CFD simulation of melting process of phase change materials (PCMs) in a spherical capsule

2017 ◽  
Vol 73 ◽  
pp. 209-218 ◽  
Author(s):  
H. Sattari ◽  
A. Mohebbi ◽  
M.M. Afsahi ◽  
A. Azimi Yancheshme
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Cfd Simulation ◽  
Melting Process ◽  
Spherical Capsule

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.

Detailed Numerical Modeling of a Hybrid PCM-Air Heat Sink

2013 ◽  
Author(s):  
Y. Kozak ◽  
G. Ziskind
Keyword(s):  
Numerical Modeling ◽  
Phase Change ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Void Formation ◽  
Solidification Process ◽  
Melting Process ◽  
Significant Rise ◽  
Air Interface ◽  
Vof Model

The ability of phase-change materials (PCMs) to absorb large amounts of heat without significant rise of their temperature during the melting process may be utilized in thermal energy storage and passive thermal management. This paper deals with numerical modeling of a hybrid PCM-air heat sink, in which heat may be either absorbed by the PCM stored in compartments with conducting walls, or dissipated to the air using fins, or both. Under the assumptions of perfect insulation (except for the air fins), identity and symmetry between all PCM channels, and negligible 3-D boundary effects, a 2-D model of the problem for half a PCM compartment of the heat sink is solved, saving calculation time and yet taking into account the essential physical phenomena. A commercial program, ANSYS Fluent, is used in order to solve the governing conservation equations. Phase-change is solved using the enthalpy-porosity method. PCM-air interface is modeled using the volume-of-fluid (VOF) approach. The model takes into account natural convection in the liquid PCM and air, volume change, phase- and temperature-dependence of thermal properties, and PCM-air interface interaction. Various scenarios for the hybrid heat sink operation are simulated and compared. The difference in the melting patterns is analyzed for the cases of heating with and without the fan operating. The solidification process with the fan operating is also simulated. It is shown that the VOF model enables simulating realistic void formation in the solidification process.

Melting of Phase Change Materials With Volume Change in Metal Foams

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Zhen Yang ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Phase Change ◽  
Volume Change ◽  
Phase Change Materials ◽  
Metal Foam ◽  
Melting Process ◽  
Metal Foams ◽  
Volume Shrinkage ◽  
Two Temperature

Melting of phase change materials (PCMs) embedded in metal foams is investigated. The two-temperature model developed accounts for volume change in the PCM upon melting. Volume-averaged mass and momentum equations are solved, with the Brinkman–Forchheimer extension to Darcy’s law employed to model the porous-medium resistance. Local thermal equilibrium does not hold due to the large difference in thermal diffusivity between the metal foam and the PCM. Therefore, a two-temperature approach is adopted, with the heat transfer between the metal foam and the PCM being coupled by means of an interstitial Nusselt number. The enthalpy method is applied to account for phase change. The governing equations are solved using a finite-volume approach. Effects of volume shrinkage/expansion are considered for different interstitial heat transfer rates between the foam and PCM. The detailed behavior of the melting region as a function of buoyancy-driven convection and interstitial Nusselt number is analyzed. For strong interstitial heat transfer, the melting region is significantly reduced in extent and the melting process is greatly enhanced as is heat transfer from the wall; the converse applies for weak interstitial heat transfer. The melting process at a low interstitial Nusselt number is significantly influenced by melt convection, while the behavior is dominated by conduction at high interstitial Nusselt numbers. Volume shrinkage/expansion due to phase change induces an added flow, which affects the PCM melting rate.

scholarly journals Effect of Inclined Magnetic Field on the Entropy Generation in an Annulus Filled with NEPCM Suspension

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Seyyed Masoud Seyyedi ◽  
M. Hashemi-Tilehnoee ◽  
M. Sharifpur
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Phase Change ◽  
Entropy Generation ◽  
Phase Change Materials ◽  
Transfer Problem ◽  
Mass Conservation ◽  
Melting Process ◽  
Industrial Applications ◽  
Inclined Magnetic Field

The encapsulation technique of phase change materials in the nanodimension is an innovative approach to improve the heat transfer capability and solve the issues of corrosion during the melting process. This new type of nanoparticle is suspended in base fluids call NEPCMs, nanoencapsulated phase change materials. The goal of this work is to analyze the impacts of pertinent parameters on the free convection and entropy generation in an elliptical-shaped enclosure filled with NEPCMs by considering the effect of an inclined magnetic field. To reach the goal, the governing equations (energy, momentum, and mass conservation) are solved numerically by CVFEM. Currently, to overcome the low heat transfer problem of phase change material, the NEPCM suspension is used for industrial applications. Validation of results shows that they are acceptable. The results reveal that the values of N u ave descend with ascending Ha while N gen has a maximum at Ha = 16 . Also, the value of N T , MF increases with ascending Ha . The values of N u ave and N gen depend on nondimensional fusion temperature where good performance is seen in the range of 0.35 < θ f < 0.6 . Also, Nu ave increases 19.9% and ECOP increases 28.8% whereas N gen descends 6.9% when ϕ ascends from 0 to 0.06 at θ f = 0.5 . Nu ave decreases 4.95% while N gen increases by 8.65% when Ste increases from 0.2 to 0.7 at θ f = 0.35 .

scholarly journals Experimental evaluation of phase change material in radiant cooling panels integrated with thermoelectric modules

2019 ◽  
Vol 111 ◽  
pp. 01002
Author(s):  
Yong-Kwon Kang ◽  
Beom-Jun Kim ◽  
Soo-Yeol Yoon ◽  
Jae-Weon Jeong
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Phase Change Materials ◽  
Target Surface ◽  
Melting Process ◽  
Night Time ◽  
Thermoelectric Modules ◽  
Radiant Cooling ◽  
Change Material

This study proposes a phase change material for use in radiant cooling panels integrated with thermoelectric modules (PCM–TERCP) and evaluates its performance characteristics during the solidification and melting process of phase change materials in design conditions. The PCM–TERCP consists of phase change materials (PCMs), thermoelectric modules (TEMs), and aluminumpanels. TEMs operate to freeze the PCM, and PCM stores the cooling thermal energy to maintain the constant surface temperature of the panel for radiant cooling. The main purpose of thermal energy storage systems is the shift of the electricity consumption from day-time to night-time during the summer season. Therefore, PCM–TERCP can implement off-peak operation according to which energy is expected to be saved. The melting temperature of PCM and the target surface temperatures of the bottom panels of PCM–TERCP were designed to be 16°C. Additionally, the room temperature and mean radiant temperature (MRT) was set to 24°C, while the thickness of the PCM pouch was 10 mm. As a result, the solidification process required 4 h and the total input power was 0.528 kWh. Correspondingly, the melting process can operate passively over a period of 4 h. In most cases, the operating temperature was lower than 19°C, which validates the temperature response of PCM–TERCP.

scholarly journals Temperature Control in (Translucent) Phase Change Materials Applied in Facades: A Numerical Study

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3286 ◽  
Author(s):  
Tenpierik ◽  
Wattez ◽  
Turrin ◽  
Cosmatu ◽  
Tsafou
Keyword(s):  
Temperature Gradient ◽  
Phase Change ◽  
Specific Heat ◽  
Melting Temperature ◽  
Phase Change Materials ◽  
Numerical Study ◽  
Melting Process ◽  
Large Temperature ◽  
Energy Efficient Buildings ◽  
High Solar Radiation

Phase change materials (PCMs) are materials that can store large amounts of heat during their phase transition from solid to liquid without a significant increase in temperature. While going from liquid to solid this heat is again released. As such, these materials can play an important role in future energy-efficient buildings. If applied in facades as part of a thermal buffer strategy, e.g., capturing and temporarily storing solar energy in so-called Trombe walls, the PCMs are exposed to high solar radiation intensities, which may easily lead to issues of overheating. This paper therefore investigates the melting process of PCM and arrives at potential solutions for countering this overheating phenomenon. This study uses the simulation program Comsol to investigate the heat transfer through, melting of and fluid flow inside a block of PCM (3 × 20 cm2) with a melting temperature of around 25 °C. The density, specific heat and dynamic viscosity of the PCM are modeled as a temperature dependent variable. The latent heat of the PCM is modeled as part of the specific heat. One side of the block of PCM is exposed to a heat flux of 300 W/m2. The simulations show that once part of the PCM has melted convection arises transporting heat from the bottom of the block to its top. As a result, the top heats up faster than the bottom speeding up the melting process there. Furthermore, in high columns of PCM a large temperature gradient may arise due to this phenomenon. Segmenting a large volume of PCM into smaller volumes in height limits this convection thereby reducing the temperature gradient along the height of the block. Moreover, using PCMs with different melting temperature along the height of a block of PCM allows for controlling the speed with which a certain part of the PCM block starts melting. Segmenting the block of PCM using PCMs with different melting temperature along its height was found to give the most promising results for minimizing this overheating effect. Selecting the optimal phase change temperatures however is critical in that case.

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