Heat Transfer Practice Test 5

1. Two spheres A and B of same material have radius 1 m and 4 m, and temperatures 4000 K and 2000 K respectively. Then the energy radiated by sphere A is

2. The value of radiation coefficient or the Stefan-Boltzmann constant is

3. In the given diagram let r be the length of the line of propagation between the radiating and the incident surfaces. What is the value of solid angle W?

4. Amount of heat energy radiated by unit surface of the sun in the same time workout as
Take, R = mean distance of earth from the sun and r = radius of sun

5. A small body has a total emissive power of 4.5 kW/m². Determine its surface temperature of maximum emission

6. A 100 W light bulb has a tungsten filament (emissivity = 0.30) which is required to operate at 2780 K. If the bulb is completely evacuated, calculate the minimum surface area of the tungsten filament

7. For the same type of shapes, the value of the radiation shape factor will be higher when

8. Calculate the radiant flux density from a black surface at 400 degree Celsius?

9. The solid angle is defined by a region by the rays of a sphere, and is measured as

10. If the temperature of a hot body is increased by 50%, the amount of radiations emitted by it would increase by nearly