Experimental investigation on the thermal performance of compact heat exchanger and the rheological properties of low concentration mono and hybrid nanofluids containing Al2O3 and CuO nanoparticles

The present work focused on preparing and studying the fluid and thermal properties such as density, viscosity, specific heat capacity and thermal conductivity of low concentration hybrid nanofluids. The present work also focused on comparing these properties and the thermal enhancements with other low concentration mono nanofluids. The nanofluids used for present work are Al2O3-CuO, Al2O3 and CuO combined with a 60:40 mixing ratio of distilled water and ethylene glycol acting as the base fluid. The volume concentration at which the nanofluids are prepared are fixed 0.02%, 0.04% and 0.06%. The findings show that the thermal conductivity of the hybrid samples is higher compare to its mono counterparts. The thermal conductivity of Al2O3-CuO showed enhancements by 2.3% when compared to CuO and by 3.6% when compared to Al2O3. By using the prepared samples as a working fluid in a compact fin and tube heat exchanger test rig, an experimental investigation is conducted. This is to observe any form of improvements in terms of heat transfer by comparing the experimental results of the hybrid nanofluids with its respective mono counterparts. Based on the experiments conducted, it is found that the use of Al2O3-CuO hybrid nanofluids as a working fluid in a compact heat exchanger test rig showed an increase in both Nusselt number and average heat transfer coefficients by 6.7% and 7.2% respectively when compared to CuO nanofluids and by 17.9% and 12.1% respectively when compared to Al2O3 nanofluids.