Abstract
In this paper, nanofluids were prepared based on gold nanorods in basic fluid, water, by single-stage chemical reduction and in different volume fractions and the used gold nanorods were synthesized by seed-mediated growth method in different dimensional ratios. The properties of the prepared nanoparticles, including crystalline size, aspect ratio, surface properties, nanoparticle purity, shape and morphology of nanostructures were investigated using x-ray diffraction, UV-vis spectroscopy, FT-IR, and transmitted electron microscopy. The effect of changing parameters of Nano rod dimensions, changes in Nano rod volume fraction in water and also the effect of temperature on the nanofluid thermal conductivity coefficient were investigated using transient hot wire method. The results showed that reducing the aspect ratio, increasing the volume fraction and increasing the temperature increase the thermal conductivity. In fact, results show that an increase in the nanorods aspect ratio with a constant volume fraction of 1:50 of gold in water nanorod and at room temperature leads to a decrease in the thermal conductivity of the nanofluid. Also, increasing the two parameters of volume fraction and temperature significantly increases the thermal conductivity coefficient.
Highlights
Heat transfer plays a very important role in several key engineering sectors including microelectronics, power generation, transportation, automotive, aerospace, and nuclear power plants
Because of the calculations done Draine and Flatau (1994), using a discrete dipole approximation (DDA), an exact relationship is established between the longitudinal LSPR peak wavelength and the aspect ratio of the gold nanorods
A theory consisting of several mechanisms, such as liquid layering in the solid-liquid interface, the high surface-to-volume ratio of nanoparticles, and the Brownian motion of particles, can be considered as effective factors in increasing the thermal conductivity of nanofluids
Summary
Heat transfer plays a very important role in several key engineering sectors including microelectronics, power generation, transportation, automotive, aerospace, and nuclear power plants. Due to bugs in the use of traditional fluids and even micro-fluids, including sedimentation and deposition of particles, erosion, fouling of tubes and increasing pressure drop of the flow channel, the researchers turned to nanofluids (Eastman et al 2001). Nanoparticles are divided into three groups which are metallic, metallic oxides and non-metallic oxides that are dispersed in the base fluid. Two methods are considered for the preparation of nanoparticles: a two-stage method and a single-stage method. In a two-step procedure, the nanoparticles are first synthesized and dispersed in a base fluid. In a one-stage process the synthesis of nanoparticles (by methods such as chemical/physical deposition or chemical reduction) is occurred with the combination of it with the base fluid simultaneously (Yu, Xie 2012). Nanoparticles of several precious metals such as gold, silver, palladium and platinum have been investigated for the manufacture of nanofluids and their use in a variety of engineering applications due to their unique catalytic, electrical, magnetic, optical and mechanical properties (Tseng et al 2013)
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