RISS 검색 - 학위논문 상세보기

다국어 초록 (Multilingual Abstract)

In recent years, membrane distillation (MD) is an emerging technique proposed as an alternative to multistage flash (MSF), multi-effect distillation (MED), and reverse osmosis (RO). MD is one of the thermal separation technologies to produce distilled quality water from high salinity water that uses a hydrophobic membrane as a barrier between feed and permeated water. MD has many potential benefits such as theoretically 100% rejection for non-volatile impurities, low operating temperatures, no applied hydraulic pressure requirement less than RO. It is a technology that can reduce the problem of concentrated water discharge due to its high recovery rate, and has the advantage of using renewable energy as a heat source. Nevertheless, the MD commercialization is not much enough because it is still evaluated that the economic feasibility is insufficient compared to the conventional processes. Therefore, various studies are being conducted to MD commercialize, which can be divided broadly into two main categories: 1) Energy efficiency improvement, 2) Membrane fouling/performance testing.
In this thesis, unlike previous studies that relied on experiment results, computational fluid dynamics (CFD) simulations were studied to understand the heat/mass transfer and confirm the movement of foulants in the direct contact membrane distillation (DCMD). Model accuracy was validated by comparing lab-scale results with CFD simulation results. The hydrodynamic condition, temperature polarization, exergy destruction, and membrane fouling inside the module were confirmed through the verified model. Finally, it was intended to develop a performance evaluation method and guideline for MD, which can improve energy efficiency inside the module and retard membrane fouling.

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국문 초록 (Abstract)

최근 막 증발법이 다단증발법, 다중효용증발법 및 역삼투의 대안으로 제안되어 새롭게 부각되고 있다. 막 증발법은 유입수와 여과수 사이의 장벽으로 소수성 막을 이용함으로써 고염수로부터 증류된 양질의 물을 생산하기 위한 열 분리 기술 중 하나이다. 막 증발법은 휘발성이 없는 이온성 물질을 이론적으로 100% 제거할 수 있으며, 기존 증발법에 비하여 비교적 낮은 온도에서 운전되며, 역삼투에 비하여 낮은 압력에서 작동할 수 있다는 장점을 가진다. 또한 회수율이 높아 농축수 배출 문제를 줄일 수 있는 기술이며, 신재생에너지를 열원으로 활용할 수 있는 장점이 있다.
이와 같은 장점에도 불구하고, 기존의 증발법 및 역삼투법에 비하여 경제성이 부족하다는 평가를 받고 있기 때문에 상용화가 활발하게 진행되고 있지 못하고 있다. 따라서, 막 증발법을 상용화하기 위한 다양한 연구들이 진행되고 있으며, 크게 두가지 1) 에너지 효율 개선, 2) 막 오염/성능 평가 연구로 나눌 수 있다.
본 논문에서는 실험에 의존했던 기존 연구와는 달리 직접 접촉식 막 증발법 모듈 내부에서 열/물질 전달의 기본 이해와 막을 오염시키는 물질의 이동을 파악하기 위하여 전산 유체 역학 시뮬레이션의 적용을 연구하였다. 실험실 규모 결과와 전산 유체 역학 시뮬레이션 결과 비교를 통하여 모델의 정확도를 검증하였고, 검증된 모델을 통하여 모듈 내부 유체 흐름, 온도 분극 현상, 엑서지 손실, 막 오염 현상 원인을 확인하였다. 최종적으로, 모듈 내부에서 에너지 효율을 개선하고 막 오염 현상을 지연시킬 수 있는 막 증발법 모듈 평가 및 가이드라인을 개발하고자 하였다.

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최근 막 증발법이 다단증발법, 다중효용증발법 및 역삼투의 대안으로 제안되어 새롭게 부각되고 있다. 막 증발법은 유입수와 여과수 사이의 장벽으로 소수성 막을 이용함으로써 고염수로부...

목차 (Table of Contents)

CHAPTER 1. Introduction 1
1.1. Research background 2
1.2. Thesis scope and objectives 5
1.3. Thesis organization 8
CHAPTER 2. Literature review 10

CHAPTER 1. Introduction 1
1.1. Research background 2
1.2. Thesis scope and objectives 5
1.3. Thesis organization 8
CHAPTER 2. Literature review 10
2.1. Membrane distillation 11
2.2. Limitation in MD 23
2.2.1. Membrane wetting 23
2.2.2. Membrane fouling 26
2.2.3. Temperature polarization 29
2.3. Modeling approach 30
2.3.1. Computational fluid dynamics 30
2.3.2. Momentum transfer 31
2.3.3. Heat transfer 32
2.3.4. Mass transfer 33
CHAPTER 3. Exergy analysis of a direct contact membrane distillation system based on computational fluid dynamics 35
3.1. Introduction 36
3.2. Theory 39
3.3. Materials and Methods 41
3.4. Results and discussions 44
3.4.1. Verification of the CFD model 44
3.4.2. Velocity distribution 46
3.4.3. Temperature distribution 48
3.4.4. Vapor pressure and flux 50
3.4.5. Temperature polarization phenomenon 52
3.4.6. Exergy destruction profiles 55
3.4.7. Exergy flow analysis 62
3.5. Conclusions 64
CHAPTER 4. Combination of computational fluid dynamics and design of experiments to optimize modules for direct contact membrane distillation 66
4.1. Introduction 67
4.2. Theory 69
4.2.1. Response surface methodology 71
4.2.2. Graphical optimization 73
4.2.3. Numerical optimization 73
4.3. Materials and Methods 75
4.4. Results and discussion 78
4.4.1. CFD model validation 78
4.4.2. CFD simulation for a lab-scale module 80
4.4.3. Response surface methodology modeling 86
4.4.4. Effect of module dimensions on flux 92
4.4.5. Effect of module dimensions on the performance ratio 94
4.4.6. Effect of module dimensions on the permeate-to-feed ratio 96
4.4.7. Graphical optimization of module dimensions 98
4.4.8. Numerical optimization of module dimensions 101
4.5. Conclusion 105
CHAPTER 5. Inorganic fouling mitigation using the baffle system in direct contact membrane distillation 107
5.1. Introduction 108
5.2. Theory 111
5.3. Materials and Methods 113
5.4. Results and discussion 121
5.4.1. Validation of CFD model 121
5.4.2. CFD Analysis of hydrodynamic conditions non-baffled and baffled modules 123
5.4.3. Experimental results: Initial flux in non-baffled and baffled modules 131
5.4.4. Experimental results: Scale formation in non-baffled and baffled modules 134
5.5. Conclusion 141
CHAPTER 6. Conclusion 143
6.1. Conclusion 144
6.2. Future work 147
6.3. Publications 149
REFERENCES 153
국문 초록 182

참고문헌 (Reference)

1 T. Sarpkaya, "Computational methods with vortices ?", 1989

2 J. Zhang , S. Gray, "Modelling heat and mass transfers in DCMD using compressible membranes", 387 (, 2012

3 B. Li , K.K . Sirkar, "Novel membrane and device for vacuum membrane distillation-based desalination process", 257, 2005

4 M. Gryta, "The application of membrane distillation for broth separation in membrane bioreactors", 2, 2016

5 M. Rezakazemi, "CFD simulation of seawater purification using direct contact membrane desalination ( DCMD ) system", 443, 2018

6 Y . Park , S. Lee ,, "Analysis of thermal energy efficiency for hollow fiber membranes in direct contact membrane distillation", 24 (, 2019

7 S.-M. Park , S. Lee, "Influence of hydraulic pressure on performance deterioration of direct contact membrane distillation ( DCMD ) process", 9 (, 2019

8 Z. Wang , S. Lin, "Membrane fouling and wetting in membrane distillation and their mitigation by novel membranes with special wettability", 112 (, 2017

9 J. Kumar , A. Bansal, "Photocatalytic degradation in annular reactor : Modelization and optimization using computational fluid dynamics ( CFD ) and response surface methodology ( RSM )", 1 (, 2013