scispace - formally typeset
Search or ask a question

Showing papers on "Heat transfer published in 1998"


Journal ArticleDOI
TL;DR: In this article, the authors used a Brookfield rotating viscometer to measure the viscosities of the dispersed fluids with γ-alumina (Al2O3) and titanium dioxide (TiO2) particles at a 10% volume concentration.
Abstract: Turbulent friction and heat transfer behaviors of dispersed fluids (i.e., uttrafine metallic oxide particles suspended in water) in a circular pipe were investigated experimentally. Viscosity measurements were also conducted using a Brookfield rotating viscometer. Two different metallic oxide particles, γ-alumina (Al2O3) and titanium dioxide (TiO2), with mean diameters of 13 and 27 nm, respectively, were used as suspended particles. The Reynolds and Prandtl numbers varied in the ranges l04-I05 and 6.5-12.3, respectively. The viscosities of the dispersed fluids with γ-Al2O3 and TiO2 particles at a 10% volume concentration were approximately 200 and 3 times greater than that of water, respectively. These viscosity results were significantly larger than the predictions from the classical theory of suspension rheology. Darcy friction factors for the dispersed fluids of the volume concentration ranging from 1% to 3% coincided well with Kays' correlation for turbulent flow of a single-phase fluid. The Nusselt n...

3,730 citations


Journal ArticleDOI
TL;DR: A novel lattice Boltzmann thermal model is proposed for studying thermohydrodynamics in incompressible limit that can incorporate viscous heat dissipation and compression work done by the pressure, in contrast to the passive-scalar-based thermal latticeboltzmann models.

1,243 citations


Journal ArticleDOI
TL;DR: In this paper, the dynamic thermoelastic response of functionally graded cylinders and plates is studied, and a finite element model of the formulation is developed, where the heat conduction and the thermo-elastic equations are solved for a functionally graded axisymmetric cylinder subjected to thermal loading.
Abstract: The dynamic thermoelastic response of functionally graded cylinders and plates is studied. Thermomechanical coupling is included in the formulation, and a finite element model of the formulation is developed. The heat conduction and the thermoelastic equations are solved for a functionally graded axisymmetric cylinder subjected to thermal loading. In addition, a thermoelastic boundary value problem using the first-order shear deformation plate theory (FSDT) that accounts for the transverse shear strains and the rotations, coupled with a three-dimensional heat conduction equation, is formulated for a functionally graded plate. Both problems are studied by varying the volume fraction of a ceramic and a metal using a power law distribution.

1,196 citations


Journal ArticleDOI
TL;DR: In this article, the development of available thermal energy storage (TES) technologies and their individual pros and cons for space and water heating applications are reviewed and compared for low temperature applications, where water is used as a storage medium.

1,156 citations


Journal ArticleDOI
TL;DR: In this article, an experimental study of heat transfer and flow regimes during condensation of refrigerants in horizontal tubes was conducted, where measurements were made in smooth, round tubes with diameters ranging from 3.14 mm to 7.04 mm.
Abstract: An experimental study of heat transfer and flow regimes during condensation of refrigerants in horizontal tubes was conducted. Measurements were made in smooth, round tubes with diameters ranging from 3.14 mm to 7.04 mm. The refrigerants tested were R-12, R-22, R-134a, and near-azeotropic blends of R-32/R-125 in 50 percent/50 percent and 60 percent/40 percent compositions. The study focused primarily on measurement and prediction of condensing heat transfer coefficients and the relationship between heat transfer coefficients and two-phase flow regimes. Flow regimes were observed visually at the inlet and outlet of the test condenser as the heat transfer data were collected. Stratified, wavy, wavy annular, annular, annular mist, and slug flows were observed. True mist flow without a stable wall film was not observed during condensation tests. The experimental results were compared with existing flow regime maps and some corrections are suggested. The heat transfer behavior was controlled by the prevailing flow regime. For the purpose of analyzing condensing heat transfer behavior, the various flow regimes were divided into two broad categories of gravity-dominated and shear-dominated flows. In the gravity dominated flow regime, the dominant heat transfer mode was laminar film condensation in the top of the tube. This regime was characterized by heat transfer coefficients that depended on the wall-to-refrigerant temperature difference but were nearly independent of mass flux. In the shear-dominated flow regime, forced-convective condensation was the dominant heat transfer mechanism. This regime was characterized by heat transfer coefficients that were independent of temperature difference but very dependent on mass flux and quality. Heat transfer correlations that were developed for each of these flow regimes successfully predicted data from the present study and from several other sources.

673 citations


Journal ArticleDOI
TL;DR: In this paper, an analog between convection and conduction with heat sources is made to have a further understanding of the mechanism of convective heat transfer, and three ways to raise the strength of heat sources/convection terms, and consequently to enhance the heat transfer are presented.

654 citations


Journal ArticleDOI
TL;DR: In this paper, a variety of liquid droplet evaporation models, including both classical equilibrium and non-equilibrium Langmuir-Knudsen formulations, are evaluated through comparisons with experiments with particular emphasis on computationally efficient procedures for gas-liquid flow simulations.

586 citations


Journal ArticleDOI
TL;DR: In this paper, a review examines recent advances made in predicting boiling heat fluxes, including some key results from the past, including nucleate boiling, maximum heat flux, transition boiling, and film boiling.
Abstract: ▪ Abstract This review examines recent advances made in predicting boiling heat fluxes, including some key results from the past. The topics covered are nucleate boiling, maximum heat flux, transition boiling, and film boiling. The review focuses on pool boiling of pure liquids, but flow boiling is also discussed briefly.

575 citations


Book
22 May 1998
TL;DR: In this paper, the analogy between heat and mass transfer is covered and applied in the analysis of heat transfer by conduction, convection and radiation, and the analysis is performed by using the handbook of numerical heat transfer.
Abstract: Handbook of Numerical Heat Transfer Free Full Download Links from Multiple Mirrors added by DL4W on 2015-04-10 02:13:35. Handbook of heat transfer / editors, W.M. Rohsenow, J.P. Hartnett. Y.I. Cho. m 3rd ed. p. cm. Includes bibliographical references and index. ISBN 0-07053555-8. Students investigate heat transfer by conduction, convection and radiation. The analogy between heat and mass transfer is covered and applied in the analysis.

564 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical model is developed for model foams with simple cubic unit cells consisting of heated slender cylinders, based on existing heat transfer data on convective crossflow through cylinder banks.

558 citations


Book
13 Jan 1998
TL;DR: In this paper, the authors present an overview of scalar, vector, and tensor notations for the collision mechanics of solids in a gas-solid flow and their relationship with heat and mass transfer.
Abstract: Part I Basic Relationships: 1 Size and properties of particles 2 Collision mechanics of solids 3 Momentum transfer and charge transfer 4 Basic heat and mass transfer 5 Basic equations 6 Intrinsic phenomena in a gas-solid flow Part II System Characteristics: 7 Gas-solid separation 8 Hopper and stand pipe flows 9 Dense-phase fluidized beds 10 Circulating fluidized beds 11 Pneumatic conveying of solids 12 Heat and mass transfer phenomena in fluidization systems Appendix Summary of scalar, vector, and tensor notations

Journal ArticleDOI
TL;DR: In this article, a numerical method to simulate liquid-vapor phase change is presented, based on the so-called single field formulation where one set of equations for conservation of mass, momentum and energy are written for the entire flow field.

Journal ArticleDOI
TL;DR: In this article, the analysis of laminar mixed convection in boundary layers adjacent to a vertical, continuously stretching sheet has been presented, where the velocity and temperature of the sheet were assumed to vary in a power-law form.
Abstract: The analysis of laminar mixed convection in boundary layers adjacent to a vertical, continuously stretching sheet has been presented. The velocity and temperature of the sheet were assumed to vary in a power-law form, that is, u w (x)=Bx m and T w (x)−T ∞=Ax n . In the presence of buoyancy force effects, similarity solutions were reported for the following two cases: (a) n=0 and m=0.5, which corresponds to an isothermal sheet moving with a velocity of the form u w =Bx 0.5 and (b) n=1 and m=1, which corresponds to a continuous, linearly stretching sheet with a linear surface temperature distribution, i.e. T w −T ∞=Ax. Formulation of the present problem shows that the heat transfer characteristics depends on four governing parameters, namely, the velocity exponent parameter m, the temperature exponent parameter n, the buoyancy force parameter G *, and Prandtl number of the fluid. Numerical solutions were generated from a finite difference method. Results for the local Nusselt number, the local friction coefficient, and temperature profiles are presented for different governing parameters. Effects of buoyancy force and Prandtl number on the flow and heat transfer characteristics are thoroughly examined.

Journal ArticleDOI
TL;DR: In this paper, a heat transfer model for intube flow boiling in horizontal plain tubes is proposed that incorporates the effects of local two-phase flow patterns, flow stratification and partial dryout in annular flow.
Abstract: A new heat transfer model for intube flow boiling in horizontal plain tubes is proposed that incorporates the effects of local two-phase flow patterns, flow stratification and partial dryout in annular flow. Significantly, the local peak in the heat transfer coefficient versus vapor quality can now be determined from the prediction of the location of onset of partial dryout in annular flow. The new method accurately predicts a large, new database of flow boiling data, and is perticularly better than existing mehods at high vapor qualities (x > 85%) and for stratified types of flows.

Journal ArticleDOI
TL;DR: In this paper, an experiment was carried out to investigate the characteristics of the evaporation heat transfer and pressure drop for refrigerant R-134a flowing in a horizontal small circular pipe having an inside diameter of 2.0 mm.

Journal ArticleDOI
TL;DR: In this paper, direct numerical simulations of the turbulent heat transfer for various Prandtl numbers ranging from 0.025 to 5 are performed to obtain statistical quantities such as turbulent heat flux, temperature variance and their budget terms.

Journal ArticleDOI
TL;DR: The use of the Monte Carlo method in radiative heat transfer is reviewed in this paper, where surface-surface, enclosure, and participating media problems are considered, as well as the effects of using parallel algorithms.
Abstract: The use of the Monte Carlo method in radiative heat transfer is reviewed. The review covers surface-surface, enclosure, and participating media problems. Discussio. is included of research on the fundamentals of the method and on applications to surface-surface interchange in enclosures, exchange between surfaces with roughness characteristics, determination of configuration factors, inverse design, transfer through packed beds and fiber layers, participating media, scattering, hybrid methods, spectrally dependent problems including media with line structure, effects of using parallel algorithms, practical applications, and extensions of the method. Conclusions are presented on needed future work and the place of Monte Carlo techniques in radiative heat transfer computations

Book
01 Jan 1998
TL;DR: In this article, the authors present a review of the application of heat transport in dielectric thin films and at Solid-Solid Interfaces, as well as their application in biological systems at low temperatures.
Abstract: Preface Contributors Part I Fundamentals 1.Microscale Energy Transport in Solids 2.Heat Transport in Dielectric Thin Films and at Solid-Solid Interfaces 3.Microscale Radiation Phenomena 4.Melting and Freezing Phenomena 5.Molecular Clusters 6.Interfacial Forces and Phase Change in Thin Liquid Films Part II.Applications 7.Thermal Phenomena in Semiconductor Devices and Interconnects 8.Micro Heat Pipes 9.Microscale Heat Transfer in Biological Systems at Low Temperatures 10.Silicon Micromachined Thermal Sensors and Actuators Index

Journal ArticleDOI
TL;DR: In this article, the authors used a trans-critical CO 2 process for tap water heating and achieved a heating-COP of 4.3 for an Oslo climate, using ambient air as heat source.
Abstract: CO 2 is one of the few non-toxic and non-flammable working fluids that do not contribute to ozone depletion or global warming, if leaked to the atmosphere. Tap water heating is one promising application for a trans-critical CO 2 process. The temperature glide at heat rejection contributes to a very good temperature adaptation when heating tap water, which inherits a large temperature glide. This, together with efficient compression and good heat transfer characteristics of CO 2 , makes it possible to design very efficient systems. A heating-COP of 4.3 is achieved for the prototype when heating tap water from 9°C to 60°C, at an evaporation temperature of 0°C. The results lead to a seasonal performance factor of about 4 for an Oslo climate, using ambient air as heat source. Thus, the primary energy consumption can be reduced with more than 75% compared with electrical or gas fired systems. Another significant advantage of this system, compared with conventional heat pump water heaters, is that hot water with temperatures up to 90°C can be produced without operational difficulties.

Journal ArticleDOI
TL;DR: In this paper, the effects of the electric double layer near the solid-liquid interface and the flow induced electrokinetic field on the pressure-driven flow and heat transfer through a rectangular microchannel are analyzed.

Journal ArticleDOI
TL;DR: In this paper, the authors used the renoramlization group (RNG) k-e turbulence model for the prediction of buoyant air flow and flow rate in enclosures with Trombe wall geometries.

Journal ArticleDOI
J. Y. Murthy, S. R. Mathur1
TL;DR: In this paper, a cell-based numerical scheme is devised for computing radiative heat transfer using meshes composed of arbitrary unstructured polyhedra, which is shown to be robust and accurate through comparisons with published solutions.
Abstract: The e nite volume method has been shown to accurately predict radiative heat transfer in absorbing, emitting, and scattering media. However, computations have for the most part been restricted to structured, body-e tted meshes. In this paper a conservative cell-based numerical scheme is devised for computing radiative heat transfer using meshes composed of arbitrary unstructured polyhedra. The method is shown to be robust and accurate through comparisons with published solutions.

Book
01 Jan 1998
TL;DR: In this paper, the authors proposed a density-driven flow model for Porous Media with an analytical approach based on the Fast-C(2D) model, which is a 2D model for water flow.
Abstract: 1 Introduction.- 1.1 Density-Driven Flow.- 1.2 Modeling.- 1.3 Modeling Density-driven Flow in Porous Media.- 1.4 FAST-C(2D) Modeling Software.- 2 Density and Other Water Properties.- 2.1 Dependence on Temperature.- 2.1.1 Density.- 2.1.2 Thermal Expansion Coefficient.- 2.1.3 Viscosity.- 2.1.4 Specific Heat Capacity.- 2.1.5 Thermal Conductivity.- 2.1.6 Diffusivity.- 2.2 Dependence on Salinity.- 2.2.1 Density.- 2.2.2 Viscosity.- 2.3 Dependence on Pressure.- 2.3.1 Density.- 2.3.2 Compressibility.- 3 Analytical Description.- 3.1 Basic Principles.- 3.2 Oberbeck-Boussinesq Assumption.- 3.3 Hydraulic Head Formulation.- 3.4 Streamfunction Formulation.- 3.5 Vorticity Equation.- 3.6 Extended Oberbeck-Boussinesq Assumption.- 3.7 Dimensionless Formulation.- 3.8 Boundary Layer Formulation.- 3.9 Heat and Mass Transfer.- 4 Numerical Modeling (Fast-C(2D)).- 4.1 Spatial Discretization.- 4.2 Temporal Discretization.- 4.3 Boundary Conditions.- 4.4 Initial Conditions and RESTART.- 4.5 Solution of the Nonlinear System.- 4.5.1 Newton Method and Variations.- 4.5.2 Picard Iterations.- 4.6 Solution of Linear Systems.- 4.6.1 Conjugate Gradients.- 4.7 Postprocessing.- 5 Steady Convection.- 5.1 Benard Experiments in Porous Medium.- 5.2 Linear Analysis.- 5.2.1 Isotropic Porous Medium.- 5.2.2 Anisotropic Porous Medium.- 5.3 Bifurcation Analysis.- 5.4 Numerical Experiments.- 5.4.1 Isotropic Porous Medium.- 5.4.2 Anisotropic Porous Medium.- 6 Special Topics in Convection.- 6.1 Thermal Convection in Slender Boxes.- 6.1.1 Analytical Studies.- 6.1.2 Numerical Experiments.- 6.2 Variable Viscosity Effects on Convection.- 6.2.1 Introduction.- 6.2.2 Onset of Convection.- 6.2.3 Heat Transfer.- 6.3 Convection in Cold Groundwater.- 6.3.1 Streamfunction Formulation.- 6.3.2 Onset of Convection.- 6.3.3 Flow Patterns.- 6.4 Relevance of Convection in Natural Systems.- 7 Oscillatory Convection.- 7.1 Hopf Bifurcation.- 7.2 Simulation.- 7.3 Influence of Numerical Parameters.- 8 Horizontal Heat and Mass Transfer.- 8.1 Analytical Approximations and Solutions.- 8.1.1 Convection.- 8.1.2 Conduction.- 8.2 Numerical Experiments.- 8.2.1 Conduction.- 8.2.2 Convection.- 9 Elder Experiment.- 9.1 Laboratory Experiment.- 9.2 Numerical Experiments.- 9.2.1 Elder's Model.- 9.2.2 FAST-C(2D) Model.- 9.2.3 Further Models.- 9.3 Related Problems.- 10 Geothermal Flow (Yusa's Example).- 10.1 Hypothetical Situation and Analytical Description.- 10.2 Flow Pattern Characterization.- 10.3 Sensitivity Analysis.- 10.4 Other Geothermal Systems.- 11 Saltwater Intrusion (Henry's Example).- 11.1 Problem Description.- 11.2 Sharp Interface Approach.- 11.3 Henry's Example.- 11.4 Modeling Saltwater Intrusion.- 11.4.1 Henry's Example.- 11.4.2 Parameter Variation.- 11.4.3 Layered Aquifers.- 12 Saltwater Upconing.- 12.1 Problem Description.- 12.2 Modeling Saltwater Upconing.- 12.2.1 Sharp Interface Approach.- 12.2.2 Miscible Displacement.- 12.2.3 Variable Density Effects.- 12.3 Case Study.- 13 Flow Across a Salt-Dome.- 13.1 Salt Formations and Scenarios.- 13.2 HYDROCOIN Test-Case.- 13.3 Modeling the HYDROCOIN Test-Case.- 13.4 FAST-C(2D) Model.- 14 Desert Sedimentary Basins.- 14.1 System Description.- 14.2 Numerical Modeling.- Concluding Remark.- References.- Appendix I: Fast-C(2D) Input- and Output-Files.- Input-File for FAST-C(2D).- Output-Files.

Journal ArticleDOI
TL;DR: In this paper, a complete numerical solution of the Navier-Stokes and energy equations, based on a modified SOLA-VOF method, was used to model droplet deformation and solidification and heat transfer in the substrate.

Journal ArticleDOI
TL;DR: In this paper, the effect of the injection and suction on heat transfer over a stretching surface with variable surface heat flux and uniform surface heat flow subject to injection was examined. And the boundary layer equations were transformed to ordinary differential equations, containing an injection parameter I, velocity exponent parameter M, heat flux exponent parameter and Prandtl number.
Abstract: Heat transfer over a stretching surface with variable surface heat flux and uniform surface heat flux subject to injection and suction is examined. The boundary layer equations are transformed to ordinary differential equations, containing an injection parameter I, velocity exponent parameter M, heat flux exponent parameter and Prandtl number . The effect of these parameters is studied. Suction increases the heat transfer from the surface, whereas injection causes a decrease in the heat transfer.

Journal ArticleDOI
TL;DR: In this article, the authors used a simple one-dimensional mixed layer model that is stochastically forced by the day-to-day changes in the local air-sea fluxes.
Abstract: Extratropical sea surface temperature (SST) and surface turbulent heat flux monthly anomalies in the central and eastern part of the North Atlantic are considered for the period 1952‐92 on a 5 83 58 grid. In this region where the mean surface current is small, the SST anomalies are well simulated by a simple one-dimensional mixed layer model that is stochastically forced by the day-to-day changes in the local air‐sea fluxes. A statistical signature of the stochastic model is that the cross correlation between surface heat flux and SST anomalies changes sign between negative and positive lags when the heat flux feedback is negative. This is observed at each grid point of the domain for the turbulent heat flux, which thus contributes both to generating the midlatitude SST anomalies and to damping them, once they are generated. Using properties of the lag covariance between SST and heat flux anomalies, the turbulent heat flux feedback is estimated from the observations. It averages to about 20 W m22 K21 in the investigated domain, increasing toward the northwest and the northeast and decreasing southward. It also varies seasonally, being generally largest in the fall and smaller and more uniform in summer. There is no indication that it can become significantly positive. A negative turbulent heat flux feedback is also suggested by the lag relation between the dominant modes of SST and turbulent heat flux variability over the whole North Atlantic, and it is found that the spatial patterns of the associated SST and turbulent heat flux anomalies are remarkably similar whether the atmosphere leads or lags, with only a change of heat flux sign between lead and lag situations. This analysis provides some observational support for the use on short timescales of a restoring condition for SST in ocean-only simulations, but the coupling coefficient should be weaker than usually assumed and a function of latitude and season. The associated SST‐evaporation feedback has little effect on interannual surface salinity changes. It should be significant on longer timescales, but then the restoring temperature should be allowed to vary and nonlocal influences should be considered.

Journal ArticleDOI
TL;DR: In this paper, the problem of cooling a heated plate by an axisymmetric isothermal fully developed turbulent jet has been studied numerically, and the normal-velocity relaxation turbulence model (V2F) was used to predict local heat transfer coefficient.

Book
01 Mar 1998
TL;DR: In this article, the authors consider the stability of plane-parallel flows and their stability in the case of arbitrary vibrations of finite frequency. But they do not consider the second-order effects.
Abstract: Basic Equations: Mechanical "Quasi-equilibrium" and Its Stability. Plane-Parallel Flows and Their Stability. Non-linear Problems. Internal Heat Sources. Vibrations of Finite Frequencies. Thermovibrational Convection in the General Case of Arbitrary Vibrations. The Problem of Boundary Conditions. The Second-order Effects. Some Particular Problems. Index.

Journal ArticleDOI
M. Fiebig1
TL;DR: In this paper, a survey on triangular and rectangular protrusions from a heat transfer surface which generate mainly longitudinal vortex systems is given on boundary layer and channel flow, either by themselves, or in a single row transverse to the flow direction.
Abstract: Longitudinal vortices are more efficient for heat transfer enhancement than transverse vortices.A survey is given on triangular and rectangular protrusions from a heat transfer surface which generate mainly longitudinal vortex systems. Wings and winglets are considered in boundary layer and channel flow, either by themselves, or in a single row transverse to the flow direction, or in a two dimensional array. Local and global heat transfer are studied as a function of the major parameters. For channel flows also the pressure losses are given. Winglets are superior to wings, but winglet form is of minor importance. In laminar flow, heat transfer enhancement increases with Reynolds number. Heat transfer enhancement increases for constant winglet aspect ratio with angle of attack up to a maximum angle of attack. But it increases also up to limiting values with winglet height relative to transverse and streamwise winglet spacing and relative to channel height or boundary layer thickness. The nonlinear character of fluid mechanics does not allow simple predictions.

Journal ArticleDOI
TL;DR: In this paper, simple formulas (based on the latest experimental tabulated data) for 11 physical properties of liquid ordinary water substance at saturation state, including saturation pressure, density, volumetric thermal expansion coefficient, specific volume of saturated vapor, specific enthalpy, specific heal, latent heal of vaporization, thermal conductivity, dynamic viscosity, Prandtl number, and surface tension as a function of temperature are presented.
Abstract: In this communication, simple formulas (based on the latest experimental tabulated data) for 11 physical properties of liquid ordinary water substance at saturation state—saturation pressure, density, volumetric thermal expansion coefficient, specific volume of saturated vapor, specific enthalpy, specific heal, latent heal of vaporization, thermal conductivity, dynamic viscosity, Prandtl number, and surface tension as a function of temperature (from 0 to 150°C)—which are used in heat transfer calculations for heat exchangers in heating systems and also for many other technological applications, are presented. Also, the uncertainties of these formulas are given. In most practical cases the pressure of liquid water is within the range from 1 to 10 absolute bar, which makes it possible to neglect the effect of pressure. All properties of saturated liquid water calculated with the recommended formulas are tabulated with a temperature increment of 5°.