EFFECT OF TAP SPACING ON OBSERVED DIFFERENTIAL PRESSURE-FLUCTUATIONS IN A PNEUMATIC TRANSPORT LINE

The standard deviation of differential pressure fluctuations between p ressure taps in a 31.7 mm i.d. vertical downer was found to be proport ional to the square root of the distance between the taps when measure d under otherwise constant conditions. This finding confirms the predi ction of a theoretical model based on the Central Limit Theorem of sam pling statistics. Although the paper only presents experimental confir mation for downward flow, the theoretical model should be valid for fl ows in all orientations. Except at very low solids flows, the pressure gradient was found to be positive in the flow direction, indicating t hat rise in pressure due to static pressure more than compensated for frictional pressure losses.