Eventos Anais de eventos
COBEM 2019
25th International Congress of Mechanical Engineering
CHARACTERIZATION OF HYBRID ZnO-Ag2O/WATER-ETHYLENE GLYCOL NANOFLUIDS FOR DIRECT PHOTOTHERMAL CONVERSION
Submission Author:
Carolina Beicker , MG
Co-Authors:
Carolina Beicker, Letícia Oliveira, ENIO PEDONE BANDARRA FILHO
Presenter: Letícia Oliveira
doi://10.26678/ABCM.COBEM2019.COB2019-1780
Abstract
The present work experimentally investigated the absorbance spectrum of hybrid ZnO-Ag2O/H2O-EG nanofluids and its thermal conductivity and viscosity for future use as photothermal conversion medium in a direct absorption solar collector (DASC). The hybrid nanoparticle was obtained by the method of coprecipitation, varying the Ag2O concentration, resulting in 11 different hybrid nanofluids samples. The XRD (X-Ray diffraction) technique was used in order to determinate nanoparticles crystalline structure and mean size. The nanofluids (0.5 wt% concentration) were prepared using a two-step method with the addition of nanoparticles (powder sample) in a mixture of water and ethylene-glycol (50:50) and the dispersion was obtained through ultrasonic vibration. Thermal conductivity and viscosity measurements were taken in the temperature range of 10ºC to 40ºC. The absorbance measurements showed that doping ZnO nanoparticles with Ag2O causes an absorbance increase for the nanofluids samples with doping silver concentrations between 0.1 and 3%, with decay for the samples doped with higher Ag2O concentrations. The thermal conductivity of the ZnO:5Ag sample presented an increase of 10% at 40°C and the temperature rise resulted in viscosity reduction for all samples. The study showed that hybrid ZnO-Ag/H2O-EG nanofluids could be great candidates for using as photothermal conversion medium since they have higher absorbance than pure Ag2O/H2O-EG and ZnO/H2O-EG nanofluids. The results also suggest that there is an optimal Ag2O concentration for doping ZnO nanoparticles for better results, and, for wavelengths between 600 and 800 nm, the doping process reaches the best absorbance with a concentration of 3 Ag%.
Keywords
Nanofluids, hybrid nanoparticles, characterization, optical properties, DASC
