12

13

14

b)

a)
b)

a)
b)

F192005 Pages:3

total emissive power?

Calculate the radiation exchange per unit area between two parallel plates of
temperature 400°C and 25°C. Emissivities of hot and cold plates are 0.9 and 0.7
respectively. Find the percentage reduction in heat transfer of a radiation shield
of emissivity 0.25 is placed in between the plates

Discuss Fick’s Law of diffusion

Nitrogen gas is maintained at 3.5 bar and 1 bar on opposite sides of a rubber
membrane which is 0.25 mm thick. The system temperature is 25°C. What is the
molar diffusive flux of nitrogen through the membrane?

Discuss Schmidt No, Lewis No and Sherwood No

Explain steady state equimolar counter diffusion in liquids

Air at 1 atm and 30°C flows over a vessel full of water at velocity 4m/s. The
partial pressure of water vapour present is 0.0070 bar. If water surface is at
temperature of 15°C, calculate the evaporation rate of water. Take Diffusion

coefficient as 25.83x10°m7/s. Saturation pressure of water at 15°C is 0.017 bar.

Page 3 of 3

(7)

(4)
(6)

(5)
(5)
(10)