ac types 2.pptx

7/27/2019 AC Types 2.pptx

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AIRCONDITIONING

TYPES OF AIR CONDITIONERS


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TYPES OF AIR CONDITIONERS

I. Self-contained room units:

Cooling only units Cooling & Heating Units Heat pump units

II. Central Systems:

Packaged Units Remote or Split Systems Combination Heating & Cooling Units Heat pump Units Built up Systems


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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 thatremoves dust & impurities, passes thru evaporator coil, where it givesup somr heat, then back into the room as conditioned air.


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Air Cooled&Water Cooled Condensor

Used in areaswhere free airsupply is limitedor non existant


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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 workalong 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 orliquid 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).


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WATER COOLED AC SYSTEMS

use water as a chiller toremove 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.


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Combination Heating&

Cooling Units

some rm conditioners are offered withelectrical 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 isprovided by heat of fan motor.

Wattage is same as drawn by

compressor motor.

Strip heater for room unit


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Combination Heating & Cooling UnitsAdvatages:heating & cooling facilities in one package.

Blower serves both sections, only one duct system

is required.

Blower designed to handle larger usually reqd. forsummer 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.


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Heat Pump Units

electrically driven device designed toprovide 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


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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.
http://inspectapedia.com/aircond/5Mc_Addition_2633_DJFs.jpghttp://inspectapedia.com/aircond/Air_conditioner_Portable023-DJFs.jpg


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PACKAGE AIR CONDITIONING: COOLING

In case of higher capacities the unit AC becomes larger in size. Needs network of supply & return. Capacity is 7 TR, 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-condensorcombination.

& may include heaqting function also. Compressors are reciprocating type, cooling colis are direct expansiontype,Condensors can be air cooled or water cooled. Expansion devices are capillaryv tubes, thermostatic expansionvalves are also used.


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Air conditioning ducts

Uses: Air Distribution

efficient method of conveying & distributing cold air.Without ducting the effect of a fan, air conditioner or cooler islimited to a small area but ducting allows the cold air to bedirected to specific hot spots to provide localised cooling, ordiffused over a wide area to reduce temp. gradients. usually suspended overhead from steel wires.

Rows of small holes in the sides of the ducts produce jets ofcold air that mix with the warmer room air before falling tofloor level. Leading to draft free air movement thru out thebuilding and reduced temperatures. By using numerous small jets the air velocity is kept low,ensuring the workforce do not complain of uncomfortable cold

drafts.


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Desirable qualities: Smooth surfaces offer min.

resistance to flow Air tight for no leakageWater proof insulating qualities-min. 2-4thk Min. sound transmission


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Duct Materials: Galvanised Steel Aluminium

Copper & Brass Laminated asbestos Spring steel wire Woven fibre glass


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Insulation


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Commonly used System Conventional system: branch &section sized on quantity of air to becarried.

Small pipe system: air is deliveredthru 31/2 or 4 round pipe with

prefabricated fittings & specialoutlets.

Extended Plenum system: large

main duct of uniform dimension thruout its length with branches taken offthru special fittings.


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Duct Layout

Commonly used System Conventional system: branch & section sized on quantity of air to be

carried. Extended Plenum system: large main duct of uniform dimensionthru out its length with branches taken off thru special fittings.Small pipe system: air is delivered thru 31/2 or 4 round pipe withprefabricated fittings & special outlets.

Duct Layout requirements: to determine air movement required in each room-found by sensiblecooling & heating load of each room. to determine supply air temperature-usually ranges from 50-65 degF for cooling & 100-150 deg F for heating. figuring sizes of various duct sections- round duct will carry moreair with less friction loss than other shape & same given cross

section. Square ducts are better than rectangular.

ac types 2.pptx

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