(SEM III) THEORY EXAMINATION 2025-26 PHARMACEUTICAL ENGINEERING

SECTION A – Short Answer Section

This section contains short conceptual questions related to pharmaceutical engineering principles such as drying, evaporation, centrifugation, fluid flow, and corrosion. These questions test the basic understanding of engineering concepts used in pharmaceutical manufacturing and processing.

Question 1: Define Raoult’s Law.

Answer:
Raoult’s law states that the partial vapor pressure of a component in an ideal solution is directly proportional to its mole fraction in the solution.

Formula:

PA=XA×PA0P_A = X_A \times P_A^0PA​=XA​×PA0​

Where:

PAP_APA​ = Vapor pressure of component in solution

XAX_AXA​ = Mole fraction of component

PA0P_A^0PA0​ = Vapor pressure of pure component

Question 2: What is Critical Moisture Content?

Answer:
Critical moisture content is the moisture level at which the drying rate begins to decrease during the drying process. Above this point, drying occurs at a constant rate, but below it the drying rate falls.

Question 3: Explain Bernoulli’s Equation.

Answer:
Bernoulli’s equation describes the relationship between pressure, velocity, and height of a fluid in motion.

Equation:

P+12ρv2+ρgh=constantP + \frac{1}{2} \rho v^2 + \rho gh = constantP+21​ρv2+ρgh=constant

Where:

PPP = Pressure

ρ\rhoρ = Density of fluid

vvv = Velocity of fluid

ggg = Gravitational acceleration

hhh = Height

It is used in fluid flow measurement devices.

SECTION B – Long Answer Section

This section requires detailed explanations of pharmaceutical engineering equipment such as mills, filters, and dryers used in pharmaceutical manufacturing.

Question 1: Explain the Principle and Working of a Ball Mill.

Answer:

A ball mill is a device used for size reduction of solid materials.

Principle:
It works on the principle of impact and attrition.

Construction:

A cylindrical shell made of steel.

Filled with steel or porcelain balls.

Rotates on its axis.

Working:
As the cylinder rotates, the balls rise and fall, crushing the material into smaller particles.

Advantages:

Suitable for fine grinding

Can handle large quantities

Disadvantages:

High energy consumption

Wear of balls

Question 2: Explain Membrane Filters.

Answer:

Membrane filtration is used for sterilization of heat-sensitive pharmaceutical products.

Principle:
It works by separating particles based on pore size of the membrane.

Construction:

Thin polymer membrane

Pore size typically 0.22 µm

Working:
Liquid is passed through the membrane and microorganisms are retained.

Applications:

Sterilization of injections

Filtration of vaccines

Question 3: Explain Fluidized Bed Dryer.

Answer:

Fluidized bed dryer is used to dry powders and granules in pharmaceutical industries.

Principle:
Air is passed upward through the powder bed, causing particles to behave like a fluid.

Working:
Hot air flows through the material and removes moisture rapidly.

Advantages:

Uniform drying

Short drying time

Disadvantages:

Not suitable for very sticky materials

SECTION C – Descriptive Section

This section tests deeper knowledge of heat transfer, drying mechanisms, plant design, and corrosion prevention in pharmaceutical industries.

Question 1: Explain the Rate of Drying Curve.

Answer:

The drying process occurs in different stages:

Constant Rate Period:
Moisture evaporates rapidly from the surface.

Falling Rate Period:
Moisture movement from inside the material becomes slower.

Final Drying Period:
Remaining moisture is removed slowly.

This curve helps determine drying efficiency and drying time.

Question 2: Explain Types of Corrosion.

Answer:

Common types of corrosion include:

Galvanic Corrosion:
Occurs when two different metals are in contact.

Pitting Corrosion:
Localized corrosion forming small holes.

Stress Corrosion:
Occurs due to combined action of stress and corrosive environment.

Prevention methods:

Protective coatings

Use of corrosion-resistant materials

Cathodic protection

Question 3: Explain the Concept of Film and Overall Heat Transfer.

Answer:

Heat transfer occurs through three mechanisms:

Conduction: Heat transfer through solids.

Convection: Heat transfer through fluids.

Radiation: Heat transfer through electromagnetic waves.

In heat exchangers, heat passes through thin films on both sides of a surface. The total resistance to heat flow is called overall heat transfer resistance.

This concept is important in evaporation, drying, and heat exchanger design.