Experimental investigation on the thermal performance and new correlation for thermal conductivity of aqueous copper oxide-doped MCM-41 nanofluids

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In the present study, the pure MCM-41- and CuO-doped MCM-41 nanoparticles with various mass fractions of CuO were synthesized and used for the preparation of water-based nanofluids. The obtained nanoparticles were characterized using small-angle X-ray scattering, scanning electron microscopy, transmission electron microscopy and N2 adsorption/desorption analysis. The thermal conductivity of the water-based nanofluids with various mass fractions of nanoparticles including 0.1, 0.5 and 1 mass% was measured by KD2-Pro thermal analyzer. A new correlation is developed for the thermal conductivity of the nanofluid with a reasonably good accuracy (± 5%) when comparing to the experimental data. The thermal performance of these nanofluids together with hydraulic features such as friction factor and heat transfer coefficient was investigated using a mini-channel heat exchanger. The obtained results revealed that the thermal conductivity can be enhanced by 13.1% which belonged to the nanofluid with 1 mass% of CuO-doped MCM-41 nanoparticles. The maximum heat transfer coefficient enhancement was 31% and belonged to the nanofluid containing 50% CuO@MCM-41 nanoparticles at 0.5 mass%. The performance evaluation criterion (PEC) of the various nanofluids was also calculated, and it was identified that the nanoparticles with 50% CuO@MCM-41 dispersed in water have the largest PEC, 16.7% over the base fluid. The friction factor increases by adding the nanoparticles to the pure water. For example, at Re = 1200, the friction factor increases about 36.84% by using the 50%CuO@MCM-41 nanoparticles with 0.5 mass% as compared with the pure water. The friction factor decreases with increasing the Reynolds number. For example, for 50%CuO@MCM-41 and 0.5 mass%, the friction factor decreases up to 34.17% as the Reynolds number increases in the range of 400–1200.