scholarly journals Review of Thermophysical Property Data of Octadecane for Phase-Change Studies

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2974 ◽  
Author(s):  
Moritz Faden ◽  
Stephan Höhlein ◽  
Joschka Wanner ◽  
Andreas König-Haagen ◽  
Dieter Brüggemann
Keyword(s):  
Solid State ◽  
Liquid Phase ◽  
Confidence Interval ◽  
Phase Change ◽  
Thermophysical Property ◽  
Confidence Intervals ◽  
Material Properties ◽  
Solid Phase ◽  
Temperature Dependent ◽  
Property Data

In this work we derive temperature-dependent functions for the most important material properties needed for phase change studies with octadecane. Over 80 references are reviewed in which at least one thermophysical property of octadecane is measured. The functions are valid ±40 K around the melting temperature and are surrounded by their confidence interval. It turns out that the values for the solid phase have much broader confidence intervals than the ones of the liquid phase. Hence, more accurate measurements are particularly desirable for the solid state material properties.

Modelling Semi-Solid Behaviour and Brittle Temperature Range

2019 ◽  
Vol 285 ◽  
pp. 361-366 ◽  
Author(s):  
Khalil Traidi ◽  
Véronique Favier ◽  
Philippe Lestriez ◽  
Karl Debray ◽  
Laurent Langlois ◽  
...  
Keyword(s):  
Solid State ◽  
Material Properties ◽  
Solid Phase ◽  
Thermal Conditions ◽  
Tensile Tests ◽  
Internal Variable ◽  
Temperature Dependent ◽  
Brittle Transition ◽  
Semi Solid ◽  
First Time

In this paper, a new elastic viscoplastic micromechanical modelling is proposed to represent the semi-solid behaviour and predict the ductile-brittle transition of the C38LTT near the solidus. It is based on a viscoplastic modelling previously presented in [1]. The originality of the new model comes from three main enhancements: the transition between the solid state and the semi-solid state was included meaning that the material properties were taken temperature-dependent, the elastic properties was taken into account similarly as [2] and the evolution of the internal variable describing the degree of agglomeration of the solid phase was enhanced. The model was implemented in the commercial software FORGE©. Tensile tests representing the experimental thermal conditions and obtained using a GLEEBLE© machine were simulated. The comparison of the predicted and experimental results shows that, for the first time to our knowledge, the three steps of the load-displacement response and ductile-brittle transition were successfully described.

Thermal Conductivity Enhancement in a Latent Heat Storage Device

2013 ◽  
Vol 860-863 ◽  
pp. 590-593
Author(s):  
Cha Xiu Guo ◽  
Ding Bao Wang ◽  
Gao Lin Hu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Solid State ◽  
Liquid Phase ◽  
Phase Change ◽  
Latent Heat ◽  
Heat Storage ◽  
Storage Device ◽  
Latent Heat Storage ◽  
Conductivity Enhancement

High conductivity porosity materials are proposed to enhance the phase change materials (PCM) in order to solve the problem of low conductivity of PCM in the latent heat storage device (LHSD), and two-dimensional numerical simulation is conducted to predict the performance of the PCM by CFD software. During the phase change process, the PCM is heated from the solid state to the liquid phase in the process of melting and from the liquid phase to the solid state in the solidification process. The results show that porosity materials can improve heat transfer rate effectively, but the effect of heat transfer of Al foam is superior to that of graphite foam although the heat storage capacity is almost the same for both. The heat transfer is enhanced and the solidification time of PCM is decreased since the effective thermal conductivity of composite PCM is increased.

Synthesis and Characterization of Solid State Phase Change Material Microcapsules for Thermal Management Applications

2013 ◽  
Author(s):  
Fangyu Cao ◽  
Jing Ye ◽  
Bao Yang
Keyword(s):  
Heat Capacity ◽  
Solid State ◽  
Phase Change ◽  
Thermal Management ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Silica Shell ◽  
Heat Transfer Fluid ◽  
Change Behavior

Polyalcohols such as neopentyl glycol (NPG) undergo solid-state crystal transformations that absorb/release sufficient latent heat. These solid-solid phase change materials (PCM) can be used in practical thermal management applications without concerns about liquid leakage and thermal expansion during phase transition. In this paper, microcapsules of NPG encapsulated in silica shell were successfully synthesized with the use of the emulsion technique. The size of the microcapsules was in the range of 0.2–4 μm, and the thickness of the silica shell was about 30 nm. It was found that the endothermic event of the phase change behavior of these NPG-silica microcapsules was initiated at around 39 °C and the latent heat was about 96.0 J/g. A large supercooling of about 43.3 °C was observed in the pure NPG particles without shell. The supercooling of the NPG microcapsules can be reduced to about 14 °C due to the heterogeneous nucleation sites provided by the silica shell. These NPG microcapsules were added into heat transfer fluid PAO to enhance its heat capacity. The effective heat capacity of the fluids can be increased by 56% by adding 20 wt. % NPG-silica microcapsules.

Energy Storage With Solid/Liquid Phase Change in Presence of Natural Convection

2001 ◽  
Author(s):  
M. Pinelli ◽  
S. Piva
Keyword(s):  
Natural Convection ◽  
Energy Storage ◽  
Liquid Phase ◽  
Phase Change ◽  
Change Process ◽  
Solid Phase ◽  
High Energy ◽  
Heat Transfer Process ◽  
Phase Change Process ◽  
Solid Liquid

Abstract Solid/liquid phase change process has received great attention for its capability to obtain high energy storage efficiency. In order to analyse these systems, undergoing a solid/liquid phase change, in many situations the heat transfer process can be considered conduction-dominated. However, in the past years, it has been shown that natural convection in the liquid phase can significantly influence the phase change process in terms of temperature distributions, interface displacement and energy storage. In this paper, a procedure to analyse systems undergoing liquid/solid phase change in presence of natural convection in the liquid phase based on the utilisation of a commercial computer code (FLUENT), has been developed. This procedure is applied to a cylinder cavity heated from above and filled with a Phase Change Material. It was found that when the coupling with the environment, even if small, is considered, natural convection in the liquid phase occurs. The numerical results are then compared with available experimental data. The analysis shows that the agreement between numerical and experimental results is significantly improved when the results are obtained considering the presence of circulation in the liquid phase instead of considering the process only conduction-dominated. Furthermore, some interesting features of the flow field are presented and discussed.

Synthesis and Characterization of Solid-State Phase Change Material Microcapsules for Thermal Management Applications

2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Fangyu Cao ◽  
Jing Ye ◽  
Bao Yang
Keyword(s):  
Heat Capacity ◽  
Solid State ◽  
Phase Change ◽  
Thermal Management ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Silica Shell ◽  
Heat Transfer Fluid ◽  
Nucleation Sites

Polyalcohols such as neopentyl glycol (NPG) undergo solid-state crystal transformations that absorb/release significant latent heat. These solid–solid phase change materials (PCM) can be used in practical thermal management applications without concerns about liquid leakage and thermal expansion during phase transitions. In this paper, microcapsules of NPG encapsulated in silica shells were successfully synthesized with the use of emulsion techniques. The size of the microcapsules range from 0.2 to 4 μm, and the thickness of the silica shell is about 30 nm. It was found that the endothermic phase transition of these NPG-silica microcapsules was initiated at around 39 °C and the latent heat was about 96.0 J/g. A large supercooling of about 43.3 °C was observed in the pure NPG particles without shells, while the supercooling of the NPG microcapsules was reduced to about 14 °C due to the heterogeneous nucleation sites provided by the silica shell. These NPG microcapsules were added to the heat transfer fluid PAO to enhance its heat capacity and the effective heat capacity of the fluid was increased by 56% with the addition of 20 wt. % NPG-silica microcapsules.

Solid/Liquid Phase Change in Presence of Natural Convection: A Thermal Energy Storage Case Study

2003 ◽  
Vol 125 (3) ◽  
pp. 190-198 ◽  
Author(s):  
M. Pinelli ◽  
S. Piva
Keyword(s):  
Natural Convection ◽  
Energy Storage ◽  
Liquid Phase ◽  
Phase Change ◽  
Change Process ◽  
Solid Phase ◽  
High Energy ◽  
Heat Transfer Process ◽  
Phase Change Process ◽  
Solid Liquid

Solid/liquid phase change process has received great attention for its capability to obtain high energy storage efficiency. In order to analyze these systems, undergoing a solid/liquid phase change, in many situations the heat transfer process can be considered conduction-dominated. However, in the past years, it has been shown that natural convection in the liquid phase can significantly influence the phase change process in terms of temperature distributions, interface displacement and energy storage. In this paper, a procedure to analyze systems undergoing liquid/solid phase change in presence of natural convection in the liquid phase based on the utilisation of a commercial computer code (FLUENT), has been developed. This procedure is applied to the study of a cylinder cavity heated from above and filled with a phase change material. It was found that when the coupling with the environment, even if small, is considered, natural convection in the liquid phase occurs. The numerical results are then compared with available experimental data. The analysis shows that the agreement between numerical and experimental results is significantly improved when the results are obtained considering the presence of circulation in the liquid phase instead of considering the process only conduction-dominated. Furthermore, some interesting features of the flow field are presented and discussed.

scholarly journals Temperature leveling of electronic chips by solid-solid phase change materials compared to solid-liquid phase change materials

2021 ◽  
Vol 179 ◽  
pp. 121731
Author(s):  
Masaaki BABA ◽  
Kosei NEMOTO ◽  
Daiki OTAKI ◽  
Takuto SASAKI ◽  
Masatoshi TAKEDA ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Phase Change ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Solid Liquid

scholarly journals Excess Li2O Additives to Promote Grain Boundary Growth and Improve Ionic Conductivity of LiTa2PO8 Solid Electrolytes

2021 ◽  
Vol 8 ◽  
Author(s):  
Qian Zhang ◽  
Fuhai Meng ◽  
Ruixiong Liao ◽  
Long Chen ◽  
Mengqian Xu ◽  
...  
Keyword(s):  
Solid State ◽  
Liquid Phase ◽  
Ionic Conductivity ◽  
Grain Boundary ◽  
Solid Phase ◽  
Synthesis Method ◽  
Lithium Ion ◽  
Liquid Phase Sintering ◽  
Diffusion Activation Energy ◽  
The Impact

LiTa2PO8 (LTPO) is a new solid-state lithium ion electrolyte material reported in the latest research, which has high bulk ionic conductivity and low grain boundary ion conductivity. However, it is difficult to density with conventional sintering methods. Herein, in this work, the solid-phase synthesis method was used to prepared the LTPO solid-state electrolyte, and the influence of the amount of lithium on the structure and performance of LTPO electrolyte material was investigated. The results show that the excess Li2O does not increase other impurities and does not change the structure of the material, but the liquid phase produced by the excess Li2O can promote the elimination of interfacial pores, accelerate the direct bonding of grains and improve the ionic conductivity of grain boundary, thus improving the overall ionic conductivity of the material. Considering the volatilization of lithium and the impact of liquid phase sintering at high temperatures and the content restructuring, after adding 20 wt% excess formulation of Li2O, the resultant of LTPO density is 5.0 g/cm3, the density reaches 85.58%. As a result, the total ionic conductivity of the electrolyte is 3.28 × 10–4 S/cm at 25°C, and the Li-ion diffusion activation energy is 0.27 eV. In addition, after loading this electrolyte into a Li–Li symmetric battery, it is proved that the electrolyte has lithium ion transport performance and can be used in all-solid-state batteries. However, it is also found from cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) analysis that the interface between LTPO material and Li is unstable, and Ta5+ ions are reduced, which will be another key issue to be addressed in the future.

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