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Ultrasonic waves is an unconventional enhanced oil recovery (EOR) technology and has been a point of interest as it is more economical and environmentally friendly. Numerous research works on ultrasonic waves application in EOR have been reported, nevertheless the studies on the effect of ultrasonic waves towards oil mobilization in porous media are still debatable. Therefore, this study aims to investigate the effect of ultrasonic waves on enhanced oil recovery of three types of oil (kerosene, engine oil and crude oil) and a brine sample at different temperatures (27°C, 35°C, 45°C, 55°C). A series of ultrasonic waterflooding experiments were conducted under controlled temperature conditions. Results demonstrated that oil recovery increases as the temperature increases during ultrasonic exposure compared to conventional waterflooding. The ultrasonic waves creates energy that increase the mobility of a displacing fluid thus reduce the viscosity of displaced fluids whereas the vibration energy produced from ultrasonic waves induced the mobility of the entrapped oil within the pores. The IR Spectra test indicates that the oil produced from ultrasonic simulated waterflooding for oils with different viscosity and density from the IR Spectra result without ultrasonic exposure due to the influence of flow behavior and sweep efficiencies of fluids. As conclusion, the ultrasonic cavitation is one of mechanism that could improve oil mobilization and enhanced oil recovery.

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Many studies have investigated natural convection heat transfer from the outside surface of horizontal and vertical cylinders in both constant heat flux and temperature conditions. However, there are poor studies in natural convection from inclined cylinders. In this study, free convection heat transfer was examined experimentally from the outside surface of a cylinder for glycerol and water at various heat fluxes. The tests were performed at 10 different inclination angles of the cylinder, namely, φ = 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, and 90°, measured from the horizon. Our results indicated that the average Nusselt number reduces with the growth in the inclination of the cylinder to the horizon at the same heat flux, and the average Nusselt number enhanced with the growth in heat flux at the same angle. Also, the average Nusselt number of water is greater than that of glycerol. A new experimental model for predicting the average Nusselt number is suggested, which has a satisfactory accuracy for experimental data.

Iron Oxide Nanoparticles (IONPs) have received unprecedented interest in various applications. The main challenges in IONPs are fluid stability due to agglomeration in a saline condition. This paper aims to investigate the colloidal stability of citric acid (CA), sodium dodecyl sulphate (SDS) and polyvinyl alcohol (PVA) under various molar ratios and levels of salinity. Firstly, the IONPs were synthesized using a facile co-precipitation approach. Secondly, the IONPs were coated using a simple dip-coating method by varying the molar ratio of CA, SDS and PVA. Next, the coated IONPs were characterized by using an X-ray Diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and a Field Emission Scanning Electron Microscope (FESEM) for the morphological and crystallographic study of coated IONPs. Finally, the coated IONPs were characterized for their zeta potential value and hydrodynamic size using a Zetasizer and their turbidity was measured using a turbidity meter. It was found that at a low salinity level, 0.07 M of CA-IONPs, a high zeta potential value, a smaller hydrodynamic size, and a high turbidity value of −40.9 mV, 192 nm and 159 NTU were observed, respectively. At a high salinity level, 1.0 M SDS-IONPs recorded a high zeta potential value of 23.63 mV, which corresponds to a smaller hydrodynamic size (3955 nm) and high turbidity result (639 NTU). These findings are beneficial for delivering cutting-edge knowledge, especially in enhanced oil recovery (EOR) applications.