Study of Heat Transfer in Microchannels Using Aluminum Oxide Nanofluids

Abstract

High performance heat exchanger devices with higher thermal conductivity of coolants are the need for micro industry, domestic and automobile industry. Thermal conductivity of coolants plays an important role in designing, selection, fabrication of high surface to volume ratio devices to extract higher heats from small spaces. Lower thermal conductivity of conventional fluids like water, ethylene glycol and oils has put a question on their credibility in small spaces high heat extraction devices. Nanofluids, suspensions have nano sized particles (upto 100nm) is seems to be promising solution of this problem. Furthermore, higher surface to volume ratio devices extract more heat than convention heat exchanging devices, microchannels stands by these constraints and proved a valuable asset for heat exchanger category. In the present study investigation of thermophysical properties of nanofluids and performance of microchannels have been carried out at different particle volume concentration ( 0.1%, 0.25%, 0.5% (vol.)) and with different flow rates ranging from 0.5ml/min to 2ml/min. the relation of thermal conductivity, viscosity has been investigated with concentration and temperature. Thermal conductivity increases and viscosity decreases with increase in temperature. Thermal conductivity and viscosity increases with increase in concentration of nanofluids. Heat transfer coefficient, Prandtl number, Reynolds number also studied for different concentrations and flow rates. It is seen that heat transfer coefficient and Prandtl number increases with increase in concentration of particles whereas Reynolds number decreases with increase in concentration. The heat transfer coefficient increased by maximum of 27% for 0.5% (vol.) concentration and Prandtl number increased by 22% maximum. However Reynolds number had decreased by maximum of 28% for 0.5ml/min flow rate and least decrease by 18% for 2ml/min flow rate. However, microchannels give the high surface to volume ratio of 8.05mm-1. This encourages the use of microchannels in small spaces where high heat transfer coefficients are required.