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Issues in Air Conditioning and Mechanical Ventilation System Design
By Low Cheng Yee , Ow Chee Sheng , Abu Hashim Abd Ghani , Hazran Husain , Tan Chee Fai
Air-Conditioning and Mechanical Ventilation ( ACMV ) systems provide thermal comfort and acceptable indoor air quality to the occupants of a building . Such systems are important in the structural design of residential , commercial , leisure , healthcare and industrial buildings where safe and healthy building conditions are regulated with respect to temperature , humidity and the introduction of conditioned fresh air from the outdoors .
Air conditioning [ 1 ] is the process of controlling the temperature and humidity in a building typically to maintain a cool atmosphere to suit human comfort . It is a system that removes heat from the air inside an occupied space , thus lowering the air temperature . The cooling is typically achieved through a refrigeration cycle . Air conditioning is also intended to maintain air cleanliness through a filtering element as well as its distribution within the space .
Ventilation is the process of introducing and circulating fresh air in any space to provide high indoor air quality . This process involves temperature control , oxygen replenishment and removal of moisture , odours , smoke , heat , dust , airborne bacteria and carbon dioxide . In addition , ventilation includes both the exchange of air to the outside as well as circulation of air within the building . It is one of the most important factors for maintaining acceptable indoor air quality within buildings .
ACMV System & Design Process
There are various types of air conditioning systems . Table 1 lists these and their cooling capacity . A typical system installed in Malaysia is the Water-Cooled Chilled Water System . It is a large system with design capacity in most cases above 200 Tons of Refrigerant ( TR ). The system architecture is illustrated in Figure 1 .
The basic equipment for Water-Cooled Chilled Water System includes a Chiller , a Chilled Water Pump , a Condenser Water Pump , a Cooling Tower , Air Handling Units ( AHU ) and Fan Coil Units ( FCU ). Heat exchange takes place between the Condenser Water Open Loop , Chilled Water Closed Loop , and as well as between the Chilled Water Closed Loop and Air Circulation .
Type |
Application |
Tons of Refrigerant ( TR ) |
Window Unit / Split Unit |
Small room / space |
< 5 |
Air-Cooled Package Unit |
Small room and difficult to get |
5-20 |
|
water supply |
|
Water-Cooled Package Unit |
Medium system |
20-40 |
Air-Cooled Chilled Water System |
Medium large system |
40-100 |
Water-Cooled Chilled Water System |
Large system |
> 100 |
District Cooling |
Large system |
> 2000 |
Source : JKR ’ s Guideline on Air-Conditioning System Design [ 2 ] Table 1 : Types of Air-Conditioning Systems
34 VOL 71 JULY - SEPTEMBER 2017