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Öğe Bobin kurutma makinesinin modellenmesi, optimizasyonu ve otomasyonu(2010) Kahveci, Kamil; Akyol, Uğur; Cihan, Ahmet[Abstract Nıt Available]Öğe Determination of optimum operating conditions and simulation of drying in a textile drying process(Taylor & Francis Ltd, 2013) Akyol, Ugur; Kahveci, Kamil; Cihan, AhmetIn this study, drying behavior of viscose yarn bobbins was investigated experimentally to specify the optimum drying conditions and a drying model was proposed for simulation of drying. The experiments were conducted in a pressurized hot-air bobbin dryer, which was designed and manufactured based on the dryers used in the textile industry. Drying process was performed for various drying parameters: bobbin diameter, drying temperature, drying pressure, and volumetric flow rate of drying air. The results show that total drying time is strongly dependent on drying pressure, drying temperature, and volumetric flow rate and increase at these parameters shortens the drying time considerably. The results also show that the minimum energy consumption is for lower values of drying temperature and drying pressure and modest and higher values of volumetric flow rate. Simulation results show that the most appropriate model in describing the drying curves of viscose yarn bobbins is the stretched exponential model.Öğe A diffusion based model for intermittent drying of rough rice(Springer, 2008) Cihan, Ahmet; Kahveci, Kamil; Hacihafizoglu, Oktay; de Lima, Antonio G. B.In this study, intermittent drying behavior of single layer rough rice with a moisture content of between 22 and 24% on the dry basis was simulated by means of a liquid diffusion model based on a prolate spheroid geometry. For this purpose, solution of the liquid diffusion equation was fitted to the experimental data for the drying air temperature 40 degrees C, drying velocity 1.5 ms(-1) and tempering periods ranging from 0 to 1 h. In order to make a comparison, solution of the liquid diffusion equation for a finite cylindrical geometry was also fitted to the experimental data. The results show that the liquid diffusion model based on a prolate spheroid geometry explains the drying behavior of rough rice more accurately. The results also show that greater variations occur in diffusion coefficient with increasing tempering time for prolate spheroid geometry which is more realistic geometry for a rough rice grain.Öğe Drying Behavior of Polyester Based Yarn Bobbins in a Hot-Air Bobbin Dryer(Trans Tech Publications Ltd, 2011) Cihan, Ahmet; Kahveci, Kamil; Akyol, Ugur; Akal, DincerDrying behavior of polyester based yarn bobbins (67% polyester, 33% viscose) was simulated for different drying air temperatures by a simultaneous heat and mass transfer model. In the model, it was assumed that mass transfer is occurred by the diffusion mechanism. In the study, firstly drying behavior of polyester bobbins for different drying air temperatures has been determined experimentally. The experiments were conducted on an experimental hot-air bobbin dryer designed and manufactured based on hot-air bobbin dryers used in textile industry. In the experimental setup, temperatures of different points of the bobbins were measured by thermocouples placed inside the bobbins and weight of the bobbins during the drying period were determined by a load cell. Then moisture ratio and temperature values of the model have been fitted to the experimental ones. The fit was performed by selecting the values for the diffusion coefficient and the thermal diffusivity in the model in such a way that these values make the sum of the squared differences between the experimental and the model results for moisture ratio and temperature minimum. The results show that there is a good agreement between the model results and the experimental ones. The results also show that temperature has a significant effect on mass transfer and temperature dependence of the diffusion coefficient may be explained by an Arrhenius type relation.Öğe Drying kinetics of cotton based yarn bobbins in a pressurized hot-air convective dryer(Sage Publications Ltd, 2017) Akal, Dincer; Kahveci, Kamil; Akyol, Ugur; Cihan, AhmetIn this study, the drying kinetics of cotton bobbin drying process in a pressurized hot-air convective bobbin dryer was investigated, and a drying model was introduced for the simulation of drying. Tests were conducted for drying temperatures of 70?, 80?, and 90?; effective drying air pressures of 1, 2, and 3 bars; three volumetric flow rates of 42.5, 55, and 67.5 m(3)/h; and for three different bobbin diameters of 10, 14, and 18cm. Optimum drying conditions were specified in terms of drying time and energy consumption. Results indicate that the total drying time depends significantly on the drying temperature, pressure, and volumetric flow rate. Results show that the minimum energy consumption is obtained for low values of drying air temperatures and pressures, and for moderate and high values of drying air volumetric flow rates. It was also found that the Page model is suitable for simulating the drying behavior of cotton yarn bobbins. Finally, results show that effective diffusion coefficient values are between 1.132x10(-7) m(2)/s and 3.453x10(-7) m(2)/s depending on the values of drying parameters.Öğe Finite Element Simulation of Drying of Rough Rice(Trans Tech Publications Ltd, 2011) Hacihafizoglu, Oktay; Cihan, Ahmet; Kahveci, KamilRough rice has high moisture content at harvest, and if their moisture content is not reduced to about 12% on the dry basis they decay due to infestation and mold growth. Drying process is generally performed by heating ambient air and then sending it by forced convection over the rough rice to be dried. The aim in heating air to a certain temperature is to reduce the relative humidity of the air, which has a positive effect on the drying potential. In this study, drying behavior of single layer rough rice for different drying air temperature was simulated by means of a liquid diffusion model numerically by finite element modeling and simulation software. The results show that temperature is an effective factor on the drying rate. The results also show that as drying proceeds, a moisture gradient develops within the grain. This slows down the drying rate considerably. Therefore, it can be concluded that performing drying with an intermittent period instead of continuous drying will cause a considerable energy-saving.Öğe A liquid diffusion model for thin-layer drying of rough rice(Springer, 2008) Hacihafizoglu, Oktay; Cihan, Ahmet; Kahveci, Kamil; de Lima, Antonio G. B.In this study, the drying behavior of single-layer rough rice with a moisture content of between 22 and 24% on the dry basis was simulated by means of a liquid diffusion model, based on a prolate spheroid geometry. For this purpose, the solution of liquid diffusion equation was fitted to the experimental moisture ratios for drying air temperatures between 40 and 60 degrees C and velocity 1.5 m s(-1). In order to make a comparison, the predictions of liquid diffusion equations for a spherical and finite cylindrical geometry were also fitted to the experimental results. Modeling was performed by selecting the diffusion coefficients in diffusion equations in such a manner as to minimize the sum of the squared differences between the experimental results and the theoretical predictions. It was found that the liquid diffusion model, based on a prolate spheroid geometry, explains single-layer drying behavior of rough rice well. It was also found that the model, based on a prolate spheroid geometry, has better agreement with the experimental results than the other geometries.Öğe A mathematical model for through-air drying process of yarn bobbins(Taylor & Francis Ltd, 2022) Akyol, Ugur; Karakoca, Alper; Shaliyev, Rafayel; Kahveci, Kamil; Cihan, AhmetIn this study, a mathematical model has been developed to simulate the through-air drying process of yarn bobbins. For this purpose, experimental data was obtained in a prototype experimental set up by passing pressurized hot air through the wool yarn bobbins. First of all, the physical phenomenon expressing the drying process has been reduced to the heat transfer problem and then a mathematical model has been written for the drying process which also includes the convective term. Using the experimental data, the coefficient included in the mathematical model was found by the extremal method. So, an inverse problem was solved. The accuracy of the model was checked by comparing with the experimentally obtained temperature values after solving a direct heat transfer problem in the given conditions. Good correlation between the obtained model results and the experimental results shows the accuracy of the mathematical model.Öğe Mathematical modelling of drying of thin layer rough rice(Elsevier, 2008) Hacihafizoglu, Okay; Cihan, Ahmet; Kahveci, KamilIn this study, suitability of several drying models available in literature in defining thin layer drying behaviour of long-grain rough rice has been examined by using statistical analysis. For this purpose, drying models have been fitted to experimental data by means of the coefficients in the models for the drying air temperatures 40 degrees C, 45 degrees C, 50 degrees C, 55 degrees C, and 60 degrees C and at an airflow rate of 1.5 ms(-1) and 3.0 ms(-1). The results show that the Midilli et al. is the most appropriate model for drying behaviour of thin layer rough rice. Furthermore, among the two parameter models, the Page models and, among the three parameter models, the Verma et al. and the diffusion approach models give better fit. The coefficients a and b, the drying coefficient k and the exponent n in the Midilli et al. model can be expressed as a function of temperature and velocity of the drying air. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe A model for predicting drying time period of wool yarn bobbins using computational intelligence techniques(Sage Publications Ltd, 2015) Akyol, Ugur; Tufekci, Pinar; Kahveci, Kamil; Cihan, AhmetIn this study, a predictive model has been developed using computational intelligence techniques for the prediction of drying time in the wool yarn bobbin drying process. The bobbin drying process is influenced by various drying parameters, 19 of which were used as input variables in the dataset. These parameters affect the drying time of yarn bobbins, which is considered as the target variable. The dataset, which consists of these input and target variables, was collected from an experimental yarn bobbin drying system. Firstly, the most effective input variables on the target variable, named as the best feature subset of the dataset, were investigated by using a filter-based feature selection method. As a result, the most important five parameters were obtained as the best feature subset. Afterwards, the most successful method that can predict the drying time of wool yarn bobbins with the highest accuracy was explored amongst the 16 computational intelligence methods for the best feature subset. Finally, the best performance has been found by the REP tree method, which achieved minimum error and time taken to build the model.Öğe Modelling of intermittent drying of thin layer rough rice(Elsevier Sci Ltd, 2007) Cihan, Ahmet; Kahveci, Kamil; Hacihafizoglu, OktayVarious mathematical models in describing the intermittent drying characteristics of thin layer rough rice were investigated. Experimental values for drying temperature 40 degrees C, drying velocity 1.5 ms(-1) and tempering period ranging from 0 h to 1 h were fitted to the theoretical models to relate the parameters of the drying models with the drying conditions. Suitability of fitting of the experimental data by models was specified as comparing the correlation coefficient, standard error and mean square deviation. The Midilli model was found to be the most adequate model in describing the intermittent drying of thin layer rough rice. The coefficient a and b, drying coefficient k and exponent n in the Midilli model can. be expressed as a polynomial function of tempering time. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Numerical Investigation of Heat Transfer in Friction Welding of Cylindrical Tubes(Begell House Inc, 2009) Can, Yilmaz; Kahveci, Kamil; Cihan, AhmetHeat transfer in friction welding of cylindrical tubes is considered in the present study and the governing equations are solved numerically using an explicit finite difference technique to determine the temperature field. The values of the radius ratio in the problem are selected as r(r) = 0.25, 0.50, and 0.75. Results show that the temperature of tubes increases with increasing radius ratio. In addition, as the generated heat is proportional to the interface radius, the temperature increases from the inner surface but drops slightly towards the periphery due to the convection effect. The temperature field is of a similar form for all values of the radius ratio, but the radial and axial temperature gradients change at certain amounts.Öğe Simulation of Drying Behavior of Cotton Bobbins by a Simultaneous Heat and Mass Transfer Model(Trans Tech Publications Ltd, 2011) Akyol, Ugur; Kahveci, Kamil; Cihan, Ahmet; Akal, DincerIn this study, the drying process of cotton bobbins for different drying air temperatures has been simulated by a simultaneous heat and mass transfer model. In the model, the mass transfer is assumed to be controlled by diffusion. In order to make the simulation, firstly, drying behavior of cotton bobbins for different drying air temperatures has been determined on an experimental bobbin dryer setup which was designed and manufactured based on hot-air bobbin dryers used in textile industry. In the experimental setup, temperatures of different points in cotton bobbins were measured by thermocouples placed inside the bobbins, and weights of the bobbins during the drying period were determined by means of a load cell. Then, moisture ratio and temperature values of the model have been fitted to the experimental ones. The fit was performed by selecting the values for the diffusion coefficient and the thermal diffusivity in the model in such a way that these values make the sum of the squared differences between the experimental and the model results for moisture ratio and temperature minimum. Results show that there is a good agreement between the model results and the experimental measurements. The results also show that temperature has a significant effect on mass transfer and the temperature dependence of the diffusion coefficient may be expressed by an Arrhenius type relation.Öğe Thermophysical parameter estimation of a wool bobbin during convective drying process(Taylor & Francis Ltd, 2010) Akyol, Ugur; Cihan, Ahmet; Shaliyev, RafayelIn this work, an inverse heat transfer problem was solved by using experimental temperature data to estimate the effective thermal properties as well as the effective heat transfer coefficients on the inner and outer surfaces of a moist wool bobbin during a hot-air drying process. Before the inverse problem solution, the mathematical model of the drying wool bobbin was expressed by means of a single energy conservation equation and convenient boundary conditions, and then, the heat and mass transfer problem in the model was reduced to a heat conduction problem. The inverse problem was solved by direct method with finite difference scheme. Model temperatures obtained from the solution of the direct problem were used for verification of the effective thermophysical properties. The results with good agreement between the model and the experimental temperatures confirm the accuracy of the effective thermophysical properties of the bobbin estimated by the inverse method.
