scholarly journals Polyethylene Glycol-Carbon Nanotubes/Expanded Vermiculite Form-Stable Composite Phase Change Materials: Simultaneously Enhanced Latent Heat and Heat Transfer

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 889 ◽  
Author(s):  
Yong Deng ◽  
Mingyue He ◽  
Jinhong Li ◽  
Zhiwei Yang
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Polyethylene Glycol ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Storage Capacity ◽  
Heat Storage ◽  
Inhibition Effect ◽  
Expanded Vermiculite ◽  
Composite Phase Change Materials

Polyethylene glycol (PEG)-carbon nanotubes (CNTs) with expanded vermiculite (EVM) form-stable composite phase change materials (PCE-CPCMs) were constructed via the efficient synergistic effect between EVM and CNTs. The resultant material demonstrated simultaneously enhanced latent heat and heat transfer. The unique EVM pore structure and CNTs surfaces contributed to the form stability of PCE-CPCMs. The adsorption capacity was 77.75–81.54 wt %. The latent heat of the PCE-CPCMs increased with increasing CNTs content due to the decreasing inhibition effect of EVM and the increasing adsorption capacity of PEG, which was 83.9 J/g during melting and 104.2 J/g during solidification for PCE7.09. The pore confinement and surface EVM interactions inhibited the heat storage capacity of the PCE-CPCMs. Moreover, the inhibition effect on the heat storage capacity of PCE-CPCMs during the melting process was stronger than during solidification due to the crystallization-promoting effect. The heat transfer of PCE-CPCMs was significantly enhanced by the CNTs filler (0.5148 W/(m·K) for PCE7.09) due to the decrease in interfacial thermal resistance and the formation of rapid thermally conductive pathways. Fourier transform infrared spectroscopy, thermogravimetric analysis, and thermal cycles test results confirmed that the PCE-CPCMs exhibited excellent chemical compatibility, thermal stability, and reliability.

Polyethylene Glycol/Expanded Vermiculite Shape-Stabilized Composite Phase Change Materials for Thermal Energy Storage

2016 ◽  
Vol 847 ◽  
pp. 39-45
Author(s):  
Yong Deng ◽  
Jin Hong Li ◽  
Ting Ting Qian ◽  
Wei Min Guan ◽  
Xiang Wang
Keyword(s):  
Polyethylene Glycol ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Vacuum Impregnation ◽  
Impregnation Method ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Expanded Vermiculite ◽  
Composite Phase Change Materials

Polyethylene glycol (PEG)/ expanded vermiculite (EVMT) shape-stabilized composite phase change material (ss-CPCM) was prepared by a facile vacuum impregnation method. The maximum mass percentage for PEG retained in ss-CPCM was 75.1 wt.% due to specific non-uniform flat layers pore structure of EVMT. The scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) analysis results indicated that the melted PEG was adsorbed on the surface and completely dispersed into the pores of EVMT and no chemical changes took place during the heating and cooling processes. X-ray diffraction (XRD) results showed that the crystal structure of PEG was not destroyed after impregnation whereas the crystallization process of PEG was greatly restrained. Differential scanning calorimetry (DSC) results indicated that ss-CPCM melted at 57.61°C with a latent heat of 103.1 J/g and solidified at 33.19°C with a latent heat of 88.29 J/g. In addition, the thermal conductivity of ss-CPCM reached 0.418W/m K. The ss-CPCM can be considered as promising candidate materials for building applications due to their suitable phase change temperature, large latent heat and excellent chemical compatibility.

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.

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