Preparation and Properties of Capric-Lauric-Palmitic Acid Eutectic Mixtures/Expanded Graphite Composite as Phase Change Materials for Energy Storage

2014 ◽  
Vol 1028 ◽  
pp. 40-45 ◽  
Author(s):  
Xue Huang ◽  
Yling De Cui ◽  
Bu Ning Zhang ◽  
Guo Qiang Yin ◽  
Guang Zhu Feng
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Melting Temperature ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Ternary Eutectic ◽  
Eutectic Mixture ◽  
Expanded Graphite ◽  
Mass Ratio ◽  
Eutectic Mixtures

This work is focused on the preparation and properties of ternary fatty acid eutectic mixtures/ expanded graphite form-stable phase change materials (PCMs). Based on the theoretical calculation of the mass ratio and ternary eutectic melting temperature, the ternary eutectic mixture of capric acid (CA), lauric acid (LA) and palmitic acid (PA) was prepared firstly, which is for the sake of decreasing the phase transformation temperature. Thermal characteristics such as melting temperature and latent heat of fusion of these developed eutectics measured by using Differential Scanning Calorimetry (DSC) technique, which also showed that the eutectic mixture was composed by CA, LA and PA in the mass ratio of 59.7:30.1:10.02. Then the CA–LA–PA was absorbed in expanded graphite (EG), which acts as a supporting material, the optimum mass ratio of CA–LA–PA to EG is 17:1. The CA–LA–PA/EG composites were characterized by the scanning electronic microscope (SEM), differential scanning calorimeter (DSC). The SEM observations showed that the CA–LA–PA was adsorbed into the porous structure of EG, instead of any chemical action. The DSC results indicated that the phase change temperature and latent heat of the CA–LA–PA and CA–LA–PA/EG were 19.92 °Cand 19.48 °C, and 135.49 J/g and 130.73 J/g respectively. The thermal conductivity of CA–LA–PA /EG composite PCM was improved by the high thermal conductivity of the EG. Thermal cycling test showed that the CA–LA–PA/EG composite had a good thermal reliability. All results indicated that CA–LA–PA/EG composite PCM has a proper melting temperature and latent heat for building energy conservation.

Optimization of Filling Mass Fraction for Composite PCMs Based Thermal Management System

2017 ◽  
Author(s):  
Bofeng Shang ◽  
Jinyan Hu ◽  
Xingjian Yu ◽  
Bin Xie ◽  
Ruikang Wu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Phase Change ◽  
Latent Heat ◽  
Mass Fraction ◽  
Phase Change Materials ◽  
Matrix Material ◽  
Expanded Graphite ◽  
Working Time ◽  
Transfer Model

Phase Change Materials (PCMs) have been widely investigated as a cooling solution due to their significant latent heat capacity. However, the current PCMs generally suffer a low thermal conductivity, thus hindering the application of PCMs. Composite Phase Change Materials (CPCMs) filling with high thermal conductivity materials have been proposed to solve this issue. Nevertheless, the latent heat of the CPCMs decreases with the mass fraction of fillings, thus leading to a lower allowable working time under safe operating temperature. Therefore, an optimal filling mass fraction of CPCMs is in urgent needed to improve the application of CPCMs. In this study, we developed a one-dimensional conduction heat transfer model of CPCMs to predict the optimal filling mass fraction of CPCMs to realize the maximum allowable working time. The filling mass fraction was introduced into the model and the relationship between the thermal conductivity and latent heat was built. We adopted paraffin as the matrix material and Expanded Graphite (EG) as the thermal conductivity enhancer. The allowable working time of the CPCMs as the function of filling mass fraction was obtained. Based on the principle of the maximum allowable working time, the optimal filling mass fraction was calculated. Comparative experiments were also conducted to validate the accuracy of the prediction model. The parameters which affect the maximum allowable working temperature were also investigated, including input heat flux, safe temperature, and height of CPCMs. The results show that a higher heat flux and height requires a larger filling mass fraction, and it’s opposite for the safe temperature.

Thermal Properties Analysis of Several N-Alkanes Eutectic Mixtures Applied in Building Envelopes

2012 ◽  
Vol 512-515 ◽  
pp. 3007-3010
Author(s):  
Jing Yu Huang ◽  
Shi Lei Lv ◽  
Chen Xi Zhang ◽  
Zhi Wei Wang
Keyword(s):  
Thermal Properties ◽  
Melting Temperature ◽  
Latent Heat ◽  
Heat Storage ◽  
Eutectic Mixture ◽  
Scanning Calorimetry ◽  
Latent Heat Storage ◽  
Building Envelopes ◽  
Eutectic Mixtures ◽  
Change Material

This study focuses on the preparation, thermal properties of alkanes eutectic mixtures (n-Octadecane/n-Eicosane, n-Octadecane/n-Docosane and n-Heptadecane /n-Eicosane) as candidate phase change material (PCM) for low temperature latent heat storage systems in building envelopes. Their melting temperature and latent heat were tested by Differential scanning calorimetry (DSC). The testing values were closed to calculation values of accepted theory that ensured the reliability of those datas. The results indicated n-Octadecane/n-Docosane eutectic mixture was more promising PCM for buildings in terms of melting temperature (25.3°C) and latent heat values of melting (158.2J/g).

scholarly journals Expanded Graphite/Paraffin/Silicone Rubber as High Temperature Form-stabilized Phase Change Materials for Thermal Energy Storage and Thermal Interface Materials

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 894 ◽  
Author(s):  
Yafang Zhang ◽  
Wang Li ◽  
Juhua Huang ◽  
Ming Cao ◽  
Guoping Du
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Silicone Rubber ◽  
Phase Change Materials ◽  
Expanded Graphite ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Excellent Thermal Stability ◽  
Interface Materials

In this work, expanded graphite/paraffin/silicone rubber composite phase-change materials (PCMs) were prepared by blending the expanded graphite (EG), paraffin wax (PW) and silicone rubber (SR) matrix. It has been shown that PW fully penetrates into the three dimensional (3D) pores of EG to form the EG/PW particles, which are sealed by SR and evenly embedded in the SR matrix. As a result of the excellent thermal stability of SR and the capillary force from the 3D pores of EG, the EG/PW/SR PCMs are found to have good shape stability and high reliability. After being baked in an oven at 150 °C for 24 h, the shape of the EG/PW/SR PCMs is virtually unchanged, and their weight loss and latent heat drop are only 7.91 wt % and 11.3 J/g, respectively. The latent heat of the EG/PW/SR composites can reach up to 43.6 and 41.8 J/g for the melting and crystallizing processes, respectively. The super cooling of PW decreased from 4.2 to 2.4 due to the heterogeneous nucleation on the large surface of EG and the sealing effect of the SR. Meanwhile, the thermal conductivity of the EG/PW/SR PCMs reaches 0.56 W·m−1·K−1, which is about 2.8 times and 3.73 times of pure PW and pristine SR, respectively. The novel EG/PW/SR PCMs with superior shape and thermal stabilities will have a potential application in heat energy storage and thermal interface materials (TIM) for electronic devices.

Latent Heat Storage: Container Geometry, Enhancement Techniques, and Applications—A Review

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
S. Arunachalam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Low Thermal Conductivity

Energy storage helps in waste management, environmental protection, saving of fossil fuels, cost effectiveness, and sustainable growth. Phase change material (PCM) is a substance which undergoes simultaneous melting and solidification at certain temperature and pressure and can thereby absorb and release thermal energy. Phase change materials are also called thermal batteries which have the ability to store large amount of heat at fixed temperature. Effective integration of the latent heat thermal energy storage system with solar thermal collectors depends on heat storage materials and heat exchangers. The practical limitation of the latent heat thermal energy system for successful implementation in various applications is mainly from its low thermal conductivity. Low thermal conductivity leads to low heat transfer coefficient, and thereby, the phase change process is prolonged which signifies the requirement of heat transfer enhancement techniques. Typically, for salt hydrates and organic PCMs, the thermal conductivity range varies between 0.4–0.7 W/m K and 0.15–0.3 W/m K which increases the thermal resistance within phase change materials during operation, seriously affecting efficiency and thermal response. This paper reviews the different geometry of commercial heat exchangers that can be used to address the problem of low thermal conductivity, like use of fins, additives with high thermal conductivity materials like metal strips, microencapsulated PCM, composite PCM, porous metals, porous metal foam matrix, carbon nanofibers and nanotubes, etc. Finally, different solar thermal applications and potential PCMs for low-temperature thermal energy storage were also discussed.

scholarly journals Preparation and Properties of Lauryl Alcohol-Caprylic Acid Eutectics/Activated Charcoal Composites as Shape-stabilized Phase Change Materials for Cold Energy Storage

2020 ◽  
Vol 26 (3) ◽  
pp. 300-307
Author(s):  
Yuan LIU ◽  
Yanghua CHEN
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Activated Charcoal ◽  
Caprylic Acid ◽  
Phase Change Materials ◽  
Lauryl Alcohol ◽  
Mass Ratio ◽  
Cold Energy ◽  
Ft Ir

A novel form-stable composite phase change materials for cold energy storage were prepared using physical blending adsorption method. In the shape-stabilized composites, lauryl alcohol (LA) and caprylic acid (CA) were employed as phase change materials, which were blended together at specific mass ratio based on theoretical calculations. Activated charcoal (AC) was selected as supporting material due to its advantages like large specific surface area and high thermal conductivity. The composites were characterized by field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectrometer (FT-IR), differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). The results of FE-SEM and FT-IR displayed that the eutectics of LA and CA was well absorbed and dispersed homogeneously into the porous network structure of the AC and the melted eutectics was not easy to leak from the reticular structure. Moreover, there was only physical absorption between the eutectic mixture and AC. The results of DSC and TGA indicated that phase change temperature and latent heat of the prepared composites increased with the increase of the binary eutectics mass ratio and AC can enhance the thermal stability of composites. The composites with the mass ratio 60% of the eutectics melted at – 0.21 ℃ with a latent heat enthalpy of 28.08 J/g and solidified at – 2.33 ℃ with a latent solidification enthalpy of 29.70 J/g. The prepared composites will contribute to cold energy storage of low temperature range.

Composite phase change materials improve the photo-thermal effects of cotton fabrics

2020 ◽  
pp. 004051752097561
Author(s):  
Wei Zhang ◽  
Shang Hao ◽  
Jiali Weng ◽  
Yibo Zhang ◽  
Jiming Yao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Surface Temperature ◽  
Ambient Temperature ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Effects ◽  
Phase Change Materials ◽  
Thermal Storage ◽  
Cotton Fabrics ◽  
Composite Phase Change Materials

We report on the impregnation-based preparation of composite phase change materials (CPCMs) with thermal storage properties, using paraffin wax and multi-walled carbon nanotubes (MWCNTs). We coated the CPCMs on the fabric by scraper coating, then evaluated their shape stability, latent heat, thermal conductivity, thermal storage stability and photo-thermal effects. Results show that CPCMs with 10% acid-oxidized MWCNTs introduce only a small phase leakage when heated at 50℃ for 900 s; their latent heat energy reduces by 16.5%, while their thermal conductivity increases by 131.9% compared to pure paraffin. When exposed to sunlight at an ambient temperature of 12.5℃, the cotton fabrics coated with CPCMs record a 12.8℃ higher surface temperature than the pristine fabric, while their heat dissipation is delayed by 120–180 s. The fabric surface temperature increases to twice the ambient temperature during daytime. Overall, these findings indicate that the coated fabric has excellent thermal stability, affirming its potential as photo-thermal functional material.

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