Novel MgCl2-KCl/expanded graphite/graphite paper composite phase change blocks with high thermal conductivity and large latent heat

Solar Energy ◽  
2018 ◽  
Vol 159 ◽  
pp. 226-233 ◽  
Author(s):  
Junwan Liu ◽  
Min Xie ◽  
Ziye Ling ◽  
Xiaoming Fang ◽  
Zhengguo Zhang
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Latent Heat ◽  
Expanded Graphite ◽  
High Thermal Conductivity

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.

scholarly journals The Impact of Additives on the Main Properties of Phase Change Materials

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3064 ◽  
Author(s):  
Ewelina Radomska ◽  
Lukasz Mika ◽  
Karol Sztekler
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
High Thermal Conductivity ◽  
Liquid Transition ◽  
Supercooling Degree ◽  
Wide Range ◽  
Solid Liquid ◽  
The Impact

The main drawback of phase change materials (PCMs) is their low thermal conductivity, which limits the possibilities of a wide range of implementations. Therefore, the researchers, as found in the literature, proposed several methods to improve the thermal conductivity of PCMs, including inserting high thermal conductivity materials in nano-, micro-, and macro-scales, as well as encapsulation of PCMs. However, these inserts impact the other properties of PCMs like latent heat, melting temperature, thermal stability, and cycling stability. Hence, this paper aims to review the available in the open literature research on the main properties of enhanced PCMs that undergo solid–liquid transition. It is found that inserting high thermal conductivity materials and encapsulation results in improved thermal conductivity of PCMs, but it decreases their latent heat. Moreover, the insertions can act as nucleating agents, and the supercooling degree can be reduced. Some of the thermal conductivity enhancers (TCEs) may prevent PCMs from leakage. However, some test results are inconsistent and some seem to be questionable. Therefore, this review indicates these discrepancies and gaps in knowledge and points out possible directions for further research.

Study on Phase-Change Temperature and Latent Heat of Organic Phase-Change Nano-Fluid

2010 ◽  
Vol 152-153 ◽  
pp. 1591-1594 ◽  
Author(s):  
Jian You Long
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Latent Heat ◽  
Organic Phase ◽  
High Thermal Conductivity ◽  
Phase Change Temperature ◽  
Nano Fluid ◽  
Change Temperature ◽  
Surface Modified

Nano-aluminum, which has high thermal conductivity and good compatibility, was added into paraffin to improve its thermal conductivity. Surface modified technology was adopted and dispersant was used to prepare uniform and stable organic phase-change nano-fluid of paraffin and nano-aluminum. Experiments were conducted to test the phase-change temperature and latent heat of the prepared organic phase-change nano-fluid. Results show that the addition of nano-aluminum has no effect on phase-change temperature, but it changes phase-change latent heat of the prepared organic phase-change nano-fluid. Reduced degree of the latent heat is nearly proportional to the quantity of the added nano-aluminum.

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.

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