Showing papers on "Heat transfer coefficient published in 1976"
01 Jan 1976
3,788 citations
TL;DR: In this paper, an experimental and theoretical-numerical investigation has been carried out to extend existing knowledge of velocity and temperature distributions and local heat-transfer coefficients for naturel convection within a horizontal annulus.
Abstract: An experimental and theoretical-numerical investigation has been carried out to extend existing knowledge of velocity and temperature distributions and local heat-transfer coefficients for naturel convection within a horizontal annulus. A Mach—Zehnder interferometer was used to determine temperature distributions and local heat-transfer coefficients experimentally. Results were obtained using water and air at atmospheric pressure with a ratio of gap width to inner-cylinder diameter of 0·8. The Rayleigh number based on the gap width varied from 2·11 × 104to 9·76 × 105. A finite-difference method was used to solve the governing constant-property equations numerically. The Rayleigh number was changed from 102 to 105 with the influence of Prandtl number and diameter ratio obtained near a Rayleigh number of 104. Comparisons between the present experimental and numerical results under similar conditions show good agreement.
716 citations
TL;DR: The average evaporation heat-transfer coefficient for the interline region of an adsorption controlled wetting film in which the disjoining pressure is approximated by P d =− A δ −3 can be represented bykh=hid[1−O5(η−1+η −2)]hid is the ideal liquid-vapor interfacial heat transfer coefficient and η is a function of the physical properties of the system.
424 citations
212 citations
TL;DR: In this article, the sensible heat and moisture fluxes by the bulk aerodynamic formulas were determined from a compilation of existing data, together with some new results, and the least square error fits were performed on the data.
Abstract: The parameterizations of the sensible heat and moisture fluxes by the bulk aerodynamic formulas are determined from a compilation of existing data, together with some new results. The data set comprised 152 determinations of the sensible heat flux and 30 of the moisture flux from experiments in which the fluxes were measured directly over water with suitable turbulence instrumentation. Least-square-error fits were performed on the data. The moisture flux (and therefore the latent heat flux) is adequately described by the bulk formula with a coefficient of 1.32 × 10−3. The parameterization of the sensible heat flux is complicated, for the data show 1) a small positive heat flux for zero temperature difference between the air and sea surface, 2) the coefficient for stable conditions is smaller than for unstable conditions, and 3) the coefficient appears to increase at high wind speeds, as shown by the data of Smith and Banke (1975). Separate bulk formulas are presented for the sensible heat flux fo...
187 citations
TL;DR: In this paper, an experiment was conducted to estimate body resistance (rb, plumage plus tissues) as a function of external temperature and wind speed, and the value ofrb decreased with wind speed and decreased as air temperature approached 0°C.
Abstract: Equations are derived that quantify the component thermal resistances to heat transfer in small birds and account explicity for the effects of variation in these resistances. Heat transfer theory is used to quantify external resistances, and an experiment was conducted to estimate body resistance (rb, plumage plus tissues) as a function of external temperature and wind speed. The value ofrb decreased with wind speed, and decreased as air temperature approached 0°C. Heat transfer from small birds is shown to be relatively independent of external resistances and mainly dependent onrb. The predictions of the new theoretical equations are shown to agree well with existing empirical data.
146 citations
TL;DR: In this article, the authors proposed a simple model to predict maximum and minimum temperature increases on the surfaces of sunlit fruits based on an energy balance at the surface of spherical fruits, and good agreement was found between the simple model and an infinite series analytical model of the system.
145 citations
TL;DR: In this paper, the average and local heat transfer from isothermal plates facing upwards in air in the range of Gr·Pr from 2 × 10 5 m to 10 9 m was determined.
143 citations
TL;DR: In this paper, a study of natural convection from an isothermal finite plate immersed in a stable thermally stratified fluid is presented, and an analytical solution to the problem is obtained by using the local nonsimilarity method.
Abstract: Results are presented of a study of natural convection from an isothermal finite plate immersed in a stable thermally stratified fluid. An analytical solution to the problem is obtained by using the local nonsimilarity method. Theoretical local and overall heat transfer coefficients are given for Pr = 0.7 and 6.0. Velocity and temperature profiles are given for Pr = 6.0. The actual experimental configuration was a vertical copper cylinder enclosed in a cube with rigid walls. Heat transfer data are correlated with the measured ambient thermal gradient. Visual studies of the flow field are also discussed. Excellent agreement is achieved between analysis and experiment.
110 citations
TL;DR: In this article, a thermohaline diffusive interface between convecting layers, with heat fluxes more similar to natural ones than in previous studies, was investigated and a new formula for the dependence of heat flux on interface stability was proposed.
TL;DR: In this article, transient, laminar free convection along a vertical, isothermal flat plate arising from buoyancy forces created by both temperature and concentration gradients is investigated.
TL;DR: In this article, a theory of heatconducting micromorphic continua is applied to an analysis of heat conduction in materials with inner structure, and the constitutive coefficients are specified as functions of the volume concentration of inner structure and thermal properties of materials.
TL;DR: In this paper, the authors investigated the convective heat transfer in fluid-saturated porous beds either heated from below or heated by distributed sources for several bed thicknesses and permeabilities.
Abstract: The convective heat transfer in fluid-saturated porous beds either heated from below or heated by distributed sources is investigated for several bed thicknesses and permeabilities. For the case of heating from below, Rayleigh numbers range from about 10 to 10,000. For distributed heat sources, Rayleigh numbers range from about 10 to 1,000. Critical Rayleigh numbers for the onset of convection are estimated as 38 for heating from below and 31.8 for distributed heat sources. Heat transfer results for convection induced by heating from below are in good agreement with analytical upper bound estimates obtained by Gupta and Joseph. (12 refs.)
TL;DR: In this paper, an apparatus for the measurement of the thermal conductivity of non-conducting liquids under their saturation vapour pressure is described, which is based upon the transient hot wire principle.
Abstract: The paper describes an apparatus for the measurement of the thermal conductivity of non-conducting liquids under their saturation vapour pressure. The instrument, which is based upon the transient hot wire principle, has been designed so that the measuring element conforms as closely as possible to an infinite line source of heat in an infinite fluid. Under these conditions the thermal conductivity of the liquid can be determined from the slope of a plot of the temperature rise of the heating element against the logarithm of time. The measurement system has been arranged so as to provide as many as 60 points on this plot for any particular thermodynamic state of the fluid under investigation. The reproducibility of the instrument is of the order of 0.03% and the precision of the measurements is estimated as +or-0.1%. Owing to a lack of a suitable theory for the effects of radiative heat transfer, the accuracy of the thermal conductivity values cannot be defined unequivocally, but a reasoned upper bound is +or-0.3%. Preliminary results are presented for n-heptane at three temperatures in the range 20 to 30 degrees C.
TL;DR: In this paper, the steady state heat transfer in an axisymmetric stagnation flow on an infinite circular cylinder is analyzed and boundary layer solutions are given for constant wall temperature and constant wall heat flux boundary conditions.
Abstract: An analysis is presented for the steady state heat transfer in an axisymmetric stagnation flow on an infinite circular cylinder. Boundary layer solutions are given for constant wall temperature and constant wall heat flux boundary conditions. Numerical results for the temperature distribution and solutions for the wall values of the temperature function have been tabulated. The range of Prandtl numbers considered was from 0.01 to 1000 while the Reynolds number was varied from 0.01 to 100.
TL;DR: In this paper, the authors studied the heating of carbohydrates in an industrial scale horizontal drum with a diameter of 0.6 m. Strips were mounted on the inside wall and the drum was heated externally by steam.
TL;DR: In this paper, the authors considered the application of regular parameter perturbation technique to obtain approximate solutions of heat-transfer problems with temperature-dependent thermal properties, and compared the accuracy with corresponding numerical solutions, the accuracy was found to be good.
TL;DR: In this paper, a population balance model is used to derive the drop size distribution of small drops which grow mainly by direct condensation, which is combined with the well-known size distribution for large drops which grows mainly by coalescence and with the growth rate of single drops to compute the heat flux during the process of dropwise condensation.
TL;DR: In this paper, it was shown that the magnitude of the heat and moisture flux depends on the cross-correlation coefficient of the temperature and humidity fluctuations, and that the coefficient of eddy conductivity may be significantly different from the correlation coefficient of moisture eddy diffusivity.
Abstract: Using simple models for the form of the pressure strain terms in the heat and moisture flux transport equations, it is shown that the magnitude of the heat and moisture flux depends on the cross-correlation coefficient of the temperature and humidity fluctuations. When the temperature and humidity fluctuations are weakly correlated it is shown that the coefficient of eddy conductivity may be significantly different from the coefficient of moisture eddy diffusivity.
TL;DR: In this article, the magnetohydrodynamic free convection flow of an electrically conducting fluid past a semi-infinite plate in a strong cross-field has been examined, and a full numerical solution was obtained providing details of skin friction and heat transfer at all stations along the plate.
Abstract: The magnetohydrodynamic free convection flow of an electrically conducting fluid past a semi-infinite plate in a strong cross-field has been examined. Formulation in terms of a characteristic length has enabled a full numerical solution to be obtained providing details of skin friction and heat transfer at all stations along the plate. An estimate of an indeterminacy in asymptotic solutions allows favourable comparison to be made between series solutions estimates of these quantities and their exact numerical values.
TL;DR: In this paper, a turbulent boundary layer developing on a smooth heated uniform-temperature plate in a zero pressure gradient was set up, and the origins of the layers were matched to remove the effect of an In heated starting length.
Abstract: A turbulent boundary layer developing on a smooth heated uniform-temperature plate in a zero pressure gradient was set up. The origins of the layers were matched to remove the effect of an In heated starting length. Similarity proposals were tested. The mean flow field followed the usual law of the wall and defect law for both temperature and velocity. Broad-band measurements of stream wise velocity and temperature fluctuations were made, and wall similarity and Townsend's self-preserving flow similarity were found to be applicable, at least after a sufficient flow development.Some initial attempts to arrive at a comparison between heat and momentum transport are presented. The results include conditionally sampled measurements of instantaneous heat and momentum fluxes and correlations between these two quantities. The fluxes were divided into quadrants. Conditional probabilities and weighted joint probability density functions were measured to determine whether there was a similarity in behaviour of these two fluxes. The concept of ‘hole size’ developed for momentum flux was extended to heat flux and events corresponding to bursts and sweeps in the momentum flux were found to be accompanied by corresponding events in the heat flux.
TL;DR: In this paper, a model was developed to calculate the heat transfer coefficients from the fuel rods to the steam-droplet mixture typical of Boiling Water Reactors under emergency core cooling system (ECCS) operation conditions during a postulated loss-of-coolant accident.
Abstract: A model has been developed to calculate the heat transfer coefficients from the fuel rods to the steam-droplet mixture typical of Boiling Water Reactors under Emergency Core Cooling System (ECCS) operation conditions during a postulated loss-of-coolant accident. The model includes the heat transfer by convection to the vapor, the radiation from the surfaces to both the water droplets and the vapor, and the effects of droplet evaporation. The combined convection and radiation heat transfer coefficient can be evaluated with respect to the characteristic droplet size. Calculations of the heat transfer coefficient based on the droplet sizes obtained from the existing literature are consistent with those determined empirically from the Full-Length-Emergency-Cooling-Heat-Transfer (FLECHT) program. The present model can also be used to assess the effects of geometrical distortions (or deviations from nominal dimensions) on the heat transfer to the cooling medium in a rod bundle.
TL;DR: In this article, a corresponding states procedure to predict the viscosity and thermal conductivity coefficients of a pure fluid or mixture is discussed, and it is shown that the conventional corresponding states approach is not sufficient to predict correctly the transport properties.