Abstract:
The study of Nanofluids is an emerging field in the 21st century. The notable
thermal properties of nanofluids have attracted the attention of researchers in
various scientific and engineering fields, such as mechanical, electrical, process,
automobile, biomedical engineering, and biotechnology. This research study
investigates the thermal properties of TiO2-based transformer oils with different
volume fractions from 0.002 to 0.012 vol.% and temperatures from 40 to 120 °C,
focusing on thermal conductivity and thermal diffusivity. The volumetric heat
capacity was calculated based on the values of thermal conductivity and thermal
diffusivity. Apart from the study of these properties, thermal conductivity results
were compared with three major theoretical models; the Maxwell model,
Maxwell and Garnett ‘s model, and the Pak and Cho model. Five different volume
fractions were considered for the study; 0 vol.%, 0.002 vol.%, 0.004 vol.%, 0.008
vol.%, 0.012 vol.%. Lower volume concentrations were selected to maintain the
stability of the nanofluid samples. Also, CTAB (Cetyltrimethylammonium
bromide) was used as a surfactant to enhance the stability of the nanofluid
samples. All the thermal properties were measured in accordance with the ASTM
D7896-19 standard using the LAMBDA multifunctional thermal conductivity
meter. The maximum thermal conductivity was achieved with the 0.012 vol.%
concentration at 40 °C as a 4.2% enhancement compared to the base oil.
According to the comparison of the experimental data with the theoretical data,
Maxwell and Garnett’s model displayed a minimum error, concluding that this
model is the most suitable one for predicting the thermal conductivity of TiO2/
Transformer Oil. The highest thermal diffusivity (81.156 × 10-3 mm2/s) was
achieved by the highest volume fraction at the minimum temperature (40 °C).
However, the highest volumetric heat capacity (1.52 × 106 J/m3.K), which was
calculated using thermal conductivity and thermal diffusivity, was achieved at
120 °C for the same sample.
