Records with Keyword: Computational Fluid Dynamics
Showing records 61 to 85 of 472. [First] Page: 1 2 3 4 5 6 7 8 Last
Energy Harvesting by a Novel Substitution for Expansion Valves: Special Focus on City Gate Stations of High-Pressure Natural Gas Pipelines
Yahya Sheikhnejad, João Simões, Nelson Martins
March 23, 2023 (v1)
Keywords: compressible turbulent flow, Computational Fluid Dynamics, design rules, energy harvesting, high-pressure methane, tesla turbine
A countless amount of energy has been wasted in all kinds of expansion valves (EV) in industries. In fact, EVs, including regulators, throttling valves, capillary tubes, etc., have been used to intentionally reduce the potential of carrier fluid. City gate stations (CGS) have been recognized as one of the important points with high potential for energy harvesting due to its function for regulating natural gas (NG) pressure by EV. In this study, Tesla turbine (TT) is introduced as a new candidate for substitution of EV, particularly those that have been employed in CGS on high-pressure NG pipelines, as well as those applications in which high-potential fluid must be reduced to a low-potential state to form a complete thermodynamic cycle or to be used at end-user equipment. Although harvesting energy is one of the hottest fields of science and engineering, there are few traces of research on using a TT as an alternative for EVs, even for the industries possessing high-pressure lines. Thi... [more]
Analysis of the Influencing Factors on Oil Removal Efficiency in Large-Scale Flotation Tanks: Experimental Observation and Numerical Simulation
Qian Huang, Xueyuan Long
March 22, 2023 (v1)
Keywords: Computational Fluid Dynamics, flotation tank, gas bubble, oil droplet, oil removal efficiency
A modified computational fluid dynamic (CFD) model has been developed to obtain oil removal efficiency for oily wastewater treatment in large-scale flotation tanks. According to the investigation of oil droplet/bubble interactions in a flotation tank, a modified Bloom−Heindel model is used to calculate the collision and attachment efficiencies between oil droplets and bubbles. Effects of the gas flow rate, oil diameter and oil concentration on oil removal efficiency of flotation tank were analyzed experimentally. The application scope of this modified CFD model is evaluated using experimental results. In addition, the comparison between the existing model and the modified model demonstrates that this modified CFD model can make a good prediction for the separation performance of the flotation tank.
The Wave-to-Wire Energy Conversion Process for a Fixed U-OWC Device
Luana Gurnari, Pasquale G. F. Filianoti, Marco Torresi, Sergio M. Camporeale
March 22, 2023 (v1)
Keywords: Computational Fluid Dynamics, energy conversion chain, oscillating water column, porous medium, resonance condition, wave energy converter, wells turbine
Oscillating water column (OWC) devices, either fixed or floating, are the most common wave energy converter (WEC) devices. In this work, the fluid dynamic interaction between waves and a U-shaped OWC breakwater embedding a Wells turbine has been investigated through unsteady Computational Fluid Dynamic (CFD) simulations. The full-scale plant installed in the harbor of Civitavecchia (Italy) was numerically modeled. A two-dimensional domain was adopted to simulate the unsteady flow, both outside and inside the U-OWC device, including the air chamber and the oscillating flow inside the conduit hosting the Wells turbine. For the numerical simulation of the damping effect induced by the Wells turbine connected to the air chamber, a porous medium was placed in the computational domain, representing the conduit hosting the turbine. Several simulations were carried out considering periodic waves with different periods and amplitudes, getting a deep insight into the energy conversion process fr... [more]
Modelling of Passive Heat Removal Systems: A Review with Reference to the Framatome BWR Reactor KERENA: Part II
René Manthey, Frances Viereckl, Amirhosein Moonesi Shabestary, Yu Zhang, Wei Ding, Dirk Lucas, Christoph Schuster, Stephan Leyer, Antonio Hurtado, Uwe Hampel
March 22, 2023 (v1)
Keywords: Computational Fluid Dynamics, condensation, containment cooling condensers, emergency condensers, passive heat removal systems, system codes, two-phase flow instabilities
Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven by thermal gradients and gravitational force. This brings up new needs for performance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modeling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I dealt with numerical and experimental methods for modeling of condensation inside the emergency condenser and on the containment cooling condenser. This second part deals with boiling and two-phase flow instabilities.
Experimental and Numerical Study on the Cooling Performance of Fins and Metal Mesh Attached on a Photovoltaic Module
Jaemin Kim, Sangmu Bae, Yongdong Yu, Yujin Nam
March 22, 2023 (v1)
Keywords: Computational Fluid Dynamics, cooling fin, indoor test, metal mesh, passive cooling, photovoltaic module, solar energy
The electrical efficiency and durability of a photovoltaic (PV) cell degrades as its temperature increases. Accordingly, there have been continued efforts to control the cell temperature by cooling the PV module. Generally, passive PV cooling using heat sinks attached on the back of the PV module can improve the electrical efficiency. However, few experimental studies have evaluated the effect of the heat sink shape on PV cooling. Therefore, this study proposed a passive cooling technology using meshes made of iron and aluminum, and performed indoor tests using a solar simulator to analyze the cooling performance. The experimental results demonstrated that iron and aluminum meshes reduced the PV module temperature by approximately 4.35 °C and 6.56 °C, respectively. Additionally, numerical studies were performed using a computational fluid dynamics (CFD) simulation to compare the cooling fins and meshes. The numerical results showed that the cooling fins exhibited a better cooling perfo... [more]
Modelling of Passive Heat Removal Systems: A Review with Reference to the Framatome KERENA BWR Reactor: Part I
Amirhosein Moonesi Shabestary, Frances Viereckl, Yu Zhang, Rene Manthey, Dirk Lucas, Christoph Schuster, Stephan Leyer, Antonio Hurtado, Uwe Hampel
March 22, 2023 (v1)
Keywords: 1D codes, Computational Fluid Dynamics, condensation, containment cooling condensers, emergency condensers, passive heat removal systems
Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven by thermal gradients and gravitational force. This brings up new needs for performance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modelling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I deals with numerical and experimental methods for modelling of condensation inside the emergency condensers and on the containment cooling condenser while part II deals with boiling and two-phase flow instabilities.
Parameter Analysis of Savonius Hydraulic Turbine Considering the Effect of Reducing Flow Velocity
Jianjun Yao, Fengshen Li, Junhua Chen, Zheng Yuan, Wangeng Mai
March 22, 2023 (v1)
Keywords: basic parameters, Computational Fluid Dynamics, flow velocity reduction, power-efficient, Savonius-tpye hydrokinetic turbine
The Savonius-type hydraulic turbine, mainly known for its good self-starting properties and simple structure, not only has energy capturing characteristics but also has a certain effect on flow velocity reduction. Aside from ensuring energy capture efficiency, studying the effects of parameters on the flow velocity reduction capacity is of great significance for the protection of mariculture, as it can reduce the damage to cages and fishes. In this study, a computational fluid dynamics method was carried out to investigate the hydrodynamic characteristics and variations in the wake of a turbine. The accuracy of the simulation results was verified by experimental comparison. Firstly, the velocity contours and vectors were studied in detail to reveal the mechanism of the flow velocity reduction effect. Secondly, the velocity attenuation coefficient and relative attenuation length were formulated by the variation rule of the velocity field to evaluate the turbine reduction strength and ra... [more]
CFD Simulation of Defogging Effectivity in Automotive Headlamp
Michal Guzej, Martin Zachar
March 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, condensation, defogging, dew point, fogging, headlamp
In the past decade, the condensation of internal air humidity in automotive headlamps has become more prevalent than ever due to the increased usage of a new light source—LEDs. LEDs emit far less heat than previously-used halogen lamps, which makes them far more susceptible to fogging. This fogging occurs when the internal parts of the headlamp fall to a temperature below the dew point. The front glass is most vulnerable to condensation due to its direct exposure to ambient conditions. Headlamp fogging leads to a decrease in performance and the possibility of malfunctions, which has an impact not only on the functional aspect of the product’s use but also on traffic safety. There are currently several technical solutions available which can determine the effectivity of ventilation systems applied for headlamp defogging. Another approach to this problem may be to use a numerical simulation. This paper proposes a CFD (computational fluid dynamics) simulation with a slightly simplified 3D... [more]
An Investigation of the Influence of Gas Injection Rate Shape on High-Pressure Direct-Injection Natural Gas Marine Engines
Jingrui Li, Jietuo Wang, Teng Liu, Jingjin Dong, Bo Liu, Chaohui Wu, Ying Ye, Hu Wang, Haifeng Liu
March 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, high-pressure direct injection (HPDI), injection rate shape, low-speed engine, Natural Gas
High-pressure direct-injection (HPDI) natural gas marine engines are widely used because of their higher thermal efficiency and lower emissions. The effects of different injection rate shapes on the combustion and emission characteristics were studied to explore the appropriate gas injection rate shapes for a low-speed HPDI natural gas marine engine. A single-cylinder model was established and the CFD model was validated against experimental data from the literature; then, the combustion and emission characteristics of five different injection rate shapes were analyzed. The results showed that the peak values of in-cylinder pressure and heat release rate profiles of the triangle shape were highest due to the highest maximum injection rate, which occurred in a phase close to the top dead center. The shorter combustion duration of the triangle shape led to higher indicated mean effective pressure (IMEP) and NOx emissions compared with other shapes. The higher initial injection rates of t... [more]
Development of a Thermal Environment Analysis Method for a Dwelling Containing a Colonnade Space through Coupled Energy Simulation and Computational Fluid Dynamics
Tatsuhiro Yamamoto, Akihito Ozaki, Myonghyang Lee
March 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, ES, heat loss, large space
In building design, several approaches have been proposed for coupling computational fluid dynamics (CFD) and energy simulation (ES) to perform analyses of thermal environments. The unsteady analysis of thermal environments within buildings containing offices and colonnade spaces is difficult to perform using an ES that represents the space with a single mass point, owing to excessive predictive heat loss; therefore, CFD has typically been used instead. Although it is possible to divide the space into zones using ES, it leads to excessive predicted heat loss and the prediction of heat movement due to the influence of strong air currents, such as those associated with air conditioners. This behavior is observed because these zones are not detailed mesh divisions. To solve these problems, we proposed a method for calculating the ratio of heat contribution to zones that were pre-divided using CFD followed by the distribution of the total thermal load calculated by ES. In this study, we pr... [more]
Unsteady Simulation of Ignition of Turbulent Reactive Swirling Flow of Novel Design of Solid-Fuel Ramjet Motor
Omer Musa, Xiong Chen, Yingkun Li, Weixuan Li, Wenhe Liao
March 21, 2023 (v1)
Keywords: combustion characteristics, Computational Fluid Dynamics, propulsion, ramjet, solid fuel
This paper presents a numerical investigation of ignition and combustion stabilization of a novel design of a solid-fuel ramjet (SFRJ) motor with and without swirl flow. The proposed design includes two solid fuels, retaining the simple design of the classic SFRJ. Numerical simulations of unsteady, turbulent, reactive, and swirling flow coupled with solid-fuel pyrolysis have been performed using an in-house CFD solver. Experiments on SFRJ were conducted via a connected-pipe test facility to validate the developed code. Furthermore, the code was validated for chemical reactions, heat diffusion, and swirl flow by using benchmark test cases of shock-induced, semi-infinite plate, and dump combustor with swirl flow, respectively. Then, the proposed and classic designs were simulated for the same inflow conditions and configurations, and the results were analyzed and discussed. It is found that the mixing degree, reactant residence time, mass flux, ignition delay time, and regression rate im... [more]
CFD Computation of the H-Darrieus Wind Turbine—The Impact of the Rotating Shaft on the Rotor Performance
Krzysztof Rogowski
March 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, rotating shaft/tower, URANS, VAWTs
Aerodynamics of the Darrieus wind turbine is an extremely complex issue requiring the use of very advanced numerical methods. Additional structural components of this device, such as, for example, a rotating shaft disturb the flow through the rotor significantly impairing its aerodynamic characteristics. The main purpose of the presented research is to validate the commonly-used unsteady Reynolds averaged Navier−Stokes (URANS) approach with the shear stress transport (SST) k-ω turbulence model based on the particle image velocimetry (PIV) studies of a two-bladed rotor operating at the moderate tip speed ratio of 4.5. In the present numerical studies, a two-dimensional turbine rotor with a diameter of 1 m was considered. The following parameters were evaluated: instantaneous velocity fields; velocity profiles in the rotor shadow and aerodynamic blade loads. The obtained numerical results are comparable with the reference experimental results taken from the literature. The second purpose... [more]
Effects of the Current Direction on the Energy Production of a Tidal Farm: The Case of Raz Blanchard (France)
Van Thinh Nguyen, Alina Santa Cruz, Sylvain S. Guillou, Mohamad N. Shiekh Elsouk, Jérôme Thiébot
March 21, 2023 (v1)
Keywords: actuator disk, Computational Fluid Dynamics, misalignment, tidal energy converter, tidal farm
This study aims to investigate the influence of the current direction on the energy production of a tidal turbines array. It is based on a three-dimensional (3D) numerical simulation of the flow where the turbines are represented with actuator disks. The case study consists of modelling the energy extraction of a small array of turbines (staggered and aligned layouts) placed in the Raz Blanchard (Alderney Race, France). The simulations are performed with hydrodynamic data (current magnitude and direction) representative of a mean tide, with several resistance forces and ambient turbulence intensities. The influence of the current direction on the energy production is highlighted by comparing the simulations forced with the real current direction with those in which the angle of incidence between the incoming flow and the turbine’s axis is “switched off” (bi-directional flow). When the flow is aligned with the turbines’ axis (misalignment “switched off”), the staggered layout produces m... [more]
The Use of CFD for the Design and Development of Innovative Configurations in Regenerative Glass Production Furnaces
Carlo Cravero, Davide De Domenico
March 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, glass production plants, NOx reduction, thermal regenerator
The limitation of nitrogen oxides emissions is nowadays a challenge in several engineering fields. Recent European regulations have reduced the maximum NOx emissions and therefore forced the glass production sector to develop emission reduction strategies. Two different systems have been developed within the framework of the European LIFE project and are currently applied to glass regenerative furnaces: the Waste Gas Recirculation (WGR) and the Hybrid Air Staging (HyAS). The above systems are primary NOx reduction strategies because they both operate to control the combustion evolution. Both WGR and HyAS systems have been conceived with the extensive use of Computational Fluid Dynamics (CFD) models: design strategies for both systems have been developed based on the use of CFD and are currently under use by glass furnace designers. In the present work, the CFD procedures routinely used for the design of the above systems are described. The systems effectiveness, due to the harsh condit... [more]
Improving Performance of Simplified Computational Fluid Dynamics Models via Symmetric Successive Overrelaxation
Vojtěch Turek
March 21, 2023 (v1)
Keywords: Computational Fluid Dynamics, performance, preconditioning, symmetric successive overrelaxation
The ability to model fluid flow and heat transfer in process equipment (e.g., shell-and-tube heat exchangers) is often critical. What is more, many different geometric variants may need to be evaluated during the design process. Although this can be done using detailed computational fluid dynamics (CFD) models, the time needed to evaluate a single variant can easily reach tens of hours on powerful computing hardware. Simplified CFD models providing solutions in much shorter time frames may, therefore, be employed instead. Still, even these models can prove to be too slow or not robust enough when used in optimization algorithms. Effort is thus devoted to further improving their performance by applying the symmetric successive overrelaxation (SSOR) preconditioning technique in which, in contrast to, e.g., incomplete lower−upper factorization (ILU), the respective preconditioning matrix can always be constructed. Because the efficacy of SSOR is influenced by the selection of forward and... [more]
Numerical Investigation of the Aeroelastic Behavior of a Wind Turbine with Iced Blades
Sudhakar Gantasala, Narges Tabatabaei, Michel Cervantes, Jan-Olov Aidanpää
March 21, 2023 (v1)
Keywords: aeroelastic behavior, Computational Fluid Dynamics, icing, Simulation, wind turbine
Wind turbines installed in cold-climate regions are prone to the risks of ice accumulation which affects their aeroelastic behavior. The studies carried out on this topic so far considered icing in a few sections of the blade, mostly located in the outer part of the blade, and their influence on the loads and power production of the turbine are only analyzed. The knowledge about the influence of icing in different locations of the blade and asymmetrical icing of the blades on loads, power, and vibration behavior of the turbine is still not matured. To improve this knowledge, multiple simulation cases are needed to run with different ice accumulations on the blade considering structural and aerodynamic property changes due to ice. Such simulations can be easily run by automating the ice shape creation on aerofoil sections and two-dimensional (2-D) Computational Fluid Dynamics (CFD) analysis of those sections. The current work proposes such methodology and it is illustrated on the Nation... [more]
Natural Ventilation Effectiveness of Awning Windows in Restrooms in K-12 Public Schools
Sung-Chin Chung, Yi-Pin Lin, Chun Yang, Chi-Ming Lai
March 21, 2023 (v1)
Keywords: air environment, awning window, Computational Fluid Dynamics, natural ventilation, school restroom
Using computational fluid dynamics (CFD), this study explores the effect of a different number of awning windows and their installation locations on the airflow patterns and air contaminant distributions in restrooms in K-12 (for kindergarten to 12th grade) public schools in Taiwan. A representative restroom configuration with dimensions of 10.65 m × 9.2 m × 3.2 m (height) was selected as the investigated object. Based on the façade design feasibility, seven possible awning window configurations were considered. The results indicate that an adequate number of windows and appropriate installation locations are required to ensure the natural ventilation effectiveness of awning windows. The recommended installation configuration is provided.
Field Measurements and Numerical Simulation for the Definition of the Thermal Stratification and Ventilation Performance in a Mechanically Ventilated Sports Hall
Lina Seduikyte, Laura Stasiulienė, Tadas Prasauskas, Dainius Martuzevičius, Jurgita Černeckienė, Tadas Ždankus, Mantas Dobravalskis, Paris Fokaides
March 21, 2023 (v1)
Keywords: basketball hall, Computational Fluid Dynamics, field measurement, indoor air quality, stratification
Sports halls must meet strict requirements for energy and indoor air quality (IAQ); therefore, there is a great challenge in the design of the heating, ventilation, and air conditioning (HVAC) systems of such buildings. IAQ in sports halls may be affected by thermal stratification, pollutants from different sources, the maintenance of building, and the HVAC system of the building, as well as by the activities performed inside the building. The aim of this study is to investigate thermal stratification conditions in accordance with the performance of the HVAC systems in the basketball training hall of Žalgirio Arena, Kaunas in Lithuania. Field measurements including temperature, relative humidity, and CO2 concentration were implemented between January and February in 2017. The temperature and relative humidity were measured at different heights (0.1, 1.7, 2.5, 3.9, 5.4, and 6.9 m) and at five different locations in the arena. Experimental results show that mixing the ventilation applica... [more]
Development and Validation of a CFD Combustion Model for Natural Gas Engines Operating with Different Piston Bowls
Giovanni Gaetano Gianetti, Tommaso Lucchini, Gianluca D’Errico, Angelo Onorati, Patrik Soltic
March 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, FAM, light-duty engine, Natural Gas, premixed turbulent combustion, RANS
Nowadays, an accurate and precise description of the combustion phase is essential in spark-ignition (SI) engines to drastically reduce pollutant and greenhouse gas (GHG) emissions and increase thermal efficiency. To this end, computational fluid dynamics (CFD) can be used to study the different phenomena involved, such as the ignition of the charge, combustion development, and pollutant formation. In this work, a validation of a CFD methodology based on the flame area model (FAM) was carried out to model the combustion process in light-duty SI engines fueled with natural gas. A simplified spherical kernel approach was used to model the ignition phase, whereas turbulent flame propagation was described through two variables. A zero-dimensional evolution of the flame kernel radius was used in combination with the Herweg and Maly formulation to take the laminar-to-turbulent flame transition into account. To estimate the chemical composition of burnt gas, two different approaches were cons... [more]
Investigation of the Heat Storage Capacity and Storage Dynamics of a Novel Polymeric Macro-Encapsulated Core-Shell Particle Using a Paraffinic Core
Matthias Singer, Michael Fischlschweiger, Tim Zeiner
March 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, core-shell, latent heat, phase change materials
Thermal energy storages represent important devices for the decarbonisation of heat; hence, enabling a circular economy. Hereby, important tasks are the optimisation of thermal losses and providing a tuneable storage capacity, as well as tuneable storage dynamics for thermal energy storage modules which are composed of either sensible or phase change-based heat storage materials. The thermal storage capacity and the storage dynamics behaviour are crucial for fulfilling certain application requirements. In this work, a novel macro-encapsulated and spherical heat storage core-shell structure is presented and embedded in a supercritical ammonia working fluid flow field. The core of the macro-capsule is built by an organic low molecular weight substance showing a solid−liquid phase transition in a respective temperature zone, where the shell structure is made of polyvinylidene fluoride. Due to the direct coupling of computational fluid dynamics and the simulation of the phase transition of... [more]
Pulverized Coal-Fired Boilers: Future Directions of Scientific Research
Marek Ochowiak, Zdzisław Bielecki, Andżelika Krupińska, Magdalena Matuszak, Sylwia Włodarczak, Michał Bielecki, Dariusz Choiński, Jarosław Smyła, Krzysztof Jagiełło
March 20, 2023 (v1)
Keywords: catalyst, combustion, Computational Fluid Dynamics, dust duct, flow, pulverized coal-fired boiler
The paper provides an outlook on future directions of research and the possible applications for pulverized coal-fired boilers. One potential direction for future research is to focus on the ways to improve the efficiency of pulverized coal-fired boilers. This could involve developing new combustion technologies that are able to more thoroughly burn the coal and produce less waste or finding ways to capture and use the excess heat that is generated during the combustion process. The pulverized coal combustion process in power boilers is still being improved by the preliminary cleaning of coal and the use of various catalytic additives. Another area of research that could be valuable is the development of advanced control systems and monitoring technologies for pulverized coal-fired boilers. These systems could be used to optimize the performance of the boiler and ensure that it is operating at maximum efficiency while also providing real-time data on the condition of the boiler and any... [more]
Thermal Effects in the End-Winding Region of Electrical Machines
Mario Vukotić, Stefan Lutovski, Nina Šutar, Damijan Miljavec, Selma Čorović
March 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, end-winding region, fan blades, fanning factor, heat transfer, heat transfer coefficient, induction machine, permanent magnet machine, stator end winding, thermal analysis
The main heat transfer mechanism in the end-winding region of electrical machines is convection. In order to increase the air motion, the rotor is equipped with a series of blades. Their geometry is reflected in the fanning factor, i.e., the ratio between the rotor peripheral speed and air velocity. An accurate calculation procedure for the fanning factor has not yet been given. Knowing its value is crucial for the determination of air velocity and heat transfer coefficient (HTC), as the latter describes the end-winding heat removal capability. In this study, the convective heat transfer phenomena between the end winding and air inside the end-winding region were analyzed, with the heat generated only in the end winding, mimicked with a custom designed coil, and air moved by the blades. The analysis was performed by experimental testing and computational fluid dynamics (CFD) modeling. Measurements data were used to build a reliable CFD model. Further on, CFD results were used to derive... [more]
Overview of Common Thermophysical Property Modelling Approaches for Cryogenic Fluid Simulations at Supercritical Conditions
Jaya Vignesh Madana Gopal, Robert Morgan, Guillaume De Sercey, Konstantina Vogiatzaki
March 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, cryogenic fluids, equations of state, real fluids, supercritical
Computational Fluid Dynamics (CFD) frameworks of supercritical cryogenic fluids need to employ Real Fluid models such as cubic Equations of State (EoS) to account for thermal and inertial driven mechanisms of fluid evolution and disintegration. Accurate estimation of the non-linear variation in density, thermodynamic and transport properties is required to computationally replicate the relevant thermo and fluid dynamics involved. This article reviews the availability, performance and the implementation of common Real Fluid EoS and data-based models in CFD studies of supercritical cryogenic fluids. A systematic analysis of supercritical cryogenic fluid (N2, O2 and CH4) thermophysical property predictions by cubic (PR and SRK) and non-cubic (SBWR) Real Fluid EoS, along with Chung’s model, reveal that: (a) SRK EoS is much more accurate than PR at low temperatures of liquid phase, whereas PR is more accurate at the pseudoboiling region and (b) SBWR EoS is more accurate than PR and SRK desp... [more]
Numerical Investigation of the Effect of Surface Wettability and Rotation on Condensation Heat Transfer in a Sludge Dryer Vertical Paddle
Wei Liu, Miao Gui, Yudong Zha, Zengyao Li
March 20, 2023 (v1)
Keywords: Computational Fluid Dynamics, dropwise condensation, rotation, sludge paddle dryer
In this paper, the applicability of advanced heat transfer enhancement technology to a paddle dryer was discussed. A computational fluid dynamics (CFD) method was used to simulate condensation heat transfer on the inner surface of a dryer paddle. The effect of surface wettability and rotation on condensation heat transfer and droplet behavior was studied. The results showed that the present CFD model could properly simulate the condensation process on a vertical surface. With a decrease in the contact angle, the filmwise condensation turned into a dropwise condensation, which resulted in a significant increase in heat transfer coefficient and provided an approximately 5% increase in evaporation rate for the paddle dryer by changing the wettability of the inner surface of the paddle. Additionally, with a change in rotational angular velocity, heat transfer performance was almost unchanged under the filmwise condensation condition. However, rotational motion might cause a decrease in wal... [more]
Numerical and Experimental Analysis of Shell and Tube Heat Exchanger with Round and Hexagonal Tubes
Abdullah Khan, Imran Shah, Waheed Gul, Tariq Amin Khan, Yasir Ali, Syed Athar Masood
March 20, 2023 (v1)
Keywords: Ansys Fluent, Computational Fluid Dynamics, hexagonal tubes, Reynolds number, shell and tube heat exchanger, temperature drop
Shell and tube heat exchangers are used to transfer thermal energy from one medium to another for regulating fluid temperatures in the processing and pasteurizing industries. Enhancement of a heat transfer rate is desired to maximize the energy efficiency of the shell and tube heat exchangers. In this research work, we performed computational fluid dynamics (CFD) simulations and experimental analysis on the shell and tube heat exchangers using round and hexagonal tubes for a range of flow velocities using both parallel flow and counter flow arrangements. In the present work, the rate of heat transfer, temperature drop, and heat transfer coefficient are computed using three turbulence models: the Spalart−Allmaras, the k-epsilon (RNG), and the k-omega shear stress transport (SST). We further utilized the logarithmic mean temperature difference (LMTD) method to compute the heat transfer and mass flow rates for both parallel and counter flow arrangements. Our results show that the rate of... [more]
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