5 research outputs found
Wet Gas Flow Metering Technique Using a Venturi With Conductance Sensors
No full textWet gas metering is becoming an increasingly important problem to the oil and gas industry. Much research has been done to measure the water and gas flow rates of two-phase flows using a Venturi meter. The Venturi meter is a favoured device for metering of unprocessed wet natural gas production flows. In this thesis, various combinations of techniques have been employed in annular gas-liquid two phase flows to measure the flow parameters (e.g. liquid film thickness, gas volume fraction and gas and water flow rates). One of the most useful techniques which was used and which has proven attractive for many previous multiphase flow applications is the electrical conductance technique used in conjunction with the Venturi.
In this thesis, research has been done on designing a novel wet gas flow metering technique, which combines a Venturi with conductance sensors at the inlet and throat to measure the gas and the water flow rates and gas mass flow rate in vertical annular (wet gas) flows. Two ring conductance sensors at the inlet of the Venturi were used to measure the film velocity by cross correlation, one of the inlet ring conductance sensors was used to measure the film thickness and the inlet gas volume fraction. A ring conductance sensor at the throat was used to measure the gas volume fraction at the Venturi throat. A digital level sensor was also used to measure the film thickness (and the gas volume fraction) at the inlet of the Venturi. The reason for measuring the film thickness, the film velocity, the gas volume fraction at the inlet and the throat of the Venturi was to determine the gas and water flow rate and the gas mass flow rate in annular wet gas two phase flow using a variety of mathematical models of Venturis.
This work included both static ‘bench’ and flow loop experiments. In the flow loop experiments, which were limited to air-water two-phase flow, the test section included a Venturi meter with a 50mm inlet diameter with conductance sensors at inlet and the throat. Reference measurements of the water and air were made with a turbine flow meter and a variable area flow meter respectively. A Honeywell DP cell sensor was used to measure the differential pressure between the inlet and the throat of the Venturi.
A NI USB 6009 data acquisition device was used to integrate the system measurements and to control the operation of the overall Venturi system. A program was created using Labview software to read the input signals from the throat conductance ring sensor; the inlet conductance ring sensors; the digital level sensor; the DP cell sensor; the variable area flow meter and the turbine meter. From these measurements the gas volume fraction at the Venturi inlet and the throat, the differential pressure between the inlet and the throat of the Venturi, the film thickness and the film velocity at the Venturi inlet were calculated and were used with appropriate mathematical models to calculate the gas volumetric rate; gas mass flow rate; and the water mass and volumetric flow rates. Reference values of the gas a water flow rates were also calculated from the turbine meter and variable area flow meter outputs
30-day Morbidity and Mortality after Cholecystectomy for Benign Gallbladder Disease (AMBROSE): A Prospective, International Collaborative Cohort Study
Get PDFObjective: This study aimed to assess 30-day morbidity and mortality rates following cholecystectomy for benign gallbladder disease and identify the factors associated with complications. Summary background data: Although cholecystectomy is common for benign gallbladder disease, there is a gap in the knowledge of the current practice and variations on a global level. Methods: A prospective, international, observational collaborative cohort study of consecutive patients undergoing cholecystectomy for benign gallbladder disease from participating hospitals in 57 countries between January 1 and June 30, 2022, was performed. Univariate and multivariate logistic regression models were used to identify preoperative and operative variables associated with 30-day postoperative outcomes. Results: Data of 21,706 surgical patients from 57 countries were included in the analysis. A total of 10,821 (49.9%), 4,263 (19.7%), and 6,622 (30.5%) cholecystectomies were performed in the elective, emergency, and delayed settings, respectively. Thirty-day postoperative complications were observed in 1,738 patients (8.0%), including mortality in 83 patients (0.4%). Bile leaks (Strasberg grade A) were reported in 278 (1.3%) patients and severe bile duct injuries (Strasberg grades B-E) were reported in 48 (0.2%) patients. Patient age, ASA physical status class, surgical setting, operative approach and Nassar operative difficulty grade were identified as the five predictors demonstrating the highest relative importance in predicting postoperative complications. Conclusion: This multinational observational collaborative cohort study presents a comprehensive report of the current practices and outcomes of cholecystectomy for benign gallbladder disease. Ongoing global collaborative evaluations and initiatives are needed to promote quality assurance and improvement in cholecystectomy
Development of a piezoelectric nanogenerator for applications in biomedical sensors
No full textilustraciones, diagramasEl uso de los PENG (nanogeneradores piezoeléctricos) como sensores ha causado mucho interés en los últimos años en diversas áreas de la ingeniería y medicina. Para desarrollar estos dispositivos es necesario usar materiales piezoeléctricos. Dentro de los materiales piezoeléctricos que pueden ser sintetizados, se encuentra el titanato circonato de plomo (PZT), uno de los materiales más usados; sin embargo, la presencia de plomo y sus impactos tanto ambientales como en la salud humana, han incrementado el interés por materiales que no contengan este elemento en su composición. El óxido de zinc (ZnO) es considerado una alternativa, ya que no es tóxico y puede estar sometido a grandes deformaciones mecánicas durante periodos prolongados, siendo ambas características benéficas para el desarrollo de estos dispositivos. Sin embargo, el valor d33 del PZT (~117 pC/N) es superior al ZnO (~12 pC/Ny esto sugiere que la salida eléctrica de los dispositivos basados en ZnO podría ser menor. La estrategia más empleada para incrementar el coeficiente d33 y la salida eléctrica ha sido el uso de dopantes y el efecto de la morfología, sin embargo, el efecto de estos parametrossobre la salida eléctrica ha sido poco estudiado. Adicionalmente, diversos trabajos usan sistemas mecánicos poco robustos para la evaluación de la salida eléctrica de los dispositivos PENG y podrían inducir errores durante el análisis. En este trabajo se sintetizaron dos morfologías de óxido de zinc con el fin de desarrollar un dispositivo que podría ser usado como sensor. Adicionalmente, se propuso una metodología de ensayo de este tipo de dispositivos con el fin de estandarizar el método. Los análisis SEM evidenciaron la obtención de partículas con morfología de barras y hojas. El análisis DRX conformó que ambos tipos de partículas evidencian la fase cristalina Wurtzita, la más común en el ZnO. Mediante análisis TGA se evaluó la cantidad de ZnO presente en los dos compuestos desarrollados, la diferencia entre ambos fue de 0.02 %. Adicionalmente, se propuso un sistema mecánico para realizar los ensayos de salida eléctrica, el cual consiste de una máquina universal de ensayos adaptada para este fin. El sistema entrega la fuerza aplicada durante cada ciclo y de esta manera se puede normalizar la salida eléctrica. Respecto a la salida de voltaje del dispositivo, el compuesto basado en barras de ZnO evidenció una mayor salida en comparación con el compuesto basado en hojas. Esto podría deberse a la formación de una red conductora que favorece la transferencia de carga dentro del compuesto. (Texto tomado de la fuente)PENGs (Piezoelectric nanogenerators) used as sensors have caused great interest in recent years across several areas of engineering and medicine. The development of these devices requires the use of piezoelectric materials. Several piezoelectric materials that can be synthesized, the lead zirconate titanate (PZT), is the most used materials; however, the presence of lead and its environmental and human impacts have increased interest in materials that do not contain this element in their composition. Zinc oxide (ZnO) is considered an alternative since it is not toxic and can be subjected to large mechanical deformations for long periods, both features being beneficial for the development of these devices. However, the d33 value of PZT (~117 pC/N) is higher than ZnO (~12 pC/N), this suggest that the electrical output of ZnO-based devices could be lower. The most used strategy has been the dopants and the effect of morphology on electrical output has been little studied. Additionally, several works use less robust mechanical systems for the evaluation of the electrical output of PENG devices and could induce errors during the analysis. In this work, two morphologies of zinc oxide were synthesized in order to develop a device that could be used as a sensor. Additionally, a testing methodology for this type of device was proposed in order to standardize the testing method. The SEM microgaph evidenced the obtaining of particles with morphology of rods and sheets. The XRD analysis confirmed that both types of particles evidenced the Wurtzite crystalline phase, the most common in ZnO. Through TGA analysis, the amount of ZnO present in the two developed compounds was evaluated, the difference between the boths was 0.02%. Additionally, a mechanical system was proposed to perform the electrical output tests. This system consists of a universal testing machine adapted for this purpose. The system delivers the force applied during each cycle and in this way the electrical output can be normalized. Regarding the voltage output of the device, the ZnO rod-based composite exhibited a higher output compared to the sheet-based composite. This could be due to the formation of a conducting network that favors charge transfer within the compound.MaestríaMagíster en Ingeniería - Materiales y ProcesosNuevos materialesÁrea Curricular de Materiales y Nanotecnologí
Proceedings of First Conference for Engineering Sciences and Technology: Vol. 2
Get PDFThis volume contains contributed articles of Track 4, Track 5 & Track 6, presented in the conference CEST-2018, organized by Faculty of Engineering Garaboulli, and Faculty of Engineering, Al-khoms, Elmergib University (Libya) on 25-27 September 2018.
Track 4: Industrial, Structural Technologies and Science Material
Track 5: Engineering Systems and Sustainable Development
Track 6: Engineering Management
Other articles of Track 1, 2 & 3 have been published in volume 1 of the proceedings at this lin
