Experimental Investigations of Thermophysical Properties and Convective Heat Transfer of Al2O3 and CuO Nanofluids in a Copper Tube: Proposing New Correlations

Abstract

The performance of the Alumina/water and copper oxide/water nanofluids in a heat exchanger is experimentally investigated for particle weight concentrations ranging from 0.02 wt% to 0.5 wt%. The alumina/water and copper oxide/water nanofluids were prepared using two-step methods in an aqueous solution with 0.01 wt% CTAB (Cetyl Trimethyl Ammonium Bromide) as a surfactant at different concentrations and were characterized using HRTEM (High-Resolution Transmission Electron Microscopy) technique. Laminar forced convective heat transfer analysis using alumina and copper oxide nanoparticles suspended in water in a circular horizontal tube under constant heat flux boundary conditions was performed. The effect of various flow conditions and weight concentrations in the local heat transfer coefficient and pressure drop of both the nanofluids were investigated. Reynolds number varied from 1275 to 2200. Results show that 12.7 & 14.5 % thermal performance enhancement was observed with 0.5 wt% of Al2O3 and CuO nanofluids. Maximum, 50.62 % enhancement was observed in the average heat transfer coefficient by Al2O3 nanofluids, whereas 52.74 % was observed using CuO nanofluids using 0.5 wt% concentrations of the nanofluids and at Reynolds number of 2200. Correlations were proposed for thermal conductivity, viscosity, and Nusselt number for both the nanofluids with the maximum and minimum deviations of ±9 % and ±10 %, respectively.