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Records with Keyword: Computational Fluid Dynamics
26. LAPSE:2023.35122
MCNP and CFD Modeling for Potential High-Power Configuration of Missouri S&T Reactor
April 28, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, high power configuration, MCNP, neutron flux spectrum, reactor design
Utilization of nuclear research reactors is of high importance for education and training, research and development, and many other applications. However, less effective utilization encountered in research reactors is mainly due to limitations in power levels and related experimental facilities. Such limitations, however, have led different global owners of research reactors to consider upgrading the power levels of their reactors to accommodate the increase in utilization demands. To consider upgrading the power levels of research reactors without replacing major components, a pair of essential analyses must be performed, namely the neutronic evaluation of nuclear fission and thermal-hydraulic evaluation for heat removal from the reactor core. In this work, a conceptual upgrade to the core design and configuration of MSTR, or Missouri University of Science and Technology Reactor (200 kilowatts (kW)), is demonstrated. The conceptual design of the MSTR high-power configuration (MSTR-HPC... [more]
27. LAPSE:2023.35114
Modeling Strategies for Crude Oil-Induced Fouling in Heat Exchangers: A Review
April 28, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, crude oil, fouling, heat exchanger, Modelling, thermal-hydraulic
Semi-empirical fouling models have proven more effective in predicting the fouling behavior of crude oils in heat exchangers. These models have aided refineries in optimizing operating conditions to minimize or eliminate fouling in preheat exchangers. Despite their complexity, the models continue to improve in approximating real behavior by taking into account previously neglected aspects. This paper summarizes these findings from various studies along with highlighting different factors which were considered to enhance the predictability of the models. A critical analysis is presented to emphasize that activation energy in the deposition term varies depending on the physical processes involved and may not conform to the precise definition of activation energy. Two primary modeling approaches for crude oil fouling have emerged, i.e., deterministic and threshold models. Threshold models have gained more attention due to their fewer adjustable parameters. The stability or compatibility o... [more]
28. LAPSE:2023.35066
Numerical Investigation of Air Flow in Goaf While Mapping Its Flow Parameters
April 28, 2023 (v1)
Subject: Modelling and Simulations
Keywords: air flow velocity, Computational Fluid Dynamics, numerical model, permeability, porosity
Recent work has presented a numerical model of a longwall ventilated by a U-system, considering the real shape of an adjacent goaf in addition to parameters characterizing the distribution of porosity and permeability. Analogous distributions are used in the two-dimensional model implemented in VentZroby software. A comparison of the results of the three-dimensional flow calculations with the two-dimensional calculations can be used to verify the simpler description and evaluate the impact of simplifications on the simulation results. Air flow calculations were carried out using the selected turbulence model. The obtained results present the possibility of conducting extensive numerical calculations for flow problems in underground mines, considering more precise descriptions and the interpretation of the calculation results carried out using a simpler description.
29. LAPSE:2023.35031
Simulation Study of Hydrodynamic Conditions in Reaction Cell for Cement Biomineralization Using Factorial Design and Computational Fluid Dynamics: Prospects for Increased Useful Life of Concrete Structures and Energetic/Environmental Benefits
April 28, 2023 (v1)
Subject: Planning & Scheduling
Keywords: aeration, biomineralization, Computational Fluid Dynamics, concrete, energetic benefits, planning of experiments
Studies have reported the incorporation of microorganisms into cement to promote the formation of calcium carbonate in cracks of concrete, a process known as biomineralization. The paper aims to improve the process of the cascade system for biomineralization in cement by identifying the best hydrodynamic conditions in a reaction cell in order to increase the useful life of concrete structures and, therefore, bring energy and environmental benefits. Two central composite rotatable designs were used to establish the positioning of the air inlet and outlet in the lateral or upper region of the geometry of the reaction cell. The geometries of the reaction cell were constructed in SOLIDWORKS®, and computational fluid dynamics was performed using the Flow Simulation tool of the same software. The results were submitted to statistical analysis. The best combination of meshes for the simulation was global mesh 4 and local mesh 5. The statistical analysis applied to gas velocity and pressure re... [more]
30. LAPSE:2023.34987
Improving the Efficiency of the Blow-Jet WEC
April 28, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Blow-Jet, Computational Fluid Dynamics, Renewable and Sustainable Energy, wave energy converter
Establishing a renewable marine energy industry demands the development of high-efficiency devices that capture as much energy as possible. The Blow-Jet is a wave energy converter mainly composed of a sloping conical channel in the shape of a brass tube, which concentrates the waves at its widest part and expels a jet of water at its narrow upper end through an orifice that can be turbined. The device has no moving parts and great flexibility in its placement. This research presents an improvement of its geometry, increasing efficiency by minimizing undesired hydrodynamic interactions. The performance of the Blow-Jet was characterized using 3D numerical modeling and laboratory tests in a wave flume. Sixteen geometric configurations of the Blow-Jet were numerically tested, and that showing the best performance was 3D printed and assessed experimentally. The twofold objective was to evaluate the performance of the new Blow-Jet geometry and to validate a numerical tool for further geometr... [more]
31. LAPSE:2023.34983
Uncertainty Quantification Analysis of Exhaust Gas Plume in a Crosswind
April 28, 2023 (v1)
Subject: Numerical Methods and Statistics
Keywords: Computational Fluid Dynamics, exhaust plume in crosswind, uncertainty quantification
The design of naval exhaust funnels has to take into account the interaction between the hot gases and topside structures, which usually includes critical electronic devices. Being able to predict the propagation trajectory, shape and temperature distribution of an exhaust gas plume is highly strategic in different industrial sectors. The propagation of a stack plume can be affected by different uncertainty factors, such as those related to the wind flow and gas flow conditions at the funnel exit. The constant growth of computational resources has allowed simulations to gain a key role in the early design phase. However, it is still difficult to model all the aspects of real physical problems in actual applications and, therefore, to completely rely upon the quantitative results of numerical simulations. One of the most important aspects is related to input variable uncertainty, which can significantly affect the simulation result. With this aim, the discipline of Uncertainty Quantific... [more]
32. LAPSE:2023.34957
Optimisation of a Multi-Element Airfoil for a Fixed-Wing Airborne Wind Energy System
April 28, 2023 (v1)
Subject: Modelling and Simulations
Keywords: aerodynamic design, airborne wind energy, Computational Fluid Dynamics, Genetic Algorithm, MSES, multi-element airfoil, OpenFOAM, optimisation
Airborne wind energy systems benefit from high-lift airfoils to increase power output. This paper proposes an optimisation approach for a multi-element airfoil of a fixed-wing system operated in pumping cycles to drive a drum-generator module on the ground. The approach accounts for the different design objectives of the tethered kite’s alternating production and return phases. The airfoil shape is first optimised for the production phase and then adapted for the requirements of the return phase by modifying the flap setting. The optimisation uses the multi-objective genetic algorithm NSGA-II in combination with the fast aerodynamic solver MSES. Once the optimal shape is determined, the aerodynamic performance is verified through CFD RANS simulations with OpenFOAM. The resulting airfoil achieves satisfactory performance for the production and return phases of the pumping cycles, and the CFD verification shows a fairly good agreement in terms of the lift coefficient. However, MSES signi... [more]
33. LAPSE:2023.34359
Transient Thermal Analysis of a Li-Ion Battery Module for Electric Cars Based on Various Cooling Fan Arrangements
April 25, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, electric vehicle, lithium-ion battery, thermal-electrochemical coupled
This paper presents a three-dimensional modeling approach to simulate the thermal performance of a Li-ion battery module for a new urban car. A single-battery cell and a 52.3 Ah Li-ion battery module were considered, and a Newman, Tiedemann, Gu, and Kim (NTGK) model was adopted for the electrochemical modeling based on input parameters from the discharge experiment. A thermal−electrochemical coupled method was established to provide insight into the temperature variations over time under various discharge conditions. The distribution temperature of a single-battery cell was predicted accurately. Additionally, in a 5C discharge condition without a cooling system, the temperature of the battery module reached 114 °C, and the temperature difference increased to 25 °C under a 5C discharging condition. This condition led to the activation of thermal runaway and the possibility of an explosion. However, the application of a reasonable fan circulation and position reduced the maximum temperat... [more]
34. LAPSE:2023.34334
A Design of the Compression Chamber and Optimization of the Sealing of a Novel Rotary Internal Combustion Engine Using CFD
April 25, 2023 (v1)
Subject: Modelling and Simulations
Keywords: combustion chamber, compression chamber, Computational Fluid Dynamics, rotary engine, SARM, sealing
The current paper investigates two particular features of a novel rotary split engine. This internal combustion engine incorporates a number of positive advantages in comparison to conventional reciprocating piston engines. As a split engine, it is characterized by a significant difference between the expansion and compression ratios, the former being higher. The processes are decoupled and take place simultaneously, in different chambers and on the different sides of the rotating pistons. Initially, a brief description of the engine’s structure and operating principle is provided. Next, the configuration of the compression chamber and the sealing system are examined. The numerical study is conducted using CFD simulation models, with the relevant assumptions and boundary conditions. Two parameters of the compression chamber were studied, the intake port design (initial and optimized) and the sealing system size (short and long). The best option was found to be the combination of the op... [more]
35. LAPSE:2023.34282
Comparative Numerical Analysis on Vertical Wind Turbine Rotor Pattern of Bach and Benesh Type
April 25, 2023 (v1)
Subject: Modelling and Simulations
Keywords: 3D modeling, air flow, Bach type, Benesh type, Computational Fluid Dynamics, rotor, wind action, wind turbine
In this work, 3D models in classic configuration of Bach and Benesh rotor type, as well as models with modified blade pattern geometry were analyzed from the air circulation point of view inside the rotor enclosure in order to identify the operating parameters differences according to rotor geometric modified configuration. Constructive design aspects are presented, as well as results obtained from the virtual model analysis in terms of circulation velocity and pressure values which enhance rotor operation related to torque and power coefficients. The rotors design pattern is made according to previous results obtained by different researchers who have performed numerical analysis on virtual models and tests on the experimental rotor models using the wind tunnel. The constructive solutions are describing two-bladed rotor models, in four new designed constructive variants and analyzed using ANSYS CFX. The air velocity specific values, static and total pressure recorded at the rotor blad... [more]
36. LAPSE:2023.34212
Optimized Design of a Swirler for a Combustion Chamber of Non-Premixed Flame Using Genetic Algorithms
April 25, 2023 (v1)
Subject: Modelling and Simulations
Keywords: combustion, Computational Fluid Dynamics, experimental validation, genetic algorithms, optimized, recirculation, swirler
Recirculation in a combustion chamber is required for stabilizing the flame and reducing pollutants. The swirlers can generate recirculation in a combustion chamber, inducing a swirling flow that breaks vorticity and improves the mixing of air and fuel. The swirl number (Sn) is related to the formation of recirculation in conditions of high-intensity flows with Sn > 0.6. Thus, the optimized design of a swirler is necessary to generate enough turbulence that keeps the flame stable. We present the optimized design of a swirler considering the main parameters for a non-premixed combustion chamber. This optimization is made with genetic algorithms to ensure the generation of a recirculation zone in the combustion chamber. This recirculation phenomenon is simulated using computational fluid dynamics (CFD) models and applying the renormalization group (RNG) k-ε turbulence method. The chemistry is parameterized as a function of the mixture fraction and dissipation rate. A CFD comparison of a... [more]
37. LAPSE:2023.34138
Review of Wind Turbine Icing Modelling Approaches
April 25, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, icing simulation, modelling of ice accretion, wind turbine icing
When operating in cold climates, wind turbines are vulnerable to ice accretion. The main impact of icing on wind turbines is the power losses due to geometric deformation of the iced airfoils of the blades. Significant energy losses during the wind farm lifetime must be estimated and mitigated. Finding solutions for icing calls on several areas of knowledge. Modelling and simulation as an alternative to experimental tests are primary techniques used to account for ice accretion because of their low cost and effectiveness. Several studies have been conducted to replicate ice growth on wind turbine blades using Computational Fluid Dynamics (CFD) during the last decade. While inflight icing research is well developed and well documented, wind turbine icing is still in development and has its peculiarities. This paper surveys and discusses the models, approaches and methods used in ice accretion modelling in view of their application in wind energy while summarizing the recent research fin... [more]
38. LAPSE:2023.34015
Numerical Investigation of the Performance of a Submersible Pump: Prediction of Recirculation, Vortex Formation, and Swirl Resulting from Off-Design Operating Conditions
April 24, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, intake structure, mixed-flow pumps, performance, Q-H, sumps
Like any other turbomachinery, it is essential that the hydraulic behavior and performance of mixed-flow pumps are evaluated way in advance prior to manufacturing. Pump performance relies heavily on the proper design of the intake structure. Intake structures should be accurately designed in order to minimize and avoid unnecessary swirl and vortex formations. Ensuring the optimum performance condition as well as predicting how a particular intake structure affects the efficiency of the pump often requires either physical model studies or theoretical evaluations. Unfortunately, physical models are costly, time-consuming, and site-specific. Conversely, design and performance predictions using a theoretical approach merely gives performance values or parameters, which are usually unable to determine the root cause of poor pump performance. This study evaluates the viability of using Computational Fluid Dynamics (CFD) as an alternative tool for pump designers and engineers in evaluating pu... [more]
39. LAPSE:2023.33910
Numerical Study and Experimental Validation of Skim Milk Drying in a Process Intensified Counter Flow Spray Dryer
April 24, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, counter-current mechanism, experimental validation, Process Intensification, REA, skim milk, spray drying
This research presents 3D steady-state simulations of a skim milk spray drying process in a counter-current configuration dryer. A two-phase flow involving gas and discrete phase is modeled using the Eulerian−Lagrangian model with two-way coupling between phases. The drying kinetics of skim milk is incorporated using the Reaction Engineering Approach. The model predictions are found to be in accordance with the experimental temperature measurements with a maximum average error of 5%. The validated computational model is employed further to study the effects of nozzle position, initial spray Sauter Mean Diameter (SMD), air inlet temperature, and feed rate on the temperature and moisture profiles, particle impact positions, drying histories, and product recovery at the outlet. The location of the nozzle upwards (≈23 cm) resulted in maximum product recovery and increased the mean particle residence time at the outlet. A similar trend was observed for the highest feed rate of 26 kg/h owing... [more]
40. LAPSE:2023.33831
Measurement and Simulation of Flow in a Section of a Mine Gallery
April 24, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, laser scanning, numerical model geometry
Research work on the air flow in mine workings frequently utilises computer techniques in the form of numeric simulations. However, it is very often necessary to apply simplifications when building a geometrical model. The assumption of constant model geometry on its entire length is one of the most frequent simplifications. This results in a substantial shortening of the geometrical model building process, and a concomitant shortening of the time of numerical computations; however, it is not known to what extent such simplifications worsen the accuracy of simulation results. The paper presents a new methodology that enables precise reproduction of the studied mine gallery and the obtaining of a satisfactory match between simulation results and in-situ measurements. It utilises the processing of data from laser scanning of a mine gallery, simultaneous multi-point measurements of the velocity field at selected gallery cross-sections, unique for mine conditions, and the SAS turbulence mo... [more]
41. LAPSE:2023.33792
Hydrodynamic Efficiency Analysis of a Flexible Hydrofoil Oscillating in a Moderate Reynolds Number Fluid Flow
April 24, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, deformable hydrofoil, fluid-structure interactions, NACA0015, oscillating hydrofoil, renewable marine energy
The paper focuses on the study of a semi-activated system, based on a combination of two movements of forced pitching and free-heaving motion. Therefore, quantifying with accuracy the hydrodynamic forces applied on the hydrofoil seems to be crucial. This is investigated throughout a numerical analysis of the hydrofoil dynamics. The deformable structure is oscillating in a low-Reynolds number flow. In this study, a hydrofoil animated by a combined forced pitching and heaving movements is considered. Various materials of the hydrofoil structure are studied, from the rigid material to a more flexible one. A partitioned implicit coupling approach is applied in order to consider the Fluid-Structure Interaction (FSI) effects, while the Navier−Stokes equations are solved using the Arbitrary Lagrangian−Eulerian (ALE) method. Both the viscous incompressible Navier−Stokes equations and the elasticity equation are solved using finite volume method. The study is based on the analysis of the hydrod... [more]
42. LAPSE:2023.33778
Multiparameter Optimization of Thrust Vector Control with Transverse Injection of a Supersonic Underexpanded Gas Jet into a Convergent Divergent Nozzle
April 24, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, engine, jet, nozzle, Optimization, thrust vector control
The optimal design of the thrust vector control system of solid rocket motors (SRMs) is discussed. The injection of a supersonic underexpanded gas jet into the diverging part of the rocket engine nozzle is considered, and multiparameter optimization of the geometric shape of the injection nozzle and the parameters of jet injection into a supersonic flow is developed. The turbulent flow of viscous compressible gas in the main nozzle and injection system is simulated with the Reynolds-averaged Navier−Stokes (RANS) equations and shear stress transport (SST) turbulence model. An optimization procedure with the automatic generation of a block-structured mesh and conjugate gradient method is applied to find the optimal parameters of the problem of interest. Optimization parameters include the pressure ratio of the injected jet, the angle of inclination of the injection nozzle to the axis of the main nozzle, the distance of the injection nozzle from the throat of the main nozzle and the shape... [more]
43. LAPSE:2023.33747
Investigations of Flow and Heat Transfer Characteristics in a Channel Impingement Cooling Configuration with a Single Row of Water Jets
April 24, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, confined array jets, heat transfer coefficient, jet impingement
The present study experimentally and numerically investigates the effect of channel height on the flow and heat transfer characteristics of a channel impingement cooling configuration for various jet Reynolds numbers in the range of 2000−8600. A single array consisting of eleven jets with 0.8 mm diameter injects water into the channel with 2 mm width at four different channel heights (3, 4, 5, and 6 mm). The average heat transfer coefficients at the target surface are measured by maintaining a temperature difference between the jet exit and the target surface in the range of 15−17 °C for each channel height. The experimental results show the average heat transfer coefficient at the target surface increases with the jet Reynolds number and decreases with the channel height. An average Nusselt number correlation is developed based on 85 experimentally measured data points with a mean absolute error of less than 4.31%. The numerical simulation accurately predicts the overall heat transfer... [more]
44. LAPSE:2023.33561
A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: combustion, Computational Fluid Dynamics, cycle-to-cycle variations, internal combustion engine, RANS simulation
Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier−Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are ta... [more]
45. LAPSE:2023.33472
Surrogate-Based Optimization of Horizontal Axis Hydrokinetic Turbine Rotor Blades
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, design, hydrokinetic turbine, marine turbine, surrogate-based optimization
A design method was developed for automated, systematic design of hydrokinetic turbine rotor blades. The method coupled a Computational Fluid Dynamics (CFD) solver to estimate the power output of a given turbine with a surrogate-based constrained optimization method. This allowed the characterization of the design space while minimizing the number of analyzed blade geometries and the associated computational effort. An initial blade geometry developed using a lifting line optimization method was selected as the base geometry to generate a turbine blade family by multiplying a series of geometric parameters with corresponding linear functions. A performance database was constructed for the turbine blade family with the CFD solver and used to build the surrogate function. The linear functions were then incorporated into a constrained nonlinear optimization algorithm to solve for the blade geometry with the highest efficiency. A constraint on the minimum pressure on the blade could be set... [more]
46. LAPSE:2023.33459
Numerical Simulation of a Novel Dual Layered Phase Change Material Brick Wall for Human Comfort in Hot and Cold Climatic Conditions
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Ansys, buildings, Computational Fluid Dynamics, latent heat, phase change material (PCM), phase change simulations, summer and winter, thermal energy storage (TES)
Phase change materials (PCMs) have a large number of applications for thermal energy storage (TES) and temperature reduction in buildings due to their thermal characteristics and latent heat storage capabilities. The thermal mass of typical brick walls can be substantially increased using a suitable PCM primarily based on phase change temperature and heat of fusion for different weather conditions in summer and winter. This study proposed a novel dual-layer PCM configuration for brick walls to maintain human comfort for hot and cold climatic conditions in Islamabad, Pakistan. Numerical simulations were performed using Ansys Fluent for dual PCMs layered within a brick wall for June and January with melting temperatures of 29 °C and 13 °C. This study examined and discussed the charging and discharging cycles of PCMs over an extended period (one month) to establish whether the efficacy of PCMs is hindered due to difficulties in discharging. The results show that the combined use of both P... [more]
47. LAPSE:2023.33403
Validation of Modified Algebraic Model during Transitional Flow in HVAC Duct
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, HVAC duct, numerical simulation, OpenFOAM, PTV, steady-state transitional flow
Airflow occurring in a ventilation duct is characterized by low velocity and hence low Reynolds number. In these conditions, either a laminar, transitional or turbulent flow will occur. Different flow conditions result in different values of the friction coefficient. To achieve the transitional flow in numerical simulation, a modified algebraic model for bypass transition (modified k−ω) was used. Numerical simulation was validated using Particle Tracking Velocimetry (PTV) in the circular channel. The modified algebraic model consists of only two partial differential equations, which leads to much faster calculation than the shear stress transport model. Results of the modified algebraic model are largely consistent with either the measurement and shear stress transport model considering laminar and transitional flow. Consistency slightly decreased in turbulent flow in relation to the model using shear stress transport method.
48. LAPSE:2023.33368
Effect of Roof Cooling and Air Curtain Gates on Thermal and Wind Conditions in Stadiums for Hot Climates
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: air curtain, building energy simulation, Computational Fluid Dynamics, hot climates, stadium cooling, thermal comfort
To host the 2022 FIFA World Cup, Qatar is facing the greatest challenge in balancing the energy consumptions for cooling the stadiums and the thermal comfort for both players and spectators. Previous studies have not considered using a combined configuration of air curtain and roof cooling supply slot in stadiums to prevent the infiltration of outside hot air and reduce the cooling system’s energy consumption. This paper presents a Computational Fluid Dynamics (CFD) study of thermal and wind modeling around a baseline stadium and simulates the cooling scenarios of air curtains and roof cooling along with the energy consumption estimations for the World Cup matches using Building Energy Simulation (BES). Sensitivity analysis of different supply speeds and supply temperatures of air curtain gates and roof cooling was carried out, and the results showed that scenario six, which provides supply air of 25 m/s and 20 m/s at the roof and air curtain gates with a supply temperature of 10 °C, d... [more]
49. LAPSE:2023.33313
Investigations of Rake and Rib Structures in Sand Traps to Prevent Sediment Transport in Hydropower Plants
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, hydropower, multiphase, particle, sand trap, sediment transport
In order to increase the lifespan of hydraulic turbines in hydropower plants, it is necessary to minimize damages caused by sediment erosion. One solution is to reduce the amount of sediments by improving the design of sand trap. In the present work, the effects on sand trap efficiency by installing v-shaped rake structures for flow distribution and rib structures for sediment trapping is investigated numerically using the SAS−SST turbulence model. The v-shaped rake structures are located in the diffuser near the inlet of the sand trap, while the ribs cover a section of the bed in the downstream end. Three-dimensional models of the sand trap in Tonstad hydropower plant are created. The present study showed that integrating rib type structure can reduce the total weight of sediments escaping the sand trap by 24.5%, which leads to an improved sand trap efficiency. Consequently, the head loss in the sand trap is increased by 1.8%. By additionally including the v-shaped rakes, the total we... [more]
50. LAPSE:2023.33212
Study of the Influence of the Lack of Contact in Plate and Fin and Tube Heat Exchanger on Heat Transfer Efficiency under Periodic Flow Conditions
April 21, 2023 (v1)
Subject: Modelling and Simulations
Keywords: Computational Fluid Dynamics, heat exchanger, plate-fin tube, tube-fin contact
Plate fin-tube heat exchangers are widely used in air conditioning and refrigeration systems and other industry fields. Various errors made in the manufacturing process can result in the formation of an air gap between the tube and fin. Several numerical simulations were carried out for a symmetric section of plate fin-tube heat exchanger to study the influence of air gap on heat transfer under periodic flow conditions. Different locations and sizes of an air gap spanning 1/2 circumference of the tube were considered for the range of airflow velocities. Velocity and temperature fields for cases with air gap were compared with ideal thermal contact cases. Blocking of heat flow by the gap leads to the reduction of heat transfer rate. Fin discontinuity in the front of the tube causes the smallest reduction of the heat transfer rate in comparison to the ideal tube-fin contact, especially for thin slits. The rear gap position is the worst in the smallest gap range. Therefore, reversing the... [more]