steam-header

from The Century Dictionary.

• noun A pipe, cylinder, or other tubular chamber with a number of side-outlets from which a series of pipes may be supplied with steam, as from a common supply: used in the construction of sectional boilers of water-tube design, in which a number of generating tubular units deliver steam into a chamber transverse to them; also in supplying steam to a number of pipes in a radiator coil used in steam-heating.