مهندسی مکانیک شریف (Nov 2020)
EXPERIMENTAL STUDY OF THE EFFECT OF SURFACE TYPE ON THE POOL BOILING HEAT TRANSFER CHARACTERISTICS IN THE PRESENCE OF NANOFLUIDS WITH HYBRID BASE FLUID
Abstract
The purpose of this study is to investigate the effect of microstructured surface of brass and its morphology change due to the deposition of nanofluids with hybrid base fluid in the pool boiling process on heat transfer characteristics. Pool boiling experiments were carried out with four groups of base fluid: pure deionized water, 70\% water - 30\% ethylene glycol, 50\% water - 50\% ethylene glycol, and 30\% water-70\% ethylene glycol. In addition, nanofluids are made of OH-based multiwall carbon nanotubes with base fluids listed in two volumetric percentages of 0.025\% and 0.1\%. To the combination of nanofluids used in all experiments was added Sodium Dodecyl Sulfate (SDS) as a homogenizer. In the hybrid fluid pool boiling experiments on the microstructured surface, with increasing ethylene glycol concentration, the critical heat flux and heat transfer coefficient decreased and the highest increase in these two parameters was related to deionized water boiling on the microstructured surface, which was 290.3\% and 302.1\% respectively, compared to the boiling of deionized water on the polished surface. In pool boiling experiments on the microstructured surface in the presence of nanofluids with hybrid base fluids, the critical heat flux and heat transfer coefficient increased with increasing nanofluid concentration and the highest increase in these two parameters was related to deionized water base nanofluid boiling at a volumetric concentration of 0.1\%, which was 74.9\% and 91.8\%, respectively, compared to the boiling of deionized water on the microstructured surface. On the deposited microstructured surface by nanoparticles, most changes in critical heat flux and heat transfer coefficient were related to deionized water base nanofluid boiling at a volumetric concentration of 0.1\%, which was increased by 18.98\% and decreased by 48.6\%, respectively, compared to the boiling of deionized water on the microstructured surface without deposition. In the all hybrid fluid pool boiling experiments, with an increase in the ethylene glycol concentration, critical heat flux and heat transfer coefficient decreased.
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