Experimental Investigation of Nano-Fluid Characteristics and Behavior of Aluminum Oxide Nano-Particles Dispersed in Ethylene Glycol-Water Mixture

Abstract

The need for improved efficiency of automotive thermal management system is driven by the trend that the automotive powertrain system operates towards higher power output with smaller system size. In other words, the intensified heat dissipation loads from the powertrain system need more efficient cooling solutions. One effort is to enhance the thermal performance of the conventional automotive heat transfer fluid, typically ethylene glycol/water mixture, due to its intrinsically poor thermal property. Nano-fluids have been synonymous with the nanotechnology-based advanced cooling fluids which are derived by homogeneously dispersing nanometer-sized particles into conventional heat transfer fluids. In this study, a multi-parameter approach is used to investigate the behavior of the Aluminum Oxide (Al2O3) nano-particle based nano-fluids. The nano-particles are dispersed in 50/50 vol.% ethylene glycol/distilled water mixture and the other two base fluids (distilled water and ethylene glycol). Two-step method is used for the nano-fluid sample preparation. Nano-fluid sample is characterized by TEM imaging, particle surface charge, particle sizing, light absorbance and pH. Nano-fluid thermal properties are investigated by measuring the thermal conductivity and viscosity at different temperatures. The nano-particle sedimentation within the nano-fluid is determined. The aging effect on the nano-fluid thermal properties is studied. The results offer multiple-perspective correlations between the nano-fluid characterization and performance.

xiv

Further, the experimental investigation is conducted to evaluate the forced convection heat transfer coefficient of Al2O3 based nano-fluids in the Reynolds number range of 3000 to 4000. The different nano-particle concentrations are tested. The heat transfer test section is basically a concentric double pipe heat exchanger. The inside pipe is designed to simulate a vehicle radiator tube flow condition, where the heated nano-fluid is circulating. The outside pipe is used for circulating the cooling water. The nano-fluid temperature at the inlet of the test section is kept at 60°C ±5°C. The result develops the correlation between nano-fluid convection heat transfer coefficient and Reynolds number as a function of nano-particle concentration.