Investigation of Rheological Behaviour and Heat Transfer Performance of Alumina Nanofluid

Abstract

In this work, Al 2 O 3 Nanoparticles with mean diameter of 25nm, surface area 180m 2 /g dispersed in base fluid using two step method with the nanoparticles volume concentrations 0.1%, 0.2%, 0.3%, 0.4% and 0.5% using magnetic stirrer and sonicator. Two different base fluids were used, Distilled Water (DW) and Distilled Water:Ethylene Glycol (EG) mixture (70:30%, 80:20% & 90:10%). 40 samples were prepared with the four base fluids with and without capping agent (Cetyltrimethyl Ammonium Bromide-CTAB). First part of the work is Rheological investigation of all samples. Thermal conductivity, viscosity and density were measured. Obtained values were compared in three ways, Nanofluids with and without capping agent, Nanofluids with different percentages of ethylene glycol and without ethylene glycol. It was observed that capping agent plays a vital role in keeping good stability of nanofluids and in the case of Water:Ethylene glycol base fluid, capping agent is very useful to reduce the agglomeration of nanoparticles and in turn increases thermal conductivity. Decreasing ethylene glycol percentage in base fluid increases the thermal conductivity. Second part of the work is the experimental investigation of heat transfer performance of nanofluids on double pipe counter flow heat exchanger. Results show that with the increasing nanoparticle concentration in nanofluids heat transfer coefficient increases. Heat transfer augmentation at 0.5% volume concentration of Al 2 O 3 is higher than the other volume concentrations.

Entropy Analysis of a Convective Film Flow of a Power-Law Fluid with Nanoparticles Along an Inclined Plate

“…into the boundary layer region) whereas the opposite behaviour is noticed for temperature gradients associated with the Nusselt number. However as with the skin friction, there is a depletion in the nano-particle concentration gradient with progress into the boundary layer transverse to the wall and this verifies the earlier results described relating to greater Sherwood numbers always being computed at the wall, associated with the agglomeration of nano-particles (although the effect is somewhat weaker for pseudo-plastic nanofluids compared with dilatant nanofluids, as noted in [22,52,53]).…”

“…achieve enhanced heat transfer rates at the wall and this has also been corroborated by experiments reported in Raghulnath et al[52] and Akhavan-Behabadi et al[53] for metallic nanofluids. This is surmised to be a result of larger concentrations of nano-particles associated with smaller sized-nanoparticles (higher Brownian motion number).…”

Study of Heat Transfer of Aluminium Oxide Nanofluids using Aluminium Split Flow Microchannels

“…A foretaste of nanofluidic thermal conductivity can be seen in reviews by Murshed et al [13], Das and Choi [14]. Another thermophysical property viscosity has also attracted the researchers [7,[15][16][17].It is seen from these investigations and reviews that the viscosity increases with increase in concentration of nanofluids and decreases with decrease with increase in temperature as concluded by Saini et al [3] in his review. So this was the one of the method enlisted above to increase the heat dissipation from the small spaces.…”

“…Due to the better thermophysical properties of nanofluids they are preferred over the base fluids. Thermal conductivity is the most studied property of nanofluids as can be seen from the available literature [5][6][7][8][9][10][11][12]. From the literature available it can be concluded that thermal conductivity of nanofluids increases with increase in concentration of nanoparticles in base fluids, also the thermal conductivity increases with increase in temperature.…”