Final control questions on the subject “heat engineering” The purpose and function of the subject. Working parameter. Status parameters. Base words and phrases

Basic laws of heat radiation 
Planck's law.
 
Absolute black bodies emit light of all wavelengths into space at a 
temperature above absolute zero. At the same temperature, the radiation speed of 
absolute black bodies is higher than that of other real bodies. The dependence of 
radiation speed J,o on wavelength and temperature T is determined by Planck's 
law: 
1
5
1
)
1
(
2
1



T
C
o
e
c
J



(10.5) 
where: C
1
=0.374∙
10-15 
W∙m
2
; S
2
=1.4388∙10
-2
m∙K – Planck's constants; e is the 
base of the natural logarithm. 
The distribution of radiation speed by wavelength and temperature based on 
Planck's law is shown in Figure 10.2. 
 
Figure 10.2. Dependence of absolute black body radiation speed on 
wavelength and temperature 
 
Vin's law.
 
As can be seen from Figure 10.2, if the body's temperature is 
increased, the maximum of its light propagation speed shifts to the short wave 
direction. This law was proposed by V. Vin in 1893 and gave its mathematical 
expression: 

---


max
=0,0028989/T 
or 
T

max
=v=2,898

10
-3
m

K
(10.6) 
This is called V. Winn's displacement law. According to the shift law, the speed of 
electromagnetic waves emitted by objects in the form of light varies at different 
temperatures. For example, when the temperature of an electric heater is T=1100 K, 
it emits light with a wavelength of λ
max
=3∙10
-6
m, whose spectrum consists mainly 
of infrared light. If we take the wave spectrum of sunlight (T=5500 K), its 
wavelength corresponds to λ
min
=5∙10
-7
m. This wavelength corresponds to the visible