• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7990-8000
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• 2015

Plant factories are plant cultivation systems which produce farm products uniformly under the controlled environmental condition regardless of seasons and places. Thermal flow in the plant factory is an important parameter in cultivating plants. In this research, we study thermal flow characteristics for a hybrid plant factory with multi-layer cultivation shelves using computer simulation techniques. In order to obtain numerical solutions for thermal flow characteristics, a finite volume method was applied. We consider a low-Reynolds-number ${\kappa}-{\epsilon}$ turbulence model, incompressible viscous flows, and pressure boundary conditions for numerical simulation. Commercial software Solid Works Flow Simulation is then used to investigate characteristics of thermal flows in the plant factory applying several different inflow air velocities and arrangements of cultivation shelves. From numerical analysis results, we found that temperatures in cultivation shelves were uniformly distributed for Case 3 when the inflow air velocity was 1.6 m/s by using a blower in the plant factory. However in Case 1 lower temperature distributions were observed in test beds, TB2 and TB3, which indicated that additional temperature control efforts would be required. Average shelf temperature increased by $3^{\circ}C$ using artificial light source (DYLED47) with 50% blue and 50% red LED ratios. Korea Academia-Industrial cooperation Society.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.131-131
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• 1999

비정질 카본 박막은 다이아몬드와 유사한 높은 경도, 내마모성, 윤활성, 전기절연성, 화학적 안정성, 그리고 광학적 특성을 가진 재료로서 플라즈마 CVD를 이용한 합성방법으로 제조된 박막이 주로 연구되고 있다. 본 연구에서는 마그네트론 스퍼터링을 이용하여 다양한 조건의 카본 박막을 제조하였다. 카본 박막의 제조는 이온빔이 장착된 고진공 증착 장치를 이용하였고 시편의 청정시 사용된 이온빔의 조건은 빔 전압이 500V, 빔 전류는 0.1mA/cm2로 기판 청정을 거친 후 DC 마그네트론 스퍼터링을 이용하여 흑연을 증발시켜 박막을 제조하였다. 기판과 타겟의 거리는 13cm로 고정시킨 후 타겟 전류는 1A로 유지하면서 30분간 증착하였다. 기판은 Si-wafer와 glass를 주로 사용하였으며 기판 인가전압, 아세틸렌 유량, 기판 온도등을 변화시켜가면서 각각 카본 박막을 제조하였다. 비정질 카본박막의 막은 평균 두께는 0.4~1.2$\mu\textrm{m}$이며 SEM을 이용하여 단면의 성장구조를 관찰하였다. 라만 분광분석과 FTIR 분광분석을 통하여 비정질 카본 박막의 결합특성을 조사하였고 scratch tester를 이용하여 박막의 밀찰력을 관찰하였다. 제조된 박막의 두께는 아세틸렌 가스 이용시 1$\mu\textrm{m}$ 이상의 박막의 제조가 가능하였으며 카본 박막의 라만 분광특성은 고체 탄소 물질의 S와 G-peak으로 구성되어 있으며 기판 인가전압, 아세틸렌 가스 유량 변화에 따른 peak의 위치 이동 및 FWHM의 변화를 관찰하였다. RFIR 결과는 아세틸렌 가스의 유량이 증가에 따라 C-H 결합 분포가 증가며 기판 인가 전압이 증가할수록 C-H 결합분포가 감소하는 경향이 나타냈다. 이는 이온 충돌 효과에 따라 결합력이 약한 C-H 결합이 우선적으로 파괴되는 현상으로 생각되어 진다. Scartch tester 측정 결과 박막의 밀착력은 실험조건에 따른 경샹성은 보이고 있지 않으나 10N 정도이며 60N 이상의 강한 밀착력을 가진 박막도 제조되었다.

• Journal of the Korean Institute of Gas
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• v.25 no.1
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• pp.14-19
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• 2021

The change of the vorticity and the temperature distribution in heat exchanger tube bank were analyzed for the flows with the constant inlet velocity and the sinusoidal inlet velocity. The flow frequency characteristics were examined by analyzing power spectral density of lift and drag at a typical circular tube in the tube bank. Karman vortex street could be seen at the upstream region of tube bank for the case of constant inlet velocity. It could be seen that the Karman vortex street was affected by the change of inlet velocity near the circular tubes for the case with the sinusoidal inlet velocity. It was observed that the unsteady temperature distributions for both inlet velocity conditions had almost the same motion as the flow vorticity behavior. The flow frequency for the case with the constant inlet velocity is 37.25Hz, and that with the sinusoidal inlet velocity, the flow frequency is 18.63Hz, which is equal to the sinusoidal inlet velocity. The mean surface Nusselt number(Nu) for overall heat exchanger tube bank was 1051 for the case with the constant inlet velocity and 1117 for the case with the sinusoidal inlet velocity. From the result of heat transfer analysis, it could be seen that Nu with the sinusoidal inlet velocity showed 6.3% increase than that with the constant inlet velocity.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.156-162
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• 2010

3-D CFD(Computational Fluid Dynamics) work were carried out to investigate the combustion characteristics in a boiler depending on the variations in air supply condition. For the gas temperature, $O_2$, NO, SOx at the outlet of economizer, the predicted values were been compared with the measured data. With the verified CFD model, the effects of air flow rates through SOFA(Separated Over Fire Air) and CCOFA(Closed Coupled Over Fire Air) on the combustion behavior in a boiler were simulated, and the distributions of NOx and gas temperature were mainly compared each other. The change in SOFA air flow rate gave the more sensitive effect on NOx than that in CCOFA. The distributions of gas temperature at convection path are differed with the changes in SOFA and CCOFA flow rate, so the combustion modification such as yaw anlge adjustment are required to get an enhanced gas temperature distribution.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.92-97
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• 2005

A series of combustion test was done to verify the optimization result of a gas generator for a 10 ton thrust liquid rocket engine. An injector element is F-O-F impinging type injector and the test was conducted with kerosene/LOX propellants. Test results of combustion temperature and pressure show a very good agreement with optimal design result and verify that the design method was properly established. And turbulence ring revealed its effectiveness in enhancing combustion gas mixing and temperature difference in the radial direction showed only less than 15K. Also turbulence ring induced only 3.2% pressure loss in the combustion chamber, which is far less than conventional level observed in a gas turbine engine. Axial temperature distribution also shows that turbulence ring could effectively reduce about 10% or more in gas generator length if its location is properly selected.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.1012-1022
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• 1989

Numerical analysis has been performed on three-dimensional natural convection in inclined concentric annuli with the nonuniform temperature distribution of the inner cylinder. The governing equations are numerically solved by successive over-relaxation methods for various inclination angles at $R_{a}$=3*10$^{4}$, $P_{r}$=7.0 and $r_{1}$ / $r_{2}$=0.6. Temperature and Nusselt number distributions are obtained and calculated results are compared with those of published uniform temperature distributions. It is found that the mean Nusselt numbers for the nonuniform temperature distributions increase more than those for the uniform temperature distributions by about 9. 6% at .delta.= 0.deg., 7.5% at .delta. = 30.deg. and 4.6% at .delta. = 60.deg.. In the case of .delta. = 0.deg., the maximum local Nusselt numbers on the inner and outer cylinder walls show at .xi. = 0.5, 1.5 of .psio=100 .deg. and .xi. = 0.4, 1.6 of .psi. = 180 .deg.. But in the case of .delta. = 30.deg. and .delta. = 60.deg., the maximum local Nusselt numbers on the inner and other cylinder walls show at .xt. = 0.0 of .psi. = 180 .deg. and .xi. = 2.0 of .psi. = 180 .deg...

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.19-31
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• 2022

With the advent of technologies based on big data, the trend of electronics towards high performance and high integration density continues. However, this development of electronics suffers from overheating issues, which seriously threaten the reliability of the devices. To develop effective strategies for thermal management, it is crucial to accurately evaluate the temperature distribution and design the heat dissipation path within the device in the operating condition. This paper introduces thermoreflectance microscopy that can observe the temperature distribution of a device with high spatial and temporal resolutions in a non-contact way. Specifically, the working principle and various forms of thermoreflectance microscopy are presented along with the latest research trends to improve the temperature, space, and time resolutions. We further review several examples in which thermoreflectance microscopy is applied to investigate the temperature and thermal characteristics of electronic devices.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.6
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• pp.477-486
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• 2017

For the analysis of the optical characteristics of electrodeless lamps, all the lamp surface temperatures have been treated the same. However, the interpretation of optical properties in this way has not been sufficient in terms of accuracy. In this paper, to overcome this problem, we divided the inside of the bulb into two parts, hot spot and cold spot, and analyzed the density difference of mercury by different temperatures. Here, it is assumed that the distribution of temperature and density is linear. The effect of optical characteristics through redistribution of hot spot and cold spot density was analyzed. It was also confirmed that the ratio of the density of the redistributed discharge gas has a great influence on the saturation of the optical characteristics. Therefore, it is proved that the design method through the domestic setting is very useful in the actual design, and the method for shortening the time for stabilizing the optical characteristics is obtained.

• Solar Energy
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• v.17 no.2
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• pp.75-89
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• 1997

In this paper, the operating thermal characterictics of liquid-ice was expeimentally investigated in an adiabatic and a non-adiabatic direct contact liquid-ice heat exchanger. Experiments were carried out varing inlet temperature, Ice Packing Factor, and the flow rate of heat transfer fluid. The higher inlet temperature and the more much inlet flow rate, thermal stratification in liquid-ice heat exchanger was established faster. In the case of adiabatic ice storage tank, temperature distribution was a little higher at all conditions than that of non-adiabatic one. The ratio of latent energy to total discharge energy($E_{\lambda}/E_[tot}$) was about 80%, and the discharge of latent heat energy was appeared rapidly as inlet temperature and flow rate were higher.

• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.46-52
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• 2008

The instrumentation was studied in order to measure aerodynamic performance and efficiency of a compressor as a component of a 5MW-class gas turbine for power generation. In case of an axial compressor, the distributions of static pressure on a casing can be obtained by averaging at each stage and those of total pressure and temperature in the flow field of the compressor can be measured with a Kiel temperature probe. In case of a centrifugal compressor, the static pressures at the hub and the tip, respectively, of an impeller exit are considerably different, so the pressures need to be measured at both positions and thereafter averaged. The distributions of static pressures in a diffuser and a deswirler are measured at ten positions along five streamlines in one pitch. In addition the flow field can be measured in detail by 5-hole Pitot tube in order to analyze the flow characteristics of the core flow region and wake region and the rotor-stator interaction of the compressor.