scholarly journals Experimental and numerical simulation on buried hot fuel oil pipelines in three modes flow regime considering temperature loss during a shutdown

2020 ◽  
pp. 345-345
Author(s):  
Mohsen Dehdarinejad ◽  
Morteza Behbahani-Nejad ◽  
Ebrahim Hajidavalloo
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Pour Point ◽  
Large Scale ◽  
Fuel Oil ◽  
Fluid Density ◽  
Temperature Dependent ◽  
Buried Pipelines ◽  
Temperature Loss ◽  
Oil Pipelines

Aiming to study the temperature distribution along buried pipelines containing hot fuel oil, a new large-scale laboratory is constructed from the perspective of the corresponding fluid thermophysical properties. Also, a modeling of the pipeline, and the soil around it, was performed along the pipeline for observation of all three modes of turbulent, laminarization, and laminar flow, which is validated by experimental results. Furthermore, the appropriate data are also gathered from the actual pipeline, 107 km of the 26? pipeline between Abadan Refinery and Mahshahr Port, and the results of the experiment and modeling are reconfirmed. The experiment shows that the viscosity and fluid density of fuel oil is strongly temperature-dependent. Many experiments are performed on the parameters affected by temperature according to their importance. The method chosen to simulate three flow modes along the pipeline shows less than 2% error in turbulent and laminar zones and reveals just a 3% error to experimental data in the laminar region. The maximum safe time during the stopping period of the pipeline (MSST) and holding fuel oil in it is calculated based on the pour point of fuel oil. This time is critical for the real pipeline in sudden shutdown and is calculated 41 hours.

Experimental and Numerical Investigation of H2-Air Deflagration in the Presence of Concentration Gradients

2013 ◽  
Author(s):  
S. Kudriakov ◽  
E. Studer ◽  
M. Kuznetsov ◽  
J. Grune
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Hydrogen Concentration ◽  
Concentration Gradient ◽  
Large Scale ◽  
Gravity Concentration ◽  
Concentration Gradients ◽  
Flame Acceleration ◽  
Institute Of Technology ◽  
Karlsruhe Institute

A set of experiments performed at Karlsruhe Institute of Technology (KIT) in the framework of the LACOMECO European project is devoted to flame propagation in an obstructed large scale facility A3 (of 8 m height and 33 m3 volume) with initially vertical hydrogen concentration gradients. Almost linear positive and negative (relative to gravity) concentration gradients are created prior to ignition in the range from 4% to 13%, and the process of flame acceleration is investigated depending on hydrogen concentration gradient and ignition positions. In this paper we describe the A3 facility and analyse the experimental data obtained during the project. The results of numerical simulation performed using Europlexus code are presented together with the critical discussions and conclusions.

scholarly journals Numerical Simulation of the Exit Temperature Pattern of an Aircraft Engine Using a Temperature-Dependent Turbulent Schmidt Number

2021 ◽  
Vol 2021 (3) ◽  
pp. 34-46
Author(s):  
Igor F. Kravchenko ◽  
Dmytro V. Kozel ◽  
Serhii A. Yevsieiev
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Temperature Dependence ◽  
Schmidt Number ◽  
Aircraft Engine ◽  
Temperature Pattern ◽  
Temperature Dependent ◽  
Ansys Fluent ◽  
Turbulent Schmidt Number ◽  
Exit Temperature

Abstract This paper presents a numerical simulation for predicting the combustor exit temperature pattern of an aircraft engine, developed using the commercial fluid simulation software Ansys Fluent, which assumes a shape probability density function for the instantaneous chemistry in the conserved scalar combustion model and the standard k-ε model for turbulence. We found the compliance of the radial and circumferential non-uniformities of the exit temperature with the experimental data to be insufficient. To achieve much more accurate result, the mixing intensity was enhanced with respect to the initial calculation due to using the reduced value of the turbulent Schmidt number Sc. Numerical simulation was performed for values of the turbulent Schmidt number from Sc = 0.85 (default) up to Sc = 0.2, with results confirming the reduction of radial and circumferential non-uniformities of exit temperature. However, correlation between radial and circumferential non-uniformities is not admissible for these cases. Therefore, we propose to use a temperature-dependent formulation of the turbulent Schmidt number Sc, accounting for the increase in Sc number with increasing gas temperature. A user defined function (UDF) was used to implement the Sc number temperature dependence in Ansys Fluent. The numerical results for the proposed Schmidt number Sc temperature dependence were found to be in acceptable agreement with the experimental data both for radial and circumferential non-uniformities of the exit temperature pattern.

Experimental and numerical investigation of heat loss in transition modes of buried hot fuel oil pipeline

2021 ◽  
pp. 095440622110007
Author(s):  
Mohsen Dehdarinejad ◽  
Morteza Behbahani-Nejad ◽  
Ebrahim Hajidavalloo
Keyword(s):  
Experimental Data ◽  
Friction Factor ◽  
Heat Loss ◽  
Large Scale ◽  
Computer Network ◽  
Strong Dependence ◽  
Fuel Oil ◽  
Optimal Size ◽  
The Real ◽  
Oil Pipeline

In this research, heat transfer of fuel oil flow through the buried pipeline in three regimes, turbulent, transition, and laminar conditions are investigated. A large-scale laboratory set-up is designed for this purpose and numerical modeling was also performed to study the effect of different parameters. The simulation is based on the fluid's thermophysical properties and the results are validated using experimental data. Due to the strong dependence of viscosity and density of fuel oil on the temperature, regime changes along the pipeline happens which complicate the calculation of friction factor. Using the experiment results and choosing different numerical methods, the acceptable model of friction factor in the transition zone for the experimental pipe and the real pipeline was achieved. Numerical simulation was performed on a 107 km pipeline using a powerful computer network to achieve the results. The approach which is used to simulate laminarization shows just a 3% discrepancy with experimental data. For the real pipeline, about 30 percent of the length is in transition mode from turbulent to laminar. The diameter of 26” is chosen as the most optimal size to transform 180000 barrels per day (BPD). According to the design thickness, diameter, and length of the pipeline, the maximum safe stop time (MSST) of the pipeline is 41 hours which is the most important data in the pipeline's maintenance period. Based on the present experimental data and simulation results, the optimal depth for the least heat loss from this pipeline is 0.9 to 2.7 meters.

scholarly journals Numerical Simulation of air Temperature and air flow Distribution in a Cabinet tray Dryer

2019 ◽  
Vol 8 (11) ◽  
pp. 1836-1840
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Air Temperature ◽  
Large Scale ◽  
Air Flow ◽  
Flow Distribution ◽  
Improve Quality ◽  
Air Movement ◽  
Drying Chamber

The quality of dried product can be enhanced in cabinet tray dryers through a uniform distribution of drying air flow and temperature. In this work, a numerical investigation is conducted to examine the consequence of air movement on the quality of product dried in a convective tray dryer. The temperature and velocity contours of air in the drying chamber are numerically determined for three different geometries of cabinet tray dryer and are compared. A good harmony is found between the predicted data from CFD and experimental data from the literature. This work will enable us to optimize the drying chamber design for uniform dispersal of air flow and temperature and to improve quality of dried product for large scale applications

scholarly journals The Dynamics of Subunit Rotation in a Eukaryotic Ribosome

Biophysica ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 204-221
Author(s):  
Frederico Campos Freitas ◽  
Gabriele Fuchs ◽  
Ronaldo Junio de Oliveira ◽  
Paul Charles Whitford
Keyword(s):  
Free Energy ◽  
Large Scale ◽  
Small Subunit ◽  
Free Energy Barrier ◽  
Temperature Dependent ◽  
Molecular Flexibility ◽  
Subunit Rotation ◽  
Biological Kinetics ◽  
Rate Limiting ◽  
Reversible Rotation

Protein synthesis by the ribosome is coordinated by an intricate series of large-scale conformational rearrangements. Structural studies can provide information about long-lived states, however biological kinetics are controlled by the intervening free-energy barriers. While there has been progress describing the energy landscapes of bacterial ribosomes, very little is known about the energetics of large-scale rearrangements in eukaryotic systems. To address this topic, we constructed an all-atom model with simplified energetics and performed simulations of subunit rotation in the yeast ribosome. In these simulations, the small subunit (SSU; ∼1 MDa) undergoes spontaneous and reversible rotation events (∼8∘). By enabling the simulation of this rearrangement under equilibrium conditions, these calculations provide initial insights into the molecular factors that control dynamics in eukaryotic ribosomes. Through this, we are able to identify specific inter-subunit interactions that have a pronounced influence on the rate-limiting free-energy barrier. We also show that, as a result of changes in molecular flexibility, the thermodynamic balance between the rotated and unrotated states is temperature-dependent. This effect may be interpreted in terms of differential molecular flexibility within the rotated and unrotated states. Together, these calculations provide a foundation, upon which the field may begin to dissect the energetics of these complex molecular machines.

scholarly journals Numerical Simulation of EPB Shield Tunnelling with TBM Operational Condition Control Using Coupled DEM–FDM

2021 ◽  
Vol 11 (6) ◽  
pp. 2551
Author(s):  
Hyobum Lee ◽  
Hangseok Choi ◽  
Soon-Wook Choi ◽  
Soo-Ho Chang ◽  
Tae-Ho Kang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Tunnel Boring Machine ◽  
Chamber Pressure ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Operational Conditions ◽  
Shield Tunnelling ◽  
Epb Shield

This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.

scholarly journals Optimal Design of Slit Impeller for Low Specific Speed Centrifugal Pump Based on Orthogonal Test

2021 ◽  
Vol 9 (2) ◽  
pp. 121
Author(s):  
Yang Yang ◽  
Ling Zhou ◽  
Hongtao Zhou ◽  
Wanning Lv ◽  
Jian Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Large Scale ◽  
Internal Flow ◽  
Orthogonal Test ◽  
Centrifugal Pumps ◽  
Initial Model ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Four Levels

Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, determines the priority of the various geometric factors of the drainage trough on the pump performance, and obtains the optimal impeller drainage trough scheme. The influence of drainage tank structure on the internal flow of a low-specific speed centrifugal pump is also analyzed. First, based on the experimental validation of the initial model, it is determined that the numerical simulation method used in this paper is highly accurate in predicting the performance of low-specific speed centrifugal pumps. Secondly, based on the three factors and four levels of the impeller drainage trough in the orthogonal test, the orthogonal test plan is determined and the orthogonal test results are analyzed. This work found that slit diameter and slit width have a large impact on the performance of low-specific speed centrifugal pumps, while long and short vane lap lengths have less impact. Finally, we compared the internal flow distribution between the initial model and the optimized model, and found that the slit structure could effectively reduce the pressure difference between the suction side and the pressure side of the blade. By weakening the large-scale vortex in the flow path and reducing the hydraulic losses, the drainage trough impellers obtained based on orthogonal tests can significantly improve the hydraulic efficiency of low-specific speed centrifugal pumps.

scholarly journals Fibre-induced drag reduction

2008 ◽  
Vol 602 ◽  
pp. 209-218 ◽  
Author(s):  
J. J. J. GILLISSEN ◽  
B. J. BOERSMA ◽  
P. H. MORTENSEN ◽  
H. I. ANDERSSON
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Reduction ◽  
Elastic Layer ◽  
Turbulent Drag Reduction ◽  
Rigid Polymer ◽  
Fibre Concentration ◽  
Induced Drag ◽  
Turbulent Drag

We use direct numerical simulation to study turbulent drag reduction by rigid polymer additives, referred to as fibres. The simulations agree with experimental data from the literature in terms of friction factor dependence on Reynolds number and fibre concentration. An expression for drag reduction is derived by adopting the concept of the elastic layer.

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