Time varying behavior of cocurrent gas-liquid flows in packed beds

Properties of pulsing flow in a trickle bed

“…The opposite trend is observed at high liquid flow rates where gas velocities tend to spread the data, but their influence is weaker in comparison with that of the liquid flow rates. The spreading with increased gas flow rate is also observed in histograms of the distribution of time intervals between the pulses, reported by Helwick et al (1992). In data of the average liquid-rich length (not presented here due to space limitations) different trends are evident for mild and wild pulsing.…”

Flow Regime Transitions in Trickle‐bed Reactors with Structured Packings

“…These periodic components are no longer observed for higher liquid velocities. This behavior is very different from the one found for a conventional TBR with random packing, where the pulsing flow is clearly identified from the appearance of pulses at regular intervals, which increase their frequency as the fluid velocities are increased (Helwick et al, 1992;Krieg et al, 1995;Horowitz et al, 1997).…”

“…For example, Frank et al (1999) did not observe a trickling-pulsing flow transition in a TBR packed with SPs for the same conditions where they did observe a change in the conventional TBR. In the last decade, many articles have put in evidence that features of time series of characteristic variables, mainly pressure fluctuations, measured in different multiphase reactors constitute robust objective tools capable of diagnosing sharp variations in the underlying dynamics as those found in flow regime transitions (Helwick et al, 1992;Krieg et al, 1995;Horowitz et al, 1997;Letzel et al, 1997;Daw et al, 1998;van Ommen et al, 2000;Johnsson et al, 2000).…”

Origin of disturbances in cocurrent gas‐liquid packed bed flows

“…A Fischer-Porter rotameter was used to measure the liquid flow rate. More details on the supply systems are available in theses by Helwick (1991), Dillon (19921, and Krieg (1994).…”

“…The vertical, cylindrical column (Helwick et al, 1992) is 1.3 m in length, 1.27 cm in wall thickness, 7.62-cm ID and filled with 0.318-cm nonporous, polished spheres to a packing height of 1.25 m. On top of the packing is a highly porous section of foam, approximately 2.5 cm high, followed by a fine screen acting as a precursor to the packing to ensure uniform distribution of liquid. The entrance section, which sits directly on top of the mesh, is a 10-cm-high monolith "honeycomb" that is designed to have 1/3 of its holes (0.35 cm dia.)…”