Chiller and water cooling system

Chiller and water cooling system is usually used in commercial building as a part of air conditioner system. Basically, chiller system consists refrigeration cycle which is used at common air-conditioner, it may be vapor compression or absorption. The difference between chiller and common air conditioner is what the machine cools. In common air conditioner, heat transfer occurs from air to evaporator (refrigeration system). But in chiller system, air is not cooled by evaporator. We can imagine how much refrigerant needed if we just use common air conditioner and how much power consumption for compressor. Chiller system uses refrigeration to cool water first, then cooled water will be pumped to Air handling unit (AHU).

In chiller system, there is heat exchanger which can be used to transfer heat from liquid to liquid, in this case between refrigerant to water. The common heat exchanger is shell and tube heat exchanger. Water temperature at outlet is colder than inlet because heat is transferred from water to refrigerant. This cooled water is pumped to Air Handling Unit (AHU). Heat transferred from room air occurs at this AHU. Air from AHU is cold and will be distributed by ducting to the room. 

Similar process is also used is water cooling system. In refrigeration cycle, condenser needs to release heat to ambient. Common air conditioner transfers heat from condenser to air. Condenser temperature is higher than outdoor temperature, thus heat transfer from condenser to the air can occur. This is why condenser is put outside. Basically we can put condenser inside, but it will make higher heat gain and it will be more difficult to cool the air.

In water cooling, condenser transfer heat to the water, Temperature of water at outlet is higher than inside. Outlet water from chiller (condenser) is pumped to cooling tower to be cooled, then this water flow to chiller again (condenser).  

Air conditioning and Ventilation

Air conditioning

Air conditioning is treatment to make temperature, humidity, cleanliness of air meet the requirements of conditioned space. It also includes the distribution of air. Air conditioner can be divided in to several types, those are direct expansion coolers, chilled water system, and evaporative coolers.

 Direct expansion cooler is the kind of usual air conditioner that found in residential house. This air conditioner uses refrigeration cycle as its principle. Air is blown through the cold part (evaporator) and distribute to the room.

Chilled water system doesn’t  cool the air directly. This air conditioner cool water and then water will be flown to the Air Handling Unit (AHU) to cool the air.

Evaporative cooler is usually used in hot and dry climate region. This air conditioner evaporates the water sprayed and resulting lower temperature of air.

Ventilation

Ventilation is the process that removes or supplies air at the room. Every room has function, such as class room, laboratory, etc. Those rooms have different requirements of ventilation. Designing HVAC system consider many aspects of parameter, one of them is how much air must be supplied.  This parameter can be achieved by designing ventilation system.

All parameter HVAC design requirement are treated to make thermal comfort for the occupancy. ASHRAE made a standard about human comfort. (ASHARE STANDARD 55)