해저지반 열전도율 산정 및 다층지반의 열전도율을 고려한 해저배관의 총괄열전달계수 식 제안 = Experimental and Numerical Method for Thermal Conductivity of Offshore Sediment and Proposed OHTC Formula for Offshore Pipelines Taking Multi-layered Sediment

다국어 초록 (Multilingual Abstract)

Subsea pipelines are designed to transport mixtures of oil, gas and their
associated impurities from the wellhead that can be in excess of
approximately as high as 100℃ temperature, while the external
temperature maybe in the range of 5℃. Heat can be lost from the subsea
pipeline which contains high temperature fluid to the surrounding
environment. It is important that the pipeline must be designed to ensure
that the heat loss is small enough to maintain flow assurance, unwanted
deposition of hydrate and wax, which occurs at a critical temperature of
about 40℃. Therefore it is essential to know heat loss of subsea pipeline
in various circumstance. This paper presents thermal conductivity of
offshore sediments using laboratory model test and numerical analysis for
various soil samples. After calculate thermal conductivities, this paper
propose a OHTC(Overall heat transfer coefficient) formula considering
multi-layed soil using calculated thermal conductivity of soil samples for
more precise OHTC estimation.

국문 초록 (Abstract)

해저배관은 오일, 가스 그리고 불순물의 혼합물을 유정에서 운송할 수 있
도록 고안되었으며, 100℃전후의 높은 온도의 유체를 수송한다. 하지만 높은
온도의 수송유류와 반대로 해저배관을 둘러싸고 있는 주변 환경의 온도는
5℃정도의 낮은 온도를 유지하고 있으며 이로 인해 해저배관은 열손실이 발
생한다. 따라서 해저배관의 열손실을 최소화 하는 것 즉, 수송유류가 왁스
(Wax)나 고상염(Hydrate) 같은 침전물이 생성되는 온도인 40℃ 이하로 떨어
지는 것을 방지해 유동안정성을 확보하는 것은 해저배관 설계에 있어 가장
중요한 부분이다. 그러므로 해저배관 주변 환경 즉 해수, 해저지반의 영향에
의한 해저배관의 열손실의 정도를 나타내는 총괄열전달계수를 계산하여 설
계에 반영하는 것은 중요하다. 본 논문에서는 실내모형실험 및 CFD해석의
검토를 통해 해저지반의 열전도율을 여러 가지 샘플을 통해 산정하였으며,
산정된 열전도율을 토대로 다층지반을 구성하여 다층지반의 다양한 열전도
율을 고려한 해저배관의 총괄열전달계수(OHTC)식을 제안하였다.

목차 (Table of Contents)

• List of Tables ··············································································································· ⅳ
• List of Figures ············································································································· ⅴ
• Abstract ························································································································· ⅶ
• 초록 ································································································································ ⅸ
• 제 1 장 서 론 ·············································································································· 1
• 1.1 연구 배경 ······································································································ 1
• 1.2 연구 동향 ······································································································ 2
• 1.2.1 해저지반 열전도율 산정 ································································· 2
• 1.2.2 다층지반을 고려한 총괄열전달계수식 제안 ······························· 3
• 제 2 장 해저지반 열전도율 산정 실내모형실험 ·················································· 5
• 2.1 실내모형실험 방법 ······················································································ 5
• 2.1.1 실내모형실험 장치 ··········································································· 5
• 2.1.2 실내모형실험 측정 장비 ································································· 7
• 2.1.3 실내모형실험 방법 ··········································································· 8
• 2.1.4 실내모형실험 시료 ········································································· 10
• 2.2 실내모형실험 결과 ···················································································· 12
• 2.2.1 혼합시료 열전도율 결과 ······························································· 12
• 2.2.2 보링시료 열전도율 결과 ······························································· 18
• 제 3 장 해저지반 열전도율 산정 유한요소해석 수행결과 및 분석 ·············· 20
• 3.1 유한요소해석 타당성 검토 ······································································ 20
• 3.2 유한요소해석 방법 ···················································································· 22
• 3.2.1 모델링 및 격자생성 ······································································· 23
• 3.2.2 유한요소해석 지배방정식 ····························································· 24
• 3.2.3 유한요소해석 초기조건 및 경계조건 ········································· 25
• 3.2.4 유한요소해석 항목 및 재료 물성치 ··········································· 25
• 3.3 실내모형실험 및 유한요소해석 결과비교 및 분석 ···························· 26
• 3.3.1 유한요소해석 및 실내모형실험 결과 ········································· 26
• 3.3.2 유한요소해석 및 실내모형실험 결과 비교 ······························· 27
• 제 4 장 다층지반의 열전도율을 고려한 총괄열전달계수식 제안 ·················· 30
• 4.1 총괄열전달계수 이론식 검토 ·································································· 30
• 4.1.1 총괄열전달계수 개념 ····································································· 30
• 4.1.2 매립된 해저배관의 총괄열전달계수 이론식 ····························· 30
• 4.2 다층지반 열전도율 적용 이론 및 식 제안 ·········································· 36
• 4.2.1 Fourier의 열전도법칙 ····································································· 36
• 4.2.2 해저지반 등가 열전도율 산정 ····················································· 38
• 4.2.3 다층지반을 고려한 총괄열전달계수 계산식 ····························· 39
• 제 5 장 유한요소해석을 통한 제안 식 검증 ······················································ 42
• 5.1 유한요소해석 방법 ······················································································42
• 5.1.1 유한요소해석 방법 ········································································· 42
• 5.1.2 유한요소해석 지배방정식 ····························································· 44
• 5.1.3 유한요소해석 초기조건 및 경계조건 ········································· 46
• 5.1.4 수치해석 결과를 이용한 총괄열전달계수 계산 이론 ··········· 48
• 5.2 유한요소해석 케이스 ·············································································· 49
• 5.2.1 해석케이스 1 : High Biot number ·············································· 50
• 5.2.2 해석케이스 2 : Intermediate Biot number ································ 51
• 5.2.3 해석케이스 3 : Law Biot number ··············································· 52
• 제 6 장 유한요소해석 수행결과 및 분석 ···························································· 53
• 6.1 유한요소해석 타당성 검토 ······································································ 53
• 6.2 유한요소해석 결과 및 제안 식 계산결과 비교분석 ·························· 55
• 6.2.1 해석케이스 1 : High Biot Number ·············································· 55
• 6.2.2 해석케이스 2 : Intermediate Biot Number ······························· 58
• 6.2.3 해석케이스 3 : Law Biot Number ·············································· 61
• 제 7 장 결 론 ············································································································ 64
• Nomenclature ············································································································· 66
• 참고문헌 ······················································································································ 68