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Flow regimes and pressure histories during blowdown from a vertical tube Steeves, Alan


A series of blowdown experiments have been performed while discharging either vertically (upwards or downwards) or horizontally in order to compare the effect of body force on transient flow patterns and pressure histories. Tests were done using Freon-114 in a clear polycarbonate pipe 4 m long with a 32 mm I.D. Results, presented in the form of flow regime maps, show that the basic nature of the developing flow in a vertical pipe when discharging upward is different than for the downward discharge case. Both cases are in turn markedly different than for horizontal discharge. Pressure histories were found to fall into two categories: one in which the pressure fell rapidly to near the saturation pressure, then slowly to atmospheric; a second in which transient repressurization to nearly the initial pressure was observed following the initial pressure drop. The second category occurred only in the vertical pipe and could not be satisfactorily explained. Rapid changes in axial pressure gradient, and possible flow reversal, were noted in the repressurization case.

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