Name: Felipe Costa Novo Malheiros
Type: MSc dissertation
Publication date: 08/11/2019

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Examining board:

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Bruno Venturini Loureiro Co advisor *
Rafael Sartim External Examiner *
Renato do Nascimento Siqueira Advisor *

Summary: As thermal systems consist of transporting a circulating fluid to perform heat transfer, methods and technologies that provide increased efficiency and cost reduction are constant challenges faced by engineers. Regarding transport (recirculation), the technique of adding small concentrations of surfactants in a fluid may be able to reduce energy consumption for this transport. Addition of nanoparticles to a fluid may be able to provide increased heat exchange efficiency. Knowing that nanofluids have the ability to increase heat transfer and that surfactant solutions can reduce energy consumption for fluid transport, experimental studies using Al2O3-water nanofluids, with and without the addition of CTAB surfactant were conducted to verify the possibility of increasing the convection heat transfer coefficient and the drag reduction effects. These experimental studies were conducted in a turbulent and constant heat flux experimental one to measure the friction factor and the convective heat transfer coefficient. The average size of the Al2O3 nanoparticles used was 13 nm. Nanofluid concentrations of 0.1% and 0.4% by mass were used, while CTAB concentrations were 200 ppm, 500 ppm and 700ppm. In this work it was possible to verify that the increase of nanoparticle concentration increased the heat transfer coefficient by 44%. The drag reduction capacity of surfactant solutions was also evaluated, which could achieve a reduction of up to 72%, but in turn reduced heat transfer effects by approximately 90%. In order to increase convective heat transfer in surfactant solutions, Al2O3 nanoparticles were added. Although there was an increase in heat transfer over surfactant solutions, it was not possible to achieve the same performance as nanofluids without surfactants. It was also found that in surfactant nanofluids that did not experience the drag reduction effects, the heat transfer coefficient showed significant values

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