Page 37 - Practical Technology 2025

nd
Clinical Pharmacy-Pharm D Level Three 2 Semester 2024/2025 Pharmaceutical Technology (PT 607)

C. Fim Evaporators
They are called film evaporators because the solution is spread as a film
formed naturally or by mechanical means over the heated surface (tubes
wall) (Why?)

To increase the heat transfer surface area (A), and the heat transfer rate (Q)

so the rate of evaporation increases.

They include:

1. Climbing (ascending) film evaporator

2. Falling (descending) film evaporator

1) Climbing (Ascending) film evaporator
1 Evaporator 6 Concentrate

body

2 Open-ended 7 Vent

tubes

3 Steam 8 Cyclone

separator

4 Feed 9 Vapors

5 Condensate

Explain why climbing film evaporator is used for evaporation of
thermolabiles?
3. Because of the high heat transfer rate, a small temperature

difference (T) is sufficient.

4. The time of contact between the liquid and the heating surface
(tubes wall) is very short (seconds not hours as other
evaporators).

35