• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.116-116
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• 2012

위성의 발사, 천이궤도, 운영궤도 등에서 위성체에 주어지는 극한 온도와 진공상태에서 위성체와 열제어시스템이 요구 조건을 만족시키는가를 확인하기 위하여 열진공시험을 수행한다. 우주에서 일어나는 환경변화는 극도로 심해서 지상에서 이와 유사한 열적 환경을 모사하는 방법은 쉽지가 않고, 일반적으로 위성체에 대한 열진공/평형 시험을 위해서는 열유속 흡수법과 열유속 투사법의 두 가지 방법을 사용한다. 한국항공우주연구원에서는 종래 접촉식 히터를 위성체에 직접 부착하는 방법에서 탈피하여 새로이 IR Lamp를 이용한 열유속 흡수법을 이용하여 위성체에 계산된 열유속을 인가하는 방법으로 위성체 열진공/평형시험을 수행하였으며, IR Lamp는 요구되는 100W~400W 사이의 열량을 오차 범위 5% 이내로 인가하여 균일한 온도 분포를 유지하고 성공적인 시험을 수행하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1799-1807
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• 1994

Natural convection from a slightly inclined circular cylinders immersed in quiescent cold pure water was studied experimentally. The experiment was carried out for circular cylinders with uniform heat flux ranging from $100W/m^{2} to 800 W/m^{2}$ and inclined angle ranging from horizontal $({\phi}=0^{\circ}) to 15^{\circ}$. The flow fields around cylinder were visualized and heat transfer characteristics investigated by measuring the surface temperatures for each case. As the results, it is shown that flow patterns are changed consecutively through the sequence of steady state downflow, unsteady state flow and steady state upflow with increasing heat flux. At the same inclined angle, as heat flux increases, the average Nusselt number decreases and then increases. At the same heat flux, as inclined angle increases, the average Nusselt number decreases.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.166-166
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• 1999

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.116-116
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• 2002

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.290-295
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• 2000

An experimental study was carried out in a cavity with upper channel and square heat surface by visualization equipment with Mach-Zehnder interferometer and laser apparatus. The visualization system consists of 2-dimensional sheet light by Argon-Ion Laser with cylindrical lens and flow picture recording system. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system(CACTUS'2000). Obtained result showed various flow patterns. Severe unsteady flow fluctuation within the cavity are remarkable and sheared mixing layer phenomena are also found at the region where inlet flow is collided with the counter-clockwise rotating main primary vortex. Photographs of Mach-Zehnder are also compared in terms of constant heat flux.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.12
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• pp.953-963
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• 2015

There is an increasing need to understand the thermal-hydraulic phenomena, including the critical heat flux (CHF), in narrow rectangular channels and consider these in system design. The CHF mechanism under a saturated flow boiling condition involves the depletion of the liquid film of an annular flow. To predict this type of CHF, the previous representative liquid film dryout models (LFD models) were studied, and their shortcomings were reviewed, including the assumption that void fraction or quality is constant at the boundary condition for the onset of annular flow (OAF). A new LFD model was proposed based on the recent constitutive correlations for the droplet deposition rate and entrainment rate. In addition, this LFD model was applied to predict the CHF in vertical narrow rectangular channels that were uniformly heated. The predicted CHF showed good agreement with 284 pieces of experimental data, with a mean absolute error of 18. 1 % and root mean square error of 22.9 %.

• Nuclear Engineering and Technology
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• v.20 no.2
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• pp.112-119
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• 1988

The purpose of this work is to obtain the experimental data for the forced How dryout heat flux in a heat generating stratified debris bed which simulates the degraded nuclear reactor core after severe accident. The present observations were mainly focused on the effect of coolant mass flux on the dryout heat flux in the stratified debris bed which consists of several layers with selected particle sizes under constant bed depth and temperature of inlet coolant flow conditions. The following results were obtained from this experimental work: (1) The dryout heat flux in the stratified debris bed increases with increase of upward forcing mass flux of coolant. The similar trend of increase rate of dryout heat flux in the stratified bed was observed in the uniform particle size bed. (2) For the comparison of theoretical values and experimental data, the use of surface area mean diameter as a particle diameter was suitable for the calculation of dryout heat flux.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.195-200
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• 2001

An experimental study on critical heat flux (CHF) has been performed for water flow in a uniformly heated vertical 3 by 3 rod bundle under low flow and a wide range of pressure conditions. The objective of this study is to investigate the parametric trends of CHF with 3 by 3 rod bundle test section where three unheated rods exist. The general trends of the CHF are coincident with previous understandings. At low flow and system pressure above 3 MPa, some critical qualities are larger than 1.0 due to counter-current flow in test sections. Since there is a supply of water to the heated section from unheated section, the maximum CHFs at system pressure between 2 and 4 MPa are not shown.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.330-336
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• 2001

Water heat transfer experiments were carried out in a uniformly heated annulus with a wide range of pressure conditions. The local heat transfer coefficients for saturated water flow boiling have been measured just before the occurrence of the critical heat flux (CHF) along the length of the heated section. The trends of the measured heat transfer coefficients were quite different from the conventional understanding for the heat transfer of saturated flow boiling. This discrepancy was explained from the nucleate boiling in the liquid film of annular flow under high heat flux conditions.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.165-165
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• 1999