Cho, Kyu T.
M.S. (Master of Science)
Department of Mechanical Engineering
Mechanical engineering; Nanofluids--Experiments; Heat--Transmission--Research; Energy transfer--Research; Fluid dynamics--Research
Systematic approach was used to investigate the physical, rheological, and thermal behavior of Nanofluids with special emphasis on the impact of stabilizing additives used to stabilize Nanoparticles suspension in base fluid. Three different additives, Sodium hexametaphosphate, Diammonium hydrogen citrate, and Triammonium citrate were used in three different sets of experiments (water, water and additive solution, and water, additive, and nanoparticles mixture). Viscosity as a rheological property was measured. Experimental data showed that viscosity of Nanofluids was influenced by the type of additive used. All additives showed an increase in viscosity when they were added in water. The largest increase in viscosity was measured when Sodium hexametaphosphate was used in concentration of 1% by mass, the increase in viscosity was a little over 3%. All viscosity measurements were made by assuming the test fluids to be Newtonian, since the used concentrations of nanoparticles and additives were small. In light of experimental data, the heat transfer coefficient decreased (in comparison to water) with the use of two additives, while no significant decrease in heat transfer was measured when Diammonium hydrogen citrate was used in concentration of 0.1% by mass. All heat transfer tests were conducted in thermally developing laminar flow. In general, for the given flow conditions, heat transfer coefficient of water and additive solution was decreased when CuO nanoparticles were introduced. Decrease was observed to be reducing along the length of the test tube. Some possible improvements were seen with higher concentrations of nanoparticles (5% by mass). Based on the experimental data, it seems that with low concentrations of nanoparticles there could be some entry regions, under some flow conditions, where heat transfer coefficient may reduce. Changes in thermo-physical properties by the use of small concentrations of nanoparticles might be causing these results, or it may also be attributed to any unknown phenomenon associated with Nanofluids. Further experiments are suggested in the future work to help understand this reduction of heat transfer.;Zeta potential measurements were made in order to quantify the stability of the prepared Nanofluids. Stability of the fluids was also visually confirmed, and it seems to agree with the measured values of zeta potential. Measurement of the particle size in Nanofluids shows that relatively smaller particle size was observed in fluids that were more stable (high values of zeta potential) as compared with fluids that were less stable. This result was expected, as with the case of less stable Nanofluids more particles will tend to stick with each other, resulting in higher average particle size. The impact of stability on the particle size further increases the importance of having more stable Nanofluids.;Nanofluid flow and heat transfer apparatus developed by Netemeyer for his Master's thesis at Northern Illinois University was used to study the flow and heat transfer characteristics of test fluids with few modifications, while Malvern Zetasizer equipment was used to measure the zeta potential and size of nanoparticles suspended in Nanofluids.
Khan, Hassan Ahmed, "Experimental study of flow and heat transfer characteristics of nanofluids in a tube flow" (2015). Graduate Research Theses & Dissertations. 3007.
Northern Illinois University
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