INFRARED0 pages

INFRARED
Ap plicat ion: Heat ing b y Ra d iat ion

INFRARED
- Infrared Heaters with Ceramic Insulation -

Figure 1
GENERAL CHARACTERISTICS
INFRARED radiators are the best solution to set up radiation
heating systems based on the use of infrared rays. Their
emission factor is 0.96, i.e. very close to the maximum
theoretical value of 1,and their manufacturing standard allows
to insure:

time the desired temperatures without presenting significant
heat losses throughout the oven inlet and outlet sections.
In addition, if the operational temperature is adequately
selected, high specific power densities (higher than those
typical of conduction or convection heating), can be obtained.

TECHNICAL DATA (see Figure 1)
1. RESISTIVE WINDING spiral made of Nickel/Chrome
80/20 DIN 17470, material n° 2.4869
2. INSULATION made of high purity ceramic which
presents a high resistance to thermal shocks and a high
dielectrical rigidity
3. SURFACE FINISH particular treatment that protects the
insulating body from oxidation, corrosion and water
sprays.
4. FIXATION BASE standard for a 15x41 mm slot
5. POWER SUPPLY CABLES made of Nickel, insulated
using ceramic bushes resistant to high temperatures
6. THERMOCOUPLE type K (Nickel/Chrome-Nickel - optional)

The heating by radiation allows to heat easily and quickly
moving objects. The dimensional and manufacturing
characteristics of the heat radiators allow the construction of
“open” ovens, normally installed around mobile surfaces (e.g.
conveyor belts) inside which it is possible to reach in a short

INFRARED

50
45
40
35
30
25
20
15
10
5
0

E = 0.8

E = 0.4

v = 25 m/s
v = 10 m/s
v = 5 m/s

0

100 200

300 400

500 600

700 800

900

Temperature Difference (°C)

This last consideration is clearly shown in the graph of Figure
2 where the specific power transferred by forced convection
(3 different air velocity values are considered) and the one
obtained by heat radiation (2 different values of the emission
factor are analysed) are compared.
The selection of the heat radiators operating temperature
shall be performed taking into account different and
conflicting needs: on one hand the specific radiated power
increases at higher radiators operational temperatures and
reaches its peak for wavelength values around 2 µm (see
graph in Figure 3), on the other hand, the heat absorption by
the radiated bodies is higher when the radiators temperature
is low (see Figure 4), which correspond to wavelength values
in the range 4 ÷ 5 µm.
Since a radiation heating system based on 300 ÷ 400 °C
operating temperatures would imply a too long heating time,
typically the operating temperature is set to 600 ÷ 800 °C
which corresponds to a peak emission wavelength of about 3
µm (see Figure 5).

www.masterwatt.it

pag. 1/8

Issue September 2010

HEATING BY RADIATION
The rapid growth of the technology in the field of plastic
materials processing has requested the development a large
variety of electric heaters, capable to transfer efficiently the
heat in the most different operational conditions.
The most common applications adopt the heat transfer by
direct contact or by convection. There are cases, however, in
which peculiar process characteristics (rapid working cycle,
necessity to heat moving objects, impossibility to seal the
heating process inside a volume that is closed to the external
environment) do not allow to use effectively the heating by
conduction or convection. In these case the most appropriate
solution is to adopt a heat transfer by radiation.

Transferred Power (kW/m²)

Figure 2:
Long operational life
Fast heat transmission
Constant emission along the operational life
Perfect heating uniformity
Easy installation