Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
11
1-2
2019
PREFACE: ADVANCES IN COMPUTATIONAL HEAT TRANSFER (CHT-17)
v-vi
10.1615/ComputThermalScien.v11.i1-2.10
Oronzio
Manca
Dipartimento di Ingegneria Industriale e dell'Informazione, Università degli
Studi della Campania "Luigi Vanvitelli," Aversa (CE), Italy
Yogesh
Jaluria
Department of Mechanical and Aerospace Engineering Rutgers-New Brunswick, The State University of New Jersey Piscataway, NJ 08854, USA
EFFECT OF GAS FLOW DIRECTION ON PASSIVE SUBSEA COOLER EFFECTIVENESS
1-16
10.1615/ComputThermalScien.2018024704
Nikolay G.
Ivanov
Peter the Great St.Petersburg Polytechnic University, Polytechnicheskaya 29, St.Petersburg, 195251, Russia
Vladimir V.
Ris
Peter the Great St.Petersburg Polytechnic University, Polytechnicheskaya 29, St.Petersburg, 195251, Russia
Nikolay A.
Tschur
Peter the Great St.Petersburg Polytechnic University, Polytechnicheskaya 29, St.Petersburg, 195251, Russia
Marina A.
Zasimova
Peter the Great St.Petersburg Polytechnic University, Polytechnicheskaya 29, St.Petersburg, 195251, Russia
tube bank
buoyancy effects
draft effect
conjugate heat transfer
unsteady flow
numerical modeling
The goal of the study is to evaluate the thermohydraulic characteristics of a passive buoyancy-dominated heat exchanger aimed at subsea processing of natural gas produced. The 3D unsteady buoyancy-induced water flow through a staggered tube bank at the Grashof number of 3 × 105 is simulated using the full Navier-Stokes equations with no turbulence model. Direct numerical simulation of the external draft flow is combined with the simultaneous unsteady Reynolds-averaged Navier-Stokes modeling of the internal natural gas flow in plain serpentine pipes at Re = 8 × 105
and simulation of heat conduction through the massive steel pipe wall. The paper compares water flow and external
heat transfer characteristics for two cross-flow cooler configurations with the downward and upward internal gas flow
that correspond to the counterflow and the parallel-flow heat exchanger schemes. It was found that though there is
a pronounced difference in the local characteristics of external heat transfer and water flow, in general the gas flow
direction does not influence the cooler effectiveness; the total heat output values for both schemes considered are almost the same. The computational fluid dynamics data are in accordance with the effectiveness-number of transfer units method analysis performed using the water mass flow rate based on the volume-averaged draft velocity. The conclusion is that the cooler performance does not depend on the inlet and outlet collector location that gives some freedom in cooler design.
PYROELECTRIC EFFECT CONTROL: DESIGN, FABRICATION, AND CHARACTERIZATION OF A MICROHEATERS ARRAY FOR BIOMEDICAL APPLICATIONS
17-28
10.1615/ComputThermalScien.2018024691
S.
Bhowmick
Shilps Sciences Private Limited, Bangalore, India
Orlando
Leo
Department of Industrial Engineering, University of Naples Federico II, Napoli, Italy
Giuseppe
Coppola
Institute for Microelectronics and Microsystems, CNR, Napoli, Italy
Mariano
Gioffrè
Institute for Microelectronics and Microsystems, CNR, Napoli, Italy
Marilena
Musto
Department of Industrial Engineering, University of Naples Federico II, Napoli, Italy
Giuseppe
Rotondo
Department of Industrial Engineering, University of Naples Federico II, Napoli, Italy
Mario
Iodice
Institute for Microelectronics and Microsystems, CNR, Napoli, Italy
pyroelectric fields
lithium niobate
Joule effect
thermal effect analysis
An innovative microheater array design is realized on a lithium niobate crystal, to induce a uniform pyroelectric effect on an area of 12.5 × 12.5 mm2. Thermal analyses of the device were performed both experimentally and numerically using a FLIR thermocamera and COMSOLTM Multiphysics.A series of preliminary numerical simulations were carried out to obtain the optimized design of the aforementioned specifications. The microheaters were fabricated on the + Z surface of the lithium niobate crystal using a photolithography process followed by titanium thin-film deposition. We performed on this device a series of electrothermal characterizations; the results of the measurements showed good agreement with the numerical model in terms of heat distribution, accomplishing a comparison between the thermal maps coming from the two methodologies.
NUMERICAL MASS TRANSFER STUDIES IN CASE OF CONVECTIVE FLOWS OCCURRENCE IN ISOTHERMAL TERNARY GAS MIXTURES
29-39
10.1615/ComputThermalScien.2018024724
Vladimir
Kossov
Institute of Experimental and Theoretical Physics
Dauren B.
Zhakebayev
Departament of Mathematical and computer modelling, Kazakh National University named after al- Farabi, al-Farabi 71, 050012 Almaty, Kazakhstan
Olga V.
Fedorenko
Institute of Experimental and Theoretical Physics, Kazakh National University named after al-Farabi, al-Farabi 71, 050038, Almaty, Kazakhstan
diffusion
convection
mixtures
pressure
instability
structures
Isothermal diffusion mixing in multicomponent gas mixtures at various pressures is studied numerically in He + Ar
– N2 and CH4 + Ar – N2. It is shown that in systems where the diffusion coefficients differ significantly from each other, nonlinear distributions of the concentrations of the components arise with increasing pressure, which leads to a nonmonotonous density distribution of the gas mixture in the computational domain. The resulting nonlinearity is the cause of the formation of convective structured flows. The transition from the diffusion to the convective regime
is characterized by a significant increase in the average mixing rate. The dynamics of the development of convective
currents and their structure is investigated.
STUDY OF EFFECT OF MOLECULAR PRANDTL NUMBER, TRANSPIRATION AND LONGITUDINAL PRESSURE GRADIENT ON FLOW AND HEAT TRANSFER CHARACTERISTICS IN BOUNDARY LAYERS
41-49
10.1615/ComputThermalScien.2018024497
Alexander I.
Leontiev
Institute of mechanics of Lomonosov Moscow State University, 1 Michurinski pr., Moscow 119192, Russia; Bauman Moscow State Technical University, ul. Baumanskaya 2-ya, 5/1, Moscow 105005, Russia
Valerii G.
Lushchik
"Energomash" Science and Production Association, M. V. Keldysh Research Center, Institute of mechanics of Lomonosov Moscow State University, Michurinsky prospect 1, 119192, Moscow, Russia
Mariia S.
Makarova
Institute of Mechanics, Lomonosov Moscow State University, Moscow, Russia
turbulent Prandtl number
differential turbulence model
injection
suction
pressure gradient
A numerical modeling of a subsonic flow at a permeable plate in the presence of a flow pressure gradient is carried
out using a differential turbulence model, supplemented with the transport equation for the turbulent heat flux. The
dependences of the turbulent Prandtl number and other turbulent flow and heat transfer characteristics from the
molecular Prandtl number, injection (suction) intensity of the gas through the permeable wall, and the acceleration
parameter of the flow are presented. Air and mixtures of helium with xenon and argon are selected as the gas heat
carriers and mercury, water, and transformer oil are selected as the liquid heat carriers, respectively. The effect of the variability of the turbulent Prandtl number on heat transfer characteristics, in particular, on the Nusselt number, is studied. It is shown that the difference of the Nusselt number obtained in the condition of the constant turbulent Prandtl number from the results obtained in the calculations with the equation for the turbulent heat flux increases under low and high molecular Prandtl number. The injection, suction, and pressure gradient also increase this difference and also lead to a substantial violation of the Reynolds analogy.
SIMPLIFICATION STUDY OF A KIND OF COMPOSITE STRUCTURE
51-55
10.1615/ComputThermalScien.2018024509
Bo
Chen
CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese
Academy of Sciences, Beijing 100190, China; College of Materials Science and Opto-Electronic Technology, University of Chinese Academy
of Sciences, Beijing, 101408, China
Hanze
Zhang
CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese
Academy of Sciences, Beijing 100190, China
Mingyue
Liu
CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese
Academy of Sciences, Beijing 100190, China
Ning
Li
Key laboratory of microwave remote sensing, Chinese Academy of Sciences, Beijing, 100190, China; National Space Science Center, Chinese Academy of Sciences, Beijing, 100190, China
Xue
Chen
CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese
Academy of Sciences, Beijing 100190, China
Heguang
Liu
CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese
Academy of Sciences, Beijing 100190, China
thermal simulation
antenna
composite
carbon fiber and aluminium honeycomb
finite element analysis
In this paper, the thermal simplification of the surface of a satellite borne microwave antenna of a kind of sandwich
composite of carbon fiber and aluminium honeycomb is discussed. For this kind of composite, it is necessary to do some simplification when doing the thermal analysis. A uniform unit repeatedly was obtained and the equivalent thermal parameters such as thermal conductivity and heat capacity were computed. The influences of simplification methods on the thermal results and computation speed were contrasted and discussed.
TWO TYPES OF HEAT EXCHANGERS FOR OFFICE BUILDINGS IN DIFFERENT EUROPEAN CLIMATES
57-67
10.1615/ComputThermalScien.2018024508
Diana
D'Agostino
University of Naples Federico II, Department of Industrial Engineering, Piazzale Tecchio, 80, 80125 Napoli, Italy
Concetta
Marino
University of Naples Federico II, Department of Industrial Engineering, Piazzale Tecchio, 80, 80125 Napoli, Italy
Francesco
Minichiello
University of Naples Federico II, Department of Industrial Engineering, Piazzale Tecchio, 80, 80125 Napoli, Italy
Francesco
Russo
Engineer, freelance
air-to-air heat exchangers
earth-to-air heat exchangers
office building
energy analysis
dynamic simulation
discounted payback
This paper investigates air-to-air (AAHX) and earth-to-air (EAHX) heat exchangers, to reduce the energy requirements
of air conditioning systems for office buildings. The AAHX considered is of static type with a partition wall and
allows recovering both sensible and latent heat. The EAHX technology exploits the capability of the ground as energy
storage, through a system of earthed air ducts laid horizontally. In summer, the ground usually presents temperatures lower than outside ventilation air temperatures, while in winter it could have, in some hours/days, a temperature higher than the outside air. Three European cities are considered: Palermo (southern Italy), with mild winters and very hot summers; Milan (northern Italy), with cold winters and hot summers; Berlin (Germany), with very cold winters and quite hot summers. The analysis is performed by means of EnergyPlus, a dynamic building energy simulation software, with reference to the same, newly designed office building, with or without heat recovery systems. The air conditioning system is based on fan-coils and primary air, and the EAHX (or the AAHX) is inserted in the first part of the primary air-handling unit. The research shows that in winter the use of the AAHX reduces the energy requirement much more than the EAHX, while in summer the EAHX is preferable. Moreover, the annual analysis shows that the use of the EAHX is more convenient in hot climates. The case of coupled heat exchangers (AAHX + EAHX) is also investigated. The evaluated discounted payback is about 6–9 years for the EAHX (3–5 years if an incentive of 20% is considered) and 1–3 years for the AAHX (less than 1 year with the incentive).
NUMERICAL THERMAL NON-EQUILIBRIUM APPROACH OF NATURAL CONVECTION IN A SQUARE POROUS CAVITY WITH NON-UNIFORM HEATING ON ONE SIDEWALL
69-80
10.1615/ComputThermalScien.2018024737
Abdeslam
Omara
Université Frères Mentouri Constantine 1
Said
Abboudi
Laboratoire Interdisciplinaire Carnot de Bourgogne, ICB UMR 6303 CNRS, Université
Bourgogne Franche Comté (UBFC), UTBM, site de Sévenans 90010 Belfort cedex, France
non-uniform heating
non-Darcy Brinkman–Forchheimer model
numerical approach
local thermal non-equilibrium model
Numerical results of two-dimensional steady natural convection in a square cavity filled with porous medium by adopting a two-temperature model of heat transfer are presented. The left wall is linearly heated (by increasing or decreasing the wall temperature); the right wall is uniformly cooled while the horizontal top and bottom walls are considered insulated. A developed program (based on the finite-volume method and the semi-implicit method for pressure-linked equations algorithm) was utilized to numerically solve the governing Navier–Stokes equations with the associated boundary conditions. The controlling parameters on the fluid flow and heat transfer for this investigation are the interphase heat transfer coefficient (H), porosity-scaled conductivity ratio (γ), Rayleigh number (Ra), and Darcy number (Da) at Pr = 0.70.
THERMO-HYDRAULIC NETWORK MODEL FOR PASSIVE COOLING OF A SUBSEA VARIABLE-SPEED DRIVE
81-93
10.1615/ComputThermalScien.2018024517
Thomas B.
Grandinger
ABB Switzerland Ltd., Corporate Research, Baden-Dättwil, Switzerland
Tor
Laneryd
ABB Sweden Ltd., Corporate Research, Västerås, Sweden
numerical simulation
natural convection
power converter
subsea electrification
Subsea factories are expected to play an important role in future oil production. Cooling of the necessary power converters in a deep-sea environment is a great challenge. Because of their high reliability, passive cooling systems that rely on natural convection of the oil within the converter tank and the seawater around it are preferred. In this paper, we present a numerical code for one-dimensional (1D) network models of natural-convection cooling specifically developed for subsea converters. Network elements are provided to model converter components such as semiconductor modules mounted on oil-cooled heat sinks. For spatial discretization, the finite-volume method is used, and the resulting set of nonlinear equations is solved in MATLAB. Measurements of natural-convection cooling of semiconductor heat sinks immersed in an oil-filled tub are presented, and 1D network models are set up to simulate this case. The numerical convergence is verified and the temperatures are compared. The comparison yields the first experimental confirmation of the model and demonstrates the importance of buoyancy corrections in the flow between the fins of heat sinks. Further experiments will be needed to gain experience with the model and refine it as necessary.
HYPO- AND HYPERTHERMIA EFFECTS ON LDL DEPOSITION IN A CURVED ARTERY
95-103
10.1615/ComputThermalScien.2018024754
Marcello
Iasiello
Dipartimento di Ingegneria Industriale, Università degli studi di Napoli Federico II, P.le Tecchio 80, 80125, Napoli, Italy
Kambiz
Vafai
Department of Mechanical Engineering, University of California, Riverside, CA 92521-0425 USA
Assunta
Andreozzi
Dipartimento di Ingegneria Industriale, Università degli studi di Napoli Federico II, P.le Tecchio 80, 80125, Napoli, Italy
Nicola
Bianco
Dipartimento di Ingegneria Industriale, Università degli studi di Napoli Federico II, P.le Tecchio 80, 80125, Napoli, Italy
low-density lipoprotein (LDL) deposition
multilayer model
curved artery
hypo- and
hyperthermia
Low-density lipoprotein (LDL) deposition within the walls of an artery causes the growth of an atherosclerotic plaque,
which can cause serious health issues. Various physical phenomena affect this aspect, for example, induced temperature gradients, which cause particle movement due to thermodiffusion. In this work, the effects of hypo- and hyperthermia on a curved artery are investigated. The heat source/sink is applied from the interior side of the artery (the lumen side). The curvature effect of the artery is taken into account through variation of the arterial curvature ratio, while a multilayer model that takes into account the heterogeneity of various layers represents the wall. Navier–Stokes and convection–diffusion equations are employed for the LDL transport through the lumen, while Darcy–Brinkman, Staverman–Kedem–Katchalsky with a reaction term, and the energy equation are used to study the wall layers. Results are presented for shear rates, temperature, and LDL profiles. It is shown that the artery curvature has a negligible effect on LDL deposition when a heat source/sink, under hypo- or hyperthermia conditions is applied from the lumen side.
STUDY OF PARTIAL SLIP MECHANISM ON FREE CONVECTION FLOW OF VISCOELASTIC FLUID PAST A NONLINEARLY STRETCHING SURFACE
105-117
10.1615/ComputThermalScien.2018024728
Gauri
Seth
Indian Institute of Technology (ISM), Dhanbad
A.
Bhattacharyya
Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand-826004, India
Manoj Kumar
Mishra
VIT-AP University, Amaravati, Andhra Pradesh-522237, India
MHD
viscoelastic fluid
stretching sheet
velocity Slip
finite element method
The investigation of simultaneous impact of Soret and Dufour effects on two-dimensional magnetohydrodynamic free
convective flow of an electrically conducting, viscous, and incompressible viscoelastic fluid over a nonlinearly stretching surface with Navier's partial velocity slip boundary condition is carried out. With the help of similarity transformation, the governing flow equations; then the Galerkin finite element method (FEM) is incorporated to obtain the approximate solution of the transformed equations. Computations for fluid velocity, fluid temperature distribution, and species concentration along with skin friction coefficient, Nusselt number, and Sherwood number are carried out for a range of values of pertinent flow parameters. An outstanding agreement is found when we compare our results with the exact solution of previously published research articles. Noteworthy findings of the present study include that nonlinearity in the stretching surface as well as the viscoelastic nature of the fluid exhibit a retarding tendency on the fluid velocity, temperature, and concentration.
HYPO- AND HYPERTHERMIA EFFECTS ON MACROSCOPIC FLUID TRANSPORT IN TUMORS
119-130
10.1615/ComputThermalScien.2018024802
Assunta
Andreozzi
Dipartimento di Ingegneria Industriale, Università degli studi di Napoli Federico II, P.le Tecchio 80, 80125, Napoli, Italy
Marcello
Iasiello
Dipartimento di Ingegneria Industriale, Università degli studi di Napoli Federico II, P.le Tecchio 80, 80125, Napoli, Italy
Paolo
Netti
Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli
Studi di Napoli Federico II, Napoli, Italy
fluid flow and mass transport in biological systems
thermo-poroelasticity theory
hypoand hyperthermia
numerical analysis
Combining the effects of transvascular and interstitial fluid movement with the structural mechanics of a tissue is necessary to properly analyze processes such as nutrient transport in a tumor cell. Furthermore, externally induced heat loads can play a role: for example, cryoablation can be performed by means of hypothermia and hyperthermia can be
induced in order to treat some kinds of tumors such as liver tumor. Recently, the study of the effects of hypo- and hyperthermia on fluid flow and mass transport in biological systems by considering the fluid–structure interaction has gained researchers' attention. In this paper, fluid flow in a tumor mass is analyzed at the macroscopic scale by considering the effects of both solid tissue deformation and temperature via hypo- and hyperthermia. Governing equations are averaged over a representative elementary volume of the living tissue, and written by means of the thermo-poroelasticity theory. Darcy's law is used to describe fluid flow through the interstitial space, while transvascular transport is described with a generalized Starling's law. The effects of hypo- and hyperthermia on the living tissue are included with a source term in the tissue momentum equation that considers thermal expansion. This term can be either negative or positive, i.e., hypo- or hyperthermia is herein considered. Governing equations with the appropriate boundary conditions are solved with the finite-element commercial code COMSOL Multiphysics in the steady-state regime. The numerical model is validated with analytical results from previously published results for an isothermal case. Results are presented in terms of pressure, velocity, and temperature fields for various thermal loads and the effects of hypo- and hyperthermia on various physical parameters are analyzed.
TURBULENT FREE CONVECTION IN A VERTICAL CHANNEL WITH ISOTHERMAL WALLS: NEW FORMULATION AND THE RESISTOR-NETWORK MODEL
131-145
10.1615/ComputThermalScien.2018021319
Sepehr
Foroushani
Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1
John L.
Wright
Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1
David
Naylor
Department of Mechanical & Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, Canada M5B 2K3
free convection
channel flow
thermal-resistor network
CFD
dQdT
The three-temperature problem of turbulent free convection of air in a vertical channel with isothermal walls is studied. An extension of the Newton law of cooling is used to formulate the problem in terms of three temperature differences, that is, without resorting to the use of some effective temperature difference. The dQdT technique was applied numerically to calculate the coefficients of this formulation. Numerical dQdT entails a baseline solution to the full set of governing equations and subsequent solutions to the linearized energy equation with perturbed boundary conditions. The low-Reynolds k-ε turbulence model was used to obtain baseline solutions that were validated against experimental data from the literature. The application of the dQdT technique to a variable-property turbulent free convection problem is discussed. Sample results are presented for different heating scenarios, flow rates, and channel aspect ratios. It is shown that the three-temperature problem can be approximated by a delta network of three convective resistances, connecting three temperature nodes representing the isothermal boundaries.
BENCHMARKS FOR THE VALIDATION OF THE HEAT TRANSFER CAPABILITIES OF ONE-DIMENSIONAL SYSTEM CODES
147-160
10.1615/ComputThermalScien.2018024378
Charl G. Jat
Du Toit
School of Mechanical and Nuclear Engineering, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
N. I.
Tak
Korea Atomic Energy Research Institute, Deajeon, Korea
Peter F.
Niemand
School of Mechanical and Nuclear Engineering, North-West University, Potchefstroom, South
Africa
M. H.
Kim
Korea Atomic Energy Research Institute, Deajeon, Korea
convection heat transfer
radiation heat transfer
conduction heat transfer
forced convection
mixed convection
free convection
The purpose of the reactor cavity cooling system in a nuclear plant is to effectively remove the heat released by the reactor pressure vessel. The reactor cavity cooling system must be able to operate safely in a natural or passive manner, particularly in the case of very high-temperature reactors in order to avoid accidents due to human error or the failure of components. Radiation, convection, and conduction heat transfer, as well as natural circulation, are the major natural phenomena that determine the performance of a reactor cavity cooling system. System codes are often used to simulate the operation of a reactor cavity cooling system under various conditions. It is important that the codes should be verified and validated. This is achieved by performing carefully controlled experiments and selecting suitable analytical examples. The experiments and analytical examples are modeled using the codes, and the simulation results obtained by the codes are then compared with the corresponding experimental and analytical results. This paper is concerned with two benchmark problems for which the analytical solutions can be obtained and used to validate the heat transfer capability of systems codes to model conduction, radiation, and convection. The systems codes GAMMA+ and Flownex are employed to demonstrate the application of the benchmark problems.
ANALYSIS OF RADIATIVE TRANSFER IN BODY-FITTED AXISYMMETRIC GEOMETRIES WITH BAND MODELS AND ANISOTROPIC SCATTERING
161-176
10.1615/ComputThermalScien.2018021506
Rahul
Yadav
Department of Mechanical Engineering, Indian Institute of Technology Madras,
Chennai-600036, India
Chakravarthy
Balaji
Heat Transfer and Thermal Power Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
S. P.
Venkateshan
Department of Mechanical Engineering, Indian Institute of Information Technology, Design
and Manufacturing, Kancheepuram-600127, India
radiative transfer
body-fitted geometries
SLW model
anisotropic scattering
The problem of radiation heat transfer in divergent nozzles and diffusers is of real practical importance. The correct
estimation of the radiative heating at the walls of these enclosures requires appropriate treatment of the spectrally dependent properties of the participating medium like absorption and scattering, along with a handle on high temperature gradients. The present study aims to apply the spectral line-based weighted sum of gray gases (SLW) model (Denison and Webb, 1993b) to body-fitted axisymmetric geometries like truncated cone-type enclosures, which resemble gradually expanding diffusers, rocket exhaust nozzles, and typical industrial combustors that find wide engineering use. A modification of the discrete ordinates method (Baek and Kim, 1997b) has been employed to solve the radiative transfer equation. A mixture of three gases (viz. CO2, H2O, and CO) has been considered and its spectral behavior is modeled using the SLW band model. Different particle loadings are incorporated and anisotropic scattering is modeled using transport approximation (Dombrovsky, 2012). A general purpose code, SLDOM (discrete ordinates method with SLW
model), has been developed to handle these complexities of the problem. After a rigorous validation, a detailed analysis of the radiative heat fluxes at the curved wall is made under the influence of variable gas and particle concentrations with high temperature gradients. The results obtained show a strong dependence of radiative heat fluxes on particle concentration. Among gases, H2O concentration was found more critical than other gases.
THE NON-BOUSSINESQ ALGORITHM FOR HIGH TEMPERATURE GRADIENT THERMOBUOYANT FLOWS WITH MAGNETIC FIELD
177-187
10.1615/ComputThermalScien.2018024727
Mukesh
Kumar
Department of Mechanical Engineering, Indian Institute of Technology Guwahati, India
Ganesh
Natarajan
Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781039, India
magnetic field
finite volume method
staggered/non-staggered
non-Boussinesq
We propose a numerical framework to solve thermobuoyant flows in enclosures with large temperature differences under the influence of an applied magnetic field. The solution methodology is based on a staggered/nonstaggered finite volume framework which is modified to solve quasiincompressible flows with heat transfer. The present framework solves a single equation for normal momentum at the face wherein a second-order convection scheme and central differencing is adopted for the convective and viscous term, respectively. An implicit solution approach which is first order accurate in time is employed, and the resulting nonlinear system of equations is solved using the Newton-Krylov approach. The momentum field at the cell centroids is reconstructed using an iterative-defect-correction approach. The energy conservation equation is discretized as in a collocated framework, with a first-order upwind scheme for the convective terms and central differencing for viscous terms, in conjunction with implicit Euler time stepping. Thus the equation is linearized by considering the velocity field at the latest available time step, and the resulting linear system of equations is solved, using an incomplete LU (ILU) preconditioned GMRES solver. The proposed approach is, however, still pressure based, but the energy equation is employed to derive the divergence constraint to be used for solution of the pressure correction equation. This leads to a nonsolenoidal velocity field with a variable coefficient poisson equation, which is also efficiently solved using an ILU preconditioned GMRES solver. Validation studies for small and large temperature differences under the action of imposed magnetic field are carried out to ascertain the applicability of the approach. Finally, investigations of magnetohydrodynamic thermobuoyant flow in an enclosure with a heat obstacle are conducted with a view to understand the effect of magnetic field and heat transfer.