A chiller is a cooling system that removes heat from a liquid (typically water) to provide reliable temperature control for buildings and industrial processes. Whether you’re in a comfortable office building or enjoying a cold beverage, chillers likely play a critical role behind the scenes.

How Chillers Work: The Cooling Process

Chillers operate using a refrigeration cycle that transfers heat from one place to another. In simple terms, they absorb heat from water and reject it elsewhere. The cooling process follows these key steps:

  1. Warm water enters the evaporator from the building or process
  2. Inside the evaporator, heat transfers from the water to a refrigerant
  3. The refrigerant evaporates as it absorbs this heat
  4. The compressor pressurizes the refrigerant gas, raising its temperature
  5. The hot refrigerant moves to the condenser where it releases heat
  6. The refrigerant condenses back to liquid form
  7. An expansion device reduces the refrigerant’s pressure
  8. The cycle repeats continuously.

This continuous cycle keeps removing heat from your building or equipment, maintaining optimal temperatures.

Key Components of a Chiller System

As shown in the diagram, a water-cooled chiller system consists of:

  • Chiller Unit: The main cooling equipment containing the refrigeration components
  • Chilled Water Pump: Circulates cooled water to the building
  • Condenser Water Pump: Moves water between the condenser and cooling tower
  • Cooling Tower: Releases heat from the system to the outside air
  • Condenser Water Loop: Carries heat away from the chiller
  • Chilled Water Loop: Delivers cooled water to air handlers in the building.

Types of Chillers

The chiller can be water-cooled, air-cooled, or evaporatively cooled:

  • Water-cooled chillers use cooling towers to reject heat and are more efficient but require water treatment
  • Air-cooled chillers reject heat directly to the surrounding air, requiring no water treatment but typically consuming more energy
  • Evaporatively cooled chillers combine features of both types

Compressor Types

Chillers use one of four main compressor types:

  • Reciprocating compressors: Suitable for smaller systems and peak loads
  • Scroll compressors: Efficient for medium-sized applications
  • Screw compressors: Can handle high compression ratios efficiently
  • Centrifugal compressors: Most efficient at peak loads for larger applications