Yazar "Kahveci, K." seçeneğine göre listele

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    Diffusion model for thin layer drying process of corn
    (Sage Publications Ltd, 2009) Hacihafizoglu, O.; Cihan, A.; Kahveci, K.; Korkmaz, C.
    In this study, single-layer drying behaviour of corn is simulated by liquid diffusion model by using the experimental data for drying temperatures between 40 and 70 degrees C and for a drying rate of 2 m/s. Three different geometries representing a corn grain, slab, sphere, and cylinder are taken into consideration to specify the geometry which yields best results. The drying curves are obtained by minimizing the sum of squared differences between experimental data and theoretical predictions. Results show that drying behaviour of corn can be modelled reasonably by liquid diffusion model and that the solution based on sphere geometry is in better agreement with the experimental drying behaviour as compared with other geometries. The results also show that the temperature and the movement velocity of moisture from the inner part of corn grains towards the outer part have a quite significant effect on the drying rate.
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    Mathematical modelling of drying of rough rice in stacks
    (Sage Publications Ltd, 2007) Akal, D.; Kahveci, K.; Cihan, A.
    In this study, drying behaviour of rough rice stacks up to 30 cm is simulated with several models. The suitability of models is determined by the statistical analysis by examining the values of correlation coefficient, standard deviation and mean squared deviation. The results showed that the best model to explain the drying characteristics of rough rice stack is the Midilli et al. model and the coefficients and exponent in the Midilli et al. model could be expressed as functions of drying temperatures and stack height. Statistical analyses also showed that among the models with two coefficients, that of Page, and among the models with three coefficients, that of Verma et al. and diffusion approach were acceptable models in expressing the drying behaviour of rough rice in stacks. Among the models considered here, the geometric model appeared to be the worst fit.
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    Stability of Unsteady Mixed Convection in a Horizontal Concentric Annulus
    (Isfahan Univ Technology, 2016) Kahveci, K.
    In this study, stability of unsteady mixed convection in a horizontal annulus between two concentric cylinders was investigated numerically. The surfaces of the cylinders were considered to be at fixed temperatures and it was assumed that the hot inner cylinder is rotating at a constant angular velocity. The buoyancy forces were formulated utilizing the Boussinesq approximation. The governing equations of fluid flow and heat transfer in the annulus were solved with a finite element method for different values of the geometric (radius ratio) and transport parameters (Rayleigh number and Reynolds number). Development of the convective flow and heat transfer was expressed by the average-Nusselt number for the outer cylinder. The results show that, for a narrow gap annulus, convective flow induces flow bifurcation and becomes unstable for high values of the Rayleigh number. Flow becomes more unstable with an increase in the Reynolds number. For a wide gap annulus, flow is stable for all values of the Rayleigh number if the rotation effects are small. On the other hand, convective flow becomes unstable for the modest and high values of the Ra number with an increase in the Re number.