Jinwon Yun

Model Based Hardware In the Loop Simulation of Thermal Management System for Performance Analysis of Proton Exchange Membrane Fuel Cell

2 School of Mechanical Engineering, Chungnam National Univ. 79, Daehangno, Yuseong-gu, Daejeon, 30-764, Korea Abstract >> A thermal management system of a proton exchange membrane fuel cell is taken charge of controlling the temperature of fuel cell stack by rejection of electrochemically reacted heat. Two major components of thermal management system are heat exchanger and pump which determines required amount of heat. Since the performance and durability of PEMFC system is sensitive to the operating temperature and temperature distribution inside the stack, it is necessary to control the thermal management system properly under guidance of operating strategy. The control study of the thermal management system is able to be boosted up with hardware in the loop simulation which directly connects the plant simulation with real hardware components. In this study, the plant simulation of fuel cell stack has been developed and the simulation model is connected with virtual data acquisition system. And HIL simulator has been developed to control the coolant supply system for the study of PEMFC thermal management system. The virtual data acquisition system and the HIL simulator are developed under LabVIEW TM

Methane steam reforming through shell-and-tube heat exchanging reformer to improve heat transfer rate from low temperature heat source

Statement of the Problem: Catalytic synthesis of organic sulfenamides and disulfides has great significance and value in synthetic chemistry and bioscience. Despite the prominent applications of sulfenamides, there are only a few reports about their preparation. In this contribution, we reported an oxidative coupling of 2-mercaptobenzothiazole leading to 2,2-disbenzothiazoledisulfide in up to 94 % yield.G acid (GABA) is a precursor to pyrrolidone, a monomer used for the production of a biodegradable polymer known as nylon-4. GABA is also widely used in the medical industry to treat conditions such as high blood pressure, anxiety and depression. Generally, GABA is produced from glutamate by the enzyme glutamate decarboxylase (GadB). In this study, a synthetic scaffold complex was introduced between Pyrococcus horikoshii GadB and the GABA antiporter (GadC) from E. coli. P. horikoshii GadB was attached to the N-terminus, C-terminus and middle of E. coli GadC via scaffolding. Among the three scaffold complexes evaluated, the N-terminus scaffold model produced 5.93 g/L of GABA from 10 g/L monosodium glutamate (MSG). When the gabT mutant E. coli XBT strain was used, the highest GABA concentration of 5.96 g/L was obtained, which is 97.8% of GABA yield. In addition to GABA concentration, GABA productivity was increased 3.5 fold via the synthetic scaffold complex.

Computational Analysis of the Methane Steam Reforming Process With Low-Temperature Waste Heat Source

When the high temperature stationary fuel cell system is designed with external reformer, typical approach to improve efficiency of system is to employ catalytic burner with fuel lean anode-off gas for methane steam reformer. Recently, there have been many studies on the hybrid fuel cell system using anode-off gas to produce additional power. In those hybrid systems, maximum temperature of heat duty for the reformer is significantly reduced. Optimization of heat management is very important for these low temperature reformers. In this study, we carried out an analytic study of the methane steam reforming process with heat duty of non-reactive, low temperature gases. It is found out that the temperature uniformity of inlet gases is crucial for high efficiency. Additionally, the reformer geometry such as heat transfer area and the aspect ratio are meaningful parameters which can severely affect the methane conversion rate under given conditions.Copyright

Secondary Flow Patterns of Liquid Ejector with Computational Analysis

* Dept. of Mechanical Engineering Chungnam Nat’l Univ.** COAVIS, *** Korea Automotive Technology Institute, (Received July 29, 2014 ; Revised September 25, 2014 ; Accepted October 30, 2014)Key Words: Nonpower-Pump(무동력펌프), Ejector(이젝터), Cavitation(공동현상), CFD Analysis(CFD 해석), Flux Ratio(유량비)초록: 무동력펌프의 일종인 이젝터는 압력을 갖는 유체를 노즐에서 분사하여 주위의 유체를 흡입 후 혼합유체를 외부 동력 없이 송출하는 장치이다. 구조가 간단하고 고장이 적어 여러 산업분야에서 이용되고 있으며, 자동차 산업에서는 연료주입용으로도 이용되고 있다. 대부분 이젝터는 가스상을 사용하기 때문에, 가스상 이젝터는 오래전부터 연구되어 왔다. 액체상 이젝터는 그 용도에 비해 아직 연구가 활발하지 못하다. 가스상 이젝터와 달리, 액체상 이젝터는 노즐목에서 부분적인 압력강하에의한 공동현상이 발생되고 이러한 공동현상은 부품파손을 유발하며, 소음을 발생시키는 원인이 되고 있다. 본 연구는 액체-액체상 이젝터의 최대 유량비와 공동현상 발생영역 비교를 위해 5가지 인자를 변경하여 2차원 축대칭 전산해석을 진행하였다. 액체 이젝터의 공동현상에서는 특히 노즐각도가 중요한 역할을 하였으며, 유량비 성능 특성은 혼합챔버각도 35°가 가장 유리한 것으로 판단된다. 이를 통해 공동 현상을 최소화 시키면서 성능 최적화를 달성할 수 있는 조합을 얻을 수 있음을 확인하였다.Abstract: An ejector is a type of non-powered pump that is used to supply a secondary flow via the ejection of a primary flow. It is utilized in many industrial fields, and is used for fueling the vehicle because of less failures and simple structure. Since most of ejectors in industry are gas-to-gas and liquid to gas ejector, many research activities have been reported in optimization of gas ejector. On the other hand, the liquid ejector is also applied in many industry but few research has been reported. The liquid ejector occurs cavitation, and it causes damage of parts. Cavitation has bees observed at the nozzle throat at the specified pressure. In this study, a two-dimensional axisymmetric simulation of a liquid-liquid ejector was carried out using five different parameters. The angle of the nozzle plays an important role in the cavitation of a liquid ejector, and the performance characteristics of the flow ratio showed that an angle of 35° was the most advantageous. The simulation results showed that the performance of the liquid ejector and the cavitation effect have to be considered simultaneously.

The Scale Up Characteristics of a Catalytic Combustor With Flow Uniformity Analysis

Catalytic combustors are used as off-gas combustors of molten carbonate fuel cells (MCFCs) because of their exhaust gas purity, geometric flexibility, and high combustion efficiency. In this study, a new design was investigated for possible application in internally reformed MCFC. The study started with performance analysis of a 5 kWe combustor, which could be precisely conducted due to availability of experimental apparatus. A 5 kWe combustor was used as a model combustor, and it was experimentally analyzed in terms of flow uniformity, catalyst screening, and reaction characteristics. The results show that the flow uniformity is able to reduce the exhaust gas concentration because temperature uniformity decreases the possibility of fuel slippages in locally lower temperature zones. As the capacity of the combustor is increased from 5 kWe to 25 kWe, the exhaust gas temperature at the same inlet condition as that of the 5 kWe combustor increases due to lower heat loss. As a result, the catalyst screening process shows different results due to higher operating temperatures, but three of four catalysts provide proper quality. On the other hand, flow uniformity improves economic competitiveness of the catalytic combustor. When the volume loading of catalytic monoliths was decreased, the performance was very similar to that of the original volume loading of catalytic monoliths.