Specific heat measurements of five different propylene glycol based nanofluids and development of a new correlation

This paper presents the specific heat measurements of five different nanofluids containing aluminum oxide (Al2O3), zinc oxide (ZnO), copper oxide (CuO), titanium oxide (TiO2) and silicon dioxide (SiO2) nanoparticles dispersed in a base fluid of 60% propylene glycol and 40% water by mass (60:40 PG/W). The measurements were carried out over a temperature range of −30 to 90 °C, for nanoparticle volumetric concentrations of 0.5% to 6% and for average particle sizes ranging from 15 to 76 nm to evaluate their effects on the specific heat. From comparison, it was found that the existing specific heat correlations were not able to predict the measured experimental values. Therefore, a new correlation was developed to predict the specific heat of measured nanofluids. This new correlation is in good agreement with 610 experimental data points of the five nanofluids with a maximum deviation of −5% exhibited by the Al2O3 nanofluid and an average deviation of −0.094%, considering all five nanofluids.