Artcle by Dr.
L.C.Singal, Prof. (ME Deptt), CEC Landran,
(Mohali), Punjab (India), Formerly Prof in
Chemical Engg. Deptt., Panjab University,
Separation of gases:
Separation of air into its constituents by
fractional distillation. Air is liquefied at
-1910C. Liquefaction temperature of
Nitrogen is -1860C and that of oxygen is -1960C.
Separation of gases in the petroleum industry
(Refinery). Lowest temperature needed is -1600C
and the cooling capacity needed are 10000 tons
Condensation of gases:
Synthetic ammonia plants condense ammonia gas
with temperatures between -200C to
+100C before storage or before
Dehumidification of air:
Low humidity is essential for the production of
Low humidity is essential in the manufacture of
pharmaceuticals, a soap, detergents and
Solidification of a solute:
(i) De-waxing of oil in the petroleum industry
is at about -250C. Low Pressure
Storage in Liquid Form:
(ii) Storing of gases in liquid form permits
many times storage than in the gaseous state
i.e. Natural gas is cooled to -1600C
at 0.7 bars (gauge).
Variety of processes fall under this category
i.e. to cool wax to -250C to harden
it on paper.
Removal of Heat of Reaction:
Many chemical reactions are exothermic (as
mentioned below) but these must take place at
temperatures below atmospheric temperature.
Therefore refrigeration is required to remove
the heat of reaction.
In the manufacture of viscous rayon
In the manufacture of Cellulose acetate
In the manufacture of synthetic rubber
Recovery of solvents:
Numerous solvents can be recovered for reuse by
acetone in film manufacture
Ccl4 in textile manufacture
CS2 in rubber manufacture
Control of Fermentation:
Heat is generated during fermentation and must
be removed otherwise temperature will rise
beyond control i.e. refrigeration maintains 5 to
In the manufacture of alcohol in a brewery
In t5he manufacture of penicillin
Cooling for preservation:
Following will live longer if stored between 5
Preservation of Dairy Products:
Refrigeration can maintain quality and taste.
(i) Milk 2 to 50C
(ii) Ice cream
Meat and poultry products:
in the frozen state
for long storage
(iii) Fish at -150C
Taste is improved on serving while cold
Its water is boiled off while working at vacuum
and low temperature 170C
Pine apple juice etc.
Chocolate and pastry maintain quality and
prevent stikyness at temperatures of 5 to 100C
Food storage and distribution:
(i) Frozen meat
and vegetables -15 to -27 0C
Cold treatment of metals:
The cutting tool can be increased many folds by
refrigerating the tool for 15 minutes at -1000C
Magnetic strength and stability of magnets can
be improved by low temperature treatment at -800C
for 8 hours.
Hoop shrinking at low temperatures
Localized refrigeration as surgical anesthesia
to provide shock less surgery.
Blood plasma and antibiotics are manufactured
using a method called freeze drying
Deliveries taking place in air-conditioned
Dead bodies are preserved at -700C
for few days.
Ice Skating Rinks:
Artificial freezing of ice rinks and not
depending on weather.
Cooling of concrete by refrigeration prevents
cracking especially in the constriction of dams.
Refrigeration cools soil to facilitate
In ice plants
(i) Birth of a child taking place in Air
(ii) Dead bodies are stored for few days when
their family members cannot be present in time
(iii) Blood preservation
(iv) Bone marrow preservation