The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10-8 W/m2.K4) ?

Related Mcqs:

1. Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K) ?

   A. t4
   B. T4
   C. 1/t4
   D. 1/T4

2. The Stefan-Boltzmann constant depends on the_________________?

   A. Medium
   B. Temperature
   C. Surface
   D. None of these

3. The value of Stefan-Boltzmann constant in SI unit is_________________?

   A. 5.6697 × 10-8W/m2.°K4
   B. 0.1714 × 10-8W/m2.°K4
   C. 5.6697 × 10-8kcal/m2. °K4
   D. 0.1714 × 10-8kcal/m2. °K4

4. Stefan-Boltzmann law applies to _____________ body?

   A. Black
   B. White
   C. Grey
   D. Any colour

5. The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?

   A. 11.2 kW/m2
   B. 12.0 kW/m2
   C. 14.6 kW/m2
   D. 16.5 kW/m2

6. Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because___________________?

   A. Convection becomes important
   B. Conduction becomes important
   C. Radiation becomes important
   D. Sub-cooled boiling occurs

7. A _____________ surface has the maximum thermal emissivity out of the following ?

   A. Black & smooth
   B. Black & rough
   C. White & smooth
   D. White & rough

8. Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be_________________?

   A. 0.35
   B. 0.45
   C. 0.55
   D. 0.85

9. 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

10. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _____________ law?

    A. Parabolic
    B. Hyperbolic
    C. Linear
    D. Logarithmic