Q1.
(a)
A rigid tank whose volume is 0.75 m3 developed a small hole on its wall. Air from the surroundings at 1 bar 25°C leaked in and finally the pressure in the tank reached 1 bar. The process occurred slowly so that heat transfer between the tank and the surroundings kept the temperature of the air inside the tank constant at 25°C. Determine the heat transfer involved in the process:
(i) if initially the tank was evacuated,
(ii) if it contained air at 0.7 bar and 25°C.
(b)
(i) Distinguish between skin friction drag and pressure drag. Does the total drag acting on a body necessarily decrease as a result of streamlining ? Explain.
(ii) With a neat sketch explain the principle and working of a pitot tube.
(c) (i) Two concentric spheres have diameters of 0.3 m and 0.8 m and are maintained at uniform temperatures of 700 K and 400 K respectively. The inner and outer spheres have emissivities of 0.5 and 0.7 respectively. The emissivity of the outer surface is 0.35. The surrounding medium and surrounding surfaces are at a temperature of 30°C. Determine the net radiation heat transfer between the two spheres. Also determine the convective heat transfer coefficient at the outer surface.
