Enhanced thermal conductivity of Ag-H20 nanofluid by pulsed laser ablation in liquid (PLAL)

Abstract

In this study, we present a straightforward, one-step pulsed laser ablation in liquid (PLAL) method for creating a surfactant-free nanofluid with silver nanoparticles suspended in water (AgNPs-H2O). The ND-YAG laser of 1064 nm wavelength is used to ablate a pure silver (Ag) target's surface in a deionized water base fluid under standard conditions. Six AgNPs-H2O nanofluids were synthesized, with concentrations corresponding to varied ablation periods (ta = 2.5; 5; 10; 15; 20; and 25 min). The synthesized nanofluid was characterised for morphology, composition, optical properties, stability tests, thermal properties, and surface tension. The nanoparticles in the water organised into an aggregate network of spherical nanoparticles, with sizes averaging between 21 and 37 nm. Apart for carbon from coating during SEM and EDS examinations, no contaminants are detected from a basic study in the fluid that is produced. AgNPs are dispersed throughout our water host fluid, as evidenced by a plasmonic peak in the UV-vis spectrum at 400 nm. Unfortunately, these nanofluids are not stable with time, at higher concentration of AgNPs in water, they settle under gravitation. That is why we lose some plasmonic peaks at high concentration (ta = 10; 15; 20; and 25 min) and only at low concentration (ta = 2.5 and 5 min) where AgNPs are stable even after 5 months.). The thermal characteristics of the generated samples were evaluated using thermal conductivity measurements, which were carried out at various nanoparticle concentrations and at temperatures ranging from 25 °C to 45 °C. The results showed that the thermal rise of Ag-water nanofluid was larger than that of pure water. When temperature rises, nanofluids become more thermally conductive. The thermal conductivity improvement was found to be around 19.45% at a temperature of 45°C and a nanoparticle volume percent of ta = 5 min. This results from the instability of AgNP at higher concentrations. Also, we assessed the contact angle, which unmistakably demonstrates that it is concentration dependant. So, even at low concentrations, the presence of silver nanoparticles will have an impact on the flow of the silver-water nanofluid. Also, it is demonstrated that a tube's surface will influence fluid flow, demonstrating the importance of careful design