Effects of Brinkman Number on Thermal-Driven Convective Spherical Dynamos
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Experimental and Numerical Characterization of the Thermal and Hydraulic Performance of a Canned Motor Pump Operating with Two-P
EXPERIMENTAL AND NUMERICAL CHARACTERIZATION OF THE THERMAL AND HYDRAULIC PERFORMANCE OF A CANNED MOTOR PUMP OPERATING WITH TWO-PHASE FLOW A Dissertation by YINTAO WANG Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Adolfo Delgado Committee Members, Karen Vierow Kirkland Michael Pate Je-Chin Han Head of Department, Andreas A. Polycarpou May 2019 Major Subject: Mechanical Engineering Copyright 2019 Yintao Wang ABSTRACT Canned motor pump (CMP), as one kind of sealless pump, has been utilized in industry for many years to handle hazards or toxic product and to minimize leakage to the environment. In a canned motor pump, the impeller is directly mounted on the motor shaft and the pump bearing is usually cooled and lubricated by the pump process liquid. To be employed in oil field, CMP must have the ability to work under multiphase flow conditions, which is a common situation for artificial lift. In this study, we studied the performance and reliability of a vertical CMP from Curtiss-Wright Corporation in oil and air two-phase flow condition. Part of the process liquid in this CMP is recirculated to cool the motor and lubricate the thrust bearing. The pump went through varying flow rates and different gas volume fractions (GVFs). In the test, three important parameters, including the hydraulic performance, the pump inside temperature and the thrust bearing load were monitored, recorded and analyzed. The CMP has a second recirculation loop inside the pump to lubricate the thrust bearing as well as to cool down the motor windings. -
Heating and Flow Computations of an Amorphous Polymer in the Liquefier of a Material Extrusion 3D Printer Franck Pigeonneau, D
Heating and flow computations of an amorphous polymer in the liquefier of a material extrusion 3D printer Franck Pigeonneau, D. Xu, M. Vincent, J.-F. Agassant To cite this version: Franck Pigeonneau, D. Xu, M. Vincent, J.-F. Agassant. Heating and flow computations of an amor- phous polymer in the liquefier of a material extrusion 3D printer. Additive Manufacturing, Elsevier, 2019, pp.101001. 10.1016/j.addma.2019.101001. hal-02425219 HAL Id: hal-02425219 https://hal-mines-paristech.archives-ouvertes.fr/hal-02425219 Submitted on 30 Dec 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Heating and flow computations of an amorphous polymer in the liquefier of a material extrusion 3D printer F. Pigeonneau∗, D. Xu, M. Vincent, J.-F. Agassant MINES ParisTech, PSL Research University, CEMEF - Centre for material forming, CNRS UMR 7635, CS 10207, rue Claude Daunesse 06904 Sophia Antipolis Cedex, France Abstract The heating of a polymer in a liquefier of a material extrusion 3D printer is numeri- cally studied. The problem is investigated by solving the mass, momentum, and energy conservation equations. The polymer is taken as a generalized Newtonian fluid with a dynamical viscosity function of shear rate and temperature. -
Friction Losses and Heat Transfer in High-Speed Electrical Machines
XK'Sj Friction losses and heat transfer in high-speed electrical machines Juha Saari DJSTR10UTK)N OF THI6 DOCUMENT IS UNLIMITED Teknillinen korkeakoulu Helsinki University of Technology Sahkotekniikan osasto Faculty of Electrical Engineering Sahkomekaniikan laboratorio Laboratory of Electromechanics Otaniemi 1996 1 50 2 Saari J. 1996. Friction losses and heat transfer in high-speed electrical machines. Helsinki University of Technology, Laboratory of Electromechanics, Report 50, Espoo, Finland, p. 34. Keywords: Friction loss, heat transfer, high-speed electrical machine Abstract High-speed electrical machines usually rotate between 20 000 and 100 000 rpm and the peripheral speed of the rotor exceeds 150 m/s. In addition to high power density, these figures mean high friction losses, especially in the air gap. In order to design good electrical machines, one should be able to predict accurately enough the friction losses and heat-transfer rates in the air gap. This report reviews earlier investigations concerning frictional drag and heat transfer between two concentric cylinders with inner cylinder. rotating. The aim was to find out whether these studies cover the operation range of high-speed electrical machines. Friction coefficients have been measured at very high Reynolds numbers. If the air-gap surfaces are smooth, the equations developed can be applied into high-speed machines. The effect of stator slots and axial cooling flows, however, should be studied in more detail. Heat-transfer rates from rotor and stator are controlled mainly by the Taylor vortices in the air-gap flow. Their appearance is affected by the flow rate of the cooling gas. The papers published do not cover flows with both high rotation speed and flow rate. -
Rayleigh-Bernard Convection Without Rotation and Magnetic Field
Nonlinear Convection of Electrically Conducting Fluid in a Rotating Magnetic System H.P. Rani Department of Mathematics, National Institute of Technology, Warangal. India. Y. Rameshwar Department of Mathematics, Osmania University, Hyderabad. India. J. Brestensky and Enrico Filippi Faculty of Mathematics, Physics, Informatics, Comenius University, Slovakia. Session: GD3.1 Core Dynamics Earth's core structure, dynamics and evolution: observations, models, experiments. Online EGU General Assembly May 2-8 2020 1 Abstract • Nonlinear analysis in a rotating Rayleigh-Bernard system of electrical conducting fluid is studied numerically in the presence of externally applied horizontal magnetic field with rigid-rigid boundary conditions. • This research model is also studied for stress free boundary conditions in the absence of Lorentz and Coriolis forces. • This DNS approach is carried near the onset of convection to study the flow behaviour in the limiting case of Prandtl number. • The fluid flow is visualized in terms of streamlines, limiting streamlines and isotherms. The dependence of Nusselt number on the Rayleigh number, Ekman number, Elasser number is examined. 2 Outline • Introduction • Physical model • Governing equations • Methodology • Validation – RBC – 2D – RBC – 3D • Results – RBC – RBC with magnetic field (MC) – Plane layer dynamo (RMC) 3 Introduction • Nonlinear interaction between convection and magnetic fields (Magnetoconvection) may explain certain prominent features on the solar surface. • Yet we are far from a real understanding of the dynamical coupling between convection and magnetic fields in stars and magnetically confined high-temperature plasmas etc. Therefore it is of great importance to understand how energy transport and convection are affected by an imposed magnetic field: i.e., how the Lorentz force affects convection patterns in sunspots and magnetically confined, high-temperature plasmas. -
Constant-Wall-Temperature Nusselt Number in Micro and Nano-Channels1
Constant-Wall-Temperature Nusselt Number in Micro and Nano-Channels1 We investigate the constant-wall-temperature convective heat-transfer characteristics of a model gaseous flow in two-dimensional micro and nano-channels under hydrodynamically Nicolas G. and thermally fully developed conditions. Our investigation covers both the slip-flow Hadjiconstantinou regime 0рKnр0.1, and most of the transition regime 0.1ϽKnр10, where Kn, the Knud- sen number, is defined as the ratio between the molecular mean free path and the channel Olga Simek height. We use slip-flow theory in the presence of axial heat conduction to calculate the Nusselt number in the range 0рKnр0.2, and a stochastic molecular simulation technique Mechanical Engineering Department, known as the direct simulation Monte Carlo (DSMC) to calculate the Nusselt number in Massachusetts Institute of Technology, the range 0.02ϽKnϽ2. Inclusion of the effects of axial heat conduction in the continuum Cambridge, MA 02139 model is necessary since small-scale internal flows are typically characterized by finite Peclet numbers. Our results show that the slip-flow prediction is in good agreement with the DSMC results for Knр0.1, but also remains a good approximation beyond its ex- pected range of applicability. We also show that the Nusselt number decreases monotoni- cally with increasing Knudsen number in the fully accommodating case, both in the slip-flow and transition regimes. In the slip-flow regime, axial heat conduction is found to increase the Nusselt number; this effect is largest at Knϭ0 and is of the order of 10 percent. Qualitatively similar results are obtained for slip-flow heat transfer in circular tubes. -
A Numerical and Experimental Investigation of Taylor Flow Instabilities in Narrow Gaps and Their Relationship to Turbulent Flow
A NUMERICAL AND EXPERIMENTAL INVESTIGATION OF TAYLOR FLOW INSTABILITIES IN NARROW GAPS AND THEIR RELATIONSHIP TO TURBULENT FLOW IN BEARINGS A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Dingfeng Deng August, 2007 A NUMERICAL AND EXPERIMENTAL INVESTIGATION OF TAYLOR FLOW INSTABILITIES IN NARROW GAPS AND THEIR RELATIONSHIP TO TURBULENT FLOW IN BEARINGS Dingfeng Deng Dissertation Approved: Accepted: _______________________________ _______________________________ Advisor Department Chair Dr. M. J. Braun Dr. C. Batur _______________________________ _______________________________ Committee Member Dean of the College Dr. J. Drummond Dr. G. K. Haritos _______________________________ _______________________________ Committee Member Dean of the Graduate School Dr. S. I. Hariharan Dr. G. R. Newkome _______________________________ _______________________________ Committee Member Date R. C. Hendricks _______________________________ Committee Member Dr. A. Povitsky _______________________________ Committee Member Dr. G. Young ii ABSTRACT The relationship between the onset of Taylor instability and appearance of what is commonly known as “turbulence” in narrow gaps between two cylinders is investigated. A question open to debate is whether the flow formations observed during Taylor instability regimes are, or are related to the actual “turbulence” as it is presently modeled in micro-scale clearance flows. This question is approached by considering the viscous fluid flow in narrow gaps between two cylinders with various eccentricity ratios. The computational engine is provided by CFD-ACE+, a commercial multi-physics software. The flow patterns, velocity profiles and torques on the outer cylinder are determined when the speed of the inner cylinder, clearance and eccentricity ratio are changed on a parametric basis. -
Simulation of Taylor-Couette Flow. Part 2. Numerical Results for Wavy-Vortex Flow with One Travelling Wave
J. E’l~idM(&. (1984),FOI. 146, pp. 65-113 65 Printed in Chat Britain Simulation of Taylor-Couette flow. Part 2. Numerical results for wavy-vortex flow with one travelling wave By PHILIP S. MARCUS Division of Applied Sciences and Department of Astronomy, Harvard University (Received 26 July 1983 and in revised form 23 March 1984) We use a numerical method that was described in Part 1 (Marcus 1984a) to solve the time-dependent Navier-Stokes equation and boundary conditions that govern Taylor-Couette flow. We compute several stable axisymmetric Taylor-vortex equi- libria and several stable non-axisymmetric wavy-vortex flows that correspond to one travelling wave. For each flow we compute the energy, angular momentum, torque, wave speed, energy dissipation rate, enstrophy, and energy and enstrophy spectra. We also plot several 2-dimensional projections of the velocity field. Using the results of the numerical calculations, we conjecture that the travelling waves are a secondary instability caused by the strong radial motion in the outflow boundaries of the Taylor vortices and are not shear instabilities associated with inflection points of the azimuthal flow. We demonstrate numerically that, at the critical Reynolds number where Taylor-vortex flow becomes unstable to wavy-vortex flow, the speed of the travelling wave is equal to the azimuthal angular velocity of the fluid at the centre of the Taylor vortices. For Reynolds numbers larger than the critical value, the travelling waves have their maximum amplitude at the comoving surface, where the comoving surface is defined to be the surface of fluid that has the same azimuthal velocity as the velocity of the travelling wave. -
Numerical Modeling of Fluid Flow and Heat Transfer in a Narrow Taylor-Couette-Poiseuille System
Numerical modeling of fluid flow and heat transfer ina narrow Taylor-Couette-Poiseuille system Sébastien Poncet, Sofia Haddadi, Stéphane Viazzo To cite this version: Sébastien Poncet, Sofia Haddadi, Stéphane Viazzo. Numerical modeling of fluid flow and heat transfer in a narrow Taylor-Couette-Poiseuille system. International Journal of Heat and Fluid Flow, Elsevier, 2010, 32, pp.128-144. 10.1016/j.ijheatfluidflow.2010.08.003. hal-00678877 HAL Id: hal-00678877 https://hal.archives-ouvertes.fr/hal-00678877 Submitted on 14 Mar 2012 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Numerical modeling of fluid flow and heat transfer in a narrow Taylor-Couette-Poiseuille system S¶ebastienPoncet,¤ So¯a Haddadi,y and St¶ephaneViazzoz Laboratoire M2P2, UMR 6181 CNRS - Universit¶ed'Aix-Marseille - Ecole Centrale Marseille, IMT la Jet¶ee,38 rue Joliot-Curie, 13451 Marseille (France) (Dated: February 17, 2010) We consider turbulent flows in a di®erentially heated Taylor-Couette system with an axial Poiseuille flow. The numerical approach is based on the Reynolds Stress Modeling (RSM) of Elena and Schiestel [1, 2] widely validated in various rotor-stator cavities with throughflow [3{5] and heat transfer [6]. -
Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD
entropy Article Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD N. Ameer Ahammad 1 , Irfan Anjum Badruddin 2,* , Sarfaraz Kamangar 2, H.M.T. Khaleed 3, C. Ahamed Saleel 2 and Teuku Meurah Indra Mahlia 4,* 1 Department of Mathematics, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia; [email protected] 2 Mechanical Engineering Department, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia; [email protected] (S.K.); [email protected] (C.A.S.) 3 Department of Mechanical Engineering, Faculty of Engineering, Islamic University of Madinah, Madinah Munawwarra 42351, Saudi Arabia; [email protected] 4 Centre of Green Technology, Faculty of Engineering and Information Technology, University of Technology, Sydney, NSW 2007, Australia * Correspondence: [email protected] (I.A.B.); [email protected] (T.M.I.M.) Abstract: This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is Citation: Ahammad, N.A.; analyzed with respect to various parameters, including the Brinkman number and Reynolds number. Badruddin, I.A.; Kamangar, S.; It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but Khaleed, H.M.T.; Saleel, C.A.; Mahlia, increases with the radiation parameter. -
Evaluation of the Cavitation Effect on Liquid Fuel Atomization by Numerical Simulation
Korean J. Chem. Eng., 35(11), 2164-2171 (2018) pISSN: 0256-1115 DOI: 10.1007/s11814-018-0141-6 eISSN: 1975-7220 INVITED REVIEW PAPER INVITED REVIEW PAPER Evaluation of the cavitation effect on liquid fuel atomization by numerical simulation Sang In Choi*, Jia Ping Feng*, Ho Suk Seo**, Young Min Jo*,†, and Hyun Chang Lee*** *Department of Applied Environmental Science, Kyung Hee University, Yongin 17104, Korea **EG Power Tech Co., Ltd., Suwon 16229, Korea ***Dept. of Mechanical Design, Kangwon National University, Samcheok 25913, Korea (Received 16 February 2018 • accepted 16 August 2018) AbstractHeavy duty diesel vehicles deteriorate urban air quality by discharging a large volume of air pollutants such as soot and nitrogen oxides. In this study, a newly introduced auxiliary device a fuel activation device (FAD) to improve the combustion efficiency of internal engines by utilizing the cavitation effect was closely investigated by the fluid flow mechanism via a numerical analysis method. As a result, the FAD contributed to fuel atomization from the injection nozzle at lower inlet pressure by reducing the pressure energy. The improved cavitation effect facilitated fuel atomization, and ultimately reduced pollutant emission due to the decrease in fuel consumption. The axial velocity along the flow channel was increased 8.7 times with the aid of FAD, which improved the primary break-up of bubbles. The FAD cavitation effect produced 1.09-times larger turbulent bubbles under the same pressure and fuel injection amount than without FAD. Keywords: Diesel Engine, Fuel Activation Device, Cavitation, Cavitation Number, CFD INTRODUCTION was determined by an atomization effect. The smaller the droplets, the total number of droplets increases. -
University of Nevada, Reno a Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philo
University of Nevada, Reno Computational Investigation of Cavitation Performance and Heat Transfer in Cryogenic Centrifugal Pumps with Helical Inducers A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering by Enver Sinan Karakas Dr. Cahit A. Evrensel/Dissertation Advisor May, 2019 THE GRADUATE SCHOOL We recommend that the dissertation prepared under our supervision by Entitled be accepted in partial fulfillment of the requirements for the degree of , Advisor , Committee Member , Comm ittee Member , Committee Member , Graduate School Representative David W. Zeh, Ph.D., Dean, Graduate School i i. ABSTRACT In this dissertation, heat transfer and cooling mechanism of a cryogenic submerged pump motor, and cavitation behavior of a cryogenic pump are investigated. Cryogenic pumps for Liquefied Natural Gas (LNG) applications are unique in design with respect other industrial pump applications. The two distinct features of the cryogenic pumps are: (1) pump motor is submerged to process liquid for improved cooling, and (2) a helical style inducer is utilized at the suction side of the pump to enhance the cavitation performance. The first part of this dissertation investigates the cooling of the submerged induction motor considering normal operating conditions of a typical cryogenic pump to understand the effect of the motor rotor geometry. In this effort, the flow structure across the motor annulus, which is commonly known as “motor air gap”, is investigated in the presence of realistic rotor geometries commonly found in practical applications. The purpose of this study is to observe and understand the fluid dynamics of Taylor-Couette-Poiseuille (TCP) flow and its significance to the cooling performance of the submerged motor, considering various configurations of the rotor surface. -
Experiments on Rayleigh–Bénard Convection, Magnetoconvection
J. Fluid Mech. (2001), vol. 430, pp. 283–307. Printed in the United Kingdom 283 c 2001 Cambridge University Press Experiments on Rayleigh–Benard´ convection, magnetoconvection and rotating magnetoconvection in liquid gallium By J. M. AURNOU AND P. L. OLSON Department of Earth and Planetary Sciences,† Johns Hopkins University, Baltimore, MD 21218, USA (Received 4 March 1999 and in revised form 12 September 2000) Thermal convection experiments in a liquid gallium layer subject to a uniform rotation and a uniform vertical magnetic field are carried out as a function of rotation rate and magnetic field strength. Our purpose is to measure heat transfer in a low-Prandtl-number (Pr =0.023), electrically conducting fluid as a function of the applied temperature difference, rotation rate, applied magnetic field strength and fluid-layer aspect ratio. For Rayleigh–Benard´ (non-rotating, non-magnetic) convection 0.272 0.006 we obtain a Nusselt number–Rayleigh number law Nu =0.129Ra ± over the range 3.0 103 <Ra<1.6 104. For non-rotating magnetoconvection, we find that the critical× Rayleigh number× RaC increases linearly with magnetic energy density, and a heat transfer law of the form Nu Ra1/2. Coherent thermal oscillations are detected in magnetoconvection at 1.4Ra∼C . For rotating magnetoconvection, we find that the convective heat transfer is∼ inhibited by rotation, in general agreement with theoretical predictions. At low rotation rates, the critical Rayleigh number increases linearly with magnetic field intensity. At moderate rotation rates, coherent thermal oscillations are detected near the onset of convection. The oscillation frequencies are close to the frequency of rotation, indicating inertially driven, oscillatory convection.