[0001] THIS INVENTION relates to a heating system wherein heat is provided by the emission
of infra-red radiation.
[0002] Infra-red radiation heats objects directly with a minimal loss of heat energy to
the air between the heating apparatus and an object. The object, having absorbed the
infra-red radiation, may conduct some of the heat from the surface into the interior
of the body of the object and re-radiate the remainder, becoming a secondary source
of infra-red radiation. The re- radiated heat energy will then be absorbed by other
cooler surfaces or by the surrounding air.
[0003] The amount of heat lost to the surrounding air, roof space and in the creation of
draughts is therefore negligible for infra-red heating systems.
[0004] It is known to use infra-red radiation generated by the passage of hot gases through
a heating pipe, for example by burning an air/gas mixture in the pipe, to heat living
quarters and places of work, for example, shops, offices and factories.
[0005] However, until a decade ago infra-red radiation could only be used efficiently to
provide high temperature, for example as required in bake ovens. Such systems used
as a source of heat only the upper range of the infra-red spectrum. Direct heating
systems for living and working areas were, at that time, very inefficient, utilizing
little, if any, of the infra-red radiation produced to heat objects directly.
[0006] More recently, by providing control means for supplying the correct proportions of
air and gas to produce an efficiently combustible mixture, connecting the control
means to a plurality of combustion devices contained in connecting pipes situated
in the space to be heated, and by operating the heating system at a pressure slightly
less than one atmosphere, it has been possible to use more of the infra-red radiation
emitted from the walls of the connecting pipes to heat objects directly. However,
due to the presence in the connecting pipes of the combustion products produced by
preceding combustion devices, insufficient oxygen may be present to effect complete
combustion, thus preventing efficient operation of the combustion devices.
[0007] According to the present invention there is provided an infra-red heating system,
comprising a heating pipe and a plurality of combustion devices distributed along
the length of the heating pipe for supplying hot gases to the interior of the pipe
to cause the pipe to emit infra-red radiation from its surface, in which system each
combustion device comprises a burner unit disposed in the heating pipe and control
means having an air orifice for supplying to the burner unit the correct amount of
air for complete combustion of fuel fed to the burner unit, means being provided to
cause a predetermined excess of air to flow through the pipe in use of the system
so that each of the serially arranged burner units can operate within the pipe with
complete combustion of fuel in an atmosphere which contains the combustion gases of
any upstream burner units.
[0008] Thus, an infra red heating system embodying the invention provides the advantage
that a combustion device operating in a series of combustion devices in an atmosphere
containing combustion products from the other burners may still release the total
heat of combustion without flame vitiation.
[0009] Preferably each combustion device in the series provides the same heat output and
may be pre-adjusted at a factory to give that output.
[0010] The gas/air ratio may be preset and maintained during variations in the overall draught
and temperature conditions.
[0011] Preferably, a control means associated with each combustion device regulates the
amount of gas supplied thereto.
[0012] Conveniently, a single adjusting means is provided to allow the heat capacity of
the system to be adjusted or to compensate for changes in the characteristics of the
fuel.
[0013] Thus, when using a gaseous fuel, a change in, for example, the wobbe number can be
compensated for by a simple adjustment allowing the required total heat output and
the preset gas/air ratio to be maintained. Preferably, the adjusting means comprises
a damper.
[0014] Conveniently, reflecting means are associated with one or more parts of a heating
pipe to direct the radiant heat energy produced thereby to the space required to be
heated. Usually, the reflecting means comprise an elongate reflector arranged axially
above a part of the heating pipe to direct radiant heat energy downwardly from the
pipe part to the space to be heated and an elongate reflecting shield supported axially
beneath the pipe part to deflect a portion of the radiant heat energy radiated from
the pipe part upwardly into the reflector. Such reflecting means provide the advantage
that the heat energy may be directed only to the space required to be heated thus
preventing or reducing wastage.
[0015] Also, one or more parts of a heating pipe may be provided with insulating means to
regulate the emission of radiant heat energy therefrom which insulating means usually
comprise an insulating tube inserted into a part of a heating pipe so as to contact
the inner surface thereof. The provision of such insulating means allows the conversion
of radiant heat energy to be regulated as required and thus reduces the possibility
of overheating of a particular space to be heated.
[0016] According to another aspect, the invention provides an infra-red heating system,
wherein a heating pipe is heated by the passage of hot gases therethrough so that
infra-red radiation is emitted from the pipe, and wherein reflecting means are associated
with at least part of the pipe to direct the radiant heat energy therefrom to the
space to be heated, the reflecting means comprising an elongate reflector arranged
above the pipe to direct radiant heat energy from the pipe downwardly to the space
to be heated and an elongate reflecting shield supported beneath the pipe to deflect
a portion of the radiant heat energy from the pipe upwardly to the reflector.
[0017] In a further aspect, the invention provides an infra-red heating system, wherein
a heating pipe is heated by the passage of hot gases therethrough so that infra-red
radiation is emitted from the pipe, and wherein one or more parts of the pipe are
provided with insulating means to regulate the emission of radiant heat energy therefrom,
the insulating means comprising an insulating tube inserted into the pipe so as to
contact the inner surface thereof.
[0018] In order that the invention may be readily understood, a preferred embodiment thereof
will now be described, by way of example, with reference to the accompanying drawings,
in which:
FIGURE 1 is a schematic representation of an infra-red heating system showing a particular
arrangement of pipe legs containing varying . numbers of burners;
FIGURE 2 is a vertical cross-section through part of an interconnecting pipe containing
a combustion device;
FIGURE 3 is a perspective view of part of a pipe leg of the system of Figure 1 having
reflection means associated therewith to reflect the radiant heat energy produced
by the pipe leg part;
FIGURE 4 is a view from one end of the pipe leg of Figure 3 showing the reflection
means associated therewith; and
FIGURE 5 is a diagrammatic longitudinal cross-section through part of a pipe leg of
the system of Figure 1 provided with insulating means to regulate radiation of heat
energy from that part of the pipe leg.
Figure 1 illustrates schematically one arrangement for a heating system comprising
several pipe legs, consisting of connecting pipes B and combustion devices C, and
connected via manifold pipes B to a vacuum pump A. Non-adjustable end vents D are
provided at the free ends of the pipe legs to allow a controlled amount of excess
air to enter the pipe system.
[0019] The vacuum pump A draws the air/gas mixture through the pipes and allows a controlled
reduction of pressure to just less than atmosphere.
[0020] A damper E is provided in each pipe leg upstream of its interconnection F with another
leg to regulate the suction effect of the vacuum pump A and make each leg independent
of the suction effect in the remainder of the system.
[0021] Another damper E', situated upstream of the vacuum pump A, allows the suction effect
of the vacuum pump to be regulated simultaneously in the whole system.
[0022] To accommodate variations in and combinations of combustion device firing rates the
"equivalent burner" concept for calculating the correct gas/air ratio has been replaced
by a flow unit method, where one flow unit A. is the quantity of air required to support
the combustion of 235 cm
3/s (10 cu.ft./h) of natural gas which is equivalent to 10550.65 kJ/h = 2.93 KW.
[0023] To provide for complete combustion of natural gas (which mainly is comprised of methane)
a gas/air ratio of 1:2 is required giving : λ =
787 cm
3/s (100 cu.ft./h).
[0024] As shown in Figure 1 each combustion device C requires 6 λ. or 1.7 m
3/h of air, whilst each end vent D is constructed to allow 12 Xor 3.4 m
3/h to enter the apparatus.
[0025] Figure 2 shows a vertical cross-section through an individual combustion device C.
[0026] The combustion device C comprises a control box F and burner unit G.
[0027] The burner unit G includes a pipe having internally screwthreaded ends 17 which engage
externally screwthreaded ends 21, 21' of connecting pipes 18, 18' to mount the burner
in a pipe leg. However, other methods of connecting the burner unit pipe in a pipe
leg may of course be employed.
[0028] Gas enters the control box F by means of a gas pipe 1 and a regulator 3 ensures that
the correct amount of gas is supplied to the system. The regulator 3 is connected
to a chamber 22 containing; a zero governor 4 which maintains the gas at atmospheric
pressure; a pilot valve 5 to control the amount of gas supplied to a spark chamber
23, by means of a pilot gas tube 12 connected to the pilot valve 5; and a main valve
6 to control the amount of gas entering the burner unit via a channel 11 connected
to the output 10A of chamber 22.
[0029] An air filter 2 removes dust particles etc, from the air to avoid choking the apparatus
with extraneous matter. Air passing through the filter 2 either enters the pilot gas
tube 12 by means of an air orifice 8 in the gas tube 12, or passes through an orifice
10 designed to let the correct amount of air through a channel 11 to a burner grid
16. A wall 14 of the channel 11 protects a pilot light in the spark chamber 23 from
draughts caused by air passing through the channel ll.
[0030] Similarly, a curved back wall 15 of the channel 11 shields the burner grid 16 from
the flow of combustion gases passing through the connecting pipe 18.
[0031] A pre-ignition purge timer, (not shown) is started when the temperature of the space
to be heated drops below a predetermined desired temperature and the timer actuates
the vacuum pump to clear the system of any remaining combustion gases or other unwanted
matter.
[0032] The vacuum pump A is designated to reduce the pressure inside the heating system
to a pressure of 3 inches of water (5.6 mmHg) below atmospheric pressure. The suction
effect produced by the pump A is regulated by the dampers E provided in each pipe
leg and by the damper E' provided upstream of pump A.
[0033] The end vents D allows 12 λ or 3.4 m
3/h of air to be drawn into the system under the action of the pump A.
[0034] The operation of a combustion device C will now be described.
[0035] Gas is drawn into the system through a gas pipe 1 and air is sucked through an air
filter 2 into the control box F by the pump A. The regulator 3 ensures that the correct
amount of gas passes into the chamber 22 and the pressure of the gas is maintained
at one atmosphere by means of the zero governor 4.
[0036] Initially gas is drawn through the pilot valve 5 into the pilot gas tube 12 and mixed
with air entering the tube 12 by means of the air orifice 8.
[0037] The air/gas mixture passes by means of an opening 20 into the spark chamber 23. A
heat control means (not shown) actuates electrical means (not shown) to induce the
contacts 13 of a spark-plug 9 to spark. The air/gas mixture in chamber 23 then ignites.
[0038] A sensor (not shown) detects the pilot flame and allows the main valve 6 to open.
Gas is then passed through an opening 10A in the chamber 22 into the channel 11 and
air is drawn into the channel 11 (by the suction effect produced by the gas flow)
through the orifice 10 which is of the correct dimensions to produce the optimum air/gas
mixture.
[0039] The air/gas mixture passes through channel 11, being prevented from extinguishing
the pilot flame by means of the wall 14 of channel 11, to the burner grid 16, where
combustion occurs upon contact with the pilot flame.
[0040] The combustion gases are drawn through the pipe 18', by the action of the vacuum
pump A, the pipe being thereby heated and radiating energy in the form of infra-red
radiation.
[0041] Combustion gases from any preceding burner units passing the burner grid 16 are deflected
by a curved back wall 15 of the channel 11. The wall 15 thus shields the burner flames
from the combustion gases preventing contamination of the air/gas mixture which could
decrease the combustion efficiency and also preventing the flames being extinguished
by the draught caused or by lack of oxygen.
[0042] The vacuum pump A removes the combustion gases from the system and these waste gases
then pass out of the dwelling or work place and are discharged into the atmosphere.
[0043] Figures 3 and 4 illustrate means associated with a part B' of a pipe B for reflecting
the radiant heat energy emitted by that pipe part to the area of the dwelling or work
place required to be heated.
[0044] As shown, the reflecting means comprises an elongate reflector 24 of substantially
inverted W-shape in cross-section disposed above the pipe part B' such that the longitudinal
axis of the reflector is parallel to the axis of the pipe B. The reflector 24 is designed
to reflect radiant heat energy radiated upwardly from the pipe part B' down to the
area being heated.
[0045] The reflecting means also comprises an elongate radiant heat shield 25 of inverted
V-shape in cross-section suspended by support brackets 26 beneath the pipe part B'
such that the longitudinal axis thereof is parallel to the pipe axis. The radiant
heat shield 25 serves to reflect a portion of the radiant heat energy reflected downwardly
from the pipe part B' onto the reflector 24 to ensure that the radiant heat energy
is distributed more evenly over the area being heated.
[0046] The radiant shield 25 can be used locally to reduce the radiant intensity immediately
below the radiant pipe. In the absence of the reflecting means the radiant heat intensity
is highest at a point immediately below the radiant pipe B' as a result of the Inverse
Square Law. By virtue of its shape and position the radiant shield 25 interrupts the
direct radiant heat path and reflects heat back to the top reflector 24 which redistributes
the radiant heat away from the centre line of the radiant pipe
[0047] Both the reflector 24 and the radiant heat shield may be made, for example, of 22
or 24 SWG NATL (TYP) aluminium and are approximately from 4 to 8 feet (1.2 to 2.4
metres) in length depending upon requirements. One or more reflecting means may be
provided within the system of Figure 1 depending upon the particular heating requirements
for the areas to be heated.
[0048] Figure 5 illustrates diagrammatically a part B" of a pipe B provided with insulating
means to regulate the amount of radiant heat energy emitted from that part of the
pipe B.
[0049] As shown in Figure 5, the insulating means comprises an insulating tube 27 of, for
example, 0.5 metres in length and made for example of ceramic fibre or a similar material
having high heat insulation properties. In the arrangement shown, the insulating tube
27 is made of alumina having a wall thickness of 5 to 10 mm.
[0050] The insulating tube 27 is inserted into the pipe part B" so as to contact the inner
surface thereof. The insulating tube 27 allows the amount of radiant heat energy emitted
from the portion of the pipe containing the tube to be reduced by reducing the temperature
of the pipe B at that point.
[0051] Insulating tubes may be provided at various points within the system of Figure 1
to reduce radiant pipe temperatures in localized positions thus controlling radiant
heat emission along pipes B of the system and preventing overheating of areas where
little heating is required.
[0052] As can be seen from Figure 5, apertures 28 may be provided in the insulating tube
or tubes 27 provided in the system to provide extremely localized areas of higher
radiant heat energy where required.
1. An infra-red heating system, comprising a heating pipe and a plurality of combustion
devices distributed along the length of the heating pipe for supplying hot gases to
the interior of the pipe to cause the pipe to emit infra-red radiation from its surface,
in which system each combustion device comprises a burner unit disposed in the heating
pipe and control means having an air orifice for supplying to the burner unit the
correct amount of air for complete combustion of fuel fed to the burner unit, means
being provided to cause a predetermined excess of air to flow through the pipe in
use of the system so that each of the serially arranged burner units can operate within
the pipe with complete combustion of fuel in an atmosphere which contains the combustion
gases of any upstream burner units.
2. A system according to claim 1, wherein each combustion device is preadjusted to
provide the same heat output.
3. A system according to claim 1 or 2, wherein a single adjusting means is provided
to allow the heat capacity of the system to be adjusted or to compensate for changes
in the characteristics of the fuel.
4. A system according to any preceding claim, wherein the fuel comprises a combustible
gas and the gas/air ratio supplied to each combustion device is preset and maintained
during operation of the combustion device.
5. A system according to claim 4, wherein a control means associated with each combustion
device regulates the amount of gas supplied thereto.
6. A system according to any preceding claim, wherein pumping means are provided to
maintain the pressure within the system just below atmospheric pressure during operation
thereof.
7. A system according to claim 6, wherein timing means are provided to actuate the
pump means to purge the system of any remaining combustion gases or other unwanted
matter prior to operation thereof a predetermined time after the temperature of the
space to be heated drops below the desired temperature.
8. A system according to claim 6 or 7, wherein the system comprises a plurality of
heating pipes connected in parallel to the pumping means, each heating pipe having
a plurality of combustion devices distributed therealong..
9. A system according to claim 10, wherein each heating pipe is provided with damping
means upstream of the combustion devices to regulate the suction effect produced therein
by the pumping means.
10. An infra-red heating system according to any preceding claim, wherein reflecting
means are associated with one or more parts of the or a heating pipe to direct the
radiant heat energy produced thereby to the space required to be heated.
ll. A system according to any preceding claim, wherein one or more parts of the or
a heating pipe are provided with insulating means to regulate the emission of radiant
heat energy therefrom.
12. An infra-red heating system, wherein a heating pipe is heated by the passage of
hot gases therethrough so that infra-red radiation is emitted from the pipe, and wherein
reflecting means are associated with at least part of the pipe to direct the radiant
heat energy therefrom to the space to be heated, the reflecting means comprising an
elongate reflector arranged above the pipe to direct radiant heat energy from the
pipe downwardly to the space to be heated and an elongate reflecting shield supported
beneath the pipe to deflect a portion of the radiant heat energy from the pipe upwardly
to the reflector.
13. An infra-red heating system, wherein a heating pipe is heated by the passage of
hot gases therethrough so that infra-red radiation is emitted from the pipe, and wherein
one or more parts of the pipe are provided with insulating means to regulate the emission
of radiant heat energy therefrom, the insulating means comprising an insulating tube
inserted into the pipe so as to contact the inner surface thereof.