Preparation And Thermal Performance Of Water Based Nanofluids Of Encapsulated Phase Change Materials And Multiwalled Carbon Nanotubes

Suspensions of paraffin microencapsules and nanofluids of multiwalled carbon nanotubes have been prepared respectively.The effects of additions of two surfactants,i.e.,GA?gum arabic?and SDBS?sodium dodecyl benzene sulfonate?,on the stability of the suspensions of paraffin microencapsules were studied.The effects of the addition of GA,ultrasonic oscillation and functionalization of multiwalled carbon nanotubes on the stability of multiwalled carbon nanotubes fluids were investigated.The results showed that the stability of the suspensions of paraffin microencapsules was the best when GA was used as the dispersant.It is necessary to use surfactants and sonicating to obtain stable nanofluids of multiwalled carbon nanotubes.By functionalizing the multiwalled carbon nanotubes with hydrophilic groups,can stable nanofluids of multiwalled carbon nanotubes be obtained.The stability mechanism of the two kinds of fluid has been discussed.It was thought that under the influence of ultrasonic,the formation adsorption layer of GA on the surface of multiwalled carbon nanotube is the key to obtain better stability of the nanofluids of multiwalled carbon nanotubes;And a large number of hydroxyl and carboxyl formed on the surface of functionalization of carbon nanotubes,greatly improved its stability in the water.The nanocapsules PA@SiO₂ with phase change material PA?palmitic acid?as core material and SiO₂ as shell material were prepared by interfacial polymerization method.Optimization of the preparation process of PA@SiO₂ nanocapsules has been achieved.The effects of the amounts of TEOS?tetraethyl orthosilicate?and the pH values of the solution on the structure and thermal properties of PA@SiO₂nanocapsules were studied.With PA of 2.5 g,TEOS of 2.5 mL and pH value of 7,PA@SiO₂ nanocapsules with smooth surface,and an average size of about 474 nmcan be get.The nanocapsules have high latent heat and thermal stability.Its melting and solidification latent heat are 109.9 J/g and 100.1 J/g,respectively.Finally,three different nanofluids,i.e.,nanofluids of paraffin microcapsules/multiwalled carbon nanotubes,nanofluids of paraffin microcapsules/functionalized multiwalled carbon nanotubes,nanofluifs of PA@SiO₂ nanocapsules/functionalized multiwalled carbon nanotubes were prepared respectively.Their suspension stability,thermal properties etc.were studied.Among the three kinds of fluids,nanofluid of PA@SiO₂ nanocapsules/functionalized multiwalled carbon nanotubes is the best.