Abstract:

The commercial-scale slurry bubble column reactors are generally equipped with bundles of vertical heat-exchange pipes.Experimental results showed that existence of the pipe bundles led to steepening of liquid velocity and gas holdup distributions, the so-called “funneling effect”.At present, there is still lack of reliable CFD models which quantitatively describe the impact of vertical pipe bundles.In this work, a novel hydrodynamic model was developed, with two new ideas.The influence of pipe bundles was regarded as volumetric sources instead of rigid wall boundaries, thus actions of internals on the flow were transformed to additional constitutive equations for momentum source, turbulent energy source and energy dissipation source in standard k-ε equations.For the determination of radial gas holdup profiles, the lateral lift force and turbulent dispersion force imposed on bubble swarms were introduced into the radial momentum balance equation.The new introduced pipe resistance coefficients in the CFD model came from literatures, only two parameters involving radial force and turbulent energy dissipation were determined by fitting experimental data.Radial profiles of gas holdup and liquid velocity predicted by the CFD model showed good agreements with experimental data.The model presented in this paper provides an effective tool for simulating the “funnel effect” and impacts of the pipe bundles on bubbly flow.