Join us at the International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES).
The thermal conductivities of paraffin-based composite phase change materials (PCMs) containing different types of graphene nanoparticles were determined using the transient plane source method. It was determined that the thermal conductivity was increased by the addition of the nanoparticles, and the enhancement was greater for composites containing larger, and stiffer nanoparticles.
Four different paraffin-based nanocomposite phase change materials (PCMs) were prepared by dispersion of 20 v. % of graphene, multi-walled carbon nanotubes (MWCNTs), aluminum, or TiO2 nanoparticles into a paraffin matrix. It was found that the two carbon-based nanoparticles reduced the time required for melting and solidification of the PCM by a greater amount than the two other nanoparticles. The graphene-paraffin PCM was found to reduce the melt and re-solidification time by the greatest amount (~30%), and the authors attributed this to the enhanced thermal conductivity in this nanocomposite PCM, which was nearly 2800% higher than that of the pure paraffin PCM. In addition to the reduced melt and re-solidification time, the graphene-paraffin PCM was also found to increase the amount of the thermal energy that can be recovered from the PCM by 11%.
The authors have carried out an experimental and numerical study on the effects of seeding Al2O3 nanoparticles in a paraffin wax phase change material (PCM) on the thermal conductivity and the latent heat of fusion. It was determined that the addition of the nanoparticles (up to 1 wt. %) resulted in the nano-PCM having a higher thermal conductivity than the pure paraffin wax. The latent heat of fusion was also found to increase with the addition of the nanoparticles. A numerical analysis was performed simulating the effects of heating the base of a rectangular box containing one of the PCMs with three different heating powers. It was found that the addition of the nanoparticles resulted in slower melting process in comparison to the pure paraffin wax.
Zinc sulfide nanoparticles were embedded in a poly(methyl methacrylate) matrix to prepare a nanocomposite polymer with a higher thermal conductivity than the pure polymer. It was determined by TEM that at a low concentration of filler particles, the particles are uniformly dispersed throughout the matrix; however, at higher concentrations, agglomeration of the filler particles occurs. The effective thermal conductivity for all samples was found to increase with increasing temperature until the glass transition temperature was attained. After this point, the thermal conductivity became constant as temperature increased. The thermal conductivity was also found to increase with increasing filler content, up to 6 wt. %. The thermal conductivity of the sample containing 8 wt. % ZnS was found to be lower than that containing 6 wt. % ZnS. The authors suggest that this decrease is due to increased particle agglomeration in the 8 wt. % sample.
CdS nanoparticles were dispersed in varying quantities into a PVC matrix and the effective thermal conductivities of the produced nanocomposites were investigated at temperatures from 25 to 110C. It was determined that the dispersion of the nanoparticles in PVC caused an increase in thermal conductivity up to 2 wt. % filler concentration when compared to that of pure PVC. When more than 2 wt. % of filler was added to the PVC matrix, the thermal conductivity began to decrease, and the sample containing 8 wt. % CdS nanoparticles was found to have an effective thermal conductivity that was lower than that of pure PVC. Temperature was also found to have an effect on the thermal conductivity. Conductivity was found to increase in all samples until the temperature reached the glass transition temperature. Past this point, the thermal conductivity of each sample became almost constant as temperature increased.
