Investigation on Thermal Properties Enhancement of Peg/Cnt Composites As Pcm For Thermal Energy Storage

Polyethylene glycol (peg) as a phase change material (pcm) can be used for thermal energy storage (tes)# melting point and phase change enthalpy of this material are in appropriate range; 20#3 ℃ and approximately 100 j/g, respectively# however, its low thermal conductivity (~ 0#2 w/m#k) limits its application# therefore, in this project thermal conductivity of peg was enhanced by utilizing carbon nanotubes (cnt)# in order to achieve good compatibility, cnt was first functionalized with surface modification by acid nitric# the modification caused agglomeration which results in improper dispersion# hence, sonication and planetary ball mill were used for breaking up the agglomerates# the optical microscope (om) images showed that planetary ball mill was more effective and reduced the cluster size to 2 µm# then, composites of peg/cnt were synthesized successfully with cnt loading of 1 and 2 wt#%# thermal conductivity of the composites were investigated and showed approximately 60% improvement in thermal conductivity of peg with 2 wt#% cnt# other thermal properties were studied by differential scanning calorimetry (dsc)# the results showed negligible change in phase change enthalpies# melting and crystallization enthalpy of peg with 2 wt#% cnt reduced by 1#3 and 5#7%, respectively# it was also observed that the supercooling degree of peg/cnt composite decreased by 46#20% in comparison to the neat sample# it reveals that cnt also acts as nucleating agent for peg# also, specific heat capacities (cp) of peg and the composite with 2wt#% cnt versus temperature were calculated from dsc results#