Which is the most suitable for the con-certration of highly concentrated solution?

The correct answer is:

C. Agitated film evaporator

🔍 Explanation:
When dealing with highly concentrated or viscous solutions, the agitated film evaporator is the most suitable because:

✅ It forms a thin film of liquid on the heated surface, allowing efficient evaporation.

✅ Mechanical agitation improves heat transfer and prevents fouling or crust formation.

✅ It works well for heat-sensitive and viscous fluids.

✅ Suitable for final stages of concentration where viscosity is high.

❌ Why not the others?
A. Open pan evaporation:

Low efficiency, large heat loss, and not ideal for viscous or heat-sensitive materials.

B. Long tube vertical evaporator:

Best for low-viscosity fluids; struggles with thick, concentrated solutions due to flow resistance and poor heat transfer.

✅ Correct Answer:
C. Agitated film evaporator