Pharmaceutical Heat Transfer, Drying and Size Reduction FAQ
1. Reynolds Number and Importance
1. What is Reynolds number? Give its importance. Reynolds number is a dimensionless number used to predict flow patterns in fluid dynamics. It is the ratio of inertial forces to viscous forces. A low Reynolds number indicates laminar flow, while a high number indicates turbulent flow. It helps in designing and analyzing fluid flow systems.
2. Heat Exchangers and Types
2. What are heat exchangers? Give their types. Heat exchangers are devices used to transfer heat between two or more fluids without mixing them. Types include:
- Shell-and-tube heat exchangers
- Plate heat exchangers
- Finned-tube exchangers
- Double-pipe heat exchangers
They are used in heating, cooling, and energy recovery applications in pharmaceutical industries.
3. Evaporation and Evaporator Types
3. Define evaporation. Classify evaporators. Evaporation is the process of converting liquid into vapor by heating. It is used in the concentration of solutions. Evaporators are classified into natural circulation and forced circulation types. Examples include short-tube, long-tube, and climbing-film evaporators.
4. Applications of Drying
4. Give the applications of drying. Drying is used to remove moisture from materials. Applications include preservation of drugs, improvement of product stability, and reduction in transportation costs. It also aids in improving powder flow properties and compressibility.
5. Modes of Size Reduction
5. Describe the modes of size reduction. Size reduction can occur through cutting, compression, impact, and attrition. Each method depends on the type of material. For example, fibrous materials are reduced by cutting, while brittle materials are broken by compression or impact.
6. Mechanism of Size Reduction
6. What is the mechanism of size reduction? The mechanism of size reduction includes cutting, impact, attrition, and compression. Each material responds differently to these forces. Selection of the mechanism depends on material hardness, moisture content, and structure.
7. Applications of Filtration
7. Give applications of filtration. Filtration is used for separating solids from liquids. It is essential in water purification, sterile filtration in injectable preparations, and clarification of liquids. It ensures product purity and safety.
8. Drying Curve Phases
8. What is drying curve? A drying curve represents the rate of moisture removal versus time. It has three phases: constant-rate period, falling-rate period, and equilibrium moisture content. Understanding it helps in optimizing the drying process.
9. Corrosion Definition and Example
9. Define corrosion with example. Corrosion is the deterioration of metals due to chemical reactions with the environment. An example is the rusting of iron in the presence of moisture and air. It reduces material strength and lifespan.
10. Sieve Number Meaning
10. What is sieve number? Sieve number indicates the number of openings per linear inch in a sieve. It determines particle size range during size separation. Smaller numbers correspond to larger openings.
11. Filter Aid Definition
11. What is filter aid? Filter aids are substances added to improve filtration by preventing clogging of the filter medium. Common examples include diatomaceous earth and Celite. They improve clarity and flow rate.
12. Heat Exchanger Definition
12. What is heat exchanger? A heat exchanger is equipment used to transfer heat between two or more fluids without allowing them to mix. Types include shell-and-tube and plate exchangers. It is vital in heating and cooling systems.
13. Applications of Evaporation
13. Give applications of evaporation. Evaporation is used to concentrate solutions, remove solvents, and recover active ingredients. It is common in the production of syrups and extracts and helps enhance product stability.
14. Molecular Distillation Principle
14. Explain the principle of molecular distillation. Molecular distillation operates under high vacuum with a short path to separate thermally sensitive compounds. It relies on differences in molecular mean free path and is useful in purifying vitamins and oils.
15. Sieve Shaker Function
15. What is sieve shaker? A sieve shaker is a mechanical device used to separate particles based on size. It provides uniform vibration to sieves for effective separation and enhances reproducibility and accuracy.
16. Heat Transfer Mechanisms
16. Give heat transfer mechanisms. The main mechanisms of heat transfer are conduction, convection, and radiation. Conduction occurs through solids, convection through fluids, and radiation through electromagnetic waves. All are important in pharmaceutical operations.
17. Size Separation Mechanisms
17. Give mechanism of size separation. Size separation mechanisms include sieving, sedimentation, and elutriation. Sieving is most common for dry powders. Each method is chosen based on particle size and density.
18. Ball Mill and Fibrous Materials
18. Ball mill is not useful for size reduction of fibrous material. Explain. Fibrous materials resist the impact and cutting forces applied in a ball mill. They tend to entangle and do not break easily under compression. Hence, ball mills are inefficient for such materials.
19. Manometers and Types
19. What are manometers? What different types of manometers do you know? Manometers measure pressure using columns of liquid. Types include U-tube, inclined, and digital manometers. They are used to measure gas pressure and fluid flow.
20. Fourier’s Law Statement and Equation
20. Give statement along with equation for Fourier’s law. Fourier’s law states that the rate of heat transfer by conduction through a material is proportional to the temperature gradient. Mathematically: q = -k A (dT/dx), where k is the thermal conductivity, A is the area, and dT/dx is the temperature gradient.
21. Plate and Frame Filter Description
21. Draw neat and labelled diagram for plate & frame filter. The plate and frame filter consists of alternate plates and frames arranged in a stack. A filter medium is placed between each plate and frame. Liquids pass through under pressure, leaving solids behind.
22. Reynolds Experiment and Significance
22. Explain the Reynolds experiment, give its significance. Reynolds’ experiment demonstrates flow regimes in a fluid. By observing dye patterns in a tube, laminar or turbulent flow is identified. It helps understand flow behavior in pipelines and scaling between laboratory and industrial systems.
23. Evaporation vs Distillation vs Drying
23. Differentiate between evaporation, distillation and drying. Evaporation removes solvent by heating, distillation separates components based on boiling point differences, and drying removes moisture from solids. Each has distinct principles and applications.
24. Cyclone Separator Principle and Working
24. Explain principle, construction and working of cyclone separator. A cyclone separator uses centrifugal force to separate particles from gas. Air enters tangentially, creating a vortex. Heavier particles move outward and fall into the dust collection area, while cleaned air exits from the top.
25. Fluidized Bed Dryer Principle and Uses
25. Explain principle, construction, working & uses of fluidized bed dryer. In a fluidized bed dryer, hot air is passed at sufficiently high velocity through a bed of particles. The particles become suspended (fluidized), increasing surface area for drying. It is widely used for drying granules and powders in pharmaceutical production.