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In this paper, both theoretical and experimental investigations have been performed to examine the effects of key operating parameters on the cell performance of a DMFCs (i.e., methanol feed concentration and operating temperature). For experiment, the membrane electrode assemblies (MEAs) were prepared using a conventional MEA fabrication method based on a catalyst coated electrode (CCE) and tested under various cell temperatures and methanol feed concentrations. The polarization curve measurements were conducted using in-house-made 25cm² MEAs. The voltage-current density data were collected under three different cell temperatures (50?C, 60?C, and 70?C) and four different methanol feed concentrations (1 M, 2 M, 3 M, and 4 M). The experimental data indicate that the measured I-V curves are significantly altered, depending on these conditions. On the other hand, previously developed one-dimensional, two-phase DMFC model is simulated under the same operating conditions used in the experiments. The model predictions compare well with the experimental data over a wide range of these operating conditions, which demonstrates the validity and accuracy of the present DMFC model. Furthermore, both simulation and experimental results exhibit the strong influences of methanol and water crossover rates through the membrane on DMFC performance and I-V curve characteristics.
Convective heat loss from solar tower receiver is experimentally investigated in wind tunnel with tilt angles and operating conditions. In order to simulate the receiver, an electric heater, which is made of aluminum (width : 100 ㎜, height : 100㎜) is used and installed in the wind tunnel. The convective heat loss from the receiver is dependent on the direction and the velocity of the wind and the surface temperature of the receiver. The tilt angle and surface temperature of the receiver are varied from 0o(cavity facing straight down) and 90o(cavity aligned horizontally) and from 150℃ to 250℃, respectively. Also, the wind speed is changed from 0 to 4㎧. The convective heat loss is obtained by measuring consumed power to the heater to maintain the desired surface temperature. It is concluded that Nusselt number increases with increasing wind speed for all cases. Especially, it is showed that Nusselt number can be maximized when the tilt angle is 30o.
The objective of this paper is to describe the experimental and numerical investigation of the analysis of the heat transfer in a solar chemical reactor. These are compared about methane steam reforming process in the solar chemical reactor which was a volumetric absorber consisting of honeycomb and a multilayered catalyst supports. With this high operating temperature, convective heat loss, thermal fracture are important features for designing SCR. In order to estimate the system performance and to design the actual solar reactor with various conditions, CFD analysis was used in this study. The nickel oxide porous metal is inserted inside the solar chemical reactor to increase the conversion rate of the reforming reaction. Simulation has been carried out based on the experimental data. According to the simulation results, the optimum methane-steam mole ratio and thickness and numbers of catalyst supports were obtained.
In the fuel cell community it is well-known that a micro-porous layer (MPL) plays a crucial role in the water management of polymer electrolyte fuel cells (PEFCs), and thereby, significantly stabilizes and improves cell performance. In this paper, a numerical MPL model is developed and embodied with comprehensive, multi-dimensional, multi-phase fuel cell models that were developed earlier to discover the exact roles of MPLs,. The effects of different porous properties and liquid-entry pressures between an MPL and a gas diffusion layer (GDL) are examined via fully three-dimensional numerical simulations. Discontinuity in liquid saturation at the GDL/MPL interface is captured by the model when the differences in pore properties and wettability between the MPL and GDL are taken into account without considering variation in the liquid-entry pressures. However, the simulation of this case fails to capture the beneficial effects of an MPL on cell performance, predicting even lower performance than the case of no MPL. On the other hand, when a high liquid-entry pressure in an MPL is additionally considered, the numerical MPL model predicts liquid-free MPL and successfully demonstrates the phenomenon that the high liquid-entry pressure of the MPL prevents any liquid water from entering the MPL. Consequently, it is found from the simulation results that the liquid-free MPL significantly enhances the back-flow of water across the membrane into the anode, which, in turn, helps to avoid membrane dehydration and alleviate the level of GDL flooding. As a result, the model successfully reports the beneficial effects of MPLs on PEFC performance and predicts higher performance in the presence of MPLs (e.g., an increase of 67 ㎷ at 1.5 A ㎝-2). This study provides a fundamental explanation for MPL functions and quantifies the influence of MPL’s porous properties and the liquid-entry pressure on water transport and cell performance.
본 연구는 전라남도 11개 시군이 각각 추진하고 있는 스포츠관광자원 및 사업현황을 분석하여, 전라남도를 국제적인 관광지로 발돋움시키기 위한 체계화, 전략화, 집중화한 권역별 스포츠 관광자원의 사업화를 위한 구체적인 마케팅 전략을 제시하는데 목적이 있다. 이와 같은 연구 목적 달성을 위해 관광관련 학회, 공사, 협회 전문가와 전라남도 11개 시·군의 공무원, 현장전문가, 연구자 등을 연구 대상으로 하였으며, 개방형 설문조사와 심층면담, 전문가 회의 등을 통해 범주화 분석을 통해 자료를 수집하였다. 자료 수집은 현황조사를 시작으로 6단계 절차를 거쳐 수행되었다. 자료분석은 주제별로 분류하여 내용 분석을 실시하였다. 도출된 연구결과를 요약하면 다음과 같다. 첫째, 각 지자체에서 활용 가능한 최적의 스포츠관광자원을 도출하기 위하여, 설문조사를 실시하여 지자체별 비교우위 스포츠관광자원과 관련된 일반관광자원을 총 10개(관광지, 대표축제, 음식, 테마파크, 기후환경, 전통민속놀이, 인조 시설물, 캠핑장, 유휴자원)의 범주로 도출하였다. 둘째, 각 지자체 활용 가능한 일반관광자원의 10개 범주를 우선순위 하였으며, 지역의 관광지, 대표축제, 자연환경, 음식, 테마파크, 기후환경 순으로 나타났다. 셋째, 각 지자체가 보유한 스포츠관광자원 현황을 파악한 결과 지자체별로 스포츠관광자원(스포츠이벤트, 스포츠시설, 특화된 스포츠, 대표 프로스포츠, 전지훈련환경, 스포츠테마, 교육시설)을 보유하고 있으며, 지자체별로 스포츠관광자원의 보유 유무와 활용하고 있는지에 대한 결과를 도출하였다. 넷째, 전라남도 스포츠관광자원으로 활용 가능한 일반관광자원을 도출하였다. 다섯째, 전라남도 스포츠관광자원 활용자원에 대한 전략방안을 도출하였다. 여섯째, 전라남도 우수 스포츠관광자원의 종합연계전략을 광주 근교권, 동부권, 서남권, 중남부권 등 4개 권역으로 나누어 지역 특색에 맞는 연계전략을 제시하였다. This study analyzed the current status of sports tourism resources and projects promoted by 11 cities and counties in Jeollanam-do, and proposes a specific marketing strategy for the commercialization of systematized, strategic, and centralized sports tourism resources in order to develop Jeollanam-do into an international tourist destination. Achieving the purpose of the study, two types of research methods that are Delphi survey and open questionnaire survey are adopted, and then the survey results are analysed and classified into three categories and six stages. The results are as follow. First, in order to derive the optimal sports tourism resources that can be used in each local government, a survey was conducted to extract sports tourism resources with comparative advantage by local governments. Second, The analysis of general tourism resources through the advice of experts showed a total of 10 categories and organized into 123 sentences. Third, as a result of grasping the current status of sports tourism resources possessed by each local government, each local government has sports tourism resources and derived the contents used. Fourth, general tourism resources available for sports tourism resources were presented. Fifth, strategic plans for utilization of the sports tourism resources in Jeollanam-do are suggested. Sixth, the comprehensive marketing plans for outstanding sports tourism resources in Jeollanam-do provinces are proposed.
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 $LaNi_5$ 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.