• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.1-6
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• 1999

Nearshore and offshore pipelines are often applied to carry oil, gas, water and combined products. The thermal and pressure gradients of the fluid inside pipeline cause pipeline expansion. This expansion produces stress to connecting structures with pipeline. Should this stress exceeds the yield strength of connecting components or the allowable displacement of the system, a damage can occur. As most pipelines contain hazardous and toxic fluids, the damage usually leads to fatal accidents involving great economic loss as well. Even subsea pipelines can be easily applied to transport liquid type fluid without time and space constraint, they should be designed and maintained carefully to be functional safely during design lifetime. In this paper, various theories estimating pipeline thermal expansion are investigated and the effects of pipe components to expansion are studied.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.173-179
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• 2010

In a HLW repository, the buffer is exposed to an elevated temperature due to a radioactive decay and geochemical conditions for a long time and such a hydrothermal condition may cause a significant loss of its barrier function. This study carried out hydrothermal tests with a domestic smectite clay to investigate the changes in the expandibility, layer charge, and cation exchange capacity of the smectite. When the temperature and potassium concentration in solution was increased for the hydrothermal treatments, the expandibility decreased, the layer charge negatively increased, and the CEC also decreased.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.70-77
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• 2005

An axisymmetric supersonic ejector equipped with a converging-diverging diffuser was built and pressure at various locations along the ejector-diffuser system was recorded with emphasis on the supersonic starting of the secondary flow. In order to find the effects of the opening size of the secondary flow, a number of openings were used with a constant primary pressure. Supersonic starting was possible only for d/D, the ratio of the opening diameter and the diffuser throat diameter, less than 0.306. for larger values of d/D, the ejection begins at subsonic secondary flow condition. With the closure of the opening, the primary flow brings the normal shock downstream of the converging-diverging diffuser And the starting of the ejector continues even after the closure was removed.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.20-28
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• 2018

In general, the choking phenomenon occurs due to the flow acceleration of a turbine under high pressure-ratio. During choking, the total pressure ratio increases without any variation in the mass flow rate. It is difficult to predict choking characteristics by using conventional meanline analysis, which utilizes mass flow inlet boundary condition. In this study, an algorithm for predicting the choking point is developed to solve this problem. In addition, a performance estimation algorithm is presented to estimate the performance after choking, based on the flow behavior of flow expansion at the choked nozzle or rotor. The analysis results are compared with 3D CFD analysis and experimental data to validate this method.

• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.559-567
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• 2018

In the case of fire, surface treatment agents used in external insulation finishing methods are substances that are vulnerable to fire due to thin finishes and the combustion of polymers. In this study, it was expected that the performance of surface preparation mortars could be improved by using expandable graphite with excellent thermal performance. Experimental results showed that the mechanical properties of surface preparation mortar were improved by using the fly ash and silica fume. Surface treatment materials using expanded graphite have a characteristic of expanding when a fire occurs. It has been shown that heat-swellable surface treatment materials can reduce the penetration of heat sources into the surface of synthetic insulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.104-111
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• 2019

A separate type rotary engine consisting of a compressor and an expander is under development. The engine motoring, compressor pressure, and fuel combustion have been tested with the initial prototype for operability checks of the mechanism. This paper describes an engine cycle analysis method designed specifically for this new-concept engine. The unique operational mechanism of the engine and the thermodynamic properties of each step of air intake, compression, filling of combustion chamber, combustion, expansion and exhaust were analyzed. The cycle efficiencies of this engine according to various engine design parameters as well as the cooling effect of compressed air between the compressor and expander can be easily calculated with this method; further, some case studies are presented in this paper.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.50-56
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• 2016

In this work, the open-drive oil free air compressor is modified to activate an organic Rankine cycle system as an expanding machine. The shape of the modified scroll expander case is a rectangular parallelepiped and the size of the case is $0.0394m^3$. The scroll expander is operated in an ORC using R245fa as working fluid with various working conditions for the performance test. The test data points are used to calculate the parameters of the scroll expander semi-empirical simulation model. The simulation results are compared with the experimental results to validate the simulation model.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.75-83
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• 2018

This paper described a results of dynamic stability by using wheel tracking test and unconfined compression test, in order to evaluate behavior characteristics on the developed pocketable expansion material for emergency restoration of ground cavity. The wheel tracking test result showed that the settlement increment ratio of the recovered ground by the expansion material was decreased compared to the sandy ground in high load condition. That is, it was confirmed that the expansion material was able to restrain the settlement due to the material stiffness, and the same results were obtained for the dynamic stability evaluation results. From the results of unconfined compression test, the pocketable expansion material was found to be able to fully support load on the restored cavity.

• Composites Research
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• v.27 no.2
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• pp.52-58
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• 2014

Short fiber reinforced composites manufactured by injection molding have diverse fiber orientations variable with measuring positions even in the same specimen, which is caused by the flow induced fiber orientation. Fiber orientations considerably affect the mechanical and thermal properties of final composite products. In this study, fiber orientation of injection molded carbon fiber reinforced PA6/PPO composite was measured at several points of the specimen by optical microscopy analysis and the corresponding izod impact strength, coefficients of thermal expansion (CTE) were also measured to investigate the influence of local fiber orientation on the mechanical and thermal properties. Izod impact strength where fiber was perpendicular to the direction of crack propagation was higher than where fiber was parallel to the direction, which could be explained be the impact resistance reinforcing mechanism by fiber orientation. CTE was also lower where fiber was parallel to the measurement direction of CTE than where fiber was perpendicular to the direction, which could be also explained by the dimensional stability mechanism by fiber orientation.

• Applied Chemistry for Engineering
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• v.28 no.4
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• pp.437-441
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• 2017

This study was carried out to investigate the volumetric expansion ratio and hardness of expanded graphite after coating with various resins which were used as an additive of fireproof sealant. The coating thickness of the resin, which represents the coating rate, was dependent of the drying speed of the resin and the viscosity of the resin. Therefore the coating thickness was shown as follows: polyvinyl acetate > acrylic resin > urethane resin > water soluble latex. Furthermore, the volumetric expansion ratio was as follows: urethane resin > water soluble latex > acrylic resin > polyinyl acetate and the hardness was as follows: polyvinyl acetate resin > acrylic resin > water soluble latex > urethane resin. This showed that the volume of expansion was reduced by expansion, which was not covered by coating, but significantly increased by increasing hardness and allowed it to be used as a refractory addition. According to the response surface methodology, the optimized addition amount and stirring speed of acrylic resin were 37.6 wt% and 441.4 rpm, respectively.