To overcome the limited mixing efficiency associated with conventional steady-state side blowing in molten pool smelting, this study proposes a gas injection strategy that combines a swirl lance configuration with sinusoidal pulsed blowing. Using a volume-of-fluid (VOF) multiphase flow framework coupled with the Realizable k–ε turbulence model, the performance of constant-velocity blowing is systematically compared with sinusoidal pulsed blowing over a range of amplitudes (5, 10, and 15 m/s) and frequencies (0.5, 1, and 2 Hz). The results demonstrate that sinusoidal pulsed blowing markedly enhances gas–liquid mixing within the melt pool relative to constant-speed injection. Mixing efficiency increases with blowing amplitude, while its dependence on pulse frequency is nonlinear. Within the investigated parameter space, the optimal configuration, an amplitude of 15 m/s and a frequency of 1 Hz, raises the average gas volume fraction by 8%, reduces the mixing dead-zone area by 81%, and expands the active mixing region by 25%. Overall, the imposed sinusoidal pulsing promotes bubble breakup beneath the free surface, leading to more complete bubble collapse, intensified turbulent agitation, and, ultimately, improved gas–liquid mixing.

Highly integrated micro-nano electronic devices suffer from severe heat dissipation challenges, and flow cooling in nanochannels is an effective solution. During convective heat transfer at liquid-solid interfaces, surface wettability and rough morphology are key parameters governing thermal transport; however, their combined effects remain unclear. In this study, molecular dynamics simulations are utilized to examine the synergistic effects of surface wettability and nanopillar arrays on thermal transport and fluid dynamics within nanochannels. The results show that increasing surface hydrophilicity and roughness reduces the thermal slip length and increases the Nusselt number, thereby enhancing heat transfer performance in the nanochannel. From a fluid dynamics standpoint, velocity slip length decreases while the relative friction coefficient increases, signifying greater flow resistance. For the present model, the enhancement in heat transfer induced by increased wettability is significantly greater than that caused by increased roughness, whereas their effects on flow resistance are difficult to distinguish the dominance. At the microscale, increased wettability and roughness facilitate the accumulation of fluid atoms near the liquid-solid interface. The elevated interaction energy between solid platinum atoms and fluid argon atoms is identified as the primary mechanism underlying thermal transport enhancement in nanochannels. This investigation offers valuable insights for the optimized thermal management of micro-nano electronic devices.

A comprehensive understanding of thermal transport across solid-liquid interfaces is crucial for enhancing the performance of micro- and nanoscale devices, especially at the silica-water interface, which plays a key role in many applications in energy conversion and medical technologies. The adsorbed water layer at the silica interface plays a core role in solid-liquid interface thermal transport. However, the molecular-level structural transitions of this layer and their correlation with thermal transport mechanisms have not been extensively studied. In this work, molecular dynamics simulations were used to study the thermal transport mechanisms at silica-water interfaces with different hydroxyl densities, focusing on how interfacial H-bonds and layered structures influence interfacial thermal transport characteristics. The results of the study show that the interfacial thermal conductance increases with the hydroxyl density, while the density distribution of water molecules at the silica interface shows an opposite trend. The formation of H-bonds at the interface is identified as the main cause of this anomalous behavior. Through density, charge, H-bonds, and water molecule orientation distribution, the bilayer structure of the adsorbed water layer at the silica interface was defined at the molecular level, which is composed of the binding interface layer and the diffuse layer. The binding interface layer plays a decisive role in interfacial thermal transport. Through the analysis of interfacial potential energy, H-bonds dynamics, and Vibrational density of states, the microscopic mechanisms of thermal transport at silica-water interfaces with different hydroxyl densities were proposed by this work. These findings may provide new insights into the understanding of thermal transport mechanisms at solid-liquid interfaces.

Smelting with oxygen bottom blowing is one of the main methods used in the frame of copper pyrometallurgy. With this approach, feed materials and oxygen-enriched air are introduced in reversed order to enhance multiphase flow within the furnace. Understanding the flow structure and temperature distribution in this setup is crucial for optimizing production. In this study, gas-liquid interactions, and temperature profiles under varying air-injection conditions are examined by means of numerical simulation for a 3.2 m × 20 m furnace. The results indicate that the high-velocity regions are essentially distributed near the lance within the reaction region and the flue gas outlet, while low-velocity regions are located close to the furnace walls on both side of the reaction region. Dead regions appear in the sedimentation region, with gas velocities surpassing those of the molten phase. As the injection rate increases from 0.50 to 0.80 Nm³/s, the stabilization time of the average liquid surface velocity decreases from 2.6 s to 1.9 s, exhibiting a similar trend to the gas holdup. During stabilization, the average liquid surface velocity rises from 0.505 to 0.702 m/s. The average turbulent kinetic energy (TKE) of the fluid in the molten bath increases from 0.095 to 0.162 m²/s². The proportion of the area distribution with TKE greater than 0.10 m²/s² and the gas holdup at steady state both rise with an increase in the injection quantity. The maximum splashing height of the melt grows from approximately 0.756 to 1.154 m, with the affected area expanding from 14.239 to 20.498 m². Under different working conditions with varying injection quantities, the average temperature changes in melt zone and flue gas zone of the furnace are small. The temperature in the melt and in the flue-gas zone spans the interval 1200°C–1257°C, and 1073°C–1121°C, respectively. The temperature distribution of the melt and flue gas reveals a pattern characterized by elevated temperatures in the reaction zone, gradually transitioning to lower temperatures in the sedimentation region.