Experimental heat capacity of highly stable diamond/thermal oil nano-suspensions

The addition of nanoparticles into conventional fluids changes their thermophysical properties, such as thermal conductivity, viscosity, density, and specific heat capacity (SHC). While different nanofluids' thermal conductivity and viscosity are studied extensively, only a few experimental studies are subjected to SHC properties. It is important to investigate the SHC of nanofluids to understand their thermal aspects, particularly where the literature shows ambiguous results for the SHC of nanofluids. This study measures the SHC of diamond-based thermal oil nanofluids using differential scanning calorimeter (DSC) at varying nanoparticle concentrations of 0.25, 0.5, 0.75, and 1 wt% and a temperature range of 35-80 °C. The SHC of these nanofluids increased with temperature and decreased with an increase in nanoparticle concentration with a maximum SHC decrement of 8.25% at the highest 1 wt% concentration. The classical models are proved to underpredict the SHC of diamond-thermal oil nanofluids, as many nano-scale phenomena are not considered in these models. Therefore, a new multivariable correlation is also proposed for predicting the SHC of diamond-thermal oil nanofluids, exhibiting a good agreement with the experimental data with an R² of 96.35%.