Which device uses water as a cooling agent to lower air temperature and increase density before entering the combustion chamber?

• A. Air Cleaner
• B. Air Silencer
• C. Aftercooler
• D. Intercooler

Answer: (C)

Cooling the air after it’s been compressed makes it denser, so more oxygen enters the combustion chamber and the engine can produce more power. The device that accomplishes this by using water as the cooling medium and sits right before the intake to the combustion chamber is the aftercooler. It acts as a heat exchanger, removing heat from the compressed air so its density increases before it mixes with fuel for combustion.

The other items aren’t doing this cooling function. An air cleaner filters out dirt and debris, not temperature. An air silencer reduces intake noise, not density. An intercooler also cools compressed air, but it’s typically described as cooling between compression stages (and isn’t specified here as the water-cooled, pre-combustion cooling device).