Most commercial buildings make use of HVAC systems to maintain their temperatures. Today, chillers are mainly used for cooling purposes in these buildings based on their sustainability and affordability.
District chiller- how does it work?
The chiller system is based on the principle of vapor absorption/compression. A coolant continuously flows to the cold side of the processing system at a temperature of 50 degrees Fahrenheit. While the coolant is pumped through the process, heat is extracted out of a machine/equipment and the coolant flows back to the process water system.
The refrigerant passes through 4 devices:
Evaporator- it performs the role of a heat exchanger. Here the coolant heat is passed on to the refrigerant. As this process takes place, the refrigerant changes its form from liquid to vapor. Meanwhile, the coolant reduces its temperature.
Compressor- In a district cooling chiller plant, a condenser performs dual functions. A compressor lowers the pressure in the evaporator so that it absorbs the heat correctly. It also increases the pressure in the refrigerant vapor so that a high temperature helps in releasing heat as it reaches the condenser.
Condenser- inside the condenser, the refrigerant changes back into a liquid, and the heat produced during the process is carried away through a cooling medium i.e. air or water.
Thus based on the cooling medium, two types of condensers are used- air-cooled and water-cooled. Air-cooled chillers use motorized blowers that force air across the grid lines of the refrigerant. On the other hand, a water chiller performs this process in 2 steps. First, heat is moved from the refrigerant vapor into the condenser water. Then, this water is pumped into the cooling tower that discharges the heat into the atmosphere. Let us explore the chilled water services in more detail.
Water chilled air conditioning- how it works?
Recirculating condenser water from a cooling tower is used in a water-cooled chiller to condense the refrigerant. Here the refrigerant depends on the temperature and flow rate of the condenser water. The temperature and the flow rate depending on the temperature of the wet bulb. Compared to a dry bulb, the temperature of the wet-bulb is usually lower. Because of this, the condensing temperature and pressure of the refrigerant are lower compared to the air-chilled conditioning system. Thus in most scenarios water chilled air conditioning works more efficiently reducing the district cooling costs per ton.
Water chillers are usually used for medium or large-size installations. Large facilities that have access to water supply like airports, malls, etc make use of water chillers. They have a long life span and are built indoors thus protecting them from other damages.
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