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Chemical Papers

, Volume 73, Issue 5, pp 1173–1188 | Cite as

Effect of wall contact angle and carrier phase velocity on the flow physics of gas–liquid Taylor flows inside microchannels

  • S. V. B. Vivekanand
  • V. R. K. RajuEmail author
Original Paper
  • 49 Downloads

Abstract

This paper investigates numerically the characteristics of gas–liquid sliding Taylor flow in a two-dimensional (2D) T-junction rectangular microchannel having both inlets perpendicular to the horizontal mixing chamber. The governing equations describing the flow are discretized and solved by employing finite volume method based computational tool ANSYS Fluent 15.0. The volume of fluid (VOF) multiphase method is used for capturing the gas–liquid interface. A dynamic mesh, based on the adaption of gradients of volume fraction, is used for grid refinement to tackle sharp gradients during the two-phase flow. A focus is laid on exploring the influence of wall contact angle on the flow physics of sliding Taylor flows inside the microchannel in which the inlet liquid velocity is varied in the range 0.05 < uL < 0.25 m/s) (or inlet Reynolds number, 4.97 < Re < 248.75), and the wall contact angle is varied in the range 0° < Θo < 170°. The effect of contact angle hysteresis on the overall pressure drop, bubble and liquid slug lengths, and the dispersed phase volume fraction is reported. The bubble length and the overall pressure drop obtained from the simulations are compared with the benchmark correlations available in the literature. It is found that the trends of the variation of bubble length with liquid velocity are in reasonable match with the correlations. In addition, the pressure drop and slug length decrease in hydrophilic channels unlike in hydrophobic channels, which signifies the importance of contact angle in two-phase sliding Taylor flows.

Keywords

Microchannels Pressure drop Surface tension Taylor microbubble Two-phase flow Volume of fluids 

Symbols

a

Constant (−)

b

Constant (−)

C

Courant number (−)

Ca

Capillary number (−)

D

Hydraulic diameter (m)

f

Apparent friction factor (−)

h

Channel width (m)

k

Interface curvature (m−1)

L

Length (m)

Nu

Nusselt number (−)

Pe

Peclet number (−)

NUC

No. of unit cells (−)

R

Microchannel radius (m)

Re

Reynolds number (−)

Sα

Mass source term (kg/m3 s)

t

Time (s)

US

Slug velocity (m/s)

Ub

Bubble velocity (m/s)

UTP

Mixture velocity (m/s)

w

Relative velocity of bubble w.r.t slug (m/s)

ucell

Unit cell velocity (m/s)

We

Weber number

ΔP

Pressure drop (Pa)

Greek letters

α

Dispersed phase volume fraction

β

Homogeneous void fraction

δ

Film thickness (m)

Δxcell

Unit cell length (m)

λm

Roots of second-order Bessel function

ρ

Density (kg/m3)

µ

Dynamic viscosity (Pas)

σ

Surface tension coefficient (N/m)

Θ

Contact angle (°)

Subscripts

a

Advancing

b

Bubble

c

Continuous/carrier phase

C

Capillary

CA

Contact angle effect

d

Dispersed phase

G

Gas phase

H

Horizontal direction

i

ith phase

L

Liquid phase

MF

MOVING film

r

Receding

SF

Stagnant film

S

Liquid slug

TP

Two-phase

UC

Unit cell

V

Vertical direction

w

Wall

o

Static

Notes

Acknowledgements

The authors are grateful to the Ministry of Human Resource Development (MHRD), India, and National Institute of Technology, Warangal (India) for providing the necessary funds and computational facilities, respectively, to carry out the research work discussed in the present paper.

Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.

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Copyright information

© Institute of Chemistry, Slovak Academy of Sciences 2018

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringNational Institute of TechnologyWarangalIndia

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