Plasma Intercooler
The Plasma Intercooler is a starship system used to provide Plasma Coolant to the Warp Drive and other critical systems.
A failure of a plasma intercooler will cause the warp drive to overheat or possibly fail to work altogether. (TNG: "Relics")
It is suspected that the Plasma Intercooler serves the same function as the Pre-Stage Flux Chiller and the Main Stage Flux chiller found on the Constitution Class starship. It is uncelar if there is more then one Plasma Intercooler aboard the galaxy class Starship. it is possible that advances in Warp Drive design may have made it unnecessary to have more than one of this device on the ship.
Chief Miles O'Brien took the safeties of the USS Defiant's plasma intercooler offline and never had any problems. Ensign Nog did the same on the USS Valiant in 2374. (DS9: "Valiant")