This study presents the results of an experimental investigation of the effect of electron-beam surface modification on heat transfer during nucleate pool boiling of distilled water at atmospheric pressure. The relevance of the research is driven by the need to improve the efficiency of cooling systems operating under high heat flux conditions. Copper surfaces with various microrelief geometries fabricated by electron-beam processing using the Surfi-Sculpt technique were employed as test specimens. Three types of modified surfaces were produced: star-shaped structures generated using both the forward and reverse electron-beam scanning modes, and a surface with a linear structure. Boiling curves and heat transfer coefficient versus heat flux relationships were obtained for all investigated samples. The results demonstrated that electron-beam surface modification significantly enhances boiling heat transfer compared with a smooth copper surface. For all modified specimens, the boiling curves shifted toward lower wall superheats, accompanied by an increase in the heat transfer coefficient and critical heat flux. It was shown that the heat transfer performance is strongly influenced by the geometry of the fabricated microrelief, which affects the density of active nucleation sites as well as the liquid supply and vapor removal mechanisms. The obtained results confirm the potential of electron-beam processing as an effective approach for the development of high-performance boiling heat transfer surfaces.
The paper considers the features of three-dimensional modeling of the thermal state of rotary piston engine (RPE) components in Ansys Fluent software. It is shown that a well-developed computational and experimental basis has been established for internal combustion piston engines (ICEs), whereas no unified methodology currently exists for RPEs that accounts for rotor motion and the nonuniform nature of heat transfer. A transient CFD modeling methodology is proposed using user-defined functions, a dynamic computational mesh, the Realizable k–ε turbulence model, the Finite Rate/Eddy Dissipation combustion model, and conjugate heat transfer between the gas, solid, and liquid domains. The methodology provides the pressure, temperature, and gas velocity fields, as well as temperature fields of engine components. Validation against experimental pressure and temperature data confirms the applicability of the proposed approach for engineering assessment of the thermal state and subsequent strength calculations.
A mathematical model based on solving Maxwell’s equations supplemented by the equation of motion of the magnetization vector in a ferromagnet taking into account the exchange interaction in the Landau–Lifshitz form has been constructed for magnetic nanostructures. An iterative computational algorithm for solving a nonlinear diffraction problem for an autonomous block containing magnetic nanoinclusions with virtual Floquet channels on the faces, which is reduced to solving a system of nonlinear algebraic equations, has been developed.
This paper presents a comprehensive study on the influence of coal particle concentration (0–50
In this paper, a new current equation of main discharge of transversely excited atmospheric (TEA) CO2 laser is introduced. The current equation is derived in consideration of the effects of electron collision with laser gas molecules on discharge current. Then, the collision-induced current equation is combined with the discharge circuit model and six-temperature model (6TM) to build theoretical model. Dynamic emission process of e-beam controlled TEA-CO2 laser is simulated using the model. The calculated result is in agreement with the experimental result in [33]. The power characteristics are analyzed for different initial electron densities. As a result, it has been found that there is a critical threshold of initial electron density that influences power characteristics to be deteriorated. The theoretical model can be used in the study of the behavior of gas laser discharge and designing of electron beam controlled TEA-CO2 laser.
