흡·탈착 시간 재분배를 통한 흡착식 냉동기 성능 최적화에 관한 연구 = A Study on the Optimization of Performance of Adsorption Chiller by Reallocation of Adsorption and Desorption Time

국문 초록 (Abstract)

현대사회에서 지구 온난화로 인해 하절기는 물론 동절기까지 냉방의 수요가 급격하게 증가하고 있으며, 그로인해 기존에 사용되던 냉동기가 환경에 미치는 문제점이 대두되고 있다. 증기 압축식 냉동기의 경우에는 많은 전력을 필요로 하며 냉매인 프레온 가스는 지구온난화를 앞당겨 환경에 악영향을 준다. 따라서 냉매로써 물, 메탄올, 암모니아 등을 사용하는 친환경적 냉동기인 흡착식 냉동기에 대한 관심이 많아지고 있으며, 그 수요에 따라 많은 연구가 진행되고 있다.
흡착식 냉동기는 가역반응인 흡착 및 탈착 반응을 이용한 저온(50℃~90℃) 열 구동 냉동 열기관이며, 낮은 성능계수로 인한 큰 시스템 부피로 보급이 지연되고 있는 상황이다. 본 연구는 CFD(computational fluid dynamics)를 이용한 냉동기 해석을 통해 흡착식 냉동기의 단점인 큰 시스템 크기를 극복하여 성능지표인 COP(coefficient of performance)와 SCP(specific cooling capacity)의 향상을 이루어내 최종적으로 흡착식 냉동기의 상용화에 이바지 하고자 한다.
첫째, 해석모델의 정확성을 증가시키기 위한 방안으로 기존의 모델에 증발기와 응축기를 포함한 새로운 모델을 개발하고 실험과 비교하여 그 타당성을 검증하였다. 증발기와 응축기의 열 및 물질교환 거동이 흡착 배드에 미치는 영향까지 고려할 수 있는 바람직한 해석모델을 제안하였다. 나아가, 성능계수와 별개로 증발기의 출구 냉수온도의 거동까지 예측하여 흡착식 냉동기의 실효성을 검증하여 수치해석 결과 예측의 신뢰성을 높이고자 한다.
둘째, 흡착식 냉동기의 흡착 및 탈착시간을 재분배를 통하여 흡착체의 특성에 유리한 흡·탈착 시간을 정량적으로 제시하였다. 또한, 이러한 시간 재분배가 흡착량 또는 흡착 배드 내부의 온도와 같은 열 및 물질전달 특성에미치는 영향을 분석하였다.
셋째, 앞서 언급한 두 가지 연구를 바탕으로 흡착식 냉동기의 열 및 물질전달을 가장 잘 이해할 수 있는 증발기와 응축기를 포함한 3-배드 흡착식냉동기 해석 모델을 제시하였다. 3-배드 흡착식 냉동기는 다변하는 일일 냉동부하에 유연하게 대응하기 쉬우며 증발기 출구 냉수온도의 범위가 비교적일정한 시스템이다. 기존 2-배드 냉동기와 대비해 가지는 여러 강점을 바탕으로 앞으로 나아가야 할 향후 연구 방향성을 제시하고자 한다.

목차 (Table of Contents)

• 목차
• 제 1장 서론 ··············································································································1
• 1.1 연구배경 및 목적···························································································1
• 1.2 해석모델 연구 동향 ·····················································································3
• 1.3 시간 재분배 연구 동향 ···············································································5
• 1.4 멀티 배드 연구 동향·····················································································6
• 1.5 연구 내용 ·······································································································7
• 제 2장 수치모델 ······································································································9
• 2.1 흡착식 냉동기 사이클 ·················································································9
• 2.2 흡착 배드 형상 ···························································································10
• 2.3 흡착제 종류 ·································································································11
• 2.4 가정 ···············································································································13
• 2.5 물질전달 방정식 ·························································································13
• 2.6 열전달 방정식 ·····························································································16
• 2.7 초기조건 및 경계조건 ···············································································18
• 2.8 성능지표 ·······································································································19
• 제 3장 흡착식 냉동기 해석에서 증발기와 응축기의 영향 ··························21
• 3.1 지배방정식 ·····································································································21
• 3.2 해석 모델 검증 ·····························································································25
• 3.3 기존 해석 모델과 비교한 증발기와 응축기의 영향 ···························27
• 3.4 집중 용량 해석과 비교한 증발기와 응축기의 영향 ···························33
• 제 4장 흡착식 냉동기에서 흡착 및 탈착 시간 재분배 영향 ······················35
• 4.1 지배방정식 ···································································································35
• 4.2 해석 모델 검증 ··························································································· 35
• 4.3 Qeva 와 Qin의 거동 및 COP 와 SCP의 거동 ····································37
• 4.4 성능 변화에 대한 고찰 ·············································································39
• 4.5 온수 온도를 고려한 시간 재분배 ·····························································42
• 4.6 사이클 타임을 고려한 시간 재분배·························································43
• 제 5장. 3-배드 이상의 멀티배드 흡착식 냉동기 최적화 연구 ······················45
• 5.1 지배방정식······································································································45
• 5.2 해석모델 검증 ······························································································47
• 5.3 3-배드 흡착식 냉동기의 장점·····································································50
• 5.4 추후 연구 방향 ····························································································54
• 제 6장. 결론 ············································································································55
• 6.1 해석모델에서 증발기와 응축기의 영향 ···················································55
• 6.2 시간 재분배로 인한 최적화 ·······································································56
• 6.3 3-배드 냉동기의 최적화 ············································································57
• 참 고 문 헌 ············································································································58
• ABSTRACT ·················································································································63