Nanoparticles Shape Effect on Viscosity and Thermal Conductivity of Ionic Liquids Based Nanofluids

Abstract

Ionic liquids (ILs) are considered a potential candidate for a heat transfer fluid (HTF) in concentrated solar power (CSP) applications. There are already many CSP sites in operation throughout the world. These complex energy systems use various subsystems such as mirrors and lenses to concentrate solar energy onto a central collector. These CSP sites rely on having a stable HTF in order to maintain high energy storage capacity and to reduce costs. This research seeks to develop a robust set of workable data that can be used to better understand the nanoparticles shape effect on viscosity and thermal conductivity of ionic liquids (ILs) based nanofluids. ILs based nanofluids were prepared by pouring 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C4mim][NTf2]) base IL and Al2O3 nanoparticles. Three different particle shapes (platelets, blades, and spherical) were used to prepare the 1 wt% ILs based nanofluids. Experimental results shows that the needleshaped nanoparticle provided the greatest effective thermal conductivity compared to the base ILs.

Thermal Conductivity and Viscosity: Review and Optimization of Effects of Nanoparticles

“…A higher surface area to volume ratio means higher heat transfer as heat transfer depends on surface area. Main et al [ 65 ] measured the thermal conductivity of sphere, rod and needle shaped Al 2 O 3 -1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ((C4 mim) (NTf2)) nanofluids. The nanofluid containing needle shaped particles had the highest thermal conductivity.…”

“…The thermal conductivity of the nanofluid containing wire shaped particles was higher than the sphere-shaped particles. The small diameter particles provide the best increase in thermal conductivity due to their high aspect ratio in other research [ 65 ]. The high aspect ratio of the wires could explain their superior enhancement in thermal conductivity to the sphere-shaped particles as aspect ratio strongly correlates to the surface area to volume ratio.…”

“…Figure 27 conveys the thermal conductivity and viscosity as a function of temperature for various shaped nanofluids with ((C4 mim) (NTf2])) as a base liquid. Specifically, shaped nanoparticles of sphere, rod, and needle are compared with the measurements from [ 65 ]. It can be concluded from the graph that the difference in shape is not clear on its effects on the viscosity of the nanofluid as they all are crowding each other.…”

“… Thermal conductivity (increasing with temperature) and viscosity (decreasing with temperature) for 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ((C4mim) (NTf2)) based nanofluid with Al 2 O 3 particles that are 2–5 nm diameter and 70–100 nm length needles, 10 nm diameter and 100 nm length rods, and 10 nm diameter spheres at 1 wt % [ 65 ]. …”

Nanofluid Heat Transfer: Enhancement of the Heat Transfer Coefficient inside Microchannels

“…Cubic nanoparticles will not necessarily always have the highest surface area to volume ratio, as depending on the particular dimensions of the nanoparticles, it is possible for other shapes to have a higher surface area to volume ratio. Main et al [37] measured the thermal conductivity of ionic liquid based nanofluids, specifically Al 2 O 3 -1-Butyl-3methylimidazolium bis(trifluoromethylsulfonyl) imide ([C4mim] [NTf2]) nanofluids, with various nanoparticle shapes. The nanoparticles used had a variety of shapes, such as sphere, rod, and needle.…”