Notes of pharmaceutical engineering

1. PHARMACEUTICAL ENGINEERING
1. FLOW OF FLUIDS
INTRODUCTION
Fluid is a substancesuch as a gas or a liquid that has no fixed shape and flows easily upon
application of external pressure.
Flow is defined as the action of moving along in a steady, continuous stream. Thus,
Fluid flow is a part of fluid mechanics that deals with fluid dynamics and is a motion of gases
and liquids.
For example, if you are pouring a water from a beaker, the velocity of water is very high over
the edge, moderately high approaching the edge, and very low at the bottom of the beaker. The
unbalanced force is gravity, and the flow continues as long as water is available and the beaker
is tilted.
Viscosityis a measure of the thickness of a fluid, and very gloppy fluids such as motor oil or
shampoo are called viscous fluids.
The volume of fluid replaced in a given interval of time is called the fluid flow rate. It is
expressed as
Mass flow rate = ρAV
Where, ρ = density, V = Velocity and A = area.
Thus, Flow rate = Area × Velocity
Both gas and liquid flow can be measured in volumetric or mass flow rates, such as L/sec or
kg/sec, respectively.
TYPES OF MANOMETERS
The term manometer is derived from the ancient Greek words 'manós', meaning thin or rare,
and 'métron' meaning measure.
A manometer works on the principle of hydrostatic equilibrium and is used for measuring the
pressure (static pressure) exerted by a still liquid or gas.
Following are the advantages of manometers:
 Simple and time proven.
 They have high accuracy and sensitivity.
 Availability of a wide range of filling fluids of varying specific gravities.

2.  It has reasonable cost.
 There are suitable for low pressureand low differential pressure applications.
TYPES OF MANOMETER
1. Simple U-tube Manometer
A manometer is a device to measure pressures. A common simple manometer consists of a U
shaped tube of glass filled with some liquid. In its simplest form, this type of manometer
consists of an incompressible fluid like water or mercury. Typically it is mercury because of its
high density.
2. Differential U-tube Manometer
A differential manometer is a device that measures the difference in pressure between two
places.
The simplest differential manometer is a U-shaped tube with both ends at the same height. A
liquid usually used is water or mercury and it rests at the bottom of the tube. If one end of the
tube is in a place with higher air pressure, the pressure will push down the liquid on that side of
the tube. By measuring the difference between the heights of liquid, it is possible to calculate
the difference in pressure.

3. 3. Inverted U-tube Manometer
The inverted U-tube differential manometer is reciprocal of U-tube differential manometer at
the different level. This type of manometers is used to measure accuracy of small difference if
pressure is increased.
4. Micro Manometer
A micromanometer is used for the accurate measurement of extremely small pressure
differences. The micromanometer is another variation of liquid column manometers based on
the principle of inclined tube manometer.
Micromanometer is a static fluid pressure difference measuring device. Its dynamics can rarely
be ignored. Considering manometric fluid as a free body, the forces acting on it are
 The weight distributed over the entire fluid.
 The drag force due to its motion and the corresponding tube wall shearing stress.
 The force due to differential pressure.
 Surface tension force at the two ends.
5. Inclined Manometer
For accurate measurement of small pressure differences by an ordinary U-tube manometer, it is
essential that the ratio of density of mercury (ρm) to density of water (ρw) should be close to

4. unity. This is not possible if the working fluid is a gas. A manometric liquid of density very
close to that of the working liquid and giving at the same time a well defined meniscus at the
interface is not always possible. Forthis purpose, an inclined tube manometer is used.
REYNOLDS NUMBER AND ITS SIGNIFICANCE
Reynolds number was discovered by an Irish engineer and physicist OsborneReynolds in 1883.
Reynolds number: It is the ratio that shows the effect of viscosity in a given medium which
governs the transition between laminar and turbulent flow.

5. BERNOULLI’S THEOREM AND ITS APPLICATIONS
Bernoulli’s theorem is the principle of energy conservation for ideal fluids in steady or
streamline flow. This theorem describes relation among the pressure, velocity, and elevation in
a moving fluid such as liquid or gas. According to this theorem the compressibility and
viscosity (internal friction) are negligible and the flow is steady, or laminar. First derived
(1738) by the Swiss mathematician Daniel Bernoulli.