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نتیجه جستجو - تولید آنتروپی

تعداد مقالات یافته شده: 6
ردیف عنوان نوع
1 Employing V-shaped ribs and nanofluid as two passive methods to improve second law characteristics of flow within a square channel: A two-phase approach
استفاده از دنده های V شکل و نانوسیال به عنوان دو روش غیرفعال برای بهبود ویژگی های قانون دوم جریان در یک کانال مربع: یک روش دو فاز-2020
This research attempts to investigate the effects of simultaneous utilization of V-shaped ribs and nanofluid as two heat transfer enhancement approaches inside a square channel on the second law at- tributes. For this purpose, the comprehensive entropy generation and exergy destruction analyses are car- ried out with the aid of the two-phase mixture technique for the copper–water nanofluid flow through the channel enhanced with the 45 °V-shaped ribs. Firstly, a comparison is made between attack angles of 45 °and 60 °, which unveils the superiority of 45 °because it shows lower entropy generation. The Cu nanoparticles are utilized as the main nanoparticles. Furthermore, the nanofluids containing the Ag nanoparticles are also simulated at two volume fractions of 0.01 and 0.03 to make comparison between different nanoparticle materials. The impacts of rib configuration including the rib pitch and its height are assessed using three rib pitches and three rib heights. The total entropy generation and total exergy destruction decrease as the volume fraction increases, such that an around 31.85% reduction occurs in the total entropy generation and total exergy destruction when the volume fraction increases by 0.03 for the case of rib height of 5 mm and rib pitch of 100 mm. Thereby, the second law efficiency rises by 15.64% in the same condition. Additionally, the installed 45 °V-shaped ribs remarkably contribute to the total irreversibility reduction by means of creating four recirculation flows and powerful swirl flows. The re- sults indicate that utilizing both larger rib height and smaller rib pitch (at the same time) exhibits lower exergy destruction and enhances the second law efficiency.
Keywords: Two-phase mixture model | second law efficiency | v-shaped rib | entropy generation | nanofluid | exergy destruction
مقاله انگلیسی
2 Thermodynamic second law analysis of magnetomicropolar fluid flow past nonlinear porous media with non-uniform heat source
تحلیل قانون دوم ترمودینامیکی جریان سیال مگنتومیکروپولار از رسانه متخلخل غیرخطی با عبور منبع حرارتی غیر یکنواخت -2020
This study analyzes the second law of thermodynamic for entropy generation in an irreversible hydromagneto-micropolar flow system with non-homogenous heat generation. The non-symmetric microstructure fluid flow past a stretching sheet with saturated porous nonlinear media under magnetic field influence. Ignoring the fluid particle deformation, the microstructure is assumed rigid with the viscous suspended medium. The reduced dimensionless nonlinear formulated model is computationally coded and solved to obtain solutions for the entropy volumetric production, Bejan number and heat transfer magneto-micropolar fluid. The parameter dependent solutions for the flow characteristics and irreversibility processes are plotted and discussed. It is revealed from the study that minimization of entropy generation in a magneto-micropolar flow system is possible by improving the thermodynamic equilibrium with low material variables, viscosity and hysteresis magnetic. Also, it is seen that the terms that encourage internal heat generation reduces the micropolar fluid viscosity in the system.
KEYWORDS : Micropolar | Non-Newtonian fluid | Entropy generation | Stretching sheet | Thermodynamic law
مقاله انگلیسی
3 CFD analysis of second law characteristics for flow of a hybrid biological nanofluid under rotary motion of a twisted tape: Exergy destruction and entropy generation analyses
تجزیه و تحلیل CFD از ویژگی های قانون دوم برای جریان یک نانوسیالات بیولوژیکی ترکیبی تحت حرکت چرخشی نوار پیچ خورده: تخریب اگزرژی و تجزیه و تحلیل نسل آنتروپی-2020
The main goal of the current study is to evaluate the effects of a hybrid heat transfer enhancement method, i.e. simultaneous deployment of active and passive techniques, with employing an ecofriendly-produced graphene nanoplatelets nanofluid from the viewpoint of the second law of thermodynamics. The numerical simulations are performed for the tubes enhanced with the innovative rotary twisted tape. Employing the rotary twisted tape intensifies the flow mixing, disrupts the thermal boundary layer, and reduces the temperature gradients dramatically. The total entropy generation and total exergy destruction of nanofluid extremely diminish by the rotational speed elevation. The maximum decrement in the total entropy generation is 87.38%, which occurs by elevating the rotational speed from 0 to 900 rpm. The concentration increase considerably contributes to the exergy destruction decrement besides total entropy generation reduction. The lower twisted ratio exhibits the smaller thermal irreversibility, and the best second law efficiency equals to 0.932.
Keywords: Exergy destruction | Rotational twisted tape | Graphene nanoplatelets nanofluid | Entropy generation | Ecofriendly nanofluid | Second law efficiency
مقاله انگلیسی
4 Numerical solution of MHD flow of power law fluid subject to convective boundary conditions and entropy generation
راه حل عددی جریان MHD موضوع مایعات قانون قدرت در معرض شرایط مرز همرفتی و تولید آنتروپی-2020
Background: The application of entropy optimization has consistently incorporated in traditional and in- dustrial fields. The system is permanently sustainable, usually a final ideal structure may not exist in general, as common evolution shows trends in a long time. The measurement of the entropy generation related to heat transport can be proportional to temperature difference. The minimization of entropy gen- eration through various parameters is our main purpose in this research article. Therefore, here we have discussed 2D flow of non-Newtonian liquid over a stretched surface with entropy optimization. Convec- tive boundary conditions of temperature are implemented in the current flow phenomenon. Furthermore, viscous dissipation has been taken into account. Method: The involved nonlinear differential system has been tackled through ND solve numerical tech- nique (Shooting method). Results: The key observations are summarized as follows: (i) Velocity grows for larger estimations of power law index of fluid. (ii) Temperature ˜ θ(ξ) increases for Ec . (iii) Surface drag enhances for higher values of Ha . (iv) The temperature gradient N u x R e −1 n +1 is inversely proportional to Ec and Ha . (v) Entropy N G ( ξ) is larger for higher Ec and Ha while the opposite impact is examined for M . (vi) Bejan number Be decreases with Pr and M , while it upsurges with Ha and Ec .
Keywords: Entropy generation | Power law fluid | Activation energy | Convective boundary conditions | Chemical reaction | Viscous dissipation
مقاله انگلیسی
5 Information criteria for quantifying loss of reversibility in parallelized KMC
معیارهای اطلاعات برای کمی سازی از دست دادن برگشت پذیری در KMC موازی-2017
Parallel Kinetic Monte Carlo (KMC) is a potent tool to simulate stochastic particle systems efficiently. However, despite literature on quantifying domain decomposition errors of the particle system for this class of algorithms in the short and in the long time regime, no study yet explores and quantifies the loss of time-reversibility in Parallel KMC. Inspired by concepts from non-equilibrium statistical mechanics, we propose the entropy production per unit time, or entropy production rate, given in terms of an observable and a corresponding estimator, as a metric that quantifies the loss of reversibility. Typically, this is a quantity that cannot be computed explicitly for Parallel KMC, which is why we develop a posteriori estimators that have good scaling properties with respect to the size of the system. Through these estimators, we can connect the different parameters of the scheme, such as the communication time step of the parallelization, the choice of the domain decomposition, and the computational schedule, with its performance in controlling the loss of reversibility. From this point of view, the entropy production rate can be seen both as an information criterion to compare the reversibility of different parallel schemes and as a tool to diagnose reversibility issues with a particular scheme. As a demonstration, we use Sandia Lab’s SPPARKS software to compare different parallelization schemes and different domain (lattice) decompositions.
Keywords: Parallel kinetic Monte Carlo | Operator splitting schemes | Long-time errors | Time-reversibility | Detailed balance | Entropy production | Information criteria
مقاله انگلیسی
6 همرفت ترکیبی MHD و تولید آنتروپی در یک میکروکانال سه بُعدی با استفاده از نانوسیال آب
سال انتشار: 2015 - تعداد صفحات فایل pdf انگلیسی: 13 - تعداد صفحات فایل doc فارسی: 35
در این مقاله، همرفت مخلوط و نیز قانون دوم تحلیل ترمودینامیک در یک میکروکانال سه بعدی پرشده با نانوسیال تحت یک میدان مغناطیسی به صورت عددی مورد بررسی قرار گرفت. میدان های دمایی، تغییرات سرعت افقی، مقاومت گرمایی، افت فشار، اعداد هارتمن و رینولدرز بررسی شدند. افزون بر این، حرارت، اصطکاک، و تولید آنتروپی مغناطیسی در کسرهای حجمی مختلف مطالعه شدند. تحلیل نتایج شبیه سازی های عددی نشان می دهد که با افزایش عدد هارتمن، حداکثر سرعت افقی در امتداد خط مرکز مقاومت حرارتی ورودی و خروجی در میکروکانال کاهش می یابد. از سوی دیگر، با افزایش قدرت میدان مغناطیسی اعمال شده، تولید آنتروپی حرارتی کاهش می یابد، در حالیکه آنتروپی های اصطکاکی و مغناطیسی افزایش می یابند. با اینحال، افزایش دو مورد آخر در مقایسه با تولید آنتروپی حرارتی، بسیار کم است. نسبت نواگ / (افت فشار) از 10 بزرگ تر است.در نتیجه، بهره ی حرارتی این میکروکانال تقریباً بیانگر افت کاهش فشار است.
کلمات کلیدی: همرفت ترکیبی | تولید آنتروپی | میکروکانال | نانوسیالات | میدان مغناطیسی
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بازدید امروز: 1808 :::::::: بازدید دیروز: 0 :::::::: بازدید کل: 1808 :::::::: افراد آنلاین: 41