Evaluation of hydrodynamic behavior of biosand filters using computational fluid dynamics combined with the design of experiments

Biosand filters (BSFs) are widely used in rural and urban areas where access to drinking water is limited or non-existent. This study applies computational fluid dynamics in the assessment of hydrodynamic characteristics considering changes in the design of two BSF models to make construction options available to communities, without losing hydrodynamic efficiency. The commercial code ANSYS-CFX 20.1 together with a central composite design of experiments methodology to simulate the flow was used under different combinations of porosities, permeabilities, pipe diameters, and filter diameters and heights. These parameters were combined statistically from Statistica 13.3. Our results have shown that combining greater filter depths with smaller pipe diameters has played a key role in the BSF best performance, and the CAWST V10 model has performed better than HydrAid, with lower velocities and longer hydraulic retention times.

Numerical Study on Aerodynamic Performance of S809 Wind Turbine

Wind energy has emerged as one of the cleanest and sustainable sources of energy and is a potential resource for meeting the future’s electricity demand. Evaluating the aerodynamic performance of the turbine blade in complex environmental conditions is vital for designing and developing energy-efficient wind turbines. This work aims to undertake aerodynamic analysis of a Horizontal Axis Wind Turbine i.e. NREL Phase IV. Computational fluid dynamics (CFD) models are presented using ANSYS-CFX software. Blade geometries were tested at different wind speeds ranging from 5 m/s to 30 m/s. The power output and pressure coefficients obtained from numerical simulations are compared with experimental data published on wind turbine.

Some Effects on the Temperature of the Mine Air at the Heading Face

Currently, with the increase in mining output leading to deeper mining levels, the volume ofheading face serving production has also increased. The thermal environment tends to worsen whendigging deep due to the geothermal's effect, which increases the air temperature at the heading face.According to QCVN01/2011-BCT, the temperature at the heading face is not allowed to exceed 300C. Toensure this, in Vietnam today, mainly forced ventilation method uses local fans to provide a clean amountof air to ensure a favorable environment for workers. With the forced ventilation method, the duct positionis usually arranged on the side, and the distance from the duct mouth to the heading face is determined toensure that l < 6√s. In this study, a numerical simulation method by Ansys CFX software is applied tostudy the influence of several factors such as duct position, air temperature of duct, and roughnesscharacteristics of roadway on the temperature of the mine air at the heading face. The models are set upwith six duct positions and four air temperature of duct parameters. Model 1 (y =1.1 m) is better thanmodels 2 to 6 in terms of temperature distribution and the lowest temperature values. Four models havedifferent wind temperatures, and we can see the significant influence of the inlet air temperature of theduct on the thermal environment of the heading face. The results show that with the model T = 297.15K,the temperature value on the roadway length is guaranteed as specified < 303K. The result is a referencefor determining the duct position and cool for the high-temperature heading face.

Increasing the production of the Mo-99 isotope by modernizing the design of targets irradiated in the experimental channels of the VVR-c reactor

There are various ways to obtain Mo-99. Some of them are widely used in industrial production, others are in the research stage with the aim of increasing the product yield. The main industrial method for obtaining Mo-99 using a nuclear reactor is the fragmentation method. This method provides for the presence of a uranium target and a nuclear reactor. The target is placed in the channel of the reactor core and irradiated with neutrons for the required time. After that, the target is removed from the channel to the “hot” chamber for the chemical separation of Mo-99. This is how Mo-99 is obtained practically all over the world. The paper considers the fragmentation method for producing Mo-99, which is implemented on the basis of the engineering and technological complex of the VVR-c research nuclear reactor. In order to increase the yield of Mo-99, a modernized model of the “tube-in-tube” target is proposed. The assessment of the production of Mo-99 and the cooling efficiency of the modernized target was carried out. The calculations were performed using the VisualBurnOut and Ansys CFX software packages. Computational studies have shown an increase in the energy release and the amount of the produced Mo-99 isotope in the target of the modernized design. In the most stressed zones, the target wall temperature exceeds the water saturation temperature. Surface boiling occurs in these zones. As a result, turbulization and mixing of the near-wall boundary water layer increases. This improves heat dissipation.

Optimisation of a Side Inlet for H2 Entry into an Ultrasonic Spray Pyrolysis Device

An ultrasonic spray pyrolysis (USP) device consists of an evaporation and two reaction zones of equal length, into which an aerosol with a precursor compound enters, and where nanoparticles are formed in the final stage. As part of this research, we simulated the geometry of a side inlet, where the reaction gas (H2) enters into the reaction tube of the device by using numerical methods. Mixing with the carrier gas (N2) occurs at the entry of the H2. In the initial part, we performed a theoretical calculation with a numerical simulation using ANSYS CFX, while the geometries of the basic and studied models were prepared with Solidworks. The inlet geometry of the H2 included a study of the position and radius of the inlet with respect to the reaction tube of the USP device, as well as a study of the angle and diameter of the inlet. In the simulation, we chose the typical flows of both gases (N2, H2) in the range of 5 L/min to 15 L/min. The results show that the best geometry is with the H2 side inlet at the bottom, which the existing USP device does not allow for. Subsequently, temperature was included in the numerical simulation of the basic geometry with selected gas flows; 150 °C was considered in the evaporation zone and 400 °C was considered in the other two zones—as is the case for Au nanoparticle synthesis. In the final part, we performed an experiment on a USP device by selecting for the input parameters those that, theoretically, were the most appropriate—a constant flow of H2 5 L/min and three different N2 flows (5 L/min, 10 L/min, and 15 L/min). The results of this study show that numerical simulations are a suitable tool for studying the H2 flow in a UPS device, as the obtained results are comparable to the results of experimental tests that showed that an increased flow of N2 can prevent the backflow of H2 effectively, and that a redesign of the inlet geometry is needed to ensure proper mixing. Thus, numerical simulations using the ANSYS CFX package can be used to evaluate the optimal geometry for an H2 side inlet properly, so as to reconstruct the current and improve future USP devices.

NUMERICAL MODELING OF A VERY LARGE CRUDE OIL CARRIER USING ANSYS CFX: A CASE STUDY OF SALINA

Specification of the frictional resistance values of tankers is the first step in managing their fuel consumption. Drag force of a very large crude oil carrier has been calculated using the numerical simulation method. With application of the ANSYS CFX software, the scaled model of the mentioned tanker with the length of 2.74 meters, width of 0.5 meters, draft of 0.17 meters was used for numerical simulation of the drag force in the tanker. Furthermore, the numerical solution of the drag force of the model was performed for 5 different speeds ranging from 0.65 to 0.85m/s. Based on the validations carried out, with mean drafts of 8 and 16.5cm, the difference between the results of the experimental and numerical models at low speeds was about 7%. However, the difference was observed to be up to 15% at higher Froude numbers. The results of the present study with respect to the SALINA are based on the method presented in ISO 19030 standard addressing the performance monitoring during vessel servicing.

Numerical Dimensioning of a Pre-Cooler for sCO2 Power Cycles to Utilize Industrial Waste Heat

The annual waste heat available from industry in the European Union is more than 2700 PJ. Consequently, the utilization of the unexploited thermal energy will decisively contribute to a reduced overall power consumption and lower greenhouse gas emissions. In the present investigation, a cycle layout, based on supercritical carbon dioxide (sCO2), was applied for a certain waste heat source, a gas compressor station. The boundary conditions determined by the cycle were used by the numerical code ANSYS CFX to design a pre-cooler. Subsequently, this printed circuit heat exchanger was examined for sCO2 mass fluxes between 100 kg/m²s and 900 kg/m²s. The heat transfer and pressure drop increase as the flow channel diameter is reduced. As the pressure drop of the coolant channel is more sensitive to the diameter, a larger coolant channel diameter is selected to maintain a reasonably low pressure drop. The optimum pre-cooler design consists of a 0.5 mm and 0.8 mm channel diameter for the sCO2 and coolant channel. Based on these results, internal fins were applied and optimized, to improve the heat transfer performance. An internal fin height of 4 mm was found to achieve the optimum thermal-flow performance for the pre-cooler.

Drilling mud upward velocity modelling in Ansys CFX software

Drilling mud has various functions, one of which is to carry cuttings to the surface. All other things being equal, the removal of cuttings is characterized by the upward velocity. This paper simulates the rheology of polymer-glycolic non-dispersing mud (in particular viscosity) to achieve the required upward velocity in the «Ansys CFX» software. The viscosity of the mud varies from 6 to 12 mPa·s, on production casing drilling in Arctic conditions. The results of the study showed that for such conditions, the viscosity should be in the range from 6 to 8 mPa·s.

ANSYS-CFX simulation of the SRBTL test loop core with nanofluid coolant

In the present study, CFD calculations are presented for the three types of water-based nanofluids Al2O3/water, CuO/water and TiO2/water with 0.1% volume fraction. These calculations are done with ANSYS-CFX and as geometry the SRBTL test loop as scaled down test loop for a VVER-1000 reactor core design is used. The goal of this study is to evaluate the CFD program against the SRBTL test loop core as a scaled core for applying water-based nanofluids as coolant. ANSYS-CFX simulation data are validated against the RELAP5/MOD3.2 simulation data for pure water. This comparison shows a good agreement. The simulation results for the nanofluids and water including Re number, temperature, viscosity, pressure drop and heat transfer coefficient through the SRBTL test loop core are compared. The results of the comparisons show that the SRBTL test loop core is suitable to extract experimental data of water-based nanofluids for using them as coolant in the VVER-1000 reactor.

Effect of Rotational Speed Variation on the Flow Characteristics in the Rotor-Stator System Cavity

In this paper, to study the effect of dynamic and static interference of clearance flow in fluid machinery caused by changes in rotational speed, the model was simplified to a rotor-stator system cavity flow. Investigating the flow characteristics in the cavity by changing the rotor speed of the rotor-stator system is of considerable significance. ANSYS-CFX was applied to numerically simulate the test model and the results were compared with the experimental results of the windage torque of the rotor-stator system. The inlet flow rate and geometric model remained unchanged. With an increase in the rotating Reynolds number, the shear stress on the rotor wall gradually increased, and the maximum gradient was within l* < 0.15. In addition to the shear stress, the tangential Reynolds stress Rrθ contributed partly to the torque on the rotor wall. The swirling vortex formed by entrainment in the cavity of the rotor-stator system tended to separate at ReΦ= 3.53 × 106. As the rotating Reynolds number continued to increase, the secondary vortex finally separated completely. The strength of the vortex in the rotor turbulent boundary layer decreased with an increase in the rotating speed, but the number of vortex cores increased with the increase of speed. Depending on the application of the fluid machine, controlling the rotating speed within a reasonable range can effectively improve the characteristics of the clearance flow.