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Öğe Design of air cooling unit with PCM(Institute of Physics Publishing, 2019) Susantez C.; Akyol E.; Hacihafizo?lu O.; Akyol U.In this paper a heat absorption unit has been designed to cool the entering hot air. For this aim, five slabs of PCM (Phase change material) have been used inside the cooling unit. The velocity and temperature values of entering hot air respectively are 0.1 m/s and 50 C. Three different cases for PCM design were investigated: in the first case RT 44HC, RT 35HC, RT 31, RT 28HC and RT 25HC as phase change materials were used in such a way that the PCM with higher number gets contact with the hot air first. In the second and third cases only one PCM type were used for the five slabs inside the cooling unit. They are RT 44HC and RT 25HC. Analysis performed for 10h. Results show that although maximum heat absorbed for the first 8h is in the case of only RT 25HC used in the cooling system, after 8h the cooling unit with mixed PCM shows a better performance and minimum exit air temperature has been observed for this case at the end of 10h. © Published under licence by IOP Publishing Ltd.Öğe Effect of drying air pressure on wool bobbin drying process(2011) Akyol E.; Akyol U.; Hacihafizoglu O.; Kahvecd K.; Cdhan A.Inevitable after most dyeing or/and finishing processes, drying is a time consuming, energy intensive and expensive process and constitutes one of the major cost elements among the textile finishing operations. The drying behavior of wool based yarn bobbins for different drying air pressures at a constant drying air temperature was simulated by empirical and semi-empirical drying models available in the literature. For this purpose, firstly, experimental drying behavior of wool bobbins was determined on an experimental bobbin dryer setup which was designed and manufactured based on hot-air bobbin dryers used in textile industry. Then, drying models considered were fitted to the experimental data. The fit was performed by selecting the values for constants in the models in such a way that these values make the sum of the squared differences between the experimental and the model results for moisture ratio minimum. Suitability of fitting was specified as comparing the correlation coefficient, standard error and mean square deviation. The results show that the most appropriate model in describing the drying curves of wool based yarn bobbins is the Logarithmic model. The results also show that the drying air pressure has a significant effect on drying.Öğe Investigation of the effect of drying air temperature on drying time by numerical method for textile bobbins(Institute of Physics Publishing, 2019) Akyol U.; Karakoca A.; Shaliyev R.; Akal D.; Uzuneanu K.Drying of the yarn bobbins in the textile sector is a very important stage among the textile finishing processes. Because this process takes a lot of time and causes a large amount of energy consumption. In this study, drying times for different drying air inlet temperatures at a constant drying air pressure were determined with the help of mathematical model for textile bobbin drying process. Finite difference method was used in mathematical model solution and the effect of different space and time steps were taken into consideration during the solution. © Published under licence by IOP Publishing Ltd.Öğe Optimum operating conditions in drying of polyester based yarn bobbins with a pressurized hot air dryer(2011) Cihan A.; Kahveci K.; Akyol U.; Akal D.In this study, optimum operating conditions in drying of polyester based yarn bobbins witha pressurized hot air dryer has been investigated experimentally. For this purpose, experimental drying behaviour of bobbins was determined by an experimental dryer which was designed and anufactured based on hot-air bobbin dryers used in the textile industry. Drying parameters were drying temperature, drying pressure and volumetric flow rate of drying air. Optimum operating conditions were considered with respect to the drying time and energy consumption. The results show that totaldrying 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.Öğe A review of new technologies in valve systems of internal combustion engines and their effects(Institute of Physics Publishing, 2019) Akal D.; Akyol U.; Uzuneanu K.Efficient use of energy is becoming increasingly crucial due to global warming and depleting fossil fuel sources. Automotive manufacturers aim for fuel economy, reduction of exhaust emissions, durability, volume and weight reduction, and power and torque increase in internal combustion engines. One of the most important developments in this field is the new technologies in classic valve systems. There are still ongoing studies in this field as the gas exchange processes affects all engine parameters. In this review; the principles of new technologies used on classic valve systems and their effects on engines have been investigated. The research has shown; new mechanism technologies used on valve systems have positive effects on engine performance, power, torque and fuel consumption. © Published under licence by IOP Publishing Ltd.Öğe A software for calculation of optimum conditions for cotton bobbin drying in a hot-air bobbin dryer(2011) Kuscu H.; Cihan A.; Kahveci K.; Akyol U.In this study, a software has been developed to predict the optimum conditions for drying of cotton based yarn bobbins in a hot air dryer. For this purpose, firstly, a suitable drying model has been specified using experimental drying behavior for different values of drying parameters. Drying parameters in the experiments were drying temperature, drying pressure, and volumetric flow rate of drying air. After obtaining a suitable drying model, additional curve fittings have been performed to obtain equations for drying time and energy consumption taking into account the effects of drying parameters. Then, a software has been developed using Visual Basic programming language to predict the optimum drying conditions for drying time and energy consumption.Öğe A software for calculation of optimum conditions for cotton, viscose, polyester and wool based yarn bobbins in a hot-air bobbin dryer(2012) Kuşçu H.; Kahveci K.; Akyol U.; Cihan A.In this study, a software has been developed to predict the optimum drying conditions of viscose, wool, polyester and cotton based yarn bobbins for drying in a pressurized hot air dryer. For this purpose, firstly, a suitable drying model has been found in defining the drying behavior of bobbins using the experimental drying behavior. After that, additional regression analyses have been made to take into account the effect of the drying parameters on drying. Then, a software has been developed using Visual Basic programming language. With the aid of this software, optimum drying conditions for drying time and energy consumption can be obtained for the cotton, viscose, polyester and wool based yarn bobbins.Öğe A software for calculation of optimum conditions for viscose based bobbin drying in a hot-air bobbin dryer(2011) Kuşçu H.; Kahveci K.; Akyol U.; Cihan A.In this study, a software has been developed to predict the optimum drying conditions of viscose based yarn bobbins for drying in a pressurised hot air dryer. For this purpose, firstly, a suitable drying model has been found in defining the drying behaviour of bobbins using the experimental drying behaviour. After that, additional regression analyses have been made to take into account the effect of drying parameters on drying. Then, a software has been developed using Visual Basic programming language. With the aid of this software, optimum drying conditions for drying time and energy consumption can be obtained.Öğe Thermal performance analysis of a tube finned surface(2002) Bilen K.; Akyol U.; Yapici S.The present work submits an experimental work on the heat transfer and friction loss characteristic, employing a tube finned heating surface kept at a constant temperature in a rectangular channel. The tube fins attached on the surface (o.d. = 29 mm) were arranged as either in-line or staggered. The parameters for the study were Reynolds number (3700-30 000), depending on hydraulic diameter, the distance between the tube fins in the flow direction (Sy/D = 1.72-3.45) and the fin arrangement. The change in the Nusselt number with these parameters was determined. For both tube fin arrangements, it was observed that increasing Reynolds number increased Nusselt number, and maximum heat transfer occured at Sy/D = 2.59. Thermal performances for both arrangements were also determined and compared with respect to heat transfer from the same surface without fins. With staggered array, a heat transfer enhancement up to 25 per cent for Sy/D = 3.45 in staggered array was achieved in constant pumping power. Copyright © 2002 John Wiley & Sons, Ltd.
