Refrigeration – Chiller Theory

Centrifugal chillers are used in medium- and large-sized buildings to provide comfort cooling. Many of them use the vapor compression refrigeration cycle to produce chilled water that is pumped to AHUs and FCUs located in various spaces around the building. Afterwards, the chilled water returns to the chiller unit, where it is re-cooled, and the process is repeated. Chiller systems are sized to handle the amount of heat that is generated inside a facility. However, cooling loads vary during the day as well as seasonally, and they can change over time as facility uses change. This can make chiller sizing challenging. An undersized system will not be able to be keep up and water temperatures will fluctuate, while an oversized system will cost more initially and not run efficiently. This course defines several chiller performance parameters, including capacity, delta T, and several efficiency factors, and it explains why they are important. It also lists items that should be checked during startups and capacity modulation techniques used during normal operations to ensure the safe efficient operation of chiller systems.