AIR CONDITIONING

Refrigeration cycle & Types of AC systems

 Air conditioner units must have the five basic
components to work:
 The compressor
 The condenser

 The expansion device

 The evaporator

 The copper refrigerant tube (a tube that connects these

air conditioner parts)
f
 The four major components split into two sections:
 indoor units,
➢ The compressor

➢ The condenser

 outdoor units,

➢ The expansion device

➢ The evaporator
 These four majors components are divided into two
difference pressure:
 high pressure and low pressure.
 The high pressure side is the condenser units (outdoor)
 The low pressure side is the air conditioning
evaporator (indoor).
 The divided point between high and low pressure cut
through the compressor and the expansion valve.
 Refrigeration cycle is a process that removes heat
from indoor evaporator to outdoor condenser units.
Air conditioner evaporator
 The air conditioning evaporator is a heat exchanger
that absorbs heat into the air conditioner system.
 The evaporator does not exactly absorb heat! It’s
the cooled refrigerant fed from the bottom of the
evaporator coils absorb the heat.
 The liquid refrigerant usually flows from the bottom
of the evaporator coils and boils as it moves to the
top of the evaporator coils.
 A (40°F) refrigerant flows through the evaporator, it
absorbs 75°F indoor heat, causing the liquid
refrigerant in the evaporator to boils.
 The air conditioner evaporator has three important
tasks:
 Its
absorb heat
 Boils all the refrigerant to vapor aka saturated vapor

 Superheat
Air conditioner compressors
 The air conditioning compressor is known as the heart of
the air conditioner units. It’s one of the divided points
between high and low side.
 The compressor has a refrigerant inlet line and
refrigerant outlet line.
 As the refrigerant flows across the compressor, it also
removes heat of compression, motor winding heat,
mechanical friction, and other heat absorbs in the
suction line.
 The air conditioner units compressor produce the
pressure different, it’s the air conditioner compressors
that cause the refrigerant to flow in a cycle
Air conditioner condenser
 The condenser units are located outdoor with the
compressor. It purposes is to reject both sensible and
latent heat of vapor absorb by the air conditioner units.
 The condenser receives high pressure and high
temperature superheats vapor from the compressor and
rejects that heat to the low temperature air. After
rejected all the vapor heat, it turns back to liquid
refrigerant.
 The condenser has three important steps:
 Its remove sensible heat or (de-superheat)
 Remove latent heat or (condense)
 Remove more sensible heat or (subcooled)
Air conditioner expansion valve
 All expansion device or metering device has similar
function (to some extent); it’s responsible for providing
the correct amount of refrigerant to the evaporator.
 This is done by creating a restriction within the
thermostatic expansion valve.
 The refrigeration cycle diagram above has a
thermostatic expansion valve. This expansion device has
 Remote Bulb
 Capillary Tube

 TXV Body
 TXV provides the correct amount of air conditioner
refrigerant to the evaporator by using a remote
sensing bulb as a regulator. The remote sensing
bulb and capillary tube has a refrigerant inside.
Air conditioning theory
 There are two laws that are significant to understand
the basic refrigeration cycle and air conditioning.
 Thermodynamics’ first law explains that energy cannot
be neither created nor destroyed, but can be changed
from one form to another.
 Thermodynamics second law can help us better
understand how the basic refrigeration cycle works.
Once of these laws state that heat always flows from a
material at a high temperature to a material at a low
temperature.
 residential air conditioners section, air conditioning (the
refrigeration cycle) is a process that simply removes
heat from an area that is not wanted and transfers that
heat to an area that makes no difference.
 The air conditioner itself does not create heat, it just
transfers heat.
 The refrigeration system removes heat from an area
that is low-pressure, low temperature (evaporator) into
an area of high-pressure, high temperature (condenser).
 For example, if cold refrigerant (40°F) flows through
the evaporator and the air surrounding evaporator is
75°F, the cold 40°F will absorb the heat from the 75°F
space. By absorbing the heat from the warm space, it
also cools the space. It then transfers that heats to
condenser (high side) through compressor.
 A hot refrigerant from the compressor flows to a cooler
location the condenser medium (air surround condenser)
for example, the refrigerant will give up the hot vapor
heat it absorbs from the indoor evaporator and
becomes cool again and turns back to liquid.
Refrigerant environmental issues
 Prior to 1994 most air conditioning systems utilized
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 the United
States and many other countries in 1994 due to
environmental concerns.
 The R-12 was replaced with R-134a refrigerant,
which has a lower ozone depletion potential.
 Cooling load Calculation
 Concepts and fundamentals of air conditioner sizing is based
on heat gain, and/or losses in a building.
 The air conditioner's efficiency, performance, durability, and
cost depend on matching its size to the above factors.
 Many designers use a simple square foot method for sizing the
air-conditioners. The most common rule of thumb is to use "1 ton
for every 500 square feet of floor area". Such a method is
useful in preliminary estimation of the equipment size.
 The main drawback of rules-of-thumb methods is the
presumption that the building design will not make any
difference. Thus the rules for a badly designed building are
typically the same as for a good design.
 The window and split air conditioners are usually
used for the small air conditioning capacities up to
5 tons.
 The packaged air conditioners are used for the
cooling capacities in between these two extremes.
The packaged air conditioners are available in the
fixed rated capacities of 3, 5, 7, 10 and 15 tons.
 The central air conditioning systems are used for
where the cooling loads extend beyond 20 tons.
 Electric motor
 An electric motor is used for the conversion of electrical
energy into mechanical energy.
 This conversion of electrical power to mechanical energy
takes place in the rotating part of the motor.
 A D.C. Motor is called as Conduction motor, but an A.C.
Motor is called as Induction Motor.
 Electric motors are used as a power source in the
operation of refrigeration compressors.
 AC (alternating current) will be used. Induction motor is
used in refrigeration application. Moving part in induction
motor-rotor and Static part in induction motor- stator.
 This mechanical energy
may be used for the
pumping of liquid from
one place to other by
using pumps or even to
blow air by blowers or
ceiling fans. The
conversion of electrical
power to mechanical
energy takes place in the
rotating part of the
motor.
 1.Window Air Conditioner
 Window air conditioner is the most commonly used air
conditioner for single rooms.
 In this air conditioner all the components, namely the
compressor, condenser, expansion valve or coil,
evaporator & cooling coil are enclosed in a single box.
 This unit is fitted in a slot made in the wall of the room, or
often a window sill.
 The whole assembly of the window air conditioner can be
divided into two compartments:
➢ the room side, which is also the cooling side
➢ the outdoor side from where the heat absorbed by the
room air is liberated to the atmosphere.
 In the front of the window air conditioner on the room
side there is beautifully decorated front panel on which
the supply and return air grills are fitted (the whole
front panel itself is commonly called as front grill).
 The louvers fitted in the supply air grills are adjustable
so as to supply the air in desired direction.
 There is also one opening in the grill that allows access
to the control panel or operating panel in front of the
window air conditioner.
Window Air Conditioner
 2. Split Air Conditioner
 The split air conditioner comprises of two parts: the
outdoor unit and the indoor unit.
 The outdoor unit, fitted outside the room, houses
components like the compressor, condenser and
expansion valve.
 The indoor unit comprises the evaporator or cooling
coil and the cooling fan. For this unit you don’t have
to make any slot in the wall of the room.
 The split air conditioner can be used to cool one or
two rooms.
 . The major reasons behind the popularity if split air
conditioner are their silent operation and elegant
looks.
 Another advantage of the split air conditioner is that
you don't have to make the hole in the wall of the air
conditioner and destroy the beauty of the room.
 These days the indoor units of the split air
conditioner are available in wide range of color and
designs.
 There are two main parts of the split air conditioner:
the indoor unit and the outdoor unit (see fig below).
 The indoor unit of the split AC is installed inside the
room that is to be air conditioned or cooled while,
 The outdoor unit is installed outside the room in
open space where the unit can be installed and
maintained easily.
 Apart from these two major parts there is copper
tubing connecting the indoor and the outdoor units.
 The most common type of the indoor unit is the wall
mounted type though other types like ceiling mounted and
floor mounted are also used.
 The installation of the split air conditioners is the most
important and crucial part.
 If it is done properly your air conditioner will give you
optimum performance, but if it is not done properly you
won't get the desired cooling effect and there may be
frequent maintenance problems of which the most
prominent can be the gas or refrigerant leakage.
 The installation of the split air conditioner should be done
by an expert air conditioning technician
Location of the Indoor and the
Outdoor Units
 Indoor Unit:
 located inside the room at the location from where the air can be
distributed evenly throughout the room.
 installed above the bed so that the maximum cooling effect can be
obtained. It should be located directly above the bed. If one has to
avoid the direct flow of chilled air on the body, one can always
change the direction of the louvers. The indoor unit can also be
installed on wall towards your feet though it can be installed on other
side walls also.
 The wall mounted indoor unit should be located at the height of about
8 to 10 feet from the floor so that that most of the chilled air is used
for cooling the room and not merely for cooling the hot roof.
 The indoor unit should be accessible easily so that one can
conveniently clean the filter every fortnight and the whole unit and also
that one can manually change the position of the louvers easily.
 Outdoor Unit:
 located in the open space preferably on the terrace so that the
air can flow freely over the compressor and the condenser. If the
terrace is not available it can be kept on the awning above the
wall or it can be hanged on the external wall supported by the
angles.
 should be such that it is easily accessible for carrying out the
maintenance works of the compressor, condenser, and other
devices. The installation and gas charging also should be
convenient.
 The surface on which the outdoor unit is to be installed should be
rigid enough to avoid its vibration. The vibration of the outdoor
unit will raise excessive noise and also lead to the breaking of the
copper tubing and leakage of the refrigerant.
 It is always advisable to keep the outdoor unit at the height above
the indoor unit. If the outdoor unit is kept at level below the indoor,
some of the compressor power is used in pumping the refrigerant
against the gravity, thus reducing the overall performance of the
compressor. Most of the outdoor units are quite silent so one does
not have to worry about their noise. The internal parts of the
outdoor unit are shielded against the rain and sun rays, so one can
rest assured about their safety in different climatic conditions.
 The refrigerant at very low temperature flows inside the tubing
between indoor and the outdoor unit, and there is always some loss
of refrigerant effect to the atmosphere from these tubing, hence the
distance between the indoor and the outdoor unit should be kept as
minimum as possible to reduce the loss of the cooling effect. The
maximum distance between the indoor and the outdoor units can be
about 15 meters.
 3.Packaged Air Conditioner
 These units are used commonly in places like restaurants,
telephone exchanges, homes, small halls, etc.
 As the name implies, in the packaged air conditioners all
the important components of the air conditioners are
enclosed in a single casing like window AC. Thus the
compressor, cooling coil, air handling unit and the air filter
are all housed in a single casing and assembled at the
factory location.
 Depending on the type of the cooling system used in
these systems, the packaged air conditioners are divided
into two types: ones with water cooled condenser and the
ones with air cooled condensers.
 Packaged Air Conditioners with
Water Cooled Condenser
 In these packaged air conditions the condenser is cooled
by the water. The condenser is of shell and tube type, with
refrigerant flowing along the tube side and the cooling
water flowing along the shell side. The water has to be
supplied continuously in these systems to maintain
functioning of the air conditioning system.
 The shell and tube type of condenser is compact in shape
and it is enclosed in a single casing along with the
compressor, expansion valve, and the air handling unit
including the cooling coil or the evaporator. This whole
packaged air conditioning unit externally looks like a box
with the control panel located externally.
 In the packaged units with the water cooled
condenser, the compressor is located at the bottom
along with the condenser (refer the figure below).
 Above these components the evaporator or the
cooling coil is located.
 The air handling unit comprising of the centrifugal
blower and the air filter is located above the cooling
coil.
 From the top of the package air conditioners the duct
comes out that extends to the various rooms that are
to be cooled.
Packaged Air Conditioners with
Air Cooled Condensers
 In this packaged air conditioners the condenser of the
refrigeration system is cooled by the atmospheric air.
 There is an outdoor unit that comprises of the important
components like the compressor, condenser and in some cases
the expansion valve (refer the figure below).
 The outdoor unit can be kept on the terrace or any other open
place where the free flow of the atmospheric air is available.
 The fan located inside this unit sucks the outside air and blows
it over the condenser coil cooling it in the process.
 The condenser coil is made up of several turns of the copper
tubing and it is finned externally.
 The cooling unit comprising of the expansion valve,
evaporator, the air handling blower and the filter are
located on the floor or hanged to the ceiling.
 The ducts coming from the cooling unit are connected to
the various rooms that are to be cooled.
 The packaged ACs with the air cooled condensers are
used more commonly than the ones with water cooled
condensers since air is freely available it is difficult
maintain continuous flow of the water.
 Compressors and Control System in
the Packaged Air Conditioners

 The packaged air conditioners are used for the low to

medium tonnage of air conditioning load ranging from 5
to 20 tons also higher.
 For smaller loads up to 5 tons single compressor is used.
 For the higher load of more than 5 tons two compressor
are used in the package air conditioning system forming
two independent refrigeration systems.
 Though the two systems are independent they are housed
in the same supporting framework. The evaporator
systems of these two systems are entwined together.
 The water cooled condenser used with the two
compressor system can be single shell but
partitioned inside it for different passages for the
refrigerant from the two compressors.
 There can also be two different water cooled
condensers for two different systems.
 If the condenser is of air cooled type, there would
be two condensers either placed side-by-side or
entwined together just like the evaporator of the
system.
 4.Central Air Conditioning System
 If the whole building is to be air conditioned, HVAC
engineers find that putting individual units in each of
the rooms is very expensive initially as well in the
long run.
 The central air conditioning system is comprised of a
huge compressor that has the capacity to produce
hundreds of tons of air conditioning.
 Cooling big halls, malls, huge spaces, galleries etc is
usually only feasible with central conditioning units.
 In the central air conditioning systems there is a
plant room where large compressor, condenser,
thermostatic expansion valve and the evaporator
are kept in the large plant room.
 They perform all the functions as usual similar to a
typical refrigeration system. However, all these
parts are larger in size and have higher capacities.
 The compressor is of open reciprocating type with
multiple cylinders and is cooled by the water
 The chilled is passed via the ducts to all the rooms,
halls and other spaces that are to be air conditioned.
 Thus in all the rooms there is only the duct passing the
chilled air and there are no individual cooling coils,
and other parts of the refrigeration system in the
rooms.
 What is we get in each room is the completely silent
and highly effective air conditions system in the room.
 The amount of chilled air that is needed in the room
can be controlled by the openings depending on the
total heat load inside the room.
 Two types of central air conditioning
plants or systems
 Direct expansion or DX central air conditioning plant: In
this system the huge compressor, and the condenser are
housed in the plant room, while the expansion valve and
the evaporator or the cooling coil and the air handling unit
are housed in separate room.
 The cooling coil is fixed in the air handling unit, which also
has large blower housed in it. The blower sucks the hot
return air from the room via ducts and blows it over the
cooling coil.
 The cooled air is then supplied through various ducts and
into the spaces which are to be cooled. This type of system
is useful for small buildings.
 In the DX system the air used for cooling the room or
space is directly passed over the cooling coil of the
refrigeration plant.
 Since the air is cooled directly by the refrigerant the
cooling efficiency of the DX plants is higher.
 However, it is not always feasible to carry the refrigerant
piping to the large distances hence, direct expansion or
the DX type of central air conditioning system is usually
used for cooling the small buildings or the rooms on the
single floor.
 Components in DX Units
 1) The Plant Room:
 The plant room comprises of the important parts of the
refrigeration system, the compressor and the condenser.
 The condenser is of shell and tube type and is cooled by
the water.
 The refrigerant flows along the tube side of the condenser
and water along the shell side, which enables faster
cooling of the refrigerant.
 The water used for cooling the compressor and the
condenser is cooled in the cooling tower kept at the top of
the plant room, though it can be kept at other convenient
location also.
 2) The Air Handling Unit Room:
 The refrigerant leaving the condenser in the plant room enters the
thermostatic expansion valve and then the air handling unit, which
is kept in the separate room.
 The air handling unit is a large box type of unit that comprises of
the evaporator or the cooling coil, air filter and the large blower.
 After leaving the thermostatic expansion valve the refrigerant
enters the cooling coil where it cools the air that enters the room
to be air conditioned.
 There are two types of ducts connected to the air handling unit:
for absorbing the hot return air from the rooms and for sending
the chilled air to the rooms to be air conditioned.
Chilled Water Central Air Conditioning Systems

 The chilled water types of central air conditioning

plants are installed in the place where whole large
buildings, shopping mall, airport, hotel, etc, comprising
of several floors are to be air conditioned.
 In case of the chilled water system the refrigeration
system is used to first chill the water, which is then used
to chill the air used for cooling the rooms or spaces.
 In chilled water plants, the ordinary water or brine
solution is chilled to very low temperatures of about 6
to 8 degree Celsius by the refrigeration plant.
 This chilled water is pumped to various floors of the
building and its different parts. In each of these
parts the air handling units are installed, which
comprise of the cooling coil, blower and the ducts.
 The chilled water flows through the cooling coil. The
blower absorbs return air from the air conditioned
rooms that are to be cooled via the ducts.
 This air passes over the cooling coil and gets cooled
and is then passed to the air conditioned space.
 The plant room comprises of all the important components
of the chilled water air conditioning plant. These include
the compressor, condenser, thermostatic expansion valve
and the evaporator or the chiller
 In the central air conditioning plant room all the
components, the compressor, condenser, thermostatic
expansion valve, and the chiller are assembled in the
structural steel framework making a complete compact
refrigeration plant, known as the chiller package.
 Piping required to connect these parts is also enclosed in
this unit making a highly compact central air conditioning
plant.