Effect of Inlet Conditions on Taylor Bubble Length in Microchannels

Abstract

The effect of inlet conditions on the frequency and size of the bubbles that form during gas–liquid Taylor flow in microchannels is investigated in this paper. Three different inlet configurations, T-, Y-, and M- junction, and three test channels with hydraulic diameters 0.345 mm, 0.577 mm, and 0.816 mm were used. The test fluids were nitrogen and water or octane, which have different surface tensions. It was found that bubble length increased with increasing gas flow rate, gas inlet size, and liquid surface tension and with decreasing liquid flow rate. From the different inlet configurations, the M-junction resulted in the largest bubbles and the Y-junction in the smallest ones, particularly at low liquid flow rates. Bubble lengths calculated from experimental bubble formation frequencies were tested against a number of literature correlations but the agreement was not very good. Two new correlations were developed for the T- and the Y-junctions to calculate the unit cell (one bubble and one slug) frequency, from which the bubble length can be found. Bubble lengths predicted from these correlations were in good agreement with experimental ones obtained from video recordings.

Acknowledgments

Nan Shao is a Ph.D. candidate in the Department of Chemical Engineering at University College London. She obtained her M.Sc. from the same university in 2004 and a B.Eng. in chemical engineering from Dalian University of Technology, China, in 2003. She has carried out studies on gas–liquid systems in microchannels, She has published three papers in this field.

Asterios Gavriilidis is a professor in the Department of Chemical Engineering at University College London. He obtained a diploma from the University of Thessaloniki (1988) and an M.Sc. (1990) and Ph.D. (1993) from the University of Notre Dame, USA, all in chemical engineering. He has carried out research in chemical and catalytic reaction engineering. He is subject editor of Chemical Engineering Research and Design, a fellow of the IChemE, and UK representative in the EFChE.

Panagiota Angeli is a reader in the Department of Chemical Engineering at University College London. She received her diploma in chemical engineering from the National Technical University of Athens (1990), and her Ph.D. from Imperial College, London (1996). Her research is on the experimental and theoretical studies of two-phase flows. She is a fellow of the IChemE and a member of the Technical Chamber of Greece.