Journal articles on the topic 'Inlets Mathematical models'
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Jelenčiaková, Nina, Bojan Petrović, Sanja Kojić, Jovana Jevremov, and Stevan Hinić. "Application of Mathematical Models and Microfluidics in the Analysis of Saliva Mixing with Antiseptic Solutions." Balkan Journal of Dental Medicine 24, no. 2 (July 1, 2020): 84–90. http://dx.doi.org/10.2478/bjdm-2020-0014.
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SummaryBackground/Aim: Human saliva offers many advantages over blood-based biochemical assays, therefore, becomes the biological fluid of interest. Once antiseptic solutions react with saliva, both fluids undergo significant changes of their biophysical properties, consequently, those changes have an impact on their principal function.Material and Methods: In this study, saliva was collected and mixed with 0,1% chlorhexidine digluconate solution, fluoride mouthwash, zinc-hydroxyapatite solution and CPP-ACP paste. Microfluidic PVC/Green tape chips within the experimental setup were used to simulate solution mixing. The chip had 2 inlets and 1 outlet, and channel was designed in Y shape without any obstacles. The inlet channels were set at a 60° angle. The channel width was 600 µm and the diameter of inlets and outlet was 2 mm. For better visualization, blue food coloring was added to the saliva. The procedure was recorded with digital USB microscope camera and afterwards the percentage of mixing was obtained by MATLAB programming language.Results: Obtained results show incomplete mixing of all the solutions with saliva. The value of mixed liquid, when mixing 0,1% chlorhexidine digluconate solution with saliva was 51,11%. In case of medium concentration fluoride mouthwash, result was 84,37%. Zinc hydroxyapatite solution obtained result of 85,24%, and the fourth tested solution, CPP-ACP paste, 83,89%.Conclusions: Analyzed mouthwashes exhibit specific, non uniform behavior during mixing with saliva. Microfluidic setups could be efficiently used in simulating real clinical conditions in laboratory settings. Image processing mathematical models are applicable, accurate and useful in determination of the interaction of saliva with commonly used antiseptic solutions.
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Wan, Wen Jun, Zhi Yuan Fan, Wei Jian Huang, and Shi He Chen. "Dynamic Characteristics and Mathematical Models of Filled Level for Ball Mills with Double Inlets and Outlets." Advanced Materials Research 1008-1009 (August 2014): 988–94. http://dx.doi.org/10.4028/www.scientific.net/amr.1008-1009.988.
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Ball mills with double inlets and outlets (BMDIO) are widely equipped in milling systems of thermal power plants because of BMDIOs’ vantage on being able to pulverize various raw coal. In this paper, dynamic characteristics of mill’s coal level were studied by pulverizing coal mechanism analysis. Furthermore, models for filled level of mill were obtained with mathematical Equations. The nonlinear, strong coupling and large lag features of BMDIO’s dynamic characteristics were demonstrated by the model for level of materiel constructed in this paper. And, the model would be become the available theory basis for the calculation of pulverized coal into furnace and design of combustion in fossil-fired thermal unit.
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Qiu, Shu Xia, and Ning Pang. "A Numerical Study on the Flow Characteristics of Opposed Impinging Jets." Advanced Materials Research 516-517 (May 2012): 854–57. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.854.
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Inspired by the increasing interests on mixing effectiveness of opposed impinging jets, a numerical work is carried out to study the flow characteristics. The fluid temperature is used as a passive tracer to evaluate the mixing rate in the current mathematical models. The effect of Reynolds number on the mixing performance is discussed. Furthermore, in order to enhance the mixing efficiency and reduce the energy cost, unsteady flow pulsations are induced at the jet inlets. The numerical results indicate that the mixing efficiency can be improved by the unsteady flow pulsations via adjusting the hydrodynamics characteristics in the opposed jets.
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Djordjević, S., D. Prodanović, Č. Maksimović, M. Ivetić, and D. Savić. "SIPSON – Simulation of Interaction between Pipe flow and Surface Overland flow in Networks." Water Science and Technology 52, no. 5 (September 1, 2005): 275–83. http://dx.doi.org/10.2166/wst.2005.0143.
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The new simulation model, named SIPSON, based on the Preissmann finite difference method and the conjugate gradient method, is presented in the paper. This model simulates conditions when the hydraulic capacity of a sewer system is exceeded, pipe flow is pressurized, the water flows out from the piped system to the streets, and the inlets cannot capture all the runoff. In the mathematical model, buried structures and pipelines, together with surface channels, make a horizontally and vertically looped network involving a complex interaction of flows. In this paper, special internal boundary conditions related to equivalent inlets are discussed. Procedures are described for the simulation of manhole cover loss, basement flooding, the representation of street geometry, and the distribution of runoff hydrographs between surface and underground networks. All these procedures are built into the simulation model. Relevant issues are illustrated on a set of examples, focusing on specific parameters and comparison with field measurements of flooding of the Motilal ki Chal catchment (Indore, India). Satisfactory agreement of observed and simulated hydrographs and maximum surface flooding levels is obtained. It is concluded that the presented approach is an improvement compared to the standard “virtual reservoir” approach commonly applied in most of the models.
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Fang, Zhicheng, Wanjiang Wang, Yanhui Chen, and Junkang Song. "Structural and Heat Transfer Model Analysis of Wall-Mounted Solar Chimney Inlets and Outlets in Single-Story Buildings." Buildings 12, no. 11 (October 26, 2022): 1790. http://dx.doi.org/10.3390/buildings12111790.
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Wall-mounted solar chimneys use solar radiation to heat the air inside the chimney cavity and use thermal pressure to create natural convection. Applying this principle allows for the indoor ventilation of a building without energy consumption. However, in wall-mounted solar chimney designs, different air inlet and outlet design dimensions can have varying degrees of impact on the effectiveness of wall-mounted solar chimney ventilation. In order to analyze the internal airflow state and airflow temperature field distribution of wall-mounted solar chimneys, physical models of wall-mounted solar chimneys with six different air outlet-to-inlet cross-sectional area ratios were developed in this research work. Before numerical simulation analysis, heat transfer analysis of the wall-mounted solar chimney’s structural components and airflow channels was carried out, and corresponding mathematical heat transfer models were established. The internal flow state and temperature distribution characteristics of a wall-mounted solar chimney were analyzed by steady-state simulations using the computational fluid dynamics software, Ansys Fluent. Finally, transient simulation calculation analysis was conducted under six different S-value models to investigate the variation in the natural ventilation of a single-story building’s wall-mounted solar chimney for a whole day. The study showed that under the same simulation conditions, 80% ≤ S < 100% effectively avoided the formation of vortices in the internal airflow of the wall-mounted solar chimneys and kept the ventilation effect of wall-mounted solar chimneys at a high level. The results of this study provide a reference for the optimization of research on the design of the air inlet and outlet structures of wall-mounted solar chimneys for single-story buildings.
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Pylypenko, O. V., O. O. Prokopchuk, S. I. Dolgopolov, O. D. Nikolayev, N. V. Khoriak, V. Yu Pysarenko, I. D. Bashliy, and S. V. Polskykh. "Mathematical modelling of start-up transients at clustered propulsion system with POGO-suppressors for CYCLON-4M launch vehicle." Kosmìčna nauka ì tehnologìâ 27, no. 6 (2021): 3–15. http://dx.doi.org/10.15407/knit2021.06.003.
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Liquid-propellant rocket propulsion systems of the first stages of launch vehicles of medium, heavy, and super-heavy class usually include POGO-suppressors, which are one of the most widely used methods to eliminate launch vehicle longitudinal structural vibrations (POGO phenomena). However, until now, the theoretical studies and analysis of the effect of the POGO-suppressors’ installation in the feedlines of main liquid rocket engines on transient processes in systems during rocket engine starting have not been carried out due to the complexity of such analysis and the lack, first of all, reliable nonlinear models of cavitation phenomena in rocket engine pumps. A mathematical model for the start-up of a clustered rocket propulsion of the Cyclone-4M launch vehicle has been developed that takes into account the low-frequency dynamics of the POGO-suppressors and the asynchronous start-up timeline sequences of the rocket engines. The first stage of the launch vehicle propulsion system includes four RD-870 rocket engines. A nonlinear mathematical model of low-frequency dynamic processes of the POGO-suppressor with bellows separation of liquid and gaseous media is presented. A significant effect of cavitation in the pumps of engines and the POGO-suppressor installation to the LOX feedline on the propulsion system dynamic gains is shown. Based on the developed mathematical model of the clustered rocket propulsion start-up, the studies of the Cyclone-4M main engines’ start-up transients were carried out. The asynchronous start-up timeline sequences of the rocket engine and the places of installation of the POGO-suppressors in the LOX feedline branches to the RD-870 rocket engine – near the general feedline collector as standard placement or directly at the entrance to the engines – were investigated. The analysis of start-up transients in the oxidizer feed system of the considered propulsion (the time dependences of the flowrate and pressure at the engine inlet) showed the following. Firstly, while the synchronous start-up of the engines, the installation of the POGO-suppressors near the feedline collector makes it possible to eliminate all engine inlet overpressures that exist in the rocket propulsion system in case of the absence of the POGO-suppressors. Secondly, the RD-870 engine asynchronous start-up operation affects negatively the time dependences of the propellant flowrate and pressure at the engine inlet if the POGO-suppressors are located near the feedline collector. So, in the propulsion system’s start-up timeline interval 0.95 s - 1.35 s, for some computational variants of the initial moments of the engine operation start, an abnormally large drop in the LOX flow rate and the overpressures at the engine inlet is observed. The asynchronous start-up of the RD-870 engines with the installation of the POGO-suppressors at the engine inlet does not significantly change the start-up transients compared to the synchronous starting of the engines. Thirdly, thus, it is shown that the installation of the POGO-suppressors both at the engine inlet and at the RD-870 branches near the collector has a significant positive effect on the quality of start-up transient processes for the main engines of the 1st stage of the Cyclone-4M launch vehicle. Placing the POGO-suppressors at the engine inlets is not standard and is considered without reference to the propulsion system layout. Nevertheless, the POGO-suppressors installed at the inlet to the engines are an effective means of preventing overshoots and dips in the parameters of the liquid-propellant rocket engine, including the conditions of asynchronous starting of the liquid rocket engines in the clustered propulsion system. The results obtained can be used in mathematical modeling of the start-up of the first stage propulsion system either for multistage sustainer rockets used in parallel with booster rockets or for the clustered multi-engine rocket propulsion system containing POGO-suppressors.
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Iwanowicz, Damian. "Assessment of selected methods of estimating the maximum back-of-queue size on a signal-controlled intersection approach." Journal of Civil Engineering and Transport 4, no. 2 (December 31, 2022): 49–63. http://dx.doi.org/10.24136/tren.2022.008.
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The article presents the characteristics and evaluation of the accuracy of estimating the maximum length of the queue of vehicles at signalized intersections by commonly used methods in the world. The analyzes were based on the latest editions of the guidelines in the United States, Canada, Australia, Germany and Poland. In order to carry out accuracy analyzes, traffic tests were carried out at 5 intersection inlets in three different cities in Poland (Bydgoszcz, Torun, Warsaw), covering all phases of vehicle queue formation during individual periods of the signaling cycle (effective red and green signal). In total, the analysis had the results of tests from 81 hours of observation ~23,000 behaviors of vehicle drivers. Based on the analyzes it was found in particular: (1) slight differences in the construction of mathematical models of the considered calculation methods, with the exception of the US HCM model from 2016; (2) small errors in estimating the maximum queue length in unsaturated vehicle flow states (~3-5 vehicles/cycle and ~2-6 vehicles/15 minutes interval); (3) quite large errors in estimating the maximum queue length in saturated and oversaturated vehicle flow states (~11-16 vehicles/cycle and ~15-18 vehicles/15 minutes interval); (4) the main impact on estimation errors in oversaturation traffic states is not taking into account or incorrect determination of the 'so-called' initial queue length of the period preceding the analyzed period.
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Chiu, Min-Chie, and Ying-Chun Chang. "An Assessment of High-Order-Mode Analysis and Shape Optimization of Expansion Chamber Mufflers." Archives of Acoustics 39, no. 4 (March 1, 2015): 489–99. http://dx.doi.org/10.2478/aoa-2014-0053.
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Abstract A substantial quantity of research on muffler design has been restricted to a low frequency range using the plane wave theory. Based on this theory, which is a one-dimensional wave, no higher order wave has been considered. This has resulted in underestimating acoustical performances at higher frequencies when doing muffler analysis via the plane wave model. To overcome the above drawbacks, researchers have assessed a three-dimensional wave propagating for a simple expansion chamber muffler. Therefore, the acoustic effect of a higher order wave (a high frequency wave) is considered here. Unfortunately, there has been scant research on expansion chamber mufflers equipped with baffle plates that enhance noise elimination using a higher-order-mode analysis. Also, space-constrained conditions of industrial muffler designs have never been properly addressed. So, in order to improve the acoustical performance of an expansion chamber muffler within a constrained space, the optimization of an expansion chamber muffler hybridized with multiple baffle plates will be assessed. In this paper, the acoustical model of the expansion chamber muffler will be established by assuming that it is a rigid rectangular tube driven by a piston along the tube wall. Using an eigenfunction (higher-order-mode analysis), a four-pole system matrix for evaluating acoustic performance (STL) is derived. To improve the acoustic performance of the expansion chamber muffler, three kinds of expansion chamber mufflers (KA-KC) with different acoustic mechanisms are introduced and optimized for a targeted tone using a genetic algorithm (GA). Before the optimization process is performed, the higher-order-mode mathematical models of three expansion chamber mufflers (A-C) with various allocations of inlets/outlets and various chambers are also confirmed for accuracy. Results reveal that the STL of the expansion chamber mufflers at the targeted tone has been largely improved and the acoustic performance of a reverse expansion chamber muffler is more efficient than that of a straight expansion chamber muffler. Moreover, the STL of the expansion chamber mufflers will increase as the number of the chambers that separate with baffles increases.
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Chang, Juntao, Lei Wang, and Wen Bao. "Mathematical modeling and characteristic analysis of scramjet buzz." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 228, no. 13 (January 29, 2014): 2542–52. http://dx.doi.org/10.1177/0954410014521055.
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Buzz is an important issue for a scramjet engine. A mathematical model of buzz oscillations is necessary for control system design. Control-oriented models of hypersonic vehicle propulsion systems require a reduced-order model that is accurate to some extent but requires less than a few seconds of computational time. To achieve this goal, a reduced-order model of buzz oscillations for a scramjet engine is built by introducing the modeling idea of Moore–Greitzed model for compressors. The introduction of characteristic lines avoids the complex interactions in hypersonic inlet, such as shock–shock interactions and shock–boundary layer interaction. And the inlet characteristics are obtained from the pressure signal of combustor. Based on the established buzz model, we can predict the inlet performance, characterize the stability margin of inlet, reflect the oscillatory characteristics of inlet buzz including the dominant amplitude and frequency and describe the transition process of inlet buzz.
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Chernova, A. A. "Validation of RANS Turbulence Models for the Conjugate Heat Exchange Problem." Nelineinaya Dinamika 18, no. 1 (2022): 61–82. http://dx.doi.org/10.20537/nd220105.
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This paper addresses problems of mathematical modeling of heat exchange processes in the pre-nozzle volume of a solid propellant rocket engine with a charge with starlike cross-section and a recessed hinged nozzle. Methods of mathematical modeling are used to solve the quasi-stationary spatial conjugate problem of heat exchange. An analysis is made of the influence of RANS turbulence models on the flow structure in the flow channels of the engine and on the computed heat flow distributions over the surface of the recessed nozzle. Methods of mathematical modeling are used to solve the quasi-stationary spatial conjugate problem of heat exchange. Results of validation of RANS turbulence models are presented using well-known experimental data. A comparison of numerical and experimental distributions of the heat-transfer coefficient over the inlet surface of the recessed nozzle for the engine with a cylindrical channel charge is made for a primary choice of turbulence models providing a qualitative agreement between calculated and experimental data. By analyzing the results of numerical modeling of the conjugate problem of heat exchange in the combustion chamber of the solid propellant engine with a starlike channel, it is shown that the SST $k-\omega$ turbulence model provides local heat-transfer coefficient distributions that are particularly close to the experimental data.
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Smith, W. R., G. C. Wake, J. E. McIntosh, R. P. McIntosh, M. Pettigrew, and R. Kao. "Mathematical analysis of perifusion data: models predicting elution concentration." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 261, no. 1 (July 1, 1991): R247—R256. http://dx.doi.org/10.1152/ajpregu.1991.261.1.r247.
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System models are constructed and analyzed for combined convective flow and for dispersion in distorting concentrations of a chemical signal as it passes through a packed column. We derive general analytical solutions for these models. The results have applications to analyses such as in biological experiments involving hormonal stimulation of perifused cells, elution chromatography, adsorption columns, and studies of groundwater flow. The models reveal that the column distorts an incoming signal (such as a change in solute concentration in the flowing liquid) at the inlet. This distortion is greatest at low values of the Peclet number of the flow and is small at larger values. We explore the effects of the approximations inherent in the mathematical models of the system. Specification of the boundary conditions of the problem are shown to be particularly important. With the use of incorrect models, it is possible to obtain accurate interpolations to data obtained from perfusion experiments. However, the parameters derived (in particular the dispersion constant and the peak concentration of a solute concentration pulse) may be considerably in error. This may lead to errors when these parameter estimates are used to predict results in other experimental situations.
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Fang, Jian Hua, Qiang Ji, Yi Qi Zhou, and De Li Zhu. "Research on Relation among Inlet/Outlet Pressure, Pressure Loss and Inlet Velocity of a Complex Resistance Muffler." Applied Mechanics and Materials 477-478 (December 2013): 858–63. http://dx.doi.org/10.4028/www.scientific.net/amm.477-478.858.
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Simulation models of resistance mufflers with different typical structures were established, through the computational fluid dynamics method, under the conditions of different inlet velocities, by analyzing distribution characteristic of velocity field and pressure field for flows internal the mufflers, a kind of mathematical relation among the inlet velocity, inlet/outlet pressure, and pressure loss was discovered. Through CFD simulation computation and practical measuring tests of above three parameters for practical muffler with complex configurations, the mathematical relation of them was proved to be correct. With the conclusion, while inlet velocity changed, the variable conditions of inlet/outlet pressure and pressure loss for resistance mufflers could be estimated approximately Therefore, the test expense could be saved, and the designing efficiency for mufflers could also be further improved, so it would bring a certain economic benefit,which would be of great significance for energy saving research of mufflers.
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Huang, Zhi-gang, Yun-xuan Weng, Nan Fu, Zong-qiang Fu, Dong Li, and Xiao Dong Chen. "Modeling and Simulation of a Co-current Rotary Dryer." International Journal of Food Engineering 12, no. 2 (March 1, 2016): 189–94. http://dx.doi.org/10.1515/ijfe-2015-0159.
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Abstract Mathematical models including mass and energy conservation were developed in order to predict the outlet particles temperature and moisture. As the inlet air temperature increased, the outlet particles temperature increased as well and the outlet particles moisture decreased quickly. The outlet particles temperature and moisture changed a little as a function of the speed of rotation at the low inlet air temperature, while the outlet particles temperature and moisture increased very apparently with the speed of rotation increased at the high inlet air temperature. The error of the simulation results compared to the experimental data showed good accuracy for particles temperature and moisture content. The mathematical model performs well to predict the outlet particles temperature and moisture content.
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Жорник, Олег Володимирович, Ігор Федорович Кравченко, Михайло Михайлович Мітрахович, and Олеся Валеріїна Денисюк. "Обґрунтування моделі турбулентної в’язкості для дослідження характеристик співвісного гвинтовентилятора і вхідного пристрою ГТД." Aerospace technic and technology, no. 4 (August 27, 2021): 35–39. http://dx.doi.org/10.32620/aktt.2021.4.05.
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The issues of substantiation of the most rational, based on adequacy, model of turbulent viscosity for mathematical modeling of the flow near the propfan and in the inlet of the turbine-propeller engine are considered. It was found that at present there is no universal turbulence model for determining the parameters of the boundary layer, energy loss in the flow, and laminar-turbulent transition. Analysis of the results of previous studies showed that there is a need to select and justify a turbulent viscosity model for each type of research object. The task of modeling the flow near the propfan and in the inlet device of the power plant was performed using the ANSYS CFX software product, which allows using various standard mathematical models and tools for modeling turbulent flow. The object of research is an annular axial inlet device, in front of which there is a coaxial propfan with two rows of propellers: the first row has eight blades, the second - six. 7 types of models of turbulent viscosity, which most fully describe the phenomena in the flow around the propfan and the inlet device, have been investigated: k-ωmodel; SSТ (shear stress transport) SST Transitional №1 Fully turbulence; SST Transitional №2 Specified Intermittency; SST Transitional №3 Gamma model; SST Transitional №4 Gamma theta model; SST Transitional №5 Intermittency. The results of mathematical modeling of the flow near the propfan and in the inlet device at the corresponding operating mode of the turbopropfan engine using the selected models of turbulent viscosity, the total pressure value in front of and behind the inlet device was obtained to determine the total pressure recovery coefficient in it and the value of the propfan thrust. The value of the recovery factor of the total pressure in the inlet device and the propfan thrust are compared with the flight test data of the prototype. An analysis of the comparison of the values of the total pressure recovery factor in the inlet device and the propfan thrust showed that the use of the SST Transitional №4 Gamma theta model allows obtaining the value of the total pressure recovery factor in the inlet device and the propfan thrust that is closest to the flight test results.
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Chekurin, Vasyl, and Olga Khymko. "Mathematical models for leak identification in long-distance gas pipeline. Stationary operational mode." Physico-mathematical modelling and informational technologies, no. 25 (May 25, 2017): 157–69. http://dx.doi.org/10.15407/fmmit2017.25.157.
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Direct and inverse problems for leak identification in long distance gas pipelines in stationary operational modes on the base of data obtained by pressure monitoring in pipeline’s inlet, outlet and in several intermediate check points have been formulated. Algorithms for solving of the formulated problems have been developed and their numerical study has been done. On this basis methods for leak detecting, its intensity and location determination with the use of the data of pressure monitoring have been suggested. Quantitative evaluation of precisions of the proposed methods has been conducted.
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Michalski, Jerzy, and Tadeusz Frączek. "Mathematical models of the change in composition of the inlet atmosphere for the assumed changes in the nitrogen potential." Inżynieria Powierzchni 25, no. 1-2 (November 3, 2020): 5–13. http://dx.doi.org/10.5604/01.3001.0014.4474.
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The development of gas nitriding and the systematic expansion of its scope of application in practice means that the issue of the production of nitrided layers on steels is still in the center of interest of industry and research centers from both a cognitive and application point of view. Research mainly focuses on determining the relationship between the construction of the nitrided layer and its production parameters. The condition of full control of the nitriding process effect is the control of the nitrogen availability of the nitriding atmosphere, which depends on the value of the nitrogen potential (Np) and the degree of ammonia dissociation (α). Shaping of these parameters is carried out by controlling and regulating the composition of the inlet atmosphere. Control and regulation of the inlet atmosphere composition is important in controlling the nitrogen availability of the nitriding atmosphere and, consequently, the kinetics of nitrided layer thickness increase. The article describes models for changing the composition of the three-component and two-component inlet atmosphere. Two variants of controlling and regulating the nitrogen potential are discussed: the composition of the two-component inlet atmosphere, dissociated ammonia-ammonia and the temperature function in the heating stage of the charge.
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Vozniak, Orest, Volodymyr Dovhaliuk, Iryna Sukholova, and Oleksandr Dovbush. "Mathematical Simulation of a Twisted Inlet Jet at Variable Mode with Using Various Turbulence Models." Ventilation, Illumination and Heat Gas Supply, no. 31 (December 1, 2019): 6–15. http://dx.doi.org/10.32347/2409-2606.2019.31.6-15.
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Azadi, Mohsen, and Mehdi Azadi. "An analytical study of the effect of inlet velocity on the cyclone performance using mathematical models." Powder Technology 217 (February 2012): 121–27. http://dx.doi.org/10.1016/j.powtec.2011.10.017.
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Zhang, Song Bo, and Jing Lv. "Performance Analysis and Numerical Simulation in Elliptical Tubes." Advanced Materials Research 291-294 (July 2011): 3354–58. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.3354.
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By using the FLUENT software, the flow and heat transfer properties of several elliptical tubes were numerically studied. The mathematical models of the tubes flow field were established. The implementation incorporated a SMPLE-based semi-implicit solution algorithm that was applied to iterating calculation. Results shows that the surface heat transfer coefficient, temperature difference between inlet and outlet were all higher than circular tube, when mass flux equal to at inlet of elliptical tubes and circular tube and wall temperature was invariable. Therefore, the elliptical tube is a kind of effective heat transfer enhancement element.
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Mu, Zhen Ying. "Study on Application of Solar Heating System Integrated Latent Heat Store Heat Exchanger." Applied Mechanics and Materials 291-294 (February 2013): 158–61. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.158.
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This paper introduces the design of a solar heating system integrated latent heat store heat exchanger. Aiming at studying the system solar fraction, mathematical models are established for describing solar collector, latent heat store heat exchanger, users’ heating thermal load, and the system in whole. Studies are carried out based on these models. The results show that there are some key influencing factors on solar fraction, including solar irradiance, collector area, collector inclination angle, the difference value between collector inlet fluid temperature and ambient air temperature. Among these, collector inclination angle is the most significant one. If the values between collector inlet fluid temperature and ambient air temperature have big difference, it’ll cause adverse effects. As long as the operation requirements are met, lower collector inlet fluid temperature and suitable ambient air temperature are reasonable conditions for application. The research results provide guide for the system application in engineering.
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Myhan, Ryszard, and Marek Markowski. "Generalized Mathematical Model of the Grain Drying Process." Processes 10, no. 12 (December 19, 2022): 2749. http://dx.doi.org/10.3390/pr10122749.
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Convective cereal grain drying is an energy-intensive process. Mathematical models are applied to analyze and optimize grain drying processes in different types of dryers and in different stages of drying to improve final grain quality and reduce energy consumption. The aim of the present study was to develop a generalized mathematical model of the grain drying process that accounts for all drying stages, including loading and unloading of unprocessed grain, drying, and cooling of dry grain. The developed mathematical model is a system of algebraic equations, where the calculated coefficients are determined by the thermophysical and diffusive properties of dried grain. The model was validated for batch drying of wheat, canola, and corn grain, as well as continuous flow drying of wheat grain. The results were compared with published findings. The relationships between energy consumption during drying and drying time vs. air temperature at the dryer inlet and air stream volume were determined. Dryer capacity and drying conditions specified by the manufacturers, as well as loading and unloading capacity, were considered during batch drying. Continuous flow drying simulations were conducted in counter-flow, parallel-flow, and cross-flow mode. Simulation results indicate that the proposed models correctly depicted process flow in both batch and continuous flow dryers.
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Yang, Xiaoping, and Zhuodi Cai. "Thermodynamic performance analysis of supercritical carbon dioxide Brayton cycle." Thermal Science, no. 00 (2020): 294. http://dx.doi.org/10.2298/tsci200314294y.
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S-CO2 (supercritical carbon dioxide) is used as working fluid for power system cycle. This paper presents thermodynamic performance analysis results on S-CO2 Brayton cycle. Based on the assumptions of the relevant initial parameters, the mathematical models of compressor, turbine, recuperator and heater are constructed, and the thermal efficiency of regenerative Brayton cycle and recompression Brayton cycle are calculated and analyzed. The results reveal that the efficiency of the recompression cycle is higher than that of the simple regenerative cycle. The effects of inlet temperature, inlet pressure of the main compressor and inlet temperature, inlet pressure of the turbine on the thermodynamic performance of the recompression cycle are studied, and the influencing mechanism is explained. The results show that the cycle efficiency decreases with the increase of the inlet temperature of the main compressor; there exists an optimum inlet pressure in the main compressor to maximize the cycle efficiency; and the cycle efficiency of the system increases with the increase of the inlet temperature and pressure of the turbine. When the inlet temperature of the turbine exceeds 600 ?, the thermal efficiency of the cycle can reach more than 50%.
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Wasik, Michał, Marcin A. Bugaj, Tomasz S. Wiśniewski, Maciej Klein, Patryk Chaja, and Sebastian Bykuć. "Mathematical model of flat plate solar thermal collector and its validation." E3S Web of Conferences 70 (2018): 01019. http://dx.doi.org/10.1051/e3sconf/20187001019.
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In order to predict solar thermal collector’s performance and optimization of control algorithms, proper mathematical models are necessary. Computer calculation technique provides tools for determination of modern materials impact on improvement of heat transfer inside the collector and minimization of heat loss. Such analysis is impossible by using standard technical datasheet provided by producer or by using empirical formulas. In the paper the authors present a mathematical model of a flat plate solar thermal collector based on the Hottel-Whiller-Bliss equation and criterial formula. The iterative algorithm solved steady state heat transfer equations for a glazed and an unglazed collector. The validation experiment was conducted under class AAA sun simulator for different inlet temperature and solar irradiation values. The unglazed PV/T and glazed solar thermal collectors were tested. For PV/T the relative difference, between measured and computed outlet temperatures, was below 5% and the highest value was reached for the lowest inlet temperature. The validation study showed that the experimental results reached good agreement with simulation predictions. Presented computation algorithm enables to predict influence of geometry changes on collector performance. The model could be used for optimization of the construction without using CFD methods, which need large computation resources.
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Hyndman, Lauren, Sean McKee, Nigel J. Mottram, Bhumika Singh, Steven D. Webb, and Sean McGinty. "Mathematical modelling of fluid flow and solute transport to define operating parameters for in vitro perfusion cell culture systems." Interface Focus 10, no. 2 (February 14, 2020): 20190045. http://dx.doi.org/10.1098/rsfs.2019.0045.
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In recent years, there has been a move away from the use of static in vitro two-dimensional cell culture models for testing the chemical safety and efficacy of drugs. Such models are increasingly being replaced by more physiologically relevant cell culture systems featuring dynamic flow and/or three-dimensional structures of cells. While it is acknowledged that such systems provide a more realistic environment within which to test drugs, progress is being hindered by a lack of understanding of the physical and chemical environment that the cells are exposed to. Mathematical and computational modelling may be exploited in this regard to unravel the dependency of the cell response on spatio-temporal differences in chemical and mechanical cues, thereby assisting with the understanding and design of these systems. In this paper, we present a mathematical modelling framework that characterizes the fluid flow and solute transport in perfusion bioreactors featuring an inlet and an outlet. To demonstrate the utility of our model, we simulated the fluid dynamics and solute concentration profiles for a variety of different flow rates, inlet solute concentrations and cell types within a specific commercial bioreactor chamber. Our subsequent analysis has elucidated the basic relationship between inlet flow rate and cell surface flow speed, shear stress and solute concentrations, allowing us to derive simple but useful relationships that enable prediction of the behaviour of the system under a variety of experimental conditions, prior to experimentation. We describe how the model may used by experimentalists to define operating parameters for their particular perfusion cell culture systems and highlight some operating conditions that should be avoided. Finally, we critically comment on the limitations of mathematical and computational modelling in this field, and the challenges associated with the adoption of such methods.
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Attia, Mohammed El Hadi. "Effect of the Preheating Inlet Air on the G222 Fuel Combustion." International Journal of Energetica 3, no. 2 (January 2, 2019): 29. http://dx.doi.org/10.47238/ijeca.v3i2.75.
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In this paper, a numerical simulation is developed to study the preheating effect of the air in a three-dimensional cylindrical combustion chamber using the FLUENT-CFD code. Particularly, we are interested on the calculation of the characteristic parameters such as the axial velocity, the temperature and the mass fraction of carbon monoxide. This study consists of a special treatment of mathematical models. The considered approaches resolve the governing equations of system. The main objective of this work is to study the behavior of the parameters considered previously during the variation of the air inlet temperature. The obtained results show that the variation of the inlet temperature presents a direct effect on the considered parameters.
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Левчук, Ігор Леонідович, Олег Петрович Мисов, Ксенія Олексіївна Фесенко, and Антон Романович Шейкус. "МОДЕЛЮВАННЯ ХІМІКО-ТЕХНОЛОГІЧНИХ ПРОЦЕСІВ У SCADA ЗА ДОПОМОГОЮ ТЕХНОЛОГІЇ OPEN PLATFORM COMMUNICATIONS." RADIOELECTRONIC AND COMPUTER SYSTEMS, no. 2 (April 26, 2020): 59–66. http://dx.doi.org/10.32620/reks.2020.2.05.
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The subject of study in the article are methods for integrating mathematical models of chemical-technological processes implemented in universal modeling programs into modern SCADA systems for developing and improving methods for controlling these processes. The goal is to develop a control system for the synthesis of acetylene in a kinetic reactor, based on a computer model created in universal modeling programs and integrated into SCADA using open platform communications (OPC) technology. Tasks: to create a mathematical model of the process of synthesis of acetylene based on the selected universal modeling program; to develop a way to integrate the resulting model into modern SCADA using OPC technology; to develop in SCADA a control system for the process of synthesis of acetylene according to a mathematical model as part of a functional human-machine interface and control subsystem algorithms; get transient graphs and prove the efficiency of the control system. Conduct a process study using a mathematical model. The methods used are computer simulation of technological processes; OPC technology; SCADA based management. The following results are obtained. A control system for the acetylene synthesis process based on SCADA Trace-Mode and a mathematical model implemented in the ChemCAD package has been developed, while the model - control system information exchange is implemented based on OPC technology. Checked and proved the efficiency of the resulting control system. A mathematical study of the process was carried out, an experimental dependence of the yield of the final product, acetylene, on the temperature, and consumption of raw materials at the inlet of the reactor was established. Conclusions. The novelty of the results is as follows. A new method is proposed for integrating mathematical models implemented in the ChemCAD modeling package into modern SCADA, based on OPC technology. A study of the process of acetylene synthesis by a mathematical model was carried out, experimental dependences of the acetylene yield on temperature and ethylene consumption at the inlet of the synthesis reactor were obtained. An analysis of the obtained experimental dependences showed the need to use cascade control algorithms to increase the efficiency of controlling the process of acetylene synthesis in a kinetic reactor.
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Salsabilah, Naqiyyah, Marwa Efira Karuniahaj, Duhaul Biqal Kautsar, Ni Made Intan Putri Suari, Heru Setyawan, Tantular Nurtono, and Widiyastuti. "Simulation of Microencapsulation Avocado Seeds Oil by Spray Drying." IOP Conference Series: Earth and Environmental Science 830, no. 1 (September 1, 2021): 012061. http://dx.doi.org/10.1088/1755-1315/830/1/012061.
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Abstract Drying air inlet temperature is one of the critical variables in the microencapsulation process by spray drying. However, when spray drying is carried out at inappropriate drying air inlet temperature, it can impact the particle produced. This study presents a simulation of spray drying from a mathematical model was developed to determine the effect of drying air inlet temperature on moisture content, particle diameter, particle density, and drying air outlet temperature in the microencapsulation process of avocado seeds oil as core materials and gum arabic as wall materials. For this aim, the mathematical model was developed then simulated using a matrix laboratory (Matlab) computer program with Euler numerical method for drying air inlet temperatures of 160, 180, and 200 °C. The selected model was validated with Cotabarren’s experimental results indicating the model was acceptable. The particles’ moisture contents predicted from simulation results are 1.170, 1.049, and 0.933 kg water/kg solid for 160, 180, and 200 °C, respectively. On the other hand, the predicted particle diameters are 29.73, 29.49, and 29.23 urn for 160, 180, and 200 °C, respectively. The predicted particle densities are 1215.72, 1225.21, and 1233.25 kg/m3 for 160, 180, and 200 °C, respectively. The prediction of drying air outlet temperatures was 39.76, 41.94, and 43.89 °C for inlet air temperatures of 160, 180, and 200 °C, respectively. The proposed models’ simulation results show that the higher temperatures caused lower particle moisture content, smaller particle diameter, and higher particle density. Also, the outlet drying air temperatures were always the same as the outlet particle temperatures.
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Salsabilah, Naqiyyah, Marwa Efira Karuniahaj, Duhaul Biqal Kautsar, Ni Made Intan Putri Suari, Heru Setyawan, Tantular Nurtono, and Widiyastuti. "Simulation of Microencapsulation Avocado Seeds Oil by Spray Drying." IOP Conference Series: Earth and Environmental Science 830, no. 1 (September 1, 2021): 012061. http://dx.doi.org/10.1088/1755-1315/830/1/012061.
Full textAbstract:
Abstract Drying air inlet temperature is one of the critical variables in the microencapsulation process by spray drying. However, when spray drying is carried out at inappropriate drying air inlet temperature, it can impact the particle produced. This study presents a simulation of spray drying from a mathematical model was developed to determine the effect of drying air inlet temperature on moisture content, particle diameter, particle density, and drying air outlet temperature in the microencapsulation process of avocado seeds oil as core materials and gum arabic as wall materials. For this aim, the mathematical model was developed then simulated using a matrix laboratory (Matlab) computer program with Euler numerical method for drying air inlet temperatures of 160, 180, and 200 °C. The selected model was validated with Cotabarren’s experimental results indicating the model was acceptable. The particles’ moisture contents predicted from simulation results are 1.170, 1.049, and 0.933 kg water/kg solid for 160, 180, and 200 °C, respectively. On the other hand, the predicted particle diameters are 29.73, 29.49, and 29.23 urn for 160, 180, and 200 °C, respectively. The predicted particle densities are 1215.72, 1225.21, and 1233.25 kg/m3 for 160, 180, and 200 °C, respectively. The prediction of drying air outlet temperatures was 39.76, 41.94, and 43.89 °C for inlet air temperatures of 160, 180, and 200 °C, respectively. The proposed models’ simulation results show that the higher temperatures caused lower particle moisture content, smaller particle diameter, and higher particle density. Also, the outlet drying air temperatures were always the same as the outlet particle temperatures.
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Yates, Martin K. "The calculation of gear pump porting areas by mathematical means." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 1 (April 24, 2014): 180–88. http://dx.doi.org/10.1177/0954406214531945.
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Twin pinion gear pumps are used widely in industrial hydraulics and as fuel-delivery pumps for aero engines. The kinematics of the pumping action leads to high-flow rates into and out of the meshing gears, and at the high speeds used with aerospace fuel pumps cavitation can occur. One-dimensional ‘lumped parameter’ models are often used to analyse this type of pump. These methods rely on an accurate description of the volume trapped by the meshing teeth and the flow areas during the meshing cycle. Typically, multiple computer-aided design models have to be created to calculate these values during the meshing cycle. This paper presents a mathematical method for calculating these parameters based on a parametric definition of the gear and inlet and outlet porting. Green's theorem is used to allow line integrals around the periphery of the tooth spaces to be used to calculate the volumes and flow areas. Winding numbers are used to calculate the inflow and outflow areas that are formed by the intersection of the trapped volume and the side area porting. The method is validated against computer-aided design model data. This method is well suited for incorporation in an optimisation algorithm since the geometry is defined parametrically.
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BARTON, N. G. "AN EVAPORATION HEAT ENGINE AND CONDENSATION HEAT PUMP." ANZIAM Journal 49, no. 4 (April 2008): 503–24. http://dx.doi.org/10.1017/s1446181108000035.
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AbstractThis paper presents a thermodynamic model for a heat engine based on evaporative cooling of unsaturated air at reduced pressure. Also analysed is a related heat pump based on condensation of water vapour in moist air at reduced pressure. These devices operate as two-stroke reciprocating engines, which are their simplest possible embodiments. The mathematical models for the two devices are based on conservation of mass for both air and water vapour, ideal gas laws, constant specific heats, and, as appropriate, either constant entropy processes or cooling/heating by evaporation/condensation. Both models take the form of coupled algebraic systems in six variables, which require numerical solution for certain stages of the cycle. The specific work output of the heat engine increases as the inlet air becomes hotter and as the expansion ratio of the engine increases. The engine provides evaporative cooling of air from inlet to outlet. The heat pump has a good coefficient of performance, which decreases as the expansion ratio increases. The heat pump also has the effect of drying the air from inlet to outlet, producing distilled water as a by-product.
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Aseibichin Cyrus, Peter Meshack Ene, and Olalekan Michael Adeloye. "Steady state modeling of steam condensate cooler." GSC Advanced Engineering and Technology 1, no. 2 (June 30, 2021): 001–6. http://dx.doi.org/10.30574/gscaet.2021.1.2.0031.
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Mathematical models for steam condensate cooler were developed. The models were deduced by applying the principle of conservation of energy and yielded an ordinary differential equation, which were solved by using MatLab ODE45 solver and validated using industrial data of a fertilizer company. The result gives minimum percentage absolute error or deviation between model predictions and industrial plant of 0.09% and 0.10% respectively for hot and cold fluid outlet temperature. These shows that the developed model predicted the fluid outlet temperature of the steam condensate cooler closely and the models were used to study the effects of process parameters such as fluid inlet flow rate and heat transfer coefficient on the performance of the steam condensate cooler.
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Tang, Pan, Hong Li, Zakaria Issaka, and Chao Chen. "Methodology to Investigate the Hydraulic Characteristics of a Water-Powered Piston-Type Proportional Injector Used for Agricultural Chemigation." Applied Engineering in Agriculture 34, no. 3 (2018): 545–53. http://dx.doi.org/10.13031/aea.12449.
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Abstract. The proportional injector is commonly used in agricultural chemigation due to its relatively high injection ratio. A major challenge with the proportional injector is related to its dependence on differential pressure, which is significantly influenced by changes in the viscosity, and setting injection ratio. A series of experiments were conducted to investigate the influence of differential pressures, solution viscosities, and setting injection ratios on the inlet and injection flow rates of a D25RE2 proportional injector. A mathematical model was developed to represent the hydraulic performance of this proportional injector. Finally, the mathematical model was verified using four different kinds of chemicals (humic acid, urea ammonium nitrate 32% N, fosthiazate, and colza oil). The inlet flow rate increased significantly with increasing differential pressure and decreased with increasing setting injection ratio. Results showed that the highest operating differential pressure should not be greater than 0.15 MPa for the D25RE2 proportional injector. The inlet flow rate gradually decreased with increasing viscosity, and a quadratic function relationship was derived between the inlet flow rate and the viscosity. The injection flow rate decreased with increasing viscosity. However, the viscosity had a slight influence on the injection flow rate when it was lower than 20 mPa·s. Mathematical models for calculating the inlet and injection flow rates with the influence of viscosity were developed, respectively. The coefficient of determination and the root mean square error (RMSE) for inlet flow rate calculation model were 0.8316 and 143.36 kg h-1, respectively. The coefficient of determination and the RMSE for the injection flow rate calculation model were 0.9706 and 0.9520 kg h-1, respectively. The calculating formula of inlet flow rate had a satisfactory accuracy under low differential pressure and high setting injection ratio. The calculating formula of the injection flow rate had a good accuracy, which is useful for calculating the injection flow rate when injected with different kinds of solutions. The average deviations between calculated and experimental injection flow rates with injection ratios of 0.2%, 1.2%, and 2% were obtained as 4.96%, 4.66%, and 4.1% respectively, which indicated that the average deviations decreased with increasing setting injection ratio. Results from this study are useful for both designers and users to effectively manage agricultural chemigation system with the proportional injector. Keywords: Agriculture, Chemigation, Proportional injector, Hydraulic performance.
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Maleki, Ghazvini, Ahmadi, Maddah, and Shamshirband. "Moisture Estimation in Cabinet Dryers with Thin-Layer Relationships Using a Genetic Algorithm and Neural Network." Mathematics 7, no. 11 (November 3, 2019): 1042. http://dx.doi.org/10.3390/math7111042.
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Nowadays, industrial dryers are used instead of traditional methods for drying. When designing dryers suitable for controlling the process of drying and reaching a high-quality product, it is necessary to predict the gradual moisture loss during drying. Few studies have been conducted to compare thin-layer models and artificial neural network models on the kinetics of pistachio drying in a cabinet dryer. For this purpose, ten mathematical-experimental models with a neural network model based on the kinetic data of pistachio drying were studied. The data obtained was from a cabinet dryer evaluated at four temperatures of inlet air and different air velocities. The pistachio seeds were placed in a thin layer on an aluminum sheet on a drying tray and weighed by a scale attached to the computer at different times. In the neural network, data was divided into three parts: Educational (60%), validation (20%) and testing (20%). Finally, the best mathematical-experimental model using a genetic algorithm and the best neural network structure for predicting instantaneous moisture were selected based on the least squared error and the highest correlation coefficient.
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Gao, De Dong, and Shan Wang. "Mathematical Model for Temperature Distributions of Work Roll in Aluminum Strip Cold Rolling." Advanced Materials Research 150-151 (October 2010): 97–101. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.97.
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The temperature distribution of the work roll affects the shape and size of final product in aluminum strip cold rolling process. The segmental model is presented to explore the boundaries of the roll. The surface of the work roll is divided into 5 different regions including the outlet roll-strip contact region, the inlet roll-strip contact (bite) region, the roll-spray region, the roll-air region and the roll-roll contact region. Based on the analysis of the roll pressure, the mathematical models of the plastic doformation work and friction heat are proposed to calculate the temperature variation in bite region. The boundaries, including heat convection with lubricant/air and heat conduction with the backup roll, are considered to model the work roll’s temperature distribution.
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Liu, Zichao, Wei Pan, Changhou Lu, and Yongtao Zhang. "Numerical analysis on the static performance of a new piezoelectric membrane restrictor." Industrial Lubrication and Tribology 68, no. 5 (August 8, 2016): 521–29. http://dx.doi.org/10.1108/ilt-07-2015-0098.
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Purpose This paper aims to establish an accurate mathematical model of a piezoelectric membrane restrictor that can be applied to control the shaft’s centerline orbit. Design/methodology/approach The methodology uses three coupled equations to establish a mathematical model of the piezoelectric membrane restrictor – Reynolds equation, the membrane deformation equation and the flow rate equation. A data identification method is used to propose the flow rate formulas for the piezoelectric membrane restrictor. Findings It has been found that the structural parameters, the membrane center deformation and the inlet and outlet pressures of the piezoelectric membrane restrictor have an effect on the static performance of the restrictor. The identified flow rate result of the piezoelectric membrane restrictor is consistent with the models. Originality/value The paper provides an accurate mathematical model of the piezoelectric membrane restrictor which can also be applied to other membrane restrictors.
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Wang, Bao Ming, Xia Lun Yun, Xing Yao Liao, and Xue Song Mei. "Analysis of Thermal Effect on Elastohydrodynamic Lubrication in Angular Contact Ball Bearing." Applied Mechanics and Materials 741 (March 2015): 443–48. http://dx.doi.org/10.4028/www.scientific.net/amm.741.443.
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Based on the theory of point contact thermal elastohydrodynamic lubrication (EHL),the mathematical models for the thermal EHL of high-speed angular contact ball bearing are established. Multi-grid method and multigrid integration method are respectively used to calculate out the film pressure and film thickness respectively,and the column-by-column scanning method is used to calculate temperature rise of isothermal EHL and thermal EHL. The calculation results show that, under the pure rolling condition, temperature rise of oil film temperature is mainly caused by the compression work and shear heat at inlet and the heat in contact zone mainly comes from the inlet and the heat conduction around; the temperature rise results in oil viscosity lower and the lubricating film thinner ,in this way it reduces the lubrication performance in contact pair.
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Rakhmanov, Sh R., and K. N. Turaev. "Implementation of the developed models and algorithms in problems of control of the process of culturing of chlorella." IOP Conference Series: Earth and Environmental Science 1043, no. 1 (June 1, 2022): 012009. http://dx.doi.org/10.1088/1755-1315/1043/1/012009.
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Abstract The article considers the implementation of mathematical models and algorithms for hanging the efficiency of managing the chlorella cultivation process on the basis of the modeling algorithm of state parameters. One of the necessary conditions for the optimal conduct of the process of cultivating microorganisms is automatic control of the quality and composition of nutrients at the inlet, as well as control of the output indicators of the process. Based on the results of theoretical and experimental studies performed using modern methods and tools, as well as the positive results of industrial tests, it is possible to increase the efficiency of controlling the chlorella cultivation process on the basis of a modeling algorithm for state parameters.
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Drozdov, A. A., Yu B. Galerkin, O. A. Solovyeva, K. V. Soldatova, and A. A. Ucehovscy. "Mathematical model of the 9th version Universal modeling method: features and results of identification." Omsk Scientific Bulletin. Series Aviation-Rocket and Power Engineering 4, no. 4 (2020): 28–40. http://dx.doi.org/10.25206/2588-0373-2020-4-4-28-40.
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The Universal modeling method is a complex of computer programs for calculating the characteristics and optimal design of centrifugal compressors based on mathematical models of efficiency and head. Practical experience allows improving the mathematical models that underlie the Method. Determining the non-incidence inlet in a blade cascade is an important part of calculating the compressor gasdynamic characteristics. In the 8th version of the Universal modeling method, a formula is used to calculate the direction of the critical stream line, containing an empirical coefficient X. The practice of application has shown that the value of the empirical coefficient changes the amount of losses in the impeller in off-design flow rates. A new scheme for modeling velocity diagrams is proposed. It is made for the stage operation mode corresponding to the zero incidence angle. The successful use of the model for the impeller made it possible to extend it to the vane diffuser and return channel. Several other improvements are made too. A new mathematical model is developed for calculating the flow parameters in the exit nozzles of centrifugal compressor stage. The mathematical model for calculating the flow parameters in the vaneless diffusers is modernized. The applicability boundary of the new model is expanded to a range of diffusers of low consumption stages with a relative width of up to 0,006. The resulting mathematical model is identified by the test results of two family model stages and plant tests of industrial compressors
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Pater, Sebastian, and Włodzimierz Ciesielczyk. "Mathematical modelling of thermal and flow processes in vertical ground heat exchangers." Chemical and Process Engineering 38, no. 4 (December 1, 2017): 523–33. http://dx.doi.org/10.1515/cpe-2017-0041.
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Abstract The main task of mathematical modelling of thermal and flow processes in vertical ground heat exchanger (BHE-Borehole Heat Exchanger) is to determine the unit of borehole depth heat flux obtainable or transferred during the operation of the installation. This assignment is indirectly associated with finding the circulating fluid temperature flowing out from the U-tube at a given inlet temperature of fluid in respect to other operational parameters of the installation. The paper presents a model of thermal and flow processes in BHE consisting of two analytical models separately-handling processes occurring inside and outside of borehole. A quasi-three-dimensional model formulated by Zeng was used for modelling processes taking place inside the borehole and allowing to determine the temperature of the fluid in the U-tube along the axis of BHE. For modelling processes occurring outside the borehole a model that uses the theory of linear heat source was selected. The coupling parameters for the models are the temperature of the sealing material on the outer wall of the borehole and the average heat flow rate in BHE. Experimental verification of the proposed model was shown in relation to BHE cooperating with a heat pump in real conditions.
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Li, Da Ying, and Gui Yun Jiang. "Study on the Oil Film Static Performance of Sliding Bearings with Different Throttling Methods." Applied Mechanics and Materials 155-156 (February 2012): 519–25. http://dx.doi.org/10.4028/www.scientific.net/amm.155-156.519.
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The restrictors of fluid lubricated sliding bearings play vital role in oil film rigidity and carrying capacity of bearings. The mathematical models for solution of the oil film static performance of the bearings with four different restrictors were presented and the numerical solution methods were analyzed. The solutions for oil film static characteristics in many aspects such as discretization of Reynolds equation, building clearance function, determinating boundary conditions, constructing continuity equation, deducing the models of oil inlet flow, solving the carrying capacity were conducted. The computational results show that the bearings with capillary or orifice restrictor have lower carrying capacity and oil film rigidity than those with sliding valve feedback or film feedback restrictors.
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Noori, Abdul Wasim, Mohammad Jafar Royen, and Juma Haydary. "Thin-layer mathematical modeling of apple slices drying, using open sun and cabinet solar drying methods." International Journal of Innovative Research and Scientific Studies 4, no. 2 (March 30, 2021): 43–52. http://dx.doi.org/10.53894/ijirss.v4i2.55.
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This paper aims to investigate the effect of climate conditions such as ambient temperature, humidity, pressure, sun radiation and pollution on sliced apples quality and drying time which are dried in an indirect forced cabinet solar drying (IFCSD) and open sun drying (OSD) systems. Both experiments were implemented at same place (Kabul, Afghanistan) and time. The IFCSD yield for saving time is 42.8 % which is more effective than drying in the OSD system. Simultaneously with the decreasing of sliced apple weight from 512.9 g down to 73.9 g, the water activity decreased from 0.955 down to 0.355 in the IFCSD system. For OSD system, the sample weight decreased from 512.6 g down to 78.4 g and its water activity from 0.955 down to 0.411. On the experiment day the average sun radiation was 571 w/m2 . The pressure drop between inlet and outlet of the dryer was 0.1 kPa. Different thin-layer mathematical models were investigated to identify the best model fitting the experimental data. The mathematical models’ performances were investigated by comparing the coefficient of determination (R 2 ), reduced chi-square (X2 ) and root mean square error (RMSE) coefficients. From all 11 applied thin-layer drying models the Page, Approximation diffusion, Verma et al and Midilli and Kacuk models are more fitted to our data.
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Zhang, Qi, Ruo Fei Liu, Hao Liu, and Ru Wu Wang. "Numerical Simulation and Performance Study of Adjustable Steam Ejector Using CFD." Advanced Materials Research 562-564 (August 2012): 1150–54. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.1150.
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A djustable ejector flow control can be achieved to export in a stable area, thus reducing the jet inlet parameters on the export parameters as well as the impact of the entire system, widening of the jet's effective operating range. In this paper, the establishment of an effective mathematical models and computational methods to commercial CFD software FLUENT 6.3 as a platform for the adjustable jet to simulate the internal flow process and performance research, exploration and analysis of the main needle is moved (ie the nozzle throat orifice area change) operating parameters (including the working fluid inlet pressure, inlet pressure and the lead body jet mixing fluid outlet pressure) on the adjustable jet performance of the law, for the adjustable jet to provide important parameters to optimize the design. Studies show that: ① the needle device with adjustable spray jet in a non-rated conditions, can increase the coefficient of the jet injector; ② other parameters remain the same circumstances, the adjustable jet to varying degrees, increased work pressure , suction pressure, discharge pressure and outlet flow range.
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Manjunatha, S. S., and P. S. Raju. "Mathematical Modelling the Drying Kinetics of Beetroot Strips during Convective Drying at Different Temperatures." Defence Life Science Journal 4, no. 2 (April 11, 2019): 140–49. http://dx.doi.org/10.14429/dlsj.4.12176.
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The thin layer drying of beetroot strips was evaluated at drying temperatures from 60 °C to 90 °C using convective dryer at inlet air velocity of 1.0 m/s. The different drying models were tested to evaluate the drying characteristics of beetroot strips. The investigations showed that Page’s and modified Page’s equations were satisfactorily describing the drying behaviour of beetroot strips during convective drying with appreciable high correlation coefficient (0.9971<r<0.9990) with low error values. The effective moisture diffusivity was increased from 3.563 x 10-10 m2/s to 8.038 x 10-10 m2/s with increase in drying temperature. The temperature dependency of effective moisture diffusivity was described by Arrhenius equation and activation energy for moisture diffusivity was 30.08 KJ/mol. The drying kinetic coefficients were significantly (p<0.05) affected by drying air temperature. The exponents of models were decreased linearly with drying air temperature during drying of beetroot strips. The equilibrium moisture content was markedly affected by drying air temperature and it decreased linearly with drying air temperature. The results were very useful in standardisation and optimisation of drying process of beetroot strips in large scale commercial production.
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Hung, Nguyen Ba, and Ocktaeck Lim. "Development of a High-Performance Electric Pressure Regulator Applied for Compressed-Natural-Gas-Fueled Vehicles." Sustainability 12, no. 19 (September 25, 2020): 7938. http://dx.doi.org/10.3390/su12197938.
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A model-based study is carried out based on a combination of mathematical and Maxwell models to develop a high-performance electric pressure regulator utilized for compressed-natural-gas-fueled vehicles. To reduce computational cost, a symmetric two-direction model of the electric pressure regulator is established in Maxwell software, in which its material properties and dimension parameters are obtained on the base of specifications of a real electric pressure regulator. The output of simulating in Maxwell is the electromagnetic force, which is significantly improved when changing core shape in the various dimensions ∆1, ∆2, and ∆3. The optimal electromagnetic force is utilized for the mathematical models as an input variable to simulate the operational characteristics of the electric pressure regulator such as displacement and response time of plunger. The operational characteristics of the electric pressure regulator are examined under the influences of key parameters, including inlet gas pressure, diameter of orifice, and spring stiffness. By optimizing these key parameters, the simulated results in this study show that an electric pressure regulator with high performance can be obtained.
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Liffman, Kurt, Ilija D. Šutalo, Anh Bui, Michael M. D. Lawrence-Brown, and James B. Semmens. "Experimental Measurement and Mathematical Modeling of Pulsatile Forces on a Symmetric, Bifurcated Endoluminal Stent Graft Model." Vascular 17, no. 4 (August 1, 2009): 201–9. http://dx.doi.org/10.2310/6670.2009.00036.
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The objective of this study was to measure the pulsatile forces acting on a symmetric, bifurcated endoluminal stent graft to validate a computational fluid dynamics (CFD) and analytic model so that they can be used for various graft dimensions. We used a load cell to measure the force owing to the movement of an acrylic model of a bifurcated stent graft under pulsatile flow. This was then simulated with a CFD and analytic model. The main features of the experimental pulsatile force data and the CFD results were consistent. The results showed that the total force was proportional to the inlet pressure cycle. The force rose from 3.32 N at 130 mm Hg systolic to 17.5 N at 250 mm Hg systolic pressure. For the more variable regions of the flow, the experimentally measured forces lagged the computational and analytic results. The CFD and analytic models provide approximate descriptions for the forces acting on a bifurcated stent graft subjected to pulsatile flow. Such models should be of assistance to designers of endoluminal stent grafts.
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Radkevich, E. V., N. N. Yakovlev, and O. A. Vasil’eva. "QUESTIONS AND PROBLEMS OF MATHEMATICAL MODELING QUA NONEQUILIBRIUM OF COMBUSTION PROCESSES." EURASIAN JOURNAL OF MATHEMATICAL AND COMPUTER APPLICATIONS 8, no. 4 (2020): 31–38. http://dx.doi.org/10.32523/2306-6172-2020-8-4-31-68.
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On the basis of thermodynamic analysis, new mathematical models of the combus- tion process (thermal theory) and vibrational combustion are constructed. A global inhomo- geneity of the system can be described as an inhomogeneous distribution of the enthalpy over a two-component mixture. In this case, for the combustion process in the phase space of the variables (%, P, T, n, S, E), an increase in the enthalpy is not a total differential. An increase in the enthalpy is a total differential on the local equilibrium manifold (a laminar combustion process). These two assertions, which allow one to single out in the phase space the corre- sponding adiabatic of the combustion process (the Hugoniot adiabatic) and the equation for the entropy, close the classical mathematical model of the combustion process. The above numerical experiments show that two regimes of the combustion process (deflagration and detonation) depend on the structure of the standard chemical potential Moreover, a control of the passive component velocity at the inlet results in (depending on the structure of the standard chemical potential) high-frequency oscillations, which are responsible for a blow-up.
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Gupta, B. B., M. Y. Jaffrin, and L. H. Ding. "Modelling of Plasma-Separation through Microporous Membranes." International Journal of Artificial Organs 12, no. 1 (January 1989): 51–58. http://dx.doi.org/10.1177/039139888901200109.
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Available mathematical models of ultrafiltration have been used to predict changes in maximum plasma filtration rate with wall shear rate for given filters and blood properties. We have done many plasmapheresis experiments in vitro, using hollow-fiber filters (500–1000 cm2) and fresh bovine blood collected on ACD or heparin. The comparison between predicted and experimentally obtained filtration rates was good for models based on the concentration polarization theory and lift velocity theory. In other experiments with pulsatile inlet flow we found that plasma filtration rate increased by 20 to 50% compared to nonpulsatile conditions. These results are in good agreement with the modified model of ultrafiltration incorporating pulsating flow. This paper presents relationships between plasma filtration velocity (steady and pulsating flow) and hemolysis limit as a function of wall shear rate and filter size.
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Yi, Xian Zhong, Song Lin Yi, Hui Shu, Yuan Qiang Ji, and Sheng Zong Jiang. "Flow-Field and Hydromechanics Analysis of High Pressure Water-Jet Single Nozzle in Radial Horizontal Drilling." Advanced Materials Research 952 (May 2014): 186–89. http://dx.doi.org/10.4028/www.scientific.net/amr.952.186.
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The technology of high pressure water jet in radial drilling has currently been used widely at home and abroad. A numerical simulation and analysis of the internal and external flow fields of jet nozzle will 1ay the foundation for the further study of high pressure water jet rock breaking. The physical and mathematical models of axial-symmetrical submerged jet rock breaking with single nozzle were established. And a numerical simulation of the internal and external flow fields of high pressure water jet nozzle in radial drilling was conducted with the Fluent software. The 1aws of the internal and external flow fields were analyzed in different jet distances and inlet flow rates.
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Diniz, Hélio A. G., Tiago F. Paulino, Juan J. G. Pabon, Antônio A. T. Maia, and Raphael N. Oliveira. "Dynamic Model of a Transcritical CO2 Heat Pump for Residential Water Heating." Sustainability 13, no. 6 (March 21, 2021): 3464. http://dx.doi.org/10.3390/su13063464.
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This paper presents a distributed mathematical model for a carbon dioxide direct expansion solar-assisted heat pump used to heat bath water. The main components are a gas cooler, a needle valve, an evaporator/collector, and a compressor. To develop the heat exchange models, mass, energy, and momentum balances were used. The model was validated for transient as well as steady state conditions using experimental data. A reasonably good agreement was observed between the predicted temperatures and experimental data. The simulations showed that the time step required to demonstrate the behavior of the heat pump in the transient regime is greater than the time step required for the steady state. The results obtained with the mathematical model revealed that a reduction in the water mass flow rate results in an increase in the water outlet temperature. In addition, when the carbon dioxide mass flow rate is reduced, the compressor inlet and outlet temperatures increase as well as the water outlet temperature.
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Uribe, Sebastián, Binbin Qi, Omar Farid, and Muthanna Al-Dahhan. "Mathematical Modeling and Pointwise Validation of a Spouted Bed Using an Enhanced Bed Elasticity Approach." Energies 13, no. 18 (September 11, 2020): 4738. http://dx.doi.org/10.3390/en13184738.
Full textAbstract:
With a Euler–Euler (E2P) approach, a mathematical model for predicting the pointwise hydrodynamic behavior of a spouted bed was implemented though computational fluid dynamics (CFD) techniques. The model considered a bed elasticity approach in order to reduce the number of required sub-models to provide closure for the solids stress strain-tensor. However, no modulus of elasticity sub-model for a bed elasticity approach has been developed for spouted beds, and thus, large deviations in the predictions are obtained with common sub-models reported in literature. To overcome such a limitation, a new modulus of elasticity based on a sensitivity analysis was developed and implemented on the E2P model. The model predictions were locally validated against experimental measurements obtained in previous studies. The experimental studies were conducted using our in-house developed advanced γ-ray computed tomography (CT) technique, which allows to obtain the cross-sectional time-averaged solids holdup distribution. When comparing the model predictions against the experimental measurements, a high predictive quality for the radial solids holdup distribution in the spout and annulus regions is observed. The model predicts most of the experimental measurements for different particle diameters, different static bed heights, and different inlet velocities with deviations under 15%, with average absolute relative errors (AARE) between 5.75% and 7.26%, and mean squared deviations (MSD) between 0.11% and 0.24%