Effects of Particle Surface Charge, Species, Concentration, and Dispersion Method on the Thermal Conductivity of Nanofluids

Abstract

The purpose of this experimental study is to evaluate the effects of particle species, surface charge, concentration, preparation technique, and base fluid on thermal transport capability of nanoparticle suspensions (nanofluids). The surface charge was varied by changing the pH value of the fluids. The alumina (Al 2 O 3 ) and copper oxide (CuO) nanoparticles were dispersed in deionized (DI) water and ethylene glycol (EG), respectively. The nanofluids were prepared using both bath-type and probe sonicator under different power inputs. The experimental results were compared with the available experimental data as well as the predicted values obtained from Maxwell effective medium theory. It was found that ethylene glycol is more suitable for nanofluids applications than DI water in terms of thermal conductivity improvement and stability of nanofluids. Surface charge can effectively improve the dispersion of nanoparticles by reducing the (aggregated) particle size in base fluids. A nanofluid with high surface charge (low pH) has a higher thermal conductivity for a similar particle concentration. The sonication also has a significant impact on thermal conductivity enhancement. All these results suggest that the key to the improvement of thermal conductivity of nanofluids is a uniform and stable dispersion of nanoscale particles in a fluid.

Thermo-physical properties and thermo-magnetic convection of ferrofluid

“…Philip et al [13] studied the effect on thermal conductivity of low volume fraction of Fe3O4 nanofluids with particle size of 6 nm in different base fluids and found that the enhancement could approach 25%, as shown in Few studies show that the thermal conductivity enhancement of nanofluid is higher when the suspended nanoparticles have higher thermal conductivity [17,18]. Thermal conductivity studies done on Cu, CuO and Al 2 O 3 water, ethylene glycol and transformer oil based nanofluids show high thermal conductivity for metallic nanofluids compared to oxide nanoparticles [18].…”

Review on Synthesis, Thermo-Physical Property, and Heat Transfer Mechanism of Nanofluids

“…Kwak et al [71] concluded that the large increase in thermal conductivity and viscosity at low nanoparticle volume fraction is an indication of aggregation effects. This has created interest in understanding the clustering phenomenon, and various studies have been conducted in this regard [72][73][74][75][76]. Interestingly, Prashaer et al [77] combined aggregation kinetics based on colloidal chemistry with the physics of thermal transport, and found that sedimentation is considerably visible due to aggregation, which negatively affects the thermal conductivity of nanofluids.…”

Experimental investigation and model development for effective viscosity of Al2O3–glycerol nanofluids by using dimensional analysis and GMDH-NN methods

“…The dispersion of nanoparticles into conventional heat transfer fluids such as ethylene glycol, glycerol, engine oil, gear oil and water are of special interest due to their reported unique behaviors [5][6][7]. It is a known fact that conventional heat transfer fluids are characteristically poor in thermal properties [8,9]. Moreover, several studies [10][11][12][13] have shown that the addition of nanoparticles to these conventional heat transfer fluids increases their thermal conductivity, heat capacity, electrical conductivity and convective heat transfer coefficient when used in flow equipment.…”

“…Some major contributions have been made in the area of thermofluids engineering and these contributions have been reported in the literature. Gowda et al [8] showed that the enhancement in the thermal conductivity of nanofluids is dependent on nanoparticle type, nanoparticle volume fraction, nanoparticles surface charge, base fluid type and the overall energy input into the nanofluid preparation. Other researchers have shown that the thermal properties of nanofluid are also dependent on temperature and the particle size, the use of dispersant and type of dispersion assist mechanism used for the preparation [14][15][16].…”