Journal articles on the topic 'Computational methods in fluid flow, heat and mass transfer (incl. computational fluid dynamics)'
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Drikakis, Dimitris, Michael Frank, and Gavin Tabor. "Multiscale Computational Fluid Dynamics." Energies 12, no. 17 (August 25, 2019): 3272. http://dx.doi.org/10.3390/en12173272.
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Computational Fluid Dynamics (CFD) has numerous applications in the field of energy research, in modelling the basic physics of combustion, multiphase flow and heat transfer; and in the simulation of mechanical devices such as turbines, wind wave and tidal devices, and other devices for energy generation. With the constant increase in available computing power, the fidelity and accuracy of CFD simulations have constantly improved, and the technique is now an integral part of research and development. In the past few years, the development of multiscale methods has emerged as a topic of intensive research. The variable scales may be associated with scales of turbulence, or other physical processes which operate across a range of different scales, and often lead to spatial and temporal scales crossing the boundaries of continuum and molecular mechanics. In this paper, we present a short review of multiscale CFD frameworks with potential applications to energy problems.
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Dixon, Anthony G., and Behnam Partopour. "Computational Fluid Dynamics for Fixed Bed Reactor Design." Annual Review of Chemical and Biomolecular Engineering 11, no. 1 (June 7, 2020): 109–30. http://dx.doi.org/10.1146/annurev-chembioeng-092319-075328.
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Flow, heat, and mass transfer in fixed beds of catalyst particles are complex phenomena and, when combined with catalytic reactions, are multiscale in both time and space; therefore, advanced computational techniques are being applied to fixed bed modeling to an ever-greater extent. The fast-growing literature on the use of computational fluid dynamics (CFD) in fixed bed design reflects the rapid development of this subfield of reactor modeling. We identify recent trends and research directions in which successful methodology has been established, for example, in computer generation of packings of complex particles, and where more work is needed, for example, in the meshing of nonsphere packings and the simulation of industrial-size packed tubes. Development of fixed bed reactor models, by either using CFD directly or obtaining insight, closures, and parameters for engineering models from simulations, will increase confidence in using these methods for design along with, or instead of, expensive pilot-scale experiments.
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Khongprom, Parinya, Supawadee Ratchasombat, Waritnan Wanchan, Panut Bumphenkiattikul, and Sunun Limtrakul. "Scaling of a catalytic cracking fluidized bed downer reactor based on computational fluid dynamics simulations." RSC Advances 10, no. 5 (2020): 2897–914. http://dx.doi.org/10.1039/c9ra10080f.
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Ozcan-Coban, Seda, Fatih Selimefendigil, Hakan Oztop, and Arif Hepbasli. "A review on computational fluid dynamics simulation methods for different convective drying applications." Thermal Science, no. 00 (2022): 70. http://dx.doi.org/10.2298/tsci220225070o.
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This paper focuses on the Computational Fluid Dynamics (CFD) studies on one of the commonly used drying processes for different applications. First, a brief information about drying is given with determining important properties that effect drying characteristics. Next, basic principles of CFD modelling are explained while capabilities of computational processing are presented. A detailed literature survey about CFD studies in convective drying process is then conducted. Finally, some sound concluding remarks are listed. It may be concluded that the CFD is a powerful and flexible tool that can be adopted to many different physical situations including complex scenarios, results of CFD simulations represent good predictions for fluid flow, heat and mass transfer of various drying methods and those numerical studies can be used for validation and controlling of applicability of new drying systems.
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Sawada, Ikuo, Hiroyuki Tanaka, and Masahiro Tanaka. "Status of Computational Fluid Dynamics and Its Application to Materials Manufacturing." MRS Bulletin 19, no. 1 (January 1994): 14–19. http://dx.doi.org/10.1557/s088376940003880x.
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Computational fluid dynamics was born principally in the aerospace field as a method for fluid flow and heat transfer research methods following experimental and analytical approaches. Along with progress in the cost performance of computers, computational fluid dynamics is now establishing itself as a tool to improve production processes and product quality in the steel, nonferrous metals, glass, plastics, and composite materials industries.Materials manufacturers use computational fluid dynamics for diverse purposes:1. Reduction in experimental conditions and costs;2. Detailed analysis of mechanisms with multifaceted information unobtainable through experimentation;3. Universal tool for scale-up; and4. Evaluation of novel processes.It can be readily imagined that accuracy, flexibility, and other requirements of computational fluid dynamics should vary with specific applications.Fluids generally observed in materials manufacturing processes are molten materials such as metal, glass, and plastics, and gases for stirring and refining. In the flow of such fluids, materials quality and process characteristics are governed by the following:1. Transport phenomena in the bulk region (where fluid flow is normally turbulent);2. Chemical reaction at interfaces;3. Transport phenomena in boundary layers near the interfaces; and4. Complex coupled phenomena (heat transfer, diffusion, chemical reaction, phase transformation like solidification, free surface, electromagnetic force, and bubble flow).
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Oon, C. S., A. Badarudin, S. N. Kazi, and M. Fadhli. "Simulation of Heat Transfer to Turbulent Nanofluid Flow in an Annular Passage." Advanced Materials Research 925 (April 2014): 625–29. http://dx.doi.org/10.4028/www.scientific.net/amr.925.625.
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The heat transfer in annular heat exchanger with titanium oxide of 1.0 volume % concentration as the medium of heat exchanger is considered in this study. The heat transfer simulation of the flow is performed by using Computational Fluid Dynamics package, Ansys Fluent. The heat transfer coefficients of water to titanium oxide nanofluid flowing in a horizontal counter-flow heat exchanger under turbulent flow conditions are investigated. The results show that the convective heat transfer coefficient of the nanofluid is slightly higher than that of the base fluid by several percents. The heat transfer coefficient increases with the increase of the mass flow rate of hot water and also the nanofluid.
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Ekaroek Phumnok, Waritnan Wanchan, Matinee Chuenjai, Panut Bumphenkiattikul, Sunun Limtrakul, Sukrittira Rattanawilai, and Parinya Khongprom. "Study of Hydrodynamics and Upscaling of Immiscible Fluid Stirred Tank using Computational Fluid Dynamics Simulation." CFD Letters 14, no. 6 (June 26, 2022): 115–33. http://dx.doi.org/10.37934/cfdl.14.6.115133.
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Stirred tanks are prevalent in various industries, including chemical, biochemical, and pharmaceutical industries. These reactors are suitable for ensuring efficient mass and heat transfer because adequate mixing can be achieved. Numerous studies have been conducted on small-scale stirred-tank reactors. However, upscaling such reactors is challenging because of the complex flow behavior inside the system, especially for the mixing of immiscible liquid–liquid systems. Thus, the objectives of this study were to examine the flow behavior and upscale an immiscible liquid–liquid stirred tank using CFD simulation by investigating a flat-bottomed stirred tank reactor, equipped with a six-blade Rushton turbine. The simulated results were in good agreement with those obtained experimentally. The scale of the reactor significantly affects the hydrodynamic behavior, and the uniformity of the radial distribution of the velocity decreases with increasing Reynolds number. Furthermore, the upscaling criteria were evaluated for geometric similarity and equal mixing times. The proposed scaling law reliably scaled up the immiscible liquid–liquid mixing in a stirred tank with a difference in the range of ±10%.
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Khan, Sabuddin, H. C. Thakur, and Nazeem Khan. "A Computational Fluid Dynamic Study of Shell and Tube Heat Exchanger Using (CuO, Al2O3, TiO2)-Water Nanofluids." Advanced Science, Engineering and Medicine 12, no. 12 (December 1, 2020): 1462–67. http://dx.doi.org/10.1166/asem.2020.2585.
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The Nusselt number for a Shell and tube Heat Exchanger with segmental baffles for different nanofluids, for different mass flow rate are discussed in the present paper. A shell and tube heat exchanger with 7 tubes and 4 segmental baffles modelling is done using SOLIDWORKS and simulation is done by the Computational Fluid Dynamic (CFD) software; ANSYS-FLUENT. By using Fluent, computational fluid dynamics software the heat transfer coefficient and various heat characteristics of Al2O3–H2O, TiO2–H2O and CuO–H2O for 1% volume of concentration nanofluids are estimated in the Shell and Tube Heat Exchanger considering the turbulent flow.
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Chen, Huajun, Yitung Chen, Hsuan-Tsung Hsieh, and Nathan Siegel. "Computational Fluid Dynamics Modeling of Gas-Particle Flow Within a Solid-Particle Solar Receiver." Journal of Solar Energy Engineering 129, no. 2 (August 25, 2006): 160–70. http://dx.doi.org/10.1115/1.2716418.
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A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two-band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray-tracing algorithm. Two kinds of solid-particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the gas velocity, temperature, particle solid volume fraction, particle outlet temperature, and cavity efficiency.
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Sharma, Shubham, Shalab Sharma, Mandeep Singh, Parampreet Singh, Rasmeet Singh, Sthitapragyan Maharana, Nima Khalilpoor, and Alibek Issakhov. "Computational Fluid Dynamics Analysis of Flow Patterns, Pressure Drop, and Heat Transfer Coefficient in Staggered and Inline Shell-Tube Heat Exchangers." Mathematical Problems in Engineering 2021 (June 1, 2021): 1–10. http://dx.doi.org/10.1155/2021/6645128.
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In this numerical study, the heat transfer performance of shell-and-tube heat exchangers (STHXs) has been compared for two different tube arrangements. STHX having 21 and 24 tubes arranged in the inline and staggered grid has been considered for heat transfer analysis. Shell-and-tube heat exchanger with staggered grid arrangement has been observed to provide lesser thermal stratification as compared to the inline arrangement. Further, the study of variation in the mass flow rate of shell-side fluid having constant tube-side flow rate has been conducted for staggered grid structure STHX. The mass flow rate for the shell side has been varied from 0.1 kg/s to 0.5 kg/s, respectively, keeping the tube-side mass flow rate as constant at 0.25 kg/s. The influence of bulk mass-influx transfer rate on heat transfer efficiency, effectiveness, and pressure drop of shell-tube heat exchangers has been analyzed. CFD results were compared with analytical solutions, and it shows a good agreement between them. It has been observed that pressure drop is minimum for the flow rate of 0.1 kg/s, and outlet temperatures at the shell side and tube side have been predicted to be 40.94°C and 63.63°C, respectively.
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Li, Chunming, Wei Wu, Yin Liu, Chenhui Hu, and Junjie Zhou. "Analysis of Air–Oil Flow and Heat Transfer inside a Grooved Rotating-Disk System." Processes 7, no. 9 (September 18, 2019): 632. http://dx.doi.org/10.3390/pr7090632.
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An investigation on the two-phase flow field inside a grooved rotating-disk system is presented by experiment and computational fluid dynamics numerical simulation. The grooved rotating-disk system consists of one stationary flat disk and one rotating grooved disk. A three-dimensional computational fluid dynamics model considering two-phase flow and heat transfer was utilized to simulate phase distributions and heat dissipation capability. Visualization tests were conducted to validate the flow patterns and the parametric effects on the flow field. The results indicate that the flow field of the grooved rotating-disk system was identified to be an air–oil flow. A stable interface between the continuous oil phase and the two-phase area could be formed and observed. The parametric analysis demonstrated that the inter moved outwards in the radial direction, and the average oil volume fraction over the whole flow field increased with smaller angular speed, more inlet mass flow of oil, or decreasing disk spacing. The local Nusselt number was remarkably affected by the oil volume fraction and the fluid flow speed distributions in this two-phase flow at different radial positions. Lastly, due to the change of phase volume fraction and fluid flow speed, the variation of the average Nusselt number over the whole flow field could be divided into three stages.
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Yeoh, Guan Heng, and Xiaobin Zhang. "Computational fluid dynamics and population balance modelling of nucleate boiling of cryogenic liquids: Theoretical developments." Journal of Computational Multiphase Flows 8, no. 4 (November 22, 2016): 178–200. http://dx.doi.org/10.1177/1757482x16674217.
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The main focus in the analysis of pool or flow boiling in saturated or subcooled conditions is the basic understanding of the phase change process through the heat transfer and wall heat flux partitioning at the heated wall and the two-phase bubble behaviours in the bulk liquid as they migrate away from the heated wall. This paper reviews the work in this rapid developing area with special reference to modelling nucleate boiling of cryogenic liquids in the context of computational fluid dynamics and associated theoretical developments. The partitioning of the wall heat flux at the heated wall into three components – single-phase convection, transient conduction and evaporation – remains the most popular mechanistic approach in predicting the heat transfer process during boiling. Nevertheless, the respective wall heat flux components generally require the determination of the active nucleation site density, bubble departure diameter and nucleation frequency, which are crucial to the proper prediction of the heat transfer process. Numerous empirical correlations presented in this paper have been developed to ascertain these three important parameters with some degree of success. Albeit the simplicity of empirical correlations, they remain applicable to only a narrow range of flow conditions. In order to extend the wall heat flux partitioning approach to a wider range of flow conditions, the fractal model proposed for the active nucleation site density, force balance model for bubble departing from the cavity and bubble lifting off from the heated wall and evaluation of nucleation frequency based on fundamental theory depict the many enhancements that can improve the mechanistic model predictions. The macroscopic consideration of the two-phase boiling in the bulk liquid via the two-fluid model represents the most effective continuum approach in predicting the volume fraction and velocity distributions of each phase. Nevertheless, the interfacial mass, momentum and energy exchange terms that appear in the transport equations generally require the determination of the Sauter mean diameter or interfacial area concentration, which strongly governs the fluid flow and heat transfer in the bulk liquid. In order to accommodate the dynamically changing bubble sizes that are prevalent in the bulk liquid, the mechanistic approach based on the population balance model allows the appropriate prediction of local distributions of Sauter mean diameter or interfacial area concentration, which in turn can improve the predictions of the interfacial mass, momentum and energy exchanges that occur across the interface between the phases. Need for further developments are discussed.
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Muthusamy, P., and Palanisamy Senthil Kumar. "Waste Heat Recovery Using Matrix Heat Exchanger from the Exhaust of an Automobile Engine for Heating Car’s Passenger Cabin." Advanced Materials Research 984-985 (July 2014): 1132–37. http://dx.doi.org/10.4028/www.scientific.net/amr.984-985.1132.
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The main objective of our work is to analysis the heat transfer rate for various fluids with different matrix heat exchanger (MHE) models and flow characteristic in matrix heat exchanger by using computational fluid dynamics (CFD) package with small car. The amount of heat carried by the cold fluid from hot fluid is mainly depends upon the mass flow rate of the working fluid. The heat transfer area per unit volume of tube is more. So, it increases the temperature of the cold fluid. Here, the hot and cold fluids are moving in the alternate tubes of heat exchanger in the counter flow direction. The small amounts of pressure drop are occurred but which is less compared to existing model. Flow disturbances are rectified in the MHE through the modifications made. Since, silicon carbide material is used as a polishing material to avoid the deposit of carbon at the inner side of the flow passage and this waste heat energy is used for heating passenger cabin during winter season. The wood is used as an insulating material to avoid the heat flow from fluid to atmosphere. Keywords-Heat transfer rate, Matrix heat exchanger, Working fluid, Polishing material.
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Reddy Kukutla, Pol, and BVSSS Prasad. "Network analysis of a coolant flow performance for the combined impingement and film cooled first-stage of high pressure gas turbine nozzle guide vane." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 6 (April 16, 2018): 1977–89. http://dx.doi.org/10.1177/0954410018767290.
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The present paper describes a system-level thermo-fluid network analysis for the secondary air system analysis of a typically film-cooled nozzle guide vane with multiple actions of jet impingement. The one-dimensional simulation was done with the help of the commercially available Flownex 2015 software. The system-level thermo-fluid network results were validated with both the computational fluid dynamics results and experimentally available literature. The entire nozzle guide vane geometry was first mapped to a thermo-fluid network model and the pressure conditions at different nodes. The discharge and heat transfer coefficients obtained from the Ansys FLUENT were specified as inputs to the thermo-fluid network model. The results show that the one-dimensional simulation of the coolant mass flow rates and jet Nusselt number values are in good agreement with the three-dimensional computational fluid dynamics results.
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Ajeeb, Wagd, Monica S. A. Oliveira, Nelson Martins, and S. M. Sohel Murshed. "Numerical approach for fluids flow and thermal convection in microchannels." Journal of Physics: Conference Series 2116, no. 1 (November 1, 2021): 012049. http://dx.doi.org/10.1088/1742-6596/2116/1/012049.
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Abstract The heat transfer performance of conventional thermal fluids in microchannels is an attractive method for cooling devices such as microelectronic applications. Computational fluid dynamics (CFD) is a very significant research technique in heat transfer studies and validated numerical models of microscale thermal management systems are of utmost importance. In this paper, some literature studies on available numerical and experimental models for single-phase and Newtonian fluids are reviewed and methods to tackle laminar fluid flow through a microchannel are sought. A few case studies are selected, and a numerical simulation is performed to obtain fluid flow behaviour within a microchannel, to test the level of accuracy and understanding of the problem. The numerical results are compared with relevant experimental results from the literature and a proper methodology for numerical investigation of single-phase and Newtonian fluid in laminar flow convection heat transfer in microscale heat exchangers is defined.
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Pungaiah, Sudalai Suresh, and Chidambara Kuttalam Kailasanathan. "Thermal Analysis and Optimization of Nano Coated Radiator Tubes Using Computational Fluid Dynamics and Taguchi Method." Coatings 10, no. 9 (August 20, 2020): 804. http://dx.doi.org/10.3390/coatings10090804.
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Automotive heat removal levels are of high importance for maximizing fuel consumption. Current radiator designs are constrained by air-side impedance, and a large front field must meet the cooling requirements. The enormous demand for powerful engines in smaller hood areas has caused a lack of heat dissipation in the vehicle radiators. As a prediction, exceptional radiators are modest enough to understand coolness and demonstrate great sensitivity to cooling capacity. The working parameters of the nano-coated tubes are studied using Computational Fluid Dynamics (CFD) and Taguchi methods in this article. The CFD and Taguchi methods are used for the design of experiments to analyse the impact of nano-coated radiator parameters and the parameters having a significant impact on the efficiency of the radiator. The CFD and Taguchi methodology studies show that all of the above-mentioned parameters contribute equally to the rate of heat transfer, effectiveness, and overall heat transfer coefficient of the nanocoated radiator tubes. Experimental findings are examined to assess the adequacy of the proposed method. In this study, the coolant fluid was transmitted at three different mass flow rates, at three different coating thicknesses, and coated on the top surface of the radiator tubes. Thermal analysis is performed for three temperatures as heat input conditioning for CFD. The most important parameter for nanocoated radiator tubes is the orthogonal array, followed by the Signal-to-Noise Ratio (SNRA) and the variance analysis (ANOVA). A proper orthogonal array is then selected and tests are carried out. The findings of ANOVA showed 95% confidence and were confirmed in the most significant parameters. The optimal values of the parameters are obtained with the help of the graphs.
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Singh, Parampreet, Neel Kanth Grover, Vivek Agarwal, Shubham Sharma, Jujhar Singh, Milad Sadeghzadeh, and Alibek Issakhov. "Computational Fluid Dynamics Analysis of Impingement Heat Transfer in an Inline Array of Multiple Jets." Mathematical Problems in Engineering 2021 (April 12, 2021): 1–10. http://dx.doi.org/10.1155/2021/6668942.
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Amid all convective heat transfer augmentation methods employing single phase, jet impingement heat transfer delivers significantly higher coefficient of local heat transfer. The arrangement leading to nine jets in square array has been used to cool a plate maintained at constant heat flux. Numerical study has been carried out using RANS-based turbulence modeling in commercial CFD Fluent software. The turbulent models used for the study are three different “k-ε” models (STD, RNG, and realizable) and SST “k-ω” model. The numerical simulation output is equated with the experimental results to find out the most accurate turbulence model. The impact of variation of Reynolds number, inter-jet spacing, and separation distance has been considered for the geometry considered. These parameters affect the coefficient of heat transfer, temperature, and turbulent kinetic energy related to flow. The local “h” values have been noticed to decline with the rise in separation distance “H/D.” The SST “k-ω” model has been noticed to be in maximum agreement with the experimental results. The average value of heat transfer coefficient “h” reduces from 210 to 193 W/m2K with increase in “H/D” from 6 to 10 at “Re” = 9000 and S/D of 3. As per numerical results, inter-jet spacing “S/D” of 3 has been determined to be the most optimum value.
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Li, Yong An, Xue Lai Liu, Jia Jia Yan, and Teng Xing. "Research on Wet Thermal Recovery Plant Used by Air Conditioning." Advanced Materials Research 424-425 (January 2012): 1155–58. http://dx.doi.org/10.4028/www.scientific.net/amr.424-425.1155.
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Based on the simulation Computational Fluid Dynamics method, in view of air conditioning with wet thermal recovery plant for heat and mass transfer characteristic, establishes air channels in three-dimensional laminar flow and heat transfer, mass transfer coupling process of mathematical physics model, discusses the air conditioning with wet thermal recovery plant air channels in temperature, concentration and pressure parameters such as distribution, application enthalpy efficiency analysis method to the heat transfer performance is evaluated. The results indicate that structure parameters of wet thermal recovery plant used by air conditioning play important influence for the heat transfer performance and flow resistance performance. The research conclusion provides guidance for air conditioning with wet thermal recovery plant of optimization.
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Bognár, Gabriella, Mohamad Klazly, and Krisztián Hriczó. "Nanofluid Flow Past a Stretching Plate." Processes 8, no. 7 (July 13, 2020): 827. http://dx.doi.org/10.3390/pr8070827.
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Viscous nanofluid flow due to a sheet moving with constant speed in an otherwise quiescent medium is studied for three types of nanofluids, such as alumina (Al2O3), titania (TiO2), and magnetite (Fe3O4), in a base fluid of water. The heat and mass transfer characteristics are investigated theoretically using the boundary layer theory and numerically with computational fluid dynamics (CFD) simulation. The velocity, temperature, skin friction coefficient, and local Nusselt number are determined. The obtained results are in good agreement with known results from the literature. It is found that the obtained results for skin friction and for the Nusselt number are slightly greater than those obtained via boundary layer theory.
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Wang, Zheng Tao, Wei Wei Liu, and Jing Jing Xu. "Numerical Simulation of Heat Transfer for the Ethyl Benzene Dehydrogenation Catalyst in the Kiln." Applied Mechanics and Materials 575 (June 2014): 672–76. http://dx.doi.org/10.4028/www.scientific.net/amm.575.672.
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In industrial reactors, the chemical or physical transformations are always expected to occur in the best way, so the performance controlling processes associated with mixing of reactants, heat transfer, contacting of multiple phases, mass transfer, chemical reactions, and phase changes are important. In this paper the heat transfer simulation of the gas-solid multiphase flow in ethylbenzene dehydrogenation catalyst kiln, heat conduction, convection and radiation involved, has been expressed by using the computational fluid dynamics (CFD) method. The present study can contribute to our better understanding of the heating process and at the same time, the thermal power distribution and temperature variation of the fluid and catalyst particles can provide guidance for the kiln design.
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El Baamrani, Hayat, Lahcen Bammou, Ahmed Aharoune, and Abdallah Boukhris. "Volume of Fluid (VOF) Modeling of Liquid Film Evaporation in Mixed Convection Flow through a Vertical Channel." Mathematical Problems in Engineering 2021 (May 23, 2021): 1–12. http://dx.doi.org/10.1155/2021/9934593.
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In this paper, the volume of fluid (VOF) method in the OpenFOAM open-source computational fluid dynamics (CFD) package is used to investigate the coupled heat and mass transfer by mixed convection during the evaporation of water-thin film. The liquid film is falling down on the left wall of a vertical channel and is subjected to a uniform heat flux density, whereas the right wall is assumed to be insulated and dry. The gas mixture consists of air and water vapor. The governing equations in the liquid and in the gas areas with the boundary conditions are solved by using the finite volume method. The results which include temperature, velocity, and vapor mass fraction are presented. The effect of heat flux density, liquid inlet temperature, and mass flow rate on the heat and mass transfer are also analyzed. Better liquid film evaporation is noted for the system with a higher heat flux density and inlet liquid temperature or a lower mass flow rate. Therefore, the VOF method describes well the thermal and dynamic behavior during the evaporation of the liquid film.
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Araújo, Morgana Vasconcellos, Alanna C. Sousa, Marcia R. Luiz, Adriano S. Cabral, Thayze Rodrigues Bezerra Pessoa, Pierre Correa Martins, Anderson Melchiades Vasconcelos da Silva, R. S. Santos, Vital Araújo Barbosa de Oliveira, and Antonio Gilson Barbosa de Lima. "Computational Fluid Dynamics Studies in the Drying of Industrial Clay Brick: The Effect of the Airflow Direction." Diffusion Foundations and Materials Applications 30 (August 19, 2022): 69–84. http://dx.doi.org/10.4028/p-j1eci6.
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The manufacture of ceramic brick goes through the stages of raw material extraction, clay homogenization, material conformation, drying and firing. Drying is the phase that needs greater care, as it involves removing part of the moisture from the brick, in order to preserve its quality after process. This work aims to predict heat and mass transfer in the drying of ceramic bricks in oven using computational fluid dynamics. Considering the constant thermophysical properties, a transient three-dimensional mathematical model was used to predict mass and energy transfer between the material and air during the process. Drying simulations at temperature of 100°C were performed with the air flow in the frontal direction to the ceramic brick holes and the results were compared with those obtained for the air flow in the perpendicular direction to the brick holes reported in the literature. It was found that the position of the brick in relation to the direction of air flow inside the oven affected directly the drying and heating kinetics, and the distribution of temperature and moisture content inside the brick. The positioning of the holes in the brick parallel to the direction of the air flow resulted in reduction at the drying time and, consequently, in energy savings in the process, more uniform drying, and improvement in the product quality.
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Khamooshi, Mehrdad, David F. Fletcher, Hana Salati, Sara Vahaji, Shaun Gregory, and Kiao Inthavong. "Computational assessment of the nasal air conditioning and paranasal sinus ventilation from nasal assisted breathing therapy." Physics of Fluids 34, no. 5 (May 2022): 051912. http://dx.doi.org/10.1063/5.0090058.
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Nasal cannula oxygen therapy is a common treatment option for patients with respiratory failure but needs further investigation to understand its potential for use for assisted breathing. Air with a high oxygen level is introduced into the nasal cavity using a nasal cannula during assisted breathing via oxygen therapy. The treatment impacts the nasal airflow dynamics and air-conditioning function. This study aims to investigate the nasal heat and mass transfer and sinus ventilation during assisted breathing at different operating conditions using computational fluid dynamics simulations. The nasal geometry was reconstructed from high-resolution computed tomography scans of a healthy subject. A constant inhalation flow rate of 15 LPM (liters per minute) was used, and the nasal cannula flow rate was set to between 5 and 15 LPM. The results demonstrated that assisted breathing at a high flow rate impacted sinus ventilation. It also changed the mucosal surface heat and mass transfer, thus inhaled air temperature and humidity. The high flow assisted breathing at 36 °C affected the nasal heat flux the most compared with other breathing conditions, while the low flow assisted breathing had minimal effect and, therefore, could be considered ineffective for any relevant treatment.
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Divo, Eduardo, and Alain J. Kassab. "An Efficient Localized Radial Basis Function Meshless Method for Fluid Flow and Conjugate Heat Transfer." Journal of Heat Transfer 129, no. 2 (May 25, 2006): 124–36. http://dx.doi.org/10.1115/1.2402181.
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A localized radial basis function (RBF) meshless method is developed for coupled viscous fluid flow and convective heat transfer problems. The method is based on new localized radial-basis function (RBF) expansions using Hardy Multiquadrics for the sought-after unknowns. An efficient set of formulae are derived to compute the RBF interpolation in terms of vector products thus providing a substantial computational savings over traditional meshless methods. Moreover, the approach developed in this paper is applicable to explicit or implicit time marching schemes as well as steady-state iterative methods. We apply the method to viscous fluid flow and conjugate heat transfer (CHT) modeling. The incompressible Navier–Stokes are time marched using a Helmholtz potential decomposition for the velocity field. When CHT is considered, the same RBF expansion is used to solve the heat conduction problem in the solid regions enforcing temperature and heat flux continuity of the solid/fluid interfaces. The computation is accelerated by distributing the load over several processors via a domain decomposition along with an interface interpolation tailored to pass information through each of the domain interfaces to ensure conservation of field variables and derivatives. Numerical results are presented for several cases including channel flow, flow in a channel with a square step obstruction, and a jet flow into a square cavity. Results are compared with commercial computational fluid dynamics code predictions. The proposed localized meshless method approach is shown to produce accurate results while requiring a much-reduced effort in problem preparation in comparison to other traditional numerical methods.
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Meng, Wei An, Mutellip Ahmat, Nijat Yusup, and Asiye Shavkat. "Study on the Field Dynamics of the Seal Cavity Flow Field for High Parameters Bellows Mechanical Seal." Applied Mechanics and Materials 99-100 (September 2011): 1287–92. http://dx.doi.org/10.4028/www.scientific.net/amm.99-100.1287.
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Based on the computational fluid dynamics (CFD) theory and numerical simulation methods, the seal cavity flow field for the bellows mechanical seal under such the high temperature, high pressure, high-speed as complex working conditions was numerically simulated, and the temperature field, velocity field, pressure field, turbulent kinetic energy and the flow field vorticity distribution of the medium of the seal cavity were obtained, the three-dimensional fluid flow in the seal cavity, the heat transfer characteristics and the impact on the sealing performance were analyzed in this researching.
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POVITSKY, ALEX. "FLUID DYNAMICS ISSUES IN SYNTHESIS OF CARBON NANOTUBES." International Journal of Nanoscience 04, no. 01 (February 2005): 73–98. http://dx.doi.org/10.1142/s0219581x0500295x.
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The majority of carbon nanotubes' synthesis processes occur in the presence of fluid (liquid, gas, plasma, or multi-phase flow) that may function as a carrier of catalyst particles, feedstock of carbon, and the heating or cooling agent. The fluid motion defines the temperature of catalyst particles and the local chemical composition of the fluid that determines the success of synthesis of high-purity nanotubes. In this review paper, the laser ablation process, high-pressure carbon oxide process, and chemical vapor deposition process are considered from the prospective of fluid dynamics modeling. The multi-model approach should be used for concurrent rendering of different areas of computational domain by different models and/or different time steps for the same model. For multiple plume ejection in laser ablation, the near-target area could be rendered by molecular dynamics approach whereas continuous gas dynamics algorithms should be employed to simulate plume dynamics of previously ejected plumes apart of the target. Such an approach combines continuous mechanics of multi-species flow of feedstock gas or plume; micro-fluidic flow model that is needed to find heat and mass transfer rate to catalysts in presence of individual nanotubes in close proximity to each other; and molecular dynamics of evaporation and ejection of plume in laser ablation.
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Amiri, Leyla, Marco Antonio Rodrigues de Brito, Seyed Ali Ghoreishi-Madiseh, Navid Bahrani, Ferri P. Hassani, and Agus P. Sasmito. "Numerical Evaluation of the Transient Performance of Rock-Pile Seasonal Thermal Energy Storage Systems Coupled with Exhaust Heat Recovery." Applied Sciences 10, no. 21 (November 3, 2020): 7771. http://dx.doi.org/10.3390/app10217771.
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This study seeks to investigate the concept of using large waste rocks from mining operations as waste-heat thermal energy storage for remote arctic communities, both commercial and residential. It holds its novelty in analyzing such systems with an experimentally validated transient three-dimensional computational fluid dynamics and heat transfer model that accounts for interphase energy balance using a local thermal non-equilibrium approach. The system performance is evaluated for a wide range of distinct parameters, such as porosity between 0.2 and 0.5, fluid velocity from 0.01 to 0.07 m/s, and the aspect ratio of the bed between 1 and 1.35. It is demonstrated that the mass flow rate of the heat transfer fluid does not expressively impact the total energy storage capacity of the rock mass, but it does significantly affect the charge/discharge times. Finally, it is shown that porosity has the greatest impact on both fluid flow and heat transfer. The evaluations show that about 540 GJ can be stored on the bed with a porosity of 0.2, and about 350 GJ on the one with 0.35, while the intermediate porosity leads to a total of 450 GJ. Additionally, thermal capacity is deemed to be the most important thermophysical factor in thermal energy storage performance.
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Rożeń, Antoni. "Modelling of a passive autocatalytic hydrogen recombiner – a parametric study." Nukleonika 60, no. 1 (March 1, 2015): 161–69. http://dx.doi.org/10.1515/nuka-2015-0002.
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Abstract Operation of a passive autocatalytic hydrogen recombiner (PAR) has been investigated by means of computational fluid dynamics methods (CFD). The recombiner is a self-active and self-adaptive device used to remove hydrogen from safety containments of light water nuclear reactors (LWR) by means of a highly exothermic reaction with oxygen at the surface of a platinum or palladium catalyst. Different turbulence models (k-ω, k-ɛ, intermittency, RSM) were applied in numerical simulations of: gas flow, heat and mass transport and chemical surface reactions occurring in PAR. Turbulence was found to improve mixing and mass transfer and increase hydrogen recombination rate for high gas flow rates. At low gas flow rates, simulation results converged to those obtained for the limiting case of laminar flow. The large eddy simulation technique (LES) was used to select the best RANS (Reynolds average stress) model. Comparison of simulation results obtained for two- and three-dimensional computational grids showed that heat and mass transfer occurring in PAR were virtually two-dimensional processes. The effect of hydrogen thermal diffusion was also discussed in the context of possible hydrogen ignition inside the recombiner.
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Faltsi, O., S. D. Vlaev, D. Sofialidis, and J. Kirpitsas. "Novel areas and future trends of computational fluid dynamics software applications in chemical engineering." Chemical Industry and Chemical Engineering Quarterly 12, no. 4 (2006): 213–19. http://dx.doi.org/10.2298/ciceq0604213f.
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The paper presents a brief overview of advanced novel applications and future trends of Computational Fluid Dynamics software in Chemical Engineering. Among the cases of major importance, single phase turbulent flow, as well as multiphase flow models are reviewed. Referring to single phase flows, the LES and RANS approaches are described and illustrated. The RANS approach is revealed as the most popular and inexpensive method for the analysis and solving of technical tasks. The paper reports on two recent modeling applications, namely, the CFD facilitated design of a new mixing impeller and the CFD characterization of impeller mixing efficiency. Multiphase models of increased sophistication describing solid, liquid and gas flows with simultaneous mass transfer between the phases are summarized with emphasis on their applications to describe evaporation, condensation, as well as chemical reactions in process equipment such as distillation columns and fluidized beds. The future trends and directions in Computer Aided methods for the analysis of Chemical Engineering processes incorporate developments, such as the integration of various pieces of software including flow sheet modeling CFD modeling and complex reaction and thermodynamic models.
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Michalcová, Vladimíra, and Kamila Kotrasová. "The Numerical Diffusion Effect on the CFD Simulation Accuracy of Velocity and Temperature Field for the Application of Sustainable Architecture Methodology." Sustainability 12, no. 23 (December 5, 2020): 10173. http://dx.doi.org/10.3390/su122310173.
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Numerical simulation of fluid flow and heat or mass transfer phenomenon requires numerical solution of Navier–Stokes and energy-conservation equations, together with the continuity equation. The basic problem of solving general transport equations by the Finite Volume Method (FVM) is the exact calculation of the transport quantity. Numerical or false diffusion is a phenomenon of inserting errors in calculations that threaten the accuracy of the computational solution. The paper compares the physical accuracy of the calculation in the Computational Fluid Dynamics (CFD) code in Ansys Fluent using the offered discretization calculation schemes, methods of solving the gradients of the transport quantity on the cell walls, and the influence of the mesh type. The paper offers possibilities on how to reduce numerical errors. In the calculation area, the sharp boundary of two areas with different temperatures is created in the flow direction. The three-dimensional (3D) stationary flow of the fictitious gas is simulated using FVM so that only advective transfer, in terms of momentum and heat, arises. The subject of the study is to determine the level of numerical diffusion (temperature field scattering) and to evaluate the values of the transport quantity (temperature), which are outside the range of specified boundary conditions at variously set calculation parameters.
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Luzi, Giovanni, and Christopher McHardy. "Modeling and Simulation of Photobioreactors with Computational Fluid Dynamics—A Comprehensive Review." Energies 15, no. 11 (May 27, 2022): 3966. http://dx.doi.org/10.3390/en15113966.
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Computational Fluid Dynamics (CFD) have been frequently applied to model the growth conditions in photobioreactors, which are affected in a complex way by multiple, interacting physical processes. We review common photobioreactor types and discuss the processes occurring therein as well as how these processes have been considered in previous CFD models. The analysis reveals that CFD models of photobioreactors do often not consider state-of-the-art modeling approaches. As a comprehensive photobioreactor model consists of several sub-models, we review the most relevant models for the simulation of fluid flows, light propagation, heat and mass transfer and growth kinetics as well as state-of-the-art models for turbulence and interphase forces, revealing their strength and deficiencies. In addition, we review the population balance equation, breakage and coalescence models and discretization methods since the predicted bubble size distribution critically depends on them. This comprehensive overview of the available models provides a unique toolbox for generating CFD models of photobioreactors. Directions future research should take are also discussed, mainly consisting of an extensive experimental validation of the single models for specific photobioreactor geometries, as well as more complete and sophisticated integrated models by virtue of the constant increase of the computational capacity.
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Li, Yong An, Ting Ting Wang, Xue Lai Liu, and Teng Xing. "Thermal Performance Research of Thermal Recovery Unit for Air-Conditioning Systerm." Advanced Materials Research 243-249 (May 2011): 4965–68. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4965.
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This document established a three-dimensional laminar mathematical and physical model which describes heat transfer, mass transfer coupling process in wet thermal recovery unit for air-conditioning systerms, based on Computational Fluid Dynamics (CFD) simulations. In addition, the research discussed the distributions of pressure, temperature, concentration and other parameters in the air channels. The heat transfer performance was analyzed by enthalpy efficiency. The results showed that the structural parameters of wet thermal recovery unit for air-conditioning systerm played important influence in the heat transfer performance and flow drag performance. The research set a foundation for the optimal design of wet thermal recovery unit for air-conditioning systerm.
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Malang, Jameson, Perumal Kumar, and Agus Saptoro. "Computational Fluid Dynamics-Based Hydrodynamics Studies in Packed Bed Columns: Current Status and Future Directions." International Journal of Chemical Reactor Engineering 13, no. 3 (September 1, 2015): 289–303. http://dx.doi.org/10.1515/ijcre-2014-0121.
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Abstract A careful review of the literature reveals that extensive research has been done on the hydrodynamics in packed bed columns using turbulence models. It can be noted that the choice of turbulence model is influenced by the number of phases, type of fluid, Reynolds number range and the type of packing. Thus, comparison of turbulence models for the selection of a suitable model assumes great importance for the better prediction of flow pattern. This is due to the fact that poor prediction of the flow pattern can lead to a limited heat and mass transfer model as the rate of transfer processes in packed bed is governed by the hydrodynamics of the packed bed. The aim of this paper is to give a review of the computational fluid dynamics (CFD)-based hydrodynamics studies of packed bed columns with the primary interest of studying pressure drop and drag coefficient in packed beds. From the literature survey in Science Direct database, more than 48,000 papers related to packed bed columns have been published with more than 3,000 papers focused on the hydrodynamic studies of the bed to date. Unfortunately, there are only a few studies reported on the hydrodynamics of packed columns under supercritical fluid condition. Therefore, it is imperative that the future work has to focus on the hydrodynamics of supercritical packed column and particularly on the selection of suitable turbulence model.
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Sadripour, Maryam, Amir Rahimi, and Mohammad Sadegh Hatamipour. "CFD Modeling and Experimental Study of a Spray Dryer Performance." Chemical Product and Process Modeling 9, no. 1 (June 1, 2014): 15–24. http://dx.doi.org/10.1515/cppm-2013-0034.
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Abstract The performance of a pilot-scale spray dryer is investigated experimentally and theoretically. The governing equations for flow field, heat and mass transfer, and particle trajectory are solved by applying computational fluid dynamics (CFD). The effects of inlet air temperature and initial particle diameter on the outlet humidity and particle residence time are examined. These parameters should be considered carefully in proper designing of spray dryers especially for the heat-sensitive products. The model is validated with an error of 5.5%.
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Borbora, Mustaque Hussain, B. Vasu, and Ali J. Chamkha. "A Review Study of Numerical Simulation of Lid-Driven Cavity Flow with Nanofluids." Journal of Nanofluids 12, no. 3 (April 1, 2023): 589–604. http://dx.doi.org/10.1166/jon.2023.1930.
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Perhaps the most deliberated fluid problem in the field of Computational Fluid Dynamics is the lid driven cavity flow whose simple geometry is used to study the thermal behavior of many engineering applications such as cooling of electronic equipment, solar collectors, thermal storage systems, food processing, solar ponds, crystal growth, lubrication technologies and cooling of electrical and mechanical components. Researchers have been devoting much of their time in order to discover innovative methods to enhance the thermal conductivity of conventional fluids. With the development of nanotechnology, the concept of nanofluids has gained ground considerably as a new kind of heat transfer fluid. Nanofluid is a new kind of fluid with high thermal conductivity is a mixture of solid nanoparticles and a liquid. This review recapitulates the recent progress of the various numerical methods that are used in predicting the influence of several parameters such as type of nanoparticle and host liquid, particle volume concentration, particle size and shape, Brownian diffusion and thermophoresis effect on hydrodynamic and thermal characteristics of convective heat transfer using nanofluids in a lid driven cavity.
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Yang, Jinguang, Min Zhang, and Yan Liu. "Numerical simulations and optimizations for turbine-related configurations." Thermal Science 24, no. 1 Part A (2020): 367–78. http://dx.doi.org/10.2298/tsci190404295y.
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In order to accelerate the numerical simulation and optimization of gas turbine-related configurations, a source based computational fluid dynamics (SCFD) approach is developed for flow and heat transfer simulations. Different sources de-pending on the fluid porosity at each grid node in the computational domain are introduced to the continuity, momentum, energy and turbulence model equations, so that both the fluid and solid regions can be solved as one region. In the present paper, test cases including a ribbed channel and a winglet shrouded turbine cascade with tip injection are investigated using the SCFD and CFD with body-fitted meshes. Impacts of grid clustering and turbulence model equation sources on the SCFD precision are examined. Numerical results show that the SCFD predicts consistent aero-thermal performance with the fluid dynamics with body-fitted meshes and experiments. The validated SCFD scheme is then employed in a response surface optimization of tip jet holes on the winglet shroud tip. A jet arrangement with the minimum energy loss and injection mass-flow rate is obtained, indicating that source based predictions can be applied to the preliminary aero-thermal design of turbine blades.
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Kulkarni, Kaustubh G., Sanjay N. Havaldar, and Harsh V. Malapur. "Numerical Analysis of Central Solar Receivers with Various Geometries." International Journal of Heat and Technology 40, no. 1 (February 28, 2022): 339–46. http://dx.doi.org/10.18280/ijht.400141.
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Concentrated solar power (CSP) is a cutting-edge method of conserving renewable energy. The concentrated solar power is utilized as a heating source to increase the temperature of heat transfer fluid circulating in the piping of the central solar receiver. The solar central receiver is the most crucial part in solar tower power plants. In this study, a Computational Fluid Dynamics (CFD) framework was developed for analyzing four designs of the central tower receiver, namely, a conventional uniform tube diameter solar receiver (UTD), vertical variable tube diameter solar receiver (VTD), a circular solar variable tube diameter (CVTD) receiver and a leaf type circular solar receiver (LTSR). This analysis studied the solar radiation heat transfer efficiency, temperature distribution, and fluid outlet temperature; pressure and velocity distributions for the designs using CFD. It was found that the CVTD design helped achieve a higher rise in temperature of the heat transfer fluid (HTF) when the mass flow rate was in the range of 0.1 to 0.2 liter per minute. The CVTD and LSTR models of receiver were more efficient heat transfer receiver designs compared with other designs for same surface area and strength of beam radiations.
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Khan, Abdullah, Imran Shah, Waheed Gul, Tariq Amin Khan, Yasir Ali, and Syed Athar Masood. "Numerical and Experimental Analysis of Shell and Tube Heat Exchanger with Round and Hexagonal Tubes." Energies 16, no. 2 (January 12, 2023): 880. http://dx.doi.org/10.3390/en16020880.
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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 heat transfer is increased by introducing the hexagonal structure tubes, since it has better flow disruption as compared to the round tubes. We further validated our simulation results with experiments. For more accurate results, CFD is performed in counter and parallel flow and it is deduced that the rate of heat transfer directly depends upon the velocity of fluids and the number of turns of the tube.
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Azari, Ahmad, Abdorrasoul Bahraini, and Saeideh Marhamati. "A CFD technique to investigate the chocked flow and heat transfer characteristic in a micro-channel heat sink." International Journal of Computational Materials Science and Engineering 04, no. 02 (June 2015): 1550007. http://dx.doi.org/10.1142/s2047684115500074.
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In this research, a Computational Fluid Dynamics (CFD) technique was used to investigate the effect of choking on the flow and heat transfer characteristics of a typical micro-channel heat sink. Numerical simulations have been carried out using Spalart–Allmaras model. Comparison of the numerical results for the heat transfer rate, mass flow rate and Stanton number with the experimental data were conducted. Relatively good agreement was achieved with maximum relative error 16%, and 8% for heat transfer and mass flow rate, respectively. Also, average relative error 9.2% was obtained for the Stanton number in comparison with the experimental values. Although, the results show that the majority of heat was transferred in the entrance region of the channel, but the heat transfer in micro-channels can also be affected by choking at channel exit. Moreover, the results clearly show that, the location where the flow is choked (at the vicinity of the channel exit) is especially important in determining the heat transfer phenomena. It was found that Spalart–Allmaras model is capable to capture the main features of the choked flow. Also, the effects of choking on the main characteristics of the flow was presented and discussed.
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Bošnjaković, Mladen, and Simon Muhič. "Numerical Analysis of Tube Heat Exchanger with Perforated Star-Shaped Fins." Fluids 5, no. 4 (December 13, 2020): 242. http://dx.doi.org/10.3390/fluids5040242.
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This article discusses the possibility of further reducing the mass of the heat exchanger with stainless steel star-shaped fins while achieving good heat transfer performance. For this purpose, we perforated the fins with holes Ø2, Ø3, and Ø4 mm. Applying computational fluid dynamics (CFD) numerical analysis, we determined the influence of each perforation on the characteristics of the flow field in the liquid–gas type of heat exchanger and the heat transfer for the range of Re numbers from 2300 to 16,000. With a reduction in the mass of the fins to 17.65% (by Ø4 mm), perforated fins had greater heat transfer from 5.5% to 11.3% than fins without perforation. A comparison of perforated star-shaped fins with annular fins was also performed. Perforated fins had 51.8% less mass than annular fins, with an increase in heat transfer up to 26.5% in terms of Nusselt number.
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Khaldi, Souheyla, Abdel Illah Nabil Korti, and Said Abboudi. "Improving the Airflow Distribution Within an Indirect Solar Dryer by Modifications Based on Computational Fluid Dynamics." International Journal of Air-Conditioning and Refrigeration 25, no. 03 (September 2017): 1750022. http://dx.doi.org/10.1142/s2010132517500225.
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Successful drying requires a uniform heating of the product along the trays. This condition is a real challenge in the design of solar dryers. Studies show that a conventional solar dryer provides a nonuniform temperature distribution at the trays level. This paper seeks to remedy this problem by adding a second air inlet to the cabinet dryer in order to get a more homogeneous temperature. Unsteady turbulent airflow and heat transfer through a two-dimensional model is carried out for a typical day of August under the climatic conditions of Tlemcen (Algeria). Figs fruit was selected to be dried. The effect of the proposed configuration on the dynamic and thermal behaviors of the solar dryer has been discussed. The results revealed that using two opposite inlets can improve the drying process by reducing the fluctuation of the temperature to about 67% and increasing the mass flow rate by about 18%.
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Gault, R. I., D. J. Thornhill, and R. Fleck. "Alternative method to evaluate discharge coefficients. Part 2: Case study." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, no. 3 (December 1, 2008): 627–36. http://dx.doi.org/10.1243/09544062jmes1075.
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The purpose of this article is to apply an alternative method whereby discharge coefficients can be estimated for the flow through a poppet valve at various lifts. Presented is the development of an operational quasi-steady flow rig. An engine cylinder head poppet valve was used as the case study. The requirement to directly measure mass flowrates using a standard conventional steady flow apparatus has been eliminated. Transient mass flowrates, pressures and temperatures of air during an inflow test for a poppet valve at various lifts were measured. Mass flowrates were also calculated from measured cylinder gas pressures and corrected for heat transfer. Using both methods to determine the mass flowrates, isentropic discharge coefficients were calculated and shown to compare within>4.0 per cent of steady flow data. A computational fluid dynamics (CFD) validation of the quasi-steady flow rig is also presented.
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Dragan, Valeriu. "CENTRIFUGAL COMPRESSOR EFFICIENCY CALCULATION WITH HEAT TRANSFER." IIUM Engineering Journal 18, no. 2 (December 1, 2017): 225–37. http://dx.doi.org/10.31436/iiumej.v18i2.695.
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In this paper we present a case study of apparent performance variation ofan optimized centrifugal compressor design when its metal parts are cold - before the conjugated heat transfer between the fluid and parts reaches an energetic equilibrium. The methods used are numerical, using full viscous 3D computational fluid dynamics with heat transfer. Three cases were considered, an adiabatic wall baseline, an all-blade cooling at 293 K and a more realistic stator row cooling at 293 K. Results indicate an apparent yet erroneous isentropic efficiency reading increase beyond 100% - which was to be expected due to the fluid cooling. However the isentropic and polytropic efficiencies could be estimated and were used to more accurately assess the performance of the compressor. Power consumption decreased to approximately 97% of the original load while the pressure ratio was marginally increased. This alone does not, however, explain the non-physical efficiency readings, which are mainly due to the assumptionsand manner under which the efficiency itself is calculated. The paper presents a more robust approach to measuring efficiency, regardless of the heat transfer within the turbomachinery itself. Possible applications of the study may range from cold-start regime simulation to the optimization of inter-cooling setup or even flow angle control without mechanically actuated OGV
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Afrasiabian, Ehsan, Oleg Iliev, Inga Shklyar, Torben Prill, Carlo Isetti, and Stefano Lazzari. "3D-CFD analysis of the effect of cooling via minitubes on the performance of a three-fluid combined membrane contactor." International Journal of Low-Carbon Technologies 14, no. 3 (July 10, 2019): 400–409. http://dx.doi.org/10.1093/ijlct/ctz033.
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Abstract A 3D computational fluid dynamics model was adopted to study the effects of internal cooling on the performance of a three-fluid combined membrane contactor (3F-CMC), in the presence of minitubes in solution and a spacer in the air channel. This compact 3F-CMC is part of a hybrid climate-control system, recently developed for serving in electric vehicles. For the studied operating conditions, results show that the absorption and sensible effectiveness parameters increase up to 77% and 124% by internal cooling, respectively. This study also reports 3D flow effects on the heat and mass transfer enhancement inside the contactor, with implications for further design improvements.
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Olia, Hamed, Mohammadamin Torabi, Mehdi Bahiraei, Mohammad Hossein Ahmadi, Marjan Goodarzi, and Mohammad Reza Safaei. "Application of Nanofluids in Thermal Performance Enhancement of Parabolic Trough Solar Collector: State-of-the-Art." Applied Sciences 9, no. 3 (January 29, 2019): 463. http://dx.doi.org/10.3390/app9030463.
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The present review paper aims to document the latest developments on the applications of nanofluids as working fluid in parabolic trough collectors (PTCs). The influence of many factors such as nanoparticles and base fluid type as well as volume fraction and size of nanoparticles on the performance of PTCs has been investigated. The reviewed studies were mainly categorized into three different types of experimental, modeling (semi-analytical), and computational fluid dynamics (CFD). The main focus was to evaluate the effect of nanofluids on thermal efficiency, entropy generation, heat transfer coefficient enhancement, as well as pressure drop in PTCs. It was revealed that nanofluids not only enhance (in most of the cases) the thermal efficiency, convection heat transfer coefficient, and exergy efficiency of the system but also can decrease the entropy generation of the system. The only drawback in application of nanofluids in PTCs was found to be pressure drop increase that can be controlled by optimization in nanoparticles volume fraction and mass flow rate.
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Campos, Julio Cesar Costa, Albino J. K. Leiroz, and Maysa T. Resende. "Analysis of Wood Biomass in Bubbling Fluidized Bed Reactors." Applied Mechanics and Materials 798 (October 2015): 475–79. http://dx.doi.org/10.4028/www.scientific.net/amm.798.475.
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This article analysis the computational simulation of wood's gasification in a bubbling fluidized bed reactor. Most articles about this topic, on homogenous reactions, don’t consider methane reforming. However, this article has taken this into consideration in the process of gasification. The bubbling fluidized bed reactor was used in the simulation, in which the advantages of a good mixture is presented, one which provides high rates of mass and heat transfer. The gas-solid flow that occurs in this reactor was described through mass, energy, momentum, and chemical species balances. The model used for the simulation was the computational fluid dynamics (CFD), by means of an open-source program named MFIX (Multiphase Flow with Interphase eXchange). It is concluded that methane reforming is important in the process of gasification.
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Navickaitė, Kristina, Michael Penzel, Christian R. H. Bahl, and Kurt Engelbrecht. "Performance Assessment of Double Corrugated Tubes in a Tube-In-Shell Heat Exchanger." Energies 14, no. 5 (March 1, 2021): 1343. http://dx.doi.org/10.3390/en14051343.
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In this article, the performance of double corrugated tubes applied in a tube-in-shell heat exchanger is analysed and compared to the performance of a heat exchanger equipped with straight tubes. The CFD (computational fluid dynamics) analysis was performed considering a turbulent flow regime at several mass flow rates. It is observed that the double corrugated geometry does not have a significant impact on the pressure drop inside the analysed heat exchanger, while it has the potential to increase its thermal performance by up to 25%. The ε–NTU (effectiveness–number of transfer units) relation also demonstrates the advantage of using double corrugated tubes in tube-in-shell heat exchangers over straight tubes.
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Pezo, Milada, and Vladimir Stevanovic. "Numerical prediction of nucleate pool boiling heat transfer coefficient under high heat fluxes." Thermal Science 20, suppl. 1 (2016): 113–23. http://dx.doi.org/10.2298/tsci150701138p.
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This paper presents CFD (Computational Fluid Dynamics) approach to prediction of the heat transfer coefficient for nucleate pool boiling under high heat fluxes. Three-dimensional numerical simulations of the atmospheric saturated pool boiling are performed. Mathematical modelling of pool boiling requires a treatment of vapor-liquid two-phase mixture on the macro level, as well as on the micro level, such as bubble growth and departure from the heating surface. Two-phase flow is modelled by the two-fluid model, which consists of the mass, momentum and energy conservation equations for each phase. Interface transfer processes are calculated by the closure laws. Micro level phenomena on the heating surface are modelled with the bubble nucleation site density, the bubble resistance time on the heating wall and with the certain level of randomness in the location of bubble nucleation sites. The developed model was used to determine the heat transfer coefficient and results of numerical simulations are compared with available experimental results and several empirical correlations. A considerable scattering of the predictions of the pool boiling heat transfer coefficient by experimental correlations is observed, while the numerically predicted values are within the range of results calculated by well-known Kutateladze, Mostinski, Kruzhilin and Rohsenow correlations. The presented numerical modeling approach is original regarding both the application of the two-fluid two-phase model for the determination of heat transfer coefficient in pool boiling and the defined boundary conditions at the heated wall surface.
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Alanazi, Meznah M., Awatif A. Hendi, N. Ameer Ahammad, Bagh Ali, Sonia Majeed, and Nehad Ali Shah. "Significance of Ternary Hybrid Nanoparticles on the Dynamics of Nanofluids over a Stretched Surface Subject to Gravity Modulation." Mathematics 11, no. 4 (February 5, 2023): 809. http://dx.doi.org/10.3390/math11040809.
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Boosting the heat transfer rate in a base fluid is of interest to researchers; many traditional methods have been utilized to do this. One significant way is using nanofluid to boost thermal performance. This investigation sought to improve the transmission of a thermal above-stretching inclined surface over an upper surface to be influenced by the magnetic field B0 along the microgravity g*(τ)=g0(1+acos(πωt)). The G-jitter impacts were analyzed for three colloidal fluids flow; the mono micropolar nanofluid (alumina/water), micropolar hybrid nanofluid (alumina–titanium)/water, and micropolar trihybrid nanofluid (alumina–titanium–silicon)/water. Using suitable transformation, the governing formulation was changed into an ordinary differential equation. In a Matlab script, a computational code was composed to evaluate the impacts of the involved parameters on fluid dynamics. The fluid flow motion and thermal performance for the trihybrid case were greater than the mono and hybrid nanofluid cases subject to a microgravity environment. The fluid velocity and microrotation function decreased in opposition to the magnetic parameter’s increasing strength, but with an increasing trend in the fluid temperature function. Fluctuations in the velocity gradient and heat flow gradient increased as the modulation amplitude increased.
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Florio, Laurie A. "Direct simulation of thermally and mechanically coupled particle-laden flow." SIMULATION 98, no. 5 (October 30, 2021): 363–87. http://dx.doi.org/10.1177/00375497211055104.
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This work describes a unique technique to simulate continuously and directly coupled fluid flow and moving particles including both mechanical and thermal interactions between the flow, particles, and flow paths. The particles/flow paths are discretized within a computational fluid dynamics flow domain so that the local flow and temperature field conditions surrounding each particle or other solid body are known along with the local temperature distribution within the particle and other solids. Contact conduction between solid bodies including contact resistance, conjugate heat transfer at the fluid–solid interfaces, and even radiation exchanges between solid surfaces and between solid surfaces and the fluid are incorporated in the thermal interactions and a soft collision model simulates the solid body mechanical contact. The ability to capture these local flow and thermal effects removes reliance on correlations for fluid forces and for heat transfer coefficients/exchange and removes restrictions on the flow regime and particle size and volume fraction considered. Larger particle sizes and higher particle concentration conditions can be studied with local effects captured. The method was tested for a range of particle thermal and mechanical properties, driving pressures, and for limited radiation parameters. The results reveal important information about the basic thermal and flow phenomena that cannot be obtained in standard modeling methods and demonstrate the utility of the modeling method. The technique can be applied to examine phenomena dependent on local thermal conditions such as chemical reactions, material property variation, agglomerate formation, and phase change. The methods can also be used as a basis for machine learning algorithm development for flows with large particle counts so that more detailed phenomena can be considered compared to those provided by standard techniques with reduced computational costs compared to those with fully resolved particles in the flow.