Heat Transfer From an Oscillating Horizontal Wire

1971 ◽  
Vol 93 (2) ◽  
pp. 239-240 ◽  
Author(s):  
B. F. Armaly ◽  
D. H. Madsen
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Path Length ◽  
Experimental Results ◽  
Thin Wire ◽  
Reciprocating Motion ◽  
Total Path Length ◽  
The Wire ◽  
Horizontal Wire

The effect of vibration on heat transfer by natural convection has been investigated experimentally using a thin wire, 0.010 in. in diameter, and air as a convection medium. Horizontal reciprocating motion of varying amplitudes, peak-to-peak values of 0–2.655 in., and frequencies, 0–20 cps, was applied to an electrically heated horizontal wire. The average wire velocity (frequency times total path length traveled per cycle by the wire) was used to correlate and predict the experimental results.

Numerical Simulation of Thermal Performance of a High Aspect Ratio Thermal Energy Storage Device

2012 ◽  
Author(s):  
Jingde Zhao ◽  
Jorge L. Alvarado ◽  
Ehsan M. Languri ◽  
Chao Wang
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Energy Storage ◽  
Aspect Ratio ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
High Aspect Ratio ◽  
Numerical Study ◽  
Experimental Results ◽  
Heat Transfer Analysis

Heat transfer analysis of a high aspect ratio thermal energy storage (TES) device was carried out numerically. The three dimensional numerical study was performed to understand the heat transfer enhancement which results from internal natural convection in a high aspect ratio vertical unit. Octadecane was used as phase change material (PCM) inside TES system, which consisted of six corrugated panels filled with PCM. Each panel had a total of 6 tall cavities filled with PCM, which were exposed to external flow in a concentric TES system. Unlike traditional concentric-type TES devices where heat transfer by conduction is the dominant heat transport mechanism, the high aspect ratio TES configuration used in the study helped promote density-gradient based internal convection mechanism. The numerical model was solved based on the finite volume method, which captured the whole transient heat transfer process effectively. The time-dependent temperature profiles of the PCM inside a single TES panel are compared with the experimental results for two cases. Numerical and experimental results of the two cases showed a reasonable agreement. Furthermore, convection cells were formed and sustained when the PCM melted within the space between the solid core and the walls. The promising results of this numerical study illustrate the importance of internal natural convection on the speed of the PCM melting (charging) process.

Numerical and Experimental Studies of Fluid Flow and Heat Transfer in a Model Experiment for Hydrothermal Growth

2016 ◽  
Vol 254 ◽  
pp. 237-242
Author(s):  
Daniel Ursu ◽  
Radu Negrila ◽  
Alexandra Popescu ◽  
Ioan Grozescu ◽  
Daniel Vizman
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Temperature Difference ◽  
Experimental Studies ◽  
Experimental Results ◽  
Convection Flow ◽  
Bottom Part ◽  
Flow And Heat Transfer ◽  
Liquid Flows

Understanding of the natural convection flow in hydrothermal autoclaves is essential for the control of the growth rate and the quality of the grown crystals. This paper presents an analysis of the natural convection fluid flow and heat transfer and show the comparison between simulation and experimental results for the experimental model in a small size autoclaves, fill with water. A numerical model based on finite volume method has been developed to simulate the heat transfer and fluid convection in the vessel. Results show that the flow will strongly affect the temperature distribution. It can be observed that in the upper region the liquid flows up in the middle of the vessel and flows down in lateral parts near the walls. The temperature difference between experimental and simulation results is less than 1 °C in the upper part and between 2 and 3 °C in the bottom part. Velocity measurements show a good qualitative agreement between simulation and experimental results. The value of the z-component of velocity along the symmetry axis slightly increase with the increases of temperature difference ΔT .

Direct Numerical Simulation of Rotating Cavity Flows Using a Spectral Element-Fourier Method

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Diogo B. Pitz ◽  
John W. Chew ◽  
Olaf Marxen ◽  
Nicholas J. Hills
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Fourier Method ◽  
Spectral Element ◽  
Two Dimensions ◽  
High Order ◽  
Experimental Results ◽  
Element Approximation ◽  
Stable Algorithm ◽  
Element Discretization

A high-order numerical method is employed to investigate flow in a rotor/stator cavity without heat transfer and buoyant flow in a rotor/rotor cavity. The numerical tool used employs a spectral element discretization in two dimensions and a Fourier expansion in the remaining direction, which is periodic and corresponds to the azimuthal coordinate in cylindrical coordinates. The spectral element approximation uses a Galerkin method to discretize the governing equations, but employs high-order polynomials within each element to obtain spectral accuracy. A second-order, semi-implicit, stiffly stable algorithm is used for the time discretization. Numerical results obtained for the rotor/stator cavity compare favorably with experimental results for Reynolds numbers up to Re1 = 106 in terms of velocities and Reynolds stresses. The buoyancy-driven flow is simulated using the Boussinesq approximation. Predictions are compared with previous computational and experimental results. Analysis of the present results shows close correspondence to natural convection in a gravitational field and consistency with experimentally observed flow structures in a water-filled rotating annulus. Predicted mean heat transfer levels are higher than the available measurements for an air-filled rotating annulus, but in agreement with correlations for natural convection under gravity.

An experimental and analytical study of natural convection with appreciable thermal radiation effects

1972 ◽  
Vol 52 (1) ◽  
pp. 57-95 ◽  
Author(s):  
T. Audunson ◽  
B. Gebhart
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Natural Convection ◽  
Thermal Radiation ◽  
Convective Heat ◽  
Radiation Effects ◽  
Experimental Results ◽  
Fluid Medium ◽  
Temperature Distributions

An experimental and theoretical investigation has been carried out to determine the effect of thermal radiation on a natural convection boundary layer formed adjacent to a vertical flat surface with uniform heat flux input. In the experiment, the gases air, argon and ammonia were used as the fluid medium, thus permitting the observation of radiation effects in non-abosrbing and absorbing media. Experimental results were obtained for three different wall emittances at ambient pressures ranging from 2 to 8 atmospheres in air and argon and from 2 to 7 atmospheres in ammonia. An interferometer was used to measure the temperature distributions in the boundary layer and to evaluate the conductive (convective) heat flux from the surface into the fluid medium. The experimental temperature distributions and heat-transfer results obtained in ammonia gas are compared to the predictions of a perturbation analysis developed by the present writers. General agreement between theory and experiment is found. The presence of a radiating gas is seen to increase the convective heat transfer by as much as 40 % for the conditions of the present experiments. The results further indicate that the temperature distributions and wall-temperature gradients are strongly affected by both variations in the surface emittance and variations in gaseous emission and absorption. For non-absorbing gases, the experimental results are found to be in general agreement with existing theory. It is also shown that the experimental temperature distributions agree very well with theoretical predictions obtained by treating the convection and radiation processes as independent and superimposed.

Enhancement of Heat Transfer in Vertical Openended Channels in Natural Convection of Gas

2002 ◽  
Vol 33 (1-2) ◽  
pp. 5 ◽  
Author(s):  
Yu. F. Gortyshov ◽  
Igor A. Popov ◽  
V. V. Olimpiev ◽  
B. B. Kostylev
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Enhancement Of Heat Transfer
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