금속수소화물 수소 저장 용기 내부의 수소흡장에 대한 수치해석적 연구

남진무,강경문,주현철 한국수소및신에너지학회 2010 한국수소 및 신에너지학회논문집 Vol.21 No.4

In this paper, a three-dimensional hydrogen absorption model is developed to precisely study hydrogen absorption reaction and resultant heat and mass transport phenomena in metal hydride hydrogen storage vessels. The 3D model is first experimentally validated against the temperature evolution data available in the literature. In addition to model validation, the detailed simulation results shows that at the initial absorption stage, the vessel temperature and H/M ratio distributions are uniform throughout the entire vessel, indicating that the hydrogen absorption is so efficient during the early hydriding process and thus local cooling effect is not influential. On the other hand, nonuniform distributions are predicted at the latter absorption stage,which is mainly due to different degrees of cooling between the vessel wall and core regions. This numerical study provides the fundamental understanding of detailed heat and mass transfer phenomena during hydrogen absorption process and further indicates that efficient design of storage vessel and cooling system is critical to achieve fast hydrogen charging and high hydrogen storage efficiency.

고분자전해질형연료전지 내부 가스 크로스오버 현상의 수치적 연구

남진무(Jinmoo Nam),주현철(Hyunchul Ju) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4

The goal of this paper is to numerically investigate the effects of hydrogen and oxygen crossover in Polymer Electrolyte Fuel Cells (PEFCs). A gas crossover model is newly developed and implemented into a comprehensive multi-dimensional, multi-phase PEFC model developed earlier. A parametric study is carried out with various crossover diffusion coefficients for hydrogen and oxygen. The simulation results demonstrate that the hydrogen crossover induces additional oxygen reduction reaction (ORR) and thereby causes additional voltage loss, while the influence of oxygen crossover on PEFC performance is minimal because it only leads to the hydrogen/oxygen chemical reaction in the anode side. This study clearly elucidates the detailed mechanism of hydrogen and oxygen crossover phenomena inside PEFCs.

Numerical analysis of the coupled heat and mass transfer phenomena in a metal hydride hydrogen storage reactor(I) - Model development of analyzation for hydrogen absorption reaction using the LaNi_5 bed

남진무(Nam, Jinmoo),주현철(Ju, Hyunchul) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

Within recent years attention has been focused on the method of hydrogen storage using metal hydride reactor due to its high energy density, durability, safety and low operating pressure. In this paper, a numerical study is carried out to investigate the coupled heat and mass transfer process for absorption in a cylindrical metal hydride hydrogen storage reactor using a newly developed model. The simulation results demonstrate the evolution of temperature, equilibrium pressure, H/M atomic ratio and velocity distribution as time goes by. Initially, hydrogen is absorbed earlier from near the wall which sets the cooling boundary condition owing to that absorption process is exothermic reaction. Temperature increases rapidly in entire region at the beginning stage due to the initial low temperature and enough metal surface for hydrogen absorption. As time goes by, temperature decreases slowly from the wall region due to the better heat removal. Equilibrium pressure distribution appears similarly with temperature distribution for reasons of the function of temperature. This work provides a detailed insight into the mechanism and corresponding physicochemical phenomena in the reactor during the hydrogen absorption process.

금속수소화물 수소 저장 용기 내부의 수소방출에 대한 수치해석적 연구

강경문,남진무,유하늘,주현철 한국수소및신에너지학회 2011 한국수소 및 신에너지학회논문집 Vol.22 No.3

In this paper, a three-dimensional hydrogen desorption model is developed to precisely study the hydrogen desorption kinetics and resultant heat and mass transport phenomena in metal hydride hydrogen storage vessels. The metal hydride hydrogen desorption model, i.e. governed by the conservation of mass,momentum, and thermal energy is first experimentally validated against the temperature evolution data measured on a cylindrical LaNi5 metal hydride vessel. The equilibrium pressure used for hydrogen desorption simulations is derived as a function of H/M atomic ratio and temperature based on the experimental data in the literature. The numerical simulation results agree well with experimental data and the 3D desorption model successfully captures key experimental trends during hydrogen desorption process. Both the simulation and experiment display an initial sharp decrease in the temperature mainly caused by relatively slow heat supply rate from the vessel external wall. On the other hand, the effect of heat supply becomes influential at the latter stages, leading to smooth increase in the vessel temperature in both simulation and experiment. This numerical study provides the fundamental understanding of detailed heat and mass transfer phenomena during hydrogen desorption process and further indicates that efficient design of storage vessel and heating system is critical to achieve fast hydrogen discharging performance.

고분자전해질형연료전지의 가스 채널 최적화를 위한 수치적 연구 (Ⅱ)

주현철(Hyunchul Ju),남진무(Jinmoo Nam) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.9

Using the multi-dimensional, multi-phase, nonisothermal Polymer Electrolyte Fuel Cell (PEFC) model presented in Part I, the effects of land/channel flow-field on temperature and liquid saturation distributions inside PEFCs are investigated in Part II. The focus is placed on exploring the coupled water transport and heat transfer phenomena within the nonisothermal and two-phase zone existing in the diffusion media (DM) of PEFCs. Numerical simulations are performed varying the land and channel widths and simulation results reveal that the water profile and temperature rise inside PEFCs are considerably altered by changing the land and channel widths, which indicates that oxygen supply and heat removal from the channel to the land regions and liquid water removal from the land toward the gas channels are key factors in determining the water and temperature distributions inside PEFCs. In addition, the adverse liquid saturation gradient along the thru-plane direction is predicted near the land regions by the numerical model, which is due to the vapor-phase diffusion driven by the temperature gradient in the nonisothermal two-phase DM where water evaporates at the hotter catalyst layer, diffuses as a vapor form and then condenses on the cooler land region. Therefore, the vapor phase diffusion exacerbates DM flooding near the land region, while it alleviates DM flooding near the gas channel.

연료전지 모델을 이용한 분리판 분할 전류밀도분포 측정에 대한 연구

최용준(Yongjun Choi),이기용(Giyong Lee),남진무(Jinmoo Namg),주현철(Hyunchul Ju) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5

The goal of this paper is to numerically evaluate the accuracy of the measurement technique by applying a three-dimensional, two-phase fuel cell model to a 100㎠ area fuel cell geometry in which segmented bipolar plate(BP) and non-segmented membrane are combined together. The measurement method via segmented BP is generally used to be justified. The simulation results revealed a similarity of the current distribution between membrane and BP but not perfectly matched. The maximum relative error of 33% exited near the U-turn regions and the numerical study further illustrates that the erroneous result originates from the BP segmented non-symmetrically based on the flow channels that allows some currents by passing flow channels to flow into its neighboring segment. Finally, this paper suggested optimal way to minimize the error between bipolar plate and membrane.