air+conditioning introduction

8/13/2019 Air+Conditioning introduction

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Home Cooling

PRESENTATION BY

PROF.B.H.SUTARBVCOA-PUNE


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PROF B.H.SUTAR BVCOAPUNE 2

What is Air Conditioning?

The first functional definition of air-conditioningwas created in 1908 and is credited to G. B.Wilson . It is the definition that Willis Carrier , thefather of air conditioning subscribed to:


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Maintain suitable humidity in all parts of a building

Free the air from excessive humidity during certainseasons

Supply a constant and adequate supply of ventilation

Efficiently remove from the air micro-organisms,dust, dirt, and other foreign bodies

Efficiently cool room air during certain seasons

Heat or help heat the rooms in winter

Function of Air Conditioning


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The job of your home air conditioneris move heat from inside your hometo the outside , thereby cooling youand your home.

Air conditioners blow cool air intoyour home by pulling the heat out ofthat air.

The air is cooled by blowing it over aset of cold pipes called an evaporatorcoil.

HOW AN AIR CONDITIONER WORKS?


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This works just like the cooling thathappens when water evaporatesfrom your skin. The evaporator coil is filled with aspecial liquid called a refrigerant ,which changes from a liquid to agas as it absorbs heat from the air.

The refrigerant is pumped outsidethe house to another coil where itgives up its heat and changes backinto a liquid.


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This outside coil is called thecondenser because the refrigerant iscondensing from a gas back to a fluid

just like moisture on a cold window.

A pump, called a compressor , is usedto move the refrigerant between thetwo coils and to change the pressure of

the refrigerant so that all the refrigerantevaporates or condenses in theappropriate coils.


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WHAT A 'TON' OF COOLING IS ?

Before refrigeration air conditioningwas invented, cooling was done bysaving big blocks of ice. When

cooling machines started to get used,they rated their capacity by theequivalent amount of ice melted in aday, which is where the term ton

came from sizing air conditioning.


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One Ton of Cooling


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If airflow across the outdoor(condenser) coil is reduced, theability to reject heat outdoors isreduced and the again the capacityof the system may go down,especially at higher outdoortemperatures.


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In dry climates the same issues happenwith regard to the indoor (evaporator)

coil: higher airflow helps, lower airflowhurts. In humid climates, the situation ismore complex. At higher airflows, therewill be less dehumidification, leading tohigh indoor humilities.If the airflow gets too low, however, theevaporator coil may freeze. This makesperformance worse and can damage thecompressor until it fails - leaving youwith an expensive repair bill and nocooling!


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WHAT THOSE FILTERS DO?

Almost every air conditioning systemhas a filter upstream of the evaporatorcoil. This can be in the return grille or in

special slots in the duct system and canbe a fuzzy-looking or a folded paperfilter. This filter removes particles fromthe air stream to both keep the airconditioning system clean and toremove particles from the air.


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As the filter does its job, it getsloaded with more and more particles.This actually has the effect of makingit more efficient, but it also increases

resistance and reducing airflow .When this happens, it is time tochange the filter. How long it will taketo happen depends on how dirty the

air is and how big the filter is.


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MAINTAIN THE SYSTEM

Routine maintenance such as changing filters

can be handled by most consumers, butothers require professional service.Its a good idea to brush dirt and obstructionsfrom the coils and the drains at the start of

each cooling season. Depending on thesystem and the consumer, this may require aservice call from a professional.If the system is not producing as much cold airas is normal, it could also be an indication of arefrigerant charge or airflow problems. Theseproblems may require servicing.


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DUCTS MATTER - A LOT Another reason systems may appear

not to be producing enough cold air isbecause of duct leakage . Duct leakagecan sap 20 to 40% of the energy out ofeven a well-operating air conditioner, if theducts pass outside the cooled space (thisincludes attics, crawlspaces and garages).Ducts outside need to be well insulated.

Various products exist specifically forinsulating ducts that can be installed by akeen home owner or a professionalcontractor.


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DUCTS MATTER - A LOT

You might be able to get an extra halfton of air conditioner capacity for free,if you seal your leaky ducts.If the ducts are accessible, handyconsumers can seal ducts withmastic that white sticky stuff you can

paint on the ducts. Otherwise youwould need a professional to seal theducts.


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HOW TO INCREASE ENERGY EFFICIENCY

Sealing leaky ducts may be the biggestsingle thing you can do to improveefficiency, but a lot of the issuesmentioned about will help as well: replace

dirty filters , keep the right charge andairflow, clean the coils.

Another thing to do is to make sure theoutdoor (condenser) unit is not so hiddenfrom sight that its air flow is blocked or thatleaves or other matter are not clogging it.


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Depending on your climate, you may wishto consider other efficiency numbers aswell.For example, in hot, dry climates you

should look at the Energy EfficiencyRating (EER) which says how well thesystem will work at peak conditions.

If you live in a hot, humid climate you

need to consider how well the unit candehumidify.


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LIGHTEN YOUR LOAD You can make your air conditioner work better byreducing the size of the job it has to do.

You can do this by improving the building or reducingthe internally generated loads that your air conditionermust deal with.Improving the building envelope includes things

such increasing insulation levels or shading windowsor reducing air leakage.Such improvements will reduce energy spent onheating and cooling, but may require substantial timeor investment.When putting in a new roof or new windows, it isusually cost effective to use high-efficiency products .Cool roofing, for example, can save half a ton ofcooling and a lot of energy over the year.


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Reducing internal loads can be simpler.Shut off unneeded electrical appliances,lights and equipment.Shift appliance use (such as washers anddryers) to cooler times of the day.

Use local exhaust fans to remove heatand humidity from kitchens and baths.

Buying Energy Star or similarly efficiencyappliances helps as well.


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VENTILATEThe previous points have focused on

cooling, but the original definition of airconditioning contains more than that; anideal air conditioner should heat, cool,clean, ventilate, humidify and dehumidify asneeded to provide health and comfort. Infact the second most important objective ofthe original definition is to provideventilation. Whether or not the piece ofequipment we call an air conditionerprovides it, ventilation is needed.


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Without adequate ventilation, contaminantsgenerated indoors will can lead to

significant health and comfort problems.Recommendtions that there be at leastenough ventilation to exchange the airinside house once every four hours,depending on house design.Older homes tend to have leakier walls andleakier ducts and mostly get sufficientventilation through such leakage. Suchleakage and infiltration may not be the mostenergy efficient approach to ventilation andis an opportunity for savings.


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Moving Heat from the Inside to the Outside


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Heat Transfer at the Inside Coil


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Evaporator Coil Collecting Hot Air Inside the House


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The Freon Gas Goes Outside

Gas Cools As thehot, high-pressuregas moves throughthe outdoor coil andgives off itsand Condenses

heat, it cools to thepoint where itcondenses back to aliquid. Logicallyenough, theoutdoor coil is called

the condenser coil(Figure 1.6)because the Freoninside condensesfrom a gas to aliquid


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Condenser Coil Exhausting Hot Air to the Outside


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Air Conditioning Schematic of System


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Water-Cooled Air Conditioning Schematic of System


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How Much Area Can One Ton Cool?


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Bigger Is not Better


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Function of an Air conditioner


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Humidity in air

Relative Humidity A measure of ofmuch water is in the

air relative to themaximum amountair can hol at thattmperature


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Arrangement


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Compressors Heating up Freon Gas


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TYPES OF AIRCONDITIONERS

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 thanthe entire home.Less expensive to operate than central units

Their efficiency is generally lower than that ofcentral air conditioners.Can be plugged into any 15- or 20-amp, 115-volthousehold 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 andreturn ducts. Supply ducts and registers (i.e.,openings in the walls, floors, or ceilings coveredby grills) carry cooled air from the air conditionerto the home.This cooled air becomes warmer as it circulatesthrough the home; then it flows back to thecentral air conditioner through return ducts andregisters


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Types of Central AC

split-systeman outdoor metal cabinet contains thecondenser and compressor, and an indoor

cabinet contains the evaporator Packagedthe evaporator, condenser, andcompressor are all located in one cabinet

d


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Large air conditioningsystems

Outside air is drawn in, filteredand heated before it passesthrough the main airconditioning devices. Thecolored lines in the lower partof the diagram show thechanges of temperature and ofwater vapor concentration (notRH) as the air flows throughthe system.


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Total Air Conditioning


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Variable fresh air mixer and dust andpollutant filtration.Supplementary heating with radiators inthe outer rooms and individual mini heaterandHumidifier in the air stream to each room.

Si i Ai C di i


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Sizing Air Conditioners

how large your home is and how many windowsit has;how much shade is on your home's windows,walls, and roof;how much insulation is in your home's ceilingand walls;how much air leaks into your home from the

outside; andhow much heat the occupants and appliances inyour home generate


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Energy Consumption

Air conditioners are rated by the number ofBritish Thermal Units (Btu) of heat they canremove per hour. Another common rating term

for air conditioning size is the "ton," which is12,000 Btu per hour.Room air conditioners range from 5,500 Btu perhour to 14,000 Btu per hour.


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Energy Efficiency

Today's best air conditioners use 30% to50% less energy than 1970sEven if your air conditioner is only 10years old, you may save 20% to 40% ofyour cooling energy costs by replacing itwith a newer, more efficient model


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Energy Efficiency

Rating is based on how many Btu per hour areremoved for each watt of power it drawsFor room air conditioners, this efficiency rating is

the Energy Efficiency Ratio, or EERFor central air conditioners, it is the SeasonalEnergy Efficiency Ratio, or SEER


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Room Air Conditioners

Built after January 1, 1990, need have anEER of 8.0 or greater

EER of at least 9.0 if you live in a mild climateEER over 10 for warmer climates


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Central AC

National minimum standards for central airconditioners require a SEER of

9.7 for single-package and10.0 for split-systemsUnits are available with SEERs reachingnearly 17


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Energy Saving Methods

Locate the air conditioner in a window orwall area near the center of the room andon the shadiest side of the house.Minimize air leakage by fitting the room airconditioner snugly into its opening andsealing gaps with a foam weather stripping

material.


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Numerical Problem

A EER from 5.0 to 9 saving and pay backperiod


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PROF B H SUTAR BVCOAPUNE 59

Thank you

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