Parts of a Chiller – Labeled Diagram of a Water Chiller

All 15 parts on the diagram

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Refrigerant side 7

Compressor It raises the pressure of the vapor, and so its temperature. Chillers are classed by compressor type: reciprocating, centrifugal or screw.
Motor On a hermetic chiller the motor is sealed in with the compressor.
Condenser The refrigerant condenses on tubes of cooling water. It gives up its heat to that water.
Evaporator (cooler) Liquid refrigerant flows over the tube bundle and evaporates. That takes heat from the chilled water inside the tubes. Some makers call it the cooler.
Tube bundle Refrigerant is on the outside of the tubes and water inside. That way heat passes through the tube walls.
Expansion valve It drops the pressure of the liquid refrigerant, and so its temperature. Both fall to that of the evaporator.
Relief valve One of the places where a chiller is checked for leaks.

Water side and controls 6

Water boxes The water pipes join the barrel here. The covers come off to reach the tubes for cleaning.
Control panel It starts and stops the machine and shows faults. It also holds the chilled water at the set temperature.
Chilled water pump The water goes to the cooling coils and comes back warmer. It is then chilled again.
Air handler Chilled water runs through the coil. The fan blows air over it. The water goes back to the chiller for recooling.
Condenser water pump This second water loop carries away heat. The chiller took that heat out of the chilled water.
Cooling tower In a spray-filled tower the water falls like rain. Meanwhile a fan draws air up through it.

Air-cooled chiller 2

Condenser coil The refrigerant runs in copper tubes. The air passes over aluminum fins.
Condenser fans They take the place of the cooling tower and its water loop.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it or describe the part: Wikipedia, Chiller (text only); the US Department of Energy O&M Best Practices Guide, Release 3.0, sections 9.4 and 9.5 (https://www.energy.gov/sites/prod/files/2013/10/f3/omguide_complete.pdf, read from the Internet Archive copy); three chiller makers' manuals read as full text on archive.org (https://archive.org/details/manualsbase-id-589112, https://archive.org/details/manualsbase-id-570535, https://archive.org/details/manualzilla-id-5718032); a US Air Force course text (https://archive.org/details/ERIC_ED183832). No maker is named on the page. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; a schematic of no maker's product, nothing traced. Licence: own work

How it works

A chiller is a refrigeration machine that cools water, and the chilled water then cools a building or a process. The drawing shows a water-cooled chiller, the plant round it, and an air-cooled chiller.

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Four parts make the cycle

The refrigerant goes round four parts. In the evaporator it takes heat from the chilled water. The compressor pumps the vapor to the condenser, where it gives that heat to the cooling water. The expansion valve drops its pressure on the way back to the evaporator. Numbers 1 to 9 are on the chiller. Numbers 10 to 13 are the plant: two pumps, the air handler and the cooling tower. Numbers 14 and 15 are on an air-cooled chiller.

Two water loops meet at a chiller: chilled water through the evaporator, condenser water through the condenser. The two never mix.
An air-cooled chiller has no cooling tower: condenser coils and fans give the heat straight to the air.

Questions and answers

What are the main parts of a chiller?

Four: the evaporator, the compressor, the condenser and the expansion valve. The refrigerant goes round them in that order. On a water-cooled chiller the evaporator and the condenser are long barrels with a bundle of tubes inside and a water box on each end.

What does the evaporator do in a chiller?

It is where the water is chilled. Liquid refrigerant flows over the tube bundle and evaporates, taking heat from the chilled water that runs through the tubes. Some makers call the evaporator the cooler.

What is the difference between an air-cooled and a water-cooled chiller?

How the condenser gets rid of heat. A water-cooled chiller gives the heat to a loop of condenser water, which a cooling tower then cools. An air-cooled chiller has condenser coils and fans and gives the heat straight to the outdoor air.

What does a cooling tower do for a chiller?

It cools the condenser water. The water that took heat from the condenser is brought into direct contact with outdoor air in the tower, then pumped back to the condenser.