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Home Cooling
EGEE 102
Function of an Air
conditioner
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Humidity in air
• Relative Humidity
• A measure of of
much water is
in the air
relative to the
maximum
amount air can
hol at that
tmperature
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EGEE 102 - Pisupati
http://www.ae.iastate.edu/Ast473/Lectures/%285%29Psychrometric_Chart/sld024.htm
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Principle
A. Expansion Valve
B. Compressor
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Arrangement
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TYPES OF AIR
CONDITIONERS
•
•
•
•
Room air conditioners
Central air conditioning systems
Heat pumps
Evaporative coolers
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Air Conditioning
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Room air conditioner
• Room air conditioners cool rooms rather
than the entire home.
• Less expensive to operate than central
units
• Their efficiency is generally lower than
that of central air conditioners.
• Can be plugged into any 15- or 20-amp,
115-volt household circuit that is not
shared with any other major appliances
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Central Air conditioning
• Circulate cool air through a system of
supply and return ducts. Supply ducts and
registers (i.e., openings in the walls,
floors, or ceilings covered by grills) carry
cooled air from the air conditioner to the
home.
• This cooled air becomes warmer as it
circulates through the home; then it flows
back to the central air conditioner
through return ducts and registers
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Types of Central AC
• split-system
• an outdoor metal cabinet contains
the condenser and compressor,
and an indoor cabinet contains the
evaporator
• Packaged
• the evaporator, condenser, and
compressor are all located in one
cabinet
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Large air conditioning
systems
• Outside air is drawn in,
filtered and heated before
it passes through the main
air conditioning devices.
The colored lines in the
lower part of the diagram
show the changes of
temperature and of water
vapor concentration (not
RH) as the air flows
through the system.
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Total Air Conditioning
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• Variable fresh air mixer and dust and
pollutant filtration.
• Supplementary heating with
radiators in the outer rooms and
individual mini heater and
• Humidifier in the air stream to each
room.
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Sizing Air Conditioners
• how large your home is and how many
windows it has;
• how much shade is on your home's
windows, walls, and roof;
• how much insulation is in your home's
ceiling and walls;
• how much air leaks into your home from
the outside; and
• how much heat the occupants and
appliances in your home generate
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Energy Consumption
• Air conditioners are rated by the number
of British Thermal Units (Btu) of heat they
can remove per hour. Another common
rating term for air conditioning size is the
"ton," which is 12,000 Btu per hour.
• Room air conditioners range from 5,500
Btu per hour to 14,000 Btu per hour.
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Energy Efficiency
• Today's best air conditioners use
30% to 50% less energy than 1970s
• Even if your air conditioner is only
10 years old, you may save 20% to
40% of your cooling energy costs by
replacing it with a newer, more
efficient model
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Energy Efficiency
• Rating is based on how many Btu per hour
are removed for each watt of power it
draws
• For room air conditioners, this efficiency
rating is the Energy Efficiency Ratio, or
EER
• For central air conditioners, it is the
Seasonal Energy Efficiency Ratio, or
SEER
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Room Air Conditioners
• Built after January 1, 1990, need
have an EER of 8.0 or greater
• EER of at least 9.0 if you live in a
mild climate
• EER over 10 for warmer climates
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Central AC
• National minimum standards for
central air conditioners require a
SEER of
• 9.7 for single-package and
• 10.0 for split-systems
• Units are available with SEERs
reaching nearly 17
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Energy Saving Methods
• Locate the air conditioner in a
window or wall area near the center
of the room and on the shadiest side
of the house.
• Minimize air leakage by fitting the
room air conditioner snugly into its
opening and sealing gaps with a
foam weather stripping material.
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Numerical Problem
• A EER from 5.0 to 9 saving and pay
back period
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