This document provides an overview of solar cooling applications using absorption systems. It describes the basic components and processes of simple and practical vapour absorption systems using examples like ammonia-water. It discusses properties of ideal refrigerants, absorbents, and their combinations. Some advantages of absorption systems over compression systems are their lack of moving parts, ability to operate on thermal energy alone, suitability for large capacities, and controllability. Passive cooling techniques to reduce heat transfer and remove unwanted heat from buildings are also briefly covered.

1. COOLING APPLICATIONS
OF SOLAR SYSTEMS
Submitted to :
Mr. Narender Kaushik
Associate Professor,
Mechanical Dept.,
Presented By :
Vikram Dangi
758/ME/12
VAISH COLLEGE OF ENGG.,
ROHTAK

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
• Passive Cooling

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. LAYOUT OF VARS

7. COEFFICIENT OF PERFORMANCE OF
IDEAL ABSORPTION SYSTEM

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

9. 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 ]

10. 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.

11. 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

12. •For LiBr-water solution
•It uses water as refrigerant(boiling point 100ºC) and Lithium-
Bromide(boiling point 1265ºC) as its absorbent
•Is used in a number of air conditioning applications. This system is
useful for applications where the temperature required is more than
32ºF(0ºC).
•Water used as the refrigerant in the absorption refrigeration system
means the operating pressures in the condenser and the evaporator
must be very low
• The system can be achieved even without installing the expansion
valve in the system, since the drop in pressure occurs due to friction in
the refrigeration piping and in the spray nozzles.
•It has lesser components than ammonia-water absorption.
LiBr-WATER COMBINATION

13. AMMONIA-WATER COMBINATION
•Uses Ammonia(NH3, Boiling point -33.34ºC) as refrigerant and
Water(Boiling point100ºC) as absorber
•Most commercial and industrial refrigeration applications occur
at temperatures below 32ºF(0ºC) and many are 0ºF (-
17.78ºC). As a result, a fluid which is not subject to freezing at
these temperatures is required. So the lithium bromide-water
cycle is no longer able to achieve this conditions, because
water is used for the refrigerant.
•Have a disadvantage in acquiring extra parts compare to LiBr-
water system but does have an advantage in operating
pressure above atmospheric that avoid air leakage.

14. 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.

15. PASSIVE COOLING

16. PASSIVE COOLING
•Passive cooling refers to technologies or design features used to
cool buildings without power consumption, such as those technologies discussed in
the Passive house project.
The term "passive" implies that energy-consuming mechanical components like
pumps and fans are not used.
Passive cooling building design attempts to integrate principles of physics into
the building exterior envelope to:
Slow heat transfer into a building. This involves an understanding of the
mechanisms of heat transfer: heat conduction, convective heat transfer,
and thermal radiation (primarily from the sun).
Remove unwanted heat from a building. In mild climates with cool dry
nights this can be done with ventilating. In hot humid climates with
uncomfortable warm / humid nights, ventilation is counterproductive, and
some of solar air conditioning may be cost effective.

17. PURPOSE OF PASSIVE COOLING
• Provides indoor comfort
• Low maintenance
• Zero/ Low energy consumption
• Low running cost
• Promotes healthy environment
☺Saves the Earth

18. SOME PASSIVE COOLING
TECHNIQUES
Shading a building from solar radiation can be achieved in
many ways.
Buildings can be orientated to take advantage of winter sun
(longer in the East / West dimension), while shading walls
and windows from direct hot summer sun. This can be
achieved by designing location-specific wide eaves or
overhangs above the Equator-side vertical windows (South
side in the Northern hemisphere, North side in the Southern
hemisphere).
(1)SHADING

19. VENTILATION
The mechanical system or equipment used to circulate air or
to replace stale air with fresh air.
Ventilation in buildings has three main purposes:
1. To maintain a minimum air quality
2. To remove heat (or other pollutant)
3. To provide perceptible air movement to enhance thermal
comfort
(2)VENTILATION

20. THANK
YOU