Experimental investigation of thermal conductivity behavior of MWCNTS-Al2O3/ethylene glycol hybrid Nanofluid: providing new thermal conductivity correlation

The present study investigates the thermal conductivity of Al2O3 hybrid with MWCNTs (multi-walled carbon nanotubes) nanoparticles dispersed in ethylene glycol (EG) as a base fluid. Seven different nanoparticles volume fractions, namely, 0.02%, 0.04%, 0.08%, 0.1%, 0.25%, 0.5% and 0.8% at temperatures ranging from 25 degrees C to 50 degrees C of the hybrid nanofluid are prepared without using any surfactant. Transient Hot Wire method (THM) using KD2 Pro device (Decagon Devices, Inc., USA) was used to measure the thermal conductivity of the nanofluids. The results show at most about 17% thermal conductivity enhancement for 0.8% nanoparticles volume fraction at 50 degrees C. Two new correlations are proposed to estimate the hybrid nanofluid thermal conductivity with high accuracy. The first one is a function of the nanofluid temperature and its volume fraction and the next one, with a higher accuracy, is in effect six expressions in terms of the nanoparticles volume fraction presented at temperatures 25 degrees C, 30 degrees C, 35 degrees C, 40 degrees C, 45 degrees C and 50 degrees C.