numerical simulation

Slug flow is a part of an intermittent flow that is avoided in industrial applications because of its irregularity and high-pressure fluctuations. The present investigation aims to comprehend the behavior of intermittent slug flow with the gate valve and its associated pressure drop, slug liquid holdup, slug frequency, and averaged slug body length using CFD simulation studies. To achieve this objective, numerical investigations of slug flow were carried out on a horizontal pipe 10 m in length and 20 mm in diameter with three distinct area contraction ratios. First, the numerical results (slug frequency) were validated by comparison with other studies, and a reasonable agreement with an error of less than 3% was achieved. Second, the numerical results were validated by comparison with experimental data in terms of time and space for slug flow encountering the gate valve, and a sensible agreement with an error of less than 15% was achieved. Eventually, pressure gradient, slug frequency, slug length, and the existence of a gate valve have been investigated using numerical methods. The results showed that the slug frequency increases by 4.3% and this phenomenon is due to the small waves that occur due to the high pressure drop at the valve location. The length of the liquid slug increases by 20.89 percent by reducing the opening of the gate valve and decreases by 30.4 percent by increasing the surface velocity of the gas. By increasing the distance from the gate valve, the pressure drops decrease by 15.65%.

In this research, numerical simulation of the hot gas flow in the firing area of the pelletizing furnace in Golgohar mining-industrial complex is studied. In this regard, Open-Foam software as an objective-oriented program and based on a proper programming language is used. The considered area includes the outlet plane of the burners, the down comer pipes, the combustion chamber, the space of the furnace and the wind box, while the pellet bed is regarded as a porous media. The investigated flow is assumed as steady-state, compressible and turbulent that passes through the pellet bed having a uniform porosity percentage. In order to model the turbulent flow, an appropriate two-equations approach is employed. In addition, the walls of the furnace are assumed to be insulated, the gradients of the temperature and pressure on the walls are considered to be zero, and non-sliding condition is regarded for the boundary condition of the velocity. The simulation results illustrate that the hot gasses are diverted on the sidewalls, which could be considered as an important factor for corrosion and decreasing their life.

The production of electricity by solar thermal power plants is one of the promising ways to utilize renewable energy sources and reduce greenhouse gas emissions. Solar thermal power plants use concentrated solar radiation to heat a fluid that drives a turbine or an engine. One of the common technologies for concentrating solar radiation is the linear parabolic trough collector, which consists of a parabolic-shaped reflector that focuses the sunlight onto a receiver tube located at the focal line. In this research, the turbulent fluid flow and heat transfer in tubes with solid and porous fins as well as without fins were investigated numerically using a three-dimensional computational fluid dynamics (CFD) model. The objective was to study the impact of the fin type on the heat transfer and flow structure at different Reynolds numbers, which represent the ratio of the inertial forces to the viscous forces in the fluid. The findings showed that using the porous fin, the friction coefficient decreased and overall Nusselt number increased compared to the solid fin and the plain tube. The porous fin enhanced the heat transfer by creating more mixing and vortices in the fluid, while reducing the pressure drop by allowing some fluid to pass through the fin. The results of this research can provide useful insights for the design and optimization of internally finned tubes for solar thermal power plants.

In this research, the thermal performance of the earth -to-air exchanger with three parallel pipes is simulated in 3D. The thermal saturation of the soil in the considered exchanger with a length of 30 m and a burial depth of 3 m in Tehran city has been investigated. The aim of the research is to investigate the effect of the distance between the pipes on the thermal saturation of the around soil consequently, its effect on the exit temperature and the overall heat transfer rate. The results showed that in the first days of operation, the temperature of the air exiting from the middle and side pipes does not change much; But with the passage of time, the temperature of the air in the middle pipe decreases to a smaller amount than the side pipes. The distance between the pipes has a significant effect on the outlet temperature of the middle and side pipes, especially after a few days of system operation. By increasing the distance between the pipes from 25 to 50, 75 and 100 cm, the heat transfer amount from the middle pipe at a flow rate of 0.1 kg/s increases by 14.5%, 26.5 and 35.6%, respectively.

The use of renewable energy has recently become very common in most countries of today's society. Among these renewable energies, wind energy is one of the most attractive methods of mechanical energy production, and different methods of flow control, including active, semi-active and passive, have been investigated by various researchers. To control the fluid flow in an active way on the wind turbine blade, the corona discharge actuator based on plasma is considered the most appropriate method to reduce the fluid flow separation on the wind turbine blade. In this paper, we present a numerical simulation to integrate active load control using a corona discharge based on plasma actuators over the roughness blade. Effects of roughness, actuators voltage and frequency on aerodynamics parameters such as separation point, lift and drag coefficients have been showed. Present results showed that, the lift coefficient increase with increase in the voltage and frequency of plasma actuators. Overall, using the roughness for outer surface of blade would decrease the critical pressure coefficient by approximately 50% compared to that for the smooth surface.

In this article, the analysis of the flow field and forced convection heat transfer of non-Newtonian fluids inside the channel with spindle-shaped obstacles is discussed. At first, after checking the governing equations and the boundary conditions of the problem, the grid independency has been evaluated. Then, the results of the present study have been validated for two cases of the Newtonian and non-Newtonian fluids with previous similar works. The effects of various parameters such as the effect of the arrangement of spindle obstacles, the effect of the obstacles diameter and the effect of the obstacles length have been investigated. Also, the effect of different power indexes of non-Newtonian fluid and its effect on drag coefficient and Nusselt number have been investigated. By examining the results, it was found that for all the mentioned parameters, the staggered arrangement of the spindle obstacles had a higher heat transfer rate than the ordered arrangement. The results of this research revealed that with the increase in the diameter and length of the obstacles, the amount of heat transfer from the obstacles decreases. Also, by increasing the diameter of obstacles, the pressure and friction drag coefficients increases. Finally, by examining the behavior of the non-Newtonian fluid of the power-law model, it was found that with the increase of the power index, the Nusselt number decreased and for shear thinning non-Newtonian fluids (n<1) less friction and pressure drops were obtained.

Augmented reality is one of the new technologies in recent decade that has appeared especially in mobile devices. In augmented reality, virtual objects are placed in a real environment, next to other real objects. Another reason for the importance of augmented reality is the implementation of augmented reality applications on mobile and personal devices such as smartphones and tablets. The integration of augmented reality with a numerical simulation method such as computational fluid dynamics provides a cognitive, scientific and efficient tool for expert and non-professional users to analyze practical problems. In addition, using computational fluid dynamics techniques and an augmented reality-based system, engineering analysis and simulation results are obtained directly on real-world objects, resulting in a better understanding and relationship between the simulation results and the world. It becomes real. In this research, the combination of augmented reality and computational fluid dynamics method has been used to implement an Android software to simulate the thermal changes of solids with different materials over time.

In this study, the heat transfer of nanofluids as single-phase, incompressible, laminar, permanent in a two-dimensional sinusoidal channel under the influence of a magnetic field with a porous medium is investigated. Alternating heat flux is applied to the channel walls. The governing equations are discretized using Fluent software with finite volume method (FVM) and velocity and pressure coupling is performed using SIMPLE algorithm. The Reynolds number range is 500 ≤ Re ≤ 200. Water is considered as the base fluid and magnesium oxide nanoparticles have been added to it. The volume percentage of nanofluid is 0.04. Nanofluid flow in 4 different Darcys (0.00001, 0.0001, 0.001, and 0.01) and magnetic field application in 4 Hartmann numbers (0, 4, 7 and 10) have been investigated. The results show that in all cases, with increasing Hartmann number, the heat transferred improves and the pressure drop increases. By increasing the Darcy number from 0.00001 to 0.01 under the same conditions (Reynolds 500 and Hartmann 10), the Nusselt number equals 4.392. Also, with increasing the Darcy number, the viscous resistance decreased and the pressure drop was always lower, so that the numerical pressure drop ratio was less than 1.

After years from the first day of operating a power plant, it has been seen that the pipes of the high-temperature super heater suffer from damage and failure. In-depth investigations have revealed that the damage has occurred suddenly and remained heavy ruining instrumentations and buildings. Experiments and finite-element numerical simulations are conducted to understand the risk factors. The experiments such as gas flue analysis, hardness test for both intact and damaged tubes, the morphology of the failure part, and the analysis of the sediment inside the tubs are done. The main reasons for the failure of the super heater unit are found to be: striking hot flue gases with temperature of 530° Celsius and the stress of thermal elongation of the tubes .With the obtained results, some remedies such as using soot removal systems, using high-quality fuels, modifying combustion systems for applying fuels out of design, and using adjustable burners can be presented to solve the aforementioned problems. The current results can be valuable for other researchers to prohibit similar phenomena.

One of the most important problems that energy absorbers as thin-walled structures have been considered by designers, is the amount of energy absorption and the initial peak crushing load. In this paper, the crashworthiness of end capped circular aluminum tubes under axial compression is investigated. In this design, in order to reduce the initial maximum crushing load, holes were created in the outer surface of the adsorbent with specified distances along the tube. The presence of annular holes as a imperfection in the absorber prevents the sudden load applied to the main structure and the occupants. In this study, using numerical simulation by ABAQUS software, the effect of the presence of holes, angle and direction of applied oblique load has been studied on the crashworthiness of end capped tubes. Also, in order to validate the numerical simulation results, a number of experimental tests were performed which showed good agreement. The results showed that the applied oblique load with an angle of 10 degree and the opposite direction of the holes is effective on the state of collapse, energy absorption and reduction of initial peak load, and the angles of 20, 30 and 40 degree do not have significant changes in initial peak force and energy absorption.

The process of roomchr('39')s air-conditioning system is used to enhance thermal comfort and to reduce energy consumption. Although most of the researches have concentrated more on flow rate and optimum temperature of inlet air, the present study software was used to obtain the best possible locations for inlet and outlet channels for 20 samples of room using Ansys Fluent. Three factors including ventilation efficiency, effective average temperature, and vertical temperature gradient were considered to find the best location for inlet and outlet port locations. As a result, model 20, where inlet channel placed in the middle of opposite wall from manikin and the outlet channel located at the bottom of the same wall, was approved. In this sample, the average temperature was 23.68; the ventilation efficiency was 2.36; and the average effective temperature was -1.01. Moreover, the analysis of rooms with area of 12 𝑚2, 16 𝑚2, and 20 𝑚2 showed that by increasing the area, the ventilation efficiency decreased by 11.86%, and by increasing the air flow from 0.045 to 0.134 m3/s, the average temperature room decreases 12.54%.

Boilers are one of the major energy consumers in the building. For this reason, increasing the efficiency of this device and improving its performance is an effective step in solving the problems in building energy and reducing waste energy. Due to the limited resources of fossil fuels and the increasing cost of energy in the world, manufacturers of these equipment are always working to improve the performance and use of appropriate control equipment. The purpose of this study is to increase the thermal recovery efficiency of steam energy in gases from shell and corrugated tubes condensing boilers. Numerical simulations are performed using commercial CFD code, ANSYS FLUENT 18.2. In this research, the effect of different arrangement of tubes in a shell and corrugated tubes condensing boiler are analyzed numerically. There are 10 tubes with three different arrangements inside the shell. The results show that the first model has clearly better heat recovery performance than the other two investigated models because of its irregular position of the tubes. The numerical model is validated by experimental results. According to the comparison of the results, the maximum difference is 6.9% and 8.9%. So simulation result shows good agreement and accuracy. Also, 10 pipes with 3 different configurations are used inside the tube. results reveal that nonlinear and irregular configuration is better than two other models.

Friction stir welding (FSW) is one of the solid state bonding methods. One of the influential factors in the mechanical and metallurgical properties of the final joint is the tool shape, which, with its proper design, can ultimately achieve optimal joint quality. Among the improvements and modifications to improve the mechanical properties of the final joint is the out-centering of the tool pin against the tool shoulder. Off centering the pin will cause the heat generated in the larger area to be distributed and the volume of the deformed material will increase with the eccentric tool pin. In the present study, the development of a thermal model for tool with an out of center pin has been addressed. The modified model is a function of the temperature dependent friction coefficient and the temperature dependent yield stress, in which the effect of key parameters on the amount of heat generated in the FSW process is considered. In order to validate the developed model, three-dimensional simulation using ABAQUS package and two subroutines of USDFLD and DFLUX have been used. The results of the temperature distribution of the developed model have been compared with the experimental and analytical results of previous studies. Based on the results, the present thermal model with high precision is able to predict the maximum temperature and temperature distribution in the FSW process with an out of center tool pin.