Thermal and Fluid Dynamics Performance of MWCNT-Water Nanofluid Based on Thermophysical Properties: An Experimental and Theoretical Study

Abstract

There are many debates on the preparation methods and the role of ultrasonication on the stability, thermophysical properties, and heat transfer performance of nanofluids. The present study, which is the continuation of the authors previous study, the effects of ultrasonication on the thermal and fluid dynamic performance of MWCNT-water nanofluid, over a different range of temperatures and solid concentrations, based on the thermophysical properties of the nanofluid, has been investigated. The effects of ultrasonication time on the stability and thermophysical properties of the nanofluid were studied over 30 days of the samples preparation. The thermophysical properties of the nanofluid have been experimentally measured at the optimum ultrasonication time. Using the experimental data, and employing different figures-of-merit, the effects that the addition of MWCNTs had on the heat transfer effectiveness and pumping power have been studied. It was confirmed that the nanofluid is a good heat transfer fluid, with a negligible penalty in pumping power. The thermal and fluid dynamic performance of the nanofluid in a microchannel heat sink has also been studied, by comparing the enhancement ratio of the convective heat transfer coefficient and the increase in pumping power.

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

“…An increase in concentration was found to increase this viscosity. In Figure 32 , the measurements for the thermal conductivity and viscosity of water-based MWCNT–Fe 3 O 4 nanofluids [ 71 ] are compared to Fe 3 O 4 –water nanofluid thermal conductivity measurements [ 6 ], Fe 3 O 4 –water viscosity measurements [ 15 ], and MWCNT–water thermal conductivity and viscosity measurements [ 72 ], with all nanofluids at a concentration of 0.1% volume. It can be seen that across the range of temperatures, the MWCNT–Fe 3 O 4 hybrid nanofluid has the highest thermal conductivity until about 60 °C.…”

“… Thermal conductivity (increasing with temperature) and viscosity (decreasing with temperature) Fe 3 O 4 –MWCNT hybrid nanofluid, MWCNT and Fe 3 O 4 with water as a base fluid at a volume of 0.1% [ 6 , 15 , 71 , 72 ]. …”

“… Timofeeva et al [ 67 ] (2009) Nanoparticle Characteristics: AlO (OH) Platelets 9 nm, cylinders 80 × 10 nm, blades 60 × 10 nm, and bricks 40 nm. Base liquid: Water Range of concentration: 1–7% vol Range of temperature: 15–85 °C Platelet shaped nanoparticles within a nanofluid have a higher viscosity than cylindrical, blade and bricklike shaped nanoparticles within a nanofluid Xing et al [ 68 ] (2015) Nanoparticle Characteristics: Carbon nanotubes (MWCNT) with S-SWNT and L-SWNT Base liquid: Water Surfactant: CTAB Range of concentration: 0.05–0.48% vol Range of temperature: 10–60 °C Thermal conductivity increases with an increase in concentration and temperature Highest thermal conductivity in L-SWNT followed by S-SWNT the MWNT Higher aspect ratio in carbon nanotubes leads to higher thermal conductivity Sundar et al [ 71 ] (2014) Nanoparticle Characteristics: Hybrid made of multiwall carbon nanotube (MWCNT) and Fe 3 O 4 Base liquid: Water Range of concentration: 0.1–0.3% vol Range of temperature: 20–60 °C Thermal conductivity increases as concentration and temperature increase Viscosity decrease as temperature increase Viscosity increase as concentration increases Lyu et al [ 72 ] (2020) Nanoparticle Characteristics: MWCNT, 7 nm Base liquid: water Range of concentration: 0.1–0.5% vol Range of temperature: 25–60 °C Thermal conductivity increases as temperature and concentration increases As temperature increases viscosity decreases As concentration increases viscosity increases Sundar et al [ 73 ] (2016) Nanoparticle Characteristics: Hybrid made up of Nanodiamond (ND) and Fe 3 O 4 Base liquid: Water, Water-EG Range of concentration: 0.05–0.20% vol Range of temperature: 20–60 °C ND–Fe 3 ...…”

A review of passive methods in microchannel heat sink application through advanced geometric structure and nanofluids: Current advancements and challenges

“…The nozzle effect generated by the rib geometry near the cavity area can reduce the residence time of fluid in the cavity area. Besides that, vortex flow induced by the rib geometry because of adverse pressure gradient can change the flow structure of fluid at the nearest cavity area, where the increase in the degree of flow mixing can contribute to the enhancement of heat transfer performance Some criteria need to be considered during the preparation of nanofluid, which include base fluid selection, size, shape, concentration, purity, dispersibility, thermal conductivity, preparation method (dispersion technique and sonication time [121,122]), and compatibility of nanoparticles that ensure the homogeneity of nanofluid [123]. Table 3 shows some types of nanoparticles that have been used in the MCHS application in the previous studies [124][125][126][127][128][129][130][131][132][133][134][135][136] It can be observed that most of the researchers were interested in Al 2 O 3 nanoparticle as an additive in a base fluid for the MCHS application.…”

Effects of ultrasonication time on stability, dynamic viscosity, and pumping power management of MWCNT-water nanofluid: an experimental study

“…There is no denying the fact that introducing nanofluids (NFs), which are suspensions of nano-sized particles into the conventional working fluids, by Choi and Eastman 1 in 1995 has opened new doors to improve the heat transfer performance in different applications. After this pioneering study by Choi and Eastman 1 , many researchers investigated the stability and thermophysical properties [2][3][4] , heat transfer [5][6][7][8][9][10][11] , applications of artificial intelligence in predicting the thermophysical properties of nanofluids [12][13][14][15][16] , and applications of various NFs [17][18][19][20][21] . It is known that thermophysical properties of each fluid play an important role in heat transfer performance of the fluids: viscosity directly affected the pumping power and the pressure loss, thermal conductivity indicates the heat transfer effectiveness of the fluid, and specific heat capacity shows the capability of the fluid in storing and moving heat away.…”