Outward Melting in a Cylindrical Annulus

1986 ◽  
Vol 108 (3) ◽  
pp. 240-245 ◽  
Author(s):  
C. J. Ho ◽  
K. C. Lin
Keyword(s):  
Numerical Simulation ◽  
Natural Convection ◽  
Melting Process ◽  
Two Dimensional ◽  
Melting Front ◽  
Cylindrical Annulus ◽  
Solid Region ◽  
Finite Difference Solution ◽  
Rayleigh Numbers ◽  
Change Material

A two-dimensional numerical simulation of outward melting process of a phase change material, n-octadecane, contained in a horizontal cylindrical annulus has been performed with a finite-difference solution of the governing partial differential equations of the system. Both conduction in the unmelted solid and natural convection induced in the melt have been taken into account. Results have been obtained for Rayleigh numbers up to Ra = 2.4 × 105 and the radius ratio of the annulus in a range of 1.6–3.0. The simulations are examined in the light of the effects of both the natural convection in the melt region and/or the subcooling in the solid region on the time-variation of the melting front during the process.

scholarly journals Natural convection melting of nano-enhanced phase change material in a cavity with finned copper profile

2018 ◽  
Vol 240 ◽  
pp. 01006 ◽  
Author(s):  
Nadezhda Bondareva ◽  
Mikhail Sheremet
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Melting Process ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Dimensional Approximation ◽  
Change Material

Present study is devoted to numerical simulation of heat and mass transfer inside a cooper profile filled with paraffin enhanced with Al2O3 nanoparticles. This profile is heated by the heat-generating element of constant volumetric heat flux. Two-dimensional approximation of melting process is described by the Navier-Stokes equations in non-dimensional variables such as stream function, vorticity and temperature. The enthalpy formulation has been used for description of the heat transfer. The influence of volume fraction of nanoparticles and intensity of heat generation on melting process and natural convection in liquid phase has been studied.

Free Two-Dimensional Convective Bifurcation in a Horizontal Annulus

1992 ◽  
Vol 114 (1) ◽  
pp. 99-106 ◽  
Author(s):  
A. Cheddadi ◽  
J. P. Caltagirone ◽  
A. Mojtabi ◽  
K. Vafai
Keyword(s):  
Natural Convection ◽  
Initial Conditions ◽  
Laser Doppler Anemometry ◽  
Perturbation Solution ◽  
Two Dimensional ◽  
Governing Equations ◽  
Cylindrical Annulus ◽  
Numerical Predictions ◽  
Rayleigh Numbers ◽  
Good Agreement

Natural convection is investigated numerically and experimentally in a cylindrical annulus. The governing equations based on primitive variables are solved using Chorin’s method. In addition to the unicellular flows reported in the literature, depending on initial conditions, bicellular flows are observed for high Rayleigh numbers. The bifurcation point is determined numerically. The velocity field for unicellular flows is measured by laser-Doppler anemometry in an air-filled annulus. A perturbation solution is also presented. The experimental results are in good agreement with numerical predictions and the perturbation solution.

Numerical Simulation of Natural Convection Flow in a Cube With a Horizontal Heated Strip

2008 ◽  
Author(s):  
Esam M. Alawadhi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Nusselt Number ◽  
High Temperature ◽  
Natural Convection ◽  
Vertical Wall ◽  
Convection Flow ◽  
Front Wall ◽  
Natural Convection Flow ◽  
Rayleigh Numbers

Natural convection flow in a cube with a heated strip is solved numerically. The heated strip is attached horizontally to the front wall and maintained at high temperature, while the entire opposite wall is maintained at low temperature. The heated strip simulates an array of electronic chips The Rayleigh numbers of 104, 105, and 106 are considered in the analysis and the heated strip is horizontally attached to the wall. The results indicate that the heat transfer strongly depends on the position of the heated strip. The maximum Nusselt number can be achieved if the heater is placed at the lower half of the vertical wall. Increasing the Rayleigh number significantly promotes heat transfer in the enclosure. Flow streamlines and temperature contours are presented, and the results are validated against published works.

Natural Convection in a Micro Size Horizontal Cylindrical Annulus With Periodic Volumetric Heat Flux

2009 ◽  
Author(s):  
Kamyar Mansour
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Viscous Fluid ◽  
Two Dimensional ◽  
Dimensional Problem ◽  
Similarity Parameter ◽  
Symbolic Calculation ◽  
Cylindrical Annulus ◽  
Gap Ratio

We consider the two-dimensional problem of steady natural convection in a narrow (Micro size) Horizontal Cylindrical annulus filled with viscous fluid and periodic volumetric heat flux. The solution is expanded in powers of a single combined similarity parameter, which is the product of the Gap ratio to the power of four, and Rayleigh number and the series extended by means of symbolic calculation up to 16 terms. Analysis of these expansions allows the exact computation for arbitrarily accuracy up to 50000 figures. Although the range of the radius of convergence is almost zero but Pade approximation lead our result to be good even for much higher value of the similarity parameter.

Numerical Simulation of Phase Change Thermal Storage in Finned Double-Pipe Heat Exchanger

2012 ◽  
Vol 232 ◽  
pp. 742-746 ◽  
Author(s):  
H. Shokouhmand ◽  
B. Kamkari
Keyword(s):  
Numerical Simulation ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Investigations ◽  
Double Pipe ◽  
Change Material ◽  
Pipe Heat ◽  
Bare Tube

This paper presents numerical investigations on melting of phase change material using paraffin wax inside a double pipe heat exchanger. Numerical simulations are performed for melting of phase change material (PCM) in annulus while the inner pipe has two or four longitudinal fins and the results compared with inner bare tube. The aim of this study is to understand the PCM melting behaviors by observing the natural convection currents movement and melting fronts formation. It is concluded that melting performance of PCM can be significantly improved by applying longitudinal fins on the inner tube.

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