23 research outputs found
Analysis of a pneumatic system for a two-phase flow sugar
This document shows a complete analysis the transportation of sugar particles by a pneumatic conveying station. This project shows an actual situation presenting in a food plant located in Aragua, Venezuela, where the sugar piping system suffers continuous obstructions. It was achieved an effective analysis of the phenomenon of solid-gas two-phase flow transport which involves a complex physics phenomenon. Two possible obstruction causes was studied: the high temperature at the blower exit that induces changes in the sugar properties caused by the working condition far from the designed operation condition, or the excessive friction losses, due to the system is working out of the dilute phase condition (optimal condition for the flow). The mathematical model described allowed to determine that the cause of the obstruction of the pipeline was the stick of the sugar to the internal wall, as consequence of this high temperature at the outlet of the blower
Study of the two-phase liquid loading phenomenon by applying CFD techniques
In order to understand the liquid loading phenomenon, 2D (axisymmetric) numerical simulations were performed. This phenomenon appears when the gas velocity reduces to a value below the critical speed of drop extraction in two-phase production wells, and as consequence liquid is accumulated in the tubing, increasing the pressure drop and reducing the flow rate within the tube. Simulations were made using air-water as working fluids over a vertical pipe of 4 meters long through a commercial package of CFD. Comparison between the simulation results and the experimental data available in the literature shows a good capability of homogeneous models to predict the flow characteristics for a given velocity range close to the critical gas velocity; over 100% of this parameter the model significantly overestimates the pressure drop
Simulación del efecto de ataguías sumergidas sobre la futura operación de las turbinas Kaplan de la Central Hidroeléctrica Tocoma (Venezuela)
[ES] La Central Hidroeléctrica de Tocoma, actualmente en construcción, está localizada en la zona sur oriental de Venezuela en el Estado Bolívar sobre las aguas del Río Caroní. Tocoma será equipada con 10 turbinas Kaplan, con potencia instalada de 2.160 MW y un Aliviadero con una capacidad de 28.750 m3/s, y junto con las presas de Macagua, Caruachi y Guri conformarán del Desarrollo Hidroeléctrico del Bajo Caroní. El bjetivo de esta investigación es evaluar los efectos hidrodinámicos de las Ataguías “A” y “B” sumergidas sobre la operación de las turbinas Kaplan de la Central Hidroeléctrica Tocoma utilizando la modelación hibrida Matemática – Física. La presencia de estas Ataguías sumergidas puede dar origen a comportamientos hidrodinámicos tridimensionales pudiendo causar pérdidas adicionales de energía y mal funcionamiento de las turbinas. Se desarrollaron 2 modelos matemáticos monofásicos utilizando la técnica de la Dinámica Computacional de los Fluidos (CFD) aplicando el código comercial ANSYS-CFX 10. El primer modelo matemático representó el embalse d la Central Hidroeléctrica y fue calibrado cualitativa y cuantitativamente con un modelo físico a escala 1:80 gobernado bajo la ley de similitud de Froude. Este modelaje hibrido determinó los patrones de flujo hidrodinámicos de aproximación a las tomas de las turbinas Kaplan, los cuales evidencian una asimetría en la distribución de velocidades en las tomas cercanas a la Ataguía B. El segundo modelo matemático representó la toma y la turbina Kaplan considerando la asimetría de velocidades reportadas por el primer modelo matemático. Los resultados reportaron que la asimetría de velocidades no ocasiona ninguna irregularidad en la distribución de velocidades y presiones en los dominios estudiados en comparación con el caso de aproximación uniforme. Esto puede ser un indicativo de que la condición hidrodinámica no uniforme en la entrada de las tomas de las turbinas Kaplan de Tocoma no afecta el funcionamiento normal de la unidad turbogeneradora.Montilla, G.; Toscano, M.; Sánchez, R.; Shmueli, A.; Stanko, M.; Asuaje, M. (2008). Simulación del efecto de ataguías sumergidas sobre la futura operación de las turbinas Kaplan de la Central Hidroeléctrica Tocoma (Venezuela). Ingeniería del agua. 15(3):175-187. https://doi.org/10.4995/ia.2008.2934OJS175187153AEA Technology Engineering Software, Inc., CFX 10TM Solver Manual, 2006.Knuss, J., (1987). Swirling Flow Problems at Intakes. A.A. Balkema.Incropera, F. y Dewitt, D., (1996). Fundamental of Heat and Mass Transfer. 4a Edición, John Wiley and Sons.Montilla, G. y Toscano, M., (2008). Simulación Numérica de los Ductos de Desvío de la Central Hidroeléctrica Caruachi. CIMENICS'2008.Shumueli, A. y Stanko, M., (2007). Estudio de la Hidrodinámica de la Caja Semi-Espiral de la Unidad 10 de la Central Hidroeléctrica Tocoma. Tesis en Ing. Mecánica USB.Toscano, M. y Sánchez, R., (2006). Aplicación de un Modelo de CFD en el Estudio de la Aproximación Hidrodinámica a las Tomas de la Casa de Máquinas de la Central Hidroeléctrica de Tocoma. Tesis en Ing. Civil UCAB.Wesseling, P., (2000). Principles of Computational Fluid Dynamics. Springer-Verlag
Numerical Modeling of the Flow Inside a Centrifugal Pump: Influence of Impeller–Volute Interaction on Velocity and Pressure Fields
An alternative source for Venezuelan nuclear energy production: The Thorium Molten Salt Reactor
Arachidonic acid activation of BKCa (Slo1) channels associated to the β1-subunit in human vascular smooth muscle cells
Arachidonic acid (AA) is a polyunsaturated fatty acid involvedin a complex network of cellsignaling. Itis well known that this fatty acid can directly modulate several cellu- lar target structures, among them, ion channels. We explored the effects of AA on high conductance Ca 2+ - and voltage- dependent K + channel (BKCa) in vascular smooth muscle cells (VSMCs) where the presence of β1-subunit was functionally demonstrated by lithocholic acid activation. Using patch- clamp technique, we show at the single channel level that 10 μM AA increases the open probability (Po) of BKCa channels tenfold, mainly by a reduction of closed dwell times. AA also induces a left-shift in Po versus voltage curves without modifying their steepness. Furthermore, AA acceler- atesthekineticsofthevoltagechannelactivationbyafourfold reduction in latencies to first channel opening. When AAwas tested on BKCa channel expressed in HEK cells with or without the β1-subunit, activation only occurs in presence of the modulatory subunit. These results contribute to highlight the molecular mechanism of AA-dependent BKCa activation. We conclude that AA itself selectively activates the β1- associated BKCa channel, destabilizing its closed state proba- bly by interacting with the β1-subunit, without modifying the channel voltage sensitivity. Since BKCa channels physiologi- cally contribute to regulation of VSMCs contractility and blood pressure, we used the whole-cell configuration to show that AA is able to activate these channels, inducing significant cell hyperpolarization that can lead to VSMCs relaxation.Grupo de Investigación en Fisiología Vascula
Ensilaged biostimulants promoting root health and control of Radopholus similis in banana (Musa AAA) cv. Grande Naine
This study evaluates plant growth promotion and the suppressive effect of the burrowing nematode (Radopholus similis) in banana Musa AAA cv Grande Naine, by two ensilaged biostimulants (EBSs) in two greenhouse trials and in two different commercial farms. Conductive (CS) and suppressive (SS) soils to plant parasitic nematodes were used for EBSs production. The EBSs were incorporated in the growth substrate at 10% w/w before planting the in vitro banana plants and before R. similis inoculation in the greenhouse trials. In commercial banana plantations, the treatments were applied every four months by incorporating 500 g of the EBS into the soil in front of the successional sucker of each banana plant. The results showed that both EBSs were effective, stimulating the root growth and reducing R. similis. The EBS with CS reduced R. similis consistently in greenhouse and field evaluations. The data suggests the potential of EBSs to promote unfavorable conditions for the burrowing nematode reproduction and more favorable conditions to the development and production of the crop, which could contribute to promote more sustainable banana production.This research was financed with the joint support of the PINN scholarship program of the Ministry of Science, Technology and Telecommunications (MICITT) and the National Banana Corporation (CORBANA), of Costa Rica.Peer reviewe