Feed throat cooling
Vol. 17 #4, Mar. 1991
Over cooling the hopper block can have a negative effect on extruder performance, due to its heat sink effect that pulls most of the heat from the feed zone of the barrel. The idea of hopper block cooling is primarily to prevent sticking or bridging in that area, and it should not be run colder than necessary to accomplish that requirement.
See also
Liquid in feed
Throat cooling