فهرست نشریات علمی دسترسی آزاد ایران

In this experimental study, titanium dioxide (TiO₂) nanoparticles were synthesized using an ultrasound-assisted technique. The structural as well as morphological characteristics of the produced TiO₂ nanoparticles were studied through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Heat transfer, as well as exergetic parameters of propylene glycol-water (PGW)-based TiO₂ nanofluid in a shell-and-tube heat exchanger, were then explored. The nanofluid was made ready by mixing 60% water and 40% propylene glycol, incorporating TiO₂ nanoparticle concentrations of 0.1 vol.%, 0.2 vol.%, and 0.3 vol.% through a two-step process. The flow rate of the nanofluid was varied between 6–12 l/min, while the flow rate of the hot water was maintained at 12 l/min. The study revealed that increasing both the flow rate and nanoparticle concentration of the nanofluid significantly improved the heat transfer rate ( ) as well as the overall heat transfer coefficient (U). Specifically, at a nanoparticle concentration of 0.3 vol.% and a flow rate of 12 l/min, the heat transfer rate increased by 44.3%, and the heat transfer coefficient increased by 46.1%. Furthermore, the average effectiveness of the heat exchanger improved with nanoparticle concentrations of 0.1 vol.%, 0.2 vol.%, and 0.3 vol.%, showing increases of 11.91%, 29.88%, and 41.82%, respectively. The research also indicated that exergy loss as well as the dimensionless exergy loss initially increased with higher nanoparticle concentrations but then decreased as the concentration continued to rise. Notably, at a concentration of 0.3 vol.% and a nanofluid flow rate of 6 l/min, the highest exergetic sustainability index (0.44) and the lowest environmental impact factor (2.3) were observed.