Abstract: The paper deals with the influence of microstructural changes of the nickel superalloy (NiS) on heat transport changes in MAR-M247. The dissolving annealing within the temperature interval of 900 – 1240°C and cooling in water has been applied to enhance structural changes. It has been shown that the narrow connection between the γ’ phase morphology changes, as well as values of density, thermal conductivity and specific heat capacity. In the dissolving annealing process, the γ’ particles change in certain cycles from fine to rough and back to fine one. Obtained results of changes of thermal conductivity, density and specific heat capacity correlate with image analysis and electron microscopy observation.
Abstract: This work addresses heat transfer in channels fitted with heat-conducting fins inserted in both walls, transversally to the flow direction, in a staggered arrangement. Turbulent fluid flow and conjugate heat transfer are assumed in the simulations. The hydrodynamic (pressure coefficient) and thermal (Nusselt number) behavior of the heat exchanger is investigated for different values of fin thickness, inclination angle and blockage ratio. The simulations show that the geometrical parameters of the finned channel cause changes in the flow topology, which in turn leads to significant differences in pressure drop and heat transfer rate. It is observed that the fin blockage ratio imposes the greatest effect in the hydrodynamic and thermal problems, followed by the fin inclination angle and thickness.
Abstract: Nowadays, global warming is central to all discussions, as governments are trying to make decisions in order to slow the greenhouse effect. This lead to the creation of “sustainable development”, which relies on renewable energies in order to preserve the environment. The development issues of renewable energy in Algeria drove the Algerian State to integrate it in the national energy mix. It is a major challenge regarding the preservation of fossil fuels, diversification of electricity production chains and contribution to sustainable development. Algeria launched a renewable energy development program going from 2011 to 2030 in order to revive economic growth in this country. The program recently concluded its first phase dedicated to pilot projects and testing various technologies available. The Renewable Energies and Energy Efficiency Development Program (REEEDP), in the revised version by the services of the Department of Energy, has just been adopted with the conclusions highlighted by its first phase.the preservation of fossil fuels, diversification of electricity production chains and contribution to sustainable development. Algeria launched a renewable energy development program going from 2011 to 2030 in order to revive economic growth in this country. The program recently concluded its first phase dedicated to pilot projects and testing various technologies available. The Renewable Energies and Energy Efficiency Development Program (REEEDP), in the revised version by the services of the Department of Energy, has just been adopted with the conclusions highlighted by its first phase.
Abstract: The present study has been attempted to systematically perform a visualizing analysis plan which can improve the flow rate, velocity and mass flow rate as a function of the size of the welding section in the injector as a key for the determination of the injection amount and time of the fuel (CH4) system for natural gas. As the setting conditions for the analysis, a minimum pressure of 2 bar and a maximum pressure of 8 bar were set to be the total pressure values in the case of the inlet, while 0 bar was set for opening drain to represent the state in the atmosphere in the case of the outlet. As a result, the characteristics with an increase in velocity could be affirmed as strong flow separation and eddy current were produced according to the model with a large size of welding section. An excellent performance with an improvement in the performance of velocity flow rate by about 40% could be affirmed in the model where the size of the welding section was designed to be 6 EA.
Abstract: In the paper the numerical solution concerning the skin tissue heating in the case of uncertain thermophysical parameters is discussed. The solutions of this type of problems presented previously are based on the application of interval arithmetic. In particular, the parameters appearing in the governing equations and boundary-initial conditions are treated as the interval numbers. Here, the authors propose another approach using for this purpose the methods of sensitivity analysis. The mathematical model of the process concerns the heterogeneous tissue domain subjected to an external heat source. At the stage of numerical modeling both the basic model and the sensitivity ones are solved using the finite difference method. In the final part of the paper, a computational example is presented.
Abstract: Alterations of boundary layer separation along the upper-rear surface of a baseline and slit cylinder and the formation of a vortex in the near-wake are investigated by particle image velocimetry (PIV) at Reynolds number 1000. The slit ratio (S/D) is 0.3. The phase-lock flow structures are referred to the time-dependent volume flux at the slit exit and are achieved by the modified phase-averaged technique. The alterations and the evolution of boundary-layer flow along the upper-rear surface are demonstrated by the phase-lock flow structures. It is found that the alternate blowing and suction at the slit exit serves as a perturbation to the boundary layer near the shoulder of the slit cylinder leading to a significant delay of flow separation and the flow reattachment of boundary-layer flow along the upper-rear surface of the cylinder. After perturbation, the vortex street behind a slit cylinder is more organized and stronger than that behind a baseline cylinder at Reynolds number 1000.
Abstract: This paper describes the LAD2D computer code, which numerically solves the equations of transient, multilaterals, compressible fluid dynamics. Of particular interest is the general capability to handle material interfaces, including slip, cavitations, or void closure. Also included is the capability to treat material strength and plasticity, as well as high explosive (HE). LAD2D uses a Lagrangian finite volume numerical technique. The method manages the sliding meshes and the internal meshes unifying as arbitrary polygonal meshes, and present a new changing connectivity of mesh technology based on the moving position of grid points with their topological relations. Of particular interest is the changing connectivity of mesh to handle the large deformation mesh and to close the gap during numerical simulation. The verification and validation (V&V) of LAD2D software was implemented based on the foundation of scientific software’s V&V method. Several applications of the changing connectivity of mesh are presented with comparison of calculations with experimental results to demonstrate the capability of the new method. The changing connectivity of mesh may be used on arbitrary geometries, using structured or unstructured meshes, and it leads to strong numerical simulation capability for multilaterals problems.
Abstract: This study conducted a computational analysis on the characteristics of the unsteady internal flow of the Urea-SCR injector using reverse engineering. The flow coefficient that changed according to time was calculated, and the flow-coefficient data from the injector-needle movement were secured. To objectively compare the responsiveness of the injector, the time taken by the flow-coefficient number to change in the injector-needle rise interval and to reach 80 % of the mean flow coefficient was indexed. The design variables of the injector, nozzle angles, and the number of nozzles were selected to analyze the effect on the mean flow coefficient and the total injection quantity. The study results indicate that the effect of the nozzle angles on the total injection quantity per time is insignificant, but when the number of nozzles was excessively increased, the total injection quantity per time was decreased. The characteristic changes of the initial flow coefficient of the increased needle regarding the injector-nozzle angle and the nozzle number were analyzed as the characteristics of the injector responsiveness. This analytic result is used as the basic material for the design of the injector.
Abstract: High rotational motion from the welding tool generates a significant amount of the heat during friction stir welding (FSW). Basically, during FSW the heat is mostly coming from the frictional force between the tool shoulder and the plates. Therefore, a precise calculation of the friction coefficient can increase the accuracy of the finite element analysis (FEA) of the process. However, researchers have applied constant values, and that causes a gap between the reality and the simulated model especially after the welding plunging step. In this study, a mathematical formulation is proposed in order to calculate the temperature dependent values of the friction coefficient and also to explore the influence of the temperature in the friction coefficient. To solve the governing equations of the process, the MATLAB® software is used. The results indicate that, from 25°C to the AA 6061-T6 melting point (580°C), the values of the friction coefficient fall steadily in a range of 0.207089 to 0.000582. Furthermore, the material shear stress and the material yield stress decrease consistently as the temperature rises. Consequently, the influence of the temperature in the contact input parameters and the material properties are discussed in detail and a good correlation with the published results is achieved.