Solid-Volume-Fraction Retained Tailoring of Thermal Diffusivity of Multiwalled Carbon Nanotube Nanofluid: A Photothermal Investigation

The diversified forms of heat engines necessitate developing energy-efficient engine oils and coolants. The article proposes a method of thermal diffusivity tuning of the base fluid (ethylene glycol) using multiwalled carbon nanotubes (MWCNTs), annealed at different temperatures, without altering the solid volume fraction. Having studied the annealing-induced structure modifications of MWCNTs through thermogravimetric and spectroscopic studies, the thermal diffusivity variations are investigated through the sensitive photothermal mode-mismatched dual-beam thermal lens technique. The study reveals that the annealing-induced structure modifications lower the nanofluid's thermal diffusivity and unveils the existence of transition annealing temperature of MWCNTs above which the nanoparticles can make the nanofluid a heat trapper. The study also proposes the importance of making more energy-efficient engine oils by keeping the temperature of the engine oil below the transition temperature.

Automated summary

Diversified heat engines require energy-efficient engine oils and coolants. This article proposes a method of tuning the thermal diffusivity of the base fluid (ethylene glycol) by using multiwalled carbon nanotubes (MWCNTs) annealed at different temperatures, without changing the solid volume fraction. The study investigates the structure modifications of MWCNTs induced by annealing and explores the variations in thermal diffusivity using the photothermal mode-mismatched dual-beam thermal lens technique. The research reveals that annealing-induced structure modifications decrease the thermal diffusivity of the nanofluid and identifies a transition annealing temperature above which the nanoparticles can act as heat trappers. The study also emphasizes the importance of maintaining the temperature of engine oil below the transition temperature for more energy-efficient engine oils.