Commercial Computational Fluid Dynamics Code Research Articles

Heuristic shape optimization of gas ducting in process and power plants

Sudden changes in the flow direction are quite common but are inevitable in the lay-out in gas ducting in process and power plants. While it is well known that such changes lead to high pressure drops and flow separation, the scope for optimization is limited by constraints such as on-site fabrication and lay-out limitations. In the present paper, we present an efficient, computational fluid dynamics (CFD)-based shape optimization method which results in lesser pressure drop and more streamlined flow while adhering to site-specific constraints in terms of the extent of changes that can be made. The method is based on velocity defect in the plane of the bend: if, at a particular streamwise location, the average velocity in one half of cross section is above (or below) the cross sectional average velocity by, say, 10% or more, then the width of the duct locally is increased (or decreased), if it is possible to do so within the lay-out restrictions. An iterative application of this criterion using a commercial CFD code is shown to lead to better design of the bend. The optimized solution is validated with experimental results.

Framework for the Shape Optimization of Aerodynamic Profiles Using Genetic Algorithms

This study developed a framework for the shape optimization of aerodynamics profiles using computational fluid dynamics (CFD) and genetic algorithms. A genetic algorithm code and a commercial CFD code were integrated to develop a CFD shape optimization tool. The results obtained demonstrated the effectiveness of the developed tool. The shape optimization of airfoils was studied using different strategies to demonstrate the capacity of this tool with different GA parameter combinations.

Numerical Simulations of Vertical Axis Wind Turbine with Controllable Blades

Wind power gives us non-polluting alternative to reduce the exploration of conventional fossil fuels.A novel vertical axis wind turbine(VAWT) has been developed that consists of several controllable plat blades.A computational investigation of the output characteristics of the VAWT has been conducted using the commercial computational fluid dynamics(CFD) code ANSYS 13.0.A validation study was performed using a Savonius turbine and good agreement is obtained with experimental data.Both fixed and rotating two-dimensional CFD simulations are conducted to further investigate the performance of the VAWT.Steady simulations have demonstrated that the VAWT has good self-starting ability with an averaged static torque coefficient of 1.09.The predicted maximum averaged power coefficient is 0.449,which is nearly 2 times of the Savonius turbine.

Performance Optimization in a Centrifugal Pump Impeller by Orthogonal Experiment and Numerical Simulation

In order to improve the hydrodynamic performance of the centrifugal pump, an orthogonal experiment was carried out to optimize the impeller design parameters. This study employs the commercial computational fluid dynamics (CFD) code to solve the Navier-Stokes equations for three-dimensional steady flow and predict the pump performance. The prototype experimental test results of the original pump were acquired and compared with the data predicted from the numerical simulation, which presents a good agreement under all operating conditions. Five main impeller geometric parameters were chosen as the research factors. According to the orthogonal table, 16 impellers were designed and modeled. Then, the 16 impellers equipped with the same volute were simulated by the same numerical methods. Through the variance analysis method, the best parameter combination for higher efficiency was captured finally. Compared with the original pump, the pump efficiency and head of optimal pump have a significant improvement.

Flowforce in a Safety Relief Valve Under Incompressible, Compressible, and Two-Phase Flow Conditions (PVP-2011-57896)

The use of relief valves is crucial for the safety of power plants. Indeed, these valves, simple but robust in their design, provide the ultimate protection when all other safety systems are inadequate. This study is focused on valve opening characteristics which can be studied through the determination of flowforces applied on the valve disk. A spring-loaded safety relief valve (SRV) (1½ in. G 3 in.) and its transparent model are tested under static conditions. The spring is removed and the forces, exerted at the valve disk for different inlet pressures and lift positions, are measured in compressible, incompressible, and two-phase flows. Results indicate that even for relatively small qualities (i.e., 5–10%), two-phase mixtures approach compressible flow behavior (especially for the higher lifts) in terms of disk force. Additionally, an inverse flowforce of air and water is noticed above a certain value of valve lift. Numerical simulations with a commercial computation fluid dynamics (CFD) code are performed in a 2D axisymmetric model of the valve for validation purposes. The main motivation of these computations is to obtain the qualitative physical explanation of this phenomenon revealing the displacement of the sonic line which occurs in air flow simulations. Finally, the importance of precise adjustment of the valve ring (in the smallest valve opening) for its optimal use is stressed by quantitative analysis using CFD simulations.

Investigations on thermal storage systems containing micron-sized conducting particles dispersed in a phase change material

The purpose of the present study is to investigate the performance enhancement of a shell and tube, latent heat thermal storage (LHTS) unit due to the addition of microsize copper particles in the phase change material (PCM). The thermo-physical properties of composites were experimentally obtained using Temperature-History technique. Numerical model was developed to explore the heat transfer characteristics of composites during both charging and discharging modes. The numerical model also features a transport equation for particle flux. The commercial computational fluid dynamics (CFD) code, FLUENT, was employed to solve the enthalpy-based two dimensional transient equations. In addition, exergy models were developed to demonstrate the effect of particle dispersion on exergy performance of LHTS systems. The thermal behavior and exergy performance in terms of exergy efficiency and total exergy stored of particle-dispersed PCM units are compared with those of pure PCM unit and nanoparticles composites. The heat transfer performance of PCM is significantly high throughout the discharging when microparticles are added. However, the enhancement could be observed only during the earlier stages of charging as particles are found to be hampering natural convection in the liquid PCM. When it comes to exergy performance, particles help in increasing the exergy efficiency of pure PCM system only when the natural convection is weak during charging. Also, the exergy recovered from composites is higher as compared to that of pure PCM and it is found that particles addition results in reduced storage capacity in terms of exergy.

Study on Noise Generation in a High Speed Centrifugal Fan

This study presents the investigation of aerodynamics and aeroacoustics of centrifugal fan using commercial computational fluid dynamics (CFD) code. The unsteady turbulent flow of the fan is simulated with Detached Eddy Simulation (DES) and the acoustics sources are computed based on the pressure fluctuations. The Ffowcs Williams and Hawking model is used to predict the tonal noises in aeroacoustics simulation.

표면조직 가공한 유압부품면에서의 윤활특성

Friction reduction between sliding hydraulic machine components is required to improve efficiency and reliability of hydraulic machineries. It is recently reported that surface texturing on sliding bearing surfaces can reduce the friction force highly. In this paper, numerical analysis is carried out to investigate the effect of dimple numbers and inlet boundary pressures on the lubrication characteristics of a parallel sliding bearing using a commercial computational fluid dynamics (CFD) code, FLUENT. The results show that the pressure distribution, load capacity, dimensionless friction force and leakage with dimple number and their locations, and inlet pressures. The overall lubrication characteristics are highly affected by dimple numbers and boundary pressure. The numerical method adopted and results can be used in design of efficient hydraulic machine components.

A study on the flow characteristics of a direct drive turbine for energy conversion generation by experiment and CFD

A variety of technologies has been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales. Due to the complexity of most offshore wave energy devices and their motion response in different sea states, physical tank tests are common practice for WEC design. Full scale tests are also necessary, but are expensive and only considered once the design has been optimized. Computational Fluid Dynamics (CFD) is now recognized as an important complement to traditional physical testing techniques in offshore engineering. Once properly calibrated and validated to the problem, CFD offers a high density of test data and results in a reasonable timescale to assist with design changes and improvements to the device. The purpose of this study is to investigate the performance of a newly developed direct drive hydro turbine (DDT), which will be built in a caisson for extraction of wave energy. Experiments and CFD analysis are conducted to clarify the turbine performance and internal flow characteristics. The results show that commercial CFD code can be applied successfully to the simulation of the wave motion in the water tank. The performance of the turbine for wave energy converter is studied continuously for a ongoing project.

정방형 공기덕트 내부의 유동특성에 원심력이 미치는 영향에 관한 연구

In this paper, an experimental and numerical investigation of transition characteristics in a square-sectional curved duct flow under Centrifugal force is presented. The experimental study is carried out to measure axial velocity profiles by using Laser Doppler Velocimeter (LDV) system. Computational fluid dynamic (CFD) simulation was performed using the commercial CFD code FLUENT to investigate the transition characteristics. The flow development is found to depend upon Dean number and curvature ratio. The velocity profiles in center of the duct have lower value than those of the inner and outer walls because of the centrifugal forces.

사이클로이드 및 폴리서클 곡선을 이용한 내접형 기어펌프용 치형 개발

A new type of gerotor developed in this paper has the inner rotor designed by inserting a polycircular-arc between the hypocycloid and epicycloid curves, and we also suggest that the outer rotor be designed using the closed-form equation for the inner rotor and a method of modification. Thus, it is possible to design a gerotor for which there is no cusp and loop, as in this case undercut is prevented. We developed automated program for rotor design and calculation of the flow rate and flow rate irregularity. And we also demonstrate the superior performance of the gerotor developed in this study by analyzing the internal fluid flow using a commercial computation fluid dynamics-code (CFD).

Investigation of the Flow Pattern in a Complex Inlet Duct of a Heat Recovery Steam Generator

Numerical simulation and experimental study were conducted in order to analyze flow patterns and finally to find out appropriate alternatives for uniform flow in the transition zone of the vertical type Heat Recovery Steam Generator (HRSG) for a gas turbine combined cycle. To understand flow patterns in the interconnecting duct between the gas turbine exhaust and the inlet of the HRSG, flow measurement was conducted in a 1/20 scale-down model. Velocities were measured by pitot tubes on selected sections and uniformity of the flow was quantitatively evaluated. Water table test was also carried out to visualize the flow and to compare the flow patterns according to the selection of alternative shape design of the transition zone, which would lead to better uniformity of the flow in the duct. Numerical simulation by a commercial Computational Fluid Dynamics (CFD) code was performed to augment the model tests and to consider various ideas for better uniformity. Finally, selected alternatives for the uniform flow chosen from the numerical study were checked against in experiments.

Three-dimensional performance analysis of plain fin tube heat exchangers in transitional regime

Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a four-row plain fin-and-tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS CFX 12.0. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 400 to 2000. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-ω) with steady and incompressible fluid flow. Model validation is carried out by comparing the simulated case friction factor (f) and Colburn factor (j) with the experimental data of Wang et al. [1]. Reasonable agreement is found between the simulations and experimental data. In this study the effect of geometrical parameters such as fin pitch, longitudinal pitch and transverse pitch of tube spacing are studied. Results are presented in the form of friction factor (f) and Colburn factor (j). For both laminar and transitional flow conditions heat transfer and friction factor decrease with the increase of longitudinal and transverse pitches of tube spacing whereas they increase with fin pitches for both in-line and staggered configurations. Efficiency index increases with the increase of longitudinal and transverse pitches of tube spacing but decreases with increase of fin pitches. For a particular Reynolds number, the efficiency index is higher in in-line arrangement than the staggered case.

Analysis and Optimization of Steam Duct for Improving Performance of Steam Cleaner

Not only the price of a steam cleaner but also the performance of it should be considered to improve the competitive power of the products. In this study, a steam duct was optimized by changing the length of guide line for compensating the drawback of the unbalanced mass flow rate of steam from each outlet. For evaluating the mass flow rate of each outlet, a commercial CFD(computational fluid dynamics) code was used. In the process of the optimization, SQP(sequential quadratic programming) optimization algorithm was applied. The numerical method in this study can be widely used to develop a high performance domestic steam cleaner.

Flow Characteristics of Polluted Air in a Rectangular Tunnel using PIV and CFD

The flow characteristics of polluted air are analysed by comparing the results obtained from PIV(Particle Image Velocimetry) experiment and CFD(Computational Fluid Dynamics) commercial code. In order to simulate the polluted air flow, the olive oil has been used as tracer particles with the kinematic viscosity of air, 1.51×10<SUB>-5</SUB> ㎡/s. The investigation has done in the range of Reynolds numbers of 870, 1730 and 2890 due to the inlet flow velocities of 0.3, 0.6, and 1.0 m/s, respectively. The average velocity and the pressure distributions are comparatively discussed with respect to the three different Reynolds numbers. The results show that the outlet flow rates at three different Reynolds numbers are equivalent of 165 to 167 percent of the inlet ones. The pressure drop occurs in the model closed at both end sides and the highest pressures at each Reynolds number are positioned at the top of the tunnel between the inlet and outlet.

Bypass flow computations using a one-twelfth symmetric sector for normal operation in a 350 MWth prismatic VHTR

Significant uncertainty exists about the effects of bypass flow in a prismatic gas-cooled very high temperature reactor (VHTR). Bypass flow is the flow in the gaps between prismatic graphite blocks in the core. The gaps are present because of variations in graphite block construction, imperfect installation and expansion and shrinkage from thermal heating and neutron fluence. Calculations are performed using computational fluid dynamics (CFD) for flow of the helium coolant in the gap and coolant channels along with conjugate heat generation and heat transfer in the fuel compacts and core graphite. A commercial CFD code is used for all of the computations. A one-twelfth sector of a standard hexagonal block column is used for the CFD model because of its symmetry. Various scenarios are investigated including varying the gap width, varying the total heat generation between average and peak rates and varying the graphite block geometry to account for the effects of shrinkage caused by irradiation. The calculations are for a 350MWth prismatic reactor. It is shown that the effect of increasing gap width, while maintaining the same total mass flow rate, causes increased maximum fuel temperature while providing significant cooling to the near-gap region. The maximum outlet coolant temperature variation is increased by the presence of gap flow and also by an increase in total heat generation. The effect of block shrinkage is actually to decrease maximum fuel temperature compared to a similar reference case.

Computational fluid dynamics (CFD) prediction of mass fraction profiles of gas oil and gasoline in fluid catalytic cracking (FCC) riser

Fluid catalytic cracking (FCC) is an important process for the conversion of gas oil to gasoline. The paper is an attempt to model the phenomenon theoretically; using commercial computational fluid dynamics (CFD) software and 3-lump kinetic model. Geometry, boundary conditions and dimensions of industrial riser for catalytic cracking unit is conferred for 2D simulation using commercial CFD code. Continuity, momentum, energy and species transport equations, applicable to two phase solid and gas flow, are used to simulate the physical phenomenon efficiently. This paper uses the granular Eulerian multiphase model with k–ε turbulence and species transport. Time accurate transient problem is solved with the prediction of mass fraction profiles of gas oil, gasoline, light gas and coke. The output curves demonstrate the mass fraction and distribution of temperature in both phases. At the end comparison of the computational results with other computational and experimental data available in literature is also given.

Thermal simulation of sodium heated once through steam generator for a fast reactor

In typical sodium cooled fast reactors, steam generators (SG) transports heat from hot liquid sodium to high pressure feed water. Feed water gets heated and converted to superheated steam and is used to roll the turbine. In SG, tubes are in triangular pitch pattern and shell in cylindrical shape, making some non-uniform gap at periphery allowing sodium to by-pass resulting radial thermal difference. Estimation of this thermal difference is very important in order to design a provision to accommodate the maximum differential thermal expansion among tubes and shell and to resist maximum thermal cycles faced by SG in its design life. A detailed three-dimensional thermal analysis of a sector model of SG with 30 m long tube is performed by combining a commercial Computational Fluid Dynamic code with in-house one-dimensional code DESOPT. The analysis is also validated with in-house experimental test facility results. From the analysis, the radial and axial temperature distributions and the differential temperature between tubes and shell are estimated for commercial fast breeder reactors SG for normal operation and typical plugged tube conditions and the results are highlighted in this paper. The results would form input for the estimation of differential thermal expansion of shell and tubes of SG and design of tube-sheets.

Computational fluid dynamic analysis of a supercritical CO2 based natural circulation loop with end heat exchangers

Steady state simulation of a 3D model of supercritical CO2 based natural circulation loop with end heat exchangers has been carried out employing the commercial CFD (computational fluid dynamics) code, FLUENT. The simulation considers phenomena such as viscous dissipation in fluid, axial conduction in fluid as well as in solid wall. Study has been carried out at a constant CO2 operating pressure of 80 bar. Results are obtained for various inlet temperatures of water in the hot heat exchanger, within the range of 323–353 K, for a fixed inlet temperature of cooling water in the cold heat exchanger (305 K). Results show that heat transfer rate increases with increase in HHX water inlet temperature whereas mass flow rate of loop fluid decreases. Due to the presence of bends and strong buoyancy effects, fluid parameters such as local velocity and temperature vary in all three dimensions which justifies the use of 3D model for this study. Results also show that even for a small temperature difference of 18 K, Reynolds number reaches a high value of the order of 105. Validation of simulation results against experimental results reported in the literature with respect to modified Grashof number (Grm) and Reynolds number (Re) exhibit good agreement.

CFD Analysis of Cable-In-Conduit Conductors (CICC) for Fusion Grade Magnets

In the present work, dual channel Cable-in-Conduit Conductor (CICC) is considered for Computational Fluid Dynamics (CFD) analysis to understand the complex behavior of flow. A two dimensional (2D) axisymmetric computational model mimicking the CICC is generated and meshed in GAMBIT 2.0. The meshed model is exported to FLUENT 6.3, a commercial CFD code, for further analysis. Annular bundle channel of CICC is assumed to be porous medium with porosity of 0.37 and the central channel is assumed as clear region. The effects of variations in mass flow rate (6 g/s to 10 g/s) of Supercritical helium (SHe), which is used as coolant, through CICC on the pressure gradients and velocity gradients are studied. Reynolds Averaged Navier Stokes (RANS) model is considered for the analysis with standard k-epsilon (k - e)turbulence, which is relevant to the separated flow models. Axial and Radial pressure gradients are calculated along the CICC axis and along the centre line of bundle channel. Friction factor is calculated using the shear stresses obtained from CFD analysis.