Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
25
1-3
1998
Turbulent Transport of Momentum and Scalars in Swirling Flows with and without Combustion
1-13
Toshimi
Takagi
Depertment of Mechanophysics, Graduate School of Engineering, Osaka University
2-1, Yamada-oka, Suita, Osaka, 565-0871 Japan
Sh.
Hirai
Department of Mechanical Engineering, Osaka University, Osaka, Japan
Effects of swirl on turbulent transport of momentum and scalars (heat and mass) are described, based on the reviews of experiments and numerical analysis of swirling flows. They include turbulent flows in a pipe rotating along its axis, in an annulus with a rotating inner cylinder, and in a stationary tube with swirl. Factors affecting the retardation and promotion of turbulent transport due to swirl are illustrated, paying attention to the production terms in transport equations of turbulent fluxes of momentum and scalars. Variable density effects in swirling flows are also described. Numerical computations incorporated with turbulence models are compared with experiments with and without combustion to reveal the applicability of the models.
Physical Properties and Heat Transfer in Tube Flows of Non-Newtonian Fluids
14-30
S. S.
Yoo
Department of Mechanical Engineering and Design, Hankuk Aviation University, Kyonggi, Korea
A brief summary for non-Newtonian fluids is presented to define the meaningful parameters for the analysis of fluid flow and heat transfer. Rheological models and thermophysical properties for non-Newtonian fluids are summarized for the flow and heat transfer analysis. The characteristic time and the diffusion time of polymer solutions are discussed to stress the significance of the rheological description of non-Newtonian fluids. The crucial roles of the solvent chemistry and degradation on the fluid flows and heat transfer are elucidated. Discussion on heat transfer is focused on the forced convection in tube flows for the power law fluids and viscoelastic fluids. Long thermal entrance length for viscoelastic fluids is discussed extensively.
Numerical Simulation of Forced Convection Heat Transfer from an Ellipsoid of Revolution, Using a Fourier Spectral Method
31-40
Yoshihiro
Mochimaru
Department of International Development Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan
Forced convection heat transfer from an ellipsoid of revolution is analyzed numerically. By assuming fluid properties to be constant, and introducing boundary-fitted conformal mapping coordinate system (in the plane), the energy equation can be decpomposed into Fourier components in one space coordinate using a form of Fourier series for temperature and a function relating to an axially symmetric stream function in the same space coordinate; the decomposed equation can be discretized in another spatial coordinate, using substantially doubly-exponential grid spacing, to get relatively accurate thermal field and a mean Nusselt number even at a relatively high Reynolds number flow past a body of revolution (from a thin prolate spheroid to an oblate spheroid.)
Mixed Convection Heat Transfer of an Open Shallow Rectangular Cavity Packed with Spherical Particles
41-51
Hideo
Inaba
Department of Mechanical Engineering, Okayama University, Okayama, Japan
K.
Ozaki
Department of Mechanical Engineering, Okayama University, Okayama, Japan
Sh.
Nozu
Department of Mechanical Engineering, Okayama University, Okayama, Japan
Convection heat transfer measurements were performed in an air flowing over an open rectangular cavity. The open rectangular cavity was installed at the lower part of a horizontal rectangular wind channel, and an one row arrangement of spherical particles was provided in the cavity. Air flowing through the channel was heated via the particle layer from the bottom heating surface of the cavity. The heat transfer results were correlated by using the parameters which represented the effects of the air velocity, particle thermal conductivity, cavity depth and temperature difference between the incoming air and the heating surface.
Spectrally Correlated Radiative Transfer in Real 3D Axisymmetrical Systems (The Sc. Art Code)
52-63
Jean
Taine
Laboratoire d'Energetique Moleculaire et Macroscopique, Combustion, UPR 288 du CNRS et de l'ECP. Ecole Centrale Paris, 92295 Chatenay-Malabry Cedex, France
Anouar
Soufiani
Laboratoire EM2C, CNRS, Centrale Supélec, Université Paris-Saclay,
Gif-Sur-Yvette, France
A method for the treatment of radiative transfer in a general axisymmetrical system containing an absorbing, emitting but nonscattering mixture of gases and particles is presented. A Random Statistical Narrow Band method is used in order to model the radiative properties of gases (CO2, H2O ...). The spectral effects due to the correlations between the gas line positions for different column elements arc computed by using the Curds-Godson approach for some principal directions and approximated for the other directions by using a continuous correlation function. The correlated intensities are computed for each point and each narrow spectral band for a large number of directions which belong to planes parallel to the axis of the system. The general code reliable for any 3D axisymmetrical system, which may contain internal bodies, is validated in the cases of a planar geometry and an infinite cylinder by comparison with an exact direct numerical calculation. The correlation effects are discussed in different conditions. An example of application in a complex geometry is given.
Turbulence Intensity in Fully Developed Turbulent Flow in an Eccentric Annulus
64-74
Fumimaru
Ogino
Department of Chemical Engineering, Kyoto University, Kyoto, Japan
T.
Kimura
Department of Chemical Engineering, Kyoto University, Kyoto, Japan
A measurement was made of stream wise velocity fluctuation in a fully developed turbulent flow in an eccentric annulus. The experiment was performed utilizing two annular ducts of different radius ratios 0.308 and 0.48; in each case the eccentricity was varied from 0.25 to 0.75. The result indicates that the radial distribution of the relative turbulence intensity has a minimum value in the central region between inner and outer tubes. The variation of the relative turbulence intensity against φ has a peak value near φ = 3π/8, where φ is the circumferential coordinate of the bipolar coordinate system. The location of the minimum turbulence intensity approaches the radial position nearest the outer tube wall when the value of φ is close to 3π/8. Those results indicate that there is some difference between two regions of φ < 3π/8 and φ > 3π/8.
Time Evolution of Double-Diffusive Convection during Solidification of a Binary System
75-85
Tatsuo
Nishimura
Department of Mechanical Engineering, Yamaguchi University, Ube 755, Japan
T.
Imoto
Department of Mechanical Engineering, Yamaguchi University, Ube, Japan
H.
Miyashita
Department of Materials Science and Engineering, Toyama University, Toyama, Japan
This manuscript describes time-evolution of double-diffusive cells during solidification of NH4Cl−H2O system in a confined cavity with lateral cooling. Time-dependent concentration measurements show a step change of concentration with time, and temperature visualizations reveal a S-shaped profile of isotherms. Although the cells move vertically and the thickness of each cell increases, the concentration in each cell is found to remain almostly constant. Convection within each cell is largely controlled by the temperature field, and diffusion is dominant in the diffusive layers between the cells due to the solute field with a vertical concentration gradient. There is a clear separation of domain of dominance between the temperature and solute-induced buoyancy effects.
An Experimental Study of Forced Convective Boiling Heat Transfer of Refrigerants in a Rough Surface Tube
86-97
Satoru
Momoki
Department of Mechanical Systems Engineering, Nagasaki University, Nagasaki, Japan
H.
Shintaku
Institute of Advanced Material Study, Kyushu University, Kasuga, Japan
Jian
Yu
Institute of Advanced Material Study, Kyushu University, Kasuga, 816, Japan
Shigeru
Koyama
International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan; Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-koen 6-1, Kasuga-shi, Fukuoka 816-8580, Japan
Toru
Shigechi
Department of Mechanical Systems Engineering, Nagasaki University, Nagasaki, Japan
T.
Fujii
Institute of Advanced Material Study, Kyushu University, Kasuga, Japan
Experiments were carried out on the forced convective boiling heat transfer of refrigerants HCFC22 and HCFC123 inside a tube whose surface was rougher than that of an ordinary smooth copper tube used commercially as heat transfer tube. The local heat transfer coefficients were measured in the range of reduced pressure ratio of 0.07 to 0.23 for mass velocity 300 kg/(m2·s). The measured heat transfer coefficients inside the present tube in annular flow regime are 20−80% higher than those calculated using the authors' previous correlation for an ordinary smooth tube. Once the term representing the nucleate pool boiling heat transfer contribution in this correlation equation is modified by considering the surface roughness effect, the modified equation can correlate the heat transfer coefficients of the present tube within 25% deviations.
Intermittent Airblast Atomization and Spray Particle Mixing in Pulsating air Flow
98-110
T.
Inamura
Department of Aeronautics and Space Engineering, Tohoku University, Sendai, Japan
Nobuki
Nagai
Department of Aeronautics and Space Engineering, Tohoku University, Aramaki Aza Aoba, Aoba-ku, Sendai, Japan
K.
Inokuchi
Department of Aeronautics and Space Engineering, Tohoku University, Sendai, Japan
Yo. T.
Oh
Department of Mechanical Engineering, Chon Buk National University, Chonju, Korea
A new twin-fluid injector applicable to single-point injector for gasoline engine was developed. Transient spray characteristics, mixing mechanism of spray particles and the deposition mechanism on the inner wall of the intake manifold were investigated.
Spray formation by the newly developed single-point injector and the measurements of spray particle sizes, velocities and deposition rates have been conducted in a pulsating air flow. Experiments have been carried out under cold flow condition.
The particle deposition takes place due to particle inertia at high air flow rate. At low air flow rate it takes place clue to the recirculation which appears on the inner wall at the entrance of an intake manifold. On the other hand, the deposition rate of spray particles is strongly influenced by air pulsation. The behavior of spray particle is influenced by the air pulsation at the low velocity of atomizing air and at high velocity of the air flowing around the injector. The small particles follow the air flow more easily than large particles, and this causes the spatial particle size distribution in the spray clump. As the spray particle approaches to the tip of spray clump, the particle size decreases.
Development of a Model for Turbulent Combustion within Porous Inert Media
111-122
R. D.
Matthews
Combustion Research Program, Department of Mechanical Engineering, The University of Texas at Austin, Austin, USA
In-G.
Lim
Combustion Research Program, Department of Mechanical Engineering, The University of Texas at Austin, Austin, USA
Prior models for porous inert medium (PIM) burners have not been able to accurately predict burning speeds, CO emissions, and NOx emissions. All prior models for these burners have assumed laminar flow within the porous structure. However, there are reasons to believe that the flow within these burners is turbulent. Therefore, a turbulent PIM burner model has been developed. A one-equation k-ε. model is used to simulate the turbulent flow field. This model makes use of the fact that the pore size constrains the size of the largest turbulent eddies. Thus, the integral length scale, which is assumed to be a simple function of the pore size, is used to determine e. It is also assumed that the dominant effect of turbulence is enhancement of the transport properties. The increased transport properties result in broader flame zones, decreased gas temperatures, and increased burning rates. The decreased gas temperature results in decreased NOx emissions. The resulting predictions of the CO emissions are also improved.
Empirical Study on Heat Transfer in Pulse Burner
123-134
David Y. S.
Lou
Department of Mechanical Engineering, University of Nebraska, Lincoln, NE 68588, USA
J.
Chen
Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, USA
In order to predict heat transfer in pulse burner, an analytical solution of fully developed flow in a circle pipe is used to study the effect of pulsation on velocity profiles. The velocity profiles are found flattened in pulsatile flow and this flatness increases with increases in frequency.
Based on the behaviors of flow as affected by the pulsation, a parabolic secondary velocity profile (PSVP) and an empirical turbulent velocity profile (ETVP), are proposed to model the actual flow characteristics. With these proposed velocity profiles, the effects of both frequency and velocity oscillatory amplitude are reflected in the changes of sectional mean velocity. These sectional mean velocities of PSVP and ETVP are then applied to an empirical heat transfer correlation to determine the heat transfer characteristics of pulse burner. The results, which are applicable to burner but can be applied to tail pipes with slight modification of the inlet conditions, show that heat transfer in pulse burner increases with increasing frequency of pulsation and velocity oscillatory amplitude.
A New Averaging Technique for Multiphase, Turbulent, Reacting
135-143
Y. G.
Zhao
Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, USA
S. H.
Chan
Department of Mechanical Engineering, The University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA
M. M. M.
Abou-Ellail
Mechanical Engineering Department, Cairo University Cairo, Egypt; The George Washington University, Washington DC, USA
The main purpose of this paper is to present a new averaging technique for the transport governing equations of turbulent, multiphase, reacting flows. It allows for density fluctuations and void fraction fluctuations in the averaging process. It yields a much less number of correlation terms which have to be modeled than other techniques. Based on the new averaging technique, a sample example problem is calculated with the modified TEACH code for the turbulent multiphase parabolic flow and the results show its superiority over current available techniques.
Friction Factor and Heat Transfer Correlations for Gaseous Reactant Flow in Fuel Cell Power Modules
144-155
G. J.
Hwang
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, Taiwan
Y. C.
Cheng
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, Taiwan
Moses L.
Ng
Energy and Resources Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan
To simulate the hydrodynamic and thermal behavior of the gaseous flows in fuel cells, a numerical study was made to investigate the forced laminar convection in the entrance region of a square duct with one wall subjected to uniform mass transpiration and constant wall heat flux. Typical velocity and temperature distributions along the flow direction are reported, as well as the correlations for hydrodynamic and thermal entrance lengths are proposed. Effects of fluid injection and suction on the pressure gradient, bulk mean temperature, friction factor and Nusselt number are all examined. Both local friction factor and Nusselt number correlations in the developing and developed regions are also obtained for using in engineering design and thermal control of fuel cell stacks.
Advanced Optical Methods in Transient Heat Transfer and Two-Phase Flow
156-180
Franz
Mayinger
Lehrstuhl A für Thermodynamik, Technische Universität München, München, Germany; Technical University, Hannover, FRG Institut fur Verfahrenstechnik
Mass Transport Effects on Coronary Flow and Left Ventricular Mechanics
181-188
D.
Zinemanas
The Julius Silver Institute, Department of Biomedical Engineering, The Heart System Research Center, Technion-Israel Institute of Technology, Haifa, Israel
Rafael
Beyar
The Julius Silver Institute, Department of Biomedical Engineering, The Heart System Research Center, Technion-Israel Institute of Technology, Haifa, Israel
Samuel
Sideman
Departments of Chemical and Biomedical Engineering The Julius Silver Institute of Biomedical Engineering Technion-Israel Institute of Technology, Haifa 32000, Israel
The contractions of the left ventricle (LV) of the heart maintain the blood flow through the body's organs, including the coronary arteries which nourish the contracting and relaxing heart muscle. The effects of fluid and mass transport inside the muscle on the LV mechanics and coronary flow are demonstrated through the model simulation of the LV response to a step change in blood osmolality and the blockage of the lymphatic outflow. An integrated LV model, that takes into account the myocardial mechanics, the coronary flow, and the fluid and mass transport, is used in the analysis. The results show that fluid and mass transport have important effects on the myocardial mechanics and the coronary flow.
Stability and Dynamics of Thin Heated Liquid Films
189-201
S. G.
Bancoff
Northwestern University, Department of Chemical Engineering, Evanston, USA
Some applications of the dynamical theory of thin liquid films on a solid surfaces, subject to heat transfer, are presented. Thermocapillary and vapor recoil effects are destabilizing, while hydrostatic pressure and surface tension effects tend to stabilize the film. Gravitational surface waves promote wave steepening and possible wave breaking. The growth of nonlinear waves may result in equilibration and "permanent" two-dimensional waves, which can, however, be destroyed by secondary wave growth in the transverse direction. The phenomena which are found include downwards fingering, which may lead to local dryout, and the formation of longitudinal rolls, which may lead to rivulet formation on a heated surface.
Effect of the Buoyancy Ratio on the Number of Double-Diffusive Cells in a Rectangular Enclosure
202-211
Hwataik
Han
Department of Mechanics and Design, Kook Min University Seoul, Korea
Double diffusive multi-cells are formed in a rectangular enclosure when horizontal temperature and concentration gradients are present in a certain range of parameters. The system parameters are thermal Grashof number, solutal Grashof number, Prandtl number, and Schmidt number for an enclosure with a given aspect ratio. Depending on the ratio of thermal and solutal Grashof numbers flow patterns due to double diffusive natural convection change, as the number of cells change. The flow structure determines the heat and mass transfer characteristics from the vertical surfaces of the cavity. It is the objective of the present study to investigate the effect of the ratio of thermal and solutal buoyant forces on the number of double diffusive cells formed in a vertical rectangular enclosure. An electrochemical copper deposition system is utilized with the vertical electrode maintained at different temperatures. Temperature distribution is measured using a thermocouple probe along the vertical centerline. The concentration distribution of cupric ion in the enclosure is determined by measuring the attenuation of light through the test cell. In well developed cells, concentration is nearly uniform in each cell, and there are large concentration gradients across the interfaces. The temperature distribution shows a stable stratification in each cell and temperature inversion across the cell interfaces. The interfaces are not quite clear in case the cell does not have appreciable size. The number of cells in a cavity is investigated as a function of the buoyancy ratio.
Rough-Wall Heat Transfer in Tbrbulent Boundary Layers
212-219
M. H.
Hosni
Department of Mechanical Engineering, Kansas State University, Manhattan, USA
H. W.
Coleman
Mechanical Engineering Department, University of Alabama in Huntsville, Huntsville, USA
Robert P.
Taylor
Mechanical Engineering Department, Mississippi State University, Mississippi State, MS, USA 39762
Measurements for heat transfer in the rough wall turbulent boundary layers are presented. This paper summarizes the previous experimental results for six test surfaces five rough and one smooth. Three of the rough surfaces are smooth plates roughened with hemispherical elements uniformly distributed 2, 4, and 10 base diameters apart. The remaining two rough surfaces are smooth plates roughened with truncated, right circular cones uniformly distributed 2 and 4 base diameters apart. Both of the roughness geometries hemispheres and truncated cones have a 1.27 mm base diameter and a roughness height of 0.635 mm. The Stanton number data are for zero pressure gradient incompressible turbulent boundary layer air flow for several freestream velocities ranging from 6 to 66 m/s which cover the aerodynamically smooth transitionally rough and fully rough flow regimes. These data are compared with previously published results from another similar test facility using a rough surface comprised of spheres of a single size (1.27 mm diameter) packed in the most dense array. It is shown that data for a given rough surface viewed in Stanton number versus enthalpy thickness coordinates do not collapse to a single curve in the fully rough regime as had been postulated based on observations of a single set of rough wall data. The heat transfer data also show that for a given surface Stanton number data in Rex, coordinates approach an asymptotic curve as freestream velocity is increased, becoming a function of Rex, alone (as in the case for smooth wall turbulent flows). However, there is a different asymptotic St-Rex curve for each rough surface, with Stanton number at a given Rex, increasing with decreasing roughness spacing, that is as the surface becomes "rougher". The data also show a measurable difference in Stanton numbers due to roughness elements shape effects.
An Experimental Study for Combined Close-Contact and Natural Convection Melting in a Spherical Capsules
220-229
Takeo S.
Saitoh
Department of Aeronautics and Space Engineering, Tohoku University, Sendai 980 Japan
J. H.
Moon
Department of Aeronautics and Space Engineering, Tohoku University, Sendai, Japan
The combined melting processes of the phase change material (PCM) in spherical capsules were investigated experimentally under various ambient temperature conditions. The spherical capsules filled with the solid n-octadecane initially at its melting temperature were instantaneously submerged into a constant-temperature bath. The density of the solid exceeds that of the liquid, which allows the solid bulk continually to drop toward the bottom of the capsule as melting progresses. It was shown that molten mass fraction can be represented as a function of a dimensionless parameter (t*Ste3/4Ar1/4), with f being the Fourier number, Ste the Stefan number, and Ar the Archimedes number. The melting shape and the complete melting time for various Stefan numbers has been studied. Further, the effect of ambient pressure was also clarified by the experiment. For the capsule with small diameter, it was found that heat conduction is a dominant heat transfer mode. The combined natural convection and close contact melting effects should be considered under large diameter and high Stefan number cases. The present experimental data will be compared with the analytical results by other researchers.
The Effect of a Spacer Grid Mixing Vane on the Critical Heat Flux for a Rod Bundle
230-242
Joon Sik
Lee
School of Mechanical and Aerospace Engineering, Seoul National University, San 56-1. Sillim-dong Gwanak-gu. Seoul 151-742 Korea
J. H.
Park
Department of Mechanical Engineering, Seoul National University, Seoul, Korea
M. Gros
d'Aillon
Laboratory d'Etude Thermohydrauliques des Assemblages Combustibles, Centre d'Etudes Nucleaires de Grenoble, Grenoble Cedez, France
The present study experimentally investigates the critical heat flux for a 5 × 5 rod bundle as a simple model for an actual PWR fuel assembly. Tests were performed for the 25 rod bundle with and without mixing vanes of spacer grids to evaluate the effect of mixing vanes on the critical heat flux. The enthalpy distribution among the subchannels and turbulent mixing coefficient were obtained by single-phase flow tests, and the effect of the mixing vanes on the critical heat flux was examined by two-phase flow tests for various inlet subcooling, mass flux and pressure conditions. The results show that the effect of the mixing vanes on the critical heat flux is more dominant in the subcooled or bubbly flow regime than in the slug or annular flow regime. The mixing vane gives the positive effect by generating the swirling flow and turbulent inter-channel mixing, and by agitating bubbles from the wall for all the flow conditions, on the other hand, it also incurs the negative effect by thinning and destroying the liquid film as a result of increasing the entrainment at the annual flow condition and by the blockage-like behavior at the high mass flux condition.
An Analysis on Convective Heat Transfer of Film Boiling from a Finite-Size Horizontal Plate Facing Downward
243-254
Toru
Shigechi
Department of Mechanical Systems Engineering, Nagasaki University, Nagasaki, Japan
Yu.
Tokita
Department of Production Systems Engineering, Oita University, Oita, Japan
K.
Kanemaru
Department of Mechanical Systems Engineering, Nagasaki University, Nagasaki, Japan
T.
Yamada
Department of Mechanical Systems Engineering, Nagasaki University, Nagasaki, Japan
Satoru
Momoki
Department of Mechanical Systems Engineering, Nagasaki University, Nagasaki, Japan
The two-dimensional, steady-state, laminar convective film boiling heat transfer from a finite-size horizontal plate facing downward to a stagnant saturated liquid was analyzed by assuming that the flow of vapor beneath the heated plate of a finite size was driven by a hydrostatic pressure gradient due to the change in the thickness of vapor film. The resulting boundary-layer equations for the vapor flow were solved by an integral method, taking into account the effect of the plate edge. The exact solutions obtained were examined for the case that the inclination angles of the vapor-liquid interface were arbitrarily given at the plate edge as the boundary condition. And the effects of profile shapes of velocity and temperature in the vapor film on the heat transfer rate were investigated. As expected, it was shown that the heat transfer rate took a maximum value at the inclination angle of 90 degrees. Accurate approximate expressions for the maximum heat transfer rate were obtained in terms of Nusselt number for four combinations of profile shapes and compared with experimental data.
Simulation of Turbulent Combustion and Heat Transfer in High Temperature Furnaces
255-265
T. W. J.
Peeters
J. M. Burgers Centre, Delft University of Technology, Lorentzweg, Netherlands
C. L.
Koster
J. M. Burgers Centre, Delft University of Technology, Lorentzweg, Netherlands
J. A.
Wieringa
J. M. Burgers Centre, Delft University of Technology, Lorentzweg, Netherlands
Charles J.
Hoogendoorn
Faculty of Applied Physics, Delft University of Technology, The Netherlands.
A complete simulation model of the combustion chamber of high temperature gas fired furnaces has been developed. It describes the turbulent flow, combustion, heat transfer and NO formation in the flame. For the radiant heat transfer spectral effects have been included. It could be shown that increasing the roof refractory emissivity from 0.4 to 1 increases the energy efficiency with 2 to 5%. The effect of local turbulent fluctuations on radiative fluxes has been found to be important only in the initial part of the flame, fluxes increased by about 27% maximum. NO formation strongly depends on gas-air mixing. Model results could be compared with existing semi-technical scale experimental data.
Soot Formation in Premixed Constant-Volume Propane Combustion at Pressures up to 6 Mpa
266-275
M.-W.
Bae
Department of Mechanical Engineering, Korea Institute of Technology and Education, Choongnam, Korea
K.-S.
Kim
Korea University of Technology and Education, Choongnam, Republic of Korea
The effects of pressure, temperature and equivalence ratio on soot formation in premixed propane-oxygen-inert gas combustion have been investigated over wide ranges of pressure (0.1 to 6 MPa) temperature (1200 to 2100 K) and equivalence ratio (1.5 to 2.7) in a specially designed disk type constant volume combustion chamber. To observe the soot formation under high pressure, premixtures are simultaneously ignited by eight spark plugs located on the circumference of chamber at 45 degree intervals. The eight converging flames compress the end gases to a high pressure. The soot volume fraction in the chamber center during the final stage of combustion at the highest pressure is measured by the in situ laser extinction technique and the burnt gas temperature during the same period by the two-color pyrometry method. The pressure and temperature during soot formation are varied by changing the initial charge pressure and by changing the volume fraction of inert gas in the premixture, respectively. It is found that the soot yield is dependent on the pressure, temperature and equivalence ratio; the soot yield increases under the following conditions:
1) decreasing temperature and increasing equivalence ratio at constant pressure,
2) increasing pressure and decreasing temperature at constant equivalence ratio,
3) increasing equivalence ratio at constant temperature and pressure.
Development of a High Load Submerged Combustion Burner
276-284
H. K.
Yoon
Korea Institute of Energy Research, Taejon, Korea
K. S.
Song
Korea Institute of Energy Research, Taejon, Korea
S. N.
Lee
Korea Institute of Energy Research, Taejon, Korea
A comprehensive study has been implemented to develop a high combustion load burner with innovative performances which should produce short and compact flames as well as minimum pollutants. A continuous swirl jet type burner (combustion load: 100 kW) was designed, built and tested to extract various design data of a submerged combustion burner. The experiments of combustion characteristics included the effects of burner geometries (gas nozzle geometries, air swirler geometries, gas injection location) and operation conditions (combustion load, 1st and 2nd air rate) on combustion efficiency and flame shape.
Mixed Convection in a Rectangular Duct Heated from below
285-294
Uichiro
Narusawa
Department of Mechanical, Industrial & Manufacturing Engineering, Northeastern University, Boston, MA 02115, USA
A thermally-developing nitrogen gas flow at the entrance region of a rectangular duct is studied numerically when the bottom is heated isothermally with adiabatic sidewalls. Flow patterns are analyzed over a range of a Rayleigh number, in which steady convective rolls are induced by buoyancy. Effects of buoyancy on heat transfer are also examined for ducts with the aspect ratio of 2-6. Both the Nusselt number and the entrance length for full development of mixed convection are shown to exhibit irregular variations as the number of longitudinal rolls changes with the aspect ratio.
Current Problems of Heat and Mass Transfer in the Cryopreservation of Biomaterials: Interactions among Coupled Multiscale Transport Processes
295-304
Kenneth R.
Diller
Department of Mechanical Engineering, University of Texas, Austin, Texas, USA
Although the low temperature storage of cells and tissues for transplantation offers a great potential advantage in the treatment of numerous diseases, many practical applications have been limited by the ability to understand and control the heat and mass transfer processes that govern cryopreservation protocols. These process typically occur across length scales that may differ by many orders of magnitude. Further, the presence of individual cells and tissues introduces additional scaling parameters that may influence the transport phenomena. Among the most challenging problems are effecting the coupled transport of water and a cryoprotective agent (CPA) into and out of a tissue and its constituent cells, manipulating the thermal boundary conditions during freezing to produce an acceptable redistribution of solute rejected from the growing ice front, and controlling the osmotic and mechanical stresses that govern the movement of chemical species in tissues during cryopreservation. Approaches will be presented by which each of these problems may be addressed.
Spin-up Flows in a Rotating Cylindrical Container
305-313
Jae Min
Hyun
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Taejon, South Korea
A brief review is made of more recent studies of spin-up flows in a cylinder. The major points of the classical models of spin-up, dealing with the transient process of fluid adjustment to the change in the rotation rate of the container, are discussed. The specific topics that are covered here include the spin-up of a homogeneous fluid from rest, transient flow of a stratified fluid from a state of rest, and transient deformation of the free surface of a liquid in an abruptly rotating cylinder. Assessments are made of the various flow models that have been proposed, and comparisons are made among the analytical predictions, numerical computations, and experimental data. The fundamental dynamic interplay of the Ekman boundary layer and the inviscid interior is stressed.
Effect of Physical Properties Variation on Convective Heat Transfer
314-328
Algirdas
Zukauskas
Lithuanian Academy of Sciences, Vilnius, Lithuania
The report deals with forced convection in single-phase flows. The analysis of the heat transfer in laminar, turbulent and separated flows includes the effect of variable fluid physical properties and covers a wide range of the Prandtl numbers. It also presents general characteristics of working fluid and variation of properties of different liquids at different temperatures. The effect of variable physical properties for different temperature differences and heat flux directions is analyzed and methods of calculations of heat transfer are suggested.
Convective Heat Transfer from a Heated Convex Cylinder with an Axisymmetric Backward-Facing Step
329-338
K. C.
Kim
Department of Mechanical and Production Engineering, Pusan National University, Pusan, Korea
M.
Niaki
Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada
Y. P.
Lee
Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario, Canada, KIN 6N5
Local heat transfer coefficients were measured in the separating, reattaching and redeveloping axisymmetric regions of turbulent boundary layer over the wall of convex cylinders with a uniform wall heat flux. Measurements were made with three different diameters of cylinders with five different diameters of the obstructions. The range of Reynolds number based on step height was between 4000 to 100000.
The study demonstrates that the maximum Nusselt number increases with decreasing cylinder radius and are always greater than those for the two-dimensional backward-facing step flow at the same conditions of the step height and flow velocity. It was also observed that the heat transfer in the redeveloping region increases with an increase in the radius convex curvature. An empirical equation is proposed for the Nusselt number at the reattachment point, correlated as a function of the Reynolds number and the diameter ratio.
The Mixed Convection Flow of a Bingham Plastic in an Eccentric Annulus
339-350
N.
Patel
Department of Applied Mathematical Studies, University of Leeds, Leeds, UK
Derek B.
Ingham
Centre for CFD, Department of Applied Mathematical Studies, The University of Leeds, Leeds, LS2 9JT, UK; Energy-2050, Faculty of Engineering, University of Sheffield, Sheffield, S10 2TN, UK
The modeling of laminar, fully-developed combined convection flow of a Bingham plastic in a vertical eccentric annulus, in which the walls are held at asymmetric constant temperatures is investigated. The momentum, continuity and energy equations are solved numerically using the Finite Element Method (F.E.M.). The results obtained are found to be in good agreement with the analytical solutions found by using a narrow gap approximation, that is the gap between the walls of the annulus is small compared with the inner radius. It is shown that different flow configurations exist depending on the buoyancy parameter, Grashof/Reynolds, including flow reversal and unsheared plug flow adjacent to the wall. If flow reversal occurs it is shown by the numerical solution that a pair of 'true plugs' in which the velocity is independent of both the radial and azimuthal variables can exist at each of the widest and narrowest regions of the annulus. Further, it is found that the leading order narrow-gap approximation is inadequate to predict these true plugs.
A Bayesian Analysis of Steam Generator Tube Wall Emissivity for Heat Treatment
351-362
M. H.
Hu
Nuclear Services Division, Westinghouse Electric Corporation, Pittsburgh, Pennsylvania, USA
This paper develops a probabilistic method for estimating tube wall emissivity of a steam generator. Bayes' theorem combines the generic probability density function (pdf) of tube wall emissivity with specific data. The combination results in a specific pdf of the emissivity for specific steam generator. Estimates of the emissivity provide inputs for probabilistic estimation of tube wall temperature during field heat treatment of steam generator tubes.
Heat Transfer to Low Prandtl Number Fluids in Turbulent Pipe Flow: a Simple but Accurate Application of Reynolds Analogy
363-375
D. R. H.
Beattie
Australian Atomic Energy Commission, Research Establishment Lucas Heights Research Laboratories Private Mail Bag, Sutherland, 2232, NSW Australia
Squire's (1948) model of turbulence is extended via Reynolds analogy to provide simple expressions for temperature profiles and heat transfer coefficients for developed heated turbulent pipe flows with Prandtl numbers less than one. The analysis uses a semi-empirical turbulent Prandtl number, based on thermal and drag losses for an eddy, and which is structured to retain the simplicity of the Squire turbulence model. Derived expressions agree satisfactorily with available data, including heat transfer data in the usually-neglected region Pr ∼ 0.4.
Convection Dominated PCM Fusion around a Vertical Cylinder
376-385
C. A.
Melo
Uberlandia, MG, Brazil
Kamal A. R.
Ismail
Department of Thermal and Fluids Engineering - FEM, State University of Campinas, Brazil
In this model the equations of conservation of mass, momentum and energy are formulated in terms of the vorticity and the stream functions while the Boussinesq model is used to formulate the fluctuation term. The dimensionless variables used lead to continuous fusion in the discretized control volumes while the boundary conditions at the moving liquid-solid interface are determined iteratively in terms of the enthalpy and the stream functions. The predictions from the present model were compared with available experimental results and the agreement is found to be satisfactory.
Horizontal Nucleate Flow Boiling Heat Transfer Coefficient Measurements and Visual Observations for R12, R134a and R134a/Ester Lubricant Mixtures
386-399
Mark
Kedzierski
NIST
M. P.
Kaul
Bristol Compressors, Bristol, VA 24202
The heat transfer characteristics of horizontal nucleate flow boiling of R12, R134a, and R134a/Ester Lubricant mixtures were investigated both visually and calorimetrically. The effect of two different ester lubricants on the boiling characteristics of R134a were investigated. The test refrigerant entered a roughened quartz tube test section slightly above the saturated state. Locally measured heat transfer coefficients were taken simultaneously with high speed motion picture images of the boiling process. The motion pictures were used to obtain a descriptive behavior of the boiling which was compared directly to the measured heat transfer coefficients.
Heat Transfer in Bubbly Liquids: Fundamentals and Waves
400-407
A. A.
Gubaidullin
Tyumen’ Affiliate of the Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Sciences, Tyumen’, Russia
The theory of non-steady wave processes in two-phase gas-liquid media with bubble structure, including hierarchy structure of mathematical models of bubbly liquids dynamic behavior, has been developed. The models differ in the degree of accounting the effects of pressure, temperature and phase velocities non-coincidence in the process of dynamic deformation. Estimations of the influence of dynamic and heat interaction between gas and liquid on shock waves evolution have presented. The technique of the worked out models program realization has been proposed. All models have been realized on a computer. A considerable number of computational experiments has been carried out, resulting in defining the principal mechanisms determining shock waves evolution in bubbly liquids in a wide range of parameters. In particular, it has been shown that shock waves evolution in low-viscous liquids with bubble size about 1 mm is determined by heat dissipation resulting from non-equilibrium heat transfer between the gas in the bubbles and surrounding liquid. Thermophysics characteristics of the gas, insignificant in volume and still more insignificant in mass, play the decisive role on evolution and formation of oscillar and monotonous wave configuration. It has been discovered that at waves propagation there may be observed their amplification as a result of the presence of locative deformation inertia characteristics in the bubbly system. The mechanism and peculiarity of shock waves amplification have been studied. The analysis of other experimental data contained in literature has been carried out. The comparison of the calculated and experimental data has proved correctness of the worked-out theory.
Mixing Time in a Gas-Particle Stirred Ladle with Throughflow
408-421
An experimental study is conducted on a gas-particle stirred ladle system with throughflow of molten metal using a simplified water model. A real-time image processing technique is employed to investigate the effects of nozzle location, throughflow rate and air and particle flow rates on the melt-particle mixing as well as to determine the timewise variation of gas and particle behavior. It is disclosed that the mixing energy supplied to the ladle consists of four sources including buoyancy, gas and particle injections and throughflow and that the mixing time decreases with an increase in the total mixing energy. No effect of nozzle depth on mixing appears explicitly if mixing times measured are summarized as a function of the total mixing energy. Longer mixing time is attained in the lower mixing energy regime, in which the main contribution is due to the rising gas bubbles through the melt driven by buoyancy. On the contrary, shorter mixing time is expected if the mixing energy input is larger and depends mainly on gas and particle injections. Correlation equations are derived to predict the mixing time in a gas-particle stirred ladle with throughflow.
The Design and Testing of a Fluid Bed Incinerator which Will Be Used to Investigate the Burning of Waste Chemicals
422-429
Joe
Deans
Department of Mechanical Engineering, University of Auckland, Auckland, New Zealand
S. T.
Choi
Department of Mechanical Engineering, University of Auckland, New Zealand
M. L.
Allen
Department of Chemical Engineering, University of Auckland, New Zealand
The destruction and disposal of liquid waste chemicals is a perennial problem which is gaining increasing importance. One possible method of destroying these chemicals is to incinerate them within a fluid bed where there is a relatively long residence time and the combustion of the chemicals is completed. To aid the investigation of this process a 0.17 m diameter fluid bed incinerator has been designed, constructed and tested. This report describes these activities and the tests which were performed on a range "commercial" waste chemicals. The precise composition of these chemicals was continuously changing though they were generally low vapor pressure solvents or oils contaminated with water.
During the incineration tests the effectiveness of the combustion process was determined by monitoring the emission levels of oxygen, carbon monoxide and unburnt hydrocarbons. The results of the tests showed that: i) It was possible to achieve emission levels of 5% Carbon monoxide and less than 100 ppm unburnt hydrocarbons, and that, ii) The optimum operating conditions for the bed were achieved when the exhaust gas contained 5% oxygen.
Three-Dimensional Simulation of Reacting Flow in a Boiler
430-436
W.-T.
Park
Computational Engineering Laboratory, Samsung Advanced Institute of Technology, Suwon, Korea
S.-J.
Shin
Computational Engineering Laboratory, Samsung Advanced Institute of Technology, Suwon, Korea
H.-I.
Lee
Computational Engineering Laboratory, Samsung Advanced Institute of Technology, Suwon, Korea
Numerical simulations are performed on complex flows in an industrial boiler. Three-dimensional steady compressible continuity and Navier-Stokes equations are solved along with energy and species equations, with k-ε turbulence model. The separate supply of hydrocarbon fuel and air into a boiler is modeled using two concentric tube flows with swirling velocity of air. The gas radiation heat transfer is considered. Calculations are carried out via a commercial finite-volume code of FLUENT, on a CRAY YMP-4E/464. Numerical results are examined for the dependence of furnace exit gas temperature (FEGT). Emphasis is placed more on actual design implications rather than on numerical procedures, especially FEGT for the design of the heat exchanger at the exit of boiler.
Reacting and Diffusive Continuum Mechanical Mixture Models Applied to Combustion
437-446
E.
Lundgren
Department of Mathematical Physics and Mechanics, Lund Institute of Technology, Lund, Sweden
Christer
Fureby
Defence Security Systems Technology
The Swedish Defence Research Agency (FOI)
SE 147 25 Tumba, Stockholm, Sweden
S.-I.
Moller
Department of Mathematical Physics and Mechanics, Lund Institute of Technology, Lund, Sweden
The aim of the paper is to derive and discuss general continuum mechanical models for combustion, founded on the mixture theory as given from modem continuum mechanics. This angle of attack differs from the traditional methology generally used in combustion contexts; the obvious advantage of utilizing modern continuum mechanics is mainly the generality and simplicity by the concepts introduced. From the presentation we will focus on a special case of the mixture theory, which can be selected as candidate of a combustion model. In the paper, simulation results for a test case will be given.