Yazar "Akyol, Ugur" seçeneğine göre listele

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    Determination of optimum operating conditions and simulation of drying in a textile drying process
    (Taylor & Francis Ltd, 2013) Akyol, Ugur; Kahveci, Kamil; Cihan, Ahmet
    In 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.
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    DRYING BEHAVIOR OF CULTURED MUSHROOMS
    (Wiley, 2010) Celen, Soner; Kahveci, Kamil; Akyol, Ugur; Haksever, Aysen
    In this study, the drying behavior of cultured mushrooms with an initial moisture content of 93% (drying basis [d.b.]) was investigated experimentally for different slice thicknesses and drying air temperatures, and the suitability of various drying models in defining the drying behavior of mushrooms was determined by statistical analysis. Drying operation was carried out at temperatures of 40, 45, 50 and 60C and at a fixed air velocity of 2 m/s. The slice thicknesses of mushrooms were taken as 2, 4 and 6 mm. The experimental results show that the drying temperature has a significant effect on the moisture removal from mushrooms. However, it is also observed that increasing the temperature above a certain value for large values of slice thickness does not have a considerable effect on the drying rate. It may also be concluded from the experimental results that the increase in the slice thickness slows down the drying rate significantly. Furthermore, the results of statistical analysis show that the most suitable model in defining the drying behavior of mushrooms is the diffusion approach model.
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    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, Dincer
    Drying 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.
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    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, Ahmet
    In 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.
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    Estimation of power output and thermodynamic analysis of standard and finned photovoltaic panels
    (Taylor & Francis Inc, 2023) Akyol, Ugur; Akal, Dincer; Durak, Ahmet
    This study deals with the estimation of power output and also thermodynamic analysis of two different photovoltaic panels. One of the panels is a standard photovoltaic module without fins (SPV), and the other one is a photovoltaic module with fins (FPV). First, a multi-layer feed-forward neural network structure is designed to estimate the daily power produced by photovoltaic modules. Furthermore, energy and exergy analyses were carried out to compare the performance of SPV and FPV panels. According to the thermodynamic analysis results using the experimental data obtained for two days (July 3, 2020 and August 4, 2020), it was calculated that the energy efficiency increased by a maximum of 8.77% and the exergy efficiency increased by a maximum of 25.9% in the FPV panel compared to the SPV panel. Moreover, considering the data obtained for each day during three months (July, August, and September), the total energy production increase in the FPV panel is approximately 6.7% compared to the SPV panel.
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    Experimental and numerical investigation of heat transfer in a channel with multiple phase change materials (PCMs)
    (Elsevier, 2022) Akyol, Erhan; Hacihafizoglu, Oktay; Susantez, Cigdem; Kahveci, Kamil; Akyol, Ugur
    In this study, the thermal performance of an air-phase change material (PCM) unit used in free cooling applications was examined experimentally and numerically by Comsol finite element simulation software. Effects of the air inlet temperature, velocity and also PCM configuration on the efficiency of the air-PCM unit were investigated. Experiments were performed on PCM unit, which is a channel including PCM plates inside and exposed to medium air entrance from one side. The air in contact with the plates inside this unit is cooled and contributes the room temperature to decrease. The experimental work was carried out at two different ambient temperatures in a well-insulated room. Three different configurations of paraffin-based pure RT22HC and RT25HC were studied. Effects of air inlet temperature and velocity on the heat transfer, channel outlet temperature, performance of the air-PCM heat exchanger, cooling power of the system and also total amount of heat absorbed by the PCM were investigated. The initial temperature of the PCMs is 16 degrees C and experiments were carried out for two different average inlet temperature values (27 and 29 degrees C) and two different average velocities (1.3 and 1.8 m/s) of the air at the channel entrance. According to the results, it was concluded that the air inlet temperature and air inlet velocity have a substantial effect on the thermal performance of the air-PCM unit. It was observed that the melting time decreased and the channel outlet temperature increased with the increase of air inlet temperature and velocity. 2 degrees C increase of in the inlet temperature increased the total amount of heat absorbed by PCMs by 31%, while an increase of the inlet velocity by 0.5 m/s increased it by 16%. The results revealed that the increase of the inlet velocity and with the inlet temperature increased the thermal energy absorbed by 44%. In addition, it was observed that the average efficiency increased by 37% with 2 degrees C increase of inlet temperature and 0.5 m/s decrease in the inlet velocity.
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    A mathematical model for through-air drying process of yarn bobbins
    (Taylor & Francis Ltd, 2022) Akyol, Ugur; Karakoca, Alper; Shaliyev, Rafayel; Kahveci, Kamil; Cihan, Ahmet
    In 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.
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    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, Ahmet
    In 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.
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    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, Dincer
    In 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.
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    Single Layer Drying Behavior of Apple Slices in a Microwave Dryer
    (Trans Tech Publications Ltd, 2011) Celen, Soner; Kahveci, Kamil; Akyol, Ugur
    In this study, the drying behaviour of single layer apple slices of 5mm thickness in a microwave dryer was investigated experimentally for four different microwave power levels (90 W, 180 W, 360 W and 600 W) and suitability of drying models available in the literature in simulating the drying behaviour of apple slices was determined by statistical analysis. The performance of these models was determined by comparing the coefficients of determination (R), reduced chisquares (chi(2)) and root mean square errors (RMSE) of the models. The results show that drying time and energy consumption decreases considerably with increasing microwave power. The results also show that, among of the models proposed, the Verma et al. model gives the best fit with experimental data for all drying conditions considered. In order to determine the colour change of apple, a colour meter was also used in this study and found that L* and a* values were not significantly different from the values of the fresh apples.
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    Thermophysical parameter estimation of a wool bobbin during convective drying process
    (Taylor & Francis Ltd, 2010) Akyol, Ugur; Cihan, Ahmet; Shaliyev, Rafayel
    In 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.