Resumo O objetivo deste trabalho é apresentar resultados experimentais e numéricos de soldagem de tubos AISI 304L em operação utilizando o processo TIG. Foi montada e construída uma bancada experimental para soldagem em operação que permite a montagem de um corpo de prova tubular de aço inoxidável AISI 304L e que utiliza água como como fluido de trabalho. Foram realizadas medições de temperatura na superfície interna do tubo, da vazão do fluido e da corrente e tensão de soldagem. Baseado nos dados experimentais obtidos da bancada experimental e, também, nas análises microscópicas, foi desenvolvido um modelo numérico utilizando o método de volumes finitos para prever o ciclo térmico de soldagem e as consequências deste aporte térmico sobre as transformações metalúrgicas. A fonte de energia (arco voltaico) foi modelada como uma superfície gaussiana móvel sobre uma elipsoide. Os resultados obtidos da simulação apresentaram uma boa concordância com os obtidos na bancada experimental, demonstrando que a simulação pode ser utilizada como uma ferramenta confiável para a previsão do processo de soldagem em operação.

Abstract The objective of this work is to present experimental and numerical results of the welding on in-service of AISI 304L pipes using the GTAW process. An experimental workbench was assembled and constructed with an AISI 304L stainless steel tube using water as a working fluid; temperature of the inner surface of the pipe, as well as the water flow rate, and the current and voltage of the welding process were acquired. Based on the information obtained with the experimental workbench and the microscopic analyses of the welding material, a numerical model was developed using the finite volume method to predict the thermal welding cycle and the heat-affected zone (HAZ). The welding energy was modeled as a movable Gaussian ellipsoid. The results obtained from the simulation were in good agreement with those obtained with the experimental workbench and therefore demonstrating that the proposed simulation can be used as a reliable tool for predicting the welding process on in-service stainless tubes.

Abstract This study presents a numerical investigation of the dynamics of methane adsorption in granular activated carbon beds with bidisperse packing in order to reduce the void spaces between the adsorbent particles and to improve the storage capacity in adsorbed natural gas vessels. Two distinct particle sizes (d and D) were used for the packing of the bidisperse bed, and the following particle size ratios were investigated: δ = d/D = 1 (monodisperse bed), 1/5, 1/10, 1/15, and 1/20. Compared with the monodisperse bed condition, the results obtained showed that bidisperse packing increases bed density by about 30% and methane storage capacity by up to 20%. The results also showed that the charging time could be optimized by increasing the pressure drop applied to the bed and that the storage capacity can be increased by cooling the admitted gas in the vessel.

This work presents a comparative study among three linearization schemes widely used in petroleum reservoir simulation, namely the Implicit Pressure Explicit Saturation (IMPES), Fully Implicit (FI) and Adaptive Implicit Method (AIM). Attention is given to the criterion used for switching from IMPES to FI and vice-versa. The black-oil model considering the oil-water flow is employed. The equations are discretized using an unstructured Voronoi mesh in a finite-volume framework. The numerical results are analyzed based on the number of iterations in the Newton and solver procedures, number of implicit volumes, and mass balance error of components. The effect of the stopping criterion on Newton's iterations is also investigated. The outcome of the study reveals that adaptive implicit methodologies can be a good choice when unstructured grids are present, allowing the use of time steps with the same order of magnitude as the ones used in FI procedures, but with reduction in the computational effort.