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NiFe<sub>2</sub>O<sub>4</sub>/m-ZrO<sub>2</sub>와 CeO<sub>2</sub>를 이용한 고온 태양열 열화학 싸이클의 수소 생산
김철숙,조지현,김동연,서태범,Kim, Chul-Sook,Cho, Ji-Hyun,Kim, Dong-Yeon,Seo, Tae-Beom 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.2
Two-step thermochemical cycle using ferrite-oxide($Fe_2O_4$) device was investigated. The $H_2O$(g) was converted into $H_2$ in the first experiment which was performed using a dish type solar thermal system. However the experiment was lasted only for 2 cycles because the metal oxide device was sintered and broken down. Another problem was that the reaction was taken place mainly on a side of the metal oxide device. The m-$ZrO_2$, which was widely known as a material preventing sintering, was applied on the metal oxide device. The ferrite loading rate and the thickness of the metal oxide device were increased from 10.67wt% to 20wt% and from 10mm to 15mm, respectively. The chemical reactor having two inlets was designed in order to supply the reactants uniformly to the metal oxide device. The second-experiment was lasted for 5 cycles, which was for 6 hours. The total amount of the $H_2$ production was 861.30ml. And cerium oxide($CeO_2$) device was used for increasing $H_2$ production rate. $CeO_2$ device had low thermal resistance, however, more $H_2$ production rate than $Fe_2O_4$ device.
접시형 태양열 시스템을 이용한 2단계 열화학 싸이클의 수소 생산과 PID 온도 제어 기법 연구
김철숙(Kim Chul-sook),김동연(Kim Dong-Yeon),조지현(Cho Ji-Hyun),서태범(Seo Tae-Beom) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.3
Solar thermal reactor was studied for hydrogen production with a two step thermochemical cycle including T-R(Thermal Reduction)step and W-D(Water Decomposition) step. NiFe2O4 and Fe3O4 supported by monoclinic ZrO2 were used as a catalyst device and Ni powder was used for decreasing the T-R step reaction temperature. Maintaining a temperature level of about 1100℃ and 1400℃, for 2-step thermochemical reaction, is important for obtaining maximum performance of hydrogen production. The controller was designed for adjusting high temperature solar thermal energy heating the foam-device coated with nickel–ferrite powder. A PID temperature control system was designed based on 2-step thermochemical reaction experiment data (measured concentrated solar radiation and the temperature of foam device during experiment). The cycle repeated 5 times, ferrite conversion rate are 4.49∼29.97% and hydrogen production rate is 0.19∼1.54mmol/g-ferrite. A temperature controller was designed for increasing the number of reaction cycles related with the amount of produced hydrogen.
김철숙(Chul-Sook Kim),차창환(Chang-Hwan Cha),조상문(Sang-Moon Cho),이승호(Seung-Ho Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Vegetable oil is the clean insulation oil which has less problem when there is the oil leakage from the transformers due to accidents or explosion of them because the biodegradability of vegetable oil is over 90%. Also it has advantage as noninflammable oil due to over 300℃ flashing point. Even though vegetable oil has many advantages, it has limitations as low cooling performance due to three times higher viscosity than existing mineral oil and poor insulation characteristic caused by high moisture content and water affinity. In this paper, we estimated the cooling performance between the mineral and vegetable oil. In the case of vegetable oil, this could predict that the temperature rise of top oil will increase about 4℃ than that of mineral oil. Also, on the basis of these results we can suggest cooling design to substitute vegetable oil for mineral oil.
NiFe₂O₄/m-ZrO₂와 CeO₂를 이용한 고온 태양열 열화학 싸이클의 수소 생산
김철숙(Kim, Chul-sook),조지현(Cho, Ji-hyun),김동연(Kim, Dong-yeon),서태범(Seo, Tae-beom) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.2
Two-step thermochemical cycle using ferrite-oxide(Fe₂O₄) device was investigated. The H₂O(g) was converted into H₂ in the first experiment which was performed using a dish type solar thermal system. However the experiment was lasted only for 2 cycles because the metal oxide device was sintered and broken down. Another problem was that the reaction was taken place mainly on a side of the metal oxide device. Them-ZrO₂, which was widely known as a material preventing sintering, was applied on the metal oxide device. The ferrite loading rate and the thickness of the metal oxide device were increased from 10.67wt% to 20wt% and from 10mm to 15mm, respectively. The chemical reactor having two inlets was designed in order to supply the reactants uniformly to the metal oxide device. The second-experiment was lasted for 5 cycles, which was for 6 hours. The total amount of the H₂ production was 861.30ml. And cerium oxide(CeO₂)device was used for increasing H₂ production rate. CeO₂ device had low thermal resistance, however, more H₂ production rate than Fe₂O₄ device.
변압기용 방열기 효율 계산을 위한 고전적 접근과 CFD 해석
조상문(Sang Moon Cho),김철숙(Chul Sook Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Recently, thermal problems in power transformer have been issued due to their lifetime and reliability. With a tendency to minimize a product, accurate prediction about efficiency of radiator becomes more important. In this background, this paper presents the method of calculation to estimate the efficiency of radiator used in power transformer cooling system. Two classical model was adopted to solve heat transfer induced by natural convection between radiator and air boundary. Temperature disribution and heat transfer coefficient were analytically investigated. To compare the result with those real case, CFD analysis and experimental investigation were companied. The overall efficiencies in each case of radiators were lower than we expected because of surrounding conditions which are different to real case. This result can help understand heat transfer phenomena in radiator and utilize to design optimum cooling system of power transformer.