This 4-week industrial training report document provides an introduction, index, and acknowledgements section. It discusses refrigeration and air conditioning topics including methods of refrigeration, units of refrigeration, vapor compression refrigeration system components, and applications of refrigeration. The document is submitted to fulfill requirements for a diploma in mechanical engineering. It is comprised of 3 sentences or less.

1. 4 WEEKS
INDUSTRIAL TRAINING REPORT
ON
“REFRIGERATION & A/C”
(Submitted to Mechanical Engineering Department for the partial fulfillment of)
DIPLOMA IN MECHANICAL ENGINEERING
SUBMITTED BY………………. SUBMITTED TO:
HOD (ME)
APC, ABOHAR

2. ACKNOWLEDGEMENT
It is worth to do anything without mentioning the names of persons who made it possible.
I am very thankful to Our Principal Er. Tilak Raj and HOD Er Chhinder Pal who give us
opportunity to go for industrial training. I am also thankful to our training Incharge Er Sudhir
Bansal and Er Harvinder Singh for their value able guidance to accomplish our training on
time.
I thank all those who are directly or indirectly assisted us to complete this

3. INDEX
Introduction to Refrigeration
Methods of Refrigeration
Units of Refrigeration
VCR System Components
Air conditioning
Application of refrigeration

4. Introduction
Refrigeration is a process in which work is done to move heat from a low temperature to a high
temperature and typically also from one location to another. The work of heat transport is
traditionally driven by mechanical work, but can also be driven by
heat, magnetism, electricity, laser, or other means. Refrigeration has many applications,
including, but not limited to: household refrigerators, industrial freezers, cryogenics, and air
conditioning. Heat pumps may use the heat output of the refrigeration process, and also may be
designed to be reversible, but are otherwise similar to refrigeration units
Cycles Prof. U.S.P. Shet , Prof. T. Sundararajan and Prof. J.M . Mallikarjuna
Indian Institute of Technology Madras
6.2 Methods of Refrigeration:
a) Natural Method:
The natural method includes the utilization of ice or snow obtained naturally in cold
climate. Ice melts at 00C. So when it is placed in space or system warmer than 00C,
heat is absorbed by the ice and the space is cooled. The ice then melts into water by
absorbing its latent heat at the rate of 324 kJ/kg. But, now-a-days, refrigeration
requirements have become so high that the natural methods are inadequate and
therefore obsolete.
b) Mechanical or Artificial Refrigeration:
Atmosphere
(T1)
Refrigerated
System (T3)
T2
δQ1
Refrigerating System (R)
δW
δQ2
A mechanical refrigeration system works on the principle of reversed Carnot cycle as
shown in Fig.6.2. Work δw is delivered to the refrigerating system, causing it to remove
Refrigeration Cycles Prof. U.S.P. Shet , Prof. T. Sundararajan and Prof. J.M . Mallikarjuna
Indian Institute of Technology Madras
heat δQ2 from the body or system (at lower temperature T3) and to deliver it along with
work, δw, to another body at higher temperature, T1, so that,
δQ1 = δw + δQ2
There can be two methods by which the temperature T2 < T3 may be attained within the
refrigerating system.
i) By lowering the temperature of the working substance in the refrigerating

5. system to the level of T2. In this case, the heat will be absorbed due to
temperature difference and T3 will decrease as heat δQ2 flows out.
ii) By evaporating some fluid at an appropriate pressure. In this case, a constant
temperature T2 will be maintained and latent heat of fluid will be absorbed as
δQ2.
Depending upon the above method used, there are two types of mechanical
refrigerating systems :
i) Air systems: Uses air as a working fluid. Air does not undergo any change of
phase, but absorbs heat due to temperature difference.
ii) Chemical Agent Systems: The working fluid changing its phase while boiling
from liquid to vapor state, thereby it absorbs the latent heat.
Unit of Refrigeration:
Capacity of refrigeration unit is generally defined in ton of refrigeration. A ton of
refrigeration is defined as the quantity of heat to be removed in order to form one ton
(1000 kg) of ice at 00C in 24 hrs, from liquid water at 00C. This is equivalent to 3.5 kJ/s
(3.5 kW) or 210 kJ/min.
Methods of refrigeration can be classified as non-cyclic, cyclic, thermoelectric and magnetic.
Non-cyclic refrigeration
In non-cyclic refrigeration, cooling is accomplished by melting ice or by subliming dry
ice (frozen carbon dioxide). These methods are used for small-scale refrigeration such as in
laboratories and workshops, or in portable coolers.
Ice owes its effectiveness as a cooling agent to its melting point of 0 °C (32 °F) at sea level. To
melt, ice must absorb 333.55 kJ/kg (about 144 Btu/lb) of heat. Foodstuffs maintained near this
temperature have an increased storage life.
Solid carbon dioxide has no liquid phase at normal atmospheric pressure, and sublimes directly
from the solid to vapor phase at a temperature of -78.5 °C (-109.3 °F), and is effective for
maintaining products at low temperatures during sublimation. Systems such as this where the
refrigerant evaporates and is vented to the atmosphere are known as "total loss refrigeration".
Cyclic refrigeration
Heat pump and refrigeration cycle
This consists of a refrigeration cycle, where heat is removed from a low-temperature space or
source and rejected to a high-temperature sink with the help of external work, and its inverse,
the thermodynamic power cycle. In the power cycle, heat is supplied from a high-temperature
source to the engine, part of the heat being used to produce work and the rest being rejected to a
low-temperature sink. This satisfies the second law of thermodynamics.
A refrigeration cycle describes the changes that take place in the refrigerant as it alternately
absorbs and rejects heat as it circulates through a refrigerator. It is also applied
toHVACR work, when describing the "process" of refrigerant flow through an HVACR unit,
whether it is a packaged or split system.

6. Heat naturally flows from hot to cold. Work is applied to cool a living space or storage volume
by pumping heat from a lower temperature heat source into a higher temperature heat
sink. Insulation is used to reduce the work and energy needed to achieve and maintain a lower
temperature in the cooled space. The operating principle of the refrigeration cycle was
described mathematically by Sadi Carnot in 1824 as a heat engine.
The most common types of refrigeration systems use the reverse-Rankine vapor-compression
refrigeration cycle, although absorption heat pumps are used in a minority of applications.
Cyclic refrigeration can be classified as:
1. Vapor cycle, and
2. Gas cycle
Vapor cycle refrigeration can further be classified as:
1. Vapor-compression refrigeration
2. Vapor-absorption refrigeration
Vapor-compression cycle
(See Heat pump and refrigeration cycle and Vapor-compression refrigeration for more
details)
The vapor-compression cycle is used in most household refrigerators as well as in many
large commercial and industrial refrigeration systems. Figure 1 provides a schematic
diagram of the components of a typical vapor-compression refrigeration system.
Figure 1: Vapor compression refrigeration

7. The thermodynamics of the cycle can be analyzed on a diagram as shown in Figure 2. In
this cycle, a circulating refrigerant such as Freon enters the compressor as a vapor. From
point 1 to point 2, the vapor is compressed at constant entropy and exits the compressor as a
vapor at a higher temperature, but still below the vapor pressure at that temperature. From
point 2 to point 3 and on to point 4, the vapor travels through the condenser which cools the
vapor until it starts condensing, and then condenses the vapor into a liquid by removing
additional heat at constant pressure and temperature. Between points 4 and 5, the liquid
refrigerant goes through the expansion valve (also called a throttle valve) where its pressure
abruptly decreases, causing flash evaporation and auto-refrigeration of, typically, less than
half of the liquid.
Figure 2: Temperature–Entropy diagram
That results in a mixture of liquid and vapor at a lower temperature and pressure as shown
at point 5. The cold liquid-vapor mixture then travels through the evaporator coil or tubes
and is completely vaporized by cooling the warm air (from the space being refrigerated)
being blown by a fan across the evaporator coil or tubes. The resulting refrigerant vapor
returns to the compressor inlet at point 1 to complete the thermodynamic cycle.
The above discussion is based on the ideal vapor-compression refrigeration cycle, and does
not take into account real-world effects like frictional pressure drop in the system,
slight thermodynamic irreversibility during the compression of the refrigerant vapor,
or non-ideal gas behavior (if any).
More information about the design and performance of vapor-compression refrigeration
systems is available in the classicPerry's Chemical Engineers' Handbook.
Vapor absorption cycle

8. Main article: Absorption refrigerator
In the early years of the twentieth century, the vapor absorption cycle using water-ammonia
systems was popular and widely used. After the development of the vapor compression
cycle, the vapor absorption cycle lost much of its importance because of its low coefficient
of performance (about one fifth of that of the vapor compression cycle). Today, the vapor
absorption cycle is used mainly where fuel for heating is available but electricity is not,
such as in recreational vehicles that carry LP gas. It is also used in industrial environments
where plentiful waste heat overcomes its inefficiency.
The absorption cycle is similar to the compression cycle, except for the method of raising
the pressure of the refrigerant vapor. In the absorption system, the compressor is replaced
by an absorber which dissolves the refrigerant in a suitable liquid, a liquid pump which
raises the pressure and a generator which, on heat addition, drives off the refrigerant vapor
from the high-pressure liquid. Some work is needed by the liquid pump but, for a given
quantity of refrigerant, it is much smaller than needed by the compressor in the vapor
compression cycle. In an absorption refrigerator, a suitable combination of refrigerant and
absorbent is used. The most common combinations are ammonia (refrigerant) with water
(absorbent), and water (refrigerant) with lithium bromide (absorbent).
Gas cycle
When the working fluid is a gas that is compressed and expanded but doesn't change phase,
the refrigeration cycle is called a gas cycle. Air is most often this working fluid. As there is
no condensation and evaporation intended in a gas cycle, components corresponding to the
condenser and evaporator in a vapor compression cycle are the hot and cold gas-to-gas heat
exchangers in gas cycles.
The gas cycle is less efficient than the vapor compression cycle because the gas cycle works
on the reverse Brayton cycle instead of the reverse Rankine cycle. As such the working
fluid does not receive and reject heat at constant temperature. In the gas cycle, the
refrigeration effect is equal to the product of the specific heat of the gas and the rise in
temperature of the gas in the low temperature side. Therefore, for the same cooling load, a
gas refrigeration cycle needs a large mass flow rate and is bulky.
Because of their lower efficiency and larger bulk, air cycle coolers are not often used
nowadays in terrestrial cooling devices. However, the air cycle machine is very common
on gas turbine-powered jet aircraft as cooling and ventilation units, because compressed air
is readily available from the engines' compressor sections. Such units also serve the purpose
of pressurizing the aircraft.
Thermoelectric refrigeration
Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of
two different types of materials. This effect is commonly used in camping and portable
coolers and for cooling electronic components and small instruments.
Magnetic refrigeration
Main article: Magnetic refrigeration

9. Magnetic refrigeration, or adiabatic demagnetization, is a cooling technology based on the
magnetocaloric effect, an intrinsic property of magnetic solids. The refrigerant is often
aparamagnetic salt, such as cerium magnesium nitrate. The active magnetic dipoles in this
case are those of the electron shells of the paramagnetic atoms.
A strong magnetic field is applied to the refrigerant, forcing its various magnetic dipoles to
align and putting these degrees of freedom of the refrigerant into a state of loweredentropy.
A heat sink then absorbs the heat released by the refrigerant due to its loss of entropy.
Thermal contact with the heat sink is then broken so that the system is insulated, and the
magnetic field is switched off. This increases the heat capacity of the refrigerant, thus
decreasing its temperature below the temperature of the heat sink.
Because few materials exhibit the needed properties at room temperature, applications have
so far been limited to cryogenics and research.
Other methods
Other methods of refrigeration include the air cycle machine used in aircraft; the vortex
tube used for spot cooling, when compressed air is available; and thermoacoustic
refrigeration using sound waves in a pressurized gas to drive heat transfer and heat
exchange; steam jet cooling popular in the early 1930s for air conditioning large buildings;
thermoelastic cooling using a smart metal alloy stretching and relaxing. Many Stirling
cycle heat engines can be run backwards to act as a refrigerator, and therefore these engines
have a niche use in cryogenics. In addition there are other types of cryo coolers such as
Gifford-McMahon coolers, Joule-Thomson coolers, pulse-tube refrigerators and, for
temperatures between 2 mK and 500 mK, dilution refrigerators.
VCR System
There are six main components in a refrigeration system
 The Compressor
 The Condenser
 The Metering Device or expansion valve
 The Evaporator
 Piping material
 Refrigerant
Compressor
It is heart of the refrigeration system as it circulates the refrigerant in the system like the heart
of a human being circulating the blood in the body.
• Two different pressures exist in the refrigeration cycle. The evaporator or low
pressure, and the condenser, or high pressure. These pressure areas are divided by the
other two components. On one end, is the metering device which controls
the refrigerant flow, and on the other end, is the compressor.

10. The compressor is the heart of the system. The compressor does just what its name is.
It compresses the low pressure refrigerant vapor from the evaporator and compresses it
into a high pressure vapor.
• The inlet to the compressor is called the “Suction Line”. It brings the low
pressure vapor into the compressor.
• After the compressor compresses the refrigerant into a high pressure Vapor, and the
outlet of the compressor is called the “Discharge Line”.
There are three types of compressors namely reciprocating, rotary and centrifugal. The type of
compressor depends on the pressure difference between the high pressure side (condenser)
and low pressure side (evaporator) of the refrigeration system. This further depends on
the refrigerant selected for the application under consideration.
Condenser
• The “Discharge Line” leaves the compressor and runs to the inlet of the condenser.
• Because the refrigerant was compressed, it is a hot high pressure vapor.
• The hot vapor enters the condenser and starts to flow through the tubes.
• Cool air is blown across the outside of the finned tubes of the condenser (usually air by
a fan or water with a pump).
• Since the air is cooler than the refrigerant, heat jumps from the tubing to the cooler air
(energy goes from hot to cold – “latent heat”).
• As the heat is removed from the refrigerant, it reaches its “saturated temperature” and
starts to change state, into a high pressure liquid.
• The high pressure liquid leaves the condenser through the “liquid line” and travels to the
“metering device” through a filter dryer to remove any dirt or foreign particles.
The condenser can be free air cooled (domestic refrigerator), forced air cooled (window air
conditioner), water cooled (Central air conditioning plant in a library, cinema house and
evaporative cooled (ice plant unit or a cold storage unit).

11. Expansion Device
• Metering devices regulate how much liquid refrigerant enters the evaporator as per heat
load on evaporator.
• Common used metering devices are, small thin copper tubes referred to as “capillary
tubes”, thermally controller diaphragm valves” (thermostatic expansion valves, called
“TXV’s. This valve has the capability of controlling the refrigerant flow. If the load on
the evaporator changes, the valve can respond to the change and increase or decrease the
flow accordingly. The TXV has a sensing bulb attached to the outlet of the evaporator.
This bulb senses the suction line temperature and sends a signal to the TXV allowing it
to adjust the flow rate. This is important because, if not all, the refrigerant in the
evaporator changes state into a gas, there could be liquid refrigerant content returning to
the compressor. This can be fatal to the compressor. Liquid cannot be compressed and
when a compressor tries to compress a liquid, mechanical failing can happen. The
compressor can suffer mechanical damage in the valves and bearings. This is called”
liquid slugging”. Normally TXV's are set to maintain 10 degrees of superheat. That
means that the gas returning to the compressor is at least 10 degrees away from the risk
of having any liquid. The metering device tries to maintain a preset degree of superheat
at the outlet openings of the evaporator. As the metering devices regulates the amount
of refrigerant going into the evaporator, the device lets small amounts of refrigerant out
into the line and looses the high pressure to low pressure.
• Now we have a low pressure, cooler liquid refrigerant entering the evaporative coil.
These are of five type namely capillary tube (domestic fridge), Automatic expansion
valve (ice plant unit), Thermostatic expansion valve (Library refrigeration plant, theatre air
conditioning unit and many more), Low side float valve (industrial cooling units) and high
pressure float valve (industrial cooling units). These causes the required pressure drop
between the high and low pressure sides and also control the flow of refrigerant as per
cooling requirements.

12. Evaporator
The evaporator is where the heat is removed from your house, business or products to
be cooled.
• Low pressure liquid leaves the metering device and enters the evaporator.
• Usually, a fan will move warm air from the conditioned space across the evaporator
finned coils.
• The cooler refrigerant in the evaporator tubes, absorb the warm room air. The change of
temperature causes the refrigerant to “flash” or “boil”, and changes from a low
pressure liquid to a low pressure cold vapor.
• The low pressure vapor is pulled into the compressor and the cycle starts over.
• Evaporators are two types i.e. flooded evaporators necessitating the use of accumulators
to permit only vapors to the compressor and dry expansion type evaporators. Flooded
types are used in industrial units whereas dry expansion types are used in domestic and
commercial refrigeration units.
Piping Materials
Pipe material should have high thermal conductivity, low cost, easy working and inertness with
the refrigerant. Till date most commonly used pipe material is soft copper with all refrigerants
except ammonia. The pipe material used with ammonia is mild steel as ammonia is highly
corrosive to copper.
Refrigerant
It is working substance in a refrigeration unit like blood in the human body. Its selection
depends on many considerations like temperature to be produced, latent heat, ozone depletion
potential, global warming potential, toxicity, inflammability, inertness, corrosion, erosion,
action with water and lubricating oil, cost, availability, leak detection and power requirements
for a certain amount of cooling needed. Various commonly used refrigerants are halogenated
saturated hydrocarbons like R-134, R-22 and inorganic compounds like ammonia and air. Most
common previously used refrigerants like R-12 and R-11 has been banned because of their high
ozone depletion and global warming potentials. Mixed refrigerants and zoetrope’s are also in
use. Refrigerants can be primary, secondary and tertiary type depending where and how these
being used are. The same substance, for example, air can be primary in aircraft refrigeration;
can be secondary as in a window air conditioner and tertiary in a central air conditioning plant.

13. ICE PLANT
COMPRESSOR
CONDENSOR

14. Air conditioning
Air conditioning is the process of altering the properties of air (primarily temperature and
humidity) to more favourable conditions. More generally, air conditioning can refer to any form
of technological cooling, heating, ventilation, or disinfection that modifies the condition of
air.[1]
An air conditioner (often referred to as AC) is a major or home appliance, system, or
mechanism designed to change the air temperature and humidity within an area (used for
cooling and sometimes heating depending on the air properties at a given time). The cooling is
typically done using a simple refrigeration cycle, but sometimes evaporation is used, commonly
for comfort cooling in buildings and motor vehicles. In construction, a complete system of
heating, ventilation and air conditioning is referred to as "HVAC".
The basic concept behind air conditioning is known to have been applied in ancient Egypt
where reeds hung in windows had water trickling down. The evaporation of water cooled the
air blowing through the window, though this process also made the air more humid. In Ancient
Rome, water from aqueducts was circulated through the walls of certain houses to cool them
down. Other techniques in medieval Persia involved the use of cisterns and wind towers to cool
buildings during the hot season. Modern air conditioning emerged from advances in chemistry
during the 19th century, and the first large-scale electrical air conditioning was invented and
used in 1911 by Willis Haviland Carrier. The introduction of residential air conditioning in the
1920s helped start the great migration to the Sunbelt.
Pre-industrial cooling
The 2nd-century Chinese inventor Ding Huan (fl 180) of the Han Dynasty invented a rotary fan
for air conditioning, with seven wheels 3 m (9.8 ft) in diameter and manually powered.[2] In
747, Emperor Xuanzong (r. 712–762) of the Tang Dynasty (618–907) had the Cool Hall (Liang
Tian) built in the imperial palace, which the Tang Yulin describes as having water-powered fan
wheels for air conditioning as well as rising jet streams of water from fountains.[3] During the
subsequent Song Dynasty (960–1279), written sources mentioned the air-conditioning rotary
fan as even more widely used.[4]
In the 17th century, Cornelis Drebbel demonstrated "turning Summer into Winter" for James I
of England by adding salt to water.[5]
In 1758, Benjamin Franklin and John Hadley, a chemistry professor at Cambridge University,
conducted an experiment to explore the principle of evaporation as a means to rapidly cool an
object. Franklin and Hadley confirmed that evaporation of highly volatile liquids such as
alcohol and ether could be used to drive down the temperature of an object past the freezing
point of water. They conducted their experiment with the bulb of a mercury thermometer as
their object and with a bellows used to "quicken" the evaporation; they lowered the temperature
of the thermometer bulb down to −14 °C (7 °F) while the ambient temperature was 18 °C

15. (64 °F). Franklin noted that, soon after they passed the freezing point of water 0 °C (32 °F), a
thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about
a quarter-inch thick when they stopped the experiment upon reaching −14 °C (7 °F). Franklin
concluded, "From this experiment one may see the possibility of freezing a man to death on a
warm summer's day"...[6]
Mechanical cooling
Three-quarters scale model of Gorrie's ice machine. John Gorrie State Museum, Florida
In 1820, British scientist and inventor Michael Faraday discovered that compressing and
liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate. In
1842, Florida physician John Gorrie used compressor technology to create ice, which he used
to cool air for his patients in his hospital in Apalachicola, Florida.[7] He hoped eventually to use
his ice-making machine to regulate the temperature of buildings. He even envisioned
centralized air conditioning that could cool entire cities.[8] Though his prototype leaked and
performed irregularly, Gorrie was granted a patent in 1851 for his ice-making machine. His
hopes for its success vanished soon afterwards when his chief financial backer died; Gorrie did
not get the money he needed to develop the machine. According to his biographer, Vivian M.
Sherlock, he blamed the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor had
launched a smear campaign against his invention. Dr. Gorrie died impoverished in 1855, and
the idea of air conditioning faded away for 50 years.
James Harrison's first mechanical ice-making machine began operation in 1851 on the banks of
the Barwon River at Rocky Point in Geelong (Australia). His first commercial ice-making
machine followed in 1854, and his patent for an ether vapor-compression refrigeration system
was granted in 1855. This novel system used a compressor to force the refrigeration gas to pass

16. through a condenser, where it cooled down and liquefied. The liquefied gas then circulated
through the refrigeration coils and vaporised again, cooling down the surrounding system. The
machine employed a 5 m (16 ft.) flywheel and produced 3,000 kilograms (6,600 lb) of ice per
day.
Though Harrison had commercial success establishing a second ice company back in Sydney in
1860, he later entered the debate of how to compete against the American advantage of
unrefrigerated beef sales to the United Kingdom. He wrote Fresh Meat frozen and packed as if
for a voyage, so that the refrigerating process may be continued for any required period, and in
1873 prepared the sailing ship Norfolk for an experimental beef shipment to the United
Kingdom. His choice of a cold room system instead of installing a refrigeration system upon
the ship itself proved disastrous when the ice was consumed faster than expected.
Electromechanical cooling
Willis Carrier
In 1902, the first modern electrical air conditioning unit was invented by Willis Haviland
Carrier in Buffalo, New York. After graduating from Cornell University, Carrier, a native of
Angola, New York, found a job at the Buffalo Forge Company. While there, Carrier began
experimenting with air conditioning as a way to solve an application problem for the Sackett-
Wilhelms Lithographing and Publishing Company in Brooklyn, New York, and the first "air
conditioner", designed and built in Buffalo by Carrier, began working on 17 July 1902.
Designed to improve manufacturing process control in a printing plant, Carrier's invention
controlled not only temperature but also humidity. Carrier used his knowledge of the heating of
objects with steam and reversed the process. Instead of sending air through hot coils, he sent it
through cold coils (ones filled with cold water). The air blowing over the cold coils cooled the
air, and one could thereby control the amount of moisture the colder air could hold. In turn, the

17. humidity in the room could be controlled. The low heat and humidity helped maintain
consistent paper dimensions and ink alignment. Later, Carrier's technology was applied to
increase productivity in the workplace, and The Carrier Air Conditioning Company of America
was formed to meet rising demand. Over time, air conditioning came to be used to improve
comfort in homes and automobiles as well. Residential sales expanded dramatically in the
1950s.
In 1906, Stuart W. Cramer of Charlotte, North Carolina was exploring ways to add moisture to
the air in his textile mill. Cramer coined the term "air conditioning", using it in a patent claim
he filed that year as an analogue to "water conditioning", then a well-known process for making
textiles easier to process. He combined moisture with ventilation to "condition" and change the
air in the factories, controlling the humidity so necessary in textile plants. Willis Carrier
adopted the term and incorporated it into the name of his company. The evaporation of water in
air, to provide a cooling effect, is now known as evaporative cooling.
Evaporative cooling was the first real air-conditioning and shortly thereafter the first private
home to have air conditioning (The Dubose House) was built in Chapel Hill, North Carolina.
Realizing that air conditioning would one day be a standard feature of private homes,
particularly in the South, DuBose designed an ingenious network of ductwork and vents, all
painstakingly disguised behind intricate and attractive Georgian-style open moldings.
Meadowmont is believed to be one of the first private homes in the United States equipped for
central air conditioning.[9]
Refrigerant development
The first air conditioners and refrigerators employed toxic or flammable gases, such as
ammonia, methyl chloride, or propane, that could result in fatal accidents when they leaked.
Thomas Midgley, Jr created the first non-flammable, non-toxic chlorofluorocarbon gas, Freon,
in 1928.
"Freon" is a trademark name owned by DuPont for any Chlorofluorocarbon (CFC),
Hydrochlorofluorocarbon (HCFC), or Hydrofluorocarbon (HFC) refrigerant, the name of each
including a number indicating molecular composition (R-11, R-12, R-22, R-134A). The blend
most used in direct-expansion home and building comfort cooling is an HCFC known as R-22.
It was to be phased out for use in new equipment by 2010, and is to be completely discontinued
by 2020.
R-12 was the most common blend used in automobiles in the US until 1994, when most designs
changed to R-134A. R-11 and R-12 are no longer manufactured in the US for this type of
application, the only source for air-conditioning repair purposes being the cleaned and purified
gas recovered from other air-conditioner systems. Several non-ozone-depleting refrigerants
have been developed as alternatives, including R-410A, invented by Honeywell (formerly
AlliedSignal) in Buffalo, and sold under the Genetron (R) AZ-20 name. It was first
commercially used by Carrier under the brand name Puron.

18. Innovation in air-conditioning technologies continues, with much recent emphasis placed on
energy efficiency and on improving indoor air quality. Reducing climate-change impact is an
important area of innovation because, in addition to greenhouse-gas emissions associated with
energy use, CFCs, HCFCs, and HFCs are, themselves, potent greenhouse gases when leaked to
the atmosphere. For example, R-22 (also known as HCFC-22) has a global warming potential
about 1,800 times higher than CO2.[10] As an alternative to conventional refrigerants, natural
alternatives, such as carbon dioxide (CO2. R-744), have been proposed.[11]
Humidity control
Air conditioning units outside a classroom building at the University of North Carolina in Chapel Hill,
North Carolina
See also: Dehumidifier
Refrigeration air-conditioning equipment usually reduces the absolute humidity of the air
processed by the system. The relatively cold (below the dewpoint) evaporator coil condenses
water vapor from the processed air (much like an ice-cold drink will condense water on the
outside of a glass), sending the water to a drain and removing water vapor from the cooled
space and lowering the relative humidity in the room. Since humans perspire to provide natural
cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the
comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative
humidity in the occupied space. In food-retailing establishments, large open chiller cabinets act
as highly effective air dehumidifying units.
A specific type of air conditioner that is used only for dehumidifying is called a dehumidifier.
A dehumidifier is different from a regular air conditioner in that both the evaporator and
condenser coils are placed in the same air path, and the entire unit is placed in the environment
that is intended to be conditioned (in this case dehumidified), rather than requiring the

19. condenser coil to be outdoors. Having the condenser coil in the same air path as the evaporator
coil produces warm, dehumidified air. The evaporator (cold) coil is placed first in the air path,
dehumidifying the air exactly as a regular air conditioner does. The air next passes over the
condenser coil, re-warming the now dehumidified air. Having the condenser coil in the main air
path rather than in a separate, outdoor air path (as with a regular air conditioner) results in two
consequences: the output air is warm rather than cold, and the unit is able to be placed
anywhere in the environment to be conditioned, without a need to have the condenser outdoors.
Unlike a regular air conditioner, a dehumidifier will actually heat a room just as an electric
heater that draws the same amount of power (watts) as the dehumidifier would. A regular air
conditioner transfers energy out of the room by means of the condenser coil, which is outside
the room (outdoors). That is, the room can be considered a thermodynamic system from which
energy is transferred to the external environment. Conversely, with a dehumidifier, no energy is
transferred out of the thermodynamic system (room) because the air conditioning unit
(dehumidifier) is entirely inside the room. Therefore all of the power consumed by the
dehumidifier is energy that is input into the thermodynamic system (the room) and remains in
the room (as heat). In addition, if the condensed water has been removed from the room, the
amount of heat needed to boil that water has been added to the room. This is the inverse of
adding water to the room with an evaporative cooler.
Dehumidifiers are commonly used in cold, damp climates to prevent mold growth indoors,
especially in basements. They are also used to protect sensitive equipment from the adverse
effects of excessive humidity in tropical countries.
The engineering of physical and thermodynamic properties of gas–vapor mixtures is called
psychrometrics.
Energy
In a thermodynamically closed system, any power dissipated into the system that is being
maintained at a set temperature (which is a standard mode of operation for modern air
conditioners) requires that the rate of energy removal by the air conditioner increase. This
increase has the effect that, for each unit of energy input into the system (say to power a light
bulb in the closed system), the air conditioner removes that energy.[12] In order to do so, the air
conditioner must increase its power consumption by the inverse of its "efficiency" (coefficient
of performance) times the amount of power dissipated into the system. As an example, assume
that inside the closed system a 100 W heating element is activated, and the air conditioner has
an coefficient of performance of 200%. The air conditioner's power consumption will increase
by 50 W to compensate for this, thus making the 100 W heating element cost a total of 150 W
of power.
It is typical for air conditioners to operate at "efficiencies" of significantly greater than
100%.[13] However, it may be noted that the input electrical energy is of higher thermodynamic
quality (lower entropy) than the output thermal energy (heat energy).

20. Air conditioner equipment power in the U.S. is often described in terms of "tons of
refrigeration". A ton of refrigeration is approximately equal to the cooling power of one short
ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as
12,000 BTU per hour, or 3517 watts.[14] Residential central air systems are usually from 1 to 5
tons (3 to 20 kilowatts (kW)) in capacity.
In an automobile, the A/C system will use around 4 horsepower (3 kW) of the engine's power
Seasonal energy efficiency ratio
Main article: Seasonal energy efficiency ratio
For residential homes, some countries set minimum requirements for energy efficiency. In the
United States, the efficiency of air conditioners is often (but not always) rated by the seasonal
energy efficiency ratio (SEER). The higher the SEER rating, the more energy efficient is the air
conditioner. The SEER rating is the BTU of cooling output during its normal annual usage
divided by the total electric energy input in watt hours (W·h) during the same period.[16]
SEER = BTU ÷ (W·h)
this can also be rewritten as:
SEER = (BTU / h) ÷ W, where "W" is the average electrical power in Watts, and (BTU/h) is
the rated cooling power.
For example, a 5000 BTU/h air-conditioning unit, with a SEER of 10, would consume 5000/10
= 500 Watts of power on average.
The electrical energy consumed per year can be calculated as the average power multiplied by
the annual operating time:
500 W × 1000 h = 500,000 W·h = 500 kWh
Assuming 1000 hours of operation during a typical cooling season (i.e., 8 hours per day for 125
days per year).
Another method that yields the same result, is to calculate the total annual cooling output:
5000 BTU/h × 1000 h = 5,000,000 BTU
Then, for a SEER of 10, the annual electrical energy usage would be:
5,000,000 BTU ÷ 10 = 500,000 W·h = 500 kWh

21. SEER is related to the coefficient of performance (COP) commonly used in thermodynamics
and also to the Energy Efficiency Ratio (EER). The EER is the efficiency rating for the
equipment at a particular pair of external and internal temperatures, while SEER is calculated
over a whole range of external temperatures (i.e., the temperature distribution for the
geographical location of the SEER test). SEER is unusual in that it is composed of an Imperial
unit divided by an SI unit. The COP is a ratio with the same metric units of energy (joules) in
both the numerator and denominator. They cancel out, leaving a dimensionless quantity.
Formulas for the approximate conversion between SEER and EER or COP are available from
the Pacific Gas and Electric Company:[17]
(1) SEER = EER ÷ 0.9
(2) SEER = COP × 3.792
(3) EER = COP × 3.413
From equation (2) above, a SEER of 13 is equivalent to a COP of 3.43, which means that 3.43
units of heat energy are pumped per unit of work energy.
The United States now requires that residential systems manufactured in 2006 have a minimum
SEER rating of 13 (although window-box systems are exempt from this law, so their SEER is
still around 10).[18]

22. Construction
A typical home air conditioning unit
Refrigerants
Main article: Refrigerant

23. A modern R-134a hermetic refrigeration compressor
"Freon" is a trade name for a family of haloalkane refrigerants manufactured by DuPont and
other companies. These refrigerants were commonly used due to their superior stability and
safety properties. However, these chlorine-bearing refrigerants reach the upper atmosphere
when they escape.[19] Once the refrigerant reaches the stratosphere, UV radiation from the Sun
cleaves the chlorine-carbon bond, yielding a chlorine radical. These chlorine atoms catalyze the
breakdown of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's
surface from strong UV radiation. Each chlorine radical remains active as a catalyst unless it
binds with another chlorine radical, forming a stable molecule and breaking the chain reaction.
The use of CFC as a refrigerant was once common, being used in the refrigerants R-11 and R-
12. In most countries the manufacture and use of CFCs has been banned or severely restricted
due to concerns about ozone depletion.[20] In light of these environmental concerns, beginning
on November 14, 1994, the U.S. Environmental Protection Agency has restricted the sale,
possession and use of refrigerant to only licensed technicians, per Rules 608 and 609 of the
EPA rules and regulations;[21] failure to comply may result in criminal and civil sanctions.
Newer and more environmentally safe refrigerants such as HCFCs (R-22, used in most homes
today) and HFCs (R-134a, used in most cars) have replaced most CFC use. HCFCs, in turn, are
being phased out under the Montreal Protocol and replaced by hydrofluorocarbons (HFCs) such
as R-410A, which lack chlorine. Carbon dioxide (R-744) is being rapidly adopted as a
refrigerant in Europe and Japan. R-744 is an effective refrigerant with a global warming
potential of 1. It must use higher compression to produce an equivalent cooling effect.

24. Types
The external section of a typical single-room air conditioning unit. For ease of installation, these are
frequently placed in a window. This one was installed through a hole cut in the wall.
The internal section of the above unit. The front panel swings down to reveal the controls.
Window and through-wall
Room air conditioners come in two forms: unitary and packaged terminal PTAC systems.
Unitary systems, the common one room air conditioners, sit in a window or wall opening, with
interior controls. Interior air is cooled as a fan blows it over the evaporator. On the exterior the
air is heated as a second fan blows it over the condenser. In this process, heat is drawn from the
room and discharged to the environment. A large house or building may have several such
units, permitting each room be cooled separately.
PTAC systems are also known as wall split air conditioning systems or ductless systems.[22]
These PTAC systems which are frequently used in hotels have two separate units (terminal
packages), the evaporative unit on the interior and the condensing unit on the exterior, with
tubing passing through the wall and connecting them. This minimizes the interior system
footprint and allows each room to be adjusted independently. PTAC systems may be adapted to
provide heating in cold weather, either directly by using an electric strip, gas or other heater, or
by reversing the refrigerant flow to heat the interior and draw heat from the exterior air,
converting the air conditioner into a heat pump. While room air conditioning provides
maximum flexibility, when used to cool many rooms at a time it is generally more expensive
than central air conditioning.

25. The first practical through the wall air conditioning unit was invented by engineers at Chrysler
Motors and offered for sale starting in 1935.[23]
Window unit
Evaporative coolers
Main article: Evaporative cooler
In very dry climates, evaporative coolers, sometimes referred to as swamp coolers or desert
coolers, are popular for improving coolness during hot weather.
An evaporative cooler is a device that draws outside air through a wet pad, such as a large
sponge soaked with water. The sensible heat of the incoming air, as measured by a dry bulb
thermometer, is reduced. The total heat (sensible heat plus latent heat) of the entering air is
unchanged. Some of the sensible heat of the entering air is converted to latent heat by the
evaporation of water in the wet cooler pads. If the entering air is dry enough, the results can be
quite cooling; evaporative coolers tend to feel as if they are not working during times of high
humidity, when there is not much dry air with which the coolers can work to make the air as
cool as possible for dwelling occupants. Unlike air conditioners, evaporative coolers rely on the
outside air to be channeled through cooler pads that cool the air before it reaches the inside of a
house through its air duct system; this cooled outside air must be allowed to push the warmer
air within the house out through an exhaust opening such as an open door or window.[24]
These coolers cost less and are mechanically simple to understand and maintain.
An early type of cooler, using ice for a further effect, was patented by John Gorrie of
Apalachicola, Florida in 1842. He used the device to cool the patients in his malaria hospital.
Portable units
A portable air conditioner is one on wheels that can be easily transported inside a home or
office. They are currently available with capacities of about 5,000–60,000 BTU/h (1,800–

26. 18,000 W output) and with and without electric-resistance heaters. Portable air conditioners are
either evaporative or refrigerative.
Portable refrigerative air conditioners come in two forms, split and hose. These compressor-
based refrigerant systems are air-cooled, meaning they use air to exchange heat, in the same
way as a car or typical household air conditioner does. Such a system dehumidifies the air as it
cools it. It collects water condensed from the cooled air and produces hot air which must be
vented outside the cooled area; doing so transfers heat from the air in the cooled area to the
outside air.
A portable split system has an indoor unit on wheels connected to an outdoor unit via flexible
pipes, similar to a permanently fixed installed unit.
Hose systems, which can be monoblock or air-to-air, are vented to the outside via air ducts.
The monoblock type collects the water in a bucket or tray and stops when full. The air-to-air
type re-evaporates the water and discharges it through the ducted hose and can run
continuously.
A single-duct unit uses air from within the room to cool its condenser, and then vents it outside.
This air is replaced by hot air from outside or other rooms, thus reducing the unit's
effectiveness. Modern units might have a coefficient of performance (COP, sometimes called
"efficiency") of approximately 3 (i.e., 1 kW of electricity will produce 3 kW of cooling). A
dual-duct unit draws air to cool its condenser from outside instead of from inside the room, and
thus is more effective than most single-duct units.
Evaporative air coolers, sometimes called "swamp coolers", do not have a compressor or
condenser. Liquid water is evaporated on the cooling fins, releasing the vapour into the cooled
area. Evaporating water absorbs a significant amount of heat, the latent heat of vaporisation,
cooling the air: humans and other animals use the same mechanism to cool themselves by
sweating. They have the advantage of needing no hoses to vent heat outside the cooled area,
making them truly portable; and they are very cheap to install and use less energy than
refrigerative air conditioners. Disadvantages are that unless ambient humidity is low (as in a
dry climate) cooling is limited and the cooled air is very humid and can feel clammy. Also, they
use a lot of water, which is often at a premium in the dry climates where they work best.
A typical single hosed portable air conditioner can cool a room that is 475 sq ft (44.1 m2) or
smaller and has at most a cooling power of 15,000 BTUs/h (4.3 kW). However, single hosed
units cool a room less effectively than dual hosed as the air expelled from the room through the
single hose creates negative pressure inside the room. Because of this, air (potentially warm air)
from neighboring rooms is pulled into the room with the cooling unit to compensate.[25]

27. Heat pumps
Main article: Heat pump
"Heat pump" is a term for a type of air conditioner in which the refrigeration cycle can be
reversed, producing heating instead of cooling in the indoor environment. They are also
commonly referred to, and marketed as, a "reverse cycle air conditioner". Using an air
conditioner in this way to produce heat is significantly more energy efficient than electric
resistance heating. Some homeowners elect to have a heat pump system installed, which is
simply a central air conditioner with heat pump functionality (the refrigeration cycle can be
reversed in cold weather). When the heat pump is in heating mode, the indoor evaporator coil
switches roles and becomes the condenser coil, producing heat. The outdoor condenser unit
also switches roles to serve as the evaporator, and discharges cold air (colder than the ambient
outdoor air).
Heat pumps are more popular in milder winter climates where the temperature is frequently in
the range of 40–55°F (4–13°C), because heat pumps become inefficient in more extreme cold.
This is due to the problem of ice forming on the outdoor unit's heat exchanger coil, which
blocks air flow over the coil. To compensate for this, the heat pump system must temporarily
switch back into the regular air conditioning mode to switch the outdoor evaporator coil back to
being the condenser coil, so that it can heat up and de-ice. A heat pump system will therefore
have a form of electric resistance heating in the indoor air path that is activated only in this
mode in order to compensate for the temporary indoor air cooling, which would otherwise be
uncomfortable in the winter. The icing problem becomes much more severe with lower outdoor
temperatures, so heat pumps are commonly installed in tandem with a more conventional form
of heating, such as a natural gas or oil furnace, which is used instead of the heat pump during
harsher winter temperatures. In this case, the heat pump is used efficiently during the milder
temperatures, and the system is switched to the conventional heat source when the outdoor
temperature is lower.
Absorption heat pumps are actually a kind of air-source heat pump, but they do not depend on
electricity to power them. Instead, gas, solar power, or heated water is used as a main power
source. Additionally, refrigerant is not used at all in the process.[dubious – discuss] An absorption
pump absorbs ammonia into water.[further explanation needed] Next, the water and ammonia mixture is
depressurized to induce boiling, and the ammonia is boiled off, resulting in cooling.[26]
Some more expensive window air conditioning units have a true heat pump function. However,
a window unit that has a "heat" selection is not necessarily a heat pump because some units use
only electric resistance heat when heating is desired. A unit that has true heat pump
functionality will be indicated its specifications by the term "heat pump".

28. Health issues
Air-conditioning systems can promote the growth and spread of microorganisms, such as
Legionella pneumophila, the infectious agent responsible for Legionnaires' disease, or
thermophilic actinomycetes; however, this is only prevalent in poorly-maintained water cooling
towers. As long as the cooling tower is kept clean (usually by means of a chlorine treatment),
these health hazards can be avoided.
Conversely, air conditioning (including filtration, humidification, cooling and disinfection) can
be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and
other environments where an appropriate atmosphere is critical to patient safety and well-being.
Air conditioning can have a negative effect on skin, drying it out,[33] and can also cause
dehydration.[34] Air conditioning may have a positive effect on sufferers of allergies and
asthma.
Prior to 1994, most automotive air conditioning systems used Dichlorodifluoromethane (R-12)
as a refrigerant. It was usually sold under the brand name Freon-12 and is a chlorofluorocarbon
halomethane (CFC). The manufacture of R-12 was banned in many countries in 1994 because
of environmental concerns, in compliance with the Montreal Protocol. The R-12 was replaced
with R-134a refrigerant, which has a lower ozone depletion potential. Old R-12 systems can be
retrofitted to R-134a by a complete flush and filter/dryer replacement to remove the mineral oil,
which is not compatible with R-134a.

29. REFERENCES
www.wikipedia.com
Refrigeration and air conditioning by Domkudwar
Refrigeration by N Singh