Duct units for delivery of air to an air supply fan and for connecting this
fan to an air heater unit are disclosed. The duct unit for delivering air in one
version has a narrow first section, a second, transition-type section and a wide
sound attenuating, third section with these three sections extending generally
vertically. Spaced apart splitters containing sound attenuating material and having
side walls of perforated metal are mounted in the third section. The splitters
include a central splitter and outer splitters with the latter converging inwardly
towards a central axis of the third section. This duct unit also has an elbow-shaped
duct section connected to the third section at its upstream end and connectible
to the fan at its downstream end. In another version, the duct unit has a single,
elongate splitter that extends longitudinally along at least a major portion of
a second duct section and that bends through a smooth curve. The outlet duct apparatus
has an elbow section of duct that bends through a smooth curve and an elongate
second section connected to the elbow section. An elongate turning vane is mounted
in the outlet duct and has a substantially curved first vane section and a second
vane section that extends substantially upwardly.
