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Öğe Eddy diffusivity of particles in turbulent flow in rough channels(Elsevier Sci Ltd, 2002) Altunbas, A; Kelbaliyev, G; Ceylan, KThe eddy diffusivity coefficient of particles depends on the flow characteristics and on the physical properties of the particles. Experimental data and theoretical considerations suggest that the ratio of the eddy diffusion coefficient of particles (D-TP) to the eddy diffusion coefficient of fluid (D-T) is dependent mainly on the friction velocity of fluid (U-*), the sedimentation velocity of the particles (V-s), the Reynolds number (Re) of the flow and also the relative roughness of channel.(epsilon/D). It is shown here that this relation among these parameters may be represented as D-TP/D-T = mu(R) proportional to (U-*(m)/V-S)(n), where m and n are empirical constants. Some new empirical relationships are proposed for the eddy diffusion coefficient of particles in the turbulent flow in vertical or horizontal channels. The results compare favorably with experimental data from the literature. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Estimation of the maximum stable drop sizes, coalescence frequencies and the size distributions in isotropic turbulent dispersions(Elsevier, 2003) Ceylan, S; Kelbaliyev, G; Ceylan, KThe process of coalescence or breakup of drops in turbulent flow is of importance in many technical applications. A new size distribution takes place due to the coalescence or the breakup of the drops during the motion of a dispersed system. Based on the experimental data given in the literature, some new empirical relationships are developed in this paper to evaluate the maximum stable drop sizes, the coalescence frequencies and the drop size distribution in an isotropic turbulent flow. The relationships are developed essentially in terms of the particle Reynolds number or of the physical properties of the system. The Focker-Planck equation is used to estimate the particle size distribution. The model predictions are compared with the experimental data given in the literature. The results indicated that the predicted values and the experimental data are in a good agreement. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Estimation of the minimum stable drop sizes, break-up frequencies, and size distributions in turbulent dispersions(Taylor & Francis Inc, 2005) Kelbaliyev, G; Ceylan, KThe breakage of drops or bubbles in isotropic turbulent dispersions has been investigated. Based on the experimental data given in the literature, some new empirical relationships are derived to evaluate the minimum stable drop sizes, the breakup frequencies, and the drop size distribution in turbulent dispersions. The solutions of the stochastic Focker-Planck equation are used to estimate the particle size distribution. The relationships are expressed essentially in terms of the system properties. In addition, a new relationship was proposed to estimate the ranges of Reynolds, Weber, or Morton number, at which the drag coefficient is minimum. The model predictions are compared with the experimental data given in the literature.Öğe Kinetics of drop breakage in stirred vessels under turbulent conditions(Taylor & Francis Inc, 2005) Sis, H; Kelbaliyev, G; Chander, SThe emulsification of dodecane oil was studied in a standard stirred vessel filled with distilled water. The in situ size distribution of the drops was measured at certain time intervals by using a particle size analyzer while stirring. The results showed that an increase in the stirring time and stirring rate resulted in a decrease in the mean drop size of drops and shifted the drop size distribution toward smaller sizes. The minimum droplet size in the turbulent flow was found to be proportional to a(min) similar to (WD)(-1.75). Normalization of data exhibited that the size distribution of drops is self-preserving. The distribution of mean drop size and distribution functions of drops were determined by using models developed from the Focker-Plank equation regarding size distribution of particles in turbulent flows. The evaluation of droplet breakage with time in isotropic turbulent flow showed that the size distribution can be represented by the summation of log-normal distribution function in series. It was found that the experimental data could be represented well by the empirical models.Öğe Modeling of drop coalescence in isotropic turbulent flow(Taylor & Francis Inc, 2006) Kelbaliyev, G; Sarimeseli, ACoalescence of drops in fully developed turbulent flow depends on the size of drops and the properties of the flow. By comparing the size of drops with the Kolmogoroff length scale, collision frequencies of drops have been determined. If lambda > lambda(0), then the collision frequency of drops in a gaseous medium is given as omega(c) similar to (epsilon(R)/a(2))(1/3) and for lambda > lambda(0), it is given as omega(c) similar to (epsilon(R)/nu(c))(1/2) in a liquid medium. New expressions for the fluctuation, thinning, and breaking of the intervening film between drops that is formed due to collisions were also suggested. At various Re and Mo numbers, for the calculation of maximum stable sizes of drops, some equations are suggested. In order to evaluate coalescence and break up rates a new dimensionless number, Ke = eta(c)epsilon(R)/g sigma, is introduced. This number is defined as the ratio of the energy of the turbulent flow to surface energy. As a result of the coalescence of drops, evolution of the distribution function with time is determined from the solution of the Focker-Planck equation. Comparisons of the calculated drop sizes with the experimental data reported in literature showed good agreement.Öğe Modeling of the break-up of deformable particles in developed turbulent flow(Pergamon-Elsevier Science Ltd, 2004) Sarimeseli, A; Kelbaliyev, GDynamic behavior of the drops and bubbles in developed turbulent flow depend on turbulent length scale (gimel), Morton (Mo), Weber (We) and Reynolds (Re-a) numbers. In the present work, in order to calculate the maximum stable size of drops and bubbles, the A factor of break-up, Ay (Ay = omegaa/U), that is the ratio of the break-up rate in developed turbulent flow to the mean velocity of the flow has been introduced and the effect of the pipe roughness on this factor has also been given. Comparison of all the results obtained in this study with those taken from the literature for the range of Mo less than or equal to 7, We less than or equal to 10 and Re-u less than or equal to 100 showed a good agreement. (C) 2004 Elsevier Ltd. All rights reserved.Öğe A new model for estimation of drag force in the flow of Newtonian fluids around rigid or deformable particles(Elsevier Science Sa, 2001) Ceylan, K; Altunbas, A; Kelbaliyev, GA number of relationships are given in the literature for estimation of the drag coefficients; however, most of these are applicable only for a narrow range of Reynolds number (Re). Some new empirical relationships are proposed in this study to estimate the drag coefficients in the flow of Newtonian liquids around the solid spherical or cylindrical particles and the deformable particles. An approximation series approach is used to develop these empirical relationships. It is shown that the proposed relationships can be applicable for the solid spherical or cylindrical particles in the range of 0.1 > Re > 10(6), and for the deformable particles (drops and bubbles) in the range of 0.1 > Re > 10(4). The predicted coefficients are in a good agreement with the experimental data given in the literature. (C) 2001 Elsevier Science B.V. All rights reserved.Öğe Rheological properties of asphalt-plastic blends(Marcel Dekker Inc, 2003) Colak, Y; Pehlivan, D; Sarimeseli, A; Kelbaliyev, GIn this article, the flow type of two different asphalt-plastic blends has been determined. One of these blends was prepared from the mixture of asphalt-cement that has a penetration degree of 60-70 (AC60-70) and low-density polyethylene (LDPE), and the other was prepared from the mixture of asphalt-cement that has a penetration degree of 150-200 (AC150-200) and low-density polyethylene (LDPE). Also, a model of the variation of the blend viscosity with temperature and concentration has been developed. It was found that this model is in a good agreement with the experimental data obtained and the relative error is calculated as 10-15%.Öğe The roughness effects on friction and heat transfer in the fully developed turbulent flow in pipes(Pergamon-Elsevier Science Ltd, 2003) Ceylan, K; Kelbaliyev, GConvective heat transfer coefficient is strongly influenced by the mechanism of flow during forced convection. In this paper, the effect of pipe roughness on friction factor and convective heat transfer in fully developed turbulent flow are briefly discussed. A correlation for the friction factor applicable in the region of transition to the fully developed turbulent flow regime is proposed. Using this relationship, some new approximation formulae are proposed to predict the convective heat transfer coefficients in the pipes with a relative roughness of epsilon/D less than or equal to 0.05. The effectiveness parameter. for the heat transfer is investigated as a function of the pipe roughness, Reynolds number and Prandtl number. The effect of fouling is also briefly discussed. The: predictions of the proposed correlations are compared with the experimental data and with some other previous correlations given in the literature. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Sedimentation of solid particles in turbulent flow in horizontal channels(Elsevier Science Sa, 2004) Sarimeseli, A; Kelbaliyev, GSedimentation of particles in horizontal channels in turbulent flow is commonly encountered in industrial processes. Investigations showed that the sedimentation velocity of particles in horizontal channels is nonsymmetrical along the cross-section of channels due to gravity. In this work, new expressions for the calculation of the sedimentation velocity of particles and the thickness of the sediment layer at the bottom of a horizontal channel are suggested. The entrainment and the transport rates of the particles from the sediment layer are also determined, and it was found that the entrainment rate is proportional to the square power of the friction velocity and inversely proportional to the viscosity of the flow. Comparisons of the suggested equations in this work with published data from the literature showed good agreement. (C) 2004 Elsevier B.V. All rights reserved.Öğe Stochastical modeling of the granule size distribution in the agglomeration processes of powdered materials(Elsevier Science Sa, 2001) Ceylan, K; Kelbaliyev, GPowders with the correct amount of a liquid binder can be formed into agglomerates by vibrating, shaking or paddle mixing. Rotating drums or disks are commonly used in industry. The break-up process of the drops of the binding liquid and the kinetics of the powder agglomeration affect the granule size distribution in the agglomerate. Generally, mathematical procedures are required to estimate such size distributions. A theoretical model is presented in this study to emphasize the major system parameters affecting the particle size distribution during agglomeration. First, an analytical relationship is derived to represent the changes in the droplet volume with time. Then, Focker-Planck equation is used to predict the granule size distribution in an agglomeration process. The model predictions are compared with the experimental data, The results indicated that the model predictions and the experimental data are in a good agreement. (C) 2001 Elsevier Science B.V. All rights reserved.Öğe A theoretical model for the particle distribution in a polydispersed solid mixture under hydrodynamic and gravitational effects(Elsevier Science Sa, 2001) Kelbaliyev, G; Ceylan, KThe particle size distribution in a polydispersed mixture significantly affects the technological behaviour of the mixture. Generally, mathematical procedures are required to estimate the particle size distribution or concentration distribution in a sorting process of such a mixture. A theoretical model is presented in this study to emphasize the major system parameters affecting the particle size distribution under hydrodynamic and gravitational effects. First, an analytical relationship is derived to represent the concentration profile in a sorting column during the classification of polydispersed mixtures. Then, the Focker-Planck equation is used to obtain the distribution function depending on the particle size. Some of the parameters of these analytical relationships are evaluated by comparing the equations with experimental data. The results indicated that the model predictions and the experimental data are in good agreement. (C) 2001 Elsevier Science B.V. All rights reserved.
