Heat Transfer Practice Test 5

1. Isothermal furnaces, with small apertures, approximate a black body and are frequently used to calibrate heat flux gauges.

2. A black body of total area 0.045 m² is completely enclosed in a space bounded by 5 cm thick walls. The walls have a surface area 0.5 m ² and thermal conductivity 1.07 W/ m K. If the inner surface of the enveloping wall is to be maintained at 215 degree Celsius and the outer wall surface at 30 degree Celsius, calculate the temperature of the black body

3. Likewise the amount of emitted radiation is strongly influenced by the wavelength even if temperature of the body is

4. Measurements were made of the monochromatic absorptivity and monochromatic hemispherical irradiation incident on an opaque surface, and the variation of these parameters with wavelength may be approximated by the result shown below. Determine the total hemispherical absorptivity

5. What is the wavelength band for Ultraviolet rays?

6. For a hemisphere solid angle is measured as

7. The absorptivity of black body equals to

8. According to Stefan-Boltzmann law of thermal radiation

9. Radiation emitted by a black surface is a function of wavelength and temperature but is independent of direction.

10. The fraction of the radiative energy that is diffused from one surface element and strikes the other surface directly with no intervening reflections is called
(i) Radiation shape factor
(ii) Geometrical factor
(iii) Configuration factor
Choose the correct answer