PhD Thesis in Safety Modelling | Experimental Safety

SAfe relief of Multi-Component Flashing Two-Phase-Flow

Phenomenological and experimental investigation of multi-component flashing two-phase flow

In the chemical and petrochemical industry as well as in the oil and gas industry, vessels, fittings and equipment of many production processes are based on mixtures of components and multi-phase streams. Representative examples are not only the blowdown of pressurized systems during the discharge through safety relief valves and rupture discs but also leaks and ruptures of pipelines and reactors or the flow through control valves and orifices. Herein, besides the sudden flash of the multiphase mixture, the fluid may be choked at the outlet, arising the phenomenon of critical flow.

Often multi-component flashing flows are modelled as single-component fluid streams with averaged thermodynamic properties under equilibrium conditions. Metastable conditions, thermodynamic non-equilibrium phenomena (boiling delay), mechanical non-equilibrium states (slip) and non-equilibrium mass are neglected for simplicity. Experimental data are lacking. Hence, current simplified methods are often not validated and/or highly uncertain when predicting multi-component multi-phase flow through industrial devices. For multicomponent flashing two-phase critical flow through throttling devices like nozzles, orifices or valves there is neither a standardized test section, nor any reliable test results are available. Consequently, there is no precise model to size these devices in such flow conditions and often safety factors are added in the calculation which results in largely oversized devices.

The CSE Center of Safety Excellence has collected more than 20 years experience in gasl/liquid two-phase flashing flow experiments and modelling. Several paper have
been published during the last decade. The latest HNE-CSE model (homogeneous non-equilibrium model based on a continuous set of sizing equations) defines the current Industrial Standard for sizing safety devices in accordance with ISO 4126-10. Nevertheless, non of the existing methods have been validated against experimental data for multi-component flashing flow.

SAM-Flash, a research programme at the CSE Institute in cooperation with Institutes and Industry, seeks to shed more light on the field of multicomponent flashing two-phase flow. Based on the measurement techniques for two-phase single component flashing flow, a test facility for two-phase multicomponent industrial mixtures will be developed. The core aim of the project is to investigate the recurring thermodynamic and mechanical non-equilibrium phenomena i.e boiling delay and phase-slip, in flashing multicomponent mixtures through nozzles under critical flow conditions, which have direct relevance for industry throttling devices applications.

The deeper understanding of the flow phenomena may then enhance and harmonize
the existing modelling techniques in order to predict more accurately the flow through
these types of industrial devices and enable more precise discharge and dispersion

Project-Data SAM-Flash

PhD-Project in the scope of the CSE Research Areas: Safety Modelling | Experimental Safety
Beginn Juni 2017 / Project Duration 4 Years

Prof. Dr.-Ing. Jürgen Schmidt

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