Natural convection of CNT water-based nanofluids in a differentially heated square cavity

Abstract

International audienceThe present paper deals with the prediction of average Nusselt number in a differentially heated square cavity filled with Newtonian and non-Newtonian CNT nanofluids. Based on thermophysical properties which were experimentally evaluated, available correlations are used for estimating the Nusselt number and heat transfer coefficient of natural convection of CNT nanofluids with volume fractions in a range of 0.0055 to 0.418 %. The effects of surfactant, average temperature of nanofluids within the cavity, driving temperature of cavity walls on Nusselt number are investigated and discussed. A peculiar attention is devoted to the non-Newtonian nature of CNT nanofluids in the analysis. It is found in particular that Nusselt number of nanofluids is lowered by nanoparticle content increase related to Non-Newtonian behaviour of nanofluids and temperature increase

Influence of defects induced by chemical treatment on the electrical and thermal conductivity of nanofluids containing carboxyl-functionalized multi-walled carbon nanotubes

“…[1][2][3] Among these potential applications, using CNTs as heat transfer media in high thermal conductivity nanouids for cooling systems is one of the most promising and interesting applications due to their high thermal conductivity, high electrical conductivity and low density. [4][5][6][7][8][9][10][11] The problem here is it is challenging to disperse CNTs in solvents directly for preparing nanouids due to their high hydrophobicity in as-grown states and CNTs normally tend to aggregate together to form bundles or clusters due to van der Waals interactions. As presented in many reports, maintaining uniform dispersion and stability of CNT nanouids is a key point to obtain the optimal thermal properties for a long time.…”

“…25 The properties of CNTs based nanouids such as the thermal conductivity, heat transfer, electrical conductivity, viscosity, stability have been investigated and reported. 5,[8][9][10][26][27][28][29][30][31][32][33][34][35][36] Many works have been proposed and mainly focused on the thermal property both in the experimental and the theoretical models due to high thermal conductivity of CNTs compared to other materials and high potential applications. [26][27][28][29][30][31][32][33] These works have almost been done to investigate the effect of the parameters such as CNT structure, CNT concentration, temperature, pH, surfactants, ultrasonic power, ultrasonication time on this property.…”

Numerical study on CNT nanofluids behavior in laminar pipe flow

“…Nanofluids considered here were previously investigated, more information about their preparation and stability, average dimension and properties of nanotubes can be found in [17][18][19][20]. Here, only important details and results are given.…”

“…Labels used to differentiate each fluid over the numerical study Table 2 Thermophysical properties of studied fluids: data extracted from [17][18][19][20] Table 3. Rheological behavior of studied CNT nanofluids [17,18,20] Table 4. Viscosity estimation (consistency and power law indexes) of studied non-Newtonian fluids [17,18,20] Table 3.…”

“…Viscosity estimation (consistency and power law indexes) of studied non-Newtonian fluids [17,18,20] Table 3. Rheological behavior of studied CNT nanofluids [17,18,20] Code flow type, extracted from [17,18,20] N1 newtonian N2 non-newtonian N3 non-newtonian Table 4. Viscosity estimation (consistency and power law indexes) of studied non-Newtonian fluids [17,18,20]…”