Slot Fan Cooler

fan cooler
(Fan Cooled) A method of forced-air cooling used to maintain design temperatures.
(Fan Cooled) A means of accelerating heat dissipation to lower the temperature rise of the transformer. This has the effect of increasing the transformer rating.

slot
A long, narrow aperture or slit in a machine for something to be inserted
assign a time slot; "slot a television program"
An allotted place in an arrangement or plan such as a broadcasting schedule
a position in a grammatical linguistic construction in which a variety of alternative units are interchangeable; "he developed a version of slot grammar"
a small slit (as for inserting a coin or depositing mail); "he put a quarter in the slot"
A groove or channel into which something fits or in which something works, such as one in the head of a screw