What Is a Chiller?

What Is a Chiller?

In HVAC, a chiller is a critical component of commercial systems designed to cool large buildings by lowering the temperature of a liquid, typically water. The liquid is then circulated throughout the building through a piping system to air handling units (AHUs) that cool the air. Chillers are essential for maintaining comfortable environments in various commercial and industrial settings, including hotels, hospitals, schools, data centers, and manufacturing plants.

How Does a Chiller Work?

Chillers operate on the principle of vapor compression or vapor absorption. Here's how the typical vapor compression chiller works:

• Heat is transferred to the refrigerant: In the evaporator, heat is transferred from the water (building loop) to the refrigerant.
• Refrigerant becomes a hot gas: The refrigerant is converted into a hot, high-pressure gas when a compressor pressurizes the refrigerant, raising its temperature.
• Gas cools back to liquid: In the condenser, the refrigerant transfers its heat to the outside environment (either to air or water) and condenses back into a liquid. Air-cooled chillers use fans to blow air over the condenser, while water-cooled chillers transfer heat to a water loop where heat can then be rejected via a cooling tower or dry cooler, or alternatively, some or all of the heat could be reused in a heat recovery system.
• Pressure reduction: The liquid refrigerant passes through an expansion device, which reduces its pressure and temperature.
• Cycle restarts: The lower-pressure refrigerant returns to the evaporator to repeat the cycle.

The three types of compressors used in Trane chillers are centrifugal, helical rotary, and scroll. Each compressor type offers distinct advantages in terms of efficiency, capacity, maintenance requirements, and cost-effectiveness, depending on the facility's specific cooling needs.

Types of Chillers

There are two main types of chillers—air-cooled and water-cooled—and each has its own process and considerations.

Air-Cooled Chillers

The process: Air-cooled chillers use fans to blow air over the condenser coils, releasing heat into the atmosphere.

Considerations when determining specifications for air-cooled chillers:

• Generally less expensive to install and maintain than water-cooled chillers.
• Do not require a cooling tower or a constant water supply, making them suitable for areas with limited water availability.
• Maintenance is easier.
• Modular solutions are available for facilities with space constraints.
• Less energy-efficient than water-cooled chillers.
• Hot weather can reduce performance.
• The cooling fans can be noisy.
• Compared to water-cooled chillers, the lifespan may be shorter.

Commonly used for: Small office buildings, data centers, educational institutions, and factories with lower cooling demands, as well as temporary emergency cooling for rental service fleets. Air-cooled chillers are also suitable for process applications, ice making for thermal energy storage, and low-temperature applications, such as ice rinks.

Water-Cooled Chillers

The process: Water-cooled chillers transfer heat from the refrigerant to water, which is then pumped to a cooling tower to release the heat into the air.

Considerations when determining specifications for water-cooled chillers:

• More energy-efficient than air-cooled chillers.
• Well-suited for applications with high cooling demands.
• Quieter operation than air-cooled chillers.
• When properly maintained, water-cooled chillers can have a longer lifespan.
• Water-cooled systems can be more expensive to install due to the need for a secondary water loop containing pumps, valves, tanks and a cooling tower.
• Maintenance of the condenser water loop could also add yearly cost.

Commonly used for: Large commercial buildings, industrial applications, and facilities with significant cooling needs, such as data centers, hospitals, and large manufacturing facilities.

Resources for Chillers

• Air-Cooled vs. Water-Cooled Chillers: Which is Best for Data Centers?
• Case Study: Golden Properties Achieves 73% Energy Savings with Trane’s Chiller Plant Redesign
• For additional case studies, read our Customer Stories.

When selecting a chiller, consider factors such as cooling capacity, energy efficiency, noise levels, maintenance requirements, and budget. Consulting with Trane Commercial HVAC professionals can help determine the most suitable chiller for your organization's specific needs.