Browsing by Author "Shojaeian, M."

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The effect of nanoparticle type and nanoparticle mass fraction on heat transfer enhancement in pool boiling
(Elsevier, 2017-06) Karimzadehkhouei, M.; Shojaeian, M.; Şendur, K.; Mengüç, Mustafa Pınar; Koşar, A.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Determining the heat transfer performance with nanofluids is of cardinal importance in the utilization of nanofluids in thermal systems. This study presents an experimental investigation on nucleate pool boiling heat transfer of TiO2 nanoparticles/water and CuO nanoparticles/water nanofluids on a flat heater plate and aims to reveal the effect of mass fraction of nanoparticles in these nanofluids for attaining the maximum enhancement in pool boiling heat transfer. The effect of mass fraction on boiling heat transfer characteristics was studied for mass fractions varying from 0.001% to 0.2% for the heat flux range between 48.7 and 134.9 kW/m2. The experimental results showed that the heat transfer performance was improved when TiO2 nanoparticles were added to pure water, as base fluid. However, the amount of enhancement was highly dependent on mass fraction. It was realized that the lowest mass fraction (0.001%), namely the dilute TiO2 nanoparticles/water nanofluid, has the largest enhancement (around 15%). A further increase in mass fraction still augments heat transfer compared to pure water, however, the amount of enhancement decreased with mass fraction. Furthermore, the performed visualization showed that the addition of nanoparticles into the base fluid, increased the number of nucleation sites, and the bubbles had a more spherical shape along with a decrease in their size. For CuO/water nanofluids, heat transfer was enhanced at mass fractions larger than 0.001%. This enhancement could be more than 35% for the mass fraction of 0.2 wt.%. This study clearly indicates that the nanoparticle mass fraction corresponding to the best performance is highly dependent on the type of nanoparticle.
Open Access
Entropy generation analysis of laminar flows of water-based nanofluids in horizontal minitubes under constant heat flux conditions
(MDPI AG, 2018-04) Karimzadehkhouei, M.; Shojaeian, M.; Sadaghiani, A. K.; Şendur, K.; Mengüç, Mustafa Pınar; Koşar, A.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
During the last decade, second law analysis via entropy generation has become important in terms of entropy generation minimization (EGM), thermal engineering system design, irreversibility, and energy saving. In this study, heat transfer and entropy generation characteristics of flows of multi-walled carbon nanotube-based nanofluids were investigated in horizontal minitubes with outer and inner diameters of ~1067 and ~889 µm, respectively. Carbon nanotubes (CNTs) with outer diameter of 10–20 nm and length of 1–2 µm were used for nanofluid preparation, and water was considered as the base fluid. The entropy generation based on the experimental data, a significant parameter in thermal design system, was examined for CNTs/water nanofluids. The change in the entropy generation was only seen at low mass fractions (0.25 wt.% and 0.5 wt.%). Moreover, to have more insight on the entropy generation of nanofluids based on the experimental data, a further analysis was performed on Al2O3 and TiO2 nanoparticles/water nanofluids from the experimental database of the previous study of the authors. The corresponding results disclosed a remarkable increase in the entropy generation rate when Al2O3 and TiO2 nanoparticles were added to the base fluid.