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Numerical and experimental study on flow and heat transfer characteristics of cryogenic liquid in porous media : 다공성 매질을 통한 극저온 액체의 유동과 열적 특성에 대한 연구

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Authors
최성웅
Advisor
이우일
Major
공과대학 기계항공공학부
Issue Date
2013-02
Publisher
서울대학교 대학원
Keywords
Mark Ⅲ systemCCS (cargo containment system)glass woolpermeabilityliquefied nitrogenhull plateLNG (liquefied natural gas)thermal safetyductile-to-brittle transition temperatureComputational fluid dynamics (CFD).
Description
학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2013. 2. 이우일.
Abstract
The importance of fluid flow and heat transfer with a change in phase arises from the fact that many industrial processes rely on these phenomena for material processes and energy transfer. Examining fluid flow related to heat transfer with a change in phase involves multiphase flow analysis, which can be adapted to various applications. In particular, flow phenomena of a cryogenic liquid subjected to evaporation are of interest to understanding cryogenic liquid behavior in a porous structure.
One of the purposes of this study is to evaluate the flow and heat transfer of cryogenic liquid in porous media. An experimental investigation on the behavior of cryogenic liquid in porous media, glass wool, with various densities showed how the cryogenic liquid behaves in a porous structure. This study examined the thermophysical properties of glass wool with different bulk densities in terms of the temperature dependence and permeability behavior under different applied pressures. The experimentally determined thermal properties were used to examine the characteristics of the two main experimental results. Two distinct experiments showed the nonlinearity of the pressure distribution over distance increased as the bulk density of the glass wool increased, and the increase rate of pressure gradient became greater with the applied injection pressure. Simulation results were used to understand a cryogenic liquids flow in porous media, and were compared with experimental results. Numerical simulation showed good agreement with experiment results. The numerical approach presented in the paper would enable a more efficient analysis and better understanding of cryogenic liquids behavior in the porous structure.
Another purpose of this study is to develop and present numerical and experimental model for LNG leakage phenomenon in the porous structure to predict more reasonable thermal effect of LNG CCS hull structure when LNG is leaked through the porous media for damages and failures. Given that LNG cargo containment systems (CCS) operate in a range of environmental temperatures that includes cryogenic temperatures, thermal analysis should be carried out to determine thermal safety of the hull plate. Two phase mixture model which was verified with experiment of flow for the cryogenic liquid was adopted for LNG leakage phenomenon. The numerical parametric studies, flow and transient heat transfer analysis were presented with the scenario that LNG leaked into the insulation panel with different inlet pressure and defect size. In this scenario, thermal safety was evaluated with the criterion that the bottom hull plate part has the critical criterion that hull plate mild steel is vulnerable to the below a ductile-to-brittle transition temperature of -60 °C. With 2 mm diameter defect area, thermal safety can be maintained, however, over 5 mm diameter defect area, temperature of hull plate drops below -60 °C. Thermal penetration depth depends on the inlet pressure of LNG, though, the maximum penetration depth didnt exceed 30 % of hull thickness.
Language
English
URI
https://hdl.handle.net/10371/118315
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Mechanical Aerospace Engineering (기계항공공학부)Theses (Ph.D. / Sc.D._기계항공공학부)
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