No abstract

No abstract

Improving the performance of heat transfer fluids is altogether significant. The best approach for improving the thermal conductivity is the addition of nanoparticles to the base fluid. In the present study, specific heat, dynamic viscosity, and thermal conductivity of water-based Indian coal fly ash stable nanofluid for 0.1% to 0.5% volume concentration in the temperature range of 30 to 60°C has been investigated. To evaluate an average particle diameter of 11.5 nm, the fly ash nanoparticles were characterized with scanning electron microscopy and dynamic light scattering. Using zeta potential, the stability of nanofluid in the presence of surfactant Triton X-100 was tested. Thermal conductivity and viscosity of fly ash nanofluid increased, while specific heat decreased as volume concentration increased. The effect of temperature on the fly ash nanofluid was directly proportional to its thermal conductivity and specific heat and inversely proportional to viscosity.

No abstract

The present study investigates the effect of ball milling on thermal conductivity and viscosity of stable nanofluid of fly ash from Indian coal. The particle size of fly ash decreased from micron size to 89, 55.5, and 11.5 nm with reduction by 55, 90, and 434 times, respectively, due to ball milling for 30, 40, and 60 hours. The surfactant Triton X-100 was used to attain stability of 0.1% and 0.5% volume concentration of fly ash nanofluid. The samples were characterized by using scanning electron microscopy, dynamic light scattering, and zeta potential analysis. The outcome reveals that the thermal conductivity of fly ash nanofluid increases with temperature, volume concentration, and reduction in particle size. A maximum enhancement in thermal conductivity of 11.9% with 11.5-nm nanofluid sample and 5.4% with 89-nm nanofluid sample for 0.5% concentration at 60°C is observed. The viscosity of fly ash nanofluid increases with concentration and varies inversely with particle size and temperature. A difference of 1.6% in viscosity is observed between the values obtained with 11.5 and 89 nm nanofluid samples for 0.5% concentration at 30°C. K E Y W O R D S fly ash nanofluid, heat transfer, stability, thermophysical properties Nanofluids can be known as fluids in which solid particles smaller than 100 nm in dimension are dispersed and distributed randomly in a base fluid, such as water, oil, glycerin, and so forth. Nanofluids can be used as heat transfer fluids. 1-3 Nanofluids are shown to have notable thermophysical properties, that is, viscosity, thermal conductivity, density, specific heat, and so forth, which are crucial for applications involving single-phase convection heat transfer. The properties of nanoparticles and base fluid affect the thermophysical properties of nanofluids. Lee et al 4 used molecular dynamic simulation studies to examine the thermal conductivity and viscosity of copper nanoparticles dispersed in liquid argon. They studied the effect of particle size and temperature in the concentration range of 2.19% to 7.77% vol. Particle diameters of 1.5 and 2.0 nm were considered for testing the dependence of particle size at a temperature of 86K. For nanofluids with a particle diameter of 2.0 nm, the effect of temperature range from 86 to 101K has been further studied. They reported that thermal conductivity improves with particle size and is independent of temperature, but the viscosity varies inversely with particle size and temperature. Nguyen et al 5 examined the influence of particle size (36 and 47 nm) on Al 2 O 3-water nanofluid viscosity and reported no significant variation in the values for concentration lower than 4% vol. However, at higher concentration, the viscosity was higher for 47 nm. He et al 6 concluded that large agglomerated TiO 2 nanofluid had higher viscosity in contrast with a smaller cluster. Sozen et al 7 determined the thermal performance of a two-phase closed thermosyphon with fly ash nanofluid at various function states. They reported the efficiency of heat pipe increased by...