Investigation On The Thermal And Electrical Conductivity Of Spherical Nanofluids

Due to the rapid development of cooling technology, the new type of refrigeration and the requirement of increasing the working medium. In high in thermal efficiency of the refrigerating agent, high heat conductivity of nanofluids can received widespread attention. Purpose of this paper is in-depth study of spherical nanometer fluid thermal and electrical properties, and from the mechanism analysis on its performance enhancements. Spherical ZnO nanoparticles with uniform size were synthesized by a hydrothermal method. By using pretreatment method we produced Al2O3nanoparticle. These nanoparticles were then dispersed into water by ultrasonic vibrating to form a stable nanofluids. The electrical conductivity of water-based ZnO nanofluids and water-based Al2O3with variety of temperature and volumetric fraction were investigated. The volumetric-fraction-dependent thermal conductivity was also measured at room temperature. Experiments indicate that the electrical conductivity of ZnO nanofluids reveals a non-linear relationship versus volumetric fraction and the electrical conductivity of Al2O3nanofluids reveals a linear relationship. However, it presents a quasi linear relationship versus temperature for both of them. The thermal conductivity is enhanced with volumetric fraction in an approximate linear relationship. Moreover, a modified model was established based on Maxwell thermal conductivity model and Brownian dynamics theory by considering boundary adsorption layer, aggregation and Brownian motion of nanoparticles in the fluid. The expected thermal conductivity values based on the modified model is in good agreement with our experiment data, suggesting our modified model might be more accurately adapted to the nanofluids thermal conductivity. However, this paper investigated the boundary adsorption layer by using molecular simulation method.