• 한국추진공학회지
• /
• 제14권5호
• /
• pp.45-50
• /
• 2010

연료링의 위치 및 열차폐 코팅의 종류에 따른 연소기의 재생냉각 특성을 검토하였다. 연료링을 노즐의 중간 부분에 위치시키고 냉각채널을 분기시켜서 설계하는 방법이 열적으로 타당함을 확인하였다. 또한 복합재를 이용한 노즐확장부가 적용 가능한 기술적 상황이라면, 팽창비가 높고 열유속이 낮은 노즐 후류 부분은 이를 이용하는 것이 매우 적절하다고 판단된다. 적용 가능한 열차폐 코팅 중에서 30톤급 연소기 및 가스발생기 개발과정에서 사용했던 $Y_2O_3$ stabilized $ZrO_2$과 내산화성이 우수한 Ni/Cr을 고려하였다. 내산화성이 우수한 Ni/Cr에 비해 세라믹 코팅($Y_2O_3$ stabilized $ZrO_2$)이 열차폐 효과가 우수한 것으로 파악되었다.

• 한국자기학회지
• /
• 제8권5호
• /
• pp.317-332
• /
• 1998

소자화 랭동법은 전자 또는 핵의 자기 모벤트를 등온적으로 자화시킨 다음 단열상태에서 자화를 없앰으로써 온도를 내리는 방법이다. 전자의 소자화 냉동기는 교석 랭동기의 출현으로 거의 사용되지 않고 있으나 핵의 소자화 냉동기는 ${\mu}K$ 이하의 극저온을 얻을 수 있는 유일한 방법으로 극저온에서의 $^{3}He$액체 또는 $^{3}He$ 고체의 상전이, 극저온 초전도 현상, 핵의 자발질서 현상, 스핀 유리 상전이등의 연구에 많이 사용되고 있다. 핵의 소자화 냉동기는 대개 물체(시료) 전체의 온도를 내리는데 사용하나 빠른 소자화를 통해 핵만의 온도를 내리는데도 사용된다. 핵만의 온도를 내리는 냉동방법은 핵 자기 현상의 연구에 많이 이용되고 있다. 이러한 극저온을 얻기 위한 냉동법은 최첨단 기술이나 현재 국내에서는 극저온을 중점적로 연구하는 곳이 없는 실정이다. 본 논문에서는 소자화 냉동에 관한 현재의 취세를 소개하고 앞으로의 연구방향을 제시하고자 한다.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2002년도 학술대회 논문집
• /
• pp.63-66
• /
• 2002

A free piston and free displacer (FPFD) Stilting cryocooler for the cooling infrared and cryo-sensor is currently under development at Korea Institute of Machinery & Materials. In this study, the dynamic characteristics of the displacer in the expansion space of the Stirling cooler was investigated by experiment. The experimental results show that the Stirling cryocooler has maximum cooling capacity at the certain relation between operating frequency and natural frequency of the displacer and the operating frequency of the Stirling crycooler should be determined by natural frequency of the linear compressor and displacer.

• 설비공학논문집
• /
• 제24권10호
• /
• pp.733-738
• /
• 2012

It is important issue to reduce the electric energy to save the operating cost of HVAC system. Even if electrical energy is the clean energy, it is difficult and takes high cost for storage of electricity. These cause the high peak load of electric energy for HVAC in summer season. In korea, government impose the electric charge with several grade for the purpose of cut-off the peak load of electricity. Government has a policy to support to design and install the heat/ice storage system using midnight electricity. In this study, analysis of cooling load and operating characteristics for ice storage system are performed. And, also economical efficiency is compared between ordinary charge system of electricity and midnight rate charge of electricity. The systematic and economical supports are needed for expansion of usage of energy saving equipments.

• 한국초전도ㆍ저온공학회논문지
• /
• 제13권3호
• /
• pp.36-41
• /
• 2011

This paper describes experimental investigation on neon refrigeration system using commercial helium compressor. In this paper, neon refrigeration cycle is calculated with assumption of ideal heat exchanger. From analysis, 32.6 K of the lowest temperature and 0.945 of quality after expansion are predicted. Cryogenic heat exchangers for pre cooler and main heat exchanger are designed and fabricated with configuration of tube-in-tube heat exchanger. In experiments, cooling performance test are performed as variation of charging pressure and orifice hole diameter. From experimental results, the lowest temperature of 44.0 K was measured with 500 ${\mu}m$ orifice and 1500 kPa of charging pressure.

• 대한기계학회논문집B
• /
• 제31권1호
• /
• pp.40-50
• /
• 2007

The present contribution describes the application of elliptic-blending second moment closure to predict the gas cooling process of turbulent super-critical carbon dioxide flow in a square cross-sectioned duct. The gas cooling process under super-critical state experiences a drastic change in thermodynamic and transport properties. Redistributive terms in the Reynolds stress and turbulent heat flux equations are modeled by an elliptic-blending second moment closure in order to represent strongly non-homogeneous effects produced by the presence of walls. The main feature of Durbin's elliptic relaxation second moment closure that accounts for the nonlocal character of pressure-velocity gradient correlation and the near-wall inhomogeneity guaranteed by the elliptic blending second moment closure.

• 한국초전도ㆍ저온공학회논문지
• /
• 제4권1호
• /
• pp.140-144
• /
• 2002

A free piston and free displacer (FPFD) Stirling cryocooler has been widely used for the cooling infrared and cryo-sensor. The thermodynamic performance of the free piston and free displacer type (FPFD) Stirling cryocooler is highly dependent on the operating frequency of the linear compressor and the natural frequency of the displacer. In this study, to find optimal relation between operating and natural frequency of the displacer the dynamic characteristics of the displacer in the expansion space of the Stirling cooler was investigated by experiment. The experimental results show that the Stifling cryocooler has maximum cooling capacity at the operating frequency of about 0.8 times of the natural frequency of displacer. Therefore the operating frequency of the Stirring cryocooler should be determined by natural frequency of the linear compressor and displacer.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.108-112
• /
• 2000

This paper presents a mathematical model and simulation of the micro-actuator based on thermally induced liquid-vapor phase-change in a partially-filled closed cavity. The volume expansion by liquid-vapor Phase change can generate considerable forces and displacement $({\sim}50{\mu}m)$ required for commercial use. For optimum operation involving many cycles within the closed chamber, active(thermoelectric) heating and cooling is used. The optimization of the system is conducted according to the parameters such as input power and response time. The optimized performance of micro-actuator is reasonable compared to other actuators.

• 한국분말재료학회지
• /
• 제1권1호
• /
• pp.52-59
• /
• 1994

Since the coefficient of thermal expansion (CTE) of matrix phase is larger about 4 times than that of W particle in tungsten heavy alloy, the thermal stresses due to the CTE difference between the two phases are induced in the alloy during heating and cooling processes. In the present study, a series of W heavy alloy containing various W particle volumes of 0 to 90% is made to investigate the residual stress taking place during cooling process. The CTE and residual stress of the series of alloy are measured by dilatometer and X-ray diffractometer. The residual stress of W particle is in compressive stress irrespective of W particle vol% and tends to increase with decreasing W particle vol% while that of the matrix phase is in tensile stress. The measured residual stress of W particle is about a third of calculated thermal stress. The influence of W particle vol% on the residual stress of W heavy alloy is discussed in terms of the deformation behaviors of W particle and matrix phase.

• 한국연초학회지
• /
• 제7권2호
• /
• pp.189-197
• /
• 1985

The purpose of this study is to improve the method and the apparatus for recovering freon-11 used in a process for increasing the filling capacity of tobacco. The first, the theoretical recovery rate of freon-11 was calculated from vapour pressure and thermodynamic properties of freon-11. The second, the usability of theoretical data was evaluated by the comparison between the theoretical data and the experimental data from the pilot plant. The result obtained under the present experiment condition was quite similar to the rate at 15kg/cm2 and 5$^{\circ}C$, but the theoretical data evaluated were 0.1 to 0.3% lower than the experimental data at 20 to 25kg/cm2 and 5$^{\circ}C$. The recovery rate of the cooling and the compression system was about 95% with freon-11 used in this system and that with freon-11 concentrate of waste gas was about 3 to 3.6% at 20 to 25kg/cm2 and 5$^{\circ}C$.