Red-Ray burners utilize this radiation to transfer heat to
the material being processed. Red-Ray burners have their energy
distribution and wavelength typically centered around 2.7
microns which is typically termed medium wavelength infrared.
This is the wavelength that corresponds to the spectrum which
water and many other materials effectively absorb the energy.
The most widespread and common applications for infrared burners
is for drying.
The radiant heat follows the same physical laws as light
and travels in a straight line until it strikes an absorbing
surface.
Radiation exists at all times between two bodies of dissimilar
temperature and the rate of heat transfer depends on the difference
in temperature between the two bodies.
Absorptivity and Emissivity
The performance of infrared thermal radiation is dependent
upon the absorptivity and emissivity of the receiver body.
Absorptivity can be stated as the ratio of radiant energy
absorbed by an actual surface at a given temperature to that
absorbed by a "black body" at the same temperature.
This "black body" is a term applied to a body that
will absorb all incident thermal radiation.
Actually, there is no true "black body" for thermal
radiation in nature, but the terminology has been universally
adopted for ratio comparisons in calculating the actual absorption
of radiant energy by different materials.
In fact, a "black body" does not necessarily have
to be black…snow is considered very nearly black in infrared
studies. When infrared strikes an object, some of it is absorbed
and some reflected. The portion of energy absorbed determines
the absorptivity of the material.
A "black body" not only absorbs infrared (radiant)
energy, but also emits equal maximum radiation at any temperature.
Emissivity is therefore the ratio of radiant energy emitted
by any object at a given temperature to the radiant energy
emitted by a "black body" at the same temperature.
The wavelength at which this "black body" emits
its maximum radiation is dependent upon its temperature.
As the temperature of a "black body" surface is
increased, the maximum radiation occurs at shorter wavelengths
and has a much higher intensity, with an increasingly larger
portion of the radiation occurring nearer the visible range.
The Benefits of Direct Gas-Fired
Infrared Burners
Red-Ray manufactures two general categories of gas fired
infrared burners: flame impingement and surface combustion.
The Red-Ray flame impingement gas-fired burners (Models F,
KN, 67IR and 64IR) employ an air-gas mixture impinging directly
on the finned refractory surface to produce a high-density
flux of maximum radiance. The flame itself is not a source
of infrared radiation. Its function is to heat the refractory
to temperatures of 1650° to 2000°F. The refractory
then emits infrared energy in the micron range most efficient
for product heating.
The Red-Ray surface combustion type of gas-fired burners
includes Models QC-12, MR-12, Apollo-Ray, Infra-Glo, Ultra-Rad
and AB-7. They each have the combustion process take place
along a porous and flat refractory metal or ceramic. The premixed
air and gas pass through the burner body and out through the
porous emitter surface. They combust along only the thin outer
surface and create the high radiating temperatures of 1200°
to 1800°F. These burners are therefore much quicker to
heat up and cool down than the traditional flame impingement
infrared burners.
Heat Transmission
The Red-Ray direct gas-fired burner can be modulated from
"full off" to "full on" to permit the
infrared energy to be adjusted to suit the particular application.
With this unusual and important ability, the user is given
a great deal of flexibility during production. The user also
has the ability to lower the radiation intensity by moving
the burners further from the product.
Rugged, Quality Construction
Red-Ray burners will deliver heat when and where needed
in industrial heat processing. All materials are selected
to provide constant temperature performance. Additionally,
all Red-Ray burners are modular and include a three-piece
union connector that permits fast, easy replacement of any
burner section. The reliability and design integrity of Red-Ray
burners is backed by over 60 years of practical application
of infrared radiation to industrial processes.
How the Red-Ray Burner Operates
Red-Ray radiant burners are premix type burners in which
air and gas are mixed and delivered to the burner for firing
under pressure. The equipment for mixing consists of an air
blower and a venturi mixer.
Air is delivered under pressure to a mixer having a metering
orifice. This orifice determines the volume of air at any
pressure delivered to the burner. The pressure of air is controlled
by a butterfly valve ahead of the mixer. After leaving the
orifice, the air is expanded through the venturi of the mixer
to create suction on the gas line.
Gas is delivered to the mixer through an air/gas ratio regulator
(zero governor). This regulator reduces the pressure of the
gas to atmospheric or zero pressure. Therefore, when the air
is expanded through the venturi in the mixer, the resultant
suction on the gas line mixes a proportionate flow of gas
to the flow of air – which is then delivered to the burner.
The Stoichiometric ratio of 10 parts air to 1 part natural
gas is thus provided to achieve maximum fuel efficiency.
The gas inlet to the mixer has a variable orifice which
must be adjusted to the correct ratio of gas for the amount
of air entering the mixer. When adjusted, the mixing system
has a single valve throttling control. Controlling the air
valve will automatically control the amount of suction on
the gas line, thereby changing the amount of gas and air delivered
to the burner in an accurate ratio through its entire adjustment
range.
RED-RAY Will Design and Supply Your
Entire System…Including Combustion Control Equipment
During more that 60 years of service to industry, Red-Ray
has developed a storehouse of application knowledge that is
available to any customer at any time.
This knowledge is reflected in the design of our products
and systems. Red-Ray engineers can recommend to you how many
burners to use, how close they should be to the product and
where they should be positioned for best results.
Red-Ray engineers will design the entire piping system for
your application. You will receive drawings listing all the
required components by manufacturer’s part number. All
piping will be sized for optimum results.
Combustion control panels will be supplied with performance-proven
components that will safely control burner operation.
The best part is Red-Ray’s service. Standard or custom
manifolded burners can usually be shipped to you within a
week. In most cases, if your order for replacement parts is
in by noon Eastern Time, they will be shipped the same day.
Complete combustion systems – consisting of burners,
manifolds, air/gas mixers, control panels, blowers, throttles,
solenoid valves, pressure regulators, shutoff cocks, etc.
– can be designed by our engineering staff and shipped
to you in 6 to 8 weeks. Red-Ray has always taken pride in
having the fastest service in the industry.
