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촉매유효도 상관식에 기반한 마이크로채널형 수증기/메탄 개질기의 1차원 해석모델 개발 : Development of One-Dimensional Calculation Model for Microchannel Steam/Methane Reformers based on Catalyst Effectiveness Factor Correlations
| DC Field | Value | Language |
|---|---|---|
| dc.contributor.advisor | 김찬중 | - |
| dc.contributor.author | 이대훈 | - |
| dc.date.accessioned | 2023-11-20T04:17:28Z | - |
| dc.date.available | 2023-11-20T04:17:28Z | - |
| dc.date.issued | 2023 | - |
| dc.identifier.other | 000000178366 | - |
| dc.identifier.uri | https://hdl.handle.net/10371/196310 | - |
| dc.identifier.uri | https://dcollection.snu.ac.kr/common/orgView/000000178366 | ko_KR |
| dc.description | 학위논문(석사) -- 서울대학교대학원 : 공과대학 기계공학부, 2023. 8. 김찬중. | - |
| dc.description.abstract | 수소의 운반 및 저장에 소요되는 비용 및 위험성을 줄이기 위한 분산형 수소생산시스템에 관한 연구가 활발하게 이뤄지고 있다. 하지만 소형화로 인해 발생되는 효율 감소 및 안정성의 문제로 인해 최적화가 요구되고 이를 위한 높은 정확도의 해석이 필수적이다. 정확한 공정 예측을 위해 전산유체역학에 기반한 해석모델 개발이 주로 이뤄졌으나 개질 과정 예측을 위해 많은 격자가 배치되어 해석에 소요되는 비용이 상당히 높다는 한계점이 있다.
본 연구에서는 분산 발전용 연료전지의 개질시스템에 적합한 저압 개질 조건(1~3bar)에서의 소형 마이크로채널 수증기/메탄 개질기를 효율적으로 해석할 수 있는 간략화된 1차원 해석모델을 개발하였다. 촉매유효도 상관식을 도입하여 다공성 촉매층 내부의 복잡한 반응/확산 문제를 간단하게 계산하였고 개질기 내부의 온도 및 농도는 에너지 보존과 화학종 보존을 고려해 계산하는 방식을 취하였다. 제시된 모델은 개질 과정을 상세히 고려한 CFD 해석모델과의 비교를 통해 신뢰성을 입증하고 파라미터 연구를 진행하여 다양한 공정 변수가 개질 과정에 미치는 영향을 조사하였다. 추가적으로 각 영역에 대한 개별적인 결과를 계산할 수 있는 1차원 상세모델을 개발하여 제시된 간략화모델의 한계점을 극복하고 정확도를 향상시키기 위한 연구가 진행되었다. 개발된 2개의 1차원모델은 CFD 해석모델과의 해석 시간을 비교하여 실효성을 증명하였다. | - |
| dc.description.abstract | Distributed hydrogen production systems are being actively studied to reduce the cost and risk of hydrogen transportation and storage. However, miniaturization of these systems can lead to decreased efficiency and stability, which requires optimization. High-accuracy analysis is essential for this.
In this study, a simplified 1D analysis model was developed that can efficiently analyze a small microchannel steam/methane reformer under low-pressure reforming conditions (1-3 bar) suitable for the reforming system of distributed power generation fuel cells. The catalyst efficiency correlation was introduced to simply calculate the complex reaction/diffusion problem inside the porous catalyst layer, and the temperature and concentration inside the reformer were calculated by energy conservation and mass conservation. The presented model was validated through comparison with a CFD analysis model that considered the reforming process in detail, and a parametric study was conducted to investigate the influence of various operating and design conditions on the reforming process. In addition, a 1D detailed model that can calculate individual results for each region was developed to overcome the limitations of the presented simplified model and improve accuracy. The two 1D models developed were proved to be effective by comparing the CPU time with the CFD analysis model. The results of this study suggest that the 1D analysis model is a promising tool for the optimization of distributed hydrogen production systems. | - |
| dc.description.tableofcontents | 목 차
요 약 i 목 차 ii List of Tables iii List of Figures iv Nomenclatures vi 제 1 장 서론 01 1.1 연구 배경 01 1.2 연구 목표 06 제 2 장 1차원 간략화모델 08 2.1 모델 설명 08 2.2 모델 검증 22 2.3 파라미터 연구 30 2.4 결론 43 제 3 장 1차원 상세모델 45 3.1 모델 설명 45 3.2 모델 검증 52 3.3 모델 비교 57 제 4 장 결론 65 Appendix 67 References 69 Abstract 72 List of Tables Table 2.1 Reaction rate constants 12 Table 2.2 Adsorption coefficient 12 Table 2.3 Equilibrium costants 12 Table 2.4 Physical properties 21 Table 2.5 Operating conditions 21 Table 3.1 Summary of methane conversion ratio from parametric studies of varying inlet velocity and convective heat transfer coefficient 58 Table 3.2 Summary of hydrogen production from parametric studies of varying operating conditions 64 List of Figures Figure 1.1 Steam/methane reforming process in microchannel reformer. 05 Figure 2.1 Schematics of an examplary microchannel steam/methane reformer considered in this study: (a) physical domain and (b) its discretized calculation grid[23] 08 Figure 2.2 Schematics of the simplified 1-D model 13 Figure 2.3 Comparison of temperature along the axial coordinate between calculation results of simplified 1D model and CFD simulation results at standard operating conditions[23] 23 Figure 2.4 Comparison of mole fractions along the axial coordinate between calculation results of simplified 1D model and CFD simulation results at standard operating conditions[23] 23 Figure 2.5 Comparison of reaction rate along the axial coordinate between calculation results of simplified 1D model and CFD simulation results at standard operating conditions[23] 25 Figure 2.6 Effect of inlet velocity on methane conversion ratio along the axial coordinate at standard operating conditions[23] 28 Figure 2.7 Effect of heat transfer coefficient on methane conversion ratio along the axial coordinate at standard operating conditions[23] 28 Figure 2.8 Effect of operating (a) pressure, (b) inlet temperature and (c) S/C ratio on methane conversion ratio along the axial coordinate at standard operating conditions 31 Figure 2.9 Effect of operating (a) pressure, (b) inlet temperature and (c) S/C ratio on temperature along the axial coordinate at standard operating conditions 32 Figure 2.10 Effect of operating (a) pressure, (b) inlet temperature and (c) S/C ratio on hydrogen production at standard operating conditions 33 Figure 2.11 Effect of (a) channel height, (b) washcoat thickness and (c) reformer length on methane conversion ratio along the axial coordinate at standard operating conditions 37 Figure 2.12 Effect of (a) channel height, (b) washcoat thickness and (c) reformer length on temperature along the axial coordinate at standard operating conditions 38 Figure 2.13 Effect of (a) channel height, (b) washcoat thickness and (c) reformer length on hydrogen production at standard operating conditions 39 Figure 3.1 Schematics of an examplary microchannel steam/methane reformer considered in this study: (a) physical domain and (b) its discretized calculation grid[23] 45 Figure 3.2 Schematics of the detailed 1-D model 47 Figure 3.3 Comparison of (a) temperature and (b) mole fractions along the axial coordinate between calculation results of detailed 1D model and CFD simulation results at standard operating conditions 54 Figure 3.4 Effect of (a) inlet velocity and (b) heat transfer coefficient on methane conversion ratio along the axial coordinate at standard operating conditions 56 Figure 3.5 Validation of detailed 1D calculation model: reaction rate along the axial coordinate at standard operating conditions 59 Figure 3.6 Comparison of (a) temperature and (b) mole fractions along the axial coordinate between simplified 1D model calculation results and detailed 1D model calculation results at standard conditions 62 Figure A.1 CFD analysis model for microchannel type steam/methane reformer 67 Nomenclature Di,eff effectiveness diffusivity in the catalyst layer, m2/s Dij binary diffusivity of i j species pair, m2/s DK,i Knudsen diffusivity of species i, m2/s Dm,i effective diffusivity in the flow channel, m2/s dpore mean pore diameter, m Hch channel height, m h convective heat transfer coefficient, W/m2-K h _i total enthalpy of species i, J/mol h _(f,i) formation enthalpy of species i, J/mol Keq,j equilibrium constants for reaction j Ki adsorption coefficient of species i Kv viscous flow permeability, m 2 keff effective thermal conductivity, W/m-K Kj reaction rate constant for reaction, j Lch channel length, m Mi molecular mass of species i, kg/kmol Mnom,CH4 nominal methane diffusion rate, mol/s Ni molar flow rate of species i, mol/s pi partial pressure of species i, bar pt total pressure, bar Rg universal gas constant, 8.314 kJ/kmol-K Rnom,j nominal reaction rate of reaction j, mol/s Rj reaction rate of reaction j, mol/s rj reaction rate of reaction j, kmol/kgcat-h SC steam to carbon (S/C) ratio Si source for species i, mol/s T temperature, twc washcoat layer thickness, m tsub substrate layer thickness, m x coordinate, m xi mole fraction of species i Greek letters ρ_cat apparent catalyst density, kgcat/m 3 β_CH4 methane conversion ε porosity φ_j effective Thiele modulus for reaction j φ_j^* modified Thiele modulus for reaction j η_j effectiveness factor for reaction j τ tortuosity Subscripts and superscripts 0 inlet value at the washcoat surface c cell value ch channel cat catalyst eff effective i species index j reaction index k grid index ref reference s solid t total | - |
| dc.format.extent | vii, 73 | - |
| dc.language.iso | kor | - |
| dc.publisher | 서울대학교 대학원 | - |
| dc.subject | 수증기/메탄 개질기 | - |
| dc.subject | 1차원 해석모델 | - |
| dc.subject.ddc | 621 | - |
| dc.title | 촉매유효도 상관식에 기반한 마이크로채널형 수증기/메탄 개질기의 1차원 해석모델 개발 | - |
| dc.title.alternative | Development of One-Dimensional Calculation Model for Microchannel Steam/Methane Reformers based on Catalyst Effectiveness Factor Correlations | - |
| dc.type | Thesis | - |
| dc.type | Dissertation | - |
| dc.contributor.AlternativeAuthor | Lee Dae-Hoon | - |
| dc.contributor.department | 공과대학 기계공학부 | - |
| dc.description.degree | 석사 | - |
| dc.date.awarded | 2023-08 | - |
| dc.contributor.major | 열공학 | - |
| dc.identifier.uci | I804:11032-000000178366 | - |
| dc.identifier.holdings | 000000000050▲000000000058▲000000178366▲ | - |
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