646 / 2019-03-28 20:04:06

An experimental study on the thermal conductivity and viscosity of CuO-ZnO hybrid nanofluids in Ethylene glycol (EG) and water (W) mixture

Key words: viscosity; thermal conductivity; CuO-ZnO hybrid nanofluids; mixture ratio; correlation

全体主题 > 纳米传热、纳米流体流动和纳米材料

Abstract: This research investigates the effects of base fluid mixture ratio (EG: W) and temperature on viscosity and thermal conductivity of CuO-ZnO hybrid nanofluids. The CuO and ZnO nanoparticles with 50:50 (by weight) suspended in different base fluids mixture ratio such as 20:80, 40:60, 50:50, 60:40 and 80:20 by weight of EG and W mixtures are investigated. A two-step method is used to prepare CuO-ZnO hybrid nanofluids with a mass fraction of 1 wt. % without any surfactant. The measurement of thermal conductivity and viscosity for CuO-ZnO hybrid nanofluids are performed in temperature between 25oC and 60oC. The results indicate that viscosity of hybrid nanofluids decreases with increment of temperature and mixture ratio of water. As temperature is increased, thermal conductivity enhancement (TCE) of hybrid nanofluids increases at all mixture ratios (EG: W). However, the thermal conductivity enhancement (TCE) of hybrid nanofluids decreases significantly with increasing mixture ratio of EG. The maximum augmentation of thermal conductivity is 21.5% at the temperature of 60 oC with a ratio of 20:80 among all the hybrid nanofluids. Meanwhile, the maximum viscosity ratio is observed for 60:40 hybrid nanofluids about 1.2 times at temperature of 25 oC. The properties enhancement ratio (PER) indicates that CuO-ZnO hybrid nanofluids will lead to higher heat transfer performance for all mixture ratios as compared to base fluids. An empirical correlation for viscosity and thermal conductivity of CuO-ZnO hybrid nanofluids are developed with purpose of modeling the experimental data. Proposed correlations can accuracy predict the viscosity and thermal conductivity of CuO-ZnO hybrid nanofluids and R-squared of these models are 0.9885 and 0.9935, respectively.