Studying the effect of using metal oxide nanofluids on the performance of a single-tube heat exchanger

The preparation of aluminum oxide from nanofluid (Al₂O₃/H₂O) in three different concentrations using a two-step method was achieved by using an atomic force microscopy (AFM). The AFM images showed that the nanoparticles took on a spherical shape with a range of average diameters and density within the range of 45–55 nm.

Polyacrylamide (PAAM) was used as a dispersion and suspension agent for aluminum oxide nanoparticles in distilled water at various concentrations (250, 500, 750, 1000) ppm during preparation, followed by determination of the polymer ratio for each sample during preparation, stability assessment by ultraviolet-visible (UV-Vis) spectrophotometer in the wavelength field (200–700) nm for 10 days, and analysis of sample Alumina nanoparticles by dispersion and suspension agent by high-pressure polymers tended M25 resulting in the highest concentrations of the given concentration. By increasing the PAAM concentration, the dispersion and stability of Al₂O₃ nanoparticles in distilled water appear to be improved, and concentrations of 0.25% seemed to be more evenly dispersed and stable over time, with minor sedimentation compared to (0.1%, 0.05%) vol concentrations, where the absorbance peak decreased by 5.5% despite the increase in size of Al₂O₃ nanoparticles and their aggregations, while the absorbance peak in the previous concentrations decreased by (14.2% and 8.8%), respectively of the two previous concentrations of Al₂O₃.

The study of PAAM polymers demonstrated that their rheological properties were not Newtonian, owing to a higher concentration of the polymer, resulting in viscosity results that resembled non-Newtonian polysaccharides.