Part A (20 x 2 = 40 Marks)
Part B (5 x 12 = 60 Marks)
(ii) Derive from fundamentals the expression for steady state equimolal counter diffusion of gas A through another gas B. (8)
(b) Methane diffuses at steady state through a tube containing helium. At point 1, the partial pressure of methane is PA1 = 55 kPa and at point 2, 0.03 m apart PA2 = 15 kPa. The total pressure is 101.32 kPa and the temperature is 298 K. At this pressure and temperature, the value of diffusivity is 6.75 x 10-5 m2/sec.
(i) Calculate the flux of CH4 at steady state for equimolal counter-diffusion.
(ii) Calculate the partial pressure at a point 0.02 m apart from point 1.
(b) Write short notes on:
(i) Film theory
(ii) Surface renewal theory
(iii) Penetration theory
(ii) What are the different types of cooling towers used in industries? Briefly explain them.
(b) The temperature of air in a room is 40.2oC and the total pressure is 101.3 kPa abs. The air contains water vapor with a partial pressure PA = 3.74 kPa. Calculate
(i) the humidity
(ii) the saturation humidity and percentage humidity
(iii) the percentage relative humidity
(b) In a textile mill, wet cloth passes through a hot air drier. The cloth enters with 90% moisture regain and leaves at 6% moisture regain at a speed of 1.15 m/sec. The width of the cloth is 120 cm and its density on bone-dry basis is 0.095 kg/m2. The temperature of the cloth leaving the drier is 368 K. The ambient air enters the dryer at 303 K DB and 298 K WB while the hot air leaves the dryer at 393 K DB and 328 K WB. Calulate:
(i) the bone-dry production of the dryer
(ii) the evaporation taking place in the dryer and
(iii) the air circulation rate.
(ii) What are the parameters controlling the crystal size distribution in a crystallizer? Explain them briefly.
(b) A solution of sodium sulfate in water is saturated at a temperature of 40oC. Calculate the weight of crystals and the percentage yield obtained by cooling this solution to a temperature of 5oC.The solubilities are as follows: