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Conjugate natural convection flow in a thick walled semi-circular cavity containing molten core material has been analysed numerically. The lower plenum debris bed represents decay heating, heat conduction, and heat convection within the... more
Conjugate natural convection flow in a thick walled semi-circular cavity containing molten core material has been analysed numerically. The lower plenum debris bed represents decay heating, heat conduction, and heat convection within the debris. The internal heat generation resulting from the radioactive decay of fission products ensures that most of the pool remains molten and also causes natural convection in
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In the conventional ice accretion models, the thickness (Bg) and time (tg), at which the glaze ice appears for the first time, are predicted based on the thermodynamic calculations. Then, these values are taken as critical transient... more
In the conventional ice accretion models, the thickness (Bg) and time (tg), at which the glaze ice appears for the first time, are predicted based on the thermodynamic calculations. Then, these values are taken as critical transient criteria to apply either the rime ice or the glaze ice calculations at each time step. In the proposed ice accretion model presented in this study, the calculations of the ice accretion are initiated with the rime ice. If the results are plausible they are accepted, otherwise, the glaze ice calculation is applied. The strength of this approach is that it enables the course of numerical computations of the icing process to proceed in the same way as the real physics of the icing phenomenon. The results of the present study show that the proposed ice accretion approach for all rime, mixed, and glaze ice-regimes gives more accurate results than the conventional ice accretion models.
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Purpose of this study is to numerically investigate combustion within a porous channel, which has three layers with different pore densities. Non-premixed combustion inside the porous channel is modelled with thermal non-equilibrium... more
Purpose of this study is to numerically investigate combustion within a porous channel, which has three layers with different pore densities. Non-premixed combustion inside the porous channel is modelled with thermal non-equilibrium energy equations. Flow and chemistry are decoupled with tabulated chemistry using flamelets, thereby reducing the computational cost. GRI 3.0 mechanism is used to account for methane/air combustion. Simulations are performed for different pore densities at the third layer in 8-30 PPI range. Also, the effects of thermal power and excess-air-ratio (EAR) are investigated for the porous burner. Temperatures and species mass fraction distributions are obtained. Maximum temperature in the burner found to be similar for all cases since combustion occurs in stoichiometric conditions at the flame front as a result of the non-premixed combustion model. NOx and CO emissions values of all simulations are compared against international gas emission standards. This co...
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... numerically analysed the effect of conduction in one of the vertical walls on natural convection flow in ... analysis is to investigate the nature of the buoyant flow in a square enclosure when all ... Cavity is square and all the... more
... numerically analysed the effect of conduction in one of the vertical walls on natural convection flow in ... analysis is to investigate the nature of the buoyant flow in a square enclosure when all ... Cavity is square and all the walls are thick having constant outside temperature, ie, rigid ...
Research Interests: Engineering, Mechanical Engineering, Applied Mathematics, Materials Science, Mechanics, and 11 moreHeat and Mass Transfer, Pergamon, Mathematical Sciences, Natural Convection, Physical sciences, THERMAL DIFFUSIVITY, Thermal Sciences, Enclosure, Interdisciplinary Engineering, Nusselt Number, and Conjugate
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The steady entropy generation due to laminar free convection from a trapezoidal cavity filled with a porous medium has been studied theoretically. The governing two-dimensional equations have been solved numerically and the isotherms,... more
The steady entropy generation due to laminar free convection from a trapezoidal cavity filled with a porous medium has been studied theoretically. The governing two-dimensional equations have been solved numerically and the isotherms, streamlines, entropy generation number and Bejan number are presented graphically for different values of the Rayleigh number and tilt angle.
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Calculated free convection flows and heat transfer are presented for concentric spherical annular sectors, filled with a porous medium. Two isothermal walls and an adiabatic radial wall at the sector angle define the sectors. The... more
Calculated free convection flows and heat transfer are presented for concentric spherical annular sectors, filled with a porous medium. Two isothermal walls and an adiabatic radial wall at the sector angle define the sectors. The governing equations (in the stream function and temperature formulation) are solved numerically using ADI (alternative direction implicit) finite-difference method. Over the range of geometric parameters
Research Interests: Chemical Engineering, Civil Engineering, Applied Mathematics, Materials Science, Mechanics, and 10 moreHeat Transfer, Transport Phenomena in Porous Media, Natural Convection, Free Convection, Finite Difference Method, Porous Medium, Numerical Solution, Stream Function, Aspect Ratio, and Rayleigh Number
... Heat Transfer A 37, 493510. Ratish Kumar, BV, Singh, P. and Murthy, PVSN: 1997, Effect of surface undulations on natural convection in a porous square cavity, ASME J. Heat Transfer 119, 848851. Ratish Kumar, BV, Murthy ...
Research Interests: Chemical Engineering, Civil Engineering, Applied Mathematics, Physics, Materials Science, and 15 moreMechanics, Convection, Heat Transfer, Finite element method, FEM, Finite Element Analysis, Models, Porous Media, Natural Convection, Enclosure, Nusselt Number, Differential equation, Porous Medium, Aspect Ratio, and Rayleigh Number
ABSTRACT A numerical investigation of steady free convection inside a cavity made of two horizontal straight walls and two vertical wavy walls filled with a heat-generating porous medium is carried out. Wavy walls are assumed to follow... more
ABSTRACT A numerical investigation of steady free convection inside a cavity made of two horizontal straight walls and two vertical wavy walls filled with a heat-generating porous medium is carried out. Wavy walls are assumed to follow the profile of a cosine curve. Horizontal straight walls are kept adiabatic, while the bent walls are isothermal and kept at the same temperature. The governing Darcy and energy equations were discretized using the Galerkin finite element method. The results provide detailed information on the influences of the governing parameters, which describe this problem. Simulations are carried out for a range of wave ratio 0 to 0.6, aspect ratio A 1 to 5, and Rayleigh number Ra 10 to 1000. Results are presented in the form of streamlines, isotherms, and local and average Nusselt numbers. Comparison with known results from the open literature for natural convection in a porous cavity with plane vertical walls ( 0) is in excellent agreement. In all the results presented, steady state has been attained.
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ABSTRACT The steady-state free convection inside a cavity made of two horizontal straight walls and two vertical bent-wavy walls and filled with a fluid-saturated porous medium is numerically investigated in the present paper. The wavy... more
ABSTRACT The steady-state free convection inside a cavity made of two horizontal straight walls and two vertical bent-wavy walls and filled with a fluid-saturated porous medium is numerically investigated in the present paper. The wavy walls are assumed to follow a profile of cosine curve. The horizontal walls are kept adiabatic, while the bent-wavy walls are isothermal but kept at different temperatures. The Darcy and energy equations (in non-dimensional stream function and temperature formulation) are solved numerically using the Galerkin Finite Element Method (FEM). Flow and heat transfer characteristics (isothermal, streamlines and local and average Nusselt numbers) are investigated for some values of the Rayleigh number, cavity aspect ratio and surface waviness parameter. The present results are compared with those reported in the open literature for a square cavity with straight walls. It was found that these results are in excellent agreement.
Research Interests: Engineering, Materials Science, Mechanics, Convection, Heat Transfer, and 13 moreFinite element method, Heat and Mass Transfer, Mathematical Sciences, Porous Media, Natural Convection, Physical sciences, Free Convection, Nusselt Number, Porous Medium, Stream Function, Aspect Ratio, Waviness, and Rayleigh Number
Research Interests: Engineering, Materials Science, Mechanics, Heat Transfer, Heat and Mass Transfer, and 12 moreMathematical Sciences, Natural Convection, Physical sciences, Free Convection, Finite Difference Method, Nusselt Number, Porous Medium, Oblique Case, Stream Function, Aspect Ratio, Cartesian Coordinate System, and Numerical Calculation
... A numerical study about the entropy generation for natural convection in an inclined porous cavity by using the second law of thermodynamics has not yet been encountered. ... Consider the flow of a Newtonian fluid within a square... more
... A numerical study about the entropy generation for natural convection in an inclined porous cavity by using the second law of thermodynamics has not yet been encountered. ... Consider the flow of a Newtonian fluid within a square porous enclosure as depicted in Fig. ...
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ABSTRACT Experiments were conducted in a swirl stabilized premixed combustor at atmospheric pressure in order to study the stability and structure of lean premixed methane air flames. Swirl number of the combustor was 0.74. The lab scale... more
ABSTRACT Experiments were conducted in a swirl stabilized premixed combustor at atmospheric pressure in order to study the stability and structure of lean premixed methane air flames. Swirl number of the combustor was 0.74. The lab scale combustor was operated up to 30 kW of thermal power during measurements. Experiments focused on two main aspects of the combustion system. First the relation between the cold flowfield and the flame stabilization is examined. It is observed that, the structure of the flame near the dump plane corresponds closely to the features of the non-reacting air flowfield. The flame is seen to be stabilized on the boundary of the recirculation region. Lean blowout limits of the combustor that operates within the flamelet regime were also recovered. A correlation linking the blowout equivalence ratio to laminar flame speed is presented.
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Recently, research on entropy generation minimization using the second law of thermodynamics has been studied for many different situations. Further, the utilization of the second law of thermodynamics in thermal design decision has been... more
Recently, research on entropy generation minimization using the second law of thermodynamics has been studied for many different situations. Further, the utilization of the second law of thermodynamics in thermal design decision has been developed and applied for porous media. For this reason, these lines of inquiry have been largely motivated by a desire to obtain an in-depth understanding of the relevant physics underlying this phenomena. Therefore, in this chapter, entropy generation has been reviewed for porous media and the recent studies related to entropy generation have been investigated for porous cavities and channels for different boundary conditions and physical situations.
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258-260The effect of foam layout on NO emission inside a a porous burner with three porous media layers has been experimentally studied. The experimental set-up included two zones, combustion and preheating. At the combustion zone, there... more
258-260The effect of foam layout on NO emission inside a a porous burner with three porous media layers has been experimentally studied. The experimental set-up included two zones, combustion and preheating. At the combustion zone, there are five layers of porous media with different pore densities; at the preheating zone, there are alumina spheres as porous media. Numerical solutions show that permutation of porous foams with different pore densities has an effect on emission rates. The purpose of this experimental study is to investigate effect of porous media permutation and equivalence on emission rates. Results indicate that when the foam density is decreased from combustion zone to exit, NO emission is declined
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Purpose The purpose of this study is to numerically analyze the mixed convection and entropy generation in an annulus with a rotating heated inner cylinder for single-wall carbon nanotube (SWCNT)–water nanofluid flow using local thermal... more
Purpose The purpose of this study is to numerically analyze the mixed convection and entropy generation in an annulus with a rotating heated inner cylinder for single-wall carbon nanotube (SWCNT)–water nanofluid flow using local thermal nonequilibrium (LTNE) model. An examination of the system behavior is presented considering the heat-generating solid phase inside the porous layer partly filled at the inner surface of the outer cylinder. Design/methodology/approach The discretized governing equations for nanofluid and porous layer by means of the finite volume method are solved by using the SIMPLE algorithm. Findings It is found that the buoyancy force and rotational effect have an important impact on the change of the strength of streamlines and isotherms for nanofluid flow. The minimum average Nusselt number on the inner cylinder is obtained at Ra$_E$ = 10$^4$, and the minimum total entropy generation is found at Re = 400 for given parameters. The entropy generation minimization ...
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Purpose The purpose of this study is to numerically investigate heat transfer and entropy generation between airframe and cabin-cargo departments in an aircraft. The conjugate forced convection and entropy generation in a cylindrical... more
Purpose The purpose of this study is to numerically investigate heat transfer and entropy generation between airframe and cabin-cargo departments in an aircraft. The conjugate forced convection and entropy generation in a cylindrical cavity within air channel partly filled with porous insulation material as simplified geometry for airframe and cabin-cargo departments are considered under local thermal non-equilibrium condition. Design/methodology/approach The non-dimensional governing equations for fluid and porous media discretized by finite volume method are solved using the SIMPLE algorithm with pressure and velocity correction. Findings The effects of the following parameters on the problem are investigated; Reynolds number, Darcy number, the size of inlet and exit cross-section, thermal conductivity ratio for solid and fluid phases, angle between the vertical symmetry axis and the end of channel wall exit and the gap between adiabatic channel wall and horizontal adiabatic wall ...
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Bir yakitin havayi en az kirletecek sekilde yanmasi oldukca onemlidir. Her gun bu konu ile ilgili kirletici gaz salimlarini kisitlayan yeni yasal duzenlemeler yururluge girmektedir. Ikinci bir onemli konu da yuksek yogunlukta hacimsel isi... more
Bir yakitin havayi en az kirletecek sekilde yanmasi oldukca onemlidir. Her gun bu konu ile ilgili kirletici gaz salimlarini kisitlayan yeni yasal duzenlemeler yururluge girmektedir. Ikinci bir onemli konu da yuksek yogunlukta hacimsel isi aciga cikisini elde etmektir. Gozenekli ortamda yanma bu iki onemli konuda cozum uretebilmektedir. Bu calismada, cesitli sayisal analizler yapilarak isil verimlilik ve yanma, 5kW’lik gozenekli ortamda simetrik ve iki boyutlu bir problem seklinde incelenmistir. Cozum alani dort adet alt-alandan olusmaktadir; iki art arda gozenekli ortam (ilki dusuk poroziteli, ikincisi yuksek poroziteli), sabit akis hizina sahip bir su tanki ve kati duvar. Yanmada tepkimeye girenler olarak metan-hava karisimi degisik fazla hava katsayilarinda kullanilmistir ve yakici tasariminin en iyilenmesi amaciyla cesitli su akis debileri her bir esdegerlik orani icin test edilmistir. Navier-Stokes, enerji (isil denge modeli) ve tur denklemleri iki boyutlu simetrik modelimiz ici...
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Purpose The purpose of this study is to numerically investigate the confined single-walled carbon nanotube-water nanofluid jet impingement heating of a cooled surface with a uniform heat flux in the presence of a porous layer. The... more
Purpose The purpose of this study is to numerically investigate the confined single-walled carbon nanotube-water nanofluid jet impingement heating of a cooled surface with a uniform heat flux in the presence of a porous layer. The analysis of the convective heat transfer mechanism is introduced considering the buoyancy force effect under local thermal non-equilibrium conditions. Design/methodology/approach The governing equations for the nanofluid and solid phase are discretized by the finite volume method and the SIMPLE algorithm is used to solve these equations. Findings It is observed that there is an increase in a local variation of temperature along the upper wall with increasing Reynolds, Darcy and Grashof numbers. For given parameters, the optimum values of thermal conductivity ratio and porous layer thickness leading to better heating on the upper wall are found as Kr = 1.0 and S = 0.5, respectively. The maximum and minimum values of temperature on the upper wall are obtaine...
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Purpose The aim of this paper is to investigate the conjugate forced convection in a semi-cylindrical cavity with air flow. Isotherms, streamlines, Bejan number and local entropy generation number are obtained for the semi-cylindrical... more
Purpose The aim of this paper is to investigate the conjugate forced convection in a semi-cylindrical cavity with air flow. Isotherms, streamlines, Bejan number and local entropy generation number are obtained for the semi-cylindrical cavity. Local Nusselt number, the temperature and the skin friction along the interface wall are calculated with different Reynolds numbers and geometric configurations. Design/methodology/approach The governing differential equations discretized by finite volume method are solved using SIMPLE algorithm. In this study, collocated grid, where all flow variables are stored at the same location, is used. Alternating direction implicit method and tri-diagonal matrix algorithm are used to solve linear algebraic equation systems. Findings The effects of Reynolds numbers, inlet and exit cross-section, the locations of exit section on fluid flow are also numerically investigated. It has been observed that since the secondary vortices developed near the exit cr...
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... [4] Lee, JH, Goldstein, RJ, An experimental study on natural convection heat transfer in an inclinedsquare enclosure containing internal energy sources, J. of Heat Transfer, 110 (1988), 345 [5] Yedder, RB, Bilgen, E., Turbulent... more
... [4] Lee, JH, Goldstein, RJ, An experimental study on natural convection heat transfer in an inclinedsquare enclosure containing internal energy sources, J. of Heat Transfer, 110 (1988), 345 [5] Yedder, RB, Bilgen, E., Turbulent natural convection and conduction in enclosures ...
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Research Interests: Materials Science, Mechanics, Chemistry, Convection, Heat Transfer, and 14 moreNatural Convection, Thermal Stress, Oscillations, Laminar Flow, Industrial Application, Enclosure, Free Convection, Temperature Gradient, Finite Volume Method, Prandtl Number, Velocity Field, Electrical And Electronic Engineering, Rayleigh Number, and Temperature field
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... Doğal gözenekli ortam ola-rak, deniz kumu, kireçtaşı, odun, çavdar ekmeği, akciğer ve dokuları örnek verebiliriz. ... Çok sayıda bilimsel ve teknolojik uygulama alanı olması sebebi ile gözenekli bir ortamda ısı ve kütle geçişi... more
... Doğal gözenekli ortam ola-rak, deniz kumu, kireçtaşı, odun, çavdar ekmeği, akciğer ve dokuları örnek verebiliriz. ... Çok sayıda bilimsel ve teknolojik uygulama alanı olması sebebi ile gözenekli bir ortamda ısı ve kütle geçişi meka-nizmasının anlaşılması ve iyi bilinmesi gerekir. ...