Scotch boiler
chiefly North American (now frequently historical )
noun
A steam boiler having a cylindrical shell with one or more furnaces inside the lower part of it, the hot gases produced from combustion passing through tubes in the upper part, typically used to power steamships; more fully Scotch marine boiler.
Origin
Late 19th century; earliest use found in Journal of the Franklin Institute. Apparently so called because it was developed in Scotland and exported by Scottish firms.