a procession (of wagons or mules or camels) traveling together in single file; "we were part of a caravan of almost a thousand camels"; "they joined the wagon train for safety"
a mechanism consisting of a metal honeycomb through which hot fluids circulate; heat is transferred from the fluid through the honeycomb to the airstream that is created either by the motion of the vehicle or by a fan
heater consisting of a series of pipes for circulating steam or hot water to heat rooms or buildings