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Hun Sik Han(한훈식),Han-Ok Kang(강한옥),Juhyeon Yoon(윤주현),Young In Kim(김영인),Youngmin Bae(배영민),Sang Ji Kim(김상지) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
A numerical study is conducted for the secondary side screw-type tube inlet orifice design of a once-through steam generator. Various tube plugging conditions and power levels are considered, and the secondary coolant inlet temperature is adjusted to maintain a constant thermal power. Comprehensive numerical solutions are acquired to evaluate the minimum orifice length under various operating conditions, and the required minimum orifice length to suppress the flow oscillation below the allowable level is evaluated. The results obtained show that the lowest power level results in the highest minimum orifice length and non-plugging condition provides a limiting case for the orifice length criterion.
Experiments on PEMFC performance enhancement by pulsating cathode flow
한훈식(Han, Hun-Sik),김기웅(Kim, Ki-Woong),김윤호(Kim, Yun-Ho),김서영(Kim, Seo-Young) 한국신재생에너지학회 2008 한국신재생에너지학회 학술대회논문집 Vol.2008 No.05
Experiments have been performed to investigate effects of pulsating cathode flow on a 10-cell proton exchange membrane fuel cell (PEMFC) stack. For all the experiments, the flow rate, temperature and relative humidity of hydrogen at the anode inlet are fixed. The effects of the pulsating frequency, amplitude and flow rate at the cathode inlet on performance of 10-cell PEMFC are examined. The polarization and power curves show that the power output and limiting current is substantially increased when the pulsating component is added to cathode flow channel. The maximum power output increases by up to 38% and enhancement of the overall performance is more pronounced at lower flow rate region.
한훈식(Hun Sik Han),김명기(Myungkee Kim),엄석기(Sukkee Um),김서영(Seo Young Kim) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.3
Experiments have been performed to investigate the key parameters determining the performance of thermoelectric power generation. The experimental results obtained show that the power output significantly increases with the temperature difference between cold and hot sides of thermoelectric generator. However, the effect of the hot side temperature under the identical temperature difference on the overall performance of a thermoelectric generator is meager. The conversion efficiency defined as the ratio of the power generated to the heat absorbed at the hot side increases with the temperature difference. The behavior of the thermoelectric generator is shown to be consistent with the theoretical analysis. The optimum current giving the maximum conversion efficiency and the maximum conversion efficiency are linearly increased with the temperature difference.
Performance Analysis of a Once-Through Steam Generator for Constant Thermal Power Operation
Hun Sik Han(한훈식),Juhyeon Yoon(윤주현),Young In Kim(김영인) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
A numerical study is made of the operation strategy of a once-through steam generator considering degradation in the thermal-hydraulic performance. The performance of the steam generator is gradually degraded as it experiences fouling, clogging, and plugging during its lifetime. To maintain the thermal power of the steam generator, therefore, its operating condition should be properly changed according to the degradation rate. Emphasis is given to the operation strategy of the steam generator to transport a constant thermal power regardless of the degradation rate. Comprehensive numerical solutions to the governing equations are acquired. It is found that a constant thermal power can be maintained by properly adjusting the secondary coolant outlet pressure with a variation of the superheat degree and secondary coolant pressure drop. A constant thermal power operation curve is obtained, and the thermal-hydraulic performance of the steam generator is analyzed according to the degradation rate in terms of the degree of superheat, secondary coolant pressure drop, temperature distribution, and quality distribution in the tube.
200 W급 휴대용 고분자 전해질막 연료전지 시스템 개발
한훈식(Hun Sik Han),김윤호(Yun Ho Kim),조창환(Changhwan Cho),김서영(Seo Young Kim),현재민(Jae Min Hyun) 대한설비공학회 2012 설비공학 논문집 Vol.24 No.2
A 200 W portable polymer electrolyte membrane fuel cell (PEMFC) system is developed. The PEMFC system consists of an air-cooled fuel cell stack module, a fuel supply subsystem, a power management subsystem, and a control electronics subsystem. The control logic is designed for the stable system operation. The system-level performance evaluation discloses that the present PEMFC system provides a rated power output of 200.5 W at 13.4 V with the maximum balance-of-plant (BOP) efficiency of 72%, and maximum system efficiency based on lower heating value (LHV) is 37% at 120.7 W system power output.
한훈식(Hun Sik Han),김명기(Myungkee Kim),김서영(Seo Young Kim),엄석기(Sukkee Um) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Experiments on the power generation of a thermoelectric cooler (Huimao: TEC1-012707T125) have been performed to investigate the key parameters determining the thermoelectric power generation performance. The hot side temperature of the thermoelectric cooler was controlled by a film heater. To adjust the cold side temperature, an additional thermoelectric cooler with a heat sink and a duct-flow type fan arrangement was installed. The experimental results obtained show that the performance of thermoelectric power generation is significantly enhanced as the temperature difference between hot side and cold side of thermoelectric cooler increases. However, the effect of the hot side temperature under the identical temperature difference on the thermoelectric power generation is meager. The conversion efficiency defined as the ratio of the maximum power output to the heat absorbed at the hot side increases with the temperature difference.
열교환기의 열저항에 따른 열전모듈 냉방 성능에 대한 연구
한훈식(Hun Sik Han),김서영(Seo Young Kim),지용준(Young-Jun Jee),이대웅(Daewoong Lee),장길상(Kil Sang Jang),오동훈(Dong Hoon Oh) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Thermal performance of a thermoelectric module (TEM) in a thermoelectric cooling system with a heat sink is analytically examined. The thermoelectric cooling system is composed of a water jacket, a thermoelectric module and a heat sink. The thermal performance of a thermoelectric module (Ferro Tee: TE 9500-127-060B) with the selected convective thermal resistance of a heat sink (Rev) is evaluated. The results show that the cooling performance of a thermoelectric module is enhanced as the convective thermal resistance decreases. The thermoelectric cooling system with R<SUB>cv</SUB>=0.3 provides 44.9% higher COP (coefficient of performance) and 59.5% higher heat absorbed compared to R<SUB>cv</SUB>= 1.1, respectively.
원통형 수증기 개질기의 열적조건 변화에 따른 개질성능 평가
한훈식(Hun Sik Han),김서영(Seo Young Kim),강상우(Sarng Woo Karng) 대한설비공학회 2014 설비공학 논문집 Vol.26 No.6
The experimental performance evaluation of a cylindrical steam reformer with various thermal conditions has been conducted. The bottom space of the cylindrical reactor was packed with Ruthenium (Ru) catalyst. A three-segment furnace was installed to create the axially variable boundary temperature distribution. Six K-type thermocouples were inserted into the catalyst layer, and three exhaust ports were fabricated on the side wall along the flow direction. The exhausted gases at each port were analyzed by using gas chromatograph (GC) system. The experimental results showed that the reforming reaction occurs intensively in the upstream region and more hydrogen is obtained when the intake gas is sufficiently heated up through the enhanced steam reforming (SR) reaction. The axially increasing boundary temperature setup provided the maximally accumulated reforming efficiency of 74.8%, when the reactor was placed at the 3rd section of the furnace.