miet gondia

1. VAPOUR ABSORPTION REFRIGERATION
SYSTEMS
Presented By :
Brundaban Sarkar
Section : ME III rd SEM
Roll No. 128
MIET GONDIA
TECHNICAL SEMINAR ON
DEPARTMENT OF MECHANICAL ENGINEERING

2. CONTENTS
• Introduction
• Simple Vapour Absorption System
• Practical Vapour Absorption System
• C.O.P of Ideal Vapour Absorption System
• Properties of Ideal Refrigerant and Absorbent
• Properties of Ideal Refrigerant-Absorbent combination
• Advantages of Absorption system over Compression system
• Domestic Electrolux Refrigerator
• Principle & Working of Domestic Electrolux refrigerator
• Advantages & Disadvantages of Domestic Electrolux Refrigerator

3. INTRODUCTION
• It is a heat operated system.
• It is quite similar to Vapour Compression systems. Condensation and
evaporation takes place at two different pressure levels to achieve refrigeration.
• The main motive is to raise the temperature of the refrigerant from evaporator
pressure to condenser pressure.
• Here refrigerant is dissolved in inert liquid in absorber and pumped to
condenser.
• After raising pressure of refrigerant it is separated from solution by heating.
• After condensation in condenser, refrigerant is throttled by expansion valve and
then it evaporates in evaporator providing the refrigeration effect.

4. SIMPLE VAPOUR ABSORPTION SYSTEM
• Ammonia vapour from evaporator is
absorbed by water in absorber.
Condensation heat released is absorbed by
cooling water.
• After being pumped to generator, heat is
supplied which gives ammonia vapour.
Weak sol. sent back to absorber.
• High pressure vapour is condensed to high
pressure liquid ammonia in condenser.
• Liquid ammonia is throttled by expansion
valve, and then it evaporates absorbing heat
from evaporator.
Simple Vapour Absorption System

5. PRACTICAL VAPOUR ABSORPTION
SYSTEM
Water vapours if reach condenser may block the
expansion valve. Therefore, analyser-rectifier is
used practically.
Analyser : Strong solution flows down the trays.
Due to high saturation temperature water
condenses down and 𝑁𝐻3 vapours escape
through.
Rectifier : A water cooled heat exchanger which
further condenses water vapour. (If any left)
Heat Exchanger : Used to cool weak solution
from generator. It also heats the strong solution
coming from pump, thereby reducing heat to be
supplied at generator, increasing economy.
Practical Vapour Absorption System

6. COEFFICIENT OF PERFORMANCE OF
IDEAL ABSORPTION SYSTEM

7. C.O.P OF IDEAL ABSORPTION
SYSTEM (CONTINUED)
Various energy transfers in VARS

8. C.O.P OF IDEAL ABSORPTION
SYSTEM (CONTINUED)
𝑇 𝐸
𝑇 𝐶−𝑇 𝐸
= C.O.P of Carnot refrigerator working b/w temperature limits 𝑇𝑐&𝑇𝐸.
𝑇 𝐺−𝑇 𝐶
𝑇 𝐺
= C.O.P of Carnot engine working b/w temperature limits 𝑇𝐺&𝑇𝐶.
Thus C.O.P of ideal absorption system,
(𝐶. 𝑂. 𝑃) 𝑚𝑎𝑥 = [ (𝐶. 𝑂. 𝑃) 𝐶𝑎𝑟𝑛𝑜𝑡 ] x [ 𝜂 𝐶𝑎𝑟𝑛𝑜𝑡 ]

9. PROPERTIES OF IDEAL REFRIGERANT
& ABSORBENT
Properties of ideal refrigerant :
• It should boil b/w 2˚-10 ˚C and condense at 40
˚C or above. (pressure around atmospheric)
• Large latent heat of vaporization.
• High critical temperature.
• Low specific heat.
• Stability in complete cycle.
Properties of ideal absorbent :
• Greater affinity for refrigerant.
• Heat released during absorption of refrigerant
should be minimum.
• High boiling point.
• Low specific heat.
• Chemical stability.

10. PROPERTIES OF IDEAL REFRIGERANT-
ABSORBENT COMBINATION
• Refrigerant should have high affinity for absorber at low temperatures & less affinity
at high temperatures.
• Mixture should have low specific heat and viscosity.
• It should be non-corrosive.
• Large difference in normal boiling points of refrigerant and absorbent.
Commonly used combinations in air-
conditioning applications :
• Ammonia-water
• Lithium-bromide water

11. ADVANTAGES OF ABSORPTION SYSTEM
OVER COMPRESSION SYSTEM
• No moving part except pump-motor, which is comparatively smaller than
compressor system.
• Quiet in operation, low maintenance cost.
• Can work only with thermal energy as an input.
• Can be built for huge working capacities. (even for above 1000 TR)
• Can be operated at designed C.O.P’s or even at part loads by varying generator
temperature.
• Space and Auto. control requirements favour absorption system.

12. Sr.
No.
Particulars Vapour Compression
Systems
Vapour Absorption Systems
1. Type of Energy
Supplied
Mechanical – High Grade Heat – Low Grade
2. Energy Supply Rate Low High
3. Wear & Tear More Less
4. Performance at Part
Load
Poor Not affected at Part Load
5. Suitability Used where High Grade
Mechanical Energy is available
Can be used at Remote Places, as can
be used with simple Kerosene lamp
6. Charging of
Refrigerant
Simple Difficult
7. Leakage More chances No chances, as no Compressor or
Reciprocating Part
8. Damage Liquid traces in Suction Line
may damage Compressor
No danger
VAPOUR COMPRESSION VS. VAPOUR ABSORPTION

13. DOMESTIC ELECTROLUX
REFRIGERATOR
• Developed from an invention by “Carl
Munters” & “Baltzer Von Platen”.
• Also known as “Three-fluid absorption
system” and “Munter’s Platen System”.
• Three fluids used are ammonia, hydrogen
and water.
Domestic Electrolux Refrigerator

14. PRINCIPLE & WORKING OF
ELECTROLUX REFRIGERATOR
Principle : If a liquid is exposed to an inert
atmosphere, it will evaporate until atmosphere
becomes saturated with the liquid vapours.
Evaporation thus produces cooling effect.
Working :
• Liquid 𝑁𝐻3 evaporates into 𝐻2 gas at low
temperature in evaporator.
• 𝑁𝐻3 + 𝐻2 mixture enters absorber where 𝑁𝐻3
is absorbed in water, 𝐻2 returns back.
• Strong sol. 𝑁𝐻3 in 𝐻2 𝑂 goes to generator,
where it is heated and vapours then go to water
separator.
• Water separates in separator, weak sol. Sent
back to absorber and 𝑁𝐻3 vapour move to
condenser. After condensation in condenser
𝑁𝐻3 liq. moves to evaporator.
Working cycle of Electrolux Refrigerator

15. POINTS WORTH NOTING
(FOR ELECTROLUX REF.)
• Complete cycle is carried out entirely
by flow of gravity of refrigerant.
• With this type of machine, efficiency is
not important since the energy input is
very small.
• Due to low C.O.P, it cannot be used
for industrial purposes.
ROLE OF HYDROGEN
• Helps in maintaining uniform total pressure
throughout the system.
• Permits the refrigerant to evaporate at low
temperature in evaporator, corresponding to
its partial pressure.

16. ADVANTAGES
(ELECTROLUX REF.)
• No pump/compressor required.
• No mechanical troubles, low
maintenance.
• No lubrication required, no wear-tear.
• Completely leak proof.
• Noiseless.
• Easy control, only by heat input.
• More complicated in construction and
working.
• Low C.O.P.
• If spoiled once, cannot be repaired and
has to be replaced fully.
DISADVANTAGES
(ELECTROLUX REF.)