• Journal of the Korean Institute of Gas
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• v.8 no.1 s.22
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• pp.1-6
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• 2004

In general, inlet temperature of cooling sea water for steam turbine condenser is about $25^{\circ}C$ and outlet temperature is about $60^{\circ}C$. For oil cooler, outlet temperature is about $40^{\circ}C$. Therefore corrosion heavily depends on the temperature of the coolant of a heat exchanger system. It is necessary to set the temperature of the cooling water to have maximum heat transfer efficiency. This paper was studied on the effect of temperature on SCC of Al-brass which is used as a tube material of vessel heat exchanger in $3.5\%$ NaCl + $0.1\%\;NH_4OH$ solution under flow by constant displacement tester. Based on the test results, the behavior of polarization characteristic, stress corrosion crack popagation and dezincification characteristic of Al-brass was investigated.

• Plant Journal
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• v.17 no.1
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• pp.38-49
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• 2021

In order to increase power plant efficiency, the steam temperature was increased to 610 ℃ which deteriorates the durability of the boiler tube and as the use of low-calorie coal increases the post combustion and delayed combustion phenomenon, the overheating of the final reheater and the tube rupture are becoming frequent. In order to prevent overheating of the final reheater, desuperheater water injection was increased, leading to a decrease in boiler efficiency. In this study install a baffle plate at the back of some overheated tube groups, thereby reduce the temperature of the tube by reducing the amount of combustion gas, and the reduced combustion gas moves to an adjacent place to increase the temperature of other tubes. As a result of the study, the temperature deviation between tubes decreased 1.5. And the heat-reducing injection amount was reduced to 6,929 kg/h and the maximum tube temperature was reduced to 623.4℃ which is 6.6℃ more below than the control standard of 630℃.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1540-1553
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• 2019

A nuclear power plant (NPP) is a highly complex system-of-systems as manifested through its internal systems interdependence. The negative impact of such interdependence was demonstrated through the 2011 Fukushima Daiichi nuclear disaster. As such, there is a critical need for new strategies to overcome the limitations of current risk assessment techniques (e.g. the use of static event and fault tree schemes), particularly through simulation of the nonlinear dynamic feedback mechanisms between the different NPP systems/components. As the first and key step towards developing an integrated NPP dynamic probabilistic risk assessment platform that can account for such feedback mechanisms, the current study adopts a system dynamics simulation approach to model the thermal dynamic processes in: the reactor core; the secondary coolant system; and the pressurized water reactor. The reactor core and secondary coolant system parameters used to develop system dynamics models are based on those of the Palo Verde Nuclear Generating Station. These three system dynamics models are subsequently validated, using results from published work, under different system perturbations including the change in reactivity, the steam valve coefficient, the primary coolant flow, and others. Moving forward, the developed system dynamics models can be integrated with other interacting processes within a NPP to form the basis of a dynamic system-level (systemic) risk assessment tool.

• Plant Journal
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• v.14 no.4
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• pp.48-54
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• 2018

As the emission limits for NOx in power generation facilities were strengthened, HRSGs installed in the 1990s became necessary to install additional DeNOx system. However, since there is no space in the HRSG for installing the entire the catalyst and ammonia injection grid, as an alternative, the catalyst was installed inside of the HRSG and the ammonia injection device was installed in the exhaust duct of the gas turbine. Experiments were conducted in horizontal HRSG of Incheon combined cycle power plant. Experimental results show that the ammonia injection method in the gas turbine exhaust duct is 1.2 times higher than the HRSG internal ammonia injection method. However when operating a HRSG for 30 years as its life span, ammonia injection method in the gas turbine exhaust duct is more economical than the cost of new HRSG construction.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.2
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• pp.150-159
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• 2013

To enhance the performance of SEWGS system by holding the WGS catalyst in a SEWGS reactor using bed inserts, effects of insert geometry and shape of WGS catalysts on CO conversion were measured and investigated. Small scale fluidized bed reactor was used as experimental apparatus and WGS catalyst (particle and tablet) and sand were used as bed materials. The parallel wall type and cross type bed inserts were used to hold the WGS catalysts. The CO conversion with steam/CO ratio was determined based on the exit gas analysis. The measured CO conversion using the bed inserts showed high value comparable to physical mixing cases. Moreover, gas flow direction was confirmed by bed pressure drop measurement for each case. Most of input gas flowed through the catalyst side when we charged tablet type catalyst into the bed insert and this can cause low $CO_2$ capture efficiency because the possibility of contact between input gas and $CO_2$ absorbent is low in this case. New bed insert geometry was proposed based on the results from this study to enhance contact between input gas and WGS catalyst and $CO_2$ absorbent.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.169-179
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• 2023

Filtered containment system is a passive safety system that controls the over-pressurization of containment in case of a design-based accidents by venting high pressure gaseous mixture, consisting of air, steam and radioactive particulate and gases like iodine, via a scrubbing system. An indigenous lab scale facility was developed for research on iodine removal by venturi scrubber by simulating the accidental scenario. A mixture of 0.2 % sodium thiosulphate and 0.5 % sodium hydroxide, was used in scrubbing column. A modified mathematical model was presented for iodine removal in venturi scrubber. Improvement in model was made by addition of important parameters like jet penetration length, bubble rise velocity and gas holdup which were not considered previously. Experiments were performed by varying hydrodynamic parameters like liquid level height and gas flow rates to see their effect on removal efficiency of iodine. Gas holdup was also measured for various liquid level heights and gas flowrates. Removal efficiency increased with increase in liquid level height and gas flowrate up to an optimum point beyond that efficiency was decreased. Experimental results of removal efficiency were compared with the predicted results, and they were found to be in good agreement. Maximum removal efficiency of 99.8% was obtained.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.130-130
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• 2020

수자원장기종합계획에 따르면 전국 지하수위는 지하수 이용의 지속적인 증가와 도시화에 따른 지하수 함양감소 등으로 최근 매년 조금씩 감소하고 있다. 특히, 환경부의 지하수조사연보(2018)에 따르면 남한강하류 중권역은 한강수계 전체 지하수 사용량의 약 34.5 %를 차지하고 있는 것으로 분석되었으며, 2009년에 비하여 2017년의 지하수위는 1.4 m의 감소 되었다. 본 연구는 한강유역에서 지하수 개발밀도가 높은 이천시에 위치해 있는 복하천 유역(303.8㎢)을 대상으로 지하수위 감소에 따른 기저유량 변동특성을 파악하기 위하여 SWAT-MODFLOW(Soil And Water Assessment Tool-MODFLOW)을 적용하고자 한다. SWAT-MODFLOW는 준분포형 장기유출모형 SWAT과 3차원 분포형 지하수 모의가 가능한 MODFLOW를 연계한 모형이며, MODFLOW만으로는 해결할 수 없는 일별 지하수 함양량의 분포와 SWAT만으로는 계산 불가능했던 지하수위의 시공간 분포를 보완하여 재생함으로써 두 모형의 한계를 극복한 모델이다. SWAT의 검보정 결과로서는 RMSE는 10.6 mm/day, NSE는 0.72, R²는 0.69 효율이 나타났으나, 지하수 유출이 보정되지 않아 MODFLOW의 입력자료인 토양두께(m), 수리전도도(m/day), 비저류량(1/m), 비산출율을 토양통에 따라 분류한 해외논문(Steven et.al 2005) 자료를 산정하여 SWAT-MODFLOW 두모형을 연계한 프로그램에 입력하여 지하수 유출을 보완하였고 SWAT과 SWAT-MDFLOW 지하수 유출량 비교뿐만이 아닌 SWAT-MODFLOW의 출력자료인 지하수위 및 지하수 충진량을 검토하였다.

• Fire Science and Engineering
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• v.33 no.6
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• pp.126-131
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• 2019

Real-scale fire tests were performed on animal-origin foods using a gas stove with no overheating prevention device. When the animal-origin foods were ignited, a large quantity of white smoke and steam was generated from them; however, when they became dry and began to carbonize, a dark smoke was generated. Even after the gas stove was overheated for more than 5400 s, mackerel, pollack, chicken, etc., did not ignite. However, pork, beef, and tuna caught fire after 2643 s, 2819 s, and 6492 s of heating, respectively. The flame patterns of animal-origin foods were in the forms of a mixed laminar flow and a turbulent flow, and a halo pattern was produced. A sand glass form of the flame pattern was generated when a kitchen hood was operated, but a triangular flame pattern was produced when the kitchen hood was not operated. When the tuna in the pot was overheated, it spontaneously ignited after 6492 s, with the surface temperature of the kitchen hood rapidly rising to 464.5 ℃. Moreover, the temperature at the back of the pot, which was 6 cm away from the outer surface of the upper part of the pot, was 869 ℃ after 6660 s because of the radiant heat. The flame formed a sand glass pattern on the kitchen wall. When the kitchen hood was not operated, or when the flame grew lower than the height of the ceiling, a triangular pattern was formed.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.795-800
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• 2009

In this study, the $CO_2$ removal characteristics of the Vortex tube type absorbtion apparatus were investigated to enhance the compactness of $CO_2$ absorption process and to reduce the amount of absorbing solution of the $CO_2$ separation process. The Vortex tube with the diameter of 17 mm and the length of 250mm was introduced in the experimental apparatus to treat $20Nm^3/hr$ of $CO_2$ containing flue gas. The flue gases for experiments containing 11~13 vol% of $CO_2$ were supplied from the coal-firing CFBC power plant with 12 ton/hr of steam producing capacity. The mixed solutions of 20 wt% of MEA as base solution with the adding solutions like HMDA, AMP and KOH were used as absorbents. The experiments were executed under the various conditions like the absorbing solution concentrations in the range of 20 to 50 wt%, the flow rate of $CO_2$ containing flue gases in the range of 6 to $15Nm^3/hr$ and the flow rate of absorbing solution in the range of 1.0 to 3.0 l/min. As a results, the $CO_2$ removal efficiency of mixed absorbent of 20 wt% of MEA with HMDA was remarkable. From this study, we concluded that the efficient separation of $CO_2$ from flue gases using the features of the Vortex tube type absorbing unit for gas/liquid contact and the separation of gas/liquid be possible. But more works are needed to increase the $CO_2$ removal efficiency of Vortex tube process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.171-179
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• 2012

Cooling of hot sections, especially the turbine nozzle and rotor blades, has a significant impact on gas turbine performance. In this study, the influence of precooling of the cooling air on the performance of gas turbines and their combined cycle plants was investigated. A state-of-the-art F-class gas turbine was selected, and its design performance was deliberately simulated using detailed component models including turbine blade cooling. Off-design analysis was used to simulate changes in the operating conditions and performance of the gas turbines due to precooling of the cooling air. Thermodynamic and aerodynamic models were used to simulate the performance of the cooled nozzle and rotor blade. In the combined cycle plant, the heat rejected from the cooling air was recovered at the bottoming steam cycle to optimize the overall plant performance. With a 200K decrease of all cooling air stream, an almost 1.78% power upgrade due to increase in main gas flow and a 0.70 percent point efficiency decrease due to the fuel flow increase to maintain design turbine inlet temperature were predicted.