Showing papers on "Film temperature published in 1990"
TL;DR: In this paper, the free convection boundary layer flow with simultaneous heat and mass transfer in a porous medium is studied when the boundary wall moves in its own plane with suction, and asymptotic approximate solutions are obtained for the flow variables for various values of the activation energy.
Abstract: The free convection boundary layer flow with simultaneous heat and mass transfer in a porous medium is studied when the boundary wall moves in its own plane with suction. The study also incorporates chemical reaction for the very simple model of a binary reaction with Arrhenius activation energy. For large suction, asymptotic approximate solutions are obtained for the flow variables for various values of the activation energy.
262 citations
TL;DR: In this article, a general flow model that accounts for the effects of the impermeable boundary and inertia is used to describe the flow inside the porous region and the dependence of these characteristics on the governing parameters such as the Darcy number, the inertia parameter, the Prandtl number and the ratio of the conductivity of the porous material to that of the fluid is also documented.
Abstract: Convective flow and heat transfer through a composite porous/fluid system have been studied numerically. The composite medium consists of a fluid layer overlaying a porous substrate, which is attached to the surface of the plate. The numerical simulations focus primarily on flows that have the boundary layer characteristics. However, the boundary layer approximation was not used. A general flow model that accounts for the effects of the impermeable boundary and inertia is used to describe the flow inside the porous region. Several important characteristics of the flow and temperature fields in the composite layer are reported. The dependence of these characteristics on the governing parameters such as the Darcy number, the inertia parameter, the Prandtl number, and the ratio of the conductivity of the porous material to that of the fluid is also documented. The results of this investigation point out a number of interesting practical applications such as in frictional drag reduction, and heat transfer retardation or enhancement of an external boundary.
126 citations
TL;DR: In this paper, it was shown that for small values of the molecular Peclet number no resistance at the rigid wall exists, and that the effect of lateral maldistribution of fluid velocity and/or thermal conductivity, of axial dispersion of heat, and of small, systematic errors in measurement is investigated.
124 citations
TL;DR: In this article, the heat transfer from a stretching sheet to a micropolar fluid is analyzed using the theory of Eringen, and the governing equations for momentum, angular momentum and energy have been solved numerically.
Abstract: The heat transfer from a stretching sheet to a micropolar fluid is analyzed using the theory of micropolar fluids formulated by Eringen. The governing equations for momentum, angular momentum and energy have been solved numerically. Numerical data for the friction factor and Nusselt number has been tabulated for a range of Prandtl numbers. Surface mass transfer rate and the power law constant for the wall temperature have considerable influence on the heat transfer mechanism.
100 citations
01 Nov 1990
TL;DR: In this article, the effects of the induced magnetic field and sources or sinks have been included in the analysis of flow and heat transfer over a stretching sheet with a magnetic field in an electrically conducting ambient fluid.
Abstract: The flow and heat transfer over a stretching sheet with a magnetic field in an electrically conducting ambient fluid have been studied. The effects of the induced magnetic field and sources or sinks have been included in the analysis. Both non-isothermal wall and constant heat flux conditions have been considered. The governing equations have been solved numerically using a shooting method. It is observed that for the prescribed wall temperature the skin friction, induced magnetic field at the wall and heat transfer are enhanced due to the magnetic field, but in general, they reduce as the reciprocal of the magnetic Prandtl number increases. For constant heat flux case, the temperature at the wall reduces as the magnetic field increases, but it increases with the reciprocal of the magnetic Prandtl number. The heat transfer is strongly affected by the Prandtl number, wall temperature and sink. Whenm 2.5 the unrealistic temperature distributions are encountered. The present analysis is more general than any previous investigation.
83 citations
TL;DR: In this paper, a numerical analysis is carried out to investigate the effects of latent heat transfer, in association with the evaporation of a finite liquid film on the channel wall, on the natural convection heat and mass transfer.
79 citations
TL;DR: In this article, the authors investigated the structure of laminar wakes and heat transfer in the presence of thermal buoyancy art in a two-dimensional horizontal channel with a built-in square cylinder and showed that mixed convection can initiate periodicity and asymmetry in the wake at lower Reynolds numbers than forced convection alone.
Abstract: Structures of laminar wakes and heat transfer in the presence of thermal buoyancy art investigated from the numerical solution of complete Navier-Stokes and energy equations in a two-dimensional horizontal channel with a built-in square cylinder. Results show that mixed convection can initiate periodicity and asymmetry in the wake at lower Reynolds numbers than forced convection alone. For a given Reynolds number, the heating of the fluid in the channel is improved by mixed convection up to a certain Grashof number and deteriorates if the Grashof number is further increased.
75 citations
TL;DR: In this article, the authors measured the local forced convective heat transfer characteristics of an array of two-dimensional discrete heat sources and found that protruding heat sources yield higher heat transfer than flush-mounted heat sources at the same channel Reynolds number.
69 citations
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01 Jan 1990
TL;DR: In this article, the influence of longitudinal pressure gradient on limiting laws of friction, heat and mass transfer on turbulent boundary layer of gas on a permeable surface film cooling effectiveness extension of the limiting law of friction and heat transfer to gas-liquid flows.
Abstract: Thermal diffusion and boundary layers boundary layer with vanishing viscosity limiting relative laws of friction, heat and mass transfer with gas flow along a flat impermeable plate the influence of longitudinal pressure gradient on limiting laws of friction, heat and mass transfer turbulent boundary layer of gas on a permeable surface film cooling effectiveness extension of the limiting laws of friction and heat transfer to gas-liquid flows.
56 citations
TL;DR: In this article, analytical solutions for fully developed natural convection in open-ended vertical concentric annuli are presented and four fundamental boundary conditions have been investigated and corresponding fundamental solutions are obtained.
55 citations
TL;DR: In this article, the authors measured drag and heat transfer coefficients on heated spheres free-falling in saturated and subcooled water, and found that the drag decreases with the initial sphere temperature, T 0.
Abstract: Experiments have been conducted to measure drag (Cg) and heat transfer coefficients (h) and to study the boding nature on heated spheres free-falling in saturated and subcooled water. Simultaneous measurements of the transient sphere velocity and temperature during the fall enabled calculation of cD, heat fluxes and h values. It has been found that the drag decreases with the initial sphere temperature, T0. The measured results, as well as still and motion photography, show that at10⩾ 450° Cfilm boiling pre vaih, with low heat fluxes at the beginning of the transient. In some cases the film collapses, leading to a transition to disturbed-film and micro-bubble regimes, associated with larger heat fluxes and also solid-liquid interactions, with lateral motion of the sphere )“ shoot-off” )
TL;DR: In this paper, an experimental and numerical investigation was made of laminar natural convection flow of air in a vertical channel with a single obstruction, where optical techniques were used to obtain measurement of both quantitative data (heat fluxes and temperatures) and qualitative data (flow visualization).
TL;DR: In this article, the laminar-flow heat transfer to a fluid flowing axially between a triangular or a square array of cylinders with a uniform wall temperature was investigated, and the energy equation in finite-difference form was solved to obtain the axial variation of the cross-sectional temperature distribution.
TL;DR: In this article, the authors applied a rigorous thermal radiation and heat conduction analysis to a high T c film irradiated by an optical pulse and compared the predicted bolometric voltage response to experimental data.
TL;DR: In this article, the unsteady flow of a liquid film on a cold rotating disk is analyzed by means of matched asymptotic expansion under the assumptions of radially uniform film thickness that varies with time.
Abstract: The unsteady flow of a liquid film on a cold rotating disk is analysed by means of matched asymptotic expansion under the assumptions of radially uniform film thickness that varies with time. The velocity, the temperature and the rate of heat transfer are determined. It is shown how the uniform film thins with time for fixed values of the cooling or heat dissipating parameter β, and the Prandtl number σ. When either β increases or σ decreases, the film thickness increases, which implies that a relative resistance to film thinning is developed inside the film- A zone S, bounded by a curve in the r-z plane, may be delineated such that the temperature is minimum on this curve. Thus, heat flows from the disk to the fluid, inside the zone S, and in the opposite direction outside S.
TL;DR: In this article, the fluid flow and heat transfer characteristics are found to be dependent on a modified Grashof number Gr+, Prandtl number Pr, number of fins M and the relative fin height H. Satisfactory agreement is obtained between the present numerical results and previous experimental data.
TL;DR: In this paper, a cubic spline collocation numerical method was used to determine the conjugate heat transfer occuring in the laminar boundary layer on a continuous, moving plate.
TL;DR: In this paper, the effect of thermomagnetic convection, which arises when a temperature-sensitive magnetic fluid is heated in a vessel under a nonuniform magnetic field, is studied by a model experiment.
TL;DR: In this article, forced convection heat transfer from a vibrating sphere, a cylinder and a square-section tube to water was experimentally investigated and the obtained heat transfer data with the vibration effect is well correlated in terms of the energy dissipation calculated from the fluid drag acting on the vibrating bodies.
Abstract: The forced convection heat transfer from a vibrating sphere, a cylinder and a square-section tube to water was experimentally investigated. The obtained heat transfer data with the vibration effect is well correlated in terms of the energy dissipation calculated from the fluid drag acting on the vibrating bodies. Through the use of the energy dissipation, the heat transfer from vibrating bodies to a fluid flow can be discussed analogously with the mass transfer.
TL;DR: In this paper, the governing boundary layer equations along with the boundary conditions are first cast into a dimensionless form by a pseudo-similarity variable transformation and the resulting system of equations is then solved by a finite difference method in conjunction with the cubic spline interpolation.
TL;DR: In this paper, the authors dealt with natural convection heat transfer from a vertical plate embedded in a fluid saturated porous medium whose ambient temperature is not uniform and solved the problem by integral method of von-Karman type and the closed form solution was obtained.
Abstract: Present investigation deals with natural convection heat transfer from a vertical plate embedded in a fluid saturated porous medium whose ambient temperature is not uniform The problem is solved by integral method of von-Karman type and the closed form solution is obtained The effects of stratification parameter on local and overall heat transfer coefficients, velocity and temperature profiles are analysed
TL;DR: In this article, the authors investigated the conjugate unsteady heat transfer between a translating droplet and its surrounding fluid at moderate Reynolds number and found that by increasing the Reynolds number, the predicted rate of heat transfer is significantly increased for fluid spheres as a result of increased fluid motions both inside and outside the droplet.
TL;DR: In this article, the analysis of steady laminar forced convection boundary layer of power-law non-Newtonian fluids on a continuously moving cylinder with the surface maintained at a uniform temperature or uniform heat flux is presented.
TL;DR: In this article, the authors compared the wall functions of George and Capp and Cheesewright with numerical calculations for air, using a k-e turbulence model with low-Reynolds number modifications.
TL;DR: In this article, the authors studied the temperature profile of a linear stretching plate for large Prandtl numberP by an asymptotic approach, and evaluated the Nusselt number and the order of magnitude of PrandTL number for variable Nussselt numbers.
Abstract: In the present paper, we study the temperature profile in the case of a linear stretching plate for large Prandtl numberP by an asymptotic approach. Also, we evaluate the Nusselt number and the order of magnitude of Prandtl number for variable Nusselt numbers.
11 Jun 1990
TL;DR: In this paper, the influence of the characteristic dimensionless groups on the local heat transfer has been investigated, and the discrepancies found can be explained only, if in addition to the limitations of the analogy, the Influence of free convection is taken into account.
Abstract: The local heat transfer from a plane rotating disc enclosed in a casing has been studied experimentally. The disc of 800 mm diameter can be run up to 2000 min−1 at axial distances between disc and casing varied between 5 and 55 mm. Centrifugal or alternatively centripetal flow of cooling air at rates up to m = 1 kg/s can be applied, both with or without an inlet swirl.With the disc rotating in a closed casing (m = 0 kg/s) the influence of the characteristic dimensionless groups on the local heat transfer has been investigated. At a fixed radius, a variation of the local Reynolds Number by either speed or density results in corresponding changes of the heat transfer. However, with a variation of the radius different heat transfer-Re relations are found. In fact, the temperature distribution in the gas caused by the heat flux results in an additional influence of free convection, to be expressed by a Grashof Number. This is confirmed by a comparison of the experimental results with calculations based on Reynolds Analogy and measured friction coefficients. The discrepancies found can be explained only, if in addition to the limitations of the analogy, the influence of free convection is taken into account. Additional results of ongoing experiments concerning the influence of the geometry of the cavity between disc and casing, of the coolant flow rate and of the swirl are presented.Copyright © 1990 by ASME
TL;DR: In this paper, the authors investigated natural convection heat transfer between water and a mushroom-shaped particle, under transient conditions, with various initial temperature differences, and found that the average value of h was significantly higher for heating than for cooling.
Abstract: Natural convection heat transfer was investigated between water and a mushroom-shaped particle, under transient conditions, with various initial temperature differences. Convective heat transfer coefficients (h) were observed to decrease over time due to equilibration, resulting in reduced driving force. In all cases, the average value of h was significantly higher for heating than for cooling. In most cases, h increased significantly with increasing initial temperature difference. When results at the same initial temperature difference were compared, h was higher for the higher temperature ranges. Correlations were developed between Nusselt, Rayleigh, and Fourier numbers.
TL;DR: Magnetic fluids, produced using highly temperature-sensitive ultrafine ferrites coprecipitated in alkaline solution containing zinc and calcium ions, were used in the heat convection pipe as mentioned in this paper.
TL;DR: In this article, the authors studied free and mixed convection for horizontal porous layers heated from below by multiple, isothermal, discrete sources and obtained steady state results for natural convection with up to eight sources and mixed-convection with four sources.
Abstract: Free and mixed convection has been studied numerically for horizontal porous layers heated from below by multiple, isothermal, discrete sources. Steady-state results have been obtained for natural convection with up to eight sources and for mixed convection with up to four sources. Rayleigh numbers are varied from 10 to 500, and Peclet numbers from 0.1 to 100. For natural convection, the vertical sidewalls for the two-dimensional domain considered have little effect on Nusselt numbers if the distance between the outermost source and wall is greater than three times the length of the heat source. As the number of heat sources increases, heat-transfer coefficients for the second outermost sources are a minimum. In mixed convection, overall Nusselt numbers increase with both the number of sources and Rayleigh number. If the individual heat source is considered, heat-transfer coefficients are determined only by its location. For Rayleigh numbers greater than 50, there exists a critical Peclet number for which the overall Nusselt number is a minimum. Unstable, oscillatory flow and temperature fields are observed for Rayleigh numbers greater than 50. Nomenclature c = specific heat of fluid at constant pressure, J/kg-K D - length of the heat sources, m DN = nth discrete heat source d = distance between two discrete heat sources, m g = acceleration of gravity, m/s2 H = height of the porous layer, m h = local heat-transfer coefficient, W/m2-K h = average heat-transfer coefficient for the bottom sur
01 Nov 1990
TL;DR: In this paper, the analysis of heat transfer to non-Newtonian power-law fluid flow past a continuously moving flat porous plate in presence of suction/injection with heat flux has been presented.
Abstract: The analysis of heat transfer to the non-Newtonian power-law fluid flow past a continuously moving flat porous plate in presence of suction/injection with heat flux has been presented. We have obtained the solution using the method of successive approximations, starting with zero approximation. It has been observed that the results obtained forn=1 are in good agreement with the corresponding results for Newtonian fluid. For various values of flow indexn and the suction/injection parameter, temperature profiles and rate of heat transfer have been presented graphically. The effect of suction is to decrease in temperature and the rate of heat transfer, while reverse nature occurs for injection.