• Structural Engineering and Mechanics
• /
• v.25 no.4
• /
• pp.445-466
• /
• 2007

As the LNG (Liquefied Natural Gas) tank contains cryogenic liquid, realistic thermal analyses are of a primary importance for a successful design. The structural details of the LNG tank are so complicated that some strategies are necessary to reasonably predict its temperature distribution. The proposed heat transfer model can consider the beneficial effects of insulation layers and a suspended deck on temperature distribution of the outer concrete tank against cryogenic conditions simply by the boundary conditions of the outer tank model. To this aim, the equilibrium condition or heat balance in a steady state is utilized in a various way, and some aspects of heat transfer via conduction, convection and radiation are implemented as necessary. Overall thermal analysis procedures for the LNG tank are revisited to examine some unjustifiable assumptions of conventional analyses. Concrete and insulation properties under cryogenic condition and a reasonable conversion procedure of the temperature-induced nonlinear stress into the section forces are discussed. Numerical examples are presented to verify the proposed schemes in predicting the actual temperature and stress distributions of the tank as affected by the cryogenic LNG for the cases of normal operation and leakage from the inner steel tank. It is expected that the proposed schemes enable a designer to readily detect the effects of insulation layers and a suspended deck and, therefore, can be employed as a useful and consistent tool to evaluate the thermal effect in a design stage of an LNG tank as well as in a detailed analysis.

• Journal of the Korea Safety Management & Science
• /
• v.12 no.3
• /
• pp.121-128
• /
• 2010

This is to show some basic data for introducing both circulated aggregate and recycled powder producing waste concrete. Standard-mixing design for 24MPa has been basically used and added and replaced normal aggregate with recycled powder made of waste concrete. In addition, polycarboxylate high-range water reducing agent has been used because recycled powder is missing adhesive strength and it is not compare with cement's adhesive strength. Compressive strength with powder mixture of 2%, 4%, 6%, 8%, and 10% has been decreased down to 80% of normal concrete material strength without recycled powder mixture. $200^{\circ}C$, $400^{\circ}C$ and $600^{\circ}C$ heated concrete were compressively tested in order to find out concrete strength resistant to high temperature. heat capacity was also tested, based on the expectancy of its low conductivity. In addition, thermal conduction test was tested in order to find out concrete insulation. According to this test, when concrete was tested by fire resistance, it using the circulation aggregate was same resulted by concrete using the natural aggregate. also, recycle powder was not effecting insulation performance. but it is fit to standard on concrete insulation of building law.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.4
• /
• pp.265-271
• /
• 2014

304L stainless steel sheets are used as a primary barrier for the insulation of membrane-type liquefied natural gas(LNG) carrier cargo containment system. 304L stainless steel is a transformation-induced-plasticity(TRIP) steel that exhibits complex material behavior, because it undergoes phase transformation during plastic deformation. Since the TRIP behavior is very important mechanical characteristics in a low-temperature environment, significant amounts of data are available in the literature. In the present study, a uniaxial tensile test for 304L stainless steel was performed to investigate nonlinear mechanical characteristics. In addition, a viscoplastic model and damage model is proposed to predict material fractures under arbitrary loads. The verification was conducted not only by a material-based comparative study involving experimental investigations, but also by a structural application to the LNG membrane of a Mark-III-type cargo containment system.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.2
• /
• pp.169-176
• /
• 2020

There is a growing interest in hydrogen energy utilization since an alternative energy development has been demanded due to the depletion of fossil fuels. Hydrogen is produced by the reforming reaction of natural gas and biogas, and the electrolysis of water. An solid oxide electrolyte cell (SOEC) is reversible system that generates hydrogen by electrolyzing the superheated steam or producing the electricity from a fuel cell by hydrogen. If the water can be converted into steam by waste heat from other processes it is more efficient for high-temperature electrolysis to convert steam directly. The reasons are based upon the more favorable thermodynamic and electrochemical kinetic conditions for the reaction. In the present study, steam at over 180℃ and 3.4 bars generated from a boiler were converted into superheated steam at over 700℃ and 3 bars using a cylindrical steam superheater as well as the waste heat of the exhaust gas at 900℃ from a solid refuse fuel combustor. Superheated steam at over 700℃ was then supplied to a high-temperature SOEC to increase the hydrogen production efficiency of water electrolysis. Computational fluid dynamics (CFD) analysis was conducted on the effects of the number of 90° elbow connector for piping, insulation types and insulation layers of pipe on the exit temperature using a commercial Fluent simulator. For two pre-heater injection method of steam inlet and ceramic wool insulation of 100 mm thickness, the highest inlet temperature of SOEC was 744℃ at 5.9 bar.

• Journal of the Society of Naval Architects of Korea
• /
• v.51 no.6
• /
• pp.495-502
• /
• 2014

Glass-reinforced polyurethane foam (R-PUF) is widely used as the primary and secondary insulation of Mark-III type liquefied natural gas (LNG) cargo system. And, polyurethane foam (PUF) and polyisocyanurate foam (PIR) are often used for insulation of onshore structures or LNG storage and pipeline system. These polymeric foam materials are known for the characteristics that mechanical properties are dependent on strain rate and temperature. In this study, compression tests for R-PUF, PIR, and PUF were carried out for the estimation of mechanical behaviors under the cryogenic environment. The range of thermal condition was from room temperature to 110K and strain rates were $10^{-3}s^{-1}$ and $10^{-4}s^{-1}$. The test results were analyzed based on the conditions of strain-rate and temperature.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.9
• /
• pp.117-123
• /
• 2009

Recently, the failures of electrical equipment have been reduced due to the improvement of its quality and the advance of operation techniques but the failure rates caused by natural disasters such as wind and lightning have been increased. To reduce the failures due to lightning, it is necessary for insulation design of transmission lines to be done, effectively. Also the analysis on the lightning characteristics is essential to the effective insulation design. In this paper, we describe lightning distribution, multiplicity, IKL(Iso-Keraunic Level) and amplitude distribution of lightning current base on the lightning data by KLDNet.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.10
• /
• pp.705-710
• /
• 2012

This study aims to analyse changes of inner temperature of PVS(Passive ventilation skin) and heat recovery when it has ventilation of air through PVS using numerical simulation in the winter condition. Results are as follows. 1) In case of the air inflows through PVS, change of inner temperature of PVS is lower than in case of the air flows inner space to out space, by dynamic insulation. 2) It was identified that the temperature gradient of PVS were bigger by increases of ventilation amount. To reduce ventilation load, heat transfer efficiency at the inner side of PVS is important and what performance of insulation at the inner side of PVS secure helps to improve heat performance of all PVS.

• Journal of the Korean Institute of Rural Architecture
• /
• v.17 no.1
• /
• pp.9-18
• /
• 2015

The purpose of this study is to analyze the usage of eco-friendly elements in Korean traditional architecture to evaluate Hanok(Unjoru and Jinwondang) according to Green Building Certification Criteria(G-SEED). The results of this study were as follows; Unjoru and Jinwondang was not enough to obtain certification points. From Site usage and Traffic category, Jinwondang gets more points than Unjoru. It's because Jinwondang is located in downtown Seoul, so it gets more points of traffic and neighborhood facility. From Energy and Environmental Pollution category, Jinwondang gets more points of energy performance than Unjoru, too. It's because Jinwondang secured insulation performance of wall and windows using insulator and glass. From Resources category, Unjoru gets more points than Jinwondang. It shows that modern Hanok was limited using natural resources. From Ecological Environments category, Jinwondang is located urban area, it's difficult to secure the open space, so Unjoru gets more points than Jinwondang. If Modern Honok installs a system that can getting point and secure insulation performance, it will be certificated according to G-SEED.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.3
• /
• pp.393-400
• /
• 2003

Excessive generation of BOG during the LNG transportation not only causes the severe financial loss but also leads to the unexpected disaster. Therefore, the carrier cargo insulating interior LNG should be carefully designed based upon an accurate heat transfer analysis. However. it is not simple to analyze heat transfer of LNG cargo, because it is in a complex insulation structure and LNG carrier experiences a complicated heat transfer according to various kinds of voyage conditions. In this paper, we carried out the transient finite element heat transfer analysis for a cargo of Mark-111 membrane-type LNG carrier during laden voyage, and we compared heat transfer rates between considering natural convection and considering conduction. For this goal, we developed a PCL program incorporating with a commercial MSC/NASTRAN FEM code.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.2
• /
• pp.213-221
• /
• 1985

Two dimensional laminar natural convection in a rectangular enclousure composed of a hot bottom wall, a partially cold side wall and insulated walls except the above walls was studied by numerical analysis and also by esperiments. In the experiments, the temperature distributions in the enclosure and Nusselt number distribution along the hot and cold walls were obtained by the use of Mach-Zehnder interferometer. At first, numerical analysis with the boundary conditions of the experimental apparatus was performed and the comparison of the results of the numerical and the experimental results validated the numerical model good ennough. Heat transfer characteristics were investigated by applying the verified numerical model with the parameters, i.e. Grashof number, aspect ratio, position of cold plate and insulation condition. The results showed the optimal conditions of temperature distribution and the position of cold wall, and the characteristics of insulation materials.