Pressure Distributions in Manifolds with Return Ducts

Abstract

Longitudinal static pressure distributions in air flow have been measured in manifolds with untapered inlet and outlet ducts, closed at one end and interconnected by a large number of identical ports. The transfer of air through these ports causes the static pressure to rise towards the closed end of the inlet duct, although friction reduces this rise to about 50 per cent of its ideal value. For very long ducts the pressure initially decreases near the inlet end. In the outlet duct the ideal drop in pressure from the closed end is increased by about 15 per cent. Theoretical distributions in good agreement with measurements are obtained assuming constant values for the frictional losses for each configuration and meaningful predictions may be made at the design stage since pressure distributions are found to be relatively insensitive to these values.