Library

2765 match your search

A time dependence of three-dimensional simulation including water phase change and heat transfer of a PEMFC model has been studied. The overshoot behavior has been observed during a change in the electrical load during operation with fixed flow rates of hydrogen and air. The simulation of 25-cm2 active area with a serpentine flow path shows the interactions of the anode and cathode flow streams, the flow through the gas diffusion media, and the movement of water through the MEA by electroosmotic and back diffusion forces. The simulation used a commercial computational fluid dynamics (CFD)...
Optimization of marine vessels requires that the interaction between hull, propulsion and steering devices, and other appendages is taken into account. In addition, one needs to account for the variable floating position at different operating conditions. Due to the complexity of all interactions, experimental optimization is both costly and time-consuming. Computational methods can help in predicting efficiently the effects of design changes on resistance and other properties of the vessel.The aim of this paper is to present the results of several validation studies which include both...
Optimization of marine vessels requires that the interaction between hull, propulsion and steering devices, and other appendages is taken into account. In addition, one needs to account for the variable floating position at different operating conditions. Due to the complexity of all interactions, experimental optimization is both costly and time-consuming. Computational methods can help in predicting efficiently the effects of design changes on resistance and other properties of the vessel. The aim of this paper is to present the results of several validation studies which include both...
Based on the successful predictions of transient drop sizes in the first part of this research (Maaß et al., Prediction of drop sizes for liquid–liquid systems in stirred slim reactors—part I: single stage impellers. Chem. Eng. J., 162 (2010) 792–801), this part is a straight continuation and extension of the earlier work. The predictive capabilities of the used population balance equation model are increased for single stage impellers and transferred to scale-up procedures of such applications. Therefore different scale-up rules for liquid–liquid systems are tested experimentally and by...
This paper presents recent results obtained as part of the on-going integral validation of an advanced Eulerian-Eulerian two-phase (E2P) computational fluid dynamics based boiling model that allows the detailed analysis of the two-phase flow and heat transfer phenomena in a Boiling Water Reactor (BWR) fuel assembly. The code is being developed as a customized module built on the foundation of the commercial CFD-code STAR-CD which provides general two-phase flow modeling capabilities. Simulations of a prototypic BWR fuel assembly experiment have been completed as an initial assessment of the...
Prediction of bubble size which governs interfacial transfer terms between the two phases is of importance for an accurate prediction of the subcooled boiling flow. In the present work, a mechanistic bubbles size model, S was examined to enhance the prediction capability of subcooled boiling flows for the CFD (computational fluid dynamics) code. In addition to this, advanced subcooled boiling models such as new wall boiling and two-phase logarithmic wall function models were also applied for an improvement of energy partitioning and two-phase turbulence models, respectively. The benchmark...
In order to enhance the prediction capability of subcooled boiling flows, an advanced wall boiling model and mechanistic bubbles size model were examined using a CFD (Computational Fluid Dynamics) code. The advanced wall boiling model consists of a mechanistic bubble departure size model (Klausner et al., 1993), Hibiki et al.’s (2009) active nucleate site density model and Cole’s (1960) bubble departure frequency model. To ensure a wide range applicability of the advanced wall boiling model, each sub-model was evaluated separately over a wide range of flow conditions in pressure, temperature...
Many researchers have experimentally studied small (∼10–50 cm2), single cell PEMFC systems to understand the behavior and electrochemistry of PEMFC. Also, three-dimensional electrochemical models have been used to predict the distributions of current, temperature, and species mole fractions as a function of the operating conditions and geometry of small cells and these predictions have been compared with experimental data. However, the commercial viability of PEMFC systems depends on understanding the mass transport and electrochemistry of large-scale electrodes with reacting area on the...
Pneumatic conveying of solid materials is used in many process industries where solid particles are carried forward in pipes and channels by the fluid. The pressure drop in the system is dependent on a host of parameters such as particle and pipe diameters, particle and fluid properties, pipe roughness and orientation, etc. In this study, the commercial CFD software, STAR-CD is used to model pneumatic conveying in a horizontal pipe. A range of fluid flow rates is studied. Reasonable agreement is obtained between the predicted pressure drop and the experimental data of Marcus et al. (1990) for...
The Computational Fluid Dynamics analysis of the hydrodynamic performance of two America’s Cup design candidates is presented. Two fully appended hulls were tested in a free to sink and trim condition. The experimental data of one of the two hulls was known a priori and was used to investigate several computational parameters, which are discussed in the present paper. The validated numerical model was used to predict the performance of the second hull, whose experimental data were unknown a priori. The a posteriori numerical/experimental comparison showed that the numerical model was able to...

Pages