Papers by Keyword: Computational Fluid Dynamics (CFD)

Abstract: This paper presents the thermal analysis of a passive solar dryer for paddy rice drying. The dryer, which was designed with a capacity of two tonnes of paddy rice per batch, was deployed and test run in a rural agrarian community. The thermal analysis of the dryer was carried out using a computational fluid dynamic (CFD) model of the system. The system’s two-dimensional continuity, momentum, and energy equations were developed subject to suitable boundary and initial conditions. The CFD model was executed for a day for which the available experimental data was 11 MJ/day of solar irradiance, mean wind velocity of 0.0186 m/s, and mean ambient temperature of 20°C. The simulation was carried out for nine different mesh sizes ranging from extremely coarse (5378 domain elements with 378 boundary nodes) to extremely fine (56153 domain elements with 1385 boundary nodes). The simulation time for the extremely coarse mesh size was 52.32 minutes, while that for the extremely fine was 180.95 minutes. The temperature, velocity, and pressure distributions of the drying air within the drying chamber were determined for each mesh size. From these, their mean values at given times and the day were calculated. It was found that the finer mesh sizes (33134 domain elements with 1004 boundary nodes to 56153 domain elements with 1385 boundary nodes) gave the same results which agreed with experimental data. The results show that the drying process is effective in harnessing solar energy to heat the chamber with the chamber temperature reaching a maximum temperature of approximately 336 K and an average drying chamber temperature of 315.6K. Possible design improvements to the system are suggested, including the incorporation of forced air circulation and phase change material energy storage.

Abstract: The diverse flow patterns observed in open channels with weir-type structures are common in natural environments such as rivers. However, the complex flow dynamics in these settings remain only partially understood. To address this research gap, a rectangular sharp-crested weir with variable geometric ratios crest heights (H/P) and widths (H/B) was numerically analyzed using CFD modeling in ANSYS Fluent. The primary objective of this study is to provide detailed numerical insights into flow characteristics over sharp-crested weirs with varying H/P and H/B, where H represents the head over the weir, P the weir height, and B the weir width. Discharge capacity and turbulent intensity profiles and contours were generated and compared across four different cases (Cases A-D). The findings demonstrate that changes in geometric parameters significantly influence flow behavior, particularly by affecting discharge rates and turbulence intensity. These results reveal the presence of complex, wide-ranging flow motions similar to those observed in natural open channels, highlighting the impact of weir geometry on overall flow dynamics.

Abstract: In order to protect coastal regions effective natural strategies are needed because of increasing intensity and frequency of tsunami and flood events. This study aims to explore the role of coastal vegetation for mitigating the tsunami and flood induced currents. To simulate interaction between tsunami waves and coastal vegetation, a detailed model is developed with the help of ANSYS FLUENT by using Computational Fluid Dynamics (CFD) techniques in this study. Critical flow characteristic such as velocity is the focus of simulations. To see that how the tree structure effects the reduction of tsunami and flood currents, the model incorporated different configurations of coastal vegetation (Linear and Staggered Arrangement). In case of linear arrangement, the highest increased value of velocity has found to be 32% of inlet velocity. On the other hand, in case of staggered arrangement the highest increased value of velocity has found to be 39.6% of inlet velocity.

Abstract: Vertical axis wind turbines (VAWTs) represent a significant advancement in harnessing wind energy, offering enhanced efficiency and adaptability. Their ability to capture wind from any direction makes them particularly suitable for urban environments and areas with unpredictable wind patterns.This study describes the design and its optimization for savonius vertical axis wind turbine for application in efficient energy generation on highways and our objective is to optimize the key parameters of design, including the blade arc angle , overlap ratio, and tip speed ratio to identify the best set of design configuration using Numerical Modelling done with the help of Computational Fluid Dynamics (CFD) Study of Turbine Blade Profile and enhance efficiency indicators like power and torque coefficient to achieve an optimal level of performance. The Outcomes and key findings of this study suggested that a rotor configuration with (Ø = 130°, O_R = 0.15, TSR = 1) demonstrated the highest C_P of 0.473 (47.3% wind to mechanical power conversion) and a C_T of 0.255 (25.5% wind to torque generation), these values suggests an enhanced performance of turbine in terms of capturing wind energy and generating torque, this provides evidence for consideration of these results while defining design criteria for the vertical axis wind turbine suitable to our application.

Abstract: In this paper, the cooling of a passenger car alternator’s stator winding is investigated with the help of computational fluid dynamics. The main heat sources are determined to be the stator winding and the diodes. Their respective heat loss is calculated and applied in the CFD software. In the first step, the CAD model is simplified in a way to enable a fine-quality numerical mesh generation, while keeping the important geometric features that could have significant effects on the results. In the next step, independence studies are carried out for the mesh, time-step size, and flow volume. A comparison is also presented between the steady “frozen rotor” approach and the transient “moving mesh” approach.After conducting the transient simulations at multiple operating points, the simulation results are evaluated with the help of contours and quantitative properties. An experimental comparison is presented which shows a good correlation between the simulated and the measured data, furthermore, the possible reasons for the deviations are eventually discussed. Finally, the benefits of the future applications of the simulation model are introduced briefly.

Abstract: This work investigates how the configuration of the geometric parameters of a radial crystallizer influences the results of the crystallization of lovastatin by antisolvent and using a multi-scale computational fluid dynamics (CFD) model. The OPENFOAM open-source software uses macro and micromixing expressions for flow, and complete energy and population equilibrium equations during nucleation and crystal growth. The model is based on the Reynolds-Averaged-Navier-Stokes (RANS) equation, along with a multi-environment probability density function (PDF) model and the spatially semi-discretized population equilibrium equation, operating a high-resolution finite volume method. The variation crystallizer construction parameters provided another crystallizer design, and analyses demonstrated improved performance and effects on crystal distribution.

Abstract: Lubrication is one of the important factors for a journal bearing to function well. Therefore, the use of bio-lubricants such as coconut oil and vegetable oil are highly recommended for their high level of biodegradability to reduce the risk of environmental pollution. Vegetable oil like coconut oil has a great lubricating quality including low friction coefficient and improved oxidation stability which is very suitable to be used as a lubricant. The performance assessment of journal bearings utilizing coconut oil as a bio-lubricant and varying angular velocity and eccentricity ratio will be the main emphasis of this study. The behavior of the journal bearing with coconut oil as the lubricant will be examined using the Computational Fluid Dynamics (CFD) program, ANSYS Fluent. Using ANSYS Fluent, the pressure distribution of pure coconut oil is analytically studied. To evaluate the efficacy of each lubricant with a varied value of angular velocity utilized by the journal in journal bearings, average viscosity, viscosity index, and produced maximum pressure can be discovered under the lubrication of the journal bearing. Using the values of angular velocity with the same value of dynamic viscosity and density as properties for the coconut oil were used to run the simulation for the journal bearing. The result obtained from the simulation for eccentricity ratio of 0.2 with an angular velocity of 5000rpm is 205926.1 meanwhile the result for eccentricity ratio of 0.8 with same angular velocity value is 9661441. Each result signifies those different value of angular velocity with different value of eccentricity ratio that effects the bearing design itself occurs different result.

Abstract: An ambient air vaporizer (AAV) is an industrial heat exchanger equipment used in the vaporization process of liquefied gases before supplying to consumers. AAV utilizes the simple heat transfer principle that uses surrounding ambient air to vaporize the liquefied gases. Liquefied Natural Gas (LNG) is one of the liquefied gases commonly associated with AAV applications. Due to a significant temperature difference between cryogenic fluid of LNG and ambient air, frost formation is inevitable to reduce the heat transfer rate. Fins geometry contributes a substantial impact on the performance of AAV and is the main element of heat transfer for AAV. This study aims to design a model of an AAV with a star 6-finned tube vaporizer with hexagon shape and to simulate the fluid flow on the vaporizer model to demonstrate the LNG vaporization process. The hexagon vaporizer model is designed using Solidworks, and heat transfer model is simulated using computational fluid dynamics (CFD) tool, Ansys Fluent solver. Parameters such as fin geometry, LNG flowrate and wind speed were referred from previous studies. Methane and air are assumed as working fluids inside and outside of the vaporizer model. Wind temperatures of 300K (27°C), 303K (30°C), and 306K (33°C) are utilized in the simulation process based on geometrical weather in Malaysia. In the simulation model, methane entered from the bottom of the tube, while air entered horizontally at x-direction from the right side. The temperature contour shows that as the temperature of methane that flowed inside the tube increased as it entered the tube, the air temperature reduced as it entered and flowed passes through the finned tube. The analysis from the simulation model shows that higher air temperature with substantial wind speed can increase the outlet temperature of methane (LNG), thus improving the performance of AAV.

Abstract: The Proton Exchange Membrane Fuel Cells (PEMFCs) performance is improved by flow field channel design. The flow field reactant distribution geometry on PEMFCs is primarily influenced by the perceived effect of pressure and transmission characteristics of reactant flow fields on the efficiency of fuel cells. Nutrients distributed in the biological branching structures systems found their optimum arrangement have more efficiently in each part. The flow fields design channels in polymer electrolyte membrane (PEM) fuel cells serve the same roles as nutrient transport systems in plants and animals, so bio-inspired flow fields design with a similar could maximize reactant transport efficiency and improve fuel cell performance. In this analysis, the lung channel design of a humane lung and a tree leaf bio-inspired flow field design is used for the flow fields of the anode and cathode bipolar plates. SOLIDWORKS produces a 3-D numerical CFD design for four new flow field pattern designs: leaf design, lung design, single-serpentine, and triple-serpentine. The model is simulated using ANSYS FLUENT-15.0 software to obtain pressure distributions in the flow field, concentration profiles of hydrogen on anode and oxygen on cathode channel, current flux density on the membrane, water concentration on the membrane, water generating in a cathode channel, the polarization curve and the power curve. It is observed that bio-inspired leaf and lung design performs better than serpentine flow field channels. So, leaf and lung design can be used in mopeds and automobiles to enhance electrical efficiency and at the same time reduce fuel consumption.

Abstract: Numerical simulations of a billet heating furnace with direct flame impingement operating in a metallurgical plant were carried out and the results compared to measurements obtained in an industrial environment. The transport equations for mass, momentum, energy and mass of chemical species in reactive flow were computed with the use of ANSYS FLUENT. Turbulence, combustion and radiation were modeled using, respectively, the realizable k-ε model, the finite-rate/eddy-dissipation model and the finite volume scheme. The model was used to simulate the furnace operating under the conditions that occurred during an energy audit carried out at an industrial facility (413 kW firing rate and 80% excess air). The predicted furnace efficiency, 72.5%, is in very good agreement with the one obtained in the energy audit (0.4% difference). The flue gas temperature at the end of the second preheating zone was measured during the energy audit and its value compared to the one predicted. In this case, the agreement between measurements and simulation is not so satisfactory (23% difference). This paper presents the validation of a CFD model of a direct-flame impingement furnace for billet heating in a full-scale industrial situation, which was not previously published, and opens the way for more simulations and detailed studies of the phenomena that occur inside this type of furnace.