21. If the temperature of a solid surface change from 27 °C to 627 °C, then find the ratio of its emissive power change?
22. When a liquid flows through a tube with sub-cooled or saturated boiling, what is the process called?
A. Pool Boiling
B. Bulk Boiling
C. Convection Boiling
D. Forced Convection Boiling
23. A wall having to comprise two layers, i.e. layer A and layer B. Find the ratio of the thickness of two layers?
(Given :- Ta = 1325 °C, Tb = 1200 °C, Length (L) = 300 mm, Ka/Kb = 2, Ambient Temp. = 25 °C)
24. A steel plate of thickness 5 cm and thermal conductivity 20 W/mK is subjected to a uniform heat flux of 800 W/m² on one surface A and transfers heat by convection with a heat transfer coefficient of 80 W/m²K from the other surface B into the ambient air at 25 °C. The temperature of the surface B transferring heat by convection is –
A. 25 °C
B. 35 °C
C. 45 °C
D. 55 °C
25. Consider two infinitely long black body concentric cylinders with a diameter ratio D2/D1 = 3. Find the shape factor for the outer cylinder with itself?