Defect and Diffusion Forum Vol. 442

Abstract: The present study provides a comprehensive computational fluid dynamics analysis of the operation of an open-circuit subsonic wind tunnel. The analysis focuses on the uniformity in the test section, such as velocity distribution and pressure drop, which are crucial for wind tunnel performance. The inlet velocity from the contraction cone is altered, specifically 1.2 m/s, 2.4 m/s, and 3.5 m/s, for assessing the velocity of nine locations in the test section. The simulation results in the test section between the k-ε and k-ω viscous models were compared in this study. The highest velocity value was obtained at points 1, 3, 7, and 9 of the k-ω and k-ε viscous models at an inlet velocity of 3.5 m/s. The velocity differences in the test section between the k-ω and k-ε viscous models were about 0.01% to 0.11% at different inlet velocity. Furthermore, the highest pressure drop produced at an inlet velocity of 3.5 m/s is 173.33 Pa for the k-ω viscous model, followed by the k-ε at 160.82 Pa.

Abstract: The FeSi system is a compound forming alloy which exhibits the interesting behavior with respect to the composition. In present work, the thermophysical properties of FeSimelts at 1873 K have been explored on using four-parameter model which is based on Maclaurin infinite series. The analytical expressions for various thermodynamic and microscopic functions have been deduced using the standard thermodynamic relations. The model parameters are estimated using experimental data of activity coefficients and excess free energy of mixing for FeSi melts at 1873 K. For theoretical calculations of the thermophysical properties of FeSi liquid alloys at 1873 K, the same values of the model parameters are used in order to maintain the consistency. The composition dependence of theoretical data for Gibbs free energy of mixing and thermodynamic activities are in excellent agreement with the corresponding experimental data at 1873 K. On using the temperature dependence of model parameters, the enthalpy of mixing and entropy of mixing of FeSi molten alloys at 1873 K arecomputed. There is a well agreement between the theory and experiment. The theoretical values of concentration-concentration structural factor, known as concentration fluctuations in the long wavelength limit agree well with experimental data for FeSi system in molten state at 1873 K. The microscopic function such as short-range order parameter has also been computed as a function of concentration of FeSi melts at 1873 K. Again, the surface properties such as surface concentration and surface tension of FeSi molten alloys at the temperatures at 1823 K and 1873 Kare analyzed by Butler modelin the framework of four-parameter model. The theoretical values are compared with the data available in the literature at 1823 K which show well agreement. Again, the excess free energy of mixing, heat of mixing, concentration fluctuations and short-range order parameter are explored at 1823 K, 1873 K, 1923 K and 2073 K. Further, the transport properties like diffusivity ratio and viscosity of FeSi liquid alloys at 1823 K, 1873 K, 1923 K and 2073 Kare computed. For this, a simple statisticalmechanical modeli.eMoelwyn-Hughes model isemployed in the framework of four-parameter model. The theoretical data exhibit the qualitative agreement with the data available in the literature. The present study reveals that FeSi melt is an ordered system in the temperature range 1823-2073 K. The model parameters are temperature dependent. The concentration dependence of short-range order parameter and diffusivity ratio indicates that there is a likelihood of the existence of complex in FeSi liquid alloys. Keywords:Free energy of mixing; heat of mixing; concentration fluctuations; short-range order parameter, surface tension; viscosity

Abstract: This paper focuses on the influence of obstacles and the use of nanofluid on heat transfer in turbulent flow along the channel. The governing equations were solved utilizing finite volume method. The main objective is to study the variations of the Reynolds number, as well as the a/b ratio, the distance between obstacles, and the volume fraction influencing the Nusselt number and the friction factor. The results indicate that the presence of obstacles in a channel and increase of Reynolds number can increase the heat transfer by inducing the formation of turbulent zones. As well, the use of nanofluids with a volume fraction also proves beneficial for heat transfer due to the increased thermal conductivity of the fluid. These results could have significant industrial and technological importance.

Abstract: This study proposes a numerical investigation of turbulent flow and heat transfer properties within an air channel featuring a 7-shaped baffle affixed to the lower wall. The main objective of this computational investigation is to assess how the Reynolds number influences the enhancement of heat transfer across a range of Reynolds values from 18000 to 33000. To solve the governing equations, the QUICK numerical scheme and the SIMPLE discretization algorithm are employed. The numerical results are presented through variations in mean velocity and temperature, as well as profiles of local Nusselt number, friction coefficient, Nusselt number and friction factor. These representations facilitate a comprehensive exploration of the aerodynamic and thermal flow properties.

Abstract: The analysis of unsteady MHD flow over a porous stretching plate is critical for various engineering applications, particularly in systems involving chemical reactions and thermal radiation. This study explores the novel effects of heat and mass transfer in a two-dimensional unsteady magnetohydrodynamic (MHD) flow. This present work examines the effects of radiation and a transverse magnetic field on a chemically reacting fluid flowing over a stretched plate. The unsteady nature of the flow is associated with the time-dependent variations in stretching/extending velocity, temperature, and fluid concentration. The nonlinear governing boundary layer partial differential equations (PDEs) are transformed into a set of nonlinear ordinary differential equations (ODEs) using a similarity transformation, which are then numerically solved using the MATLAB bvp4c method. The flow, heat, and concentration profiles are quantitatively analysed through graphs for various problem parameters, including the unsteadiness parameter (A), Hartmann number (M), porosity parameter (Sp), radiation parameter (N), chemical reaction parameter (K), Soret number (Sr), Eckert number (Ec), Schmidt number (Sc), and Prandtl number (Pr). Additionally, the skin friction coefficient, Nusselt number (Nu), and Sherwood number (Sh) are numerically addressed and illustrated using graphs.

Abstract: Out-of-furnace treatment of steel has many possibilities for correcting the iron-carbon semi-product obtained at the previous stage of steel production. This is ensured both by various methods of maintaining the temperature and by introducing the necessary correcting or modifying additives into the ladle with subsequent averaging stirring of the melt. At the same time, the bottom type of purging through one or more purging units became the most widespread. The paper presents the results of research on the nature of the flows created during bottom purging through a block with non-directional porosity. The research was conducted with the help of a full-scale physical model using water as a model fluid and using the conductometric method of establishing the homogeneity of the liquid bath and dissolution additives of the “heavy” type (using NaCl salt for modelling). Those additives dissolve mostly at the bottom and, for their volume distribution, require the creation of sufficient mixing flows. The study was carried out at different intensities of gas supply for purging according to the purging modes corresponding to industrial conditions. It was established that during purging in the bubbling mode through a block with non-directional porosity, the largest change in concentration during purging occurs in the volume of the liquid bath at the level of more than 25% from the bottom of the ladle. A large change in concentration indicates a significant volume of dissolution of “heavy” additives that dissolve at the bottom. This can be explained by the formation of conditions for the spiral rotation of the grouped bubble flow that breaks into individual bubbles at a distance of approx. 75% from the bottom of the ladle. Such flows create active horizontal mixing of the liquid bath. The best conditions for mixing the liquid bath, under conditions of addition of “heavy” additives that dissolve at the bottom, with the shortest homogenization time among the studied conditions were purging with an intensity of gas supply of 0.684-1.026 m³/t steel per h.