scholarly journals Convective Heat Transfer During Melting in a Solar LHTES

2021 ◽  
Vol 11 (3) ◽  
pp. 7181-7186
Author(s):  
F. Z. Mecieb ◽  
F. García Bermejo ◽  
J. P. Solano Fernández ◽  
S. Laouedj
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Melting Rate ◽  
Melting Time ◽  
Heat Sources ◽  
Stored Energy ◽  
Numerical Investigations ◽  
Coupling Strategy ◽  
Kinetics Of ◽  
Change Material

Melting combined with natural convection in a shell and Latent Thermal Energy Storage (LHTES) tube driven by a solar collector was analyzed numerically in the present work. This work's particularity lies in the fact that the HTF temperature varies at each moment following the solar irradiance curve. A program (UDF) has been developed and integrated into Ansys to meet this requirement. The use of this coupling strategy allows obtaining realistic unsteady LHTES results. Several numerical investigations were carried out to analyze the effect of the heat sources' power on the accumulator's performance. The obtained results show that natural convection considerably influences the heat transfer as well as the melting kinetics of the Phase Change Material (PCM). Besides, the results show that increasing the heat transfer fluid's thermal load can increase the melting rate of the PCM and the stored energy and reduce the entire melting time.

scholarly journals Numerical Simulation of the Impact of the Heat Source Position on Melting of a Nano-Enhanced Phase Change Material

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1425
Author(s):  
Tarek Bouzennada ◽  
Farid Mechighel ◽  
Kaouther Ghachem ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Melting Rate ◽  
Heat Transfer Fluid ◽  
Commercial Code ◽  
Tube Position ◽  
The Impact ◽  
Change Material

A 2D-symmetric numerical study of a new design of Nano-Enhanced Phase change material (NEPCM)-filled enclosure is presented in this paper. The enclosure is equipped with an inner tube allowing the circulation of the heat transfer fluid (HTF); n-Octadecane is chosen as phase change material (PCM). Comsol-Multiphysics commercial code was used to solve the governing equations. This study has been performed to examine the heat distribution and melting rate under the influence of the inner-tube position and the concentration of the nanoparticles dispersed in the PCM. The inner tube was located at three different vertical positions and the nanoparticle concentration was varied from 0 to 0.06. The results revealed that both heat transfer/melting rates are improved when the inner tube is located at the bottom region of the enclosure and by increasing the concentration of the nanoparticles. The addition of the nanoparticles enhances the heat transfer due to the considerable increase in conductivity. On the other hand, by placing the tube in the bottom area of the enclosure, the liquid PCM gets a wider space, allowing the intensification of the natural convection.

scholarly journals Latent Heat Thermal Storage of Nano-Enhanced Phase Change Material Filled by Copper Foam with Linear Porosity Variation in Vertical Direction

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1508
Author(s):  
Mohammad Ghalambaz ◽  
Mohammad Shahabadi ◽  
S. A. M Mehryan ◽  
Mikhail Sheremet ◽  
Obai Younis ◽  
...  
Keyword(s):  
Natural Convection ◽  
Phase Change ◽  
Phase Change Material ◽  
Metal Foam ◽  
Vertical Direction ◽  
Melting Time ◽  
Copper Foam ◽  
Average Porosity ◽  
The Impact ◽  
Change Material

The melting flow and heat transfer of copper-oxide coconut oil in thermal energy storage filled with a nonlinear copper metal foam are addressed. The porosity of the copper foam changes linearly from bottom to top. The phase change material (PCM) is filled into the metal foam pores, which form a composite PCM. The natural convection effect is also taken into account. The effect of average porosity; porosity distribution; pore size density; the inclination angle of enclosure; and nanoparticles’ concentration on the isotherms, melting maps, and the melting rate are investigated. The results show that the average porosity is the most important parameter on the melting behavior. The variation in porosity from 0.825 to 0.9 changes the melting time by about 116%. The natural convection flows are weak in the metal foam, and hence, the impact of each of the other parameters on the melting time is insignificant (less than 5%).

Natural Convection From Protruding Heat Sources in a Channel

2003 ◽  
Author(s):  
Tunc Icoz ◽  
Qinghua Wang ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Rayleigh Scattering ◽  
Convection Heat Transfer ◽  
Separation Distance ◽  
Natural Convection Heat Transfer ◽  
Temperature Profiles ◽  
Heat Sources ◽  
Convection Heat

Natural convection has important implications in many applications like cooling of electronic equipment due to its low cost and easy maintenance. In the present study, two-dimensional natural convection heat transfer to air from multiple identical protruding heat sources, which simulate electronic components, located in a horizontal channel has been studied numerically. The fluid flow and temperature profiles, above the heating elements placed between an adiabatic lower plate and an isothermal upper plate, are obtained using numerical simulation. The effects of source temperatures, channel dimensions, openings, boundary conditions, and source locations on the heat transfer from and flow above the protruding sources are investigated. Different configurations of channel dimensions and separation distances of heat sources are considered and their effects on natural convection heat transfer characteristics are studied. The results show that the channel dimensions have a significant effect on fluid flow. However, their effects on heat transfer are found to be small. The separation distance is found to be an important parameter affecting the heat transfer rate. The numerical results of temperature profiles are compared with the experimental measurements performed using Filtered Rayleigh Scattering (FRS) technique in an earlier study, indicating good agreement. It is observed that adiabatic upper plate assumption leads to better temperature predictions than isothermal plate assumption.

Numerical Survey of the Melting Driven Natural Convection Using Generation Heat Source: Application to the Passive Cooling of Electronics Using Nano-Enhanced Phase Change Material

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Hamza Faraji ◽  
Mustapha Faraji ◽  
Mustapha El Alami
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Source ◽  
Phase Change ◽  
Phase Change Material ◽  
Metallic Nanoparticles ◽  
Simple Algorithm ◽  
Bottom Side ◽  
Volume Method ◽  
Change Material

Abstract The present paper reports numerical results of the melting driven natural convection in an inclined rectangular enclosure filled with nano-enhanced phase change material (NePCM). The enclosure is heated from the bottom side by a flush-mounted heat source (microprocessor) that generates heat at a constant and uniform volumetric rate and mounted on a substrate (motherboard). All the walls are considered adiabatic. The purpose of the investigation is analyzing the effect of nanoparticles insertion by quantifying their contribution to the overall heat transfer. Combined effects of the PCM type, the inclination angle and the nanoparticles fraction on the structure of the fluid flow and heat transfer are investigated. A 2D mathematical model based on the conservation equations of mass, momentum, and energy was developed. The governing equations were integrated and discretized using the finite volume method. The SIMPLE algorithm was adopted for velocity–pressure coupling. The obtained results show that the nanoparticles insertion has an important quantitative effect on the overall heat transfer. The insertion of metallic nanoparticles with different concentrations affects the thermal behavior of the heat sink. They contribute to an efficient cooling of the heat source. The effect of nanoparticles insertion is also shown at the temperature distribution along the substrate.

scholarly journals Numerical Study of a New Solar Vacuum Tube Integrating with Phase Change Material

2019 ◽  
Vol 11 (24) ◽  
pp. 6960
Author(s):  
Juan Shi ◽  
Hua Xue ◽  
Zhenqian Chen ◽  
Li Sun
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Transfer Performance ◽  
Melting Time ◽  
Transfer Performance ◽  
Vacuum Tube ◽  
Fin Thickness ◽  
Phase Change Heat Transfer ◽  
Fin Spacing ◽  
Change Material

In this work, a new solar vacuum tube (SVT) integrating with phase change material is introduced and numerically investigated. The mathematical model and the numerical solution of phase change heat transfer is introduced. The heat transfer of the solar energy collection system during the energy storage process is simulated. Solid-liquid phase change characteristics of the SVT with paraffin inside is analyzed. Optimization analysis of fin structure parameters (fin thickness and fin spacing) in the vacuum tube is conducted. The results showed that the metal fin has a great effect on the phase change heat transfer of paraffin in SVTs. The closer the paraffin is to the fins, the more uniform the paraffin temperature is and the sooner the paraffin melts. As the fin thickness increases and the spacing between the fins decreases, the melting time of the paraffin decreases. Meanwhile, the effect of fin spacing on the overall heat transfer performance of the phase change energy storage tube is larger than the effect of the fin thickness. When the fin thickness is 2 mm, the melting time of paraffin with a fin spacing of 80 mm is 21,000 s, which is almost three times of that with a fin spacing of 10 mm (7400 s). Therefore, decreasing fin spacing is an effective way of enhancing phase change heat transfer. When the total fin volume is constant, a SVT with small fin space and small fin thickness performs better in heat transfer performance.

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.

Three-Dimensional Steady and Oscillatory Natural Convection in a Rectangular Enclosure With Heat Sources

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Amin Bouraoui ◽  
Rachid Bessaïh
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional ◽  
Air Cooling ◽  
Heat Sources ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Simpler Algorithm ◽  
Strong Relation

In this paper, a numerical study of three-dimensional (3D) natural convection air-cooling of two identical heat sources, simulating electronic components, mounted in a rectangular enclosure was carried out. The governing equations were solved by using the finite-volume method based on the SIMPLER algorithm. The effects of Rayleigh number Ra, spacing between heat sources d, and aspect ratios Ax in x-direction (horizontal) and Az in z-direction (transversal) of the enclosure on heat transfer were investigated. In steady state, when d is increased, the heat transfer is more important than when the aspect ratios Ax and Az are reduced. In oscillatory state, the critical Rayleigh numbers Racr for different values of spacing between heat sources and their aspect ratios, at which the flow becomes time dependent, were obtained. Results show a strong relation between heat transfers, buoyant flow, and boundary layer. In addition, the heat transfer is more important at the edge of each face of heat sources than at the center region.

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