An Euler‐Euler model for gas‐liquid flows in a coil wound heat exchanger
Chapter, Conference object, Peer reviewed
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- SINTEF Proceedings 
Coil-wound heat exchangers (CWHE) are commonly adapted in process engineering for the efficient transfer of heat between fluids which feature wide temperature and pressure ranges. The field of application for this apparatus ranges from heating or cooling of single-phase flows, over the evaporation or condensation of fluids, to the utilization as isothermal reactor. Due to their large specific heat transfer area accompanied by a compact design, coil-wound heat exchangers are widely used in various process plants (e.g., LNG plants). Depending on the application, twophase flows may occur at both, the tube- as well as the shellside of the apparatus. For the design of a CWHE, the fluid and thermodynamic processes in the unit are commonly represented by a system of one-dimensional correlations. This approach implies uniform thermohydraulic conditions on horizontal cutting planes of the exchanger. Fluid and thermodynamic effects in the apparatus which result in radial parameter variations are inaccessible to these conventional design tools. To this end, a multidimensional CFD model has been established to enhance the representation of fluid and thermodynamic phenomena in CWHE design. The shellside of the CWHE and all tube-side sections are each numerically represented by separate domains which are coupled by source terms to account for the thermodynamic interaction between tube- and shell-side. In each flow region, the hydraulic effect of the tube bundle is modeled as a porous medium with corresponding fluid dynamic characteristics. The gas-liquid dynamics in each flow region is modeled based on an Euler-Euler approach. Unlike classical Euler-Euler models, local phase fractions and fluid properties are calculated from species relations as well as pressure and temperature fields. This model framework is augmented by locally evaluated correlations for pressure drop and heat transfer to account for apparatus internals and thermal coupling. The models for gas-liquid interaction forces are derived from standard correlations and augmented by findings from detailed CFD studies. Remaining parameters are specified by a parameterization study based on experimental findings.