RADIANT HEATING WITH INFRARED - Watlow

W/in 2
Radiated
Net
In a typical radiant application, a heater radiates energy to a product. As the
temperature of the product increases, it begins to radiate a significant amount
of energy as well. To determine the net power radiated, the power radiated by
the product must be subtracted from that radiated by the heater. The equation
thus becomes:
Net Watts Radiated = Constant [(Heater Absolute Temperature) 4 - (Product
Area Absolute Temperature) 4 ]
This equation is plotted for various heater and product temperatures in
Figure 7. From the graph it can be seen that the greater the temperature
difference between the heater and the product, the greater the net watts
radiated. When the heater and product temperature are equal, the net watts
radiated is zero.
45.00
40.00
35.00
30.00
25.00
Stefan-Boltzman Equation (Fig. 7)
20.00
1200
15.00
1100
1000
10.00
900
800
5.00
700
600
0.00 500
100 200 300 400 500 600 700 800 900
Average Product Temperature (˚F)
Net watts = 3.4885 x 10 -12 [(T h + 460) 4 - (T p + 460) 4 ]
in 2
T h = Heater Temperature (˚F)
T p = Product Temperature (˚F)
Heater Temperature (˚F)
1400
1300
7