• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.4
• /
• pp.331-335
• /
• 2018

The purpose of this study is to investigate the feasibility of CFBC artificial fine aggregate as a substitute for natural aggregate used in dry mortar. The basic performance of the flow, compressive strength and dry shrinkage of the dry mortar was evaluated. Four types of test dry mortar specimens using natural aggregate without expansion admixture, a specimen with modified CaO expansion admixture and natural aggregate, a specimen with modified CaO expansion admixture and CFBC artificial fine aggregate, and a specimen using CFBC artificial fine aggregate without modified CaO expansion admixture were evaluated respectively. As a result of evaluation of drying shrinkage performance at 20th day of age, the dry shrinkage performance of the specimen using modified CaO expansion admixture was found to be the highest at $250{\times}10^{-6}$. On the other hand, the specimen containing the modified CaO expansion admixture with CFBC artificial aggregate exhibited a shrinkage of $410{\times}10^{-6}$, and the drying shrinkage of specimen using natural fine aggregate without expansion admixture was $450{\times}10^{-6}$. When the modified CaO expansion material was used, and exhibited performance equal to or higher than that of the shrinkage-drying property.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.1
• /
• pp.40-45
• /
• 2011

The purpose of research is to understand the characteristics of refrigeration system having a liquid-vapor phase separator after expansion device and precooling heat exchanger. After expansion process of typical refrigerant of freezer, R134a, the cold vapor of the expanded refrigerant mixture is separated in the liquid-vapor separator and introduced in the precooling heat exchanger to enable the liquid refrigerant to be subcooled. The analysis results showed that the increasing rate of refrigeration capacity and COP can be 8.6% and 1.4%, each. The cause of these performance improvements is due to the difference of the slope of saturated vapor and saturated liquid lines in Mollier diagram of refrigerant.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.2
• /
• pp.20-28
• /
• 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
• /
• v.18 no.6
• /
• pp.559-567
• /
• 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 Institute of Gas
• /
• v.20 no.5
• /
• pp.50-56
• /
• 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 Korean Tunnelling and Underground Space Association
• /
• v.22 no.1
• /
• pp.47-58
• /
• 2020

The interest in the use of shield TBM (Tunnel Boring Machine) on the tunnel excavation has been increased rapidly in Korea. The shield TBM tunnel is generally designed as non-drainage tunnel. Consequently, if water leakage through the segment joints happens, big problems on the usage and stability of tunnel can be occurred. In this study, the variation of waterproof capacity of hydrophilic rubber waterstop by the construction error and excessive displacement of segment was studied. In particular, the waterproof capacity of each of single and double layer arrangements of hydrophilic rubber waterstop was examined to verify the efficiency of the double layer arrangement. The test results show that the single layer and double layer hydrophilic rubber waterstop showed the same waterproof performance. hydrophilic rubber waterstop has favorable on the offset, however unfavorable on the gap.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.3
• /
• pp.125-132
• /
• 2014

Steel fiber is a effective composite for crack resistance and improve structural performance under tensile loading. This study presents an evaluation of crack resistance and structural performance in cement mortar with steel fiber and expansion agent through internal chemical prestressing. For this work, cement mortar samples with 10% replacement of cement binder with CSA (Calcium-Sulfo-Aluminate) expansion agent and 1% volume ratio of steel fiber are prepared. Including basic mechanical properties, initial cracking load and fracture energy are evaluated in cement mortar beam with notch. Initial cracking load and fracture energy in cement mortar with CSA and steel fiber increase by 1.75 and 1.41~1.53 times compared with those in cement mortar with steel fiber. With optimum mix design for steel fiber and CSA expansive agent, the composite with chemical prestressing can be applied to various members and effectively improve crack resistance to external loading.

• Journal of the Society of Disaster Information
• /
• v.14 no.1
• /
• pp.79-88
• /
• 2018

In this study, the changes of the expansion and strength according to the temperature of the emergency repairing expansion material were examined by cup foaming test and uniaxial compressive strength test, and the accelerated compression creep test was carried out to confirm the long term stability. Ramp & Hold test and accelerated compressive creep test were performed to evaluate the creep performance. The short - term creep test was used to determine the initial creep strain of the expanding material. The isothermal method using time - To evaluate the long - term compressive creep performance.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.4
• /
• pp.568-576
• /
• 1986

본 연구에서는 포하수 혹은 팽창기를 열매체로한 스크루우팽창기의 회전자회 전각에 의한 회전자간체적변화, 흡입구의 면적변화, 팽창기내에서의 누설통로에서의 임계등의 기하학적 특성과 흡입구와 누설통로에서의 임계유속을 고헌한 해석프로그램 을 개발하여 회전자회전수 흡입열매체의 건도, 흡입.토출압력비 그리고 팽창기내부에 서의 누설등의 효과에 대한 해석을 행하여 스크루우 팽창기의 동력발생기로서의 실용 성을 검토하였다.

• Journal of Energy Engineering
• /
• v.23 no.4
• /
• pp.230-235
• /
• 2014

In this study, performances of the vane expander protype for micro organic Rankine cycle with refrigerant R134a as a working fluid have been analyzed. While operating organic Rankine cycle for analysing expander efficiencies such as overall efficiencies, volumetric efficiencies and mechanical efficiencies under $110^{\circ}C$ of expander inlet temperature, the power of the expander, inlet temperature of expander, inlet pressure of expander and the flow rate of the working fluid(refrigerant R134a) have been measured while varying the rotational speed of the expander. It was found that the more the expander revolution speed is high, the more the expander power, overall efficiencies and volumetric efficiencies are higher. In case of 500 rpm of rotational speed, overall efficiencies are 6~7% and in case of 1000 rpm, overall efficiencies are 11~12%. We have found that low volumetric efficiencies result in poor overall efficiencies.