- a fire-tube boiler having flues that collect the combustion gases at the end of the boiler opposite the fire door and pass them through the boiler to an uptake above the fire door.
Origin of return-flue boiler
First recorded in 1885–90
Also called re·turn-tu·bu·lar boil·er [ri-turn-too-byuh-ler, -tyoo-] /rɪˈtɜrnˈtu byə lər, -ˈtyu-/.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018