Hydrodynamics analysis of Taylor flow in oil and gas pipelines under constant heat flux
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ORIGINAL
Hydrodynamics analysis of Taylor flow in oil and gas pipelines under constant heat flux Sidique Gawusu 1
&
Xiaobing Zhang 1
Received: 5 May 2020 / Accepted: 15 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This is an incompressible numerical study of the hydrodynamics and heat transfer characteristics of Taylor flow in vertical oil and gas pipelines under constant heat flux using the Volume-of-fluid (VOF) method in ANSYS Fluent, covering a wide range of Re(0.22 ≤ Re ≤ 800) and Ca(0.0075 ≤ Ca ≤ 0.35). Nusselt number (Nu) correlations were used to examine the heat transfer characteristics based on a set of flow parameters. A comparison of the predictions of the void fraction, average velocity, pressure drop and the mean Nusselt number was made with available experimental observations, with most of the experimental data falling within 15.540% of the current study. The bubble increases in length with increasing capillary number and the wall of the tube at the confines of the gas phase leads to asymmetric and axisymmetric bubbles at low and high capillary numbers respectively. The transition region between the edge of the bubble and the film thickness increases with an equivalent increase in Ca and more evident at high Re. The study revealed that, Taylor flow plays a more significant role on the pressure drop increase and, provided the mechanisms and theoretical guidance for heat transfer characteristics in oil and gas pipelines. Keywords Pressure drop . Taylor flow . Heat transfer . Homogeneous void fraction . Slug flow . Mixture velocity
Notation a constant cp specific heat capacity, Jkg−1K−1 Ca Capillary number, μLUTP/σ D diameter of the column, m Eo Eotvos number, g(ρL −p ρGffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi )D2/σ Fr Froude number, U TB = gDðρL −ρG Þ =ρL g acceleration due to gravity, m/s2 G gas phase k Thermal conductivity, Wm−1K−1 k the kth phase fluid κ Interface curvature L liquid phase Ls liquid slug length Luc unit cell length, m M Morton number MRF Moving Frame of Reference Nu Nusselt number, hD/k
* Xiaobing Zhang [email protected] 1
School of Energy and Power Engineering, Nanjing University of Science & Technology, Nanjing, China
Nuav Nux Nu* NuLO NuTP q qav R ReTP Re H Tb, av T W ,
mean Nusselt number local Nusselt number normalized Nusselt number, NuTP/NuLO fully developed liquid-only Nusselt number for constant heat flux conditions. two-phase Nusselt number,hTP/kL heat flux, Wm−2 average heat flux,Wm−2 bubble radius, m two-phase (liquid only Reynolds number), UTPρLd/μL Reynolds number specific enthalpy, J/kg average bulk Temperature, K average Temperature, K
av
UTP UTB UL UWall ux υ νx
mixture velocity, m/s Taylor bubble velocity, m/s liquid superficial velocity, m/s velocity of the moving wall, m/s axial velocity,m/s velocity vector, m/s radial velocity, m/s
Greek numbers σ surface tension, N/m
Heat Mass Transfer
ρG gas density, kg/m3 ρL liquid density, kg/m3 μG gas viscosity, Pa s μL liquid viscosity, Pa s αG volume fraction of the gas phase αL vo
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