Search Results (4)

This study focuses on the utilization of surface modification technology to create glass disks with varying surface wettability. A measurement test bench for point contact lubrication film is employed to investigate the impact of changes in the angle between the velocities of the glass disk and steel ball on the state of the lubricating oil film at the interface. The results show that altering the surface wettability reduces the adhesive strength between the interface and the adjacent lubricant, leading to a decrease in the ultimate shear stress, and inducing interface slippage. When the rotational velocity of the disk matches the translational velocity of the ball and their trajectories are inclined at specific angles, the sliding velocity increases proportionally to the inclination angle, which contributes significantly to the thermal effect. Furthermore, when the velocity varies across the interface with differences in wettability, the contact zone forms a wedge-shaped gap and causes modifications in the oil film’s shape, including the formation of an inlet dimple and an inclined straight stripe. The dominant factor influencing the interface is the slip when the angle is acute, whereas the thermal effect plays a significant role when the angle is obtuse. This work is expected to provide a new strategy for elastohydrodynamic lubrication under surface wettability interfaces. Full article

The investigation in this article focuses on the rolling resistance torque and thermal inlet shear factor in tapered roller bearings (TRBs) through systematic experiments using a modular test setup. TRBs typically operate under Elastohydrodynamic Lubrication (EHL) conditions. At sufficiently high speeds, the majority of rolling friction is due to a significant shift of the pressure centre in the EHL contact. While at lower speeds, sliding friction in the roller-rib contact becomes dominant, which operates under mixed lubrication conditions. Limited literature exists on the impact of inlet shear heating on effective lubricant temperature ($T_{in\_c}$) and rolling friction in TRBs. To fill this gap, experimental measurements of the total frictional torque under axial loading at different speeds and oil temperatures are performed. With existing models for different friction contributions described in the literature, the rolling resistance due to EHL has been determined for various operating conditions. The effects of dimension-less speed (U), material (G), and load (W) parameters have also been investigated. Under fully flooded conditions, it was observed that the influence of material (G) and load (W) parameters on rolling friction is minor, while the impact of velocity (U) is significant. In the context of rolling resistance, the heating due to shear of the lubricant in the inlet zone plays a significant role. For higher rotational velocities, the estimated rotational torque reduction resulting from inlet shear heating was found to be approximately 6–8%. Full article

Steam methane reforming (SMR) is the most common commercial method of industrial hydrogen production. Control of the catalyst tube temperature is a fundamental demand of the reformer design because the tube temperature must be maintained within a range that the catalysts have high activity and the tube has minor damage. In this paper, the transport and chemical reaction in an industrial-scale steam methane reformer are simulated using computational fluid dynamics (CFD). Two factors influencing the reformer temperature, hydrogen yield and stress distribution are discussed: (1) the mole fraction of steam (Y_H2O) and (2) the inlet velocity of the reforming reactants. The purpose of this paper is to get a better understanding of the flow and thermal development in a reformer and thus, to make it possible to improve the performance and lifetime of a steam reformer. It is found that the lowest temperature at the reforming tube surface occurs when Y_H2O is 0.5. Hydrogen yield has the highest value when Y_H2O is 0.5. The wall shear stress at the reforming tube surface is higher at a higher Y_H2O. The surface temperature of a reforming tube increases with the inlet velocity of the reforming reactants. Finally, the wall shear stress at the reforming tube surface increases with the inlet velocity of the reforming reactants. Full article

In this paper, we study pulsed flow and heat transfer in water-Al₂O₃ nanofluids in a Y-type intersection channel with two inlets and one outlet. At the two inlets, two sinusoidal velocities with a phase difference of π are applied. We assume that the shear viscosity and the thermal conductivity of the nanofluids depend on the nanoparticles concentration. The motion of the nanoparticles is modeled by a convention-diffusion equation, where the effects of the Brownian motion, thermophoretic diffusion, etc., are included. The effects of pulse frequency, pulse amplitude and nanoparticles concentration on the heat transfer are explored numerically at various Reynolds numbers. The results show that the application of the pulsed flow improves the heat transfer efficiency (Nusselt number) for most of the cases studied. Amongst the four factors considered, the effect of the frequency seems to be the most important. Full article