scholarly journals Numerical Analysis of Melting Process in a Rectangular Enclosure with Different Fin Locations

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4091
Author(s):  
Bin Huang ◽  
Lin-Li Tian ◽  
Qing-Hua Yu ◽  
Xun Liu ◽  
Zu-Guo Shen
Keyword(s):  
Natural Convection ◽  
Liquid Flow ◽  
Thermal Stratification ◽  
Flow Resistance ◽  
Waste Heat ◽  
Melting Process ◽  
Melting Behavior ◽  
Bottom Surface ◽  
Melting Time ◽  
Change Material

Latent thermal energy storage is regarded as an effective strategy to utilize solar energy and recover automotive waste heat. Based upon an enthalpy-porosity method, the influence characteristics and mechanism of fin location on phase change material melting behavior in vertical rectangular enclosures were explored numerically. The results show that as fin location increases, the melting time decreases before attaining the minimum at the fin location of 0.20 after which it increases and finally surpasses the no fin case, because (1) the influence range of fins for conduction is limited by the bottom surface when putting fins next to this surface, (2) the liquid flow resistance increases with moving fins up, and (3) mounting fins near the top surface accelerates melting at the upper part, facilitating thermal stratification formation and weakening natural convection. Nu is higher than the no fin case, i.e., Nu enhancement factor is a positive value, in the melting process for a lower fin location, while for other fin locations, a transition to a negative value takes place. The higher the fin location is, the earlier the transition that arises. Finally, a strategy of increasing the maximum liquid flow velocity is proposed to reinforce melting for cases with considerable natural convection.

scholarly journals Numerical Investigations on Melting Behavior of Phase Change Material in a Rectangular Cavity at Different Inclination Angles

2018 ◽  
Vol 8 (9) ◽  
pp. 1627 ◽  
Author(s):  
Yong Wang ◽  
Jingmin Dai ◽  
Dongyang An
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Melting Process ◽  
Melting Behavior ◽  
Rectangular Cavity ◽  
Melting Time ◽  
Inclination Angles ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Change Material

This paper investigates the melting process of phase change material in a rectangular cavity at different inclination angles. Paraffin is used as a phase change material in this study. One side of the cavity is heated while the other sides are considered to be adiabatic. The investigated angles of inclination include 0° (bottom horizontal heating), 30°, 60°, 90° (vertical heating), 120°, 150° and 180° (top horizontal heating). Shapes of the solid liquid interface and temperature variations during the melting process were discussed for all the inclination angles. The results reveal that the inclination angles have a significant impact on the melting behavior of paraffin. As the angle increases from 0° to 180°, the complete melting time increases non-linearly.

scholarly journals Optimizing the shape of PCM container to enhance the melting process

2022 ◽  
Author(s):  
Bingkun Huang ◽  
Shimi Yang ◽  
Jun Wang ◽  
Peter D Lund
Keyword(s):  
Natural Convection ◽  
Heat Storage ◽  
Design Method ◽  
Heating Surface ◽  
Melting Process ◽  
Design Guidelines ◽  
Melting Time ◽  
Latent Heat Storage ◽  
Rectangular Container ◽  
Change Material

Abstract The shape of container influences natural convection inside a latent heat storage with a phase change material (PCM). Often the geometrical design of a PCM container is based on empirical observations. To enhance convection and melting of the PCM, authors propose here new design guidelines for an improved container. Using the so-called Co-factor method as the optimized basis, which is defined as the vector product of the velocity and temperature gradient, the new design method strives to raise the velocity of natural convection in liquid PCM, increase the amount of PCM in the direction of the convective flow, and reduce the amount of PCM far from the heating surface. Following these guidelines and Co factor, an optimized PCM container with an elongated and curved shape is proposed and compared to a rectangular container. Numerical simulations indicated that the total melting time of the PCM in the optimized container could be reduced by more than 20% compared to the rectangular one. The higher natural convection velocity and the better use of it to melt the PCM in the optimized container space attributed to the better performance than that in rectangular container. The results can be used to design more effective PCM storage systems.

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%).

Heat Transfer Enhancement of Finned Copper Foam/Paraffin Composite Phase Change Material

2021 ◽  
Vol 14 ◽  
Author(s):  
Tingting Wu ◽  
Yanxin Hu ◽  
Xianqing Liu ◽  
Changhong Wang ◽  
Zijin Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Transfer Rate ◽  
Flow Resistance ◽  
Phase Change Materials ◽  
Heat Transfer Performance ◽  
Melting Process ◽  
Copper Foam ◽  
Composite Phase Change Material ◽  
Change Material

Background: The employment of Phase Change Materials (PCMs) provides a potential selection for heat dissipation and energy storage. The main reason that hinders the wide application is the low thermal conductivity of PCMs. Combining the proper metal fin and copper foam, the fin/composite phase change material (Fin-CPCM) structure with good performance could be obtained. However, the flow resistance of liquid paraffin among the porous structure has seldom been reported, which will significantly affect the thermal performance inside the metal foam. Furthermore, the presence of porous metal foam is primarily helpful for enhancing the heat transfer process from the bottom heat source. The heat transfer rate is slow due to the one-dimensional heat transfer from the bottom. It should be beneficial for improving the heat transfer performance by adding external fins. Therefore, in the present study, a modified structure by combining the metal fin and copper foam is proposed to further accelerate the melting process and improve the temperature uniformity of the composite. Objective: The purpose of this study is to research the differences in the heat transfer performance among pure paraffin, Composite Phase Change Materials (CPCM) and fin/Composite Phase Change Material (Fin-CPCM) under different heating conditions, and the flow resistance of melting paraffin in copper foam. Methods: To experimentally research the differences in the heat transfer performance among pure paraffin, CPCM and Fin-CPCM under different heating conditions, a visual experimental platform was set up, and the flow resistance of melting paraffin in copper foam was also analyzed. In order to probe into the limits of the heat transfer capability of composite phase change materials, the temperature distribution of PCMs under constant heat fluxes and constant temperature conditions was studied. In addition, the evolution of the temperature distributions was visualized by using the infrared thermal imager at specific points during the melting process. Results: The experimental results showed that the maximum temperature of Fin-CPCM decreased by 21°C under the heat flux of 1500W/m2 compared with pure paraffin. At constant temperature heating conditions, the melting time of Fin-CPCM at a temperature of 75°C is about 2600s, which is 65% less than that of pure paraffin. Due to the presence of the external fins, which brings the advantage of improving the heat transfer rate, the experimental result exhibited the most uniform temperature distribution. Conclusion: The addition of copper foam can accelerate the melting process. The addition of external fins brings the advantage of improving the heat transfer rate, and can make the temperature distribution more uniform.

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.

scholarly journals Melting process modeling of Carreau non-Newtonian phase- change material in dual porous vertical concentric cylinders

2020 ◽  
pp. 329-329
Author(s):  
Mohsen Talebzadegan ◽  
Mojtaba Moravej ◽  
Ehsanolah Assareh ◽  
Mohsen Izadi
Keyword(s):  
Porous Media ◽  
Rayleigh Number ◽  
Phase Change ◽  
Phase Change Material ◽  
Melting Process ◽  
Darcy Number ◽  
Melting Time ◽  
Stefan Number ◽  
Concentric Cylinders ◽  
Change Material

In this paper a numerical simulation of the melting process of Carreau non- Newtonian phase-change material (PCM) inside two porous vertical concentric cylinders included constant temperatures of the inner and outer walls, represented by Th and Tc respectively. Half of the void between the two pipes is filled with copper porous media and paraffin wax as a phase change material. The governing equations are converted into a dimentionless form and are solved using the finite element method. The enthalpy- porosity theory is applied to simulate the phase change of PCM while the porous media follow to the Darcy law. Outcomes are shown and compared in terms of the streamline, isotherm, melting fraction and mean Nusselt numbers. The solid- liquid interface location and the temperature distribution are predicted to describe the melting process. The effects of the Carreau index, porosity and non-dimensional parameters such as Stefan number, Darcy number and Rayleigh number are analyzed. Our results indicate a good agreement between this study and the previous investigations. The results show that an increase in Rayleigh number, Stefan number and Darcy number increases the melting volume fraction and reduces the melting time. Also, the time of melting non-Newtonian phase change material decreases when Carreau index and porosity decrease.

Thermodynamics of Energy Storage by Melting Due to Conduction or Natural Convection

1990 ◽  
Vol 112 (2) ◽  
pp. 110-116 ◽  
Author(s):  
M. De Lucia ◽  
A. Bejan
Keyword(s):  
Energy Source ◽  
Natural Convection ◽  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Melting Process ◽  
Absolute Temperature ◽  
Design Parameters ◽  
Environment Temperature ◽  
Change Material

This paper describes the most basic thermodynamic aspects of the process of energy storage by melting of a phase change material when the energy source is a stream of hot single-phase fluid. The first part of the paper considers the melting process ruled by pure conduction across the liquid phase, and the second part deals with the quasi-steady melting dominated by natural convection. The paper establishes the relationship between the total irreversibility of the melting process and design parameters such as the number of heat transfer units of the heat exchanger placed between the energy source and the phase change material, the duration of the melting process, and the position of the energy storage process on the absolute temperature scale. It is shown that the exergy transfer to the melting material is maximized when the melting temperature (Tm) equals the geometric average of the environment temperature (Te) and the temperature of the energy source (T∞), in other words when Tm=(TeT∞)1/2. This conclusion holds for both conduction-dominated melting and convection-dominated melting.

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 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.

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