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Öğe An Experimental Study on SiO2-ND Hybrid Nanofluid: Thermal Conductivity, Viscosity, and Stability with New Forecast Models(Bentham Science Publ Ltd, 2022) Yalcin, Gokberk; Oztuna, Semiha; Dalkilic, Ahmet Selim; Nakkaew, Santiphap; Wongwises, SomchaiObjective: In the present investigation, thermal conductivity and viscosity properties of water-based SiO2-ND hybrid nanofluid were measured, experimentally. Methods: Nanofluids were prepared by using a two-step method and with three different (0.5%, 0.75%, and 1%) concentrations. Every concentration had three different SiO2-ND mixtures (50% SiO2 - 50% ND, 33% SiO2 - 66% ND, 66% SiO2 - 33% ND). Results: The most stable sample was measured as -33.4 mV. Measurements of viscosity and thermal conductivity were done from 20oC to 60oC at every 10oC. Thermal conductivity data were measured by thermal conductivity analyzer and viscosity data were measured by tube viscometer. The highest thermal conductivity enhancement was measured for 1% SiO2 (0.33): ND (0.66) at 40oC and the highest relative dynamic viscosity was calculated as 4.19 for 1% SiO2 (0.33): ND (0.66) at 40oC. A comparison table is also given to show the zeta potential values-concentration relations. Conclusion: Finally, two different correlations for predicting thermal conductivity and viscosity were proposed for practical usage.Öğe Experimental study on the thermal conductivity of water-based CNT-SiO2 hybrid nanofluids(Pergamon-Elsevier Science Ltd., 2018) Dalkilic, Ahmet Selim; Yalcin, Gokberk; Kucukyildirim, Bedri Onur; Oztuna, Semiha; Eker, Aysegul Akdogan; Jumpholkul, Chaiwat; Nakkaew, Santiphap; Wongwises, SomchaiThis experimental study includes measurement of thermal conductivity of distilled water-based CNT-SiO2 hybrid nanofluids. Nanofluids were prepared by using two-step method, 3 different concentrations and 4 different mass range of CNT-SiO2. SiO2 has 2200 kg m(-)(3) density, 1.4 W m(-1) K (-1) thermal conductivity and 7 nm average particle size. CNT has 2620 kg m(-3) density, 25 W m (-1) K(-1 )thermal conductivity and 6-10 nm average particle size. Samples were placed in ultrasonic homogenizer maximum power capacity for 3 h. Throughout sonication process temperature of nanofluids have been kept under control in order not to chance volumetric fraction of nanofluids. All measurements of thermal conductivity were done by using thermal conductivity meter. Thermal conductivity meter was calibrated by di-water. Measurements of thermal conductivity was done range from 25 degrees C to 60 degrees C for every 5 degrees C. Validation of measurements had been performed by using di-water and shown in a thermal conductivity-temperature figure. Minimum and maximum thermal conductivity enhancements were revealed in detail. Alteration of the thermal conductivity with temperature according to various volumetric fractions were in literature rated and it is found that the thermal conductivity increases with temperature and vol. fraction clearly. Enhancement on the thermal conductivity to di-water were also depicted for various temperatures and vol. fraction in figures. Almost well-known correlations in the literature were given with their predictable rates. Moreover, comparisons with other studies were provided in this present study. A practical correlation was proposed for other researchers.Öğe The influence of particle size on the viscosity of water based ZnO nanofluid(Elsevier, 2023) Yalcin, Gokberk; Oztuna, Semiha; Dalkilic, Ahmet Selim; Wongwises, SomchaiThis experimental work investigated, the effect of ZnO particles' size on the water-based nanofluid viscosity. Nanofluid samples with 0.5, 0.75, and 1% volume concentrations were prepared using 20 and 50 similar to 150 nm ZnO nanoparticle sizes. Their viscosity was determined at 20, 30, 40, 50, and 60 similar to C. Scanning electron microscopy was employed to investigate the morphology of the nanoparticles. The maximum relative viscosity was measured for 1% ZnO (50 similar to 150 nm) as 1.35 times water. The stability of samples was evaluated for 1% ZnO (20 nm) and 1% ZnO (50 similar to 150 nm) by measuring their Zeta potential values which were similar to 21.4 mV and -23.1 mV, respectively. The correlation for the dynamic viscosity using measured data was compared with wellknown ones. The offered correlation has R-2 = 0.988, R-adj(2) = 0.987, and +/- 5.58% maximum deviation. The results showed that 12.8% reduction in viscosity is possible by varying nanoparticle sizes. The current study proposes additional new findings on the nanofluids' usability. (C) 2022 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.Öğe Measurement of thermal conductivity and viscosity of ZnO-SiO2 hybrid nanofluids(Springer, 2022) Yalcin, Gokberk; Oztuna, Semiha; Dalkilic, Ahmet Selim; Wongwises, SomchaiPreparing and defining of thermal properties of new type hybrid nanofluids are essential to understand the fluidity mechanism of hybrid nanofluids and select suitable nanofluids in terms of application. This research aims to provide an alternative fluid for different applications and complete the new type of nanofluid necessity in the literature that has been reported by different research groups. In this current investigation, water-based ZnO-SiO2 hybrid nanofluid is prepared by using the two-step method, and thermal conductivity and dynamic viscosity values are experimentally specified. ZnO-SiO2 hybrid nanofluid has 0.5%, 0.75%, and 1% with 50% ZnO-50% SiO2; 33.3% ZnO-66.6% SiO2, and 66.6% ZnO-33.3% SiO2 nanoparticle mixtures. Thermal conductivity and dynamic viscosity are experimentally measured from 20 to 60 degrees C. Maximum thermal conductivity rising is 2.26%, and it is obtained for 1% ZnO0.66-SiO2(0.33) at 50 degrees C. Maximum dynamic viscosity increment is measured as 1.36 times of base fluid for 1% ZnO0.33-SiO2(0.66) at 50 degrees C. Changes in thermal properties are reasonable to use ZnO-SiO2 hybrid nanofluid in different thermal applications to increase system heat transfer rate and efficiency and reduce pressure drop and power consumption. Finally, two different regression equations are developed to predict the thermal conductivity and dynamic viscosity, respectively.
