• 한국조경학회지
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• 제31권3호
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• pp.58-73
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• 2003

It is well known that urban environment affects climate, as we can see in the quality of bio-climate. However, climate has not been recognised properly in the urban planning process. The role it flays needs to be examined for better urban environment. The main objective of this study is to investigate the climate-ecological priority area which produces cold fresh air and thermal induced wind circulation between rural and urban areas. The objective is also to improve the quality of bio-climate and wind circulation at blocked urban areas. This paper uses the measurement and analysis method of wind direction and wind speed in order to investigate the climate-ecological priority area and cold fresh air corridor. In this study, local climate conditions i.e. wind speed, wind direction, temperature, humidity etc., were measured at nine fields and analyzed. On the basis of the climate measurement, the climate ecological priority areas were delineated; These will be assigned as climate-ecological conservation areas.

• 생물환경조절학회지
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• 제16권4호
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• pp.291-296
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• 2007

이 연구는 순환팬에 의해 만들어지는 수평적인 공기흐름이 환경요인들의 수평 및 수직분포에 미치는 영향을 조사하기 위해 수행하였다. 순환팬 가동 유무에 따라 기류 속도, 기온, 상대습도 및 $CO_2$농도의 3차원 분포를 측정하였다. 온실내 기상인자 분포의 균일성은 외기온이 낮아짐에 따라 감소하였다. 무처리시 기온 편차는 4.7, 습도 편차는 19%이었는데 팬을 가동한 경우 그 편차들은 각각 2.2, 6.3%로 감소하였다. 팬 용량이 증가할수록 측점간 기온 편차가 줄어들었는데, 온실 바닥면적당 $0.0104m^3{\cdot}s^{-1}$ 용량의 팬으로 온실내 적정한 공기 유동을 만들 수 있었다. 기온 및 $CO_2$ 농도의 수직분포는 높이나 팬 용량에 관계없이 상당히 균일한 것으로 나타났다. 폭 방향의 기온 편차를 줄일 수 있는 팬 배치와 소용량의 팬을 다수 설치했을 때의 효과에 대한 연구가 더 필요할 것으로 생각된다.

• 한국가시화정보학회지
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• 제18권2호
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• pp.18-27
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• 2020

Air lift pump operated by buoyancy is mainly used for the continuous circulation and the purification of fluids. In this study, the computational flow analysis has been performed with the geometric and operating conditions of the air lift pump. The numerical data from the analysis have been verified by comparing with the previous experimental data. The following results are obtained which advance the efficiency of the air lift pump. As the submergence length of pipe increases and the pipe length over the water surface decreases, the non-dimensional mass flow ratio increases in both cases. When the position of the air injection hole is within the pipe, the circulation range of the surrounding fluid becomes widened with the distance between the air injection hole and the pipe inlet relatively becoming narrower. It is more efficient both when the air injection velocity is at 10 m/s and at 15 m/s, and when the diameter of the pipe with holes is doubled near the water surface. It is expected that these results can be provided as fundamental data for operating the air lift pump.

• KSBB Journal
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• 제7권1호
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• pp.59-65
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• 1992

외부 순환식 공기리프트 반응기에서 기상유속과 액상의 점도를 변수로 하여 기체체류량과 액체의 순환시간, 혼합시간, 순환속도 및 축방향분산계수를 측정하여 다음과 같은 결론을 얻었다. 1. 기체체류량은 기체유속이 증가함에 따라 증가 하였으며, 점도가 증가함에 따라서는 약간 감소하는 경향을 보였다. 또 기체유속이 증가함에 따라 상승관에서는 기체체류량의 증가율이 감소한 반면 하강관에서는 증가하였다. 2. 기체유속이 증가함에 따라 순환시간 및 혼합시간은 초기에 급격히 짧아지다가 거의 일정한 값을 나타내었으며, 액체의 점도가 증가함에 따라 순환기산과 혼합시간은 모두 증가하였다. 3. 순환 액체의 속도는 기체의 속도에 따라 초기에 급격히 증가하나 기체속도가 약 5cm/sec이상이 되면 그 증가율이 매우 둔화되었으며, 점도가 증가함에 따라 약간 감소함을 알 수 있었다. 또한 압력수지식으로 예측한 이론값과 실험값은 낮은 기체유속 영역에서는 잘 일치하였으나 기체유속이 증가함에 따라 실험값이 이론값보다 작은 값을 나타내었다. 4. 기체유속이 증가함에 따라 Bodenstein number는 감소하였고, 축방향분산계수는 증가하였으며, 점도가 증가함에 따라 약간 감소하는 경향을 보였다. 본 실험범위에서 분산이 많이 일어나mixed folw에 근접함을 알 수 있었다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.639-646
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• 2000

Hot air heater with light oil combustion is the most common heater for greenhouse heating in the winter season in Korea. However, since the heat efficiency of the heater is about 80%, considerable unused heat in the form of exhaust gas heat discharges to atmosphere. In order to capture this exhaust gas heat a heat recovery system for plant bed heating in the greenhouse was built and tested in the hot air heating system of greenhouse. The system consists of a heat exchanger made of copper pipes, ${\phi}\;12.7{\times}0.7t$ located inside the rectangular column of $330{\times}330{\times}900mm$, a water circulation pump, circulation plastic pipe and a water tame The total heat exchanger area is $1.5m^2$, calculated considering the heat exchange amount between flue gas and water circulated in the copper pipes. The system was attached to the exhaust gas path. The heat recovery system was designed as to even recapture the latent heat of flue gas when exposing to low temperature water in the heat exchanger. According to performance test it can recover 45,200 to 51,000kJ/hr depending on the water circulation rates of 330 to $690{\ell}$/hr from the waste heat discharged. The exhaust gas temperature left from the heat exchanger dropped to $100^{circ}C$ from $270^{circ}C$ by the heat exchange between the water and the flue gas, while water gained the difference and temperature increased to $38^{circ}C$ from $21^{circ}C$ at the water flow rate of $690{\ell}$/hr. And, the condensed water amount varies from 16 to $43m{\ell}$ at the same water circulation rates. This condensing heat recovery system can reduce boiler fuel consumption amount in a day by 34% according to the feasibility study of the actual mimitomato greenhouse. No combustion load was observed in the hot air heater.

• 설비공학논문집
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• 제23권9호
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• pp.595-603
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• 2011

In this study, an effort has been made to analyze the subcooled boiling heat transfer in a natural circulation vertical evaporator. To verify the analysis, a small-scale model was made and tested. The friction correlation by Ueda, void fraction and quality correlation by Saha and Zuber along with the superposition heat transfer model by Rohsenow yielded a satisfactory agreement with the model test data. The analysis was extended to simulate a 1 ton/day concentration system. Comparison with the test results of 1 ton/day prototype revealed that the data were overpredicted by 13%. The capacity of the prototype was 1.2 ton/day with COP of 5.77.

• 한국환경과학회지
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• 제10권3호
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• pp.187-194
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• 2001

For the purpose of predicting air pollutants concentration in Pusan coastal urban, we used an Eulerian model of flow and dispersion/chemistry/deposition process considering SST effects which estimate through POM. The results of air quality model including emission from various sources show that the seasonal variation pattern of respective pollutants was affected by the seasonal SST fields and local circulation. Horizontal deviation of diurnal SST was 2.5~4K, especially large gradients in coastal region. Through numerical simulation of wind fields we predicted that local circulation prevailed during daytime in summer and nighttime in winter. So high concentration distribution showed toward inland in spring and summer seasons, while high concentration distribution showed at inland near coast in autumn and winter.

• 설비공학논문집
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• 제23권11호
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• pp.762-768
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• 2011

We use floor radiant heating system in the house of commons in winter Floor radiant heating system, which transfer heat by radiation, is one of the energy efficient and comfortable systems that. Floor radiant heating system is configured to be controlled by the room for energy-saving. Proper flow rate to a comfortable heating in the room is important. However, Using a constant speed circulation pump in separate rooms, heating system may cause an imbalance because of the difference of length of coil when operating in the rooms. In this study, our Research team examined heating imbalance due to the variation length through the coil length changes and flow control of the circulation pump.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2589-2593
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• 2008

In a fuel cell vehicle using polymer electrolyte membrane fuel cell(PEMFC), hydrogen is over-supplied to gain higher stack efficiency. So it is needed considering fuel efficiency to re-circulate hydrogen which is not reacted in stack. And to re-circulate hydrogen, a blower or an ejector is used. Ejector re-circulation system has several merits compared with blower system, for example no parasite energy, simple structure and no lubrication system. But the secondary flow of an ejector in fuel cell vehicle, has high humidity because of crossover problem in stack. Therefore in this paper, ejector is designed by 1-D modeling and CFD with the primary and secondary flow of hydrogen. And the ejector which has the primary and secondary flow of air, is designed to have the same Reynolds number and Mach number at the nozzle exit as the hydrogen ejector's. And this air ejector is tested while the humidity of the secondary flow is varied.

• 설비공학논문집
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• 제16권3호
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• pp.287-292
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• 2004

An experimental investigation was carried out to study the performance of a bubble pump for the diffusion absorption refrigerating system. Ammonia was used as the refrigerant and the helium was charged in order to balance the pressure between the low and high pressure side. As experimental variables, the concentration of ammonia charged into system, heat input, and the pressure of helium were selected. Experimental results show that the generation rate of ammonia vapor and the circulation rate of diluted ammonia solution were increased as the heat input increases, but the ratio of the solution to vapor flow rate was decreased. The generation rate of refrigerant vapor and the circulation rate of diluted ammonia solution increased as the system pressure decreased. Finally under the condition of 25 bars, the concentration of rich ammonia solution was not affected by the generation rate of ammonia vapor and the circulation of diluted ammonia solution.