The document discusses the intermittent vapor absorption refrigeration cycle. It defines absorption refrigeration as using a heat source like solar energy to drive the cooling process rather than electricity. The cycle works by evaporating a refrigerant like ammonia at low pressure to absorb heat, then absorbing the gaseous refrigerant in a solution, and regenerating it by heating the solution to release the refrigerant gas. Industrial applications include using lithium bromide solutions. Advantages are using waste heat, but disadvantages include lower efficiency than vapor compression refrigeration.

1. CAREER POINT
UNIVERSITY
PRESENTATION ON INTERMITTENT VAPOUR
ABSORPTION REFRIGERATION CYCLE
Submitted by:-
ABHISHEK VERMA
B.Tech /Mechanical
6th Sem/3rd Year
Submitted to:-
Mr. Amit Mishra Sir
Assistant Professor
Mechanical Department

2. CONTENTS
.Introduction
.definition
.Principle
.Working
.Industrial applications
.Advantage
.Disadvantage

3. DEFINITION
An absorption refrigerator is a refrigerator that uses a
heat source (e.g., solar energy, a fossil-fueled flame, waste
heat from factories, or district heating systems) which
provides the energy needed to drive the cooling process.
Absorption refrigerators are often used for food storage
in recreational vehicles. The principle can also be used
to air-conditionbuildings using the waste heat from a gas
turbine or water heater. Using waste heat from a gas
turbine makes the turbine very efficient because it first
produces electricity, then hot water, and finally, air-
conditioning (called cogeneration/trigeneration).

4. INTRODUCTION
In the early years of the twentieth century, the vapor
absorption cycle using water-ammonia systems was
popular and widely used, but after the development of
the vapor compression cycle it lost much of its
importance because of its low coefficient OF
performance (about one fifth of that of the vapor
compression cycle). Nowadays, the vapor absorption
cycle is used only where waste heat is available or where
heat is derived from solar collectors.

5. WORKING
The cooling cycle starts with liquid ammonia entering the evaporator
at room temperature. The volume of the evaporator is greater than
the volume of the liquid, with the excess space occupied by a mixture
of gaseous ammonia and hydrogen. The presence of hydrogen lowers
the partial pressure of the ammonia gas, thus lowering the boiling
point of the liquid below the temperature of the refrigerator's
interior. Ammonia evaporates, taking a small amount of heat from the
liquid and lowering the liquid's temperature, until it reaches that
boiling point. It then continues to evaporate, without the liquid
descending below the boiling point, while the large enthalpy of
vaporization (heat) flows from the warmer refrigerator interior to the
cooler liquid ammonia and then to more ammonia gas.

6. PRINCIPLE
Both absorption and compressor refrigerators use
a refrigerant with a very low boiling point (less than
0 °F (−18 °C)). In both types, when this refrigerant
evaporates (boils), it takes some heat away with it,
providing the cooling effect. The main difference
between the two systems is the way the refrigerant
is changed from a gas back into a liquid so that the
cycle can repeat. An absorption refrigerator
changes the gas back into a liquid using a method
that needs only heat, and has no moving parts
other than the refrigerant itself.

7. The absorption cooling cycle can
be described in three phases:
• Evaporation: A liquid refrigerant evaporates
in a low partial pressure environment, thus
extracting heat from its surroundings (e.g. the
refrigerator's compartment). Because of the
low partial pressure, the temperature needed
for evaporation is also low.
• Absorption: The now gaseous refrigerant
is absorbed by another liquid (e.g. a salt
solution).

8. •Regeneration: The refrigerant-saturated liquid is
heated, causing the refrigerant to evaporate out.
The hot gaseous refrigerant passes through a
heat exchanger, transferring its heat outside the
system (such as to surrounding ambient-
temperature air), and condenses. The condensed
(liquid) refrigerant supplies the evaporation
phase.

9. INDUSTRIAL APPLICATIONS
• A simple absorption refrigeration system common in
large commercial plants uses a solution of lithium
bromide and Lithiumchloride salt and water. Water
under low pressure is evaporated from the coils that
are being chilled. The water is absorbed by a lithium
bromide/water solution. The system drives the water
off the lithium bromide solution with heat.

10. Water spray absorption system:-
Another variant, depicted to the right, uses air, water, and a salt
water solution. The intake of warm, moist air is passed through a
sprayed solution of salt water. The spray lowers the humidity but
does not significantly change the temperature. The less humid,
warm air is then passed through an evaporative cooler, consisting
of a spray of fresh water, which cools and re-humidifies the air.
Humidity is removed from the cooled air with another spray of salt
solution, providing the outlet of cool, dry air.

11. Labeled photo of a domestic absorption refrigerator

12. 1. Hydrogen enters the pipe with liquid ammonia (or lithium
bromide solution)
2. Ammonia and hydrogen enter the inner compartment of the
refrigerator. An increase in volume causes a decrease in the
partial pressure of the liquid ammonia. The ammonia evaporates,
taking heat from the liquid ammonia and thus lowering its
temperature. Heat flows from the hotter interior of the refrigerator
to the colder liquid, promoting further evaporation.
3. Ammonia and hydrogen return from the inner compartment,
ammonia returns to absorber and dissolves in water. Hydrogen is
free to rise upwards.
4. Ammonia gas condensation (passive cooling).
5. Hot ammonia (gas).
6. Heat insulation and distillation of ammonia gas from water.
7. Heat source (electric).
8. Absorber vessel (water and ammonia solution).

13. ADVANTAGE AND DIS ADVANTAGE
The ammonia (gas) and hydrogen (gas) solution flows through a pipe
from the evaporator into the absorber. In the absorber, the solution
of gas flows into a solution of ammonia (liquid) and water (liquid).
The ammonia dissolves in the water and the hydrogen collects at the
top of the absorber, while the ammonia (liquid) and water (liquid)
solution remains at the bottom. The hydrogen is now separate, but
the ammonia is now mixed with water.
The next step separates the ammonia and water. The
ammonia/water solution flows to the generator, where heat is
applied to evaporate the ammonia, leaving most of the water, with
its higher boiling point, behind. Some water vapor and bubbles
remain mixed with the ammonia; this water is removed in the final
separation step, by passing it through the separator, an uphill series
of twisted pipes with minor obstacles to pop the bubbles, allowing
the water vapor to condense and drain back to the generator.