evaporator coils that remove heat from the building. The hot air in the build-
ing is passed over the evaporator coils, adding heat to the refrigerant and
removing heat from the air, which is recirculated back into the building. The
added heat turns the refrigerant to vapor, which is sent back to the compres-
sor, completing the cycle.
Chiller condensers remove heat from the system via cooling air, cooling
water, and evaporation. Air-cooled systems are typically found in residential
homes and commercial buildings where the cooling load is less than 100 tons
(Fig. 3.3). The air-cooled condenser is comprised of coils that house the flow-
ing refrigerant and maximize convective surface area (the area for the transfer
of heat), and a forced air source (typically a fan) that uses convection to
extract heat from the refrigerant and remove it from the system altogether.
Water-cooled systems are used for buildings that require large cooling
loads, and typically have higher efficiencies than air-cooled systems.
(Fig. 3.4). Instead of using air to remove the heat from the refrigerant, water
is used to extract heat. Once the heat is extracted the water is then pumped
to a cooling tower, where the heat is rejected back into the atmosphere and
the water is then pumped back to the condenser (Fig. 3.5). Cooling towers
reject heat by using an air stream to evaporate a portion of the incoming
water, thereby cooling the rest of the incoming water. The heat transferred
to the air causes it to rise, flowing out of the top of the tower and into the
atmosphere.
Figure 3.3 Air cooled chiller.
Heating, Ventilating, and Air Conditioning Systems 35