In a typical injector string in SAGD operation, steam is injected through tubing placed inside a casing. Heat losses through the string and casing can result in lower quality steam being injected into the formation, and hence reduce the productivity of a SAGD operation. An ideal SAGD operation would be one where no heat losses happen inside the tubing and all the latent heat is released inside the formation to heat up the heavy oil. Several methods have been used to reduce heat losses in the injector tubing. One of the methods is the usage of a vacuum insulated tubing (VIT) placed inside the casing. VIT consists of specially manufactured tubing with a getter coating to maintain vacuum between ID and the OD of the tube. This helps in preventing heat losses compared to normal bare steel tubing. In an effort to demonstrate the benefits of VIT compared to bare tubing injector string, a comparative 3D Computational Fluid Dynamics (CFD) study was carried out. The objective of the study is to provide a comparison of heat loss in both VIT and bare tubing concentric and eccentric configurations. The simulation accounts for frictional and heat losses throughout the tubing and most importantly, condensation of steam inside the tubing as result of heat loss. The consideration of condensation inside the tubing is a critical component of the simulation as it in turn affects the heat loss through the tubing. The other significant aspect of the study is the consideration of eccentric and concentric placement of tubing string inside the casing and its effect on heat loss. This study uses an Euler-Euler Multiphase flow based approach which accounts for the fluid-fluid interactions such as drag, turbulent dispersion etc. between steam and water inside the tubing. The thermal phase change model in ANSYS CFD accounts for the condensation of steam into water. The computed results successfully demonstrate the benefits of vacuum insulated tubing over bare tubing in maintaining steam quality in the vertical section of the wellbore. Also, the study shows reduction in steam quality for eccentric position of the bare tubing compared to concentric position. Most importantly this study demonstrates the capability of CFD to solve industrial scale complex problems and provide engineers with an insight into some of the challenging physics associated with a SAGD operation in the field.
High‐fidelity, predictive fluid flow simulations of the interactions between the rising thermal plumes from forced air warming blower and the ultra‐clean ventilation air in an operating room (OR) are conducted to explore whether this complex flow can impact the dispersion of squames to the surgical site. A large‐eddy simulation, accurately capturing the spatiotemporal evolution of the flow in 3 dimensions together with the trajectories of squames, is performed for a realistic OR consisting of an operating table (OT), side tables, surgical lamps, medical staff, and a patient. Two cases are studied with blower‐off and blower‐on together with Lagrangian trajectories of 3 million squames initially placed on the floor surrounding the OT. The large‐eddy simulation results show that with the blower‐off, squames are quickly transported by the ventilation air away from the table and towards the exit grilles. In contrast, with the hot air blower turned on, the ventilation airflow above and below the OT is disrupted significantly. The rising thermal plumes from the hot air blower drag the squames above the OT and the side tables and then they are advected downwards toward the surgical site by the ventilation air from the ceiling. Temporal history of the number of squames reaching 4 imaginary boxes surrounding the side tables, the OT, and the patient's knee shows that several particles reach these boxes for the blower‐on case.
Oxy-fuel based pulse detonation system can be used for direct power extraction when combined with magnetohydrodynamics (MHD). A space-time conservation element solution element (CE/SE) method is used to investigate the operational envelope of oxy-coal detonations with gaseous methane as a surrogate fuel. The CE/SE method results in a consistent multidimensional formulation for structured/unstructured meshes by providing flux conservation in space and time without the need for complex Riemann solvers to capture solution discontinuities. A modified revised Jones-Lindstedt (JL-R) reaction mechanism accounting for radicals such as O, OH, and H was used as a reduced mechanism to simulate detonation waves from CH4−O2 combustion. The numerical scheme is first verified by comparing predictions with the ZND theory and other published data to show excellent agreement. For shock-induced detonation, the effect of driver shock temperature, pressure, stoichiometric ratio (ϕ) and initial driver shock length, on detonation initiation and propagation was investigated. The simulations accurately predicted detonation velocities, at various ϕ values, compared with available experimental data. The results show that higher gas temperatures and velocities are achieved through oxy-detonations compared to air. The chosen reduced chemical kinetic mechanism, that accounts for radical disassociation, is found to be critical in appropriately limiting heat release during oxy-combustion, thereby predicting detonation temperature and velocity accurately.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.