Vapour absorption refrigeration systems using water-lithium bromide pair are extensively used in large capacity air conditioning systems. In these systems water is used as refrigerant and a solution of lithium bromide in water is used as absorbent. it is having lot more of advantages like except for two small centrifugal pumps, there are no moving parts so less number of moving parts step less capacity control down to 0%capacity which is not possible with reciprocating machines and centrifugal, No Freon used ,no recharging cost of refrigerant ,which will be quite substantial and inevitable in vapor compression cycle. low working pressure

1. A presentation
on
lithium bromide absorption
refrigeration system
By
Rohan Sharma

2. • Vapour compression refrigeration system
• Lithium bromide
• Vapour absorption refrigeration system
• Working
• Advantages
• Disadvantages
• Future scope
Table of contents

3. At present vapor compression system is widely being
use for refrigeration purpose. The major disadvantages
of this system is that Use of refrigerant increases the
cost and has environmental impact.
Vapour compression refrigeration
system

4.  Being a salt, lithium bromide does not exert any
pressure and does not boil off when heated. Thus
there is no need of rectifier to separate out the
absorbent vapor from the refrigerant vapor.
 The rate of absorption of water vapor comes down
as temperature of the solution increases. The
concentration of a solution does not change with
temperature, its concentration comes down. This is
because the weight of the total solution has
increased on absorbing water, but salt content has
not changed. A stronger solution can absorb more
water vapor than a solution of lower concentration
Lithium bromide

5.  Vapour absorption refrigeration systems using water-lithium
bromide pair are extensively used in large capacity air
conditioning systems. In these systems water is used as
refrigerant and a solution of lithium bromide in water is used
as absorbent.
 it is used only in applications requiring refrigeration at
temperatures above 0oC Since water is used as refrigerant,
using these systems it is not possible to provide refrigeration
at sub-zero temperatures.
 The analysis of this system is relatively easy as the Vapour
generated in the generator is almost pure refrigerant
(water), unlike ammonia-water systems where both
ammonia and water Vapour are generated in the generator.
Vapour absorption refrigeration
system

6. IN ABSORBER AND GENERATOR
 The evaporator and absorber are inter-connected. So
the refrigerant vapor formed in the evaporator is
absorbed by the absorbent in the absorber thereby
maintaining the refrigerant vapor pressure in the
evaporator at the low level required for continuous
vaporization of liquid refrigerator to obtain
refrigeration. To recover the refrigerant from the
absorbent it is pumped from the absorber to the
generator, where it is heated using steam or hot
water.
working

7. Contd.

8.  On getting heated the absorbent
releases the refrigerant vapor as a
high temperature/pressure vapor. It
passes to the comparatively cooler
condenser where it is condensed.
The liquid refrigerant then passes on
to the evaporator thus completing
the refrigerant cycle. The absorbent
flows back from the generator to the
absorber
 Here the condenser is replaced by
the radiator of the vehicle . When the
air cooler is not switched on the hot
coolant water flows into it, when the
AC is switched on it acts as a
condenser for the unit
Contd.
In condensor and evaporator

9. Schematic representation of
refrigeration system

11. Operating conditions
Generator solution temperature = 990C
• Generator solution strength= 63.3%
• Generator solution vapor
pressure=76.2mmHg abs
• Condensing temperature=460C
• Condensing pressure of refrigerant=76.2mmHg abs
• Absorber solution temperature=38.30C
• Absorber solution strength=59.5%
• Absorber solution vapor pressure=6.35mmHg
• Evaporator temperature=4.440C
• Evaporator refrigerant vapor
pressure=6.35mm(0.25”)Hg abs

12.  except for two small centrifugal pumps, there are no
moving parts so less number of moving parts
 step less capacity control down to 0%capacity which
is not possible with reciprocating machines and
centrifugal
 No Freon used
 no recharging cost of refrigerant ,which will be quite
substantial and inevitable in vapor compression cycle
 low working pressure
advantages

13.  low COP
 high heat rejection factor, so requirement of higher
cooling tower and pump capacities
 corrosive nature of lithium bromide corrodes the
heat exchanger
disadvantages

14.  Condensed liquid refrigerant from the condenser can
be used for refrigeration by passing the same
through capillary tube and then to evaporator
 All the accessories of a vehicle can be made to run
with the power obtained from refrigerant turbine,
so as to reduce the energy loss of 2.2%
Future scope

15. Thank you