A Comparative Analysis of Conductance Probes and High-Speed Camera Measurements for Interfacial Behavior in Annular Air-Water Flow

[EN] Different techniques are used to analyze annular flow, but the more interesting ones are those techniques that do not perturb the flow and provide enough resolution to clearly distinguish the interfacial phenomena that take place at the interface, especially the disturbance waves (DW) and the ripple waves (DW). The understanding of these events is important because it influences the heat and mass transfer taking place through the thin film formed near the walls in this flow regime. The laser-induced fluorescence (LIF) and the three-electrode conductance probe are two commonly used techniques to study experimentally annular flow phenomena. In this paper, a set of experiments at different temperatures of 20 degrees C, 30 degrees C and 40 degrees C and different liquid Reynolds numbers have been performed in the annular flow regime, the characteristic of the DW and RW as average height and frequency of these waves has been measured by both techniques LIF and conductance probes. In addition, we also measured the mean film thickness. It was found that the mean film thickness and the DW height are practically the same when measured by both techniques; however, the height of the RW is smaller when measured by the conductance probe and this difference diminishes when the temperature increases.This research was funded by the Plan Nacional de I+D, grant number ENE2016-79489-C2-1-P, Ministerio de Economia y Competitividad.Rivera, Y.; Bidon, M.; Muñoz-Cobo, JL.; Berna, C.; Escrivá, A. (2023). A Comparative Analysis of Conductance Probes and High-Speed Camera Measurements for Interfacial Behavior in Annular Air-Water Flow. Sensors. 23(20):1-33. https://doi.org/10.3390/s23208617133232

Maximizing the use of hydrogen as energy vector to cover the final energy demand for stand-alone systems, application and sensitivity analysis for the Canary Archipelago by 2040

[EN] Fossil fuel-based economies must undergo a deep transition for complete decarbonization. To this end, it is widely recognized that all economies must move towards the electrification of energy end uses. Even though there is a part that cannot be electrified, at least at affordable costs; clear examples are heavy road transport, maritime and air transport, and some industrial processes. As a result of the limitations of electrification in certain energy end uses, the potential use of hydrogen as an alternative energy carrier has been examined in recent decades. Hydrogen is seen as a viable option for the medium to long term. Specifically, efforts are being made in the case of the Canary Islands to move towards a carbon-free energy mix. In fact, the aim is to advance the economy decarbonization by 10 years over the date foreseen for both Europe and the rest of Spain. To this end, the HOMER program has been used to analyze the possibility of producing the necessary hydrogen in a scenario applied to the Canary Islands in which the uses of this energy vector have been maximized. This research considers two possible scenarios, together with a sensitivity analysis under the different uncertain conditions associated with the used technologies. The results have been the estimation of hydrogen production costs for high demands, about 230,000 tH2/year, in 2040 for an isolated archipelago under two totally different generation scenarios. The first scenario is totally renewable, while the other is based on nuclear generation by means of high-temperature SMRs. The results show, that it would be possible to produce at a cost in the range of 1 euro/kgH2 using nuclear technology and around 4 euro/kgH2 using renewables, with uncertainty cost ranges of around 40%, i.e. costs between 0.85-1.48 and 3.29-4.99 euro kgH2 respectively.The authors would like to express their gratitude to the Generalitat Valenciana (Spain) for its support under the Santiago Grisolia Program/2018/140. The authors also would like to extend their gratitude to the Ministerio de Economia, Industria y Competitividad and by Agencia Nacional de Investigacion under the FPI grant BES-2017-080031.Berna, C.; Rivera-Durán, Y.; Córdova-Chávez, Y.; Muñoz-Cobo, JL. (2023). Maximizing the use of hydrogen as energy vector to cover the final energy demand for stand-alone systems, application and sensitivity analysis for the Canary Archipelago by 2040. Progress in Nuclear Energy. 163. https://doi.org/10.1016/j.pnucene.2023.10479116

Experimental Measurements and CFD Results of Liquid Film Thickness in Vertical Downward Air-Water Annular Flow

[EN] Annular gas¿liquid flows have been extensively studied over the years. However, the nonlinear behavior of the interface is still currently the subject of study by multiple researchers worldwide. The appearance of a liquid layer on the wall and its turbulent behavior support the heat exchange of multiple systems in the industrial field. Research in this area allows the optimization of these installations as well as the analysis of possible safety problems if the liquid film disappears. This study first shows some of the most important findings obtained in the GEPELON experimental facility (GEneración de PElícula ONdulatoria or Wavy Film Generator). The facility was built in order to analyze the behavior of the liquid film in annular downward air¿water flow. The experimental range of the inlet conditions is 800¿8000 for the ReL and 0¿110,000 for the Reg. Measurements for the mean film thickness show a fairly good agreement with the empirical correlations and the measurements of other authors. One of the most demanded applications of this type of measurements is the validation of computational dynamics or CFD codes. Therefore, the experiment has been modeled using Ansys CFX software, and the simulation results have been compared with the experimental ones. This article outlines some of the reasons why two-phase flow simulations are currently challenging and how the codes are able to overcome them. Simulation predictions are fairly close to the experimental measurements, and the mean film thickness evolution when changing the boundary conditions also shows a good agreement.The authors are indebted to the plan of I+D support of the EXMOTRANSIN project ENE2016-79489-C2-1-P.Rivera-Durán, Y.; J. L. Muñoz-Cobo; A. Escrivá; C. Berna; Y. Córdova (2022). Experimental Measurements and CFD Results of Liquid Film Thickness in Vertical Downward Air-Water Annular Flow. International Journal of Computational Methods and Experimental Measurements. 10(2):93-103. https://doi.org/10.2495/CMEM-V10-N2-93-1039310310

Experiments in free falling and downward cocurrent annular flows-Characterization of liquid films and interfacial waves

[EN] Falling liquid films and downward cocurrent flows in rounded shape pipes have been experimentally studied during the last decades, estimating the evolution of its major characteristics. The most important variables during the formation and growth of surface waves in falling downward flows have been measured using conductance probes. The main objective of the current research paper is to study the dependency of the characteristics of the thin liquid layer for downward cocurrent annular flows. The GEPELON experimental facility consists of a vertical pipe with 3.8 m of useful test length. Two pipe diameters have been analysed in this experimental study, 42 and 30 mm, in which the range covered by the liquid Reynolds number varies between 570 and 8500 and 800-7900 respectively, while the gas Reynolds numbers vary from 0 to 7.9.10(4) and from 0 to 1.1.10(5) respectively for the mentioned pipe diameters. Up to five conductance probes have been placed along the pipes test sections to capture the liquid film thickness fluctuations along time at different distances of the pipe entrance for both developing and fully developed regions. After the study and analysis of the experimental data, the central point of this paper has been the development of new correlations for the liquid film thicknesses and the two major properties of the interfacial waves. Their adjustment procedure has been carried out in terms of dimensionless numbers, aiming to provide more general relationships. In particular, the magnitudes that characterise the interface behavior have been measured, particularly film thicknesses, average disturbance wave amplitudes, and disturbance wave frequencies for each boundary condition. An additional part of the document contains an extensive comparison between the results obtained in this study and the data and expressions of other authors. It has been confirmed the significant dispersion existing among different researchers, especially when analysing variables related to the interfacial waves. This highlights the lack of knowledge in some aspects even today. The different correlations proposed have been calculated based on the best fit of the data from all the series of experiments carried out in this study. Comparisons of the behaviour of these correlations with data from other researchers have also been included.This research is supported by the EXMOTRANSIN project ENE2016-79489-C2-1-P included in the I + D Spanish plan. Funding for open access charge: CRUE-Universitat Politècnica de València.Rivera-Durán, Y.; Berna, C.; Muñoz-Cobo, JL.; Escrivá, A.; Córdova, Y. (2022). Experiments in free falling and downward cocurrent annular flows-Characterization of liquid films and interfacial waves. Nuclear Engineering and Design. 392:1-23. https://doi.org/10.1016/j.nucengdes.2022.11176912339

Numerical simulation of air discharged in subcooled water pool

[EN] Turbulent jet discharges in subcooled water pools are essential for safety systems in nuclear power plants, specifically in the pressure suppression pool of boiling water reactors and In-containment Refueling Water Storage Tank of advanced pressurized water reactors. The gas and liquid flow in these systems is investigated using multiphase flow analysis. This field has been extensively examined using a combination of experiments, theoretical models, and Computational Fluid Dynamics (CFD) simulations. ANSYS CFX offers two approaches to model multiphase flow behavior. The non-homogeneous Eulerian-Eulerian Model has been used in this work; it computes global information and is more convenient to study interpenetrated fluids. This study utilized the Large Eddy Simulation Model as the turbulence model, as it is better suited for non-stationary and buoyant flows. The CFD results of this study were validated with experimental data and theoretical results previously obtained. The figures of merit dimensionless penetration length and the dimensionless buoyancy length show good agreement with the experimental measurements. Correlations for these variables were obtained as a function of dimensionless numbers to give generality using only initial boundary conditions. CFD numerical model developed in this research has the capability to simulate the behavior of non-condensable gases discharged in water.This work was supported by the project THAIS co-financed by the CSN (Nuclear Safety Council of Spain) and the UPV (Polytechnical University of Valencia). The authors also would like to express gratitude to the Generalitat Valenciana (Spain) for its support under the Santiago Grisolia Program/2018/140.Córdova, Y.; Blanco, D.; Rivera, Y.; Berna, C.; Muñoz-Cobo, JL.; Escrivá, A. (2023). Numerical simulation of air discharged in subcooled water pool. Nuclear Engineering and Technology. 55(10):3754-3767. https://doi.org/10.1016/j.net.2023.06.04137543767551

Experimental Characterization of the Dimensionless Momentum Length for Submerged Jet Discharges of Air-Steam Mixtures into Stagnant Water

[EN] A very efficient method of condensing the steam in various industrial applications is the steam direct discharge into pools with subcooled water. This kind of condensation is known as Direct Contact Condensation (DCC), by providing high heat transfer and mass exchange capacity, the steam condenses quickly. In the past few decades, many experiments have been carried out on the submerged jets of non-condensable gases and pure steam in pools, supplying much information of interest, but efforts are still being made to obtain more information. In particular, the research of steam and non-condensable gas mixtures is of great interest to the chemical, energy, and nuclear industry. Consequently, this study investigates the discharge behavior of air-steam mixtures in a pool with subcooled water by direct visualization techniques using a high-speed camera. To know the behavior of the dimensionless momentum length, tests were carried out considering several initial discharge conditions such as nozzle diameter, percentage of mixture, and flow rates. After image acquisition, a series of complex processing, filtering, and post-processing procedures are applied using a subroutine in MATLAB. The momentum length of the jet was measured and found to be heavily influenced by the nozzle diameter, the jet velocity, and the mixture percentage. A correlation is obtained for the dimensionless momentum length of the horizontal jet that depends on the Froude and Mach numbers.The authors would like to acknowledge the support provided through the Spanish project EXMOTRANSIN ENE2016-79489-C2-1-P and the Santiago Grisolía Program for the training of research personnel.Y. Córdova; D. Blanco; C. Berna; J. L. Muñoz-Cobo; A. Escrivá; Rivera-Durán, Y. (2022). Experimental Characterization of the Dimensionless Momentum Length for Submerged Jet Discharges of Air-Steam Mixtures into Stagnant Water. International Journal of Computational Methods and Experimental Measurements. 10(3):195-210. https://doi.org/10.2495/CMEM-V10-N3-195-21019521010

Expansión en Caos Polinómico como método de Cuantificación de la Incertidumbre en simulaciones CFD. Aplicación al benchmark Cold-Leg Mixing de la OECD/NE

[ES] En este documento se presenta un estudio de la metodología de cuantificación de la incertidumbre mediante Expansión en Caos Polinómico (PCE por sus siglas en inglés). La teoría presentada es aplicada a un benchmark de la OECD/NEA denominado Cold-Leg Mixing. Este benchmark está basado en la instalación experimental que recibe el mismo nombre y está desarrollada por la Texas A&M University. Se muestran varios estudios de sensibilidad para optimizar el cálculo de la simulación. El modelo de turbulencia utilizado finalmente corresponde a un modelo tipo Large Eddy Simulation. Los resultados de la simulación muestran una buena concordancia con las medidas experimentales, en especial después de aplicar el PCE.Los autores de este trabajo desean destacar la contribución del plan de apoyo I+D del proyecto EXMOTRANSIN ENE2016-79489-C2-1-P.Rivera-Durán, Y.; Muñoz-Cobo, JL.; Berna, C.; Escrivá, A. (2019). Expansión en Caos Polinómico como método de Cuantificación de la Incertidumbre en simulaciones CFD. Aplicación al benchmark Cold-Leg Mixing de la OECD/NE. Sociedad Nuclear Española. 1-8. http://hdl.handle.net/10251/180968S1

Characterization of the gas-liquid interfacial waves in vertical upward co-current annular flows

[EN] For more than fifty years, hundreds of research works have focused on the study of annular flow because of its huge importance in many industrial processes, for instance, chemical, petroleum, etc., being of particular interest in nuclear industry. Specifically, interfacial waves play a vital role in the mass, momentum and energy transference processes between gas and liquid phases. This paper describes the new experimental measurements of vertical upward co-current two-phase gas-liquid flow carried out in a tube with an inner diameter of 44 mm. The liquid film thickness and the major characteristics of the interfacial waves have been measured using a non-intrusive instrument, a conductance probe. The physical phenomenon in which this device is based is the change in the electrical conductivity between air and water, i.e., the electrical signal collected in the sensor receiver depends on the thickness of the liquid film layer. The experimental measurements range from 2000 to 3500 l/min for the gas volumetric flow rate, and from 4 to 10 l/min for the liquid volumetric flow rate. Correlation of the experimental measurements of liquid film thickness and the major properties of the interfacial waves have been analyzed using non-dimensional numbers. An important part of the document focuses on the comparison of the experimental data and the fitting correlations against several of the most widely used expressions. Throughout this paper, in addition to present all the available correlations, the existing scattering found when comparing against other expressions have been also confirmed, underlining the existence of gaps of knowledge even today. Emphasize that the proposed correlations are the ones that better fit the data of all experimental series carried out under the present study for the analyzed variables, with almost all the experimental points covered by the +/- 10% error bands of the new correlations.The authors are indebted to the plan of I+D support of the EXMOTRANSIN project ENE2016-79489-C2-1-P.Cuadros-Orón, JL.; Rivera-Durán, Y.; Berna, C.; Escrivá, A.; Muñoz-Cobo, JL.; Monrós-Andreu, G.; Chiva, S. (2019). Characterization of the gas-liquid interfacial waves in vertical upward co-current annular flows. Nuclear Engineering and Design. 346:112-130. https://doi.org/10.1016/j.nucengdes.2019.03.008S11213034

Excavaciones en el conjunto megalítico de la Peña Oviedo (Camaleño, Cantabria)

La excavación del conjunto megalítico de la Peña Oviedo, pretende ser el inicio de un estudio más amplio que aborde de manera global el fenómeno megalítico en las cue.ncas altas de los ríos Deva y Nansa. El total desconocimiento que se tenía hasta esta década, no ya del fenómeno megalítico, sino incluso de su existencia en estos valles montañosos del Occidente de Cantabria hace necesario un estudio que ponga de manifiesto sus características y las relaciones con las áreas vecinas.The excavation of the megalithic complex of the Peña Oviedo, pretends to be the beginning of a larger study that approaches the megalithic phenomenon in the global River basins of the Deva and Nansa rivers. The total lack of knowledge of the megalithic phenomenon, but not even of its existence in these mountain valleys of western Cantabria, requires a study that reveals its characteristics and relations with neighboring areas

Estudio del comportamiento de la película de líquido en flujo anular aire-agua en caída libre vertical

[ES] El documento recoge los detalles de la instalación experimental GEPELON (GEneración de PELícula ONdulatoria) cuyo objetivo principal es la realización y modelización de experimentos de caída libre aire-agua. La instalación tiene dos opciones, una de tamaño 3.8m y 42mm de diámetro y la otra de 3.8m y 30mm de diámetro. Se han llevado a cabo medidas del espesor de película de líquido utilizando varias sondas de conductancia en distintas posiciones (tanto antes como después de la zona de desarrollo del fluido). El agua se introduce mediante un inyector con caudales entre 1 ¿ 20 l/min y 1 ¿ 10 l/min respectivamente. Se espera obtener correlaciones de las magnitudes más importantes, así como ampliar el rango de medidas experimentales en tubos de 19 mm.Los autores quieren agradecer el apoyo de la Agencia Nacional de Investigación de España al proyecto EXMOTRANSIN, ENE2016-79489-C2-1-P.Rivera-Durán, Y.; Muñoz-Cobo, JL.; Escrivá, A.; Berna, C.; Iglesias, SM.; Domínguez, DS. (2019). Estudio del comportamiento de la película de líquido en flujo anular aire-agua en caída libre vertical. Sociedad Nuclear Española. 1-8. http://hdl.handle.net/10251/180960S1