CFD Simulation of Two-Phase Flows in Helical Coils

Abstract

The behavior of two-phase flow and corresponding flow regimes in helical tubes significantly differ when compared to two-phase flows in straight tubes due to centrifugal and torsion effects. In order to gain physical insight and gather data for validating computational models, a large number of experiments were performed on a helical coil experimental setup operated with a mixture of water and air. The experimental data were used to assess the predictive capabilities of current two-phase Computational Fluid Dynamics (CFD) models based on the Volume of Fluid (VOF) approach. In the present paper, a comparison of the CFD simulation results with the high-resolution experimental data is discussed, with special emphasis on two-phase pressure drops and void fraction distributions. It is shown that the CFD VOF model is able to correctly capture the occurrence of five flow regimes observed in the experiments, namely bubbly flow, plug flow, slug flow, slug-annular flow, and annular flow. However, a good quantitative agreement for pressure drops and void fraction distributions is found in slug flow and slug-annular flow regimes only. The good agreement found only in a limited range of flow regimes demonstrates that there is not a single set of best-practice guidelines for CFD VOF models that can be applied across a wide range of two-phase flow regimes. Also, there is not a single mesh that can be used to simulate all of the flow regimes and a case-specific mesh and time-step convergence study is needed for each individual flow regime. In the current study, optimal mesh size and time step were obtained for a slug flow test case. Hence, good agreement was obtained only for similar flow regimes, leading to significant disagreement with experimental data for test cases with substantially different flow patterns.

Method of electric vehicle braking energy recovery

“…Professor N.V. Gulia have developed the super-flywheel device and is working on the creation of a supervariator mechanism -a wide-range flywheel drive. An important factor is the ability to save and reuse braking energy [5,6]. Engineers have long tried to preserve the kinetic energy of motion during braking in order to reuse it.…”

Performance Optimization of the Helical Heat Exchanger With Turbulator

“…The process of transferring the heat (Ghalandari et al, 2019;Zhao et al, 2021a, Zhao et al, 2021b between two fluids at different temperatures separated by a solid wall is common in many engineering applications (Che et al, 2021;Mahariq and Erciyas, 2017;Mahariq et al, 2020;Panahi and Zamzamian, 2017;Prabhanjan et al, 2002;Shafee et al, 2020;Zhao et al, 2021c). Heat exchangers are devices that allow heat to be transferred from one fluid to another without mixing the two fluids (Assad et al, 2021;Che et al, 2021;Chu et al, 2020;She and Fan, 2018;Zhou et al, 2020).…”

“…The process of transferring the heat (Ghalandari et al, 2019;Zhao et al, 2021a, Zhao et al, 2021b between two fluids at different temperatures separated by a solid wall is common in many engineering applications (Che et al, 2021;Mahariq and Erciyas, 2017;Mahariq et al, 2020;Panahi and Zamzamian, 2017;Prabhanjan et al, 2002;Shafee et al, 2020;Zhao et al, 2021c). Heat exchangers are devices that allow heat to be transferred from one fluid to another without mixing the two fluids (Assad et al, 2021;Che et al, 2021;Chu et al, 2020;She and Fan, 2018;Zhou et al, 2020). Significant issues such as savings in materials, space, energy, and the global economy have led to the development of more efficient heat exchanger equipment and reductions in costs (Ghalandari et al, 2020;Irandoost Shahrestani et al, 2020;Shadloo et al, 2016;Zhao et al, 2020a).…”

Steady-state thermal hydraulic modelling and turbine trip transient simulation of the NuScale integral pressurised water reactor using the ASTEC code

“…Numerous studies have been performed, ranging from overall steady-state and transient characteristics using system codes (Yan et al, 2016;Skolik et al, 2021) to specific phenomena related to natural circulation, helical SG coils, boiling instabilities etc. with CFD methods (Che et al, 2020), and combinations of these (Hoffer et al, 2011;Kim et al, 2020).…”