Experimental investigation of natural convection heat transfer of Al2O3 Nanoparticle Enhanced Ionic Liquids (NEILs)

Abstract

Experimental investigations were carried out regarding natural convection heat transfer of Nanoparticle Enhanced Ionic Liquids (NEILs) in rectangular enclosures of two different sizes with dimensions length×width×height, 50×50×50mm and 50×50×75mm in heated from below. The NEILs were synthesized by dispersing different wt% (0.5, 1.0, and 2.5) of alumina (Al 2 O 3) nanoparticles of two different particle shapes (spherical and whiskers) into N-butyl-Nmethylpyrrolidinium bis{(trifluoromethyl)sulfonyl} imide, ([C 4 mpyrr][NTf 2 ]) ionic liquid (IL). Heat transfer related thermophysical properties, i.e. density, viscosity, thermal conductivity, and heat capacity of base IL and NEILs were also measured and reported. The experimental measurement shows enhanced density, thermal conductivity, viscosity, and heat capacity of NEILs compared to the base IL and they increase with the nanoparticle concentration. However natural convection heat transfer coefficient was observed to deteriorate for the NEILs compared to the base IL irrespective of the shapes of the particles and aspect ratio of the enclosure and the deterioration increases with the increase of nanoparticle concentration. Interestingly spherical Al 2 O 3 NEILs was observed to affect more adversely compared to the whiskers Al 2 O 3 NEILs. The observed degradation of the heat transfer performance of the NEILs could not fully be explainedby the change ofthermophysical properties, which indicates that other factors may playsignificant roles in this phenomenon and the possible reasons of the degradation is discussed in this paper.

Enhanced thermophysical properties of NEILs as heat transfer fluids for solar thermal applications

“…Fox et al [17] have studied different nanoparticles effect on thermophysical properties of NEILs and reported that whisker-shaped Al 2 O 3 nanoparticles show highest thermal conductivity enhancement. Paul et al [18][19] have reported the higher forced convection heat transfer coefficients [18] and deterioration of the natural convection [19]…”

Ionic Liquids-Based Nanocolloids—A Review of Progress and Prospects in Convective Heat Transfer Applications

“…Most of the new fluids contain little concentration of nanoparticles, up to 1 %wt. with several exceptions when the nanoparticles fractions are up to 0.05 (see, for example, Franca et al [26], Paul [61], Paul et al [62], Chereches et al [47,65], Hosseinghorbani et al [68]). As for base fluids, several ionic liquids were considered and few authors, such as, for example, Xie et al [37] and Chereches et al [47,60], made mixtures between water and ILs.…”

“…Most of the experimental studies, as can be seen from Table 4, noticed an increase in viscosity when nanoparticles were added to the ionic liquids, depending on nanoparticles mass concentration (see, for example, Paul et al [62], Fox et al [72]). Besides that, several authors (see Patil et al [60], Ferreira et al [3], Zhang et al [68]) found a decrease in viscosity when nanoparticles were added and explained this phenomenon relying on the low density and lubricating properties of nanoparticles, on the interactions between the ions of ILs and the MWCNT, which can hardly be acceptable without a scientific explanation.…”

“…Only a handful of experimental works from a single research group on convective heat transfer of ILs and their nanofluids (INFs) are reported in the literature [62,[77][78][79][80]. The findings of those works are summarized in Table 7.…”

Estimating the Heat Capacity of Non-Newtonian Ionanofluid Systems Using ANN, ANFIS, and SGB Tree Algorithms

“…To apply the above methods and construct an accurate model, in the first stage, a set of experimental data points for the network training is introduced. A review of empirical studies has been performed, and the C p values of some NEILs with wide ranges of nanoparticle concentrations and temperatures were found [20,21,[77][78][79]. The total collected experimental dataset (571) was randomly split into two parts: training (75%) and testing (25%) subsets.…”