Bubble Behaviour in Three Phase Capillary Microreactors

Abstract

Two-phase flow characteristics in vertical capillary downflow were investigated in order to obtain understanding of the behaviour of three-phase monolith reactors. Experiments were conducted using air and dyed water in round and square capillary tubes of 2 mm and 3 mm diameter. The flow regimes and transitions observed were recorded using high speed videography and this data was used to produce flow maps for each tube. The gas and liquid superficial velocities used ranged from 0.001 to 10 m/s and 0.0001 to 1 m/s respectively. The flow regimes and their transitions were found to be a strong function of tube geometry and surface tension effects, and some differences were observed between capillaries of round and square section. This has significant implications for the design of microchannel reactors. Annular, slug-annular, slug, bubbly and churn flow regimes were observed in the round tubes; channelling/irregular flow was observed in the square tubes in place of annular and slug-annular flow.

Homogeneous Gas‐Liquid Distribution for Monolithic Structures via a Needle Distributor

“…10 a. The experimental results were approved comparing this finding with other flow regime maps for this channel geometry [21]. Even if there is no homogeneous distribution and the gas-to-liquid ratio varies in the channel, Taylor flow is present in those channels.…”

“…Multiple investigations of minichannels ascertained several characteristic flow regimes [9,[17][18][19][20][21][22]. Four of them were established to be typical for gas-liquid flows: bubbly flow, Taylor flow, churn flow, and film flow, occurring with increasing gas velocity.…”

Maldistribution susceptibility of monolith reactors: Case study of glucose hydrogenation performance

“…The gas superficial velocities were adjusted at , , and , while the liquid superficial velocity was maintained constant at . Considering the open frontal area of the monolith packing, the operating conditions were chosen that — according to the flow regime maps of Simmons et al developed for square channels of size and Venkatesan et al determined in circular channels with a diameter of — experiments were clearly allocated to the Taylor flow regime.…”

“…Taylor flow, which establishes within the channels of a monolith at low gas and liquid superficial velocities, is a surface tension dominated regime . Its boundaries in flow maps are mainly related either to superficial gas and liquid velocities or to gas and liquid Weber numbers . The reviews of Rebrov and Shao et al verify that Taylor flow develops also in comparably large channels for all fluid combinations if the gas superficial velocity is below .…”

Microchannel Reactors: Applications and Use in Process Development

“…The two phase flow characteristics of a gas-liquid mixture in vertical capillary microreactor were studied by Simmons et al, (2003) covering a rage of 0.001 to 10 m s -1 of gas flow and 0.0001 to 1 m s -1 of liquid flow. The capillary tubes were round (2 mm) and square (3 mm) in diameter and showed flow regimes and transitions as flow changes.…”