Qualification of CFD-models for multiphase flows in medium and large scale industrial applications


Qualification of CFD-models for multiphase flows in medium and large scale industrial applications

Lucas, D.

Multiphase flows are frequently applied in industrial processes as e.g. in chemical engineering, oil industries or power plants. Reliable predictions of the flow characteristics such as local concentration of species, interfacial area density or heat transfer in gas-liquid flows can contribute to an optimization of the design of corresponding apparatuses and processes. Computational Fluid Dynamics (CFD) in principle allows the simulation of such flows and provides local flow characteristics. While it is frequently used for industrial problems in case of single phase flows it is not yet mature for two-phase flows. The reason is the complex gas-liquid interface. For medium and large scale flow domains it is not feasible to resolve all details of this interface. Averaging procedures have to be applied and in most cases the so-called two- or multi-fluid approach is used. It assumes interpenetrating phases and the information on the interface gets lost by these averaging procedures. This information has to be added to the basic balance equations by so-called closure models. The development and validation of such models is done at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) to obtain tools for reliable predictions of multiphase flow characteristics in medium and large industrial scales.
One difficulty for the model development and validation results from the fact that we still have a lack of knowledge on local phenomena which determine the two-phase flow characteristics and which should be considered in the closure models. Experimental data with high resolution in space and time are required. To get such information on the gas-liquid interface new innovative measuring techniques as wire-mesh sensors and ultrafast X-ray tomography were developed at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) and extensively used to establish comprehensive databases. The corresponding experiments were conducted at the TOPFLOW-facility of HZDR. It can be operated for air-water and steam-water flows with a pressure up to 7 MPa and the corresponding saturation temperature of 286 °C. An electrical steam generator with a power of 4 MW is able provide up to 1.5 kg steam per second.
In this lecture the strategy of the CFD-model development and validation for multiphase flows is presented. This includes the corresponding experimental work and development of innovative measuring techniques.

Keywords: CFD; two-phase flow; TOPFLOW

  • Invited lecture (Conferences)
    Lecture series of the Energy Department of Politecnico die Milano, 15.06.2016, Milano, Italy

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Publ.-Id: 23853