The Experts below are selected from a list of 3867 Experts worldwide ranked by ideXlab platform
Atsuhiko Yamanaka - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Loss and Bobbin Material in Double Pancake AC Superconducting Coils
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: Tomoaki Takao, S Fukui, Takayuki Goto, Orie Sakamoto, K. Nishimura, T. Takagi, S. Sakai, Atsuhiko YamanakaAbstract:We fabricated nonimpregnated HTS superconducting coils with a BSCCO tape. Bobbin materials in the coils are a Dyneema(R) fiber reinforced plastic (DFRP) and a glass fiber reinforced plastic (GFRP). We excited those coils with ac currents, and estimated mechanical losses. According to the measured data, the mechanical loss decreased with increase of winding tension of the coils, because strong winding tension fixed the coils tightly. Also, the mechanical loss occurred in the DFRP coil was smaller than that occurred in the GFRP coil. A thermal expansion coefficient of the DFRP is a negative value, that is, the DFRP expands with cooling down from room temperature to cryogenic temperature. The expansion of the DFRP bobbin made the winding of the coil fix tightly, and the mechanical loss decreased. From those experimental results, we think that the DFRP bobbin is useful for decreasing of mechanical losses of the ac coils.
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High Thermal Conduction Bobbin and Thermal Stability of Conduction Cooled Superconducting Pancake Coils
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: Tomoaki Takao, Shunsuke Asano, Kohei Ishikawa, Yuzuru Kawahara, Orie Sakamoto, Arata Nishimura, Atsuhiko YamanakaAbstract:We have proposed a Dyneema fiber reinforced plastic (DFRP) as a coil bobbin material. The DFRP has some properties such as high thermal conduction, easy mechanical processing, and expansion with cool down. We fabricated superconducting coils having an YBCO tape, cooled the coils with a refrigerator, and supplied a dc current to the conduction cooled coils. Thermal stability of the coils was also estimated. The DFRPs, glass fiber reinforced plastics, and AlN blocks were used as the bobbin materials for the coils. From the experimental results, the thermal stability of the coils increased with increasing of the winding tension of the coils, and the coil having the DFRP bobbin showed better performance than the coils with the glass fiber reinforced plastic and the AlN Bobbins. We think that contact force between the superconducting tape and the bobbin became large due to the thermal expansion of the DFRP bobbin. These results showed that DFRP can represent a viable opportunity as bobbin material for conduction cooled high-temperature superconducting coils.
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Increase of Cooling Performance of Conduction Cooled Superconducting Coils Using High Thermal Conduction Plastic
IEEE Transactions on Applied Superconductivity, 2012Co-Authors: Tomoaki Takao, Atsuhiko Yamanaka, Takayuki Goto, Daigo Hachisuka, Syunsuke Asano, Takuro Yuhara, Arata NishimuraAbstract:We experimentally study thermal stability of conduction cooled superconducting coils from a viewpoint of structural materials of the coils. The materials are Dyneema fiber reinforced plastics (DFRPs). The DFRP has properties of high thermal conduction and negative thermal expansion. We evaluated the stability of the conduction cooled coils having DFRP Bobbins with changing the DFRP's thermal expansion. According to the experimental results, when the expansion became large, the stability also became better. It is expected that the DFRP is the effective heat sink bobbin material.
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Mechanical Loss and Bobbin Materials in AC Superconducting Coil Under AC Magnetic Field
IEEE Transactions on Applied Superconductivity, 2011Co-Authors: Tomoaki Takao, S Fukui, Takayuki Goto, Tomoaki Masuda, K. Nishimura, T. Takagi, Atsuhiko YamanakaAbstract:We made small superconducting coils and measured the total AC loss under the AC and DC external magnetic fields. The coil winding conditions are that 1, 5, and 10 N of the winding tensions and bobbin materials are glass fiber reinforced plastic (GFRP) and Dyneema fiber reinforced plastic (DFRP). The GFRP and the DFRP have thermal strain properties of contraction and expansion respectively with cooldown to cryogenic temperature. Mechanical losses were estimated from the measured data. According to the estimated mechanical losses, the loss of the coil whose bobbin material is the DFRP was small because the DFRP bobbin expanded and hence the winding was tightly fixed. Approximate 10 to 13% of the AC loss can be reduced by only changing the bobbin material from the GFRP to the DFRP.
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Evaluating Cooling Performance of High-Thermal-Conduction Composite in Conduction-Cooled Superconducting Coils
IEEE Transactions on Applied Superconductivity, 2010Co-Authors: Tomoaki Takao, Takayuki Goto, Takuroh Yuhara, Ryo Sakuma, Atsuhiko YamanakaAbstract:Aluminum nitride (AlN) has been widely used as a heat sink material in conduction-cooled superconducting coils but is hard to process. We have therefore developed an easily processed Dyneema-fiber-reinforced plastic (DFRP) with high thermal conductivity. Making small superconducting coils with DFRP or AlN Bobbins, cooling them to a cryogenic temperature by using a refrigerator, and comparing their voltage profiles when DC currents were applied to them, we found the heat-sink effect of DFRP to be almost same as that of AlN because DFRP has a high thermal conductivity and expands when cooled. This expansion increases the contact force between superconducting windings and the DFRP bobbin and thereby improves the transfer of heat from the winding to the DFRP. We think DFRP will be the next-generation heat-sink material.
Ahmet Cihan - One of the best experts on this subject based on the ideXlab platform.
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drying kinetics of cotton based yarn Bobbins in a pressurized hot air convective dryer
Proceedings of the Institution of Mechanical Engineers Part E: Journal of Process Mechanical Engineering, 2017Co-Authors: Dinçer Akal, Ugur Akyol, Kamil Kahveci, Ahmet CihanAbstract: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...
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A model for predicting drying time period of wool yarn Bobbins using computational intelligence techniques
Textile Research Journal, 2015Co-Authors: Ugur Akyol, Pınar Tüfekci, Kamil Kahveci, Ahmet CihanAbstract: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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A model for predicting drying time period of wool yarn Bobbins using computational intelligence techniques
Textile Research Journal, 2014Co-Authors: Ugur Akyol, Pınar Tüfekci, Kamil Kahveci, Ahmet CihanAbstract: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,...
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A Software for Calculation of Optimum Conditions for Cotton Bobbin Drying in a Hot-Air Bobbin Dryer
World Academy of Science Engineering and Technology International Journal of Mechanical Aerospace Industrial Mechatronic and Manufacturing Engineering, 2011Co-Authors: Hilmi Kuscu, Ahmet Cihan, Kamil Kahveci, Ugur AkyolAbstract: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. Keywords—Drying, bobbin, cotton, PLC control, Visual Basic.
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Simulation of Drying Behavior of Cotton Bobbins by a Simultaneous Heat and Mass Transfer Model
Defect and Diffusion Forum, 2011Co-Authors: Ugur Akyol, Kamil Kahveci, Ahmet Cihan, Dinçer AkalAbstract: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.
Ugur Akyol - One of the best experts on this subject based on the ideXlab platform.
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drying kinetics of cotton based yarn Bobbins in a pressurized hot air convective dryer
Proceedings of the Institution of Mechanical Engineers Part E: Journal of Process Mechanical Engineering, 2017Co-Authors: Dinçer Akal, Ugur Akyol, Kamil Kahveci, Ahmet CihanAbstract: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...
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A model for predicting drying time period of wool yarn Bobbins using computational intelligence techniques
Textile Research Journal, 2015Co-Authors: Ugur Akyol, Pınar Tüfekci, Kamil Kahveci, Ahmet CihanAbstract: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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A model for predicting drying time period of wool yarn Bobbins using computational intelligence techniques
Textile Research Journal, 2014Co-Authors: Ugur Akyol, Pınar Tüfekci, Kamil Kahveci, Ahmet CihanAbstract: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,...
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A Software for Calculation of Optimum Conditions for Cotton Bobbin Drying in a Hot-Air Bobbin Dryer
World Academy of Science Engineering and Technology International Journal of Mechanical Aerospace Industrial Mechatronic and Manufacturing Engineering, 2011Co-Authors: Hilmi Kuscu, Ahmet Cihan, Kamil Kahveci, Ugur AkyolAbstract: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. Keywords—Drying, bobbin, cotton, PLC control, Visual Basic.
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Simulation of Drying Behavior of Cotton Bobbins by a Simultaneous Heat and Mass Transfer Model
Defect and Diffusion Forum, 2011Co-Authors: Ugur Akyol, Kamil Kahveci, Ahmet Cihan, Dinçer AkalAbstract: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.
A. Yamanaka - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Loss of HTS Coils Reinforced With Negative Thermal Expansion Fiber Materials
IEEE Transactions on Applied Superconductivity, 2006Co-Authors: M. Furuse, T. Takao, M. Umeda, Y. Fukasawa, S. Minowa, T. Iwamura, H. Sato, T. Asano, A. YamanakaAbstract:High-Tc superconducting (HTS) coils with various types of reinforcement are investigated with respect to the reduction of mechanical loss. The total AC loss of the coils is measured under an external DC magnetic field at liquid nitrogen temperature, the reduction of the mechanical loss components are estimated. Tensioned stainless-steel tape is found to be the most effective for reducing the mechanical loss by improving the rigidity of the entire winding. The mechanical loss of the HTS coils is reduced by reinforcement with a bobbin of negative thermal expansion material, although the hoop stress caused by radial expansion of the bobbin is absorbed by a small number of winding turns. Bobbins of negative thermal expansion material are therefore unsuitable for pancake-type coils or multilayer windings, but can be expected to realize substantial reductions in mechanical loss for single-layer windings or thin solenoids
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Quench Characteristics in Superconducting coils fabricated by various FRP Bobbins
IEEE Transactions on Applied Superconductivity, 2005Co-Authors: N. Sekine, S. Tada, T. Higuchi, T. Takao, Y. Furumura, A. YamanakaAbstract:In coils using low temperature superconductor, a wire motion due to an electromagnetic force observably reduces stability. It is quite important to prevent the wire motion under a DC operation. We aim to improve stability by means of an intensification of a winding tension at cryogenic temperature. The technique is the use of the Bobbins whose thermal expansion coefficients are negative. For experiments, superconducting coils were fabricated with various conditions; materials of Bobbins, thermal expansion properties, and winding tensions at room temperature. And quench characteristics were measured under the DC operation. Applying a standard deviation of quench currents, we discussed about the relation between fluctuation and the amplitude of the quench currents. In the results, stable quench characteristics were obtained in the coils which were not extremely contracted in the direction of the circumference.
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Reduction of mechanical losses by use of ZFRP Bobbins in AC superconducting coils
IEEE Transactions on Applied Superconductivity, 2004Co-Authors: N. Sekine, S. Tada, T. Higuchi, T. Takao, A. YamanakaAbstract:We have studied a technique to reduce mechanical losses under AC operation by use of a particular bobbin's material as a superconducting coil. The material is a Zylon fiber reinforced plastic (ZFRP). From a viewpoint of mechanical loss reduction, a winding tension at coil-operating temperature is an important element. Since the ZFRP bobbin makes the control of the tension possible, the losses of the coils having the ZFRP Bobbins can also be controlled. To investigate the effect of the loss reduction, 9 sample coils whose winding tensions at cryogenic temperature are different from each other, are prepared. The results of the experiment show that the coils whose winding tensions at cryogenic temperature are strong make the reduction of mechanical losses possible. On the contrary, the mechanical losses are significantly greater in the coils having weak tensions. This paper reports that the ZFRP is effective as the superconducting coil's bobbin.
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Influence of mechanical losses in AC superconducting coils having composite materials reinforced with Dyneema and glass fibers
IEEE Transactions on Applied Superconductivity, 2004Co-Authors: N. Sekine, S. Tada, T. Higuchi, T. Takao, A. Yamanaka, S. FukuiAbstract:When a Dyneema fiber reinforced plastic (DFRP) is used as a superconducting coil's bobbin, the decrease of the winding tension during cooling down is prevented. Therefore, it is expected that a mechanical loss generated in AC superconducting coils is reduced. The DFRP has the high Young's modulus to the fiber direction, however the modulus to the perpendicular direction is lower than the modulus of the glass fiber reinforced plastic (GFRP), which is generally used as a structural material in superconducting coils. Therefore, a Dyneema and glass fiber reinforced plastic (DGFRP), which was compounded the Dyneema and the glass fibers, was fabricated for the purpose of the intensification of the DFRP, and total losses of the superconducting coils having some kinds of DGFRP Bobbins were measured under AC operation. In loss measurements, the coil whose loss was the smallest was the coil having the strongest winding tension at cryogenic temperature, and the coil whose loss was the largest was the coil having the weakest tension. Moreover, comparing with the results of the loss measurement in the coils fabricated with the DFRP bobbin, the losses of the coils having the DGFRP Bobbins were slightly large due to the mixture of the Dyneema and the glass fibers. This paper reports the effect of the reduction of the mechanical losses in the coils having the DGFRP Bobbins and the comparison with the coils whose Bobbins are the DFRP and the GFRP.
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Relation between frictional loss and combination of thermal coefficient of Bobbins and winding tension in AC superconducting coils
IEEE Transactions on Applied Superconductivity, 2003Co-Authors: N. Sekine, Masakatsu Takeo, S. Tada, T. Higuchi, T. Takao, A. Yamanaka, Y Kojo, Y Yamaguchi, S Sato, S. FukuiAbstract:Frictional losses in windings are one of the loss types in AC superconducting coils. When an AC current is supplied to the coil, a superconducting wire in the winding start to vibrate. And frictional heat generates at contact segments between the wire and a coil bobbin. And hence, the losses are not electromagnetic losses such as coupling losses but mechanical losses in superconducting coils. We prepared four types of bobbin materials. Two Bobbins expanded during a cooling process from room temperature to liquid helium temperature. The other two Bobbins contracted during the cooling down. Winding tensions for the four kinds of coils were 0.5, 3.5, and 5.0 N. And then, the AC losses of the twelve coils were measured. When the coils whose Bobbins have thermal expansion were used, the AC losses increased with the gain of the winding tensions, in spite that the experimental conditions such as coil currents and background magnetic field were same. On the contrary, in case of the contraction Bobbins coils were used, the losses decreased with the tensions increased. To analyze the experimental cases of the winding tensions of the sample coils at the liquid helium temperature were calculated, and the relation between the tensions at the cryogenic temperature and the frictional losses was discussed.
Tomoaki Takao - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Loss and Bobbin Material in Double Pancake AC Superconducting Coils
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: Tomoaki Takao, S Fukui, Takayuki Goto, Orie Sakamoto, K. Nishimura, T. Takagi, S. Sakai, Atsuhiko YamanakaAbstract:We fabricated nonimpregnated HTS superconducting coils with a BSCCO tape. Bobbin materials in the coils are a Dyneema(R) fiber reinforced plastic (DFRP) and a glass fiber reinforced plastic (GFRP). We excited those coils with ac currents, and estimated mechanical losses. According to the measured data, the mechanical loss decreased with increase of winding tension of the coils, because strong winding tension fixed the coils tightly. Also, the mechanical loss occurred in the DFRP coil was smaller than that occurred in the GFRP coil. A thermal expansion coefficient of the DFRP is a negative value, that is, the DFRP expands with cooling down from room temperature to cryogenic temperature. The expansion of the DFRP bobbin made the winding of the coil fix tightly, and the mechanical loss decreased. From those experimental results, we think that the DFRP bobbin is useful for decreasing of mechanical losses of the ac coils.
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High Thermal Conduction Bobbin and Thermal Stability of Conduction Cooled Superconducting Pancake Coils
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: Tomoaki Takao, Shunsuke Asano, Kohei Ishikawa, Yuzuru Kawahara, Orie Sakamoto, Arata Nishimura, Atsuhiko YamanakaAbstract:We have proposed a Dyneema fiber reinforced plastic (DFRP) as a coil bobbin material. The DFRP has some properties such as high thermal conduction, easy mechanical processing, and expansion with cool down. We fabricated superconducting coils having an YBCO tape, cooled the coils with a refrigerator, and supplied a dc current to the conduction cooled coils. Thermal stability of the coils was also estimated. The DFRPs, glass fiber reinforced plastics, and AlN blocks were used as the bobbin materials for the coils. From the experimental results, the thermal stability of the coils increased with increasing of the winding tension of the coils, and the coil having the DFRP bobbin showed better performance than the coils with the glass fiber reinforced plastic and the AlN Bobbins. We think that contact force between the superconducting tape and the bobbin became large due to the thermal expansion of the DFRP bobbin. These results showed that DFRP can represent a viable opportunity as bobbin material for conduction cooled high-temperature superconducting coils.
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Increase of Cooling Performance of Conduction Cooled Superconducting Coils Using High Thermal Conduction Plastic
IEEE Transactions on Applied Superconductivity, 2012Co-Authors: Tomoaki Takao, Atsuhiko Yamanaka, Takayuki Goto, Daigo Hachisuka, Syunsuke Asano, Takuro Yuhara, Arata NishimuraAbstract:We experimentally study thermal stability of conduction cooled superconducting coils from a viewpoint of structural materials of the coils. The materials are Dyneema fiber reinforced plastics (DFRPs). The DFRP has properties of high thermal conduction and negative thermal expansion. We evaluated the stability of the conduction cooled coils having DFRP Bobbins with changing the DFRP's thermal expansion. According to the experimental results, when the expansion became large, the stability also became better. It is expected that the DFRP is the effective heat sink bobbin material.
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Mechanical Loss and Bobbin Materials in AC Superconducting Coil Under AC Magnetic Field
IEEE Transactions on Applied Superconductivity, 2011Co-Authors: Tomoaki Takao, S Fukui, Takayuki Goto, Tomoaki Masuda, K. Nishimura, T. Takagi, Atsuhiko YamanakaAbstract:We made small superconducting coils and measured the total AC loss under the AC and DC external magnetic fields. The coil winding conditions are that 1, 5, and 10 N of the winding tensions and bobbin materials are glass fiber reinforced plastic (GFRP) and Dyneema fiber reinforced plastic (DFRP). The GFRP and the DFRP have thermal strain properties of contraction and expansion respectively with cooldown to cryogenic temperature. Mechanical losses were estimated from the measured data. According to the estimated mechanical losses, the loss of the coil whose bobbin material is the DFRP was small because the DFRP bobbin expanded and hence the winding was tightly fixed. Approximate 10 to 13% of the AC loss can be reduced by only changing the bobbin material from the GFRP to the DFRP.
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Evaluating Cooling Performance of High-Thermal-Conduction Composite in Conduction-Cooled Superconducting Coils
IEEE Transactions on Applied Superconductivity, 2010Co-Authors: Tomoaki Takao, Takayuki Goto, Takuroh Yuhara, Ryo Sakuma, Atsuhiko YamanakaAbstract:Aluminum nitride (AlN) has been widely used as a heat sink material in conduction-cooled superconducting coils but is hard to process. We have therefore developed an easily processed Dyneema-fiber-reinforced plastic (DFRP) with high thermal conductivity. Making small superconducting coils with DFRP or AlN Bobbins, cooling them to a cryogenic temperature by using a refrigerator, and comparing their voltage profiles when DC currents were applied to them, we found the heat-sink effect of DFRP to be almost same as that of AlN because DFRP has a high thermal conductivity and expands when cooled. This expansion increases the contact force between superconducting windings and the DFRP bobbin and thereby improves the transfer of heat from the winding to the DFRP. We think DFRP will be the next-generation heat-sink material.
