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Öğe Alternative heat insulation method for rigid construction walls(2021) Dagdeviren, Abdullah; Acar, Bahadır; Aydin, MuratThe purpose of heat insulation is to minimize the heat transfer between the interior and external\renvironment. Besides, it helps to prevent the structure of the constructions from the harmful heat effects\rbecause of heat transfer. This study presents an alternative method to achieve heat insulation in concrete\rwalls. 4 various heat insulation materials as wood shavings, fiberglass, granule rubber, and styrofoam were\radded into the concrete wall parts and an enclosed volume was created using those. The interior\rtemperature of the enclosed volume increased using resistance and the temperature was measured with a\rthermocouple as well. In order to calculate the thermal conductivity of heat-insulated walls, measured\rtemperature, power consumption, and surface area were used. As a result, it was shown that the wood\rshavings insulation in concrete had a lower thermal conductivity coefficient as 2,51 W/mK than others and\rmuch efficiency as well. In addition, the uncertainty of the thermal conductivity coefficient was calculated\rapproximately about ± 0,204 for all type of walls. Besides, the presented methodology could help to prevent\rlacking energy resources and to save economical incomes.Öğe Design of Hazelnut Drying System Supported By Solar Energy, Investigation of Drying Performance and Determination of Proper Drying Model(Int Journal Renewable Energy Research, 2020) Acar, Bahadir; Dagdeviren, Abdullah; Ozkaymak, MehmetRapid and efficient drying process for the hazelnuts is required because of the lack of plain areas for solar drying due to the rough landforms in the Black Sea Region, high amount of cloudy days, causing product deteriorations and rots by instantaneous rain transitions and unexpected sudden rains. In this study, a hazelnut drying system supported by solar energy in order to achieve a rapid and efficient drying process was designed and drying performance was examined. In the designed system, a spiral shaft was used for movements of the hazelnuts in the drying chamber. Besides, the inner temperature of the chamber increased with the help of a sun collector. The process control device was used to keep the inner temperature as constant at 40 degrees C. In the experiments, 20kg weight hazelnut husk was used. The experiment was performed between 09:00 and 17:00 hours in a day with normal sunlight conditions and the total drying process took about 8 hours. The moisture ratios (MR) and drying rates (DR) graphics were obtained by scaling weight losses of the hazelnuts in each hour. As a result, it is observed that the 20kg weight of the hazelnuts decreased to the 17.201kg and therewith the total removed moisture from the hazelnuts was about 2.799kg. In the light of the moisture ratios obtained by experiments, 8 different kinetic drying models were performed with MATLAB software. According to the kinetic model results, the lowest reduced chi-square (chi(2)) and root mean square error (RMSE) were about 241x10(-6) and 155x10(-4) respectively. In addition, the coefficient of determination (R-2) was calculated as 0.9982 which is the highest result closest to 1. Among the 8 kinetic models, the Page model is given the best results for the drying process.Öğe Determination freeze-drying characteristics of ottoman strawberries(Gazi Univ, 2023) Acar, Bahadir; Dagdeviren, Abdullah; Yildiz, Busra Meryem; Ozkaymak, MehmetThis study was performed to define the kinetic drying model and to define the effective diffusivity coefficient of the fruit, which is called ottoman strawberries in the literature. In the study, strawberries by the weight of 100 g and with a thickness of 5 mm were placed in the drying device, and the data were processed by observing the weight loss every two hours after being subjected to the drying process for 14 hours. 8 different kinetic drying models were applied to the acquired data using the MATLAB program. As a result of the application, the estimated standard errors (RMSE), chi-square (X2), regression coefficients (R2) were calculated, error analysis was performed, R2, X2, and RMSE values were found, as 9,998x10-1, 6,993x10-5 and 0.7242x10-2. According to these results, the model of strawberry was determined that the most suitable model is the Page model. Also, the effective diffusivity coefficients for ottoman strawberries were calculated as 2.73286 x 10-10 m2/s. It was confirmed that the calculated effective diffusivity value was within the reference range mentioned in the literature (10-12 m2/s - 10-8 m2/s) for food products.Öğe Effect of Al2O3-SiO2/Water Hybrid Nanofluid Filled in a Square Enclosure on the Natural Convective Heat Transfer Characteristics: A Numerical Study(Amer Scientific Publishers, 2022) Dagdeviren, Abdullah; Gedik, Engin; Kecebas, Ali; Pazarlioglu, Hayati Kadir; Arslan, Kamil; Alsabery, Ammar I.In this study, heat transfer enhancement by natural convection Al2O3/water mono and Al2O3-SiO2/water hybrid nanofluid in an enclosure cavity have been performed utilizing the finite element method. For numerical com-putations, the homogeneous nanofluid approach was considered. The cavity was heated from the left vertical wall and cooled from the right vertical wall while the top and bottom walls were taken as adiabatic. The effects of some related factors such as the Rayleigh number (10(3) <= Ra <= 10(6)) and nanoparticles' volume fraction IP: 182.75.148.10 On: Sat, 13 Aug 2022 10:11:41 (0 <= phi <= 0.05) on the heat transfer by natural convction were examined. To discuss fluid characteristics of mono Copyright: American Scientific Publishers and hybrid type nanofluid under natural convecton effect, the obtained results were presented as streamlines Delivered by Ingenta and isotherms. Also, variations of local and average Nusselt numbers were examined in detail. It was obtained that an increase in the nanoparticle volume fraction leads to the enhancement of convective heat transfer for all Rayleigh numbers. It was also indicated that the highest increment in heat transfer by convection occurs in the nanoparticle volume fraction of 2% for Al2O3/water and 4% for Al2O3-SiO2/water. The present study results are also consistent with the literature results.Öğe Effect of magnetic field locations on thermo-magnetic convection performance of Fe3O4/H2O ferrofluid flowing in a novel dimpled tube: An experimental study(Pergamon-Elsevier Science Ltd, 2023) Gursoy, Emrehan; Gurdal, Mehmet; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Tekir, Mutlu; Arslan, Kamil; Gedik, EnginThe aim of this study is to examine the hydrothermal behavior of Fe3O4 Ferrofluid flowing under the effect of uniform magnetic field (0 T <= B <= 0.3 T). In addition, magnetic field locations were changed for each experiment to observe effect of the magnetic field locations (x/D = 20, 40, 60) on the hydrothermal behavior of the proposed system. Fe3O4 Ferrofluid was prepared in phi = 1.0% volume concentration in water and flows under the laminar regime (1131 <= Re <= 2102). Comparisons of the hydrothermal behavior of the novel proposed parameters were performed according to combinations of the different magnetic field locations and magnitudes. It is concluded that the highest Nusselt number was obtained using B = 0.3 T for the magnetic field location of x/D = 20 for both in smooth and dimpled tubes. Compared to B = 0 T, the Nusselt number enhancement was detected by 64.03% for smooth tube for the magnetic field location of x/D = 20 for B = 0.3 T whereas Nusselt number wasaugmented by 45.40% for dimpled tube for the same input parameters. Furthermore, no considerable changes in friction factor was determined under magnetic field effect when the application of magnetic field locations was changed. As a result of these findings, the highest increase in Performance Evaluation Criteria belonging dimpled tube was calculated by 33.54% at Re = 2102 for B = 0.16 T for the magnetic field location of x/D = 20. As a general conclusion, this study can shed light on investigating ferrofluids behavior under magnetic field applied in var-iable magnetic field locations.Öğe Energy analysis of magnetite nanofluid flowing in newly designed sudden expansion tube retrofitted with dimpled fin(Pergamon-Elsevier Science Ltd, 2022) Guersoy, Emrehan; Pazarlioglu, Hayati Kadir; Dagdeviren, Abdullah; Guerdal, Mehmet; Gedik, Engin; Arslan, Kamil; Kurt, HueseyinSudden expansion geometry plays an important role in the design of many engineering applications such as heat exchangers to avoid thermal stress on welded joints. While the heat transfer in these geometries is maximized at the reattachment points, it decreases to a minimum in the recirculation regions created by the fluid. To prevent this situation and improve the performance of the expansion tubes, nanofluid, and expanded surfaces can be used. For this purpose, forced convection of magnetite nanofluid flow in various expansion ratios has been investigated numerically in this study. Analyses have been performed on Reynolds ( Re ) numbers ranging from 100 to 2000, constant and uniform heat flux at 600 W/m(2), and volume concentrations (1.0 <=phi <= 2.0 vol.%). The result showed that while the Nu number increases with increasing Re number , the most efficient case is Dimpled Tube ( DT ) 9, and the highest value of performance evaluation criteria (PEC) has been obtained at phi= 2.0 vol.%. Compared with the water, the highest Nu number value has been obtained as 3.34% increased at Re = 20 0 0 and phi= 2.0 vol.%. When compared to the DT9 and Smooth Tube ( ST ) 1 where water was used as the working fluid at Re = 20 0 0 and phi= 2.0 vol.%, the PEC value increased by 8.66% and 110.31%, respectively. In addition, the bottom wall of the DT9 case performs higher convective heat transfer rate than the top wall.(c) 2022 Elsevier Ltd. All rights reserved.Öğe Experimental and numerical study on ferrohydrodynamic and magneto-convection of Fe3O4/water ferrofluid in a sudden expansion tube with dimpled fins(Elsevier, 2024) Guersoy, Emrehan; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil; Dagdeviren, AbdullahBackground: This study experimentally and numerically addresses magnetohydrodynamic forced convection including dimpled fins, Fe3O4/water ferrofluid, and DC magnetic field. In this research, focusing on the thermohydraulic performance improvement of a sudden expansion tube. It has been used different inlet diameters, dimple sizes, ferro nanoparticle concentrations, and magnetic field strengths to examine the heat transfer and fluid dynamics characteristics of the system. Methods: The study consists of two parts, i) experimental and ii) numerical. Steady-state, incompressible, Newtonian flow were considered but chemical reaction, viscous dissipation, buoyancy, and radiative heat transfer were neglected in this study. On the other hand, numerical solutions were carried out for single-phase method. This study was first compared with the studies in the literature on the flow in a sudden expansion tube without dimpled fins and the error rate was found to be less than 10%. In the analysis, dimpled fins with d=3, 5, and 7 mm at each P=15 mm (P/d=5.0, 3.0, and 2.14) have been used. As working fluid, Fe3O4/water ferrofluid with volume concentration of phi=1.0 % and 2.0% have been analyzed. Additionally, DC magnetic fields, which strength of Ha=0.1, 0.3, 0.5, 1.1, 3.2, and 5.3 (B =0.01, 0.03, 0.05, 0.1, 0.3, and 0.5T), have been applied on the sudden expansion tube surface as external force. Significant findings: Dimpled fins enhance the heat transfer by disrupting the boundary layer and forming secondary flows, while the ferrofluid increases the thermal conductivity and viscosity of the base fluid. Based on these explanations, dimpled fins increased the convective heat transfer rate at the rate of 96.0% compared with smooth tube. In addition, Fe3O4/water ferrofluid with phi=2.0 % performed the highest performance and performance evaluation criteria increased by 8.5%. The magnetic field also contributes to the heat transfer enhancement by inducing Lorentz force and mixing the flow. Excessive increasing of magnetic field strength adversely affected the system performance, and the highest performance evaluation criterion is acquired at Ha=3.2 by increasing 3.9%. Compared with smooth tube, compound effect of dimpled fins, Fe3O4/water ferrofluid, and magnetic field improved the average Nusselt number and performance evaluation criterion at the rate of 279.8 % and 207.9%, respectively.Öğe Experimental Investigation of Freeze-Dried of Kanlica Mushroom (Lactarius Salmoncolor)(Gazi Univ, 2023) Ongun, Goknur Kayatas; Ozkaymak, Mehmet; Acar, Bahadir; Aktas, Mustafa; Dagdeviren, AbdullahIn this study, it is examined to prevent the formation of toxins by providing drying of the kanlica mushroom, which is unique to Karabuk, by freezing, to extend the shelf life, to take measures against early decay and spoilage. As the dried product, kanlica mushroom, which is an endemic plant, contains high amounts of protein and amino acids. In this study, the 5 mm thick cut kanlica mushroom was placed in a freeze-drying device and the drying process was initiated. Weight losses during drying were recorded and kinetic models were created. In the experiment lasting 14 hours in total, 100 gr. The weights of the canlica mushrooms were measured every two hours and MR (Moisture rates) were calculated. According to our results, the lowest chi-square (X-2) was 1.851 x10(-4) and the estimated standard error (RMSE) value was 0.01358. The correlation value (R-2) was calculated as 0.9988, close to one. The best Page model gave these results from the kinetic models. The effective diffusivity for the Kanlica Mushroom with 5 mm thicknesses can be calculated at about 3.2035x10(-10) m(2)/s. It was confirmed that the calculated effective diffusivity value was within the reference range mentioned in the literature (10(-12) m(2)/s - 10(-8) m(2)/s) for food products.Öğe Freeze Drying Process of Kiwi Slices with Various Thicknesses and Investigation Drying Characteristic of Process(Gazi Univ, 2023) Acar, Bahadir; Dagdeviren, Abdullah; Ozkaymak, Mehmet; Guinaleh, Abdillahi RoblehIn the study, the kiwi fruit was sliced into various thicknesses as 5 mm and 7 mm, and those sliced specimens were put in the freeze-drying device. the mass losses of the specimens were measured and saved during the drying process and kinetic drying models were performed using those measurements. The mass losses of each kiwi slices in 100 g mass were measured every two hours in the experiment lasting 14 hours in total and moisture ratios (MR) were calculated as well. Considering the experimental results, 8 different kinetics drying models were performed using MATLAB software. As a result, the lowest reduced chi-square (X-2) values for 5 mm and 7 mm thicknesses were calculated about 8.261x10(-6) and 1.705x10(-5) respectively, the root means square error values (RMSE) were about 0.002865 and 0.004146, respectively. Also, the coefficient of determination (R-2) for both thicknesses was calculated as 0.9999 which was the highest result closest to 1. Among the 8 different kinetic drying models, the Logarithmic model was chosen as a proper kinetic drying model for kiwi products. When the moisture contents and drying rates were considered it was seen that the drying rate of kiwi slices with 7 mm thickness exhibited slow behavior because of the higher moisture content. Besides, it was determined that the effective diffusivity coefficients for specimens with 5 mm and 7 mm thickness were calculated as 2.25 x 10(-10) m(2)/s and 3.28 x 10(-10) m(2)/s respectively.Öğe Freeze- drying of carrot slices in diverse thicknesses(2021) Acar, Bahadır; Dagdeviren, Abdullah; Janaani, Ahmed; Roshanaei, Khandan; TaskeŞen, Edip; Ongun, Göknur K.; Özkaymak, MehmetIn this paper we dried carrots by the method of freeze-drying. The carrots had cut into slices; then\rdivided in halves. The mass looses of samples sized. The mass losses measured and recorded during the\rprocess. The sections were in 5 mm and 7 mm. Slices were dried with SCANVAC COOLSAFE. The masses of\rthe carrot slices differed also in each unit with the same mass and shape varied. Our team did the drying\rprocedures every two hours, also the experiment was applied at different temperatures. While evaluating\rthe number of carrot slices as samples for freeze-dried observed that, dried samples amount were 5\rtimes less than the number of carrots before drying. The procedure was applied to 10 different\rmathematical models using the MATLAB program. The error analysis of the models at the result made by\rusing the root-mean-square error (RMSE), chi-square (X2) and regression coefficients (R2). According to\rthe results, it was sdetermined that the results of the Page model were closer as the experimental results\rbe compared to other models. The statistical error values of samples for R2, RMSE respectively were\r0.018565707 for 5 mm and 0.019532936 for 7 mmÖğe Freeze-drying kinetics and diffusion modeling of hawthorn(Yildiz Technical Univ, 2023) Hagig, Khaled Ali; Acar, Bahadir; Dagdeviren, Abdullah; Taskesen, Edip; Ozkaymak, MehmetThis study tests freeze-drying (FD) technology (Scanvac Coolsafe model, Labogene brand) to preserve hawthorn fruit. First, 100g hawthorn slices were frozen and then freeze-dried. Kinetic models were applied, and hawthorn's moisture ratio and weight loss were noted after every two hours during the 14-hour freeze-drying process. Matlab program is used to perform a total of eight kinetic drying models. Results show that the root mean square error was 0.011063, the highest determination coefficient was 0.9987, the least chi-square was 1.959x10(-4), and the effective diffusivity was 2.33742x10(-1)0m(2)/s. The diffusion approach is the best among the eight models.Öğe Freeze-Drying of Persimmon (Diospyros Kaki) Slices Investigation of Drying Characteristics(Gazi Univ, 2023) Dagdeviren, Abdullah; Acar, Bahadir; Alhammadiy, Abdullatif; Roshanaei, Khandan; Coskun, Tuba; Inanc, Ozgur; Ozkaymak, MehmetThis study was performed to define the kinetic drying model and to define the effective diffusivity coefficient of the fruit, which is called Diospyros kaki in the literature, from the family of Ebonaceae known as the Persimmon in our country. In the study, blueberries by the weight of 100 g and with a thickness of 5 mm were placed in the drying device, and the data were processed by observing the weight loss every two hours after being subjected to the drying process for 14 hours. 8 different kinetic drying models were applied to the acquired data using the Matlab program. As a result of the application, the estimated standard errors (RMSE), chi-square (X-2), regression coefficients (R-2) were calculated, error analysis was performed, R-2, X-2, and RMSE values were found, as 0.019483, 5.062 x 10(-4) and 0.9558. According to these results, it was determined that the most suitable model is the Page model. Also, the effective diffusivity coefficients for Persimmon (Diospyros Kaki) were calculated as 1.79775 x 10(-10) m(2)/s.Öğe Investigation of magneto-convection characteristics in a sudden expanding channel with convex surface geometry under thermally developing flow conditions(Emerald Group Publishing Ltd, 2024) Gursoy, Emrehan; Pazarlioglu, Hayati Kadir; Gurdal, Mehmet; Gedik, Engin; Arslan, Kamil; Dagdeviren, AbdullahPurposeThe purpose of this study is to analyse the magnetic field effect on Fe3O4/H2O Ferrofluid flowing in a sudden expansion tube, which has specific behaviour in terms of rheology, with convex dimple fins. Because the investigation of flow separation is a prominent application in performance, the effect of magnetic field and convex dimple on the thermo-hydraulic performance of sudden expansion tube are examined, in detail.Design/methodology/approachDuring the solution of the boundary conditions of the sudden expansion tube, finite volume method was used. Analyses have been conducted considering the single-phase solution, steady-state, incompressible fluid and no-slip condition of the wall under forced convection conditions. In the analyses, it has been assumed that the flow was developing thermally and has been fully developed hydrodynamically.FindingsThe present study focuses on exploring the influence of the magnetic field, nanofluid concentration and convex dimple fins on the thermo-hydraulic performance of sudden expansion tube. The results indicate that the strength of the magnetic field, nanofluid concentration and convex dimple fins have a positive effect on the convective heat transfer in the system.Originality/valueThe authors conducted numerical studies, determining through a literature search that no one had yet investigated enhancing heat transfer on a sudden expansion tube using combinations of magnetic fields, nanofluids and convex dimple fins. The results of the numerical analyses provide valuable information about the improvement of heat transfer and system performance in electronic device cooling and heat exchangers.Öğe Kinetic Model And Effective Diffusivity Of Frozen-Dryed European Blueberry (Vaccinium Myrtillus)(Gazi Univ, 2022) Ayriksa, Mutlucan; Acar, Bahadir; Dagdeviren, Abdullah; Roshanaei, Khandan; Coskun, Tuba; Ongun, Goknur K.; Ozkaymak, MehmetIn current study, the freeze-drying (FD) method has been investigated. This method is the healthiest drying method that used in recent years by extending the shelf life of the products and preserving the beneficial flavors in its content. Antioxidant, antimicrobial, antidiabetic, anti-inflammatory, antiseptic, etc., are the most emphasized role among the berries. Thus, blueberry is one of the great aspects to be a case for drying. Blueberry (Vaccinium Myrtillus), which is an opulent source of many phenolic compounds with known properties, has been determined. In the study, blueberries by the weight of 100 g and with a thickness of 5 mm were placed in the drying device, and the data were processed by observing the weight loss every two hours after being subjected to the drying process for 14 hours. 8 different kinetic drying models were applied to the acquired data using the Matlab program. As a result of the application, the estimated standard errors (RMSE), chi-square (X-2), regression coefficients (R-2) were calculated, error analysis was performed, R-2, X-2, and RMSE values were found, as 1.4686 x 10(-2), 2.875 x 10(-4) and 9.978 x 10(-1). According to these results, it was determined that the most suitable model is the Page model. Also, the effective diffusivity coefficients for blueberries were calculated as 2.57665 x 10(-12) m(2)/s.
