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CHAPTER 2

AIR-CONDITIONING SYSTEM

2.1 Introduction

TM Jalan Raja Chulan uses a centralized chilled water air-conditioning system. The entire system

consists of the chiller, cooling tower, pumps, air handling units (AHU), fan coil units, ducting,

compressors and vents. There are also several separate mini split units installed in certain

offices for single room air-conditioning. The information, pictures, and analysis gathered from

the site visits and drawings will aid in explaining how this centralized system works, from the

initial component until distribution and delivery.

Analysis on all the data will then be crossed referenced with the Uniform Building by Laws

requirements to assess whether or not the TM building follows the requirements.

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2.2 Literature Review

A central air-conditioning system is necessary in high-rise commercial building such as TM

building. This system handles the removal of heat from the interior of the building and helps

maintain it at a cool temperature that is comfortable for staff to function in. However, the term

air-conditioning does not only mean to cool or lower the temperature of a room, but also can

serve to heat, ventilate, disinfect, or simply modify the condition of air. The centralized unit of

the case study cools and dehumidifies the air and then circulates it throughout the building. The

system depends on electrical power and ducting for its distribution. The process involves a

refrigeration cycle that will be explained below.

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Air-conditioners use a chemical known as refrigerant which easily converts from a gas to a

liquid, and back to gas. The three main mechanical components responsible for this process are

the compressor, condenser, and the evaporative coil. The compressor compresses and

squeezes the gas and reduces its volume. The more compact it gets, the pressure will increase,

and simultaneously increases the temperature of the gas. Hot gas will then flow from the

compressor into the condenser. This condenser then turns the hot gas into a liquid by releasing

and removing the heat. The fan blows across the hot coil and as the hot air is blown out, the

refrigerant inside the coil is cooled.

Once the fluid passes through the condenser, the temperature is much lower. It flows

into the evaporator coil through a tiny tube that passes through the expansion valve.

The temperature of the liquid then drops and it flows into the evaporator coil where it

evaporates while absorbing heat from the return air blown over the indoor coil by a fan.

The refrigerant then flows back out to the compressor and the cycle is repeated.Connected to the evaporator is a fan that circulates the air inside the house to blow

across the evaporator fins. Hot air is lighter than cold air, so the hot air in the room rises

to the top of a room. There is a vent there where air is sucked into the air conditioner

and goes down ducts. The hot air is used to cool the gas in the evaporator. As the heat is

removed from the air, the air is cooled.

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2.3 Air-conditioning System

2.3.1 Chiller

A water chiller is a refrigeration machine that produces chilled water (approx. 7 - 12C). The

chilled water is sent to the AHU room which is used to generate cold air to circulate the building.

It is critical in Telekom Malaysia Jalan Raja Chulan that the temperature of the building is

maintained as the building is filled with very important and high voltage equipment that can

heat up very easily. The equipment in this building is essential to the TM Communication

system. This segment will focus on the water cooled chiller in the building that is manufactured

by York.

The primary function of a chiller is to lower the temperature of the water to such a value so that

it can be used for producing the cooling effect in integration with other AC components. A

centrifugal chiller utilizes the gas compression cycle to chill water and reject the heat collected

from the chilled water, plus the heat from the compressor to a second water loop that is in turn

cooled by the cooling tower.

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Figure: Basic Refrigeration Cycle (Water cooled condenser)

Process 1 2 Heat addition to refrigerant in evaporator:

The refrigerant gets vaporized by taking heat from chilled water in the evaporator thus serving

its prime purpose. The refrigerant comes out of the evaporator as a gas but on the other side

chilled water is produced. Thus heat is added to refrigerant as constant pressure but is extracted

from chilled water. Both refrigerant and chilled water dont get mixed and are separated by apartition in between them in the evaporator.

Process 2 3 Compression of Refrigerant Gas in Compressor

Refrigerant gas come out of the evaporator and then is compressed by the chiller compressor to

high pressure and temperature. The compressor requires energy input for its working and hence

electric energy is supplied to it.

Process 3 4 Heat Rejection by refrigerant in condenser

Similar to evaporator but the reverse is happening here. Refrigerant rejects its heat to outside

cooling liquid or air. In this way the refrigerant gets condensed and outside media (cooling

water).

Process 4 1 Expansion of refrigerant in expansion valve

Refrigerant in condensed form coming out of condenser is expanded in expansion valve and its

pressure and temperature is reduced to a level ready for evaporation to take place so that the

cycle can be repeated again.

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2.4 AHU

The AHU room is the central controlling unit for the circulation of air that produces the cool air

and recycles the hot air from the public spaces. The ducting system is connected to this and

distributed to all the spaces and levels in the building.