We have experimentally investigated the behaviour and heat transfer enhancement of a particular nanofluid, Al2O3 nanoparticle–water mixture, flowing inside a closed system that is destined for cooling of microprocessors or other electronic components. Experimental data, obtained for turbulent flow regime, have clearly shown that the inclusion of nanoparticles into distilled water has produced a considerable enhancement of the cooling block convective heat transfer coefficient. For a particular nanofluid with 6.8% particle volume concentration, heat transfer coefficient has been found to increase as much as 40% compared to that of the base fluid. It has also been found that an increase of particle concentration has produced a clear decrease of the heated component temperature. Experimental data have clearly shown that nanofluid with 36 nm particle diameter provides higher heat transfer coefficients than the ones of nanofluid with 47 nm particle size.
"A considerable research has been found in the literature to understand the heat transfer enhancement using different water based nanofluids; however most of these studies are limited to either pool boiling or cooling of low temperature substrates [13e19]. For example, Nguyen et al.  investigated the heat transfer potential of watereAl 2 O 3 nanofluid for an electronic liquid cooling system. It has been found that addition of nanoparticles increases the heat transfer coefficient of water by 40%. "
[Show abstract][Hide abstract] ABSTRACT: Keywords: Air-assisted atomizer Heat transfer enhancement Nanofluid Run-out table application Spray evaporative cooling a b s t r a c t The study deals with the air-atomized spray cooling using nanofluid as the cooling media for high heat flux applications. The nanofluid has been prepared by commercial Al 2 O 3 particles of diameter less than 13 nm and water. Heat transfer study has been carried out on a pre-heated steel specimen of dimensions 100 mm Â 100 mm Â 6 mm. The initial temperature of the plate which was subjected to air-atomized spray cooling was over 900 C. Various coolants consisting of 0.1% volumetric concentration of water eAl 2 O 3 mixture, with or without a dispersing agent (surfactant) were used for the study. The dispersing agents used are sodium dodecyl sulphate (SDS) and polyoxyethylene (20) sorbitan monolaurate (Tween 20). Inverse heat conduction software INTEMP has been used for estimating the surface heat flux and temperatures taking into account the measured internal temperature histories by the thermocouples during the cooling process. The results obtained using nanofluid coolants are compared with that of the results where pure water (filtered potable water) is used as a coolant. The analyses reveal that the cooling rate, critical heat flux and heat transfer coefficients are significantly enhanced when nanofluids are used as coolants in air-atomized spray process. Also, the nanofluid coolants with dispersing agent shows a better enhancement of heat transfer over that of the nanofluid without the dispersing media. The nanofluid with dispersing agent Tween 20 is found more effective than that of its counterpart. Overall, the percentage enhancement in cooling rate of all these nanofluids compared with pure water (filtered potable water) is 10.2% for watereAl 2 O 3 , 18.6% for watereAl 2 O 3 eSDS, and upto 32.3% for watereAl 2 O 3 eTween 20.
International Journal of Thermal Sciences 10/2015; 96:85-93. DOI:10.1016/j.ijthermalsci.2015.04.012 · 2.63 Impact Factor
"They found that the heat transfer coefficient increased with volume fraction of TiO₂. Nguyen et al.  conducted experimentally the behaviour of heat transfer characteristics of Al₂O₃/water nanofluids for an electronic application as a cooling system. They observed the heat transfer coefficient with a certain particle volume concentration remarkably increased compared to the base fluid. "
[Show abstract][Hide abstract] ABSTRACT: A numerical analysis has been implemented applying on turbulent forced convection flow of water inside a horizontal circular channel with a constant heatflux applied to the wall. Nusselt number and friction factor have been tested for Reynolds number, Re= 5000to 20000. Results present that the heat transfer rate increases as the Reynolds number increase. On the other hand, the friction factor increase when the Reynolds number decrease. Finally, results of the average Nusselt number and frictional factor for pure fluid (water) have been verified and validated with experimental results as well as with available correlations where a logical good agreement has been fulfilled.
"e l s e v i e r . c o m / l o c a t e / e t f s et al.  performed experiments for Al 2 O 3 /water nanofluid in radiator type heat exchanger and observed 40% heat transfer enhancement for a volume concentration of 6.8%. Wen and Ding  conducted Al 2 O 3 /water nanofluid heat transfer experiments under constant wall heat flux for laminar flow conditions. "
[Show abstract][Hide abstract] ABSTRACT: Turbulent forced convection heat transfer and friction of Al2O3–water nanofluid flowing through a concentric tube U-bend heat exchanger with and without helical tape inserts in the inner tube were studied experimentally. The experiments were conducted in the Reynolds number range from 3000 to 30,000, volume concentrations of 0.01%, 0.03% and helical tape inserts of p/d = 5, 10, 15 and 20. The results indicate that an increase in Reynolds number and Prandtl number yields to an increase in the average Nusselt number, and augmentation of thermal conductivity in the nanofluid contributes to heat transfer enhancement. The Nusselt number of entire pipes for 0.03% concentrations of nanofluid with helical tape inserts of p/d = 5 shows an enhancement of 32.91%, as compared to water. The friction factor for the entire inner tube for 0.03% concentration of nanofluid with helical tape inserts of p/d = 5 has increased by 1.38-times, as compared to water; in general and consistent with theory, the pressure drop in the inner tube increases with an increase in nanoparticle volume concentration and aspect ratio of the inserts. The empirical correlations for the Nusselt number and friction factor are obtained as functions of the Reynolds number, Prandtl number, volume concentration and aspect ratio.
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