Showing papers on "Heat transfer published in 1992"

Bubbles, Drops, and Particles in Non-Newtonian Fluids

Abstract: Preface Preface to the First Edition Acknowledgements About the Author INTRODUCTION, SCOPE, AND ORGANIZATION NON-NEWTONIAN FLUID BEHAVIOR Definition of a Newtonian Fluid Non-Newtonian Fluids: Definition, Examples of Different Types, Mathematical Models Dimensional Considerations in the Mechanics of Viscoelastic Fluids Experimental Techniques: Rheometry RIGID PARTICLES IN TIME-INDEPENDENT FLUIDS WITHOUT A YIELD STRESS Governing Equations for a Sphere Spherical Particles in Newtonian Fluids Spheres in Shear-thinning Fluids Spheres in Shear-thickening Fluids Light Spheres Rising in Pseudoplastic Media Pressure Drop due to a Settling Sphere Non-Spherical Particles RIGID PARTICLES IN VISCOPLASTIC FLUIDS Static Equilibrium of Particles Flow Field: Shape and size of flow zones Drag Force Role of Values of Yield stress used in correlations Time Effects RIGID PARTICLES IN VISCOELASTIC FLUIDS Flow over a sphere Flow over a cylinder Other Studies Involving Interactions Between Non-Newtonian Characteristics, Particle Shape, Flow Field, etc. FLUID PARTICLES IN NON-NEWTONIAN MEDIA Formation of Fluid Particles Shapes of Bubbles and Drops in Free Rise or Fall Terminal Velocity-Volume Behavior in Free Motion Drag Behavior of Single Particles Bubble and Drops Ensembles in Free Motion Coalescence of Bubbles and Drops Breakage of Drops Motion and Deformation of Bubbles and Drops in Confined Flows NON-NEWTONIAN FLUID FLOW IN POROUS MEDIA AND PACKED BEDS Porous Medium Definition, Examples and Characterization Flow of Newtonian Fluids Flow of Non-Newtonian Fluids Miscellaneous Effects Two Phase Gas/Liquid Flow FLUIDIZATION AND HINDERED SETTLING Two-Phase Fluidization Sedimentation or Hindered Settling Three Phase Fluidized Beds MOMENTUM, HEAT AND MASS TRANSFER IN BOUNDARY LAYER FLOWS Boundary Layer Flows Viscoelastic Effects in Boundary Layers Mass Transfer from Bubbles Mass Transfer from Drops Mass Transfer from Ensembles of Bubbles and Drops Heat and Mass Transfer in Fixed Beds Heat and Mass Transfer in Fluidized Beds Heat and Mass Transfer in Three Phase Fluidized Beds Heat Transfer from Tube Bundles WALL EFFECTS Definition For Rigid Spheres For Non-Spherical Particles For Drops and Bubbles FALLING OBJECT RHEOMETRY Falling Ball Method Rolling Ball Method Rotating Sphere Viscometer Falling Cylinder Viscometer *All Chapters contain Introduction, Summary and Nomenclature sections References Subject index Author index

Thermal Radiative Transfer and Properties

Abstract: The Nature of Thermal Radiation. Radiative Properties and Simple Transfer. Diffuse Surface Transfer. Electromagnetic Theory Results. Classical Dispersion Theory. Monte Carlo Surface Transfer. Radiative Transfer Equation. Thermal Radiation Properties of Gases. Radiative Properties of Particles. Radiative Transfer in Nonscattering, Homogeneous Media. Nonisothermal Transfer: Radiative Equilibrium and Diffusion with Isotropic Scattering. Radiative Transfer with Anisotropic, Multiple Scattering. Radiative Transfer Coupled with Conduction and Convection. Monte Carlo in Participating Media. Appendices. Index.

Heat transfer in condensation and boiling

Abstract: A Heat Transfer in Condensation.- 1 Fundamentals.- 2 Film Condensation of Stagnant Vapors.- 3 Drop Condensation of Stagnant Vapors.- 4 Condensation of Flowing Vapors.- 5 Condensation of Metal Vapors.- 6 Condensation of Vapors of Miscible Liquids.- 7 Condensation of Vapors of Immiscible Liquids.- 8 Enhancement of Heat Transfer During Condensation.- B Heat Transfer in Boiling.- 9 The Different Types of Heat Transfer During Boiling.- 10 Physical Fundamentals of Vapor Bubble Formation.- 11 Heat Transfer During Boiling of Pure Substances in Free Convection.- 12 Heat Transfer in Falling Film Evaporators.- 13 Heat Transfer During Boiling of Pure Substances in Forced Flow.- 14 Heat Transfer During Boiling of Mixtures in Free Convection.- 15 Heat Transfer During Boiling of Mixtures in Forced Flow.- 16 Enhancement of Heat Transfer During Boiling.- Index of Names.

Heat sink optimization with application to microchannels

Abstract: The equations governing the fluid dynamics and combined conduction/convection heat transfer in a heat sink are presented in dimensionless form for both laminar and turbulent flow. A scheme presented for solving these equations permits the determination of heat sink dimensions that display the lowest thermal resistance between the hottest portion of the heat sink and the incoming fluid. Results from the present method are applied to heat sinks reported by previous investigators to study effects of their restrictions regarding the nature of the flow (laminar or turbulent), the ratio of fin thickness to channel width, or the aspect ratio of the fluid channel. Results indicate that when the pressure drop through the channels is small, laminar solutions yield lower thermal resistance than turbulent solutions. Conversely, when the pressure drop is large, the optimal thermal resistance is found in the turbulent region. With the relaxation of these constraints, configurations and dimensions found using the present procedure produce significant improvement in thermal resistance over those presented by all three previous studies. >

Thermal Properties and Temperature-Related Behavior of Rock/Fluid Systems

Abstract: I. Thermal Processes and Terms. Applications requiring thermal data. Definition of terms. II. Heat Capacities of Rocks. Experimental measurements. Calculated heat capacities. Heat capacities of fluid saturated rocks. Generalized calculations of heat capacities. Heat capacity of shales. III. Thermal Reactions in Rocks. Experimental methods. Results of measurements. IV. Thermal Expansion of Rocks. Thermal expansion of dry sandstones. Thermal expansion of fluid saturated rocks under stress. Conclusions on thermal expansion. V. Thermal Conductivities of Rock/Fluid Systems. Methods of measuring thermal conductivities. Effects of rock/fluid properties on thermal conductivity. Effects of temperature on thermal conductivity. Effects of stress on thermal conductivity. Summary. VI. Thermal Conductivity Models. Mixing law models. Empirical models. Theoretical models. Summary. VII. Thermal Diffusivities of Rocks. Experimental methods of measurement. Measured diffusivities of rocks. Calculated thermal diffusivities of rocks. VIII. Heat Transfer with Flowing Fluids. Natural convection in porous media. Fluid phase changes in porous media ( VCC effect ). Convective heat transfer with flowing fluids. IX. Thermal Alterations of Rocks. High temperature alterations. Role of fluxing agents in high temperature alterations. Reduction in fracture pressures by intensive borehole heating. Effects of steaming on rock properties. X. Effects of Temperature on Rock Properties. Bulk and pore compressibilities. Elastic wave velocities. Permeability. Formation resistivity factor. Summary and conclusions. XI. Low Temperature Behavior of Rock/Fluid Systems. P- and S-wave velocities and elastic moduli. Electrical properties. Thermal conductivity. Other low-temperature effects. XII. Wellbore Applications. Thermal data from well logs. Thermal gradients in wells. Heat losses in wells due to VCC effect. Summary and conclusions. Appendix A. Thermal Units Conversion Factors. Appendix B. Thermal Properties Data for Various Rocks. Appendix C. Thermal Properties of Subsurface Reservoir Fluids. References. Author Index. Subject Index.

Heat transfer in rotating serpentine passages with trips normal to the flow

Abstract: Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

Application of self‐preservation in the diurnal evolution of the surface energy budget to determine daily evaporation

Abstract: Evaporation from natural land surfaces often exhibits a strong variation during the course of a day, mostly in response to the daily variation of radiative energy input at the surface. This makes it difficult to derive the total daily evaporation, when only one or a few instantaneous estimates of evaporation are available. It is often possible to resolve this difficulty by assuming self-preservation in the diurnal evolution of the surface energy budget. Thus if the relative partition of total incoming energy flux among the different components remains the same, the ratio of latent heat flux and any other flux component can be taken as constant through the day. This concept of constant flux ratios is tested by means of data obtained during the First ISLSCP Field Experiment; the instantaneous evaporation values were calculated by means of the atmospheric boundary layer bulk similarity approach with radiosonde profiles and radiative surface temperatures. Good results were obtained for evaporative flux ratios with available energy flux, with net radiation, and with incoming shortwave radiation.

Surface Roughness and Its Effects on the Heat Transfer Mechanism in Spray Cooling

Abstract: In the spray cooling of a heated surface, variations in the surface texture influence the flow field, altering the maximum liquid film thickness, the bubble diameter, vapor entrapment, bubble departure characteristics, and the ability to transfer heat. A new method for determining and designating the surface texture is proposed, and the effects of surface roughness on evaporation/nucleation in the spray cooling flow field studied. A one-dimensional Fourier analysis is applied to determine experimentally the surface profile of a surface polished with emery paper covering a spectrum of grit sizes between 0.3 to 22 {mu}m. Heat transfer measurements of liquid flow rates between 1 to 5 l/h and air flow rates between 0.1 to 0.4 l/s are presented. Maximum heat fluxes of 1,200 W/cm{sup 2} for the 0.3 {mu}m surface at very low superheats were obtained.

Ablation electrode with insulated temperature sensing elements.

Abstract: An ablation electrode (16) carries a temperature sensing element (94) for measuring the temperature of the tissue being ablated. A thermal insulating element (88) associated with the sensing element blocks the transfer of heat energy from between the temperature sensing element (94) and the electrode (16). The temperature sensing element therefore measures temperature without being affected by the surrounding thermal mass of the electrode (16).

Sea spray and the turbulent air‐sea heat fluxes

Abstract: Heat and moisture carried by sea spray have long been suspected of contributing to the air-sea fluxes of sensible and latent heat. Using time scales that parameterize how long sea spray droplets reside in the air and how quickly they exchange heat and moisture with their environment, I estimate sea spray contributions to the air-sea heat fluxes. To make these estimates, I first develop a new sea spray generation function that predicts more realistic spume production than earlier models. Spray droplets with initial radii between 10 and 300 μm contribute most to the heat fluxes; the vast majority of these are spume droplets. The modeling not only demonstrates how spray droplets participate in the air-sea heat exchange but also confirms earlier predictions that the heat carried by sea spray (especially the latent heat) is an important component of the air-sea heat balance. In my examples, the maximum magnitude of the spray latent heat flux for a 20-m/s wind is 170 W/m2; the maximum spray sensible heat flux is 33 W/m2. For winds over 10 m/s, the spray latent heat flux is usually a substantial fraction of the interfacial (or turbulent) latent heat flux (estimated from the bulk-aerodynamic equations) and will thus confound measurements of the air-sea transfer coefficient for latent heat.

Heat Effects of Welding: Temperature Field, Residual Stress, Distortion

Abstract: 1 Introduction.- 1.1 Scope and structuring of contents.- 1.2 Weldability analysis.- 1.3 Residual stresses.- 1.4 Welding residual stresses.- 1.5 Welding residual stress fields.- 1.6 Type examples.- 1.7 Welding deformations.- 1.8 References to related books.- 1.9 Presentation aspects.- 2 Welding temperature fields.- 2.1 Fundamentals.- 2.1.1 Welding heat sources.- 2.1.1.1 Significance of welding temperature fields.- 2.1.1.2 Types of welding heat sources.- 2.1.1.3 Output of welding heat sources.- 2.1.2 Heat propagation laws.- 2.1.2.1 Law of heat conduction.- 2.1.2.2 Law of heat transfer by convection.- 2.1.2.3 Law of heat transfer by radiation.- 2.1.2.4 Field equation of heat conduction.- 2.1.2.5 Initial and boundary conditions.- 2.1.2.6 Thermal material characteristic values.- 2.1.3 Model simplifications relating to geometry and heat input.- 2.1.3.1 Necessity for simplifications.- 2.1.3.2 Simplifications of the geometry.- 2.1.3.3 Spatial simplifications of the heat source.- 2.1.3.4 Time simplifications of heat source.- 2.1.3.5 User questions addressing welding temperature fields.- 2.1.3.6 Numerical solution and comparison with experiments.- 2.2 Global temperature fields.- 2.2.1 Momentary stationary sources.- 2.2.1.1 Momentary point source on the semi-infinite solid.- 2.2.1.2 Momentary line source in the infinite plate.- 2.2.1.3 Momentary area source in the infinite rod.- 2.2.2 Continuous stationary and moving sources.- 2.2.2.1 Moving point source on the semi-infinite solid.- 2.2.2.2 Moving line source in the infinite plate.- 2.2.2.3 Moving area source in the infinite rod.- 2.2.3 Gaussian distribution sources.- 2.2.3.1 Stationary and moving circular source on the semi-infinite solid.- 2.2.3.2 Stationary and moving circular source in the infinite plate.- 2.2.3.3 Stationary strip source in the infinite plate.- 2.2.4 Rapidly moving high-power sources.- 2.2.4.1 Rapidly moving high-power source on the semi-infinite solid.- 2.2.4.2 Rapidly moving high-power source in the infinite plate.- 2.2.5 Heat saturation and temperature equalization.- 2.2.6 Effect of finite dimensions.- 2.2.7 Finite element solution.- 2.2.7.1 Fundamentals.- 2.2.7.2 Ring element model.- 2.2.7.3 Plate element models.- 2.3 Local heat effect on the fusion zone.- 2.3.1 Electric arc as a welding heat source.- 2.3.1.1 Physical-technical fundamentals.- 2.3.1.2 Heat balance and heat source density.- 2.3.1.3 Heat conduction modelling of fusion welding.- 2.3.1.3.1 Melting of the electrode.- 2.3.1.3.2 Fusion of the base metal.- 2.3.1.3.3 Interaction of melting-off and fusion.- 2.3.1.4 Weld pool modelling.- 2.3.1.4.1 Weld pool physics.- 2.3.1.4.2 Welding arc modelling.- 2.3.1.4.3 Hydrostatic surface tension modelling.- 2.3.1.4.4 Hydrodynamic weld pool modelling.- 2.3.1.4.5 Hydrostatic weld shape modelling.- 2.3.1.4.6 Keyhole modelling.- 2.3.2 Flame as a welding heat source.- 2.3.2.1 Physical-technical fundamentals.- 2.3.2.2 Heat balance and heat flow density.- 2.3.3 Resistance heating of weld spots.- 2.3.4 Heat generation in friction welding.- 2.4 Local heat effect on the base metal.- 2.4.1 Microstructural transformation in the heat-affected zone.- 2.4.1.1 Thermal cycle and microstructure.- 2.4.1.2 Time-temperature transformation diagrams.- 2.4.1.3 Evaluation of time-temperature transformation diagrams.- 2.4.2 Modelling of microstructural transformation.- 2.4.3 Cooling rate, cooling time and austenitizing time in single-pass welding.- 2.4.3.1 Cooling rate in solids and thin plates.- 2.4.3.2 Cooling rate in thick plates.- 2.4.3.3 Cooling time in solids and plates.- 2.4.3.4 Austenitizing time in solids and plates.- 2.4.4 Temperature cycles in multi-pass welding.- 2.5 Hydrogen diffusion.- 3 Welding residual stress and distortion.- 3.1 Fundamentals.- 3.1.1 Temperature field as the basis.- 3.1.2 Elastic thermal stress field.- 3.1.3 Elastic-plastic thermal stress field.- 3.1.4 Basic equations of thermomechanics.- 3.1.5 Thermomechanical material characteristic values.- 3.2 Finite element models.- 3.2.1 Intelligent solution.- 3.2.2 Rod element model.- 3.2.3 Ring element model.- 3.2.4 Membrane plate element model in the plate plane.- 3.2.5 Membrane plate element model in the cross-section.- 3.2.6 Solid element model.- 3.3 Shrinkage force and stress source models.- 3.3.1 Longitudinal shrinkage force model.- 3.3.2 Transverse shrinkage force model.- 3.3.3 Application to cylindrical and spherical shells.- 3.3.4 Residual stress source model.- 3.4 Overview of welding residual stresses.- 3.4.1 General statements.- 3.4.2 Weld-longitudinal residual stresses.- 3.4.3 Weld-transverse residual stresses.- 3.4.4 Residual stresses after spot-welding, cladding, and flame cutting.- 3.5 Welding distortion.- 3.5.1 Model simplifications.- 3.5.2 Transverse shrinkage and groove transverse off-set.- 3.5.3 Longitudinal and bending shrinkage.- 3.5.4 Angular shrinkage and twisting distortion.- 3.5.5 Warpage of thin-walled welded components.- 3.6 Measuring methods for residual stress and distortion.- 3.6.1 Significance of test and measurement.- 3.6.2 Strain and displacement measurement during welding.- 3.6.3 Destructive residual stress measurement.- 3.6.3.1 Measurement of uniaxial welding residual stresses.- 3.6.3.2 Measurement of biaxial welding residual stresses.- 3.6.3.3 Measurement of triaxial welding residual stresses.- 3.6.4 Non-destructive residual stress measurement.- 3.6.5 Distortion measurement after welding.- 3.6.6 Similarity relations.- 4 Reduction of welding residual stresses and distortion.- 4.1 Necessities and kinds of measures.- 4.2 Design measures.- 4.3 Material measures.- 4.3.1 Starting points.- 4.3.2 Material characteristic values in the field equations.- 4.3.3 Traditional consideration of the influence of the material.- 4.3.4 Derivation of novel welding suitability indices.- 4.4 Manufacturing measures.- 4.4.1 Starting points.- 4.4.2 Measures prior to and during welding.- 4.4.2.1 Overview.- 4.4.2.2 General measures.- 4.4.2.3 Weld-specific measures.- 4.4.2.4 Thermal measures.- 4.4.2.5 Mechanical measures.- 4.4.2.6 Typical applications.- 4.4.3 Post-weld measures.- 4.4.3.1 Overview.- 4.4.3.2 Hot stress relieving (annealing for stress relief).- 4.4.3.2.1 Hot stress relieving in practice and relevant codes.- 4.4.3.2.2 Stress relaxation tests.- 4.4.3.2.3 Microstructural change during hot stress relieving.- 4.4.3.2.4 Equivalence of annealing temperature and annealing time.- 4.4.3.2.5 Creep laws and creep theories relating to hot stress relieving.- 4.4.3.2.6 Analysis examples and experimental results relating to hot stress relieving.- 4.4.3.3 Cold stress relieving (cold stretching, flame and vibration stress relieving).- 4.4.3.3.1 Rod element model for cold stretching.- 4.4.3.3.2 Notch and crack mechanics of cold stretching.- 4.4.3.3.3 Cold stretching in practice.- 4.4.3.3.4 Flame and induction stress relieving.- 4.4.3.3.5 Vibration stress relieving.- 4.4.3.4 Hammering, rolling, spot compression and spot heating.- 4.4.3.5 Hot, cold and flame straightening.- 5 Survey of strength effects of welding.- 5.1 Methodical and systematical points of view.- 5.2 Hot and cold cracks.- 5.3 Ductile fracture.- 5.4 Brittle fracture.- 5.5 Lamellar tearing type fracture.- 5.6 Creep fracture.- 5.7 Fatigue fracture.- 5.8 Geometrical instability.- 5.9 Corrosion and wear.- 5.10 Strength reduction during welding.

Numerical modeling of steam injection for the removal of nonaqueous phase liquids from the subsurface. 1. Numerical formulation

Abstract: A multidimensional integral finite difference numerical simulator is developed for modeling the steam displacement of nonaqueous phase liquid (NAPL) contaminants in shallow subsurface systems. This code, named STMVOC, considers three flowing phases, gas, aqueous, and NAPL; and three mass components, air, water, and an organic chemical. Interphase mass transfer of the components between any of the phases is calculated by assuming local chemical equilibrium between the phases, and adsorption of the chemical to the soil is included. Heat transfer occurs due to conduction and multiphase convection and includes latent heat effects. A general equation of state is implemented in the code for calculating the thermophysical properties of the NAPL/chemical. This equation of state is primarily based on corresponding states methods of property estimation using a chemical's critical constants. The necessary constants are readily available for several hundred hazardous organic liquid chemicals. In part 2 (Falta et al., this issue), the code is used to simulate two one-dimensional laboratory steam injection experiments and to examine the effect of NAPL properties on the steam displacement process.

Numerical calculation of wall‐to‐bed heat‐transfer coefficients in gas‐fluidized beds

Abstract: A computer model for a hot gas-fluidized bed has been developed. The theoretical description is based on a two-fluid model (TFM) approach in which both phases are considered to be continuous and fully interpenetrating. Local wall-to-bed heat-transfer coefficients have been calculated by the simultaneous solution of the TFM conservation of mass, momentum and thermal energy equations. Preliminary calculations suggest that the experimentally observed large wall-to-bed heat-transfer coefficients, frequently reported in literature, can be computed from the present hydrodynamic model with no turbulence. This implies that there is no need to explain these high transfer rates by additional heat transport mechanisms (by turbulence). The calculations clearly show the enhancement of the wall-to-bed heat-transfer process due to the bubble-induced bed-material refreshment along the heated wall. By providing detailed information on the local behavior of the wall-to-bed heat-transfer coefficients, the model distinguishes itself advantageously from previous theoretical models. Due to the vigorous solids circulation in the bubble wake, the local wall-to-bed heat-transfer coefficient is relatively large in the wake of the bubbles rising along a heated wall.

Prediction of radiative transfer in cylindrical enclosures with the finite volume method

Abstract: This article shows how the finite volume method can be implemented to solve three-dimensional radiation problems in cylindrical enclosures. The medium is considered to be gray, and absorption, emission, and either isotropic or nonisotropic scattering are included. For the special case of axisymmetric radiation, a mapping is described that yields a complete solution by solving the intensity in a single azimuthal direction. The method is shown to rapidly converge to the solution of the radiation transfer equation as the spatial and directional grid is refined. Results from the solution of axisymmetric bench mark problems show that the method is stable, accurate, and computationally efficient. 25 refs.

Gas Pressure and Temperature Dependences of Thermal Conductivity of Porous Ceramic Materials: Part 2, Refractories and Ceramics with Porosity Exceeding 30%

Abstract: A review of experimental results and theoretical models for thermal conductivities of ceramic materials with porosity less than 30% is given. It is shown that the abnormal non-monotonic pressure and temperature dependences of thermal conductivity arise from the effects of microcracks and porous grain boundaries, characterizing many industrial refractories, and from the competitive influences of classical and novel mechanisms of heat transfer in composite multiphase materials. The latter mechanisms include segregation and surface diffusion of impurities and defects in crystal structure, and the mechanism arising from chemical conversion and gas emission, occurring within pores of ceramic materials. A fractal model of porous materials' structure is proposed and used for analysis, explanation, and classification of thermophysical properties of ceramic materials measured in various thermodynamic conditions.

Thermal radiation heat transfer - Third edition

Abstract: The authors have revised this text to incorporate new general information, advances in analytical and computational techniques, and new reference material. Wide coverage focuses on thres subject areas: radiation from opaque surfaces, radiation interchange between various types of surfaces enclosing a vacuum or transparent medium, and radiation including the effects of partially transmitting media, such as combustion gases, soot, or windows.

Fluid flow, heat transfer, and solidification of molten metal droplets impinging on substrates: Comparison of numerical and experimental results

Abstract: A mathematical representation has been developed, and computed results are presented describing the spreading and solidification of droplets impacting onto a solid substrate. This impingement is of major practical interest in plasma spraying and spray forming operations. Experiments in which molten metal drops were made to impinge onto a substrate were used to test the model. High-speed videography was used to record the spreading process, which typically took a few milliseconds for the experimental conditions employed. A comparison was made of the theoretical predictions with the experimental measurements; these were found to be in very good agreement, suggesting that the theoretical treatment of the model is sound. These calculations permit the prediction of the time and extent of the spreading process, the solidification rate, and the effect of process parameters, such as droplet size, droplet velocity, superheat, and material properties, provided that a value of the thermal contact coefficient is known. The most important finding of the modeling work is that for large droplets (∼5-mm diameter) with low impinging velocities (∼2 m/s), spreading and solidification appear to take place at comparable rates; in contrast, for small (∼100−µm diameter) particles impacting at a high velocity (∼100 m/s), the time scale for spreading appears to be shorter than the time scale for solidification (within the range of parameters of this study.)

Modeling of Bioheat Transfer Processes at High and Low Temperatures

Abstract: Publisher Summary Heat transfer exhibits many therapeutic applications involving either a raising or lowering of temperature. It often requires precise monitoring of the spatial distribution of thermal histories that are produced during a protocol. The ability to perform accurate analysis of the heat transfer phenomena has led to a quantitative basis for describing the broad range of bioheat transfer processes that exist and in modeling the unique features of the flow of heat in living systems. This chapter presents a general background for the previous work in bioheat transfer. It describes the evolution of modeling techniques to deal with the special problems confronting the analysis of heat transfer processes in biosystems, both in vivo and in vitro. In specific, the chapter outlines the paths that are followed in arriving at the present state-of-the-art in several important areas of bioheat transfer modeling. It addresses the techniques for the modeling of many of the most important and commonly encountered examples of heat transfer processes in living systems.

Method and apparatus for temperature control of multiple samples

Abstract: Independent control of multiple samples which are in close proximity. All the samples in a sample container designed for rapid heat transfer and can be independently regulated to a set point using a temperature feedback control with the temperature monitored by a temperature sensitive element. This is implemented by heating each sample independently and at the same time a cooling device produces a substantial and continuous heat flow from the sample in order to permit an adequate rate of cooling when required. The rate of heat flow through the cooling device is partly determined by a thermal resistance which is included to control the pattern and maximum rate of heat flow to designed levels. By keeping the thermal mass of the temperature controlled components to a minimum it is also possible to change the temperature of the samples very rapidly.

Scaling relations in thermal turbulence: The aspect-ratio dependence

Abstract: We report scaling relations of thermal turbulence in cells of aspect ratio 0.5, 1.0, and 6.7.

Orthotropic Thermal Conductivity of Plain-Weave Fabric Composites Using a Homogenization Technique

Abstract: This article presents a new application of two-scale asymptotic homogenization schemes to predict the orthotropic thermal conductivity of plain-weave fabric reinforced composite laminates. A unit-cell, enclosing the characteristic periodic repeat pattern in the fabric weave, is isolated and modeled. A new three-dimensional series-parallel thermal resistance network is developed to solve a steady-state heat transfer boundary value problem (BVP) for this unit-cell. Laminate effective orthotropic thermal conductivities are obtained analytically and numerically as functions of (1) thermal conductivity of the constituent materials, (2) fiber volume fraction, and (3) weave style. The analytically predicted thermal conductivity values are compared with numerical finite element predictions, with existing models in the literature and with experimentally obtained values. 27 refs.