downcomer

noun

Definition of downcomer

: a pipe to conduct something downward: such as
a : a pipe for leading the hot gases from the top of a blast furnace downward to the dust collectors and flue system
b : a tube larger in diameter than the water tubes in some watertube boilers to conduct water from each top drum to a bottom drum under the influence of thermal circulation

History and Etymology for downcomer

down entry 2 + comer

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