جستجوی مقالات مرتبط با کلیدواژه « zno nanoparticles » در نشریات گروه « مواد و متالورژی »

An experimental study was carried out in order to find out the effects of ZnO Nano fluid with a mean diameter of 30nm on heat transfer, pressure drop and termal performance of a double tube heat exchanger, where the volume fraction of nanoparticles in the base fluid is less than 1% (low concentration). Ethylene glycol and Nano fluid with particle volume fraction of 0.5%, 0.7% and 1% are used as working fluid. The experiments are carried out in the fully developed turbulent regime. The results indicate that addition of low value of nanoparticles to the base fluid motivates the heat transfer to increase remarkably. The Nano fluid also show that the pressure drop of Nano fluid is slightly higher than that of the base fluid and does not increase with increasing the nanoparticles volume fraction. In this paper, experimental results have been compared with the existing correlations for Nano fluid convective heat transfer coefficient in turbulent regime. Also Nusselt number and friction factor were considered in definition of thermal performance factor for all cases are greater than unity which indicate that this Nano fluid enhances the heat transfer without huge penalty in pumping power. Thermal performance factor maximum is obtained 1.32% by 1% volume fraction and between 1.03%~1.20% by 0.5% volume fraction. Also, for Reynolds about 6300, nusselt number have increased by 0.7% volume fraction, about 19.8 percent. Hence, applying the methods studied here could be considered as a good choice in particle application.

In this research, Zinc oxide nanoparticles with semi-spherical morphology were synthesized by modified sol-gel method using rosemary extract as a stabilizing agent. The effect of the amount of rosemary extract and calcination temperature on size and shape of the particles was investigated. The samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and elemental analysis (EDX). X-ray diffraction results showed hexagonal structure (wurtzite phase) of zinc oxide. According to the SEM results semi-spherical nanoparticles of 18 nm in size were obtained using 75 ml of rosemary extract. The photocatalytic activity of the modified ZnO nanoparticles was investigated for degradation of the methylene blue dye solution. The results showed 96.87% of dye degradation in the 135 min that confirmed suitable efficiency of as-synthesized nanoparticles in the photocatalytic degradation process of dyes.