Airconditioning ppt

AIRCONDITIONING
VENTILATION IN BUILDINGS
TYPES OF FANS
TYPES OF AIR CONDITIONERS
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• “I am certain that no air is so unwholesome as air in a
closed room that has been often breathed and not
changed.”
Benjamin Franklin
Mid 1700s

VENTILATIONOF BUILDINGS:
Human life- space for living & working.
• Living- biological & physical requirements.
• Air is reqd. for breathing.
• Composition of Air: Nitrogen- 78.084 %
Oxygen- 20.94 %
Argon- 00.934%
CO2 - 00.033%
•Purpose: to remove high concentrations of body odours, carbon dioxide, water
vapors, dust, fumes & smoke & excess heat.
• air replaced by fresh air & creates air movement inside the bldg. to get feeling of
freshness without draught.
• air velocity of 0.15 & 0.5 m per second is acceptable, higher concentrations for
manual work, to prevent monotony, variable air speed is preferable to a constant air
speed.
• minimum ventilation rate of 28m3 of fresh air per person is reqd for theatres, cinema
& dance halls.

SYSTEMSOFVENTILATION:
Natural- wind pressure, stack effect,
combination of both.
•Wind causes positive pressure to act on
windward side of the bldg. & negative pressure
to act on the leeward side.
• Fig shows wind pressure distribution diagram
for pitched & flat roofs.
• inlet openings shall be well distributed &
located on windward side near the bottom.
•Outlets well distributed located on leeward
side near the top, for cross ventilation.

•The higher the column or ‘stack’ of warm air the
greater will be the air movement inside the building.
• for max. advantage, vertical distance betw inlet &
outlet openings should be as great as possible.
• in presence of wind, air inside is warmer than air
outside, ventilation will take place by both wind &
stack effect.
STACK EFFECT IN BLDG.
• Natural ventilation cannot ensure specified air
change, nor it is possible to filter the air before it
enters the building.
• if air inside is at same temperature as air outside,
there is no wind, natural ventilation will be non-
existent.

AIR CONDITIONING BASED ON CLIMATE
The heat & other gains are given below:
 heat by conduction (structural)
 Heat by radiation (through windows)
 Heat by convection currents (Atmospheric)
 Heat gain by gadgets & devices
 Heat gain by persons working or occupying spaces
 any other reason for heat gain.

MECH.VENTILATION,AIRCONDITIONING & AIR COOLING
The heat & other gains are given below:
Rated capacity is expressed inTR=Ton
of refrigeration

MECHANICALVENTILATION
•System employs electrically driven fan or fans for necessary air movement
• provides positive ventilation at all times, irrespective of outside conditions.
• ensures specified air change & air under fan pressure can be forced through filters.
•There are three types of mechanical ventilation systems namely:
1. Natural inlet & mechanical extract (exhaust system)
Ducted exhaust system for assembly hall
•Most common type of system used for kitchens,
workshops, laboratories, garages, sanitary
apartments & assembly halls.
• fan creates negative pressure on its inlet side, this
causes the air inside to move towards the fan, the
room air is displaced by the fresh air from outside the
room.
•The air inlets can be placed behind radiators, so that
air is warmed before it enters the hall.

Common duct system for internal
bathrooms andWC cubicles
•Internal Bathrooms &W.Cs:
•Min extract rate of 20 m3/h from a W.C cubicle, or
bathroom without W.C & min extract rate of 40 m3/h
from a bathroom withW.C.
• ventilation to be separate than other vent. Plant.
• preferably connected to main vertical duct by a
shunt duct at least 1m long.
• fans capable of extracting total flow of air, plus an
allowance on fan static pressure to counteract wind
pressure.

2. Mechanical inlet & Natural extract
•Essential in this system that air is heated
before being forced into the building.
• used for boiler rooms, offices, factories etc.
• air may be heated in central plant & ducted
to various rooms or unit fan convector may be
used.

Downward & upward System
Upward air distribution System
2. Mechanical inlet & extract
•Best possible system of ventilation, most expensive,
used for many types of buildings including cinemas,
theatres, offices, lecture theatres, dance halls,
restaurants, dept. stores & sports centre.
• air is normally filtered & provision is made for
recirculation of heated air which reduces fuel costs,
air may be extracted thru electric light fittings, which
also increases the light efficiency about 14%.

Air conditioning:
Definition:
• a system giving automatic control, within predetermined limits of the
environmental conditions, by heating, cooling, humidification,
dehumidification, cleaning & movement of air in buildings.
• Basic job of preparing conditioned air & supply to built spaces, returning
back of same air delivered is done by AC systems.
• The systems of AC are basically same as far as making the conditioned air
but differ as regards place where it is prepared and methods of supply &
return.
• for Indian conditions mostly making cold air or cooling the air is the main
job.The range is from 35- 31 deg C to 20-24 deg C.

Types of fans:
•Three types of fans are normally used:
1. Propeller: two or more blades fixed at an angle to
the hub, develop low pressure of only 125 Pa (12.5
mm water gauge).
Can remove large volumes of air, installation cost is
lower,
2. Centrifugal: impeller revolves inside a casing
shaped like a scroll, can develop high pressure upto 760
Pa therefore used forcing air to long length ductwork,
inlet is at 90deg to outlet and this makes it difficult to
install, unless ductwork can also be turned thru the
same angle. Forward blade impeller-constant air
resistance, backward blade-variable air resistance &
paddle blade-for high lvl of suspended matter.
3. Axial flow fans: an impeller with blades of aerofoil
section, rotating inside a cylindrical casing, air flows in
parallel to propeller shaft, can be installed without fan
base. Efficiencies range between 60 & 75 %, develop
pressure up to @ 1500 Pa.

Fan laws with constant air temperature
1. Volume of air delivered varies as the fan speed.
2. pressure developed varies as square of fan speed.
3. power absorbed varies as cube of fan speed.

Air conditioning Systems:
Type of system depends upon the type of bldg. System may be divided
into three categories:
1. All air systems where conditioned air is treated in the central plant &
ducted to various rooms, requires large spaces & duct rooms.
2. Air & water where air is treated in central plant, heating & cooling is
done in the rooms by passing air over hot or cold water coils supplied from
a central boiler & refrigeration plant.Central plant is smaller & less
ductwork is required.
3. Self contained units in which complete air conditioning process is carried
out & sited inside various rooms against outside wall, so that fresh air can
be drawn into the units thru a short duct in the wall.

Air Cooled
&
Water Cooled Condensor
Used in areas where
free air supply is
limited or non existant

 use of air to cool the
compressor & condenser coil
used to return the refrigerant gas
to a liquid state.
 These split systems usually
have an inside evaporator
cooling coil installed to work
along with the blower & duct
system. The outside half of the
equipment contains the
compressor and condenser coil.
AIR COOLED AC SYSTEMS
Schematic diagram shows how refrigerant
moving through the system as a gas or
liquid moves heat from inside the building
(at the evaporator coil in an air handler) to
outside the building (at the condenser
unit's condensing coil).

WATER COOLED AC SYSTEMS
 use water as a chiller to remove
heat from the high temp gas in
the (usually but not always
outside) compressor/condenser
unit.
 uses refrigerant & coils to move
heat from indoors to outside. But
instead of moving heat from the
condensing coil into air blown
across the coil outdoors, we're
moving heat into water circulated
around a condensing coil.

TYPES OF AIR CONDITIONING
Central
Air Conditioning
System
Unit
Air Conditioning
System
AHU based
Compartmental
Air Conditioning
System
Unit
Air Conditioners
SplitAC Packaged
Type
Ductable Non Ductable
The systems are basically the same as far as making the conditioned air
is concerned, the only difference being where it is prepared and
methods of supply & return.

THE SELECTION OF EQUIPMENT FOR HEATING, COOLING
& VENTILATING IS A COMPLEX DESIGN DECISIONTHAT
MUST BALANCE WITH:
* HEATING
* COOLING NEEDS
* ENERGY EFFICIENCY
* HUMIDITY CONTROL
* POTENTIAL FOR NATURALVENTILATION
* ADHERENCETO CODES AND STANDARDS
* OUTDOOR AIR QUANTITY AND QUALITY
* INDOOR AIR QUALITY AND
* COST.

Sequential activities related to making conditioned air
Air conditioning is a process which cools (or heats), cleans, circulates,
freshens air & control its moisture content simultaneously.
Fresh
Air inlet
Air Filters
Air heaters
Air coolers
Blower fan
Humidifiers
Conditioned air is circulated by compression & suction created by
the blower/centrifugal flow fan. Both supply & return are parts of air
circulation system.

CENTRAL
PLANT
SYSTEM
 Centrally placed plant distributing air to all use spaces with use of ducting network.
 Nearly 80% of air returned back by return air ducts.
 Situated along with ancillary plants & equipments preferably on GF/ basements.
 Delivers air to weather maker rm. From where it is circulated vertically & horizontally.
 In the same manner the air is returned back to AC plant nearly up to 80% for reuse. About 20% is
taken as fresh air all times.
 conditioned air is circulated by the compression & suction by the blower centrifugal flow fan.

Suitable for large spaces where the air temp & relative humidity is constant , suitable
for open plan offices, theatres, cinemas, super markets & assembly halls.
 fresh air is drawn in, mixed with a proportion of recirculated air.
 air passes thru dry or viscous filter to remove suspended matter, further cleaned by
passing it thru electrostatic filter.
 In winter air heated by a preheating coil formed of finned Cu pipe, allow to absorb more
moisture in washer & also prevent freezing of water in spray.
 In summer, air is cooled by cooling coil, or passing the air thru cold water in spray.
 After leaving the washer, air passes thru two set of glass or G.I steel plates in zigzag
formation.
 first set is known as scrubber plates, second set is known as eliminator set designed to
intercept any droplets of water held in air, so that only absorbed moisture is carried
forward with the air to the final or reheated.
The inlet fan forces conditioned air into the building via inlet ductwork & diffusers.
Vitiated air is extracted from building by extract fan via extract ductworks & grills.
Extract fan is smaller than the inlet fan this causes slight pressurization of air inside
building, which prevents entry of draughts & dust.
 About 75% of extract air may be recirculated via recirculating duct.
CENTRAL PLANT SYSTEM

DUAL DUCT SYSTEM OF AIR CONDITIONING
System has two ducts, for hot & cold air
resp., Use of ducts provides means of
controlling varying temp.
 capable to meet most exacting room
climatic reqd.
 All main air conditioning units may be
housed in plant rooms & hot & cold air ducts
may be installed in ceiling void to mixing or
blending units.
 Air in the duct flows at higher pressure &
velocity which allows ducts to be smaller.
 Because of higher pressure & velocity fan
must operate at higher speed.
System requires more duct space than
central plant, usually arranged in false
ceiling, windows etc.
Besides variation in temp. system also provides varying ventilation rates, rooms with different
ventilation rates & air changes can be served from same plant.
 System does not operate on constant humidity principle.

Fresh air is drawn in main treatment plant & mixed as reqd. with recirculating air.
 Dust is removed in the filter, air is preheated & humidified in winter.
 In summer air is filtered, washed & cooled in cooling coil.
 Mixing of the hot or cold air streams passing thru the mixing units is controlled
by a room thermostat, so that supply air may be maintained at any temp. within
limits of hot or cold air streams.
This is known as constant volume controller & is an essential part of dual duct
system.

INDUCTIONCONVECTOR AIR CONDITIONING SYSTEM
Used as an alternative to dual duct system for
varying supply air temp. in multi roomed
buildings.
 utilizes hot or cold water pipes, but a single
duct is also reqd. for primary air from a main
conditioning unit.
 causes secondary air to be recirculated by
primary air passing thru nozzles in an induction
unit which causes good air movement.
 induced air flows over a cooling or heating coil
& cooled & heated secondary room air is mixed
with primary conditioned air before being
discharged.
 most common type of air/water system in use.
 operates on two pipe principle, flow & return
pipes are used.
 during summer chilled water is pumped from a
refrigerating unit & during winter hot water is
pumped from boiler plant.

INDUCTIONCONVECTOR AIR CONDITIONING SYSTEM
Operation of Plant
 inlet fan forces air thru primary air duct to various
induction units fitted below the windows.
 in winter, curtain of cold air descending past
windows can be drawn in & warm air curtain drawn
over window opening.
 In summer, stream of cold air blown vertically
upwards cools area around the window opening &
reduces solar heat gain inside the room.
 to keep duct size down to min. & to create
sufficient air velocity, the air velocity in the duct is
in order of 20 m/s.
 In summer chilled water is circulated thru finned
Cu pipe coils, during winter hot water is circulated.
 primary air at high velocity passes thru induction
nozzles inside the induction unit & reduces the air
pressure below nozzles.
 secondary air drawn inside the unit is mixed with
primary air before being discharged into the room.

AHU BASED AIR
CONDITIONING SYSTEM
 For preparation of conditioned air building is divided part wise & floor wise which is
managed by AHUs.
These self functioning units are conditioning air & supplying it to use spaces.
 Nearly 60-70% of air returned back by return air ducts to AHUs.
 No vertical connection between AHUs for fire safety.
 Chilled water @ 5-7 deg C is supplied by insulated Cu tubes from chiller plants. Used
water is returned back.
 Chilling plant for AC load of more than 50TR.
Air Handling Units

SPLIT SYSTEM OF AIR
CONDITIONING
 Single or Multi Split- Ductable or Non Ductable.
Works on principle of splitting or division of Unit AC System.
 Reason being mainly the problem of getting external wall for fresh air & release of hot
air.
Refrigerating machine along with noise generating units like compressors are kept
away.
 Ceiling, Floor or Wall mounted.

 Single split, Multiple split & ductable
also.

A window air conditioner unit implements a complete air conditioner
in a small space. The units are made small enough to fit into a standard
window frame.
It contains:
• A compressor
• An expansion valve
• A hot coil (on the outside)
• A chilled coil (on the inside)
• Two fans
• A control unit
The fans blow air over the coils to improve their ability to dissipate
heat (to the outside air) and cold (to the room being cooled).
WINDOW UNITAIR CONDITIONING

• The AC unit is consisting of air
filters, air humidifiers, air
cooling/heating, air delivery &
air return facility.
• The air movement is
undertaken by a multifunctional
blower fan creating air flow of
fresh air, from outside to volume
to be provided with conditioned
air .
• it is available in 0.50 TR, 0.75
TR, 1.00 TR, 1.25 TR, 1.50 TR,
2.00 TR, 2.50 TR & 5 TR capacity.
• it is one fan operated machine,
multiple jobs of taking fresh air,
return air & sending conditioned
air are all done together.

AIR CONDITIONING & HEATING WITH ROOM UNITS
• Room units condition the air in one
room
• Self-contained systems
• Cooling only or heating/cooling models
• Units that provide heating can use
electric strip heaters or reverse-cycle
refrigeration (heat pump)
• Some units can be used to condition
the air in more than one room

ROOM AIR CONDITIONING: COOLING
• Can be window or though-the-wall type units
• Most units have one fan motor that is used for both the evaporator and
condenser (2 shafts)
• Units can be front or top discharge
• Units can be fixed to the case or have a chassis that slides out of the case
(sleeve)
• Slide-out chassis are easier to service
 Installed in the window or through the wall
 Units should have a dedicated electric circuit
 Unit must be properly supported
 Air must be able to circulate freely
 Through the wall units can be installed during building construction (sleeves
are installed when walls are constructed and the units are slid in afterwards)

Combination Heating
&
Cooling Units
 some rm conditioners are offered with
electrical resistance, usually in the form
of strip heaters for supplying heat
during cool days, done instead of
incorporating reverse cycle system as
heat pumps.
 strip heaters are placed in the air
stream beyond the evaporator,
manually operated, with fan operating
but compressor turned off.
 with strip heaters all current drawn is
converted into heat. Additional heat is
provided by heat of fan motor.
 Wattage is same as drawn by
compressor motor.
Strip heater for room unit

Cooling only units
A room AC has two separate & distinctive air circuits:
 Outside Air over Condensor: air drawn into the unit from outside, passes thru air-cooled
condensor over motor compressor & back outside, carrying with it the heat removed
from condensor.
 Cooled Room Air: air drawn from the rm. Into the unit thru a filter that removes dust &
impurities, passes thru evaporator coil, where it gives up some heat, then back into the
room as conditioned air.

Combination Heating & Cooling Units
Advatages:
heating & cooling facilities in one package.
 Blower serves both sections, only one duct
system is required.
 Blower designed to handle larger usually
reqd. for summer cooling loads.
 Both operations are independent & air from
either side does not pass thru other side.
 minimum duct work required to connect unit
to air distribution system.
 Compact unit takes up less space.
Disadvatages:
Sometimes over capacity results, space
utilization, initial cost & additional wiring.

Heat Pump Units
 electrically driven device designed to
provide heating & cooling in the same
basic unit but operation is entirely different
& hence treated separately.
 used for residential & light commercial
application.
Operation depends on two simple facts:
1. There is always considerable heat in
air, at extremely low outside temp.
2. A cold object absorbs heat from
warmer one.
Construction of a room air to air
heat pump unit

Reverse Cycle:
Air to air heat pump Cycle:
in winter extracts heat from outside air &
uses it to heat the air inside the rm. in
summer operation is reversed to remove
heat from inside & release it outside.
 Water to water system
water to water system takes heat from
water source such as deep well & transfers
it to closed circulation water system.

PACKAGE AIR CONDITIONING: COOLING
 In case of higher capacities the unit AC
becomes larger in size.
 Needs network of supply & return.
 Capacity is 7TR, 10TR, 12TR etc.
 Built up spaces between 1200 to 1800 Sft
can be effectively served.
 include ceiling as well as floor mounted
units.
Commercial or residential uses.
 Consist of evaporator or cooling coil, compressor-condenser combination.
& may include heating function also.
 Compressors are reciprocating type, cooling coils are direct expansion type,
 Condensers can be air cooled or water cooled.
 Expansion devices are capillary tubes, thermostatic expansion valves are also used.

INSIDE OUTSIDE
Brace kit supplied
with unit

Return air to the
unit
Supply air to the
space
Window unit with
front discharge

Return air to the
unit
Supply air to the
space
Wall unit with top
air discharge

AC LOAD CALCULATION:AC DISTRIBUTION SYSTEMS
The heat & other gains are given below:
Rated capacity is expressed inTR=Ton
of refrigeration
Calculate the capacity of Ac plant for a
hall measuring 35’x 15’x 12’.
Volume of hall is 35’x15’x12’=6300 cft
Hence 6300= 6.3TR capacity
1000
If hall is provided with false ceiling at 10’
Then volume shall be 35x15x10= 5250 cft
Hence plant of 5.2TR will be reqd.

CIVILWORK FOR AC
ADDITION & ALTERATIONWORK FOR OLDWORK
 Partitioning: plywood, fiberboard, cement concrete walls, MS/ Aluminum frame, heat
insulation provided.
 False ceiling: POP, gypsum boards on G.I/ Al framework
plywood/particle board/bison panel board/
chipboard on GI/MS/Al framework
Fiberboard/foam concrete panels on MS framework
Lath plaster on structural RCC/ MS framework
 Updating Doors/ Windows/Ventilators/ glazed areas
Automatic door closers,Airtight by fibrous contacts at jambs, fixed non openable/ heat
insulation provided
 Insulation of walls & roofs
Glass wool, thermocol sheets, foam concrete panels
 Floor treatment & updating
Stone finishes like granite, marble, kota. PVC floor covers, ceramic tiles floor finish

WATER DEMAND FORAC
Water is required for;
Washing the air
 Humidifying the air
 Cooling the air by chilled water sprays & chilled water carrying tube grills &
heating air
Required as coolant in refrigeration plant
Water demand
 calculated on basis of rated capacity of AC plant
 water reqd for 1TR plant for 24 hrs is 4.0 gallons, apprx 4.0 lts.
Considering other losses of about 25-30% demand can be 40-50 lts per day.
 demand less in monsoon & winter period.
 2 days stock in UG tanks & 1 day stock in OH tank.

SPACE REQD FOR AC PLANT & ANCILLARYACTIVITY
The built up space is required for:
• space for water chilling plant & ancillary requirements like storage tanks,
cooling towers, water treatment plant etc.
• space for electrical substation, stand by generator & electric control room.
• space on ground & upper floors for placement of AHUs & electric control.
• space on terrace for water storage tank.
• some service space adjacent to AHUs for cleaning of air filters.
The area requirement is as follows:
• For AC plant of 100TR capacity following areas with 3m ht.
• On ground floor 100m2 for water chilling paint & ancillaries.
• 20 m2 per AHU on GF & upper floors.
•

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