Air-Cooled Chilled Water Plant
Understand how the air-cooled chilled water plant works. Explore system overviews, measurements, and additional resources.
Overview
An air-cooled chilled water plant consists of an air-cooled chiller system and a chilled water loop system operating to meet the cooling demand in a facility. The air-cooled chiller produces chilled water through the basic refrigeration cycle. The primary chilled water pump circulates the chilled water between the chiller and the chilled water loop. In some cases, a secondary chilled water pump distributes the chilled water produced by the chiller to air handling units (AHUs) in the building.
Systems
Air Cooled Chiller
An air-cooled chiller provides chilled water to the chilled water loop system and components
Chilled Water Loop
A chilled water loop system consists of a closed loop distribution system that supplies chilled water to the building and includes components.
How do I…
Assess Plant Energy Usage
The primary energy consumption of an air-cooled chilled water plant comes from the chiller package, which incorporates the compressor and condenser in a single unit. The chilled water pumps are also large and consistent users of energy within the plant.
Quantify Electricity Usage (kWh)
Determine the total amount of electricity used to operate the chillers and pumps in the plant.
Equipment to Measure
What to Measure:
- Average hourly true RMS power draw (kW) of the chiller package
What to Measure:
- Average hourly true RMS power draw (kW) of the chilled water pumps
Measurement Locations
Assess Plant Performance
The thermal energy rejected from the building to the outdoors can also be measured to evaluate the overall performance of the plant, usually in kilowatts of power consumed per ton of cooling provided (kW/ton).
Quantify Evaporator Thermal Load (Btu)
Determine the cooling load on building / heat rejected to the outdoors.
Equipment to Measure
What to Measure:
- Average hourly flow rate (gpm) of chilled water in the loop
- Average hourly temperature (°F) of chilled water supply
- Average hourly temperature (°F) of chilled water return
Measurement Locations
Further Reading
ASHRAE (2020). 2020 ASHRAE Handbook: HVAC Systems and Equipment. Atlanta, GA: ASHRAE.
Gordon, J.M.; Ng, K.C. (2000). Cool thermodynamics: The engineering and physics of predictive, diagnostic and optimization methods for cooling systems. Cambridge International Science Publishing; pp. 159-177.
Wei, J.; Reddy, T.A. (2003). “Reevaluation of the Gordon-Ng Performance Models for Water-Cooled Chillers.” ASHRAE Transactions, Vol. 109, Part 2. Atlanta, GA: American Society of Heating, Refrigerating and Air Conditioning Engineers.