Plasma intercooler

From Memory Alpha, the free Star Trek reference.

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")

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")

Though never stated in canon, "plasma intercooler" may be the proper name of the "intercooler" mentioned in Star Trek: The Motion Picture.