• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2534-2539
• /
• 2007

Launch vehicles are exposed to aerodynamic heating conditions while flying at high Mach numbers in the atmosphere. In this study aerodynamic heating test for fairing nose-cone was done using ATSF(Aerodynamic Thermal Simulation Facility) and Engineering Model for fairing. ATSF is a facility that can simulate given temperature profile using about 4,000 halogen heaters on fairing model. Aerodynamic heating profile is got from result of thermal analysis using MINIVER, Thermal Desktop and SINDA/FLUINT. After aerodynamic heat test, it is found that initial temperature of fairing inner surface and thickness of BMS has important effects on temperature of fairing inner surface. Also it is confirmed that maximum temperature of fairing nose-cone inner surface during flight is lower than allowable temperature limit. Later, thermal correlation between thermal analysis and experimental results will be done using aerodynamic heating test result

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.3371-3376
• /
• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the thermal conductivity of the ground. To evaluate this heat transfer property, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to water over various test lengths. By measuring the water temperatures entering and exiting the loop, water flow rate, and heat load, effective thermal conductivity values of the ground were determined. The effect of increasing thermal conductivity of grouting materials from 0.82 to 1.05 W/m$^{\circ}C$ resulted in overall increases in effective ground thermal conductivity by 25.8% to 69.5%.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.1349-1352
• /
• 2005

This paper is to investigate a defect for thermal barrier coating layers by acoustic emission method in 4-point bending test. The two-layer thermal barrier coating is composed of $150\mu{m}\;CoNiCrAlY\;bond\;coating\;by\;vacuum\;plasma\;spray(VPS)\;process\;and\;250\mu{m}\;ZrO_2-8wt%Y_2O_3$ ceramic coating layer by air plasma spray(APS) process on Inconel-718. The specimen prepared by cyclic thermal test(500, 1000, 2000cycle) at $1050^{\circ}C$ The AE monitoring system is composed of PICO type sensor, a wide band pre-amplifier(40dB), PC and AE DSP(16/32 PAC) board. The AE event, amplitude, Cumulative energy and count of coating specimens is evaluated according to cyclic thermal test.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회
• /
• pp.325-335
• /
• 2010

A new geothermal energy source obtained from a tunnel structure has been studied in this paper. The geothermal energy is extracted through a textile-type ground heat exchanger named "Energy Textile" that is installed between a shotcrete layer and a guided drainage geotexitle. A test bed was constructed in an abandoned railway tunnel to verify the geothermal heat exchanger system performed by the energy textile. To evaluate the applicability of the energy textile, we measured the thermal conductivity of shotcrete and lining samples which were prepared in accordance with a common mixture design. An overall performance of the energy textile installed in the test bed was evaluated by carrying out a series of in-situ thermal response test. In addition, a 3-D finite volume analysis (FLUENT) was adopted to simulate the operation of the ground heat exchanger being encased in the energy textile with the consideration of the effect of the shotcrete and lining thermal conductivity.

• 한국항공우주학회지
• /
• 제49권5호
• /
• pp.407-415
• /
• 2021

인공위성의 부품은 발사 전 지상에서의 우주 궤도환경 하에서의 성능검증이 필수적이다. 본 논문은 열진공시험을 위한 위성 부품 및 소형 열진공챔버 간의 전도, 복사, 열손실 및 내부 발열의 열환경을 고려한 모델식을 설계하였다. 최근 한국항공우주연구원에서 수행된 열진공시험 20건의 시험데이터를 이용한 시스템 식별을 수행하였다. 시험품 기능시험의 발열이 일정하지 않는 경우를 제외하고 시스템 식별의 정확성을 확인함으로써 개발된 모델식이 유효함을 검증하였다.

• 대한의용생체공학회:의공학회지
• /
• 제17권3호
• /
• pp.327-336
• /
• 1996

This study was performed to investigate the effec% of immersion in water and thermal cycling on the mechanical peoperties of light cured restorative composite resins. Five commerically available light-cured composite resins(Photo Clearfil A : CA, Lite-Fil A . LF, Clearril Photo Posterior CP, Prisms AP.H.. PA, 2100 : ZH) were unto The specimens of 12 m in diameter and 0.7 m in thickness were made, and an immersion in $37^{\circ}C$ water for 7 days and a thermal cycling of 1000 cycles at 15 second dwell time each in $5^{\circ}C$ and $55^{\circ}C$ baths were performed. Biaxial flexure test was conducted using the ball-on-three-ball method at the crosshead speed of 0.5mm/min. In order to investigate the deterioration of composite resins during the thermal cycling test, Weibull analysis for the biaxial flexure strengths was done. Fracture surfaces and the surfaces before and after the thermal cycling test were examined by SEM. The highest Weibull modulus value of 10.09 after thermal cycling tests which means the lowest strength variation, was observed in the CP group, and the lowest value of 4.47 was obsered in the LF Group. Biaxial flexure strengths and Knoop hardness numbers significantly decreased due to the thermal cycling ($\textit{p}$< 0.01), however, they recovered when specimens were drie4 The highest biaxial flexure strength of 125.65MPa was observed in the ZH group after the thermal cycling test, and the lowest value of 64.86MPa was observed in the CA group. Biaxial flexure strengths of ZH and CP groups were higher than those of PA, CF, and CA groups after thermal cycling test($\textit{p}$< 0.05). Knoop hardness numbers of CP group after the thermal cycling test was the highest(95.47 $\pm$ 7.35kg/$mm^2$) among the samples, while that of CA group was the lowest(30.73 $\pm$ 2.58kg/$mm^2$). Knoop hardness numbers showed the significant differences between the CP group and others after the thermal cycling test(($\textit{p}$< 0.05). Fracture surfaces showed that the composite resin failure developed along the matrix resin and the filler/resin interface region, and the cracks propagated in the conical shape from the maximum tensile stress zone.

• 한국전기전자재료학회논문지
• /
• 제29권3호
• /
• pp.152-158
• /
• 2016

The bonding characteristics of MLCCs (multi layer ceramic capacitor, C1608) lead-free solder (SAC305) joints were evaluated through thermal shock test ($-40^{\circ}C{\sim}125^{\circ}C$, total 1,800 cycle). After the test, IMCs( intermetallic compounds) growth and cracks were verified, also shear strengths were measured for degradation of solder joints. In addition, The thermal stress distributions at solder joints were analyzed to compare the solder joints changes before and after according to thermal shock test by FEA (finite elements analysis). We considered the effects of IMCs growth at solder joints. As results, the bonding characteristics degradation was occurred according to initial crack, crack propagations and thermal stress concentration at solder-IMCs interface, when the IMCs grown to solder inside.

• 설비공학논문집
• /
• 제19권7호
• /
• pp.512-520
• /
• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the effective thermal conductivity of the ground and the effective thermal resistance of the borehole. To evaluate these heat transfer properties, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to circulating water. The line-source method is applied to the temperature rise in an in-situ test and extended to also give an estimate of borehole effective thermal resistance. The effect of increasing thermal conductivity of the grouting materials from 0.818 to $1.104W/m^{\circ}C$ resulted in overall increases in effective thermal conductivity by 15.8 to 56.3% and reductions in effective thermal resistance by 13.0 to 31.1%.

• 한국항공우주학회지
• /
• 제34권12호
• /
• pp.90-95
• /
• 2006

위성 열평형 시험에 사용하는 열진공 챔버의 벽은 흑체 거동을 하는 우주공간과는 달리 위성의 복사 에너지를 완벽하게 흡수하지 못하고 일부를 반사한다. 챔버의 크기가 작을수록 이러한 챔버 벽 효과는 커지는 것으로 알려져 있다. 이것은 시험비용을 줄이기 위해 대형 챔버를 사용하기 힘든 소형위성의 개발에 걸림돌이 된다. 본 연구에서는 챔버 벽 효과를 예측하고 이를 보정하기 위한 정량적인 분석을 진행하였다. 그 결과로 챔버 벽 효과에 의한 온도 오차를 계산하여 시험 데이터를 보정할 수 있게 하였다. 또, 최적 면적비를 정의하여 소형위성의 열평형 시험용 열진공 챔버의 크기를 정하는데 기준을 마련하였다. 덧붙여 챔버 벽을 투명한 재질로 코팅하여 챔버 벽 효과를 줄일 수 있는 방안에 대해 이론적인 분석을 수행하였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2005년도 춘계학술대회
• /
• pp.427-432
• /
• 2005

This study treats the advantage of in situ line source method measuring the heat transfer capacity of a borehole, using mobile equipment, to determine the thermal properties of the entire borehole system such as thermal conductivity, diffusiveity. volumetric heat capacity, and borehole thermal resistance. The results from the response test include not only the thermal properties of the ground and the borehole, but also conditions that are difficult to estimate, e,g. natural convection in the boreholes, asymmetry in the construction, etc. In this study, 1) theoretical in situ methods for assessing working fluid temperature variation in V-type PE tube have been introduced, and 2) TRTE(Thermal Response Test Equipment) has been built based on these kinds of theoretical in situ methods. Basically TRTE consists of a pump, a heater and temperature sensors for measuring the inlet and outlet temperatures of the borehole. In order to make equipment easily transportable it is set up on a small trailer. Since the response test takes above two days to execute, the test was fully automatic in recording measured data using Labview DAS(Data acquisition system) program. The test was demonstrated in the course of intensive research in this field through the one site at Ulsan city in Korea. From this kind of thermal properties test of borehole systems in situ, the design of the borehole system can be optimized regarding the total geological, hydro-geological and technical conditions at the location.