Ugur Akyol

Determination of optimum operating conditions and simulation of drying in a textile drying process

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.

Thermophysical parameter estimation of a wool bobbin during convective drying process

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.

Simulation and thermodynamic analysis of a hot-air textile drying process

This paper is concerned with the simulation of drying behavior of wool yarn bobbins and also determination of the optimum operating conditions by using thermodynamic analysis. Firstly, experimental drying behavior of wool yarn bobbins was determined on a hot-air bobbin dryer. Empirical and semi-empirical mathematical models available in the literature were fitted to the experimental data. Then, a multi-layer feed forward neural network structure was used to predict drying behavior of wool bobbins. Afterwards, the first and second law analyses were performed to determine the optimum drying conditions. It was concluded that both the Two Term and Verma et al. models and also the artificial neural network model successfully simulates the drying process. Furthermore, according to the energy and exergy analyses’ results, Peff = 1 bar and T = 100°C were found to be the optimum operating conditions in convective drying process of wool yarn bobbins.

Drying kinetics of cotton based yarn bobbins in a pressurized hot-air convective dryer

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 m3/h; and for three different bobbin diameters of 10, 14, and 18 cm. 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 1.132 × 10−7 m2/s and 3.453×10−7 m2/s depending on the values of drying parameters.

A model for predicting drying time period of wool yarn bobbins using computational intelligence techniques

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.

Single Layer Drying Behavior of Apple Slices in a Microwave Dryer

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 chi-squares (χ2) 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.

Simulation of Drying Behavior of Cotton Bobbins by a Simultaneous Heat and Mass Transfer Model

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.

Drying Behavior of Polyester Based Yarn Bobbins in a Hot-Air Bobbin Dryer

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.