두 개의 컨덕턴스미터를 이용한 슬러그류의 기공률 및 기공률 전달속력 실시간 측정

김종록(Jongrok Kim),안예찬(Yeh-Chan Ahn),강덕홍(Deok Hong Kang),김무환(Moo Hwan Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

Two ring-type conductance meters were manufactured to measure void fraction and its propagation speed in slug flow. The signal of conductance meter with two rings depends on liquid temperature. Therefore a conductance meter with separated probe designed by Coney (1973), which is independent of liquid temperature, was used and experimentally proved. The manufactured conductance meters showed a good repeatability and agreement with the analytical solution by Coney (1973). From time lag between two conductance meter, we could calculate the propagation speed of void fraction.

X-ray 현미경을 이용한 GDL(가스확산층)에서 물의 거동 및 분포에 관한 실험적 연구

김종록(Jongrok Kim),김태주(TaeJoo Kim),김무환(MooHwan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

The water management is one of the most critical issues for the PEMFC commercialization. In order to make a proper scheme for water management, the information of behavior of water is very important. So, the X-ray imaging has joined the canon of diagnostic methods for the fuel cell research and is applied worldwide with qualitative and quantitative results. In this study, we did experimental study about behavior of water in GDL using X-ray microscope in Pohang Accelerator Laboratory. For this aim, we prepared a simple experimental model which has two channels on both face of GDL. The behavior of water in the GDL were observed as functions of the thickness of compressed GDL and the pressure of injected water on a channel. X-ray microscope shows the water in GDL had different behavior for each thickness of GDL and each pressure of injected water on steady and unsteady conditions. The water easily permeated to GDL when compressed GDL was thick and pressure of injected water was high.

연료전지 다공성막을 통한 수분증발량의 정량적 측정에 관한 실험적 연구

김종록(Jongrok Kim),김무환(Moo Hwan Kim),손상영(Sang Young Son) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.6

연료전지 시스템에서 잔류 수분의 제거과정은 연료전지의 성능 및 수명 관리를 위해 중요한 과정이다. 효과적인 수분 제거과정의 설계를 위해서는 연료전지내의 수분 제거 특성에 대한 이해가 필수적이다. 이를 위해 본 연구에서는 연료전지의 다공성막인 가스확산층을 통한 수분증발량을 정상상태에서 측정하는 실험 기법을 개발하였다. 이 기법을 이용하여 연료전지의 잔류수분 제거 현상을 모사하는 실험장치를 개발하였다. 그리고 건조가스와 가스확산층의 변수가 수분에 미치는 영향을 실험적으로 측정하였다. 건조가스의 습도가 낮고, 유량이 높을수록 가스확산층을 통해 증발되는 수분량이 높았다. 또한 가스확산층의 두께가 얇을수록 수분 증발량이 높은 특성을 확인하였다. Removing residual water in a fuel cell is a critical operational process for managing its performance and controlling its lifetime. Understanding the mechanism of water transport in fuel cells is essential for the design of the water removal process. In this study, an experimental method for measuring the water evaporation rate through a gas diffusion layer, which is a porous medium, under steady-state conditions was developed. Experimental bench tests were conducted to apply the developed method. Then, the effects of various parameters of the drying gas and the gas diffusion layer were experimentally measured. The water evaporation rate increased as the humidity of the drying gas decreased and the flow rate of the drying gas increased. In addition, a thinner gas diffusion layer yielded a higher water evaporation rate.

습도센서와 미세입자센서의 원자로냉각재계통 누설 감지 성능 비교 연구

김종록(Jongrok Kim),김우식(WooShik Kim),권태순(Tae-Soon Kwon) 한국유체기계학회 2022 한국유체기계학회 학술대회 논문집 Vol.2022 No.11

3-ring 임피던스미터의 유체 전기 전도도 독립성에 대한 실험적 연구

김종록(Jongrok Kim),안예찬(Yeh-Chan Ahn),김무환(Moo Hwan Kim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.11

2상유동(기체-액체) 현상은 전자기발전, 원자력발전, 철강산업 등 유체 시스템에 자주 나타나는 현상으로, 2상유동을 파악하는 것은 유체 시스템의 안정성 및 성능을 위해 중요하다. 2상유동 특성 중 기공률은 압력강하와 열전달 성능을 결정하는 주요 인자로서 이를 측정하는 기술이 특히 중요하다. 유동의 임피던스를 측정하여 기공률을 산정하는 임피던스법은 전기적 특성을 이용하기 때문에 반응속도가 빨라 실시간 측정이 가능하며, 유동관 벽에 전극을 설치할 경우 유동 교란없이 측정할 수 있는 장점이 있다. Coney는 원형관에 적용할 수 있는 ring 임피던스미터를 이론적 연구하였다. 본 연구에서는 Coney가 이론적으로 제안하고 실험적으로 검증하지 못한 3-ring 임피던스미터의 유체 전기전도도에 대한 독립성을 실험적으로 검증하였다. A two-phase (gas-liquid) flow is a common phenomenon in fluidic systems, e.g., fluidic systems in the electro-magnetic or nuclear power generation industry and in the steel industry. The measurement of a two-phase flow is important for guaranteeing the safety of the system and for achieving the desired performance. The measurement of the void fraction, which is one of the parameters of the two-phase flow that determines the pressure drop and heat transfer coefficient, is very important. The time resolution achieved by employing the impedance method that can be used to calculate the void fraction from the impedance of the fluid is high because the electric characteristics are taken into account. Therefore, this method can be employed to accurately measure the void fraction without distortion of flow in real time by placing electrodes on the walls of the tubes. Coney analytically studied a ring-type impedance meter, which can be employed in a circular tube. The aim of this study is to experimentally verify the robustness of a three-ring impedance meter to variations in the electric conductivity of the fluid; this robustness was suggested by Coney but was not experimentally verified.

무선 OFDM 시스템에서 MUSIC을 기반으로 하는 효율적인 주파수 옵셋 추정

김종록(JongRok Kim),장석진(Sekchin Chang) 대한전기학회 2006 정보 및 제어 심포지엄 논문집 Vol.2006 No.1

As OFDM-based systems exhibits robustness over wireless channel, it is possible to consider them the next generation of the wireless communications including the mobile communications. However, there is a critical point that OFDM-based systems can receive the distorted signal due to the frequency-offset. Therefore, it is necessary to accurately estimate the frequency-offset for OFDM-based systems to be adopted as the next wireless communication systems. In this paper, the efficient frequency-offset estimation scheme based on MUSIC is presented in 802.11a WLAN systems. As shown in the simulation result. this scheme can improve and optimize the estimation performance.

3-ring 임피던스미터를 이용한 슬러그류 및 기포류의 기공률 측정

김종록(Jongrok Kim),안예찬(Yeh-Chan Ahn),김무환(Moo Hwan Kim) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.1

관내 2상 유동의 기공률을 효과적으로 측정할 수 있는 3-ring 임피던스미터를 이용하여 실제 슬러그류 및 기포류를 측정하였다. 먼저, 임피던스미터의 신호와 기공률 사이의 보정곡선을 구하였다. 임피던스미터는 동일한 기공률을 갖는 슬러그류와 기포류에 대해 각각 다른 보정곡선을 나타내는 특성을 보였다. 임피던스미터는 유동패턴에 따라 두 보정 곡선 중 하나를 선택해야 하며, 기공률 측정 결과로부터 유동 패턴을 판단할 수 있었다. 두 개의 임피던스미터를 통해 측정된 기공률 변화 곡선으로부터 기포의 이동 속도, 크기를 효과적으로 측정할 수 있었다. Real slug and bubbly flows were measured using a three-ring impedance meter that can efficiently measure the void fraction of two-phase flows in a tube. First, the fitting curves between the signal from the impedance meters and the void fraction were found. The impedance meter had different fitting curves for slug and bubbly flows that had the same void fraction. An impedance meter should choose one of the two fitting curves according to the flow pattern, and the flow patterns can be recognized using the measured void fraction. The velocities and sizes of the bubbles were calculated using the void fraction curves measured by two impedance meters.

옴니 카메라의 전방향 영상을 이용한 이동 로봇의 위치 인식 시스템

김종록(Jongrok Kim),임미섭(Mee-Seub Lim),임준홍(Joonhong Lim) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.3

Vision-based robot localization is challenging due to the vast amount of visual information available, requiring extensive storage and processing time. To deal with these challenges, we propose the use of features extracted from omni-directional panoramic images and present a method for localization of a mobile robot equipped with an omni-directional camera. The core of the proposed scheme may be summarized as follows : First, we utilize an omni-directional camera which can capture instantaneous 360˚ panoramic images around a robot. Second, Nodes around the robot are extracted by the correlation doefficients of Circular Horizontal Line between the landmark and the current captured image. Third, the robot position is determined from the locations by the proposed correlation-based landmark image matching. To accelerate computations, we have assigned the node candidates using color information and the correlation values are calculated based on Fast Fourier Transforms. Experiments show that the proposed method is effecitve in global localization of mobile robots and robust to lighting variations.

평판 삼전극 컨덕턴스미터에 대한 실험적 연구

김종록(Jongrok Kim),어동진(Dong Jin Euh),조형규(Hyoung-Kyu Cho) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12

The real time measurement of the void fraction, which is one of the parameters of the two-phase flow that determines the pressure drop and heat transfer coefficient in a fluidic system, is very important. The time resolution that achieved by employing the conductance method that can be used to calculate the liquid film thickness from the electric conductivity of the fluid is high because the electric characteristics are taken into account. Therefore, this method can be employed to accurately measure the film thickness without distortion of flow in real time by placing electrodes on the walls.Coney analytically studied a three probe conductance meter, which can void an error by variation of liquid temperature. The aim of this study is to compare the experimental signal of three probe conductance meter and the analytical predicted signal and to experimentally verify the robustness of a three probe conductance meter to variations in the electric conductivity of the fluid.

중성자 영상법을 이용한 PEMFC 에서의 물 배출 특성에 관한 실험적 연구

김태주(TaeJoo Kim),김종록(JongRok Kim),김무환(MooHwan Kim),심철무(CheulMuu Sim),이승욱(SeungWoo Lee),전진수(JinSoo Jeon) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

The neutron imaging technique was used to investigate the water discharge characteristics at PEMFC. The feasibility test apparatus was consisted of pressurized air and water in order to simulate the actual operating PEMFC. The feasibility tests have been performed at two kinds of flow field type (1-parallel and 3-parallel) with 100 ㎠ active area and different flow rate (200, 400, and 850 ㏄/min). Although the water and pressurized air was supplied only into cathode, the water movement into anode was found by neutron image. The water at cathode is well discharged, but except the 850 ㏄/min at 3-parallel flow field type, the water at the anode was not removed by pressurized air. The total water volume variations at each condition were calculated from the neutron images. This technique can be used for detailed studies on water distribution and transport in the PEMFC.