and improve the appearance of the radiator. In another preferred arrangement, the foil is provided between the carrier tube and the reflector and thus the panel 46 is not required.

The radiator of Figures 4 and 5 is particularly suitable for use in offices or domestic applications, for example. It may be ceiling or wall mounted. A reflector of the type shown in Figure 2 is used in larger scale applications such as factories. it produces a downward "beam" of heat radiation which subtends an angle of about 900 at the carrier tube. The heater therefore needs to be mounted high to provide sufficient coverage near floor level. This is not often possible in smaller spaces. The planar radiator configuration of Figures 4 to 6 radiates a much broader beam of heat energy and therefore heats a room more evenly. It also occupies substantially less space than that of Figure 2.

Furthermore, the radiator described above is advantageous relative to a conventional central heating radiator which essentially relies on convection to transfer its heat around a room. In such a system, heated air loses a large proportion of its heat energy as it travels across the ceiling of a room before cooling and falling down the wall opposite to the radiator. The reflector 42 and insulation 44 of the radiator 41 shown in Figure 4 increase the proportion of the heat energy emitted from the radiator which is radiated into the room. Furthermore, if such 7 a radiator is mounted near the ceiling, convection losses are decreased and the level of radiation may be increased by raising its surface temperature.

Also, the prior type of system circulates water, which is a considerably less manageable medium than a gas. Gas can move more quickly through the present system, giving a quicker response to changes in the system settings.

The carrier tube of Figures 4 and 5 is formed into a Ushape. However, a wide range of configurations may be adopted. The alternative shown in Figure 6 has two bends in the carrier tube 8.

As also shown in Figure 6, heat transfer from the carrier tube 8, may be assisted by "gills" 50 on the tube or means 52 for creating turbulence within the tube. The gills 50 consist of annular members fitted around the tube which substantially increase the surface area of the tube. The turbulence creating means 52 may be in the form of aerodynamic turbulators or "swirlers", such as helical strips, for example, which can be formed by twisting a metallic strip. This serves to direct the hot gases in the tube 8 towards its wall, without unduly restricting the gas flow within the tube. These devices enable the length of the carrier tube 8 and therefore the size of the radiators 41 to be reduced whilst maintaining the same heat transfer characteristics.

0 8

Claims

1 A gas burner f or use with a radiant tube heater system, comprising means for directing a flow of a combustible mixture of gas and primary air towards a zone where the mixture combusts in the form of a longitudinal flame, means being provided to induce a f low of air to draw said f lame out of the burner, wherein the burner comprises a baf f le to restrict the ingress of secondary air to the combustion zone at least at the base portion thereof, the baffle extending in the longitudinal direction of the combustion zone and having an open end for the egress of the combustion zone and air ports adjacent the base of the combustion zone for the ingress of secondary air, the directing means and the baffle being contained within a housing, the open end of the baffle being substantially aligned with but spaced from an opening in the housing.

2 A gas burner as claimed in Claim 1 wherein the baf f le is effective to permit a predetermined amount of secondary air to enter the base of the combustion zone and substantially to exclude further, tertiary air from at least a portion of the length of the combustion zone.

3 A gas burner as claimed in Claim 1 or Claim 2 wherein the length of the baffle is variable.

4 A gas burner as claimed in any preceding claim including a sensor for monitoring said flame, the sensor being provided within the housing.

A gas burner as claimed in Claim 4 wherein the sensor is disposed.between the open end of the baffle and the opening in the housing.

9 6 A gas burner f or use with a radiant tube heater system, comprising means for directing a flow of a combustible mixture of gas and primary air towards a zone where the mixture combusts in the form of a longitudinal flame, means being provided to induce a flow of air to draw said flame into and along a radiant carrier tube of said heater system, wherein the burner comprises a baffle to restrict the ingress of secondary air to the combustion zone at least at the base portion thereof, the baffle extending in the longitudinal direction of the combustion zone and having an open end for the egress of the combustion zone and air ports adjacent the base of the combustion zone for the ingress of secondary air, the directing means and the baffle being contained within a housing which is sealably connectable to the distal end of said carrier tube, the arrangement being such that the longitudinal combustion tube is substantially coaxial with at least the distal end portion of said carrier tube, and the length of the baf f le is such that when the housing is connected to the distal end of said heater system the open end of the baffle is spaced from the distal end of said carrier tube.

7 A gas burner for use with a radiant tube heater system substantially as described herein with reference to Figure 3 of the drawings.

8 A gas-fired radiant tube heater system comprising a gas burner as claimed in any of Claims 1 to 5 and a radiant carrier tube connected to the opening in the housing which is substantially aligned with the open end of the baffle.

9 A system as claimed in Claim 8 including at least one reflector adjacent to the carrier tube.

A system as claimed in Claim 9 wherein the at least one reflector, is substantially planar.

11 A system as claimed in Claim 9 or Claim 10 wherein the outer surface of the at least one reflector is thermally insulated.

12 A system as claimed in Claim 10 or Claim 11 as appendant to Claim 10 wherein a respective substantially planar emitter member for radiating heat energy is provided adjacent the opposite side of the carrier tube to each reflector.

13 A gas-fired radiant heater system substantially as described herein with reference to Figures 3 to 6 of the drawings.

14 A method of heating space within a building comprising generating a supply of heated gas, inducing the heated gas to flow through a radiant carrier tube, and disposing at least one substantially planar reflector adjacent to the carrier tube to direct heat radiation emitted from the carrier tube into said space.

is A method of heating space within a building substantially as described herein with reference to Figures 3 to 6 of the drawings.

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