Density and Specific Heat Capacity of 50:50 by Volume CuO–GO Hybrid Nanofluids in Water–Ethylene Glycol (60:40)

Abstract

The present study evaluates the density and specific heat capacity of a CuO–GO hybrid nanofluid dispersed in a water–ethylene glycol (W–EG) mixture with a 60:40 volume ratio. The CuO and GO nanoparticles were incorporated at a 50:50 ratio by volume. CuO nanoparticles with a density of 6300 kg m⁻³ and graphene oxide (GO) nanoparticles with a density of 1800 kg m⁻³ were considered. The total hybrid nanoparticle concentrations were 0.05, 0.10, 0.25 and 0.50 vol.%, and calculations were performed over a temperature range of 25–55 °C. The density of the hybrid nanofluid was determined using a mixture-based relation, while specific heat capacity was calculated using a density-weighted thermal-equilibrium relation. For a 50:50-by-volume CuO–GO mixture, the effective density was calculated as 4050 kg m⁻³, while the effective specific heat capacity was 0.5686 kJ kg⁻¹ K⁻¹ based on the constituent properties used in the present analysis. The predicted density decreased with increasing temperature and increased with increasing nanoparticle concentration. Conversely, specific heat capacity increased with temperature and decreased with nanoparticle concentration. At 0.50 vol.% and 55 °C, the predicted density was 1041.88 kg m⁻³, corresponding to an increase of approximately 1.47% relative to the base fluid, whereas the predicted specific heat capacity was 3.3979 kJ kg⁻¹ K⁻¹, corresponding to a reduction of approximately 1.62%. The results provide model-based information regarding the influence of temperature and hybrid nanoparticle concentration on the density and energy-storage characteristics of CuO–GO/W–EG hybrid nanofluids.