Showing papers on "Film temperature published in 1995"
TL;DR: In this paper, a finite difference scheme consisting of modified ADI (Alternating Direction Implicit) method and SLOR (Successive Line Over Relaxation) method is used to solve the vorticity-stream function formulation of the problem.
484 citations
TL;DR: In this article, similar solutions of the laminar boundary-layer equations describing heat and flow in a quiescent fluid driven by a stretched surface subject to suction or injection are obtained.
333 citations
TL;DR: In this paper, an experimental investigation on heat transfer behavior during forced convection condensation inside a horizontal tube for wavy, semi-annular and annular flows is presented.
Abstract: This paper presents the results of an experimental investigation on heat transfer behaviour during forced convection condensation inside a horizontal tube for wavy, semi-annular and annular flows. A qualitative study was made of the effect of various parameters - refrigerant mass flux, vapour quality, condensate film temperature drop and average vapour mass velocity - on average condensing heat transfer coefficient. Akers-Rosson correlations have been found to predict the heat transfer coefficients within ±25% for the entire range of data. A closer examination of the data revealed that the nature of the relation for the heat transfer coefficient changes from annular and semi-annular flow to wavy flow. Akers-Rosson correlations with changed constant and power have been recommended for the two flow regimes.
99 citations
TL;DR: In this paper, the authors present a numerical investigation of fully developed laminar convective heat transfer in a helicoidal pipe with a finite pitch coiled pipe, where three major parameters are identified to affect LHT: the Dean number, torsion and the Prandtl number.
82 citations
TL;DR: In this article, a numerical solution for laminar forced convection of an incompressible periodically reversing flow in a pipe of finite length at constant wall temperature is presented, where four parameters that govern the heat transfer characteristics for the problem under consideration are the kinetic Reynolds number Reω, the dimensionless oscillation amplitude Ao, the length to diameter ratio LID, and the Prandtl number of the fluid.
82 citations
TL;DR: In this article, a numerical heat transfer analysis was performed to investigate the surface temperature distribution and uniformity of heat flux in the cold plates, and the results demonstrate good agreement with experimental surface temperature measurements.
75 citations
TL;DR: In this article, fully analytical solutions for the temperature and mass fraction are obtained for a falling film absorber in an absorption heat pump, leading to an analytical expression for the local and total mass absorbed.
57 citations
TL;DR: In this article, a finite element method employing Galerkin's approach was developed to analyze free convection heat transfer in axisymmetric fluid saturated porous bodies, and the method was used to study the effect of aspect ratio and radius ratio on Nusselt number in the case of a proous cylindrical annulus.
Abstract: A finite element method employing Galerkin’s approach is developed to analyze free convection heat transfer in axisymmetric fluid saturated porous bodies. The method is used to study the effect of aspect ratio and radius ratio on Nusselt number in the case of a proous cylindrical annulus. Two cases of isothermal and convective boundary conditions are considered. The Nusselt number is always found to increase with radius ratio and Rayleigh number. It exhibits a maximum when the aspect ratio is around unity; maximum shifts towards lesser aspect ratios as Rayleigh number increases. Results are compared with those in the literature, wherever available, and the agreement is found to be good.
54 citations
TL;DR: In this article, a surface contribution analysis of energy and momentum balances in a unit cell of the offset fin geometry is performed to predict heat transfer and pressure drop performance of liquid-cooled offset fin cold plates.
50 citations
TL;DR: In this article, a superconducting tungsten thin film was used for phonon mediated particle detection on a silicon substrate, where the temperature of the film was held constant within the transition by an electrothermal feedback process, while the substrate temperature was well below the film temperature.
Abstract: We are developing and testing a new type of superconducting transition edge sensor for phonon mediated particle detection. This sensor consists of a superconducting tungsten thin film deposited on a silicon substrate. The temperature of the film is held constant within the superconducting transition (T/sub c//spl ap/70 mK) by an electrothermal feedback process, while the substrate temperature is well below the film temperature. Phonon energy deposited in the film is removed by a reduction in feedback Joule heating, which is measured using a series array of DC SQUIDs. The resulting signals show improvements in linearity and signal to noise ratio over our previous transition edge sensors. >
43 citations
Journal Article•
TL;DR: In this article, the authors report the results of numerical simulations and laboratory investigations carried out to explore the characteristics of the transient self-heating process and demonstrate that a characteristic temperature, defined as the crossing-point temperature, does not change (to within ± 0.01°C) for the same exothermicity, activation energy, thermal properties, half-thickness and boundary temperature when only the initial uniform temperature is varied.
TL;DR: In this paper, the effects of waves on a falling condensate film on heat transfer have been studied by direct computer simulation, and the authors attributed the enhancement of the heat transfer is attributed to the decreasing time averaged film thickness due to waves and the disturbance effects of the waves are small.
TL;DR: A numerical scheme based on Galerkin's finite element method was used to solve the three-dimensional governing equations for steady laminar simultaneously developing flow and heat transfer in a semi-circular duct as discussed by the authors.
TL;DR: In this paper, a theoretical investigation was carried out on the heat transfer characteristics of an oscillating flow in a circular pipe and the sinusoidal temperature distribution was considered, which revealed the existence of two important parameters and occurrence of three distinct regimes.
TL;DR: In this paper, a simple correlation is presented for calculating the wall-to-suspension heat transfer in circulating fluidized beds of low dimensionless pressure gradients with different solid particles like bronze, glass and polystyrene at ambient temperatures.
TL;DR: In this article, the effect of the buoyancy parameter on the reversed flow structure and the Nusselt number is discussed and discussed. But the results of the experiments were limited to a vertical convergent channel, where the ratio of the height to width at the inlet of the channel is 15.
TL;DR: In this article, the authors investigated the heat and mass transfer characteristics for a falling liquid film evaporating into a gas stream and found that the latent heat transport connected with the vaporization of the liquid film plays an important role in the transfer processes.
TL;DR: In this article, a steady laminar axisymmetric thermal flow past solitary oblate spheroids and non-spherical droplets at constant temperature has been numerically analyzed.
TL;DR: In this paper, a sinusoidal axial distribution of wall heat flux is studied under the hypothesis that both axial heat conduction and viscous dissipation in the fluid are negligible.
Abstract: Stationary and laminar forced convection in a circular tube with a sinusoidal axial distribution of wall heat flux is studied under the hypothesis that both axial heat conduction and viscous dissipation in the fluid are negligible. Two cases are considered: a sinusoidal wall heat flux distribution with a vanishing mean value; a sinusoidal wall heat flux distribution which does not change its sign. In both cases, the temperature field and the local Nusselt number are evaluated analytically in the fully developed region, i.e. where the local Nusselt number depends periodically on the axial coordinate. It is shown that, in the first case, the fully developed region presents an infinite sequence of axial positions where the local Nusselt number is singular. In these positions, the wall heat flux has a non-vanishing value even if the wall temperature equals the bulk temperature.
TL;DR: In this article, an iterative method for the solution of the conjugate heat transfer problem is presented, where convection heat transfer in a channel is solved using an FDM, and conduction heat transfer on the channel wall is solved by a BEM.
Abstract: An iterative method for the solution of the conjugate heat transfer problem is presented. Convection heat transfer in a channel is solved using an FDM, and conduction heat transfer in the channel wall is solved using a BEM. The FDM and BEM are coupled to iteratively solve the conjugate problem. Numerical results are in good agreement with experimental data. The influences of the conductivity ratio of solid on fluid, solid wall thickness, channel aspect ratio, and of the input velocity on the interfacial temperature and Nusselt number distribution are studied.
TL;DR: In this article, an equation for heat transfer for the boundary condition of constant heat flux at the wall for laminar developed flow in ducts of arbitrary cross-sectional area is given.
Abstract: We can calculate the heat transfer in ducts of arbitrary cross section with the definition of the equivalent diameter only in turbulent flow. In laminar flow, it is not sufficient to define an equivalent diameter, because the boundary layer of each wall is influenced by another wall. Therefore, one needs additional quantities to describe the heat transfer and pressure drop. This is shown for pressure drop calculations by Yilmaz and heat transfer for constant wall temperature by Yilmaz and Cihan. In these works, by using other quantities, it was possible to obtain general equations for pressure drop and heat transfer for constant wall temperature. In the present work, an equation for heat transfer for the boundary condition of constant heat flux at the wall for laminar developed flow in ducts of arbitrary cross-sectional area is given. 14 refs., 1 fig., 4 tabs.
TL;DR: In this paper, a two dimensional laminar mixed convection flow in vertical channels with a discrete heat source was numerically analyzed and the governing equations were solved using a finite difference method based on the control volume approach.
Abstract: Two dimensional laminar mixed convection flow in vertical channels with a discrete heat source was numerically analyzed. An isoflux discrete heating element was located on the left wall, while the isothermal conditions were imposed on the other wall. The governing equations were solved using a finite difference method based on the control volume approach. The mean Nusselt number was calculated and the maximum component temperature was determined. The computations were carried out for different Grashof number, Reynolds number, heater locations and the channel width. It was observed that the location of the heating element does not play a considerable role on the flow. At low Reynolds numbers (Re 1). However, at high Reynolds numbers more effective cooling is obtained in narrow channels.
TL;DR: In this article, a study of quasi-steady state natural convection in a vertical annular porous layer when the inner wall is heated by a constant heat flux and the other walls are maintained adiabatic is made.
Abstract: A study is made of quasi-steady state natural convection in a vertical annular porous layer when the inner wall is heated by a constant heat flux and the other walls are maintained adiabatic. On the basis of the Darcy-Oberbeck-Boussinesq equations, the problem is solved analytically in the limil of a long shallow annulus (A ≫ 1), where A is the aspect (height-to-gap width) ratio. The analytical solution for the Row and heat transfer, based on a parallel flow assumption, is derived in terms of the Darcy-Rayleigh number R and radius ratio K. A numerical study of the same phenomenon, obtained by solving the complete system of governing equations, is conducted to assess the validity of the analytical results. It is demonstrated that the analytical solution predicts well the flow structure and the heat transfer for a wide range of R and K. In the boundary layer regime it is shown that the Nusselt number, based on the gap width of porous annulus, is Nu=R 2/5[2K 2lnK−(K 2 − 1)]/[2(K − 1)2(K + 1)6/5].
TL;DR: In this paper, the conjugate heat transfer problem with Poiseuille-Couette flow within a thick-waited parallel-plate channel is solved using a coupled finite-difference method / boundary-element method (FDM/BEM) iteration scheme.
Abstract: The conjugate heat transfer problem with Poiseuille-Couette flow within a thick-waited parallel-plate channel is solved using a coupled finite-difference method / boundary-element method (FDM/BEM) iteration scheme. The convective heat transfer in the fluid is solved using the FDM, and the conduction heat transfer in the solid is solved using the BEM. The two solutions are coupled to solve the conjugate problem iteratively by enforcing continuity of temperature and heat flux at the fluid-solid interfaces. Numerical results are in good agreement with available experimental data. A parametric study was performed to determine the influence of conductivity ratio of solid to fluid, dimensionless solid wall thickness, channel aspect ratio, and the ratio of free surface velocity to mean fluid velocity on the interfacial temperature and Nusselt number distributions
01 May 1995
TL;DR: In this paper, the authors investigated the effect of conduction on the heat transfer characteristics of the natural convection boundary layer of the fluid and introduced a wall conduction parameter, p, which is a measure of the heat conductivities of the solid and fluid and the thickness of the cylindrical shell.
Abstract: An analysis is made of the laminar natural convection of incompressible fluids over a slender, hollow circular cylinder with the inner surface at a constant temperature ofTb. The temperature of the outer surface must be solved from the coupled conduction of the cylinder and the natural convection of the fluid over the cylinder. The objective of this paper is to investigate the effect of conduction on the heat transfer characteristics of the natural convection boundary layer of the fluid. A wall conduction parameter,p, is introduced which is a measure of the heat conductivities of the solid and the fluid and the thickness of the cylindrical shell. The governing differential equations, being non-similar, are solved by a finite-difference method. Numerical results are generated for a series of values ofp's and Prandtl numbers.
01 Jan 1995
TL;DR: In this paper, the boundary layer on a 5 deg half-angle cone is studied by measurement of the heat flux distribution and by qualitative flow visualisation in the laminar layer, heat flux levels are higher in air than in nitrogen because of a larger heat release from oxygen recombination at the wall.
Abstract: The boundary layer on a 5 deg half-angle cone is studied by measurement of the heat flux distribution and by qualitative flow visualisation In the laminar layer, heat flux levels are higher in air than in nitrogen because of a larger heat release from oxygen recombination at the wall By varying the specific reservoir enthalpy in air and N2, and from measurements in CO2, it is found that real-gas effects stabilize the boundary layer
31 Dec 1995
TL;DR: In this article, a correlation between the numerical solutions of the Prandtl numbers and the average Nusselt numbers for a wide range of Rayleigh numbers was presented. But the correlation was only applied to single horizontal cylinders with uniform surface heat fluxes.
Abstract: The natural convection heat transfer coefficients on single horizontal cylinders with uniform surface heat fluxes were derived numerically from the fundamental equations for laminar natural convection heat transfer by finite difference method without the boundary layer approximation for a wide range of Rayleigh numbers for the Prandtl numbers ranging from 0.005 to 3000. Based on the numerical solutions for the Prandtl numbers, a correlation which describes the numerical solutions of the average Nusselt numbers for the investigated Prandtl numbers within {+-}5 percent is presented. The average Nusselt numbers calculated from the correlation are compared with the experimental results for various fluids with the Prandtl numbers ranging from 0.005 to about 18000 obtained by the authors and by other workers: the authors` experimental results for various liquids such as water, ethanol, glycerin, liquid sodium, liquid nitrogen and liquid helium obtained under a wide range of bulk liquid temperatures and system pressures with a variety of cylinder diameters agree with the correlation within {+-}20 percent differences when the fluid properties are evaluated at the reference temperature.
TL;DR: In this paper, a numerical analysis of the laminar forced convection in a cylindrical duct for a thermodependent Herschel-Bulkley fluid is presented, where two boundary conditions are considered: constant wall heat flux and constant wall temperature.
TL;DR: In this paper, an analytical solution to the forced convective heat and mass transfer across a laminar incompressible boundary layer, over the surface of a stationary isothermal spherical particle was obtained.