Related Questions

Thermal conductivity based continuous flue gas analyser makes use of varying thermal conductivity of the constituents of flue gases. Which of the following constituents of flue gases has the maximum thermal conductivity?
A CO2
B N2
C O2
D CO
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by
A Painting the surface black
B Painting the surface white (with aluminium paint)
C Giving the surface a mirror finish
D Roughening the surface
In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)
A α = 1; ε ≠ 1
B α ≠ 1, ε = 1
C α ≠ 1, ε ≠ 1
D α = 1; ε = 1
Heat transfer by radiation from a hot body will be most rapid, if its surface is __________ because of its higher emissivity.
A White & rough
B Black & rough
C White & polished
D Black & polished
Emissivity of a white polished body in comparison to a black body is
A Higher
B Lower
C Same
D Depends upon the shape of body
Total emissivity of polished silver compared to black body is
A Same
B Higher
C More or less same
D Very much lower
The changes in the reflectivity/emissivity with time, is called:
A Spectral variation
B Spatial variation
C Temporal variation
D None of these
Ceramic coating material for furnace refractory, which increases its emissivity and thus the radiation heat transfer rate in the furnace, comprises of
A Graphite powder
B Thoria
C Zircon powder
D Beryllium
The emissivity for a black body is
A 0
B 0.5
C 0.75
D 1
Absorptivity of a body will be equal to its emissivity
A At all temperatures
B At one particular temperature
C When system is under thermal equilibrium
D At critical temperature

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