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Reg. No. : .................................... Name : .........................................
Third Semester B. Tech. Degree Examination, November 2009 (2008 Scheme) BIOTECHNOLOGY AND BIOCHEMICAL ENGINEERING BRANCH 08.304 : Principles of Momentum Transfer (B) Time : 3 Hours
Max. Marks : 100
Instructions : 1) Answer all questions in Part A. 2) Answer any one full question from each Module in Part B. 3) Each question in Part A carries 4 marks. PART – A 1. Compare positive displacement pumps with centrifugal pumps. 2. Explain hydrostatic equilibrium and give the hydrostatic equation. 3. Discuss briefly about the different pipe fittings used in industries. List four types of valves used in pipe line with their specific use. 4. Water is flowing through a pipe of 40 cm diameter and 600 m long pipe. The head loss due to friction is 6m of water. Determine the flow rate of water. The friction factor is 0.004. 5. Air at 37.8°C and 101.3 kPa, abs pressure flows at a velocity of 23 m/s past a sphere having a diameter of 42 mm. What is the drag force on the sphere if the drag coefficient on the sphere is 0.47 at the flow Reynold’s number ? 6. Explain sphericity and shape factor. 7. Define drag coefficient. With a neat sketch discuss how drag coefficient varies with particle Reynold’s number. 8. Write a note on bubbling fluidization. 9. Explain the power curves in mixing and agitation. 10. Explain how terminal settling velocity of particles in hindered settling is evaluated. (10×4=40 Marks) P.T.O.
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PART – B Module – I 11. a) Certain oil flowing through a 15 cm steel pipe at a rate of 1500 litres/min, inserted in this is a standard sharp edged orifice, which is attached to a mercury manometer ? At the flow temperature, the oil has a specific gravity of 0.8 and a viscosity of 15 cP. What would be the manometer reading, for an orifice coefficient of 0.62 and the density of mercury is 13.69 g/cm3 ? b) Explain the criterion to identify the regime in which the motion of a particle lies. c) Derive the Bernoulli equation from fundamentals.
(8+4+8=20 Marks)
12. a) Explain the principle and working of a Couette viscometer. b) Discuss the factors affecting the viscosity of fermentation broths. c) Water with a density of 998 kg/m3 is flowing at a steady mass flow rate through a uniform diameter pipe. The entrance pressure of the fluid is 68.9 kN/m2. abs in the pipe, which connects to a pump that actually supplies 155.4 J/kg of fluid flowing in the pipe. The exit pipe from the pump is the same diameter as the inlet pipe. The exit section of the pipe is at a level 3.05 m higher than the entrance and the exit pressure is 137.8 kN/m2 absolute. The Reynold’s number in the pipe is above 4000 in the system. Determine the frictional loss in the pipe system. (5+5+10=20 Marks) Module – II 13. a) Develop an expression to find the pressure drop at minimum fluidization. b) Water at 24°C is flowing past a long cylinder at a velocity of 1 m/s in a large tunnel. The axis of the cylinder is perpendicular to the direction of flow. The diameter of the cylinder is 90 mm. Compute the drag force per meter length of the cylinder. The following data is available Density of water is 997.2 kg/m3 Viscosity of water is 0.914 CP Drag coefficient is 1.40
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c) A bed of ion exchange beads 2.44 m deep is to be backwashed with water to remove dirt. The particles have a density of 1.24 g/cm3 and an average size of 1.1 mm. What is the minimum fluidization velocity using water at 20°C and what velocity is required to expand the bed by 25% ? The beads are assumed to be spherical and the porosity at the minimum fluidization velocity is 0.4. The following relationship between superficial velocity and bed porosity is available. V 0 H m , where V 0 is the superficial velocity, H is the bed porosity and m can be taken as 4. (5+7+8=20 Marks) 14. a) Derive Ergun equation. List the important assumptions involved in deriving the equation. b) A water softener consists of a vertical tube 5 cm diameter and packed to a height of 50 cm with ion exchange resin particles. The particles may be considered spherical with a diameter of 0.125 cm. Water flows over the bed by gravity as well as pressure difference at the rate of 0.3 cm3/s. The bed has a porosity of 0.3. Determine the pressure gradient. (10+10=20 Marks) Module – III 15. a) Explain the need of determining particle size distribution and also discuss the differential and cumulative method of size analysis. b) A tank of 1.2 m in diameter and 2 m high is filled a depth of 1.2 m with a solution having a viscosity of 10 poise and a density of 800 kg/m3. The tank is not baffled. A three bladed 360 mm diameter propeller is installed in the tank 36 cm from the bottom. The pitch is 1 : 1. The motor develops 8 kW. Is the motor adequate to drive the agitator at a speed of 800 rpm ? (10+10=20 marks) 16. a) Develop an expression for the bubble diameter when a single bubble issues from a submerged circular orifice in a quiescent liquid. b) How does the power consumption by turbine impeller in agitating a liquid compare with the power consumption in dispersing a gas in the liquid ? c) It is planned to disperse 2.271 m3/h of benzene in 22.71 m3/h of water at 20 °C with an average drop size of 15 microns using a pipe disperser of 77.93 mm diameter. Determine the diameter of the orifice required for this. The densities of pure water and Benzene are 1000 kg/m3 and 879 kg/m3 respectively. The interfacial tension between Benzene and water at 20 °C is 35 dyne/cm. (5+5+10=20 Marks) ———————