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Intrusive sensors are widely employed in numerous industrial applications to determine the phase fraction in gas-liquid two-phase flows. Such applications include those in the chemical, nuclear, and oil industries. This study aims to investigate the use of three distinct intrusive sensor topologies, specifically intended for underwater applications, wherein the detailed characterization of the disperse phase is the primary objective. Examples of such applications include aeration diffusers in wastewater treatment plants (WWTPs) and fish farming facilities., Peer Reviewed

Las regulaciones en materia de medio ambiente adoptan medidas cada vez más restrictas en aras de reducir la contaminación medioambiental, principalmente regulan dos aspectos en el mundo de la refrigeración, la carga máxima admisible de refrigerante en la instalación y el empleo de refrigerantes de bajo GWP. Por este motivo es importante disponer de una herramienta capaz de predecir el funcionamiento de los evaporadores de los sistemas de refrigeración dentro de las regulaciones estipuladas. En este artículo se presenta el modelo matemático generado para simular el funcionamiento de un evaporador de CO2 de tubos concéntricos y su validación experimental. La validación del modelo se realiza con el fin de generar una herramienta de cálculo capaz de optimizar el proceso de dimensionamiento de los evaporadores que se montan en los muebles frigoríficos en Frost-trol. Para realizar los cálculos de transferencia de calor se han introducido en el modelo correlaciones empíricas y correlaciones pseudoempíricas (patrones de flujo). Para la validación de los resultados del modelo se ha procedido al dimensionamiento y montaje de una instalación experimental. En este trabajo se realiza una comparación entre los resultados obtenidos para cada una de las diversas correlaciones y los datos medidos experimentales. El modelo final contendrá la correlación que más se ajuste a los datos experimentales.

El trabajo presentado en este artículo se basa en integrar en el interior de un mueble frigorífico comercial un fluido caloportador con cambio de fase que permite un funcionamiento totalmente autónomo durante un periodo de tiempo, sin necesidad de conexión eléctrica para mantener la temperatura del alimento perecedero. En este artículo se presenta una nueva solución para optimizar el rendimiento de los muebles frigoríficos destinados al almacenamiento de producto perecedero en un supermercado a la vez que se abre una nueva posibilidad de añadir servicios nuevos que hasta la fecha el mercado desconoce. Este estudio se ha llevado a cabo a partir de la acumulación térmica de un fluido compuesto por muestras PCM (Phase Change Material) y de la optimización de todos los mecanismos de transmisión de calor que coexisten durante el funcionamiento de un mueble. El almacenamiento de calor en un momento determinado para disponerlo más tarde se presenta como una solución sin precedentes. En este sentido, nace una manera nueva de producir frío que nos va a permitir recargar este acumulador térmico en horario de tarificación eléctrica más bajo y proporcionar un servicio autónomo y continuado para mantener las condiciones que necesita el almacenamiento del producto perecedero durante el horario de mejor coste energético y mitigando las variaciones de temperatura que pueda sufrir el producto perecedero.

During last years, supermarkets have increased the demand for closed refrigerated display cabinets due to new regulations and trends on energy and sustainability. However, the performance of this type of refrigerated display cabinets is not completely known, being of utmost importance how the airflow distributions could affect over the temperature distributions inside the cabinet. Consequently, this work presents a numerical evaluation of the performance of closed display cabinets focusing on the effect of the sliding doors opening process. The set of computational fluid dynamics (CFD) simulations served to validate the use of immersed solid approach in order to accurately analyze and evaluate transient behavior of the turbulent air flow distributions and temperature evolutions inside the cabinet and over the products, and characterizing the air curtain disruptions and the warm air entrainment during the opening process of the cabinet sliding doors (i.e. from closed doors, through doors opening process and to doors totally open).

[EN] In the computational modeling of two-phase flow, many uncertainties are usually faced in simulations and validations with experiments. This has traditionally made it difficult to provide a general method to predict the two-phase flow characteristics for any geometry and condition, even for bubbly flow regimes. Thus, we focus our research on studying in depth the bubbly flow modeling and validation from a critical point of view. The conditions are intentionally limited to scenarios where coalescence and breakup can be neglected, to concentrate on the study of bubble dynamics and its interaction with the main fluid. This study required the development of a solver for bubbly flow with higher resolution level than TFM and a new methodology to obtain the data from the simulation. Part I shows the development of a solver based on the CFD-DEM formulation. The motion of each bubble is computed individually with this solver and aspects as inhomogeneity, nonlinearity of the interfacial forces, bubble-wall interactions and turbulence effects in interfacial forces are taken into account. To develop the solver, several features that are not usually required for traditional CFD-DEM simulations but are relevant for bubbly flow in pipes, have been included. Models for the assignment of void fraction into the grid, seeding of bubbles at the inlet, pressure change influence on the bubble size and turbulence effects on both phases have been assessed and compared with experiments for an upward vertical pipe scenario. Finally, the bubble path for bubbles of different size have been investigated and the interfacial forces analyzed. (C) 2017 Elsevier Ltd. All rights reserved.

[EN] In the computational modeling of two-phase flow, many uncertainties are usually faced in simulations and validations with experiments. This has traditionally made it difficult to provide a general method to predict the two-phase flow characteristics for any geometry and condition, even for bubbly flow regimes. Thus, we focus our research on studying in depth the bubbly flow modeling and validation from a critical point of view. The conditions are intentionally limited to scenarios where coalescence and breakup can be neglected, to concentrate on the study of bubble dynamics and its interaction with the main fluid. This study required the development of a solver for bubbly flow with higher resolution level than TFM and a new methodology to obtain the data from the simulation. In Part II, taking profit of the detailed data provided by the CFD-DEM solver presented in Part I, we propose a novel methodology based on virtual sensor probes, to perform a rigorous validation and to investigate the experimental data. The same approximation used for processing the experimental datasets applies to simulation data, then the same assumptions are considered. In this way we can study an extended number of disperse phase variables as bubble velocity, void fraction, interfacial area concentration, mean chord length and distribution, Sauter mean diameter, bubble frequency and missing ratio, in addition to other variables as bubble size distribution or carrier phase velocity and turbulence. Several upward bubbly flow scenarios from datasets of different authors are used to validate the solver using this methodology. Finally, an axial evolution validation is performed including a discussion motivated by the comparison between experiments and the data from the virtual probes. (C) 2017 Elsevier Ltd. All rights reserved.