Fluid Flow PDF

BASICS AND APPLICATION OF  Introduction History and OVERVI Background Unit Operation and EW Unit Process Classification Application  INTRODUCTI ON  Unit Operations gives ide...

BASICS AND APPLICATION OF  Introduction History and OVERVI Background Unit Operation and EW Unit Process Classification Application  INTRODUCTI ON  Unit Operations gives idea about specific physical operation; different equipments-its design, material of construction and operation; calculation of various physical parameters (mass flow, heat flow, mass balance, power and force etc.).  In Pharmaceutical Engineering a unit operation is a basic step in a process.  Unit operations involve a physical change or chemical transformation such as separation, crystallization, evaporation, filtration, polymerization, isomerization, and other reactions.  Classificat ion 1 2 3 4 5 6 7 8 9 1 1 0 1 Flow Heat Filtratio Size Mixing Extractio Distillati Evaporati Dryin Centrifugati Reductio of Crystalizatio of and n on on g n on n n Fluid Mass Solids Transfe r  UNIT 1 Flow of Fluid Definition of Fluid flow What is Fluid Flow? Fluid Flow is a part of fluid mechanics and deals with fluid dynamics. It involves the motion of a fluid subjected to unbalanced forces. This motion continues as long as unbalanced forces are applied. For example, if you are pouring water from a mug, the velocity of water is very high over the lip, moderately high approaching the lip, and very low at the bottom of the mug. The unbalanced force is gravity, and the flow continues as long as the water is available and the mug is tilted. Types of Flow Ideal fluid A fluid is said to be ideal when it cannot be compressed and the viscosity doesn’t fall in the category of an ideal fluid. It is an imaginary fluid which doesn’t exist in reality. Real fluid All the fluids are real as all the fluid possess viscosity. Newtonian fluid When the fluid obeys Newton’s law of viscosity, it is known as a Newtonian fluid. Non-Newtonian fluid When the fluid doesn’t obey Newton’s law of viscosity, it is known as Non-Newtonian fluid. Types of Fluids.. contds Ideal plastic fluid When the shear stress is proportional to the velocity gradient and shear stress is more than the yield value, it is known as ideal plastic fluid. Incompressible fluid When the density of the fluid doesn’t change with the application of external force, it is known as an incompressible fluid. Compressible fluid When the density of the fluid changes with the application of external force, it is known as compressible fluid.  Compressible vs incompressible flow Compressible Flow of fluid or gas is the changes in density in changes of pressure or temperature. However, in many situations the changes in pressure and temperature are sufficiently small that the changes in density are negligible. In this case the flow can be modelled as an incompressible flow. Otherwise the more general compressible flow equations must be used. Newtonian vs non-Newtonian fluids All fluids are viscous, meaning that they exert some resistance to deformation: neighboring parcels of fluid moving at different velocities exert viscous forces on each other. Isaac Newton showed that for many familiar fluids such as water and air, the stress due to these viscous forces is linearly related to the strain rate. Non-Newtonian fluids have a more complicated, non-linear stress-strain behaviour. The sub-discipline of rheology describes the stress-strain behaviours of such fluids, which include emulsions and slurries, some viscoelastic materials such as The table below represents the density and viscosity of different types of fluids Types of fluid Density Viscosity Ideal fluid Constant Zero Real fluid Variable Non-zero Newtonian fluid Constant/ Variable T=u(du/dy) Non-Newtonian Constant/ Variable T≠u(du/dy) fluid Incompressible Constant Non-zero/ zero fluid Compressible fluid Variable Non-zero/ zero Types of Fluid Flow Fluid flow has all kinds of aspects — steady or unsteady, compressible or incompressible, viscous or non-viscous, and rotational or irrotational, to name a few. Some of these characteristics reflect the properties of the liquid itself, and others focus on how the fluid is moving. Steady or Unsteady Flow Fluid flow can be steady or unsteady, depending on the fluid’s velocity: Steady: In steady fluid flow, the velocity of the fluid is constant at any point. Unsteady: When the flow is unsteady, the fluid’s velocity can differ between any two points Viscous or Non-viscous Flow Liquid flow can be viscous or non-viscous. Viscosity is a measure of the thickness of a fluid, and very gloppy fluids such as motor oil or shampoo are called viscous fluids. Fluid Flow Equation Mass flow rate is the rate of movement of a massive fluid through a unit area. In simple words it is the movement of mass per unit time. The formula for mass flow rate is given as follows: Mass flow rate=ρAV From the equation, we can see that mass flow rate depends on the density, velocity and the area of cross-section of the fluid.  Reynolds number It is used for measurement and type of flow determination. Re = D× u × density of liquid/Viscosity of fluid D= diameter of pipe, u = Average velocity When Re4000 then flow is turbulent Re is 2000–4000 then flow is laminar or turbulent Critical velocity It is defined as average velocity of any fluid at which viscous flow changes into turbulent flow. Manometers These are the devices which are use for measuring the pressure difference. 1.Simple manometer: It helps in measuring the consumption of gases in the chemical reaction. 2.Differential manometer (two-fluid U-tube manometer): It useful for measuring small gas pressure.  Fluid Dynamics: Bernoulli’s Theorem Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed. Bernoulli's principle: At points along a horizontal streamline, higher pressure regions have lower fluid speed and lower pressure regions have higher fluid speed. The variables P1, v1, h1 refer to the pressure, speed, and height of the fluid at point 1, whereas the variables P2, v2, h2 refer to the pressure, speed, and height of the fluid at point 2 as seen in the diagram Measurement of rate of flow of fluidsweighing or 1.Direct measuring 2.Hydrodynamic methods Pum ps These are mechanical devices use to increase the pressure energy of a liquid. A. Reciprocating pumps: These are used for injection of inhibitors in polymerization units and corrosion inhibitors to high pressure system. C. Peristaltic pump: It contains silicone rubber tube in a U-shape against roller is clamped. Use: It is used for pumping emulsions, creams in pharmaceutical industry and pumping parenteral nutrition infusions to patient and blood pumping for surgical operation.