Begell House Inc.
Computational Thermal Sciences: An International Journal
CTS
1940-2503
4
6
2012
PREFACE: FIFTH INTERNATIONAL SYMPOSIUM ON COMPUTATIONAL HEAT TRANSFER KEYNOTE LECTURES
0
10.1615/ComputThermalScien.v4.i6.10
Graham
de Vahl Davis
University of New South Wales, Kensington, NSW, Australia
D. Andrew S.
Rees
Department of Mechanical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
LASER INDUCED HYPERTHERMIA OF SUPERFICIAL TUMORS: A TRANSIENT THERMAL MODEL FOR INDIRECT HEATING STRATEGY
457-475
10.1615/ComputThermalScien.2012006531
Victoria
Timchenko
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney 2052, Australia
Leonid A.
Dombrovsky
Joint Institute for High Temperatures, 17A Krasnokazarmennaya Str., Moscow,
111116, Russia; Tyumen State University, 6 Volodarsky Str., Tyumen, 625003, Russia
hyperthermia
superficial tumors
radiative transfer
transient heat transfer in human body
An indirect heating strategy based on laser irradiation of surrounding tissues as an alternative to a direct irradiation of superficial tumors is presented in this paper. The computational analysis is based on two-dimensional axisymmetric models for both radiative transfer and transient heat transfer in a human body Coupled transient energy equations for composite human tissue take into account the metabolic heat generation and heat conduction, blood perfusion through capillaries, the volumetric heat transfer between arterial blood and ambient tissue, the periodic laser heating, and also heat transfer between the human body and ambient medium. The relative role of the treatment parameters on the transient temperature field and degree of thermal conversions in human tissues has been studied by solving an example problem for a superficial human cancer with and without embedded gold nanoshells. The thermal conversions in blood and tumor tissue as a response to hyperthermia are estimated by solving Arrhenius-type kinetic equations. It is shown that required parameters for hyperthermia treatment can be attained without gold nanoshells.
A ROLE FOR COMPUTATIONAL HEAT TRANSFER (CHT) IN ENGINEERING EDUCATION
477-484
10.1615/ComputThermalScien.2012006430
Dudley Brian
Spalding
Concentration, Heat, and Momentum (CHAM), Limited, Bakery House, 40 High Street, Wimbledon Village, London SW19 5AU, England
education
heat exchangers
shell and tube
SimScene
computational heat transfer (CHT)
computational fluid dynamics (CFD)
Traditional engineering education has two main aspects, theoretical and experimental; of which the first also has two parts: quantitative formulation of the relevant general laws of science; and deduction of their implications, in particular, practical circumstances. The deductions are conducted by mathematical methods in which differential calculus plays a large part. Students lacking proficiency in such methods are not admitted to engineering schools. Differential calculus applies the laws of science to infinitesimal volumes, and it expresses its deductions in terms of pretabulated functions. Only rarely does reality conform to them well enough for use in design, without large safety factors. Computer-based analysis applies the laws to finite volumes with fewer oversimplifications. Its deductions conform to reality more closely; so safety factors can be closer to unity; with great economic advantage. It is argued that these facts should be reflected in both the admission procedures and the teaching methods of engineering education. In respect to the second, detailed suggestions are made, exemplified by application to heat-exchanger theory.
DROPLET HEATING AND EVAPORATION−RECENT RESULTS AND UNSOLVED PROBLEMS
485-496
10.1615/ComputThermalScien.2012006265
Sergei S.
Sazhin
Advanced Engineering Centre, School of Computing, Engineering and Mathematics,
University of Brighton, Brighton, BN2 4GJ, UK
Morgan R.
Heikal
Advanced Engineering Centre, School of Computing, Engineering and Mathematics,
University of Brighton, Brighton, BN2 4GJ, UK
droplet
heating
evaporation
kinetic modeling
Recently developed approaches to the hydrodynamic, kinetic, and molecular dynamic modeling of fuel droplet heating and evaporation are reviewed. Two new solutions to the heat conduction equation, taking into account the effect of the moving boundary during transient heating of an evaporating droplet, are discussed. The first solution is the explicit analytical solution to this equation, while the second one reduces the solution of the differential transient heat conduction equation to the solution of the Volterra integral equation of the second kind. The new approach predicts lower droplet surface temperatures and slower evaporation rates compared with the traditional approach. An alternative approach to the same problem has been based on the assumption that the time evolution of a droplet's radius, Rd (t), is known. For sufficiently small time steps, the time evolutions of droplet surface temperatures and radii predicted by both approaches coincide. A simplified model for multi-component droplet heating and evaporation, based on the analytical solution to the species diffusion equation inside droplets, is discussed. Two new solutions to the equation, describing the diffusion of species during multi-component droplet evaporation taking into account the effects of the moving boundary, are presented. A quasi-discrete model for heating and evaporation of complex multi-component hydrocarbon fuel droplets is described. The predictions of the model, taking into account the effects of the moving boundary during the time steps on the solutions to the heat transfer and species diffusion equations, are discussed. A new algorithm, based on simple approximations of the kinetic results, suitable for engineering applications, is discussed. The results of kinetic modeling, taking into account the effects of inelastic collisions, and applications of molecular dynamics simulations to study the evaporation of n-dodecane droplets are briefly summarized. The most challenging and practically important unsolved problems with regard to the modeling of droplet heating and evaporation are summarized and discussed.
ZONAL RANS-LES MODELING FOR TURBINES IN AEROENGINES
497-506
10.1615/ComputThermalScien.2012006402
Paul G.
Tucker
Fluid Dynamics Research Centre, School of Engineering, The University of Warwick, Coventry; Whittle laboratory, University of Cambridge, UK
R.
Jefferson-Loveday
Whittle Laboratory, University of Cambridge, Cambridge, CB3 0DY United Kingdom
James
Tyacke
Whittle Laboratory, University of Cambridge, Cambridge, CB3 0DY United Kingdom
V. Nagabhushana
Rao
Whittle Laboratory, University of Cambridge, Cambridge, CB3 0DY United Kingdom
LES
RANS
hybrid
zonal
turbine
The cost of large-eddy simulation (LES) modeling in various zones of gas turbine aeroengines is outlined. This high cost clearly demonstrates the need to perform hybrid Reynolds-averaged Navier-Stokes-LES (RANS-LES) over the majority of engine zones because the Reynolds number is too high for pure LES. The RANS layer is used to cover over the fine streaks found in the inner part of the boundary layer. The hybrid strategy is applied to various engine zones, which is shown to typically give much greater predictive accuracy than pure RANS simulations. However, the cost estimates show that the RANS layer should be disposed within the low-pressure turbine zone. Also, the nature of the flow physics in this zone makes LES most sensible.
LEVEL-SET METHOD FOR MULTIPHASE FLOWS
507-515
10.1615/ComputThermalScien.2012006412
Y F
Yap
Department of Mechanical Engineering, The Petroleum Institute, Abu Dhabi, United Arab Emirates
John C.
Chai
Department of Engineering and Technology, School of Computing and Engineering, University of Huddersfield, Huddersfield, HD1 3DH, UK; The Petroleum Institute, Department of Mechanical Engineering
Abu Dhabi, United Arab Emirates
level set
two-phase flow
finite-volume method
This article presents a single-fluid formulation to model multiphase flows using the level-set method. The formulation is generic in the sense that additional physics involving heat and mass transfer can be incorporated easily. For demonstration purposes, the finite-volume method is used to discretize the governing equations. Two examples are presented to showcase the present approach.
THE FUTURE OF CFD AND THE CFD OF THE FUTURE
517-524
10.1615/ComputThermalScien.2012006511
Akshai K.
Runchal
Analytic & Computational Research, Inc, Los Angeles, CA 90077;
CFD Virtual Reality Institute, Dharamsala, HP, India 176219
CFD
history of CFD
future of CFD
computational technology
engineering virtual reality
Imperial College
Los Alamos National Laboratory
CFD is undergoing a rapid evolution. The distinction between CFD and the so called Structural FE codes is disappearing. Solids and plastics are already being viewed as special subsets of fluids and eventually the structural and fluid codes will merge together and evolve as multi-physics design tools. The algorithmic advancements will have to include a much stronger emphasis on rheology, fluid structure interaction and physics that includes the complete spectrum of solids, plastics, liquids, gases and other phases in-between. A second evolution is occurring in computer architecture. The codes of today, with a few exceptions, rely heavily on iterative matrix solvers. The algorithmic core of most of the current CFD codes was developed when the paradigm was a single CPU with limited memory or a parallel system with multiple CPUs − at the most numbered in 100 s − in a MIMD or SIMD architecture. Hence the methodology used is that adapted to such configurations. The architecture of the future will be multi-core cloud or grid-computing CPUs, GPUs or ASICs. The use of matrix solvers for such architecture will present bottlenecks associated with communication and management software. This will necessitate a new look at how to solve the governing equations and how to do so effectively within the paradigm of cloud computing. A third evolution will occur in the implementation of CFD as a design tool. Increasingly, the emphasis will shift to embedded applications so that CFD as a stand-alone tool will practically disappear. CFD as an embedded application will then merge with virtual reality tools and be included in intelligent AI type interfaces where the emphasis is on the design function of interest rather than on the CFD per se. CFD will then be part of an interactive tool such as the one for x-ray tomography or the performance analysis of an aircraft engine and, with increasing task specific embedded applications, the day is perhaps not far off when specific ASIC (Application Specific Integrated Circuits) chips may implement CFD for such applications. This will give rise to EVR (Engineering Virtual Reality) Design Tools. In summary, CFD will surely become ubiquitous but buried to such an extent that it will be rarely obvious that a CFD tool is being used. Everyone knows there is an engine in a car yet hardly anyone cares to ask what that engine is.
BUBBLE DYNAMICS DURING POOL BOILING UNDER MICROGRAVITY CONDITIONS
525-538
10.1615/ComputThermalScien.2012006423
Dean Vijay K.
Dhir
Henry Samueli School of Engineering and Applied Science, Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, USA
G. R.
Warrier
Henri Samueli School of Engineering and Applied Science, University of California, Los Angeles
Eduardo
Aktinol
Henry Samueli School of Engineering and Applied Science, University of California, Los Angeles, California, 90024-1597
bubble dynamics
heat transfer
microgravity conditions
A numerical tool has been developed over the last decade to study bubble dynamics and the associated heat transfer during nucleate pool boiling. The numerical model divides the domain of interest into micro- and macroregions. The microregion is the ultra-thin liquid layer that forms between the advancing or receding vapor−liquid interface and the solid wall. The macroregion is the vapor−liquid occupied region away from the heated wall and excluding the microregion. Lubrication theory is used for the solution of the microlayer. Complete conservation equations of mass, momentum, and energy are solved in the macroregion. A level set function is used to capture the evolving, merging, and breaking interfaces. Gravity is an important variable of the problem. Experiments at earth normal gravity, reduced gravity in the parabolic flights, and microgravity conditions on the International Space Station are used to validate the numerical results. The reduced gravity is shown to increase the length and timescales of the process. Although bubble dynamics and vapor removal processes (except the bubble size) remain the same down to one-hundredth of earth normal gravity, there is a significant change in the vapor removal pattern under microgravity conditions.
ADVANCED INDOOR HUMIDITY CONTROL: NEW IMPACTS ON CONJUGATED HEAT AND MASS TRANSFER
539-547
10.1615/ComputThermalScien.2012006413
Si-Min
Huang
Key Laboratory of Distributed Energy Systems of Guangdong Province, Department of Energy
and Chemical Engineering, Dongguan University of Technology, Dongguan 523808, People's
Republic of China
Lizhi
Zhang
South China University of Technology
conjugated heat and mass transfer
hollow fiber membrane contactor
liquid desiccant air dehumidification
counter flow
Fluid flow and conjugate heat and mass transfer in a hollow fiber membrane contactor used for air humidification are investigated. The contactor is like a shell-and-tube heat exchanger where the water stream flows in the tube side while the air stream flows in the shell side in a counter flow arrangement. To overcome the difficulties in direct modeling of the whole contactor a representative cell comprised of a single fiber, with the water flowing inside the fiber and the air stream flowing outside the fiber, is considered. The air stream outside the fiber has an outer free surface. Furthermore, the equations governing the fluid flow and heat and mass transfer in the two streams are combined together with the heat and mass diffusion equations in membranes. The conjugate problem is then solved to obtain the velocity, temperature, and concentration distributions in the two fluids and in the membrane. The local and mean Nusselt and Sherwood numbers in the cell are then obtained and experimentally validated.
UNSTABLE ANISOTHERMAL MULTICOMPONENT CONVECTIVE FLOW: FROM SMALL TO LARGE SCALES
549-566
10.1615/ComputThermalScien.2012006451
Rachid
Bennacer
L2MGC F-95000, University of Cergy-Pontoise, 95031 Cergy-Pontoise Cedex, Paris, France; ENS-Cachan Dpt GC/LMT/CNRS UMR 8535, 61 Ave. du Président Wilson, 94235 Cachan Cedex, France; Tianjin Key Lab of Refrigeration Technology, Tianjin University of Commerce, 300134
Omar
Rahli
Laboratoire LTPMP, Fac GMGP, USTHB, 16111, Bab Ezzouar, Algiers, Algeria
Haikel
Ben Hammed
LTI, IUT Amiens, Avenue des Facultes, Le Bailly 80025 AMIENS, Cedex 1, France
Rayleigh-Benard
convection
double diffusive
complex flow
stability
The present document covers fundamental, academic, and practical topics. Indeed, the mixed convection in channels heated and cooled differentially has been studied in relation to several practical applications. Most interest in these flows are encountered in several domains to explain certain geological phenomena and atmospheric flows, and intervene in many industrial applications such as cooling of electronic appliances, plastics manufacturing, building sciences, moisture transfer, or in the chemical vapor deposition and other crystal growth techniques. It either permits simulation of pollution problems or storage of different fluid mixtures either in natural storage (traps structures) or in industrial tanks. Being bound by any such applications, the subject is currently open for exploration in order to enrich our knowledge of this complicated problem. We consider three-dimensional thermosolutal mixed convection with flow confined between two parallel and horizontal planes where the lower and upper surfaces are hot and cold, respectively. Such a configuration of convective flows is referred to as Poiseuille−Rayleigh−Benard, (PRB) which is based on the famous Rayleigh−Benard problem. In such a PRB configuration, the flow results from the superposition of two convective sources; i.e., the horizontal pressure gradient that causes the main flow within the duct and a vertical temperature and/or concentration gradient, which are the cause of thermoconvective structure formations. The stability diagram and the effect of the entrance domain on the exchanges are presented. We classify the different behaviors and we complete the classical stability analysis by linear stability on a bounded domain. The numerical results demonstrate explicitly the important effect of the entrance domain on the obtained solution and also on the resulting exchange (heat and mass).