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      • KCI등재

        Method applied to evaluate heat leakage of cryogenic vessel for liquid hydrogen

        Zhengqing Li,Shengsheng Yang,Xiaojun Wang,Yafei Yuan 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.1

        Cryogenic vessels are special equipment that requires periodic evaluation of their thermal insulation performance. At the currentstandard, the test is considered as the loss product or heat leakage of cryogenic vessel, which takes over 72 h to evaluate;consequently, a large amount of working medium is discharged to the environment in the process. However, hydrogen is flammableand explosive, and the discharged gas may be dangerous. If liquid hydrogen is replaced with liquid nitrogen before testing, theoperation then becomes complicated, and the loss product or heat leakage cannot respond to the thermal insulation performance ofcryogenic vessels for liquid hydrogen. Therefore, a novel method is proposed to evaluate the heat leakage of cryogenic vessels forliquid hydrogen in self-pressurization. In contrast to the current testing methods, the method proposed in this study does not requiredischarge or exchange of working medium in all test processes. The proposed method is based on one-dimensional heat transferanalysis of cryogenic vessels, which is verified by experiment. When this method is used to predict the heat leakage, the comparisonwith the experimental data of the standard method shows that the maximum error of heat leakage is less than 5.0%.

      • KCI등재

        Application of magnetic activated sludge process for a milking parlor wastewater treatment with nitrogen and phosphorus recovery

        Toshihito Onodera,Yasuzo Sakai,Masaru Kashiwazaki,Ikko Ihara,Saha Mihir Lal 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        Milking parlor wastewater contains high concentration suspended solid (SS), nitrogen, and/or phosphate as well as organiccompounds. A new biological wastewater process by magnetic separation, magnetic activated sludge (MAS) process, was appliedto milking parlor wastewater treatment process. A three step wastewater treatment process of coagulation sedimentation / ammoniastripping (C/S), magnetic activated sludge process and contact oxidation (CO) was proposed for removal of these pollutants. Firststep, C/S process recovered 96% TN and 96% PO43-P as resource for fertilizer from the wastewater. 81% biochemical oxygendemand (BOD) in wastewater was removed after MAS process. As a results, all pollutant concentrations satisfied Japanese effluentstandards. Most of residual BOD and SS were removed by the CO process. It was estimated that the proposed process could reducethe process space to 1/7.

      • KCI등재

        Study of Micro-plastics Separation from Sea Water with Electro-Magnetic Force

        Naoki Nomura,Fumihito Mishima,Shigehiro Nishijim 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        The method of removing micro-plastics from sea water has been developed using electro-magnetic force. Plastics are difficult todecompose and put a great load on the marine environment. Especially a plastic with a size of 5 mm or less is defined asmicro-plastic and are carried by ocean currents over long distances, causing global pollution. These are not easily decomposed inthe natural environment. The Lorentz force was generated in simulated sea water and its reaction force was applied to themicro-plastic to control their motion. Lorentz force was generated downward and the reaction force to the plastics was upward. Theplastic used in the experiment was polystyrene with a diameter of 6 mm, and the density was 1.07 g/cm3. The polystyrene spherelevitated at the current density of 0.83 A/cm2and the external field of 0.87T. The particle trajectory calculation was also made todesign separation system using superconducting magnet.

      • KCI등재

        Treatment of milking parlor wastewater containing tetracycline by magnetic activated sludge and contact oxidation process

        Gaowa,Yasuzo Sakai,Xiaonan Xie,Mihir Lal Saha,Ikko Ihara 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        Milking parlor wastewater contains not only high concentrations of organic compounds, but often animal antibiotics. Todischarge the antibiotics to public water area cause problem of antibiotics resistant bacteria. Magnetic separation was applied intoimprovement of milking parlor wastewater treatment process. A new process, composed of a magnetic activated sludge (MAS)process and a contact oxidation (CO) process, was proposed in this study. This process was evaluated by the simulated milkingparlor wastewater (4500 mg/L CODCr and 10 mg/L tetracycline) using a bench scale experimental setup. As a result, the processwas able to removed 97% CODCr as well as 94% tetracycline. The MLVSS (mixed liquor volatile suspended solids) concentrationof MAS was maintained at 12000 mg/L without excess sludge drawing. This process was considered to be useful as treatmentprocess for milking parlor wastewater in which waste-milk including antibiotics is often discharged.

      • KCI등재

        Metallization and superconductivity of hydrides under high pressure

        김덕영 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        Hydrogen, the lightest and the most abundant element in the universe becomes a mainstay of contemporary condensed matterphysics, which is largely because its metallization is regarded as the holy grail of high-pressure physics and it is also due to recentobservations of high Tc superconductivity in hydrogen-dense compounds at extremely high pressure. Contemporary statichigh-pressure technique is not enough to realize the metallization of solid hydrogen and hydrogen-dense compounds maysignificantly reduce the required transition pressure providing an excellent proxy study. In this brief review, I will introduce recentachievements of high-pressure study in solid hydrogen and hydrides.

      • KCI등재

        Feasible waste liquid treatment from electroless nickel-plating by intense magnetic field of HTS bulk magnets

        T. Oka,M. Furusawa,K. Sudo,L. Dadiel,N. Sakai,H. Seki,M. Miryala,M. Murakami,T. Nakano,M. Ooizumi,K. Yokoyama,M. Tsujimura 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        Nickel (Ni) is a kind of the rare earth resources. Since Ni-containing waste is drained after several plating operations in thefactories, the effective recycling technique has been expected to be introduced. An actual magnetic separation technique using HTSbulk magnet generating the strong magnetic field has succeeded in collecting the paramagnetic slurry containing Ni-sulphate coarsecrystals which were fabricated from the Ni-plating waste. The Ni compound in the collected slurry was identified as NiSO4/6H2O,showing slight differences in the particle size and magnetic susceptibility between the samples attracted and not-attract to themagnetic pole. This preferential extraction suggests us a novel recycling method of Ni resource because the compound is capable ofrecycling back to the plating processes as a raw material.

      • KCI등재

        Transient Cooling Operation of Multistage Thermoelectric Cooler (TEC)

        Jiho Park,정상권 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        A thermoelectric cooler (TEC) is promising as an alternative refrigeration technology for the sake of its inherent advantages;no-moving parts and refrigerant-free in its operation. Due to the compactness, reliability and excellence in temperature stability,TECs have been widely used for small cooling devices. In recent years, thermoelectric devices have been attractive technologiesthat not only serve the needs of cooling and heating applications but also meet the demand for energy by recycling waste heat. Inthis research paper, multistage TEC is proposed as a concept of demonstrating the idea of transient cooling technology. The keyidea of transient cooling is to harnesses the thermal mass installed at the interfacial level of the stages. By storing heat temporally atthe thermal mass, the multistage TEC can readily reach lower temperatures than that by a steady-state operation. The multistageTEC consists of four different sizes of thermoelectric modules and they are operated with an optimized current. Once the cold-partof the uppermost stage is reached at the no-load temperature, the current is successively supplied to the lower stages with a certaintime interval; 25, 50 and 75 seconds. The results show the temperatures that can be ultimately reached at the cold-side of thelowermost stage are 197, 182 and 237 K, respectively. It can be concluded that the timing or total amount of the current fed to eachthermoelectric module is the key parameter to determine the no-load temperature.

      • KCI등재

        Numerical investigations on the effect of tortuosity on friction factor in superconducting CICC configuration

        Hitensinh Vaghela,Vikas Lakhera,Kunal Bhatt,Biswanath Sarkar 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.4

        The Cable in Conduit Conductor (CICC) configurations are designed, tested and realized to make high field superconducting(SC) magnets. The evolution of CICC design makes it challenging to forecast thermo-hydraulic behavior. A common objective ofthermo-hydraulic studies is to obtain the most reliable predictive correlation for friction factor in CICC geometries and to reducethe dependency on the experiment. So far, only the void fraction and Reynolds number have been considered in the predictivecorrelations in an explicit way. In the present paper, the CICC twisting pattern dependency, called tortuosity ( ), on the pressuredrop prediction, has been assessed through a numerical simulation approach. The CICC twisting pattern with 6+1 petals (solidconductor in the present study) with different twisting pitches is mimicked in the numerical simulation for the range 100 ≤ Re≤10000 and 1 < < 1.08 and a correlation for friction factor, f, has been proposed as a function of Re and .

      • KCI등재

        Dependence of superconductivity on the crystallinity of Nb films on Si wafers

        Joonyoung Choi,Chang-Duk Kim,Younjung Jo 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.4

        Among elemental metals, niobium (Nb) has the highest superconducting transition temperature (Tc) at ambient pressure. Thus,Nb films have been used in superconducting electronics and radio frequency cavity applications. In this study, the depositionalfactors determining the crystallinity and Tc of Nb films were investigated. An Nb film grown at a sputtering temperature of 240°Cexhibited the maximum crystallinity of Nb and the minimum crystallinity of niobium oxide. X-ray photoelectron spectroscopyconfirmed a maximum atomic percent of niobium and a minimum atomic percent of oxygen. A sputtering power of 210 W and asputtering time of 50 min were the optimal conditions for Nb deposition, and the Tc of the optimized film (9.08 K) was close to thatof bulk Nb (9.25 K). Transmission electron microscopy images of the thick film directly confirmed the removal of the typicalin-plane compressive strain in the (110) plane caused by residual stress.

      • KCI등재

        Removal of iron oxide scale from boiler feed-water in thermal power plant by high gradient magnetic separation: field experiment

        Yoko Akiyama,Suqin Li,Koshiro Akiyama,Tatsuya Mori,Hidehiko Okada,Noriyuki Hirota,Tsuyoshi Yamaji,Hideki Matsuura,Seitoku Namba,Tomokazu Sekine,Fumihito Mishima,Shigehiro NISHIJIMA 한국초전도저온학회 2021 한국초전도저온공학회논문지 Vol.23 No.3

        The reduction of carbon dioxide emissions becomes a global issue, the main source of carbon dioxide emissions in the Asianregion is the energy conversion sector, especially coal-fired power plants. We are working to develop technologies that will at leastlimit the increase in carbon dioxide emissions from the thermal power plants as one way to reduce carbon dioxide emissions. Ourresearch aims to reduce carbon dioxide emissions by removing iron oxide scale from the feedwater system of thermal power plantsusing a superconducting high-gradient magnetic separation (HGMS) system, thereby reducing the loss of power generationefficiency. In this paper, the background of thermal power plants in Asia is outlined, followed by a case study of the introduction ofa chemical cleaning line at an actual thermal power plant in Japan, and the possibility of introducing it into the thermal power plantsin China based on the results.

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