JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Pharmacy II Year PHARMACEUTICAL ENGINEERING Previous Question Paper (March-2021 - R17)

Bernoulli’s theorem states that for an ideal, incompressible, and non-viscous fluid in steady, streamline flow, the sum of the pressure energy, kinetic energy, and potential energy per unit weight of the fluid remains constant at every point along a streamline.

The mathematical expression for the theorem is:

Where:

• P/ρg represents the pressure head (energy due to fluid pressure).
• v²/2g represents the velocity head (kinetic energy per unit weight).
• z represents the potential head or elevation head (potential energy per unit weight).
• g is the acceleration due to gravity.

The theorem is derived from the principle of conservation of energy. In pharmaceutical engineering, it is fundamental for calculating flow rates, pressure drops, and power requirements in fluid transport systems, such as in the design of piping networks, venturi meters, and orifice meters used to measure the flow of liquid ingredients.

For real fluids, the theorem is modified to account for energy losses due to friction, expressed as:

Where h_f represents the head loss due to friction between two points in the system. This modified form is essential for practical engineering applications where fluid viscosity and pipe roughness cannot be neglected.

A ball mill is a type of grinder used to grind materials into extremely fine powder for use in mineral dressing processes, paints, pyrotechnics, and ceramics. It operates on the combined principle of impact and attrition.

The construction consists of a hollow cylindrical shell mounted on a metallic frame, rotating about its longitudinal axis. The shell is partially filled with grinding media, typically steel or ceramic balls. The diameter of the balls is proportional to the size of the feed material. The shell is fitted with liners to protect it from wear and tear.

The working process involves the following steps:

• The material to be ground is fed into the cylinder along with the grinding balls.
• As the cylinder rotates at a controlled speed, the balls are lifted along the inner walls of the shell due to centrifugal force.
• Upon reaching a certain height, the balls fall back onto the material (impact) and roll over each other (attrition), effectively crushing the particles.
• The speed of rotation is critical; at the critical speed, the balls are carried around the inner periphery without falling, resulting in no grinding. Therefore, the mill is operated at approximately 60-75% of the critical speed.

Applications of the ball mill include:

• Size reduction of hard and abrasive materials.
• Production of fine powders for pharmaceutical formulations.
• Used for both dry and wet grinding processes.
• Effective for achieving very fine particle sizes, often in the range of 10 to 50 micrometers.