• 태양에너지
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• 제19권4호
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• pp.11-20
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• 1999

The study on ice thermal storage system is to improve total system performance and increase the economical efficiency in actual air-conditioning facilities. To obtain the high charging and discharging efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therefore the process flow must be piston flow in the cylindrical type. In the influence of the inlet port type, the inflowing water in the distributor type diffuses through the whole storage tank more than in the slot type. In case of the flow process in the ice storage tank, the upward flow type in the charging process and the downward flow type in the discharging process make the stratification well, thereby the loss of energy wored be smaller. The influence of the inlet temperature difference and the change of the inlet flow rate is intensive when the temperature difference is larger, the flow rate is smaller in case of charging and the results are opposite in case of discharging with the reason that the good coduction condition. The total effeciency of the ice thermal storge system is 73% on condition that the porosity in the thermal storage tank is 0.55. This result shows that cylinderical ice storage tank has better storage capacity than rectangular type in case of the same porosity.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 1997년도 추계 학술논문발표회 논문집
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• pp.31-36
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• 1997

Strength test using strain rosette gage have been conducted to investigate safety of an auxiliary tank in a high-pressure air compressor. Thickness of auxiliary tanks in 6063-T5 aluminum at toy are 9mm and 17mm. The result of strength test make a comparison the design in strength of materials by nominal stress and the design in fracture mechanics with consideration of crack size. Summarizing the result: Comparing with the safe working pressure of the strength test and that of the design method in strength of materials by nominal stress with the experimental values, it makes difference 11% and 39% for 9mm and 17mm thickness of auxiliary tanks, respectively, and that of the design method by fracture mechanics, it makes difference 4％ and 5% for them, respectively. It is confirmed that the design by fracture mechanics is more economical and safe design than the design in strength of materials by nominal stress.

• 설비공학논문집
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• 제13권7호
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• pp.549-556
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• 2001

Heat flow characteristics during hot water extraction process was studied experimentally. Data were taken at various outlet port type for the fixed inlet port type, inlet-outlet temperature differences and mass flow rates. In this study, the temperature distribution in a storage tank and an outlet temperature were measured to predict a flow pattern in the storage tank, and a hot water extraction efficiency was analysed with respect to the variables dominating a extraction process. Experimental results show that the extraction efficiency is high in a low flow rate in case of using modified distributor I(MDI) as a outlet port type.

• 상하수도학회지
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• 제18권3호
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• pp.307-311
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• 2004

The objective of this work is to evaluate the hypothesis that a good technique for supplying oxygen to the saturated zone in the presence of light nonaqueous phase liquid (LNAPL) pool contamination at the water table is to pass air through the unsaturated zone above the pool. This hypothesis was evaluated in experimental studies performed using a bench-scale, sand-tank reactor, Steady-state abiotic experiments in the sand-tank reactor with air flowing through the reactor headspace demonstrated that oxygen supply through the water table interface into the saturated zone was enhanced when an LNAPL (dodecane) pool was present at the water table. These experimental results confirmed the hypothesis that an LNAPL pool can serve as a high concentration oxygen source to the oxygen-limited area beneath the pool and, as a result, enhance the in situ biodegradation rate.

• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.14-26
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• 1998

This paper deals with approximate analytical solutions for the two-region one-dimensional model describing the charging process of stratified thermal storage tanks at variable inlet temperature with momentum-induced mixing. An arbitrarily increasing inlet temperature is decomposed into inherent step changes and intervals of continuous change. Each continuous interval is approximated as a finite number of piecewise linear functions, which admits an analytical solution for perfectly mixed region. Using the Laplace transform, the temperature profiles in plug flow region with both the semi-infinite and adiabatic ends are successfully derived in terms of well-defined functions. The effect of end condition on the solution proves to be negligible under the practical operating conditions. For a Quadratic variation of inlet temperature, the approximate solution employing a moderate number of pieces agrees excellently with the exact solution.

• 설비공학논문집
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• 제20권9호
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• pp.631-636
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• 2008

Solar thermal systems are recently refocused by higher oil prices, but did not completely restore the people's confidence owing to the past bad systems. Several types of solar water heating systems were analyzed in characteristics and some proper systems were proposed under Korean climates and system scale. As a small system, natural circulation system should be installed only in a southern region of Korea, with a freeze protection valve instead of heating coil for freeze protection. In most area of Korea, the forced circulation type with a heat exchange coil inside a thermal storage tank or with a spiral-jacketed storage tank, proposed and verified by the authors, has a merit of stable performance and freeze protection.

• 설비공학논문집
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• 제13권2호
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• pp.80-87
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• 2001

Microencapsulated PCM particles are mixed with distilled water and utilized to evaluate its characteristics and performance as a thermal storage medium transporting heat. For the present study, tetradecane(C$_14H_30, T_m=5.5^{\circ}C$) is capsulated in the core with the melamine of its surface. The size of particles is well-controlled under 10${\mu}{\textrm}{m}$ in the way of in-situ polymerization with melamine-formaldehyde resin. For the experiment, the concentrations of slurries are prepared for 20wt%, 30wt%, and 40wt%. The results are compared with those of water and 100% tetradecane oil. The pure water and tetradecane start solidifying within 20 minutes after introducing cooling water into the thermal storage tank whose tank whose flow rates are varied by 125cc/min, 250cc/min, and 500cc/min. However, MicroPCM slurries are required relatively longer period of time for their phase change than pure phase change materials. That is, the entrained MicroPCM particles control its heat transfer in terms of natural convection and conducting to them.

• 생물환경조절학회지
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• 제21권3호
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• pp.163-169
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• 2012

관비재배 및 수경재배시 비료를 녹일 때 소요되는 시간과 노동력을 절감하고, 작업의 안전성 확보와 자동화를 가능하게 할 수 있는 장치의 개발을 위해 본 실험을 실시하였다. 실험은 세 종류로 수행되었다. 먼저, 효과적인 비료용해 방법을 구명하기 위해 수중펌프를 양액 통 속에 두고 양액 통의 입구에 삼베포를 깐 거름망을 설치하여 물을 스프레이하여 비료를 녹이는 방법(Spray), 수중프로펠러를 이용하는 방법(Propeller), 수중펌프를 양액 통 속에 넣어 물의 흐름을 만들어 주는 방법(Submerged), 에어컴프레서를 이용하여 양액 통 속에 공기흐름을 만들어 비료를 용해하는 방법(Airflow) 등 4개의 처리를 두고 실험하였다. Spray 처리에서 가장 시간이 짧게 소요되는 것으로 조사되었으나 농가가 실제로 적용하는데 어려움이 있어서, Spray 처리 다음으로 비료를 녹이는 시간이 짧고, 노동력을 절감할 수 있으며 양액제조 과정을 자동화 하는 것이 용이할 것으로 사료되는 Airflow 처리를 선택하였다. 두 번째 실험에서는 Airflow 처리에서 사용한 재질과 분지관수를 개선한 6지관 및 8지관 장치를 제작하여 비교 실험했는데, 6지관 장치가 비료용해시간이 짧고, 양액탱크의 입구 크기에 관계없이 사용이 가능하며, 제작이 용이하여 가장 효과적인 장치로 판단되었다. 세 번째 실험에서는 개발된 6지관 장치를 이용하여 비료를 용해하는데 소요되는 시간을 조사하여 경제성을 분석하였는데, 농가에서 수중펌프를 이용하여 비료를 용해하는 방법보다 시간은 1/8배 절약할 수 있으며 경제성이 큰 것으로 나타났다. 아울러 $KNO_3$, $Ca(NO_3)_2{\cdot}4H_2O$, Fe-EDTA 등의 용해특성을 조사했다.

• 한국태양에너지학회 논문집
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• 제35권5호
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• pp.21-29
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• 2015

In this study, the performance of hybrid solar air-water heater when the heated air was used as inlet air was investigated during air and liquid were heated simultaneously. Temperature difference between inlet air and ambient was set as $0^{\circ}C$, $13^{\circ}C$ and $22^{\circ}C$ and it was maintained during the daily operation. As a result, thermal efficiency of liquid heating was increased when the inlet air temperature was increased and heat gain of the water in heat storage tank was also increased with increment of temperature difference between inlet air and ambient temperature. On the contrary to this, the decrement of air heating efficiency and total efficiency of collector was confirmed with increment of inlet air temperature and it is considered that heat gain of liquid side is lower than heat loss of air side that occurring by using heated air as inlet air of collector. So, from these results, maximum temperature that the liquid in heat storage tank can reach was expected to increase if the return air or any heated air was used as inlet air. But air and total efficiency of hybrid solar air-water is decreased, so using outdoor air as inlet air is considered as better way on perspective of using of solar thermal energy by hybrid solar collector. However, it is hard to conclude that using outdoor air is better than heated air on the perspective of energy saving of building because the performance of heat storage performance was increased even air and total thermal efficiency was decreased, so the necessity of more profound consideration about these result in further research was confirmed for putting the hybrid solar air-water heater to practical use.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2003년도 하계학술대회 논문집
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• pp.250-250
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• 2003