Download - Air Conditioning System Note

8/10/2019 Air Conditioning System Note

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Dengan nama Allah yang

maha pemurah lagi maha penyayang..

Ya Tuhanku, lapangkanlah

dadaku dalam menjalankan

tugasku, bukalah simpulan

lidahku supaya muridku

memahami setiap

perkataanku.

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Air conditioning is the treatment of theair to:

Control temperature

Control Humidity

An air conditioner is an appliance, system,or mechanism designed to extract heat from an area usinga refrigeration cycle. In construction, a complete system ofheating, ventilation and air conditioning is referred to as“HVAC".

Provide ventilation or air movement

Clean the air

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Other definition……

• Air conditioning is the process to control andmaintenance the air in space or enclosed areas.

Mechanical treatments performed on thetemperature, humidity, air renewal, cleanliness

and distribution of air to achieve the requirementsand functions of an item.

• Air Conditioning is the process of treating air in aninternal environment to establish and maintain

requirement standards of temperature, humidity,cleanliness, and motion.

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Basic principles are based on mass characteristicwith temperature, heat and pressure

“Is the treatment of air inenclosed space to control and

to maintain temperature, heat

and pressure together”

ASHRAE STANDARD definition:

Air conditioning is the process whereby the condition of air,as defines by its temperature an moisture content, is changed.

Other factors must also be taken into account especiallycleanliness; odor; velocity & distribution pattern.

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• Evaporator (The cooling coil) —

A heat exchanger wherethe heat from the area or item being cooled is transferredto the refrigerant. Change the form of refrigerant liquid togas.Compressor — creates the pressure differences or increase

the gas pressure in the system that needed to makerefrigerant flow and the refrigeration cycle work.

• Condenser — A heat exchanger where the heat absorbedby the refrigerant is transferred to the outdoor air oranother cooler substance. Change the form of refrigerant

gas to liquid• Expansion device (The expansion valve) — provides a

pressure drop that lowers the boiling point of therefrigerant just before it enters the evaporator. This is alsoknown as the metering device.

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The major pieces of equipment required to complete the air-conditioning cycle are listed as follows:

fan

supply ducts

supply outlets

space to be conditioned

return outlets

return ducts filter

heating coil (combustion chamber) or cooling coil

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The Fan

The fan moves air to and from an enclosed space. In an air-conditioning system, fan moves air that consists of:

all outdoor air

all indoor or room air

a combination of outdoor and indoor air

The fan pulls air from the outdoor and from the room at the same time.Since drafts in the room cause discomfort, and poor air movementslows the body heat rejection process, it is necessary to regulate theamount of air supplied by the fan. To accomplish this regulation a fan is

selected that can deliver the correct amount of air. By controlling thespeed of the fan, the air stream in the room can be regulated toprovide good circulation without drafts.

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The supply duct

The supply duct directs the air from the fan to the room. Atypical duct arrangement is shown below. The supply ductshould be as short as possible and have a minimum number ofturn to ensure that the air can flow freely.

Supply Duct

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Supply Outlets

Supply outlets help to distribute the air evenly in a room. Some outlets

fan the air and other outlets direct the air in a jet stream. Still otheroutlets combine these actions.

As a result of these actions, the outlets are able to exert some controlon the direction of the air delivered by the fan. This directionalcontrol plus the location and the number of outlets in the roomcontribute greatly to the comfort or discomfort resulting from the air

pattern.

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Room Space

The room or the space to be conditioned is one of the most importantparts of the air cycle. If an enclosed space does not exist, then it isimpossible to complete the air cycle.



Return Outlets

As stated previously, return outlets allow room air to enter thereturn duct. The main function of the return outlet is to allow airto pass from the room. These outlets are usually located on theopposite wall from the supply outlet. For example, if the supplyduct is on the ceiling, or on the wall near the ceiling, then thereturn duct may be located on the floor or on the wall near

the floor.

This situation is not true in all installations, however. Some systemsare provided with both the supply and the return near thefloor or near the ceiling.

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Filters

Filters clean the air by removing dust, suspended particles, contaminants and

odours. Filters are located within the return air duct. These devices are made

of many materials including spun glass and composition plastic.

Other filter materials maintain an electrostatic charge, and attract and capturedust and dirt particles from the air flowing through them.

There are 4 classification for filters:

i. Dry

ii. Viscous

iii. Electrostatic

iv. Activated Carbon

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Dry Filter- producedfrom paper, finewoven fabric,

foamed plastic orglass fibers.

Electrostatic Filter-very expensive,extremely efficientof removing fineparticles, pollens,smoke.

Viscous Filter – comprise rows ofcorrugated metal sheets withsurface coated in a non-

flammable, non toxic odourlessoil.

Activated Carbon Filter-location in cooker hood. Veryabsorbent and special designfor use in greasy and odoursatmosphere.



1. Performance requirementsOn comfort, noise, control options, flexibility and meetingrequirements of local regulations/codes

2. Capacity requirements

Range of capacity, multiple units, zoning, etc. 3. Spatial requirement

Plant room space, space for ducting and piping (verticalshafts),space for terminal equipment

4. CostsInitial cost, operating cost and maintenance cost

5. Energy consumptionFor both economic and environment reasons

6. System qualitiesAesthetics, life, reliability and maintainability

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AC system

Unit System Window Unit

Package Unit

Split unit

Water and air cooling

Air cooling

Water cooling

Split unit without

outdoor air

Split unit with outdoor

air Plant system

Air Handling unit

Centralized system



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A. Unit systems

i) Split system

In split system, the condenser and compressor arelocated in an outdoor unit but the evaporatoris located inside the building.

Typically, the evaporator is mounted in the airhandler unit.

ii) Packaged System In a packaged system, as the name suggests, all

components – the condenser, the compressorand the evaporator are located in a single

outdoor unit. The entire unit is generally located on the groundor on the roof.

Packaged systems are generally used when thereis limited space.

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A split air conditioner splits the hot side from the coldside system, like this:

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- With the packaged system, all the components which may

also include heating coils or a furnace , are located in a singlecabinet- The cabinet is located on the roof of the structure or on theconcrete slab next to the structures foundation.

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iii. Window unit

Window units (also known as room units), are designedto air condition a portion of the residence.

The capacity of such a unit is designed so that a givenunit size is adequate to condition one room.

Thus, a unit in a larger size is satisfactory for more thanone room.

If the unit is to be used for more than one room;however, the arrangement of the rooms must insuregood airflow.

Although a unit may be designed to air condition onlyone room, several window units can be used to aircondition an entire residence.

In fact, it is possible to air condition an entire multi-roomcommercial building using window units.

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1. Comfort conditions are maintained in every room in the house.2. A central automatic control points is provided.3. Since the cooling and heating equipment is installed in one

locationrather than several locations, the maintenance of the system is

easier.4. Better air distribution.5. One of the major differences between central systems and

window units is the higher equipment and installation cost of thecentral system.

6. Efficient air circulation7. Improve your indoor air quality.8. Level of indoor noise is almost negligible (system the condenser,

including the fan and the compressor, is located in an outdoorunit)

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1. A separate temperature control is provided in eachroom or area in which a unit is installed.

2. Ducts are not required. This advantage is especiallynoticeable in residences in mild climates wherecentral heating systems are not required. The

advantage may not apply in cooler regions whereduct systems are necessary for winter heating,regardless of the summer requirements.

3. Plumbing is not required.

4. The installation of the unit is simple; therefore,changes in the construction of the residence usually

are not required.5. Some types of window units are fitted with heating

coils and can be used a; supplementary sources ofheat.

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1. The unit requires space in a window/wall.

2. In general, the unit has a fixed air quantity.

3. The installation must be made on an outside wall.

4. Appearance may be a factor.

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