Volkan Kirmaci

Determination of freeze-drying behaviors of apples by artificial neural network

Freeze drying is the best drying technology regarding quality of the end product but it is an expensive method and the high costs of process limit its application to industrial scale. At the same time, the freeze-drying process is based on different parameters, such as drying time, pressure, sample thicknesses, chamber temperature, sample temperatures and relative humidity. So, the determination of drying behaviors, such as moisture content (MC), moisture ratio (MR) and drying rate (DR), of the freeze-drying process are too complex. In this paper, to help the freeze dryer designer and simplify this complex process, the use of artificial neural networks has been proposed. An artificial neural networks (ANN) model has been developed for determination the prediction of drying behaviors, such as MC, MR and DR, of apples in the freeze-drying process. The back-propagation learning algorithm with variant which is Levenberg-Marquardt (LM) and Fermi transfer function have been used in the network. In addition, the statistical validity of the developed model has been determined by using the coefficient of determination (R^2), the root means square error (RMSE) and the mean absolute percentage error (MAPE). R^2, RMSE and MAPE have been determined for MC, MR and DR, as 0.999, 0.0078895, 0.2668459, and 0.999, 0.0001099, 0.2968427 and 0.999, 0.0000008, 0.2703797, respectively.

An Experimental Investigation of the Cold Mass Fraction, Nozzle Number, and Inlet Pressure Effects on Performance of Counter Flow Vortex Tube

This paper discusses the experimental investigation of vortex tube performance as it relates to cold mass fraction, inlet pressure, and nozzle number. The orifices have been made of the polyamide plastic material. Five different orifices, each with two, three, four, five and six nozzles, respectively, were manufactured and used during the test. The experiments have been conducted with each one of those orifices shown above, and the performance of the vortex tube has been tested with air inlet pressures varying from 150 kPa to 700 kPa with 50 kPa increments and the cold mass fractions of 0.5―0.7 with 0.02 increments. The energy separation has been investigated by use of the experimentally obtained data. The results of the experimental study have shown that the inlet pressure was the most effective parameter on heating and the cooling performance of the vortex tube. This occurs due to the higher angular velocities and angular momentum conservation inside the vortex tube. The higher the inlet pressure produces, the higher the angular velocity difference between the center flow and the peripheral flow in the tube. Furthermore, the higher velocity also means a higher frictional heat formation between the wall and the flow at the wall surface of the tube. This results in lower cold outlet temperatures and higher hot outlet temperatures.

An Experimental Study on Freeze-Drying Behavior of Strawberries

In this article, the freeze-drying behavior and the drying kinetics of strawberries were investigated. Drying experiments were performed in a freeze-drying experimental setup constructed in the Department of Mechanical Education, Faculty of Technical Education, Gazi University, Ankara, Turkey. In experiments, 5- and 7-mm-thick sliced strawberry samples have been used. Some models, which were given in the literature, have been used to predict the drying behavior of strawberries. Experimental data findings were fitted for determining the best model to represent the drying behavior of strawberries and the drying kinetics used in these models. It was seen from the correlation coefficient, reduced chi-square, and root mean square error (0.9984, 2.688 × 10−4, 0.015 and 0.9976, 4.669 × 10−6, 0.002, respectively) that the Page model could sufficiently describe the drying behavior of 5- and 7-mm strawberry samples.

An Experimental Investigation of Performance and Exergy Analysis of a Counterflow Vortex Tube Having Various Nozzle Numbers at Different Inlet Pressures of Air, Oxygen, Nitrogen, and Argon

An experimental investigation has been carried out to determine the thermal behavior of cooling fluid as it passes through a vortex tube and the effects of the orifice nozzle number and the inlet pressure on the heating and cooling performance of the counterflow type vortex tube (RHVT). Experiments have been performed using oxygen (O 2 ), nitrogen (N 2 ), and argon (Ar). Five orifices have been fabricated and used during the experimental study with different nozzle numbers of 2, 3, 4, 5, and 6. The orifices used at these experiments are made of the polyamide plastic material. The thermal conductivity of polyamide plastic material is 0.25 W/m K. To determine the energy separation, the inlet pressure values were adjusted from 150 kPa to 700 kPa with 50 kPa increments for each one of the orifices and each one of the studied fluids. The vortex tube that was used during the experiments has L/D ratio of 15 and the cold mass fraction was held constant at 0.5. As a result of the experimental study, it is determined that the temperature gradient between the cold and hot exits is decreased depending on the orifice nozzle number increase. Exergy analyses have been realized for each one of the studied fluids under the same inlet pressures with the experiments (P i = 150-700). The exergy efficiency of the vortex tube is more affected by inlet pressure than nozzle number.

Statistical Assessment of Counter-Flow Vortex Tube Performance for Different Nozzle Numbers, Cold Mass Fractions, and Inlet Pressures Via Taguchi Method

Abstract In this article, the effect and optimization of process parameters in a counter-flow vortex tube on temperature difference were investigated through the Taguchi method. The experiments were planned as per Taguchis L27 orthogonal array with each experiment performed under different conditions of inlet pressure, nozzle number, and cold mass fraction. By means of analysis of variance and regression analysis, the effects of factors and their interactions on temperature difference were determined and modeled with a correlation coefficient of 93.5%. Accordingly, it was observed that temperature difference goes up with the increase in inlet pressure, and the cold mass fraction and decreases with the increase in nozzle number. In addition, the optimum settings of process parameters maximizing the temperature difference are an inlet pressure of 650 kPa, a nozzle number of 2, and a cold mass fraction of 0.7. Finally, confirmation tests verified that the Taguchi method was successful in the assessment of vortex tube parameters for temperature difference.

A Novel Data Preprocessing Method for the Modeling and Prediction of Freeze-Drying Behavior of Apples: Multiple Output–Dependent Data Scaling (MODDS)

In the present study, the freeze drying behavior of apples have been modeled and predicted. Because freeze-drying is a very expensive and complex process, modeling of the freeze-drying process is a challenging task. In this study, a novel data scaling method called multiple output–dependent data scaling (MODDS) has been proposed and combined with an adaptive neuro-fuzzy inference system (ANFIS) to forecast the moisture content (MC), moisture ratio (MR), and drying rate (DR) values, which are outputs of freeze-drying behavior of apples. The input parameters of the freeze drying system are the sample thicknesses, drying time, pressure, relative humidity, chamber temperature, and sample temperature. Using the input parameters, the outputs of the freeze-drying process of apples were predicted using a hybrid system based on MODDS and ANFIS. In the first stage, only input parameters were scaled using MODDS. In the second stage, the outputs of freeze drying of apples were predicted with the scaled input parameters using ANFIS algorithm. Ninety-two samples were included in the data set, including 10-, 7-, and 5-mm samples. In order to evaluate the performance of the proposed model, the mean absolute error (MAE), mean square error (MSE), root mean square error (RMSE), coefficient of determination (R 2), index of agreement (IA), and mean absolute percentage error (MAPE) were used. Though MSE values of 2.48, 0.035, and 0.011 and IA values of 0.887, 0.887, and 0.466 were obtained for MC, MR, and DR, respectively, using the ANFIS prediction algorithm the hybrid MODDS-ANFIS model achieved MSE values of 0.003, 0.00005, and 0.00007 and IA values of 0.999, 0.999, and 0.993 for the prediction of MC, MR, and DR, respectively. The results obtained demonstrate that the proposed hybrid system is a robust and efficient method for the modeling and prediction of freeze-drying behavior of apples.

The Effects of Orifice Nozzle Number on Heating and Cooling Performance of Vortex Tubes: An Experimental Study

Abstract In this study, the effects of the orifice nozzle number and the inlet pressure on the heating and cooling performance of the counter flow type vortex tube is investigated experimentally. The orifices are produced using the polyamide plastic material. Five orifices with 2, 3, 4, 5, and 6 nozzles are manufactured. In this study, air is used as a fluid. In the experiments, for each of the orifices, inlet pressures were adjusted from 150 kPa to 700 kPa with 50 kPa increments and the energy separation was investigated. During the experiments, cold mass fraction of the vortex tube that L/D ratio is 15, is held constant at 0.5. At the end of the experimental study, it is noted that the temperature gradient between the cold and hot fluid is decreased with increasing of the orifice nozzle number.

Farklı Kalınlıklardaki Elmaların Dondurarak Kurutma Davranışlarının Taguchi Metodu Kullanılarak Belirlenmesi

Dondurarak kurutma sonucta elde edilen urunun kalitesine gore en iyi kurutma teknolojisidir. Fakat, bu yontem pahalidir ve islemin yuksek maliyeti nedeniyle endustriyel olcekte uygulanmasi sinirlidir. Ayrica, dondurarak kurutma islemi, kurutma suresi, basinc, numune kalinliklari, hazne sicakligi, numune sicakliklari ve bagil nem miktari gibi farkli parametrelere baglidir. Bu yuzden dondurarak kurutma islemi icin nem icerigi, nem orani ve kurutma orani gibi kurutma davranislarinin belirlenmesi oldukca karmasiktir. Bu makalede dondurarak kurutmanin karmasik yapisi icin Taguchi metodu onerilmistir. Taguchi metodu, Taguchi’nin her L9 dikey sirasi ile gerceklestirilen her deneyin, dondurarak kurutma isleminde elmalarin nem icerigi, nem orani ve kurutma davranislari tahmini icin gelistirilmistir. Islem parametrelerinin etkisi ve optimal unsur ayarlarini belirlemek icin sinyal goruntu orani ve varyans analizi gerceklestirilmistir. Son olarak, nem icerigi, nem orani ve kurutma orani icin Taguchi metodunun onaylama testleri gerceklestirilerek basariya ulastigi dogrulanmistir.