Showing papers on "Heat transfer published in 1985"

Fundamentals of Heat and Mass Transfer

Abstract: This undergraduate-level engineering text introduces the physical effects underlying heat and mass transfer phenomena and develops methodologies for solving a variety of real-world problems.

Introduction to Heat Transfer

Abstract: This book, designed for advanced undergraduate engineering majors, explains the physical concepts and methodologies of heat and mass transfer. It uses a systematic method for problem solving and discusses the relationship of heat and mass transfer to many important practical applications through examples and problems. A and significant contribution is the extensive use of the First Law of thermodynamics.

Heat transfer / a basic approach

Abstract: Heat transfer: a basic approach , Heat transfer: a basic approach , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Inverse heat conduction

Abstract: This book discusses the engineering problem of determining surface heat flux and temperature history based on interior temperature measurements. It also provides the analytical techniques needed to arrive at otherwise difficult solutions, summarizing the findings of the last ten years. Topics include the steady state solution, Duhammel's Theorem, ill-posed problems, single future time step, and more.

Handbook of Heat Transfer Fundamentals

Abstract: This handbook is on the fundamentals of heat transfer. It provides coverage on conduction, convection, and radiation and on thermophysical properties of materials.

A New Simplified Bioheat Equation for the Effect of Blood Flow on Local Average Tissue Temperature

Abstract: A new simplified three-dimensional bioheat equation is derived to describe the effect of blood flow on blood-tissue heat transfer. In two recent theoretical and experimental studies [1, 2] the authors have demonstrated that the so-called isotropic blood perfusion term in the existing bioheat equation is negligible because of the microvascular organization, and that the primary mechanism for blood-tissue energy exchange is incomplete countercurrent exchange in the thermally significant microvessels. The new theory to describe this basic mechanism shows that the vascularization of tissue causes it to behave as an anisotropic heat transfer medium. A remarkably simple expression is derived for the tensor conductivity of the tissue as a function of the local vascular geometry and flow velocity in the thermally significant countercurrent vessels. It is also shown that directed as opposed to isotropic blood perfusion between the countercurrent vessels can have a significant influence on heat transfer in regions where the countercurrent vessels are under 70-micron diameter. The new bioheat equation also describes this mechanism.

Combined Heat Transfer and Fluid Dynamic Measurements Downstream of a Backward-Facing Step

Abstract: Combined heat transfer and fluid dynamic measurements in a separated and reattaching boundary layer, with emphasis on the near-wall region, are presented. A constant heat-flux surface behind a single-sided sudden expansion is used to obtain Stanton number profiles as a function of Reynolds number and boundary-layer thickness at separation. Fluctuating skin-friction and temperature profiles demonstrate the importance of the near-wall region in controlling the heat transfer rate. The fluctuating skin friction controls the heat transfer rate near reattachment, while the conventional Reynolds analogy applies in the redeveloping boundary layer beginning two or three step heights downstream of reattachment.

Solar thermal energy storage

Abstract: 1 Importance and modes of energy storage.- 1.1 The importance of energy storage.- 1.2 Influence of type and extent of mismatch on storage.- 1.3 Size and duration of storage.- 1.4 Applications.- 1.4.1 Stationary applications.- 1.4.2 Transport applications.- 1.5 Quality of energy and modes of energy storage.- 1.6 Thermal energy storage.- 1.6.1Sensible heat storage.- 1.6.2 Storage in phase change materials (PCM).- 1.7 Mechanical energy storage.- 1.7.1 Storage as potential energy.- 1.7.2 Storage as kinetic energy.- 1.7.3 Energy storage in a compressed gas.- 1.8 Electrical and magnetic energy storage.- 1.8.1 Storage in electrical cap ac i tors.- 1.8.2 Storage in electromagnets.- 1.8.3 Storage in magnets with superconducting coils.- 1.8.4 Storage in a battery.- 1.9 Chemical energy storage.- 1.9.1 Synthetic fuels.- 1.9.2 Thermochemical storage.- 1.9.3 Electrochemical storage.- 1.9.4 Photochemical storage.- References.- 2 Sensible heat storage.- 2.1 Sensible heat storage basics.- 2.2 Sensible heat storage and type of load.- 2.3 Sensible heat storage media.- 2.4 Well-mixed liquid storage.- 2.5 Stratified liquid storage.- 2.5.1 Analytical studies on thermally stratified hot water tanks.- 2.5.2 Experimental studies on thermally stratified hot water storage tanks.- 2.5.3 Forced stratification in liquids.- 2.6 Containers for water storage.- 2.7 Packed bed storage system.- References.- Appendix -I.- Appendix - II.- 3 Latent heat or phase change thermal energy storage.- 3.1 Basics of latent heat storage.- 3.1.1 Heat of fusion (Latent heat).- 3.1.2 Employment of latent heat storage system.- 3.2 Liquid-solid transformation.- 3.2.1 Nucleation and supercooling.- 3.2.2 The rate of crystal growth.- 3.2.3 Types of solidification or crystallization.- 3.2.4 Melting and freezing characteristics.- 3.2.5 Interpretation of freezing curves.- 3.2.6 Relative rates of heat and mass transport.- 3.2.7 Binary phase diagrams.- 3.3 Phase change materials (PCM).- 3.3.1 Solid-solid transitions.- 3.3.2 Solid-liquid transformations.- i) Salt hydrates.- ii) Other inorganic compounds.- iii) Paraffins.- iv) Non paraffin organic solids.- v) Clathrate and semi-clathrate hydrates.- vi)Eutectics.- 3.4 Selection of PCM.- 3.5 Storage in salt hydrates.- 3.5.1 Nucleation and crystallization.- 3.5.2 Incongruent melting.- 3.5.3 Thickening agents.- 3.5.4 Some promising salt hydrates and the binary phase diagrams.- 3.6 Prevention of incongruent melting and thermal cycling.- 3.6.1 Thickening agents.- 3.6.2 Extra water principle.- 3.6.3 Rolling cylinder method.- 3.6.4 Adding SrCl2 6H2 C in CaCl2 H2O system.- 3.7 Storage in paraffins.- 3.8 Heat transfer in PCM.- 3.8.1 Freezing of tops of ponds.- 3.8.2 An approximate analytical model for a periodic process.- 3.8.3 Heat-exchange with fluid-flow between trays holding PCM.- 3.9 Heat exchange arrangement and containment of PCM.- 3.9.1 Encapsulation of PCM.- 3.9.2 Containment.- 3.9.3 Compatibility.- 3.9.4 Special heat exchangers for PCM.- (A) Passive systems.- (B) Active systems.- 3.10 Storage in PCM undergoing solid-solid transition.- 3.10.1 Storage in modified high density polyethylene (HDPE).- 3.10.2 Storage in layer perovskites and other organometallic compounds.- 3.11 Heat of solution storage and heat exchangers.- 3.11.1 Crystallization from saturated solution.- 3.11.2 Heat exchangers in heat-of-solution storage system.- References.- 4 Chemical energy storage.- 4.1 Introduction.- 4.2 Selection Criterion.- 4.2.1 Thermodynamic considerations.- 4.2.2 Reversibility.- 4.2.3 Reaction rates.- 4.2.4 Controllability.- 4.2.5 Ease of storage.- 4.2.6 Safety.- 4.2.7 Availability and Cost.- 4.2.8 Product separation.- 4.2.9 Reaction with water and oxygen.- 4.2.10 Technology.- 4.2.11 Catalyst availability and lifetime.- 4.3 Energy storage in thermal dissociation type of reactions.- 4.3.1 Thermal dissociation of SO3.- 4.3.2 Dissociation of Ammonia.- 4.3.3 Thermal dissociation of inorganic hydroxides.- 4.3.4 Thermal decomposition of carbonates.- 4.3.5 Decomposition of sulfates.- 4.3.6 Thermal decomposition of CS2.- 4.3.7 Organic hydrogenation/dehydrogenation reaction.- 4.3.8 Thermal dissociation of ammoniated salts.- 4.3.9 Oxides-Peroxides and super oxides decomposition.- 4.3.10 Hydride decomposition.- 4.3.11 The reaction N2 O4 2N0+02.- 4.4 Methane based reactions.- 4.5 Heat transformation (HT) and chemical heat pumps (CHP).- 4.5.1 Working materials for CHP and HT.- 4.5.2 Thermal efficiency of CHP cycles.- 4.5.3 Ammoniates based CHP.- 4.5.4 Salt hydrates in chemical heat pump.- 4.5.5 Hydrides in CHP and HT.- 4.5.6 Methanolated salts.- 4.5.7 Heat of solution systems.- 4.6 Three step approach.- 4.7 Energy storage by adsorption.- References.- 5 Longterm energy storage.- 5.1 Solar ponds.- 5.1.1 Classification of solar ponds.- i) Shallow solar pond.- ii) Salt gradient solar ponds.- iii) Partitioned solar pond (PSP).- iv) Viscosity stabilized ponds.- v) Membrane stratified solar pond.- vi) Saturated solar pond.- 5.1.2 Thermal stability of solar ponds.- 5.1.3 Salt properties.- 5.1.4 Passage of solar insolation into solar pond.- 5.1.5 Creation and maintenance of solar pond.- 5.1.6 Performance analysis of a solar pond.- 5.1.7 Heat extraction.- 5.1.8 Applications.- i) Space heating.- ii) Domestic water or swimming pool heating.- iii) Industrial process heat.- iv) Power production.- v) Desalination.- 5.1.9 Some remarks.- 5.2 Energy storage in aquifers.- 5.2.1 Operational strategies.- 5.2.2 Theoretical studies.- 5.2.3 Characteristics of the aquifer.- 5.3 Heat storage in underground water tanks.- 5.4 Heat storage in the ground.- References.- 6 Energy storage in building materials.- 6.1 Introduction.- 6.2 Basic passive designs.- 6.2.1 Direct gain systems.- 6.2.2 Convective loops.- 6.2.3 Thermal storage walls.- 6.2.4 Roof ponds.- 6.2.5 Attached sunspace.- 6.3 PCM in building panels.- 6.4 Experiments on PCM building panels.- 6.5 Applications.- References.- 7 High temperature heat storage.- 7.1 Introduction.- 7.2 Techniques for thermal energy storage.- 7.3 Sensible heat storage systems.- 7.3.1 Rock bed storage system.- 7.3.2 Rock bed-liquid (Dual medium) storage system.- 7.3.3 Two stage thermal storage in unpressurized liquids.- 7.3.4 Molten slag storage system.- 7.3.5 Thermal storage in large hollow steel ingots.- 7.3.6 Thermal energy storage in sand (fluidized bed).- 7.4 Phase change energy storage systems and ceramic pellets.- 7.4.1 Phase change salt and ceramic 570 pellets with air as working fluid.- 7.4.2 Phase change salt/metal storage systems.- 7.4.3 Phase change storage material with heat exchanger.- 7.4.4 Energy storage boiler.- 7.4.5 Storage heat in PCM and use of scraper for removing solid boundary layer.- 7.5 Chemical reactions.- 7.5.1 Catalytic decomposition reactions.- 7.5.2 Thermal dissociation reactions.- References.- 8 Testing of thermal energy storage system.- 8.1 Introduction.- 8.2 Historical development.- 8.3 Related studies.- 8.4 Basis and evolution of testing procedures.- 8.5 Standard procedure.- 8.5.1 ASHRAE 94-77.- 8.5.2 NBSIR 74-634.- 8.6 Some comments.- References.- Appendices.- Appendix 1 Conversion of units.- Appendix 2 Physical properties of some solid materials.- Appendix 3 Physical properties of some building and insulating materials.- Appendix 4 Physical properties of some liquids.- Appendix 5 Physical properties of some liquid metals.- Appendix 6 Physical properties of saturated water.- Appendix 7 Physical properties of saturated steam.- Appendix 8 Physical properties of some gases.- Appendix 9 Physical properties of dry air at atmospheric pressure.- Appendix 10 Freezing points of aqueous solutions.- Appendix11 Properties of typical refrigerants.- Appendix 12 Storage capacities.- Appendix 13 Properties of some promising latent-heat thermal energy storage materials.- Appendix 14 Solubility behavior of candidate salts for salt-gradient solar pond.

Thermal evolution models for the Earth

Abstract: Thermal evolution models for the earth which are based on a parameterization of the convective heat transport are critically reexamined. Traditionally, it has been assumed that the temperature dependence of the mantle viscosity implies that internal temperature and convective heat loss are strongly coupled. Recent numerical work on the heat transport by variable viscosity convection demonstrates that the dependence of the heat flow on the mantle temperature may in fact be much weaker than expected. I compare thermal evolution models with strong and weak dependence of the heat loss on the temperature. With the weaker dependence, plate velocities and heat flow in the Archean were not more than 50% higher than today, while with the strong dependence, much larger differences are predicted. In the former case the Archaean mantle temperatures are somewhat higher, and the present-day ratio of radioactive heat production over heat loss (Urey ratio) is 50% or slightly less. The Urey ratios in the traditional parameterized evolution models are >70%. The predictions of both kinds of models are compared with the independent geological, geochemical, and palaeomagnetic evidence. Although this evidence is subject to some uncertainties, it favors in every case the evolution models based on a weak coupling of heat loss to the interior temperature.

Metal-Mold interfacial heat transfer

Abstract: During the solidification of metal castings, an interfacial heat transfer resistance exists at the boundary between the metal and the mold. This heat transfer resistance usually varies with time even if the cast metal remains in contact with the mold, due to the time dependence of plasticity of the freezing metal and oxide growth on the surface. The present work has studied interfacial heat transfer on two related types of castings. In the first type, a copper chill was placed on the top of a cylindrical, bottom gated casting. Using the techniques of transducer displacements and electrical continuity, a clearance gap was detected between the solidified metal and the chill. The second type of casting had a similar design except that the chill was placed at the bottom. Owing to the effect of gravity, solid to solid contact was maintained at the metal-chill interface, but the high degree of interface nonconformity resulted in a relatively low thermal conductance as indicated by solution of the inverse heat conduction problem. Finally, the influence of interfacial heat transfer on solidification time with three mold ma-terials is compared by a numerical example, and criteria for utilizing Chvorinov's rule are discussed.

Three-dimensional treatment of convective flow in the earth's mantle

Abstract: A three-dimensional finite-element method is used to investigate thermal convection in the earth's mantle. The equations of motion are solved implicitly by means of a fast multigrid technique. The computational mesh for the spherical problem is derived from the regular icosahedron. The calculations described use a mesh with 43,554 nodes and 81,920 elements and were run on a Cray X. The earth's mantly is modeled as a thick spherical shell with isothermal, free-slip boundaries. The infinite Prandtl number problem is formulated in terms of pressure, density, absolute temperature, and velocity and assumes an isotropic Newtonian rheology. Solutions are obtained for Rayleigh numbers up to approximately 106 for a variety of modes of heating. Cases initialized with a temperature distribution with warmer temperatures beneath spreading ridges and cooler temperatures beneath present subduction zones yield whole-mantle convection solutions with surface velocities that correlate well with currently observed plate velocities.

A method of calculating radiative heat diffusion in particle simulations

Abstract: A new method for solving heat diffusion in three dimensional particle simulations is described. The difficulties encounted by other authors is discussed, in particular the difficulty of including boundary conditions in particle simulations. One and three dimensional tests of the method are described.

On ‘‘Radiative transfer in three-dimensional rectangular enclosures containing inhomogeneous,anisotropically scattering media’’

Abstract: Our 1985 paper (JQSRT 1985; 33: 533–549) reported the result of the research we conducted back then to better understand heat transfer processes in large-scale combustion chambers, especially in pulverized coal-fired furnaces. It was one of the first works exploring radiative transfer in three-dimensional enclosures where absorption and scattering coefficients due to combustion particles and gases were allowed to vary within the medium. This flexibility of the mathematical model made it useful for applications to realistic furnaces and different types of high-temperature systems. This note briefly discusses the motivation behind the paper and the immediate extension of the idea to different systems.

Enhanced heat conduction in oscillating viscous flows within parallel-plate channels

Abstract: The hydrodynamics of enhanced longitudinal heat transfer through a sinusoidally oscillating viscous fluid in an array of parallel-plate channels with conducting sidewalls is examined analytically. Results show that for fixed frequency the corresponding effective thermal diffusivity reaches a maximum when the product of the Prandtl number and the square of the Womersley number is approximately equal to α2 Pr = π Under such tuned conditions the axial heat transfer achievable is considerable and can exceed that possible with heat pipes by several orders of magnitude. The heat flux between different temperature reservoirs connecting the parallel-plate-channel configuration is shown, under tuned conditions, to be proportional to the first power of both the axial temperature gradient and the flow oscillation frequency and to the square of the tidal displacements. A large value for the fluid density and specific heat is also found to be beneficial when large heat-transfer rates are desired. The process discussed involves no net convection and hence achieves large heat-transfer rates (in excess of 106 W/cm2) without a corresponding net convective mass transfer. A discussion of the physical origin for this new heat-transfer process is given and suggestions for applications are presented.

Particle dynamics and particle heat and mass transfer in thermal plasmas. Part I. The motion of a single particle without thermal effects

Abstract: A particle injected into a thermal plasma will experience a number of effects which are not present in an ordinary gas. In this paper effects exerted on the motion of a particle will be reviewed and analyzed in the context of thermal plasma processing of materials. The primary purpose of this paper is an assessment of the relative importance of various effects on particle motion. Computer experiments are described, simulating motion of a spherical particle in a laminar, confined plasma jet or in a turbulent, free plasma jet. Particle sizes range from 5 to 50 µm, and as sample materials alumina and tungsten are considered. The results indicate that (i) the correction term required for the viscous drag coefficient due to strongly varying properties is the most important factor; (ii) non-continuum effects are important for particle sizes <10 µm at atmospheric pressure and these effects will be enhanced for smaller particles and/or reduced pressures; (iii) the Basset history term is negligible, unless relatively large and light particles are considered over long processing distances; (iv) thermophoresis is not crucial for the injection of particles into thermal plasmas; (v) turbulent dispersion becomes important for particle <10 µm in diameter.

A Model for Predicting Spatially and Time Resolved Convective Heat Transfer in Bowl-in-Piston Combustion Chambers

Abstract: A new model for convective in-cylinder heat transfer has been developed which calculates heat transfer coefficients based on a description of the in-cylinder flow field. The combustion chamber volume is divided into three regions in which differential equations for angular momentum, turbulent kinetic energy and turbulent dissipation are solved. The resultant heat transfer coefficients are strongly spatially non-uniform, unlike those calculated from standard correlations, which assume spatial uniformity. When spatially averaged, the heat transfer coefficient is much more peaked near TDC of the compression stroke as compared to that predicted by standard correlations. This is due to the model's dependence on gas velocity and turbulence, both of which are amplified near TDC. The new model allows a more accurate calculation of the spatial distribution of the heat fluxes. This capability is essential for calculation of heat transfer and of component thermal loading and temperatures.

Planar laser-driven ablation: Effect of inhibited electron thermal conduction

Abstract: A model for planar laser‐driven ablation is presented, including the effects of inhibited electron thermal conduction. Localized deposition of laser energy at the critical‐density surface is assumed. A steady‐state solution in the conduction zone is joined to a rarefaction wave in the underdense corona. The global flow structure is calculated, as well as the ablation pressure, ablation rate, and hydrodynamic efficiency. Criteria are developed for the importance of the inertial force caused by the acceleration of the slab. The results agree well with time‐dependent computer simulations using a Lagrangian hydrodynamics code.

a Numerical Study of Two-Dimensional Natural Convection in Square Open Cavities

Abstract: A numerical study of natural convection in a two-dimensional square open cavity under laminar steady-state conditions has been performed. The square cavity has one heated vertical wall facing a vertical opening and two insulated horizontal walls. Results are obtained for Rayleigh numbers ranging from 103 to 109 at unit Prandtl number with constant properties and the Boussinesq approximation. Heat transfer results approach those for an isothermal vertical flat plate at high Rayleigh numbers. Streamline and isotherm plots illustrate the effect of the open boundary on the basic flow patterns. A recirculation zone is found at high Rayleigh numbers above the bottom wall due to incoming flow turning around the corner. Thermally stratified flow below the top wall exits to form a wall plume.

Fouling of Heat Transfer Surfaces Related to β-Lactoglobulin Denaturation During Heat Processing of Milk

Abstract: Denaturation of beta-lactoglobulin during heating of milk in a plate heat exchanger has been investigated as an important factor in fouling the heat transfer surface. Using, on one hand, data on chemical composition of deposits obtained from biochemical analysis technics and, on the other hand, kinetic data of beta-Iactoglobulin denaturation, the distribution profile of deposits along the surface and the experimental fouling curves can be adequately predicted.

Particle Dynamics and Particle Heat and Mass Transfer in Thermal Plasmas. Part II. Particle Heat and Mass Transfer in Thermal Plasmas

Abstract: This paper is concerned with a review of heat and mass transfer between thermal plasmas and particulate matter. In this situation various effects which are not present in ordinary heat and mass transfer have to be considered, including unsteady conditions, modified convective heat transfer due to strongly varying plasma properties, radiation, internal conduction, particle shape, vaporization and evaporation, noncontinuum conditions, and particle charging. The results indicate that (i) convective heat transfer coefficients have to be modified due to strongly varying plasma properties; (ii) vaporization, defined as a mass transfer process corresponding to particle surface temperatures below the boiling point, describes a different particle heating history than that of the evaporation process which, however, is not a critical control mechanism for interphase mass transfer of particles injected into thermal plasmas; (iii) particle heat transfer under noncontinuum conditions is governed by individual contributions from the species in the plasma (electrons, ions, neutral species) and by particle charging effects.

Hydrodynamics of fluidization: Prediction of wall to bed heat transfer coefficients

Abstract: A computer model for a hot fluidized bed was developed. The large heat transfer coefficients characteristic of fluidized beds were computed without an enhancement of heat transfer by turbulence. They agreed with measurements reported by Ozkaynak and Chen (1980) within the accuracy of estimated thermal conductivity of solids.