Abstract
A striking contrast in the thermal conductivities of polyethylene glycol (PEG)/diatomite form-stable phase change composite (fs-PCC) with single-walled carbon nanotubes (SWCNs) as nano-additive has been reported in our present study. Compared to the pure PEG, the thermal conductivity of the prepared fs-PCC has increased from 0.24 W/mK to 0.87 W/Mk with a small SWCNs loading of 2 wt%. SWCNs are decorated on the inner surface of diatomite pores whilst retaining its porous structure. Compared to PEG/diatomite fs-PCC, the melting and solidification time of the PEG/diatomite/SWCNs fs-PCC are respectively decreased by 54.7% and 51.1%, and its thermal conductivity is 2.8 times higher. The composite can contain PEG as high as 60 wt% and maintain its original shape perfectly without any PEG leakage after subjected to 200 melt-freeze cycles. DSC results indicates that the melting point of the PEG/diatomite/SWCNs fs-PCC shifts to a lower temperature while the solidification point shifts to a higher temperature due to the presence of SWCNs. Importantly, the use of SWCNs is found to have clear beneficial effects for enhancing the thermal conductivity and thermal storage/release rates, without affecting thermal properties, chemical compatibility and thermal stability. The prepared PEG/diatomite/SWCNs fs-PCC exhibits excellent chemical and thermal durability and has potential application in solar thermal energy storage and solar heating.
Highlights
Our study has reported a high thermal conductive PEG/Dt/single-walled carbon nanotubes (SWCNs) form-stable composite
SWCNs were randomly distributed on the surface of diatomite whilst retaining its porous structure (SEM, transmission electron microscope (TEM), BET and XPS results)
With a small SWCN loading of 2 wt% a strikingly high, 260% enhancement is obtained in the thermal conductivity, compared to the pure PEG
Summary
The results showed that the thermal conductivity increased about 105% for the highest loading of CNS at 50 wt%. SWCN is a fascinating family member of the carbon based nano-materials, which is characteristic for its outstanding thermal conductivity[9]. This study attempts to develop a novel form-stable PCM composite with high thermal conductivity. PEG is the PCM, diatomite (Dt) was used as the supporting material, and SWCNs were employed as the high thermal conductive additive. The effective thermal conductivities of the prepared PEG/ Dt/SWCNs fs-PCCs have been tested using the laser flash method and the microstructures were analyzed using transmission electron microscope (TEM). The resulting PEG/Dt/SWCNs fs-PCC is a potential solar thermal energy storage material for residential heating and domestic hot-water production
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