• Journal of Korea Foundry Society
• /
• v.21 no.3
• /
• pp.192-197
• /
• 2001

본 연구에서는 여러 다른 냉각속도로 냉각되는 강의 조직과 경도를 예측하는 수치 해석을 수행하였다. 해석 프로그램은 확산과 비확산 변태에 대한 변태 이행 방정식과 유한차분법을 이용하여 제품에 대해서 온도분포 및 조직변태에 대한 예측을 수행하고 또한 경도를 예측하도록 하였다. 해석 결과와의 비교를 위해 여러 다른 냉각속도로 냉각되는 AISI 410시편들에 대한 일련의 시험을 행하여 각각의 조직과 경도를 구하였으며 특히 온도해석에 사용하는 열전달계수는 실험을 통하여 구한 값을 사용하였다. 실험에 의해 구해진 결과는 해석 프로그램을 이용한 값과 잘 일치 하였다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.10a
• /
• pp.732-737
• /
• 1997

본 연구에서는 IFC6.0코드 검증과 개선점 파악을 목적으로 유럽공동체 연구소 JRC-Ispra에서 수행한 Faro L-14실험을 모의하였으며 이는 ISP-39 참여하에 수행하였다. ISP-39는 용융물과 냉각재 반응 시 용융물 냉각 현상에 있어 관련 해석 코드를 검증하고 각 코드의 한계점을 파악하는데 그 목적을 두고 있다. 계산 결과 용기 내 압력상승 및 냉각재 상승에 관한 경향은 잘 모의하고 있다. 한편 절대값에 있어 실험치에 미치지 못하는 것은 냉각재와의 혼합 시 용융물의 분쇄가 실제보다 덜 예측되고 이에 따른 열전달량의 예측 미달로 인한 것으로 보이며 결국 Lagrangian코드개발의 필요성이 확인되었다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.12
• /
• pp.1647-1653
• /
• 2011

The cycle time in injection moulding greatly depends on the cooling time of the plastic part that is controlled by cooling channels. Cooling channels are required to facilitate the heat transfer rate from the die to the coolant without reducing the strength of the die. Employing layered manufacturing techniques (LMT), a die embedding conformal cooling channels can be fabricated directly while conventional cooling channels are usually made of straight drilled hole. Meanwhile, H13 tool steel is widely used as the die material because of its high thermal resistance and dimensional stability. However, H13 with a low thermal conductivity is not efficient for certain part geometries. In this context, the use of functionally graded materials (FGMs) between H13 and copper may circumvent a tradeoff between the strength and the heat transfer rate. This paper presents a method for modeling of conformal cooling channels made of FGMs.

• Journal of ILASS-Korea
• /
• v.13 no.3
• /
• pp.143-148
• /
• 2008

In the present study, the correlation between the Nusselt number and Reynolds number was developed for forced convection and nucleate boiling region in spray cooling. Also the effect of droplet subcooling on spray cooling heat transfer was investigated. Full cone spray nozzles were employed for spray cooling experiment, and water and FC-77 were used for developing the correlation. From the experimental results, the correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for water and FC-77.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05a
• /
• pp.422-429
• /
• 1997

피동형 격납용기 냉각계통 해석을 위하여 격납용기 압력, 온도 과도현상 분석 코드인 CONTEMPT4/MOD5 전산코드에 피동형 격납용기 열전달 모델을 추가하였다. 외부공기의 순환에 의한 철제 격납용기와 차폐건물 사이의 환형 공간의 냉각모델은 자연대류 및 혼합 대류의 기존 실험적 상관식을 사용하였고 상부에서 분사된 물의 증발에 의한 열전달 현상은 analogy 개념을 적용한 질량전달 모델을 도입하였다. 개선된 전산코드로 1000Mwe급 원전의 피동형 격납용기에 대하여 각 실험적 상관식의 차이, 물막의 형성비율, 습식냉각 지연시간 등의 민감도 분석을 수행하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.1
• /
• pp.33-39
• /
• 2010

The film boiling heat transfer was experimentally investigated for the water sprays impacting on an inclined hot surface. Full cone spray nozzles were employed for the spray cooling experiment, and experiments were made for different inclination angles of $\theta=0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$. The experimental results show that, in the downstream region of the inclined hot surface, increasing the inclination angle increases the local heat flux slowly because of increasing the number of rebound droplets. However, the inclination angle of heat transfer surface had no remarkable effect on the local heat flux of spray cooling under the present test conditions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.05a
• /
• pp.9-12
• /
• 2003

A cooling performance analysis has been made in the 8-channel calorimeter based on sub-scale KSR-III engine. Three-dimensional heat transfer analysis in cooling channels has been performed using the heat flux distribution through the chamber wall predicted from axi-symmetric compressible flow inside the combustion chamber. The heat flux distribution was verified against the published literature. Presented for the development and operation of the calorimeter are the coolant pressure drop, coolant temperature rise and the maximum chamber wall temperature.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.6
• /
• pp.880-887
• /
• 1998

In order to study heat transfer characteristics of spray cooling for the purpose of uniform and soft cooling of high temperature surface a series of experiments for a hot horizontal copper flat plate was performed by downflow spray water using flat spray nozzle. Cooling curves were mea-sured under the various experimental conditions of flow rates and temperatures of cooling water Surface temperature surface heat fluxes and heat transfer coefficients of horizontal upward-facing flat surface were calculated with cooling curves measured at each radial positions near the cooling surface by TDMA method. Generally heat transfer characteristics for spray cooling is simi-lar to boiling phenomenon of pool boiling. The minimum heat flux(MHF) appear at the surface temperature of about ${\Delta}Tsat=250^{\circ}C$ and the critical heat flux(CHF) appear at about ${\Delta}Tsat=250^{\circ}C$.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.5
• /
• pp.25-32
• /
• 2000

In this paper, experiments investigating the high-temperature region heat transfer coefficients for the spray cooling of hot flat plates were performed by down spray water using flat spray nozzles. The heat transfer surface is made of copper and is 100mm in length and 40mm in width and 15mm in thickness. The experimental condition of spray are as follows: temperatures of the water droplets are T=20~$80^{\circ}C$ and droplets volume fluxes are D=0.001565~0.010438$m^3/m^2s$. Next, correlating equations for the heat transfer characteristics of spray cooling in the high temperature region are developed from the effects of droplets volume flux and the surface temperature of heat transfer plate.

• Journal of ILASS-Korea
• /
• v.15 no.4
• /
• pp.202-207
• /
• 2010

Mist cooling is widely employed as a cooling technique of high temperature surfaces, and it has heat transfer characteristics similar to boiling heat transfer which has the convection, nucleate and film boiling regions. In the present study, mist cooling heat transfer was experimentally investigated for the mist flow impacting on the heated surfaces of mico-fins. The mist flow was generated by supersonic vibration. Experiments were conducted under the test conditions of droplet flow rate, $Q=6.02{\times}10^{-9}{\sim}3.47{\times}10^{-8}\;m^3/s$ and liquid temperature, $T_f=30{\sim}35^{\circ}C$. From the experimental results, it is found that an increase in the droplet flow rate improves mist cooling heat transfer in the both case of smooth surface and surfaces of micro-fins. Micro-fins surfaces enhance the mist cooling heat transfer. Besides, the experimental results show that an increase in the droplet flow rate decrease the heat transfer efficiency of mist cooling.