• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.85.1-85.1
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• 2010

캐스케이드형 연료전지 시스템에 있어서 각 스택의 단에서 전기화학반응에 의해 생성된 물을 분리하여 적절하게 배출시켜주는 것은 스택의 성능 및 내구성 향상을 위해 매우 중요하다. 이를 위해 연료전지 스택 각 단의 상이한 조건에 맞는 기액분리기의 설계가 필요하다. 유량에 따른 기액분리기의 부피와 원활한 연료 가스와 생성수의 분리를 위한 내부구조 및 입구 속도 등의 변수들에 따라 기액분리기의 성능 뿐만 아니라 연료전지 시스템 전체의 성능에 영향을 준다. 그러나 기액분리기의 폐쇄적 구조 때문에 실험을 통해 내부의 거동 및 현상을 파악할 수 없어 앞서 언급한 변수들의 효과를 확인할 수 없는 문제점이 있다. 이에 CFD(Computational Fluid Dynamics, 전산유체역학)를 활용하여 각 조건에 따른 기액분리기 내부의 현상을 파악하고 이를 통해 기액분리기 설계를 최적화하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.170-170
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• 2009

AIP(Air Independent Propulsion)시스템에 적용되는 연료전지 스택의 경우 연료의 이용율을 극대화시키는 것이 매우 중요하다. 일반적인 연료전지 스택은 물배출과 성능의 안정화를 위해 이론적 요구량보다 양론적으로 많은 양을 공급하여, 반응에 사용되지 않고 배출되는 연료 가스가 많아 이용율이 낮다. 여러 단으로 구성되어 전 단에서 사용하고 남은 연료 가스를 다음 단에 재공급하여 사용하는 케스케이드 구조의 연료전지 스택을 적용하게 되면 연료이용율을 90% 이상으로 높일 수 있다. 그러나 연료전지 스택에서 반응에 의해 발생한 물과 응축된 가습수가 재공급되면 연료전지 스택의 성능과 내구성에 악영향을 주는 플러딩현상이 발생하게 된다. 반면 반응수와 응축수를 제거할 때 스택에 재공급되는 연료 가스의 가습수가 같이 제거되면 낮은 가습도로 스택에 공급되는 문제점도 있다. 따라서 연료 가스의 가습도를 잘 유지하면서 액화된 물만 원활하게 제거할 수 있는 기액분리기의 개발이 필요하다. 본 연구에서는 CFD(Computational Fluid Dynamics)해석을 활용하여 다양한 디자인의 기액분리기를 설계하고 실험을 통해 각 디자인의 장단점을 분석하였다. 결과를 바탕으로 최적의 기액분리기를 개발하고 제작 및 평가를 통해 성능을 검증하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.297-305
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• 2017

Air-source heat pumps are widely used in residential heating systems. However, the decrease in the capacity of the heat pump is unavoidable when operating at very low and high ambient temperatures. The vapor injection technique is considered a promising technology to overcome this problem. Recent research on vapor injection cycles have mainly adopted a scroll compressor with an internal heat exchanger at severe operating conditions. This study measured the COP and EER of a gas injection heat pump using a flash tank with an inverter-driven rotary compressor at severe operating conditions. Compared to non-injection heat pumps, the heating capacity and COP of the gas injection heat pump improved up to 15% and 2.9%, respectively, at outdoor temperatures of $-10^{\circ}C$ to $7^{\circ}C$. The cooling capacity of the gas injection heat pump was 11% higher than the non-injection heat pump at an outdoor temperature of $35^{\circ}C$. At the same time, the EER of the gas injection heat pump was similar to that of the non-injection heat pump.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3215-3220
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• 2007

Gas-liquid separator has been designed for the sake of reducing expenses associated with production operations. To date, a number of gas-liquid separators have been installed and put to use for various applications. Despite the advantages of simple and compact configuration of separator with no moving part, its efficient operation is limited in terms of total pressure losses, separation performance and flow-induced noise and vibration, which are closely associated with the very complicated flow phenomena involved. In the present study, a gas-liquid centrifugal separator with a swirl vane is investigated for the purpose of water separation from compressed moisture air. The 3D Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Based upon the obtained solutions, tangential velocities, centrifugal forces, vortices and total pressure losses are analyzed to find out the best design parameters. From the present study, several attempts are made to improve the performance of conventional separators of centrifugal type.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.8
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• pp.425-432
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• 2009

In this study, the improvement of cooling capacity by applying gas injection technique in a two-stage heat pump using R410A was experimentally investigated. A twin rotary type compressor with gas injection was applied to the heat pump system. The optimum refrigerant charge for the injection and the non-injection cycles was selected to achieve the maximum COP at the cooling standard condition. The injection cycle showed less optimum refrigerant charge than that of the non-injection cycle. The cooling performances of the injection and the non-injection cycles were measured and compared by varying compressor frequency from 40 to 90 Hz. The cooling capacity of the gas injection cycle was 1.6% -11.3% higher than that of the non-injection cycle. The COP of the gas injection cycle was 13.7% to 28.9% higher than that of the non-injection cycle at the same cooling capacity. The heat pump system showed stable operation after 30% of the injection valve opening.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.229-235
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• 2011

This research aims todevelopa compression/absorption hybrid heat pump system using an $NH_3/H_2O$ as working fluid.The heatpump cycle is based on a combination of compression and absorption cycles. The cycle consists of two-stage compressors, absorbers, a desorber, a desuperheater, solution heat exchangers, a solution pump, a rectifier, and a liquid/vapor separator. The compression/absorption hybrid heat pump was designed to produce hot water above $90^{\circ}C$ using high-temperature glide during a two-phase heat transfer. Distinct characteristics of the nonlinear temperature profile should be considered to maximize the performance of the absorber. In this study, the performance of the absorber was investigated depending on the capacity, shape, and arrangementof the plate heat exchangers with regard tothe concentration and distribution at the inlet of the absorber.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.51-55
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• 2011

In this study, the liquid-vapor (L-V) separator equipped with liquid-level meter is developed. In the developed L-V separator, the flange is designed to be attachable so that the separator can be flexibly applied under any cases where the volumetric of L-V separator is varied by the system requirement. The leak-tightness between the attachable flange and the chamber is experimentally confirmed with the use of double groove indium wire sealing even under the high pressure up to 20 bar. In addition, the liquid-level meter is designed and fabricated to figure out the inner state of L-V separator. It consists with 19 carbon composition resistors in series. All resistors are separately calibrated in the temperature range from 77 K to 200 K. The performance of the L-V separator and the liquid-level meter is investigated with experimental tests, and the result is presented in this paper.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1367-1373
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• 2011

This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than $90^{\circ}C$ when the heat source and sink temperatures were $50^{\circ}C$. Experiments with various $NH_3/H_2O$ mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific $NH_3$ concentration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.2055-2061
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• 2013

Recently, an understanding of new sources of liquid hydrocarbons such as bio-ethanol is economically very important. Successful design of distillation columns in a separation process depend on the availability of accurate vapor-liquid equilibrium data. For the binary system of Ethanol/3-methyl-l-butanol mixture, isothermal Vapor-liquid equilibrium data were measured at temperature of 50, 55, 60, 65, 70, 75 and $80^{\circ}C$. An empirical relation to predict Vapor-liquid equilibrium data was obtained from the above measured data. The predicted values are compared with the measured ones to be in a good agreement within accuracy of ${\pm}0.0005$, ${\pm}0.0022$.

• Journal of Animal Environmental Science
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• v.10 no.3
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• pp.141-154
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• 2004

The solar powered water pump is very ideal equipment because solar power is more intensive when the water is more needed in summer and it is very helpful in the rural area, in which the electrical power is not available. The average so]ar radiation energy is 3.488 kWh/($m^2{\cdot}day$) in Korea. In this study, the automatic control logic and system of the water pump driven by the radiation energy were studied, designed, assembled, tested and analyzed for realizing the solar powered water pump. The experimental system was operated automatically and the cycle was continued. The average quantity of the water pumped per cycle was about 5,320 cc. The cycle time was about 4.9 minutes. The thermal efficiency of the system was about $0.030\%$. The pressure level of the n-pentane vapour in flash tank was 150$\%$450 hPa(gauge) which was set by the computer program for the control of the vapour supply. The pressure in the condenser and air tank during cycles was maintained as about 600 hPa and 1,200 hPa respectively. The water could be pumped by the amount of 128kg/($m^2{\cdot}day$) with the efficiency of $0.1\%$ and the pumping head of 10 m for the average solar energy in Korea.