Modeling and investigation on the heat transfer in nanofluids

A fluid that contains suspended solid particles which have a diameter of approximately 10-9 m called as nanoparticles is called a nanofluid. The nano particles have demonstrated great potential to improve the heat transfer characteristics of heat transfer fluids. Previously developed correlations have not completely predicted the anomalous increase in the thermal conductivity of nanofluids. Possible parameters responsible for this increase were studied. A solid - liquid interface, also referred to as a nanolayer is considered to be one of the main reasons for the enhancement of the thermal conductivity. The heat transfer profile in the nanolayer region was combined with other parameters such as volume fraction, particle radius, thermal conductivity of the fluid, particle and nanolayer to formulate a new correlation. Results predicting the thermal conductivity of nanofluids using the new correlation were compared with experimental results as well as studies by other researchers. Overall the comparison of the results obtained for the nanofluids studied shows that the correlation proposed is in closest proximity in predicting the experimental results for the thermal conductivity of a nanofluid. A parametric study to understand how a number of factors affect the thermal conductivity of nanofluids was performed using the newly developed correlation. Different base fluid and nanofluid combinations such as Copper Oxide (CuO) in Ethylene Glycol, Titanium dioxide (TiO2) in Ethylene Glycol, Aluminum Oxide (Al2O3) in water (H2O) and the Iron (Fe) in Ethylene Glycol were studied. Results from the parametric study show that the thermal conductivity of the nanofluid increases as the thickness of the nanolayer increases. It also increases as the volume fraction increases and decreases as the radius of particle increases.