• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.626-629
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• 2008

In this study, a geothermal power generation system using the Kalina cycle was investigated by the simulation method. The Kalina cycle system can be used for the utilization of a low-temperature heat sources such as geothermal and industrial waste heat that are not hot enough to produce steam. The sea/river water can be considered as a cooling media. A steady-state simulation model was developed to analyze and optimize its performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump were modelled by an isentropic efficiency, while a condenser, an evaporator and a regenerative heat exchanger were modeled by UA-LMTD method with a counter-flow assumption. The effect of the ammonia fraction at the separator inlet on the cycle performance is investigated in detail.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10c
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• pp.72-76
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• 2006

센서 네트워크에서는 싱크에서 센서로 자료요청을 위한 쿼리를 발송하고 감지된 데이터를 싱크로 수집하는 방법은 여러 가지가 있을 수 있다. 그러나 어떠한 쿼리 최적화 방법을 사용하느냐에 따라 센서 네트워크의 성능이 달라질 수 있다. 본 논문에서 센서 네트워크 상에서 영역질의를 처리하는 분산 색인 방법을 제안하였다. 본 연구에서 제안한 DIMTree(Distributed Index Management Tree)는 센터에서 데이터를 수집하기 위하여 모든 영역에 쿼리를 배포할 필요가 없이 질의에 적합한 지역에서만 쿼리를 배포하여, 자료 전송 및 수집으로 인한 데이터 전송량을 줄임으로써 통신으로 인한 노드의 에너지를 절감시킬 수 있는 장점을 가진다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.569-572
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• 2009

In this study, HFC ORCs (Organic Rankine Cycles) are investigated for a low-temperature geothermal power generation by a simulation method. A steady-state simulation model is developed to analyze and optimize cycle's performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump are modelled by an isentropic efficiency. Simulations were carried out for the given heat source and sink inlet temperatures, and given flow rate that is based on the typical power plant thermal-capacitance-rate ratio. 3 HFC fluids are considered as a candidate for a working fluid of low-temperature ORCs. In this study, all optimized HFC ORCs are shown to yield almost the same performance in terms of power for a low-temperature heat source of about $100^{\circ}C$.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.103-106
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• 2003

An experimental investigation was peformed to study the characteristics of ER(Electro-Rheological) fluid water flow in a horizontal rectangular tube with or without D.C volatage. To determine some characteristics of the ER flow, 2D PIV(Particle Image Velocimetry) technique is employed for velocity measurement. This research found the mean velocity distribution with 0 kV/mm, 1.0kV/mm and 1.5kV/mm for Re = 0, 0.62, 1.29 and 2.26. When the strength of the electric field increased, the claster of ERF are clearly strong along the test tube and the flow rate decreased.

• Journal of Sensor Science and Technology
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• v.6 no.2
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• pp.131-136
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• 1997

The ISFET(ion sensitive field effect transistor), a semiconductor ion sensor, has many advantages over conventional ion sensors. Various single-sensor type ISFET pH-meters have been developed. However, they could not be applied in fields because their performances are directly affected by the sensor condition. With only one sensor, the system could be easily damaged from environmental factors, and reliability of it is decreased. Therefore, a 4-channel PH-meter system is proposed to improve the reliability of ISFET pH-meter. It has 4 ISFETS as ion sensor, and a software which contains a new calibration and measurement algorithm appropriate to the system. The reliability of the system was proved by measuring hydrogen ion concentration in the pH standard solutions and buffer solutions.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.258-263
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• 2000

River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.84-84
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• 2005

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.22-22
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• 2007

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.41-41
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• 2005

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.982-987
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• 2006

The fluid mechanics and heat transfer of surfactant turbulent pipe flows are characterized with particular emphasis on the effects of surfactant concentration and solution temperature on drag reduction and heat transfer reduction. The test fluids are the surfactant solutions of DR-IW616 supplied by Akzo Nobel Chemical in concentration of $100{\sim}3000ppm$. The solution temperatures studied are $5^{\circ}C$ to $50^{\circ}C$. The critical values of surfactant concentration and solution temperature are clearly identified for drag reduction phenomena.