Ultrasonication time optimization for multi-walled carbon nanotube based Therminol-55 nanofluid: an experimental investigation

The main theme of the work is to examine the influence of ultrasonication time on colloidal stability and thermal conductivity (TC) of multi-walled carbon nanotubes (MWCNTs)-Therminol 55 based nanofluid. Three different volume percentages of nanofluid samples have been produced namely 0.09, 0.18, and 0.3 vol.% by adopting various ultrasonication times, varying from 30 to 120 min. The colloidal stability of the nanofluid samples has been examined over one month after formulation through carrying out zeta potential examination and visual inspection method. From the results it can be concluded that an increase in the sonication time up to 120 min results in the improved colloidal stability of nanofluid samples. Extending sonification time beyond 60 min weakened the nanofluid stability. The nanofluid TC of the samples has been measured experimentally over various temperatures ranging from 30 to 50 °C. It is noticed that rising the nanofluid temperature outcomes in decreasing the nanofluid TC, whereas it was incremented with rise in MWCNT concentration. Besides, the impacts of ultrasonication time on stability and TC have been examined, and it is noticed that rising the time of ultrasonication inducting a quiet augmentation in nanofluid TC. The highest TC was attained by employing 60 min time of ultrasonication.