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BIO 208 FLUID FLOW OPERATIONS IN BIOPROCESSING [ 3 1 0 4 ]

BIO 208 FLUID FLOW OPERATIONS IN BIOPROCESSING [ 3 1 0 4 ]. SYLLABUS. Fluid statics Fluid dynamics Bernoulli’s equation Hagen Poiseuille's equation Friction factor Flow past immersed bodies Flow thro bed of solids Fluidization Transportation and metering of fluids

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BIO 208 FLUID FLOW OPERATIONS IN BIOPROCESSING [ 3 1 0 4 ]

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  1. BIO 208 FLUID FLOW OPERATIONS IN BIOPROCESSING [ 3 1 0 4 ]

  2. SYLLABUS • Fluid statics • Fluid dynamics • Bernoulli’s equation • Hagen Poiseuille's equation • Friction factor • Flow past immersed bodies • Flow thro bed of solids • Fluidization • Transportation and metering of fluids • Mixing & Agitation

  3. References….. • Unit Operations of Chemical Engineering, 5th edn., McCabe & Smith. • Chemical Engineering, Vol. I, Coulson and Richardson • Introduction to Chemical engineering, Badger and Banchero • Unit Operations, Foust et. al.,

  4. Why?????? • Fluid mechanics is an important area of engg. science. • The nature of flow in pipes and reactors depends on the power input to the system & physical characters of fluid • In fermentors, fluid properties affect process energy requirements & effectiveness of mixing which can have dramatic influence on productivity & the success of equipment scale-up. • Transport of heat and mass is often coupled with fluid flow. • Fluids in bioprocessing often contain suspended solids, consist of more than one phase, and have non-Newtonian properties. • All of these features complicate analysis of flow behavior and present many challenges in bioprocess design.

  5. FLUID…… • A fluid may be defined as a substance that does not permanently resist distortion and, hence, will change its shape. • In this text gases, liquids, and vapors are considered to have the characteristics of fluids and to obey many of the same laws. • In the process industries, many of the materials are in fluid form and must be stored, handled, pumped and processed. • So it is necessary that we become familiar with the principles that govern the flow of fluids and also with the equipment used. • Typical fluids encountered include water, air, CO2, oil, slurries, and thick syrups & BIOPRODUCTS

  6. Compressible & Incompressible • If a fluid is inappreciably affected by changes in pressures it is said to be incompressible. Most liquids are incompressible. • Gases are considered to be compressible fluids.

  7. Momentum Transfer • The study of momentum transfer, or fluid mechanics as it is often called, can be divided into two branches; • fluid statics, or fluids at rest, and • fluid dynamics or fluids in motion. • Since in fluid dynamics momentum is being transferred, the term “momentum transfer” or “transport” is usually used.

  8. Viscosity • The viscosity (m) of a fluid measures its resistance to flow under an applied shear stress. • Representative units for viscosity are • kg/(m.sec) • g/(cm.sec) (also known as poise designated by P) • The centipoise (cP), one hundredth of a poise, is also a convenient unit

  9. The kinematic viscosity (n) is the ratio of the viscosity to the density: • n = m/r, • Has the units of m2/s

  10. Viscosity of liquids: • Viscosity of liquids in general, decreases with increasing temperature. • Viscosity of gases: • Viscosity of gases increases with increase in temperature. • @ 25oC, mwater = 1 cP and • mair = 1 x 10-2 cP

  11. In fig., a stationary column of fluid of ht h2 and constant CSA A, where A=Ao=A1=A2, is shown. The pressure above the fluid is Po (which could be the press of atmos above the fluid) Also for a fluid at rest, the force/unit area (ie Pressure) is the same at all points with the same elevation. Fluid Statics…… Pressure in a static fluid

  12. We know F = mg and P = F/A • Total mass of fluid = h2 A r F=h2A r g P = F /A = h2r g • This is the press on A2 due to the mass of fluid above it. • To get the TOTAL PRESS P2 on A2, the Po must be added P2 = h2r g + Po • To cal P1, P1 = h1r g + Po • The press difference bet 2 and 1 is DP = P2-P1 = (h2 – h1)r g

  13. Since it’s the vertical height of a fluid that determines the press of fluid, the shape of the vessel doesn’t affect the pressure • In the above fig the press P1 at the bottom of all three vessels is the same and equal to h1r g + Po

  14. Prob 1 • A large storage tank contains oil having a density of 917 kg/m3.The tank is 3.66 m tall and is vented (open) to the atmosphere of 1 atm abs at the top. The tank is filled with oil to a depth of 3.05 m (10 ft) and also contains 0.61 m (2.0 ft) of water in the bottom of the tank. Calculate the pressure in Pa and 3.05 m from the top of the tank and at the bottom.

  15. P1 = Po + (hrg)oil = 1.288 x 105 Pa P2 = P1 + (hrg)water = 1.347 x 105 Pa Soln……

  16. Head of a fluid • Expressing the pressure in terms of head in m or ft of a particular fluid • We know….P = hrg • h = P / rg

  17. Prob 2 • Compare the column heights of water,CCl4(r=1.59 g/cc) and mercury (r=13.65 g/cc) corresponding to a pressure of 50kPa • hwater = 5.1m • h CCl4 = 3.21m • hHg = 0.373m

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