Steam is supplied to the jacketed kettle in which the aqueous extract is placed. Heat is transferred to the extract by conduction and convection. 

1. EVAPORATIO
N
Steamjacketed kettle
Principle
Construction
Working
Applications

2. STEAM JACKETED KETTEL
Principle:
Steam is supplied to the
jacketed kettle in which the
aqueous extract is placed.
Heat is transferred to the
extract by conduction and
convection.
The temperature raises and
the escaping tendency of the
solvent molecules into
vapour increases. Stirring
further enhances the
vaporization of solvent
molecules.


3. Construction
 Copper is the excellent material for the kettle
because of its conductivity. Iron is used for
construction of jackets since it has minimum
conductivity.
 One round, hemispheric bowl is sealed within
another, with about 2" of space between the
bowls.
 The space is filled with steam.
 Steam pressure can be adjusted: increased
for faster cooking, decreased for slower.
 Baffles on the exterior bowl (jacket) distribute
heat evenly throughout the kettle.

4. Working:
 Aqueous extract to be evaporated is placed in the kettle.
 Steam is supplied through inlet. Steam gives out its heat to
the contents and the condensates leaves through the outlet.
 The contents must be stirred manually for smaller volumes
and mechanically for larger volumes. The rate of evaporation
is fast in the initial stages and decreases gradually as the liquid
gets concentrated.
 The kettle may be fixed or made to tilt. A kettle of capacity up
to about 90 litres may be made to tilt. But above this capacity,
the weight of pan along with its contents becomes too great to
tilt. hence, the bottom outlet is used to collect the concentrated
product.

5.  Advantages
 Used for both small
scale & large scale
operation.
 Simple in
construction and
easy to operate.
 Low maintenance &
installation cost.
 Wide variety of
materials.
 Disadvantages
 Heat economy is
less.
 Not suitable for
heat sensitive
materials.
 Heat decreases on
product
concentration.
 Since, open type so
vapor passes to
atmosphere.

6. Applications
 Evaporating pan is suitable for concentrating
aqueous and thermostable liquors
 Example: Liquorice extract.

7. MULTIPLE CHOICE QUESTIONS
1) To prevent rusting of the jacket …… is either tinned or
enameled on inner surface.
a) Zinc
b) Aluminium
c) Iron
d) Copper
2) The smaller quantities jacket/kettle is made up of
a) Double sheet of metal
b) Single sheet of metal
c) Both a&b
d) None of thise

8. 3) Steam jacket evaporating pan is known as
a) Horizontal tube evaporator
b) Vertical tube evaporator
c) Steam jacket kettle
d) Short tube evaporator
4) Which is an excellent material for kettle
a) Copper
b) Zinc
c) Aluminium
d) Gold
5) The contents must be stirred manually for…….
a) Smaller volume
b) Larger volume
c) Both a&b
d) None of these
6) The heat economy of evaporating pan is……
a) High
b) Normal
c) Less
d) None of these

9. 7) The content must be stirred mechanically for…..
a) Smaller volume
b) Normal volume
c) Larger volume
d) All of the above
8) The capacity of kettle is upto……..litres may be made to tilt.
a) 90
b) 120
c) 70
d) 60
9) The cost of installation and maintainance of steam jacket evaporating pan is
a) Low
b) Medium
c) High
d) None of these
10) ……..is can not be created in open type evaporator
a) Vapour pressure
b) Temperature
c) Energy
d) Reduced pressure