• Journal of Energy Engineering
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• v.2 no.1
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• pp.83-94
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• 1993

In this paper, the performance of an energy conversion system is analyzed using two efficiency concepts, one of conventional and the other of energetic efficiently. The objective of this analysis was to improve and optimize the energy conversion system in point, namely, and LNG-fired Combined Heat and Power Plant (CHP). To this end, energies which represent the true efficiency figures were evaluated for various flows of the system with a set of system configurations given. Then the economic values of the energies were assigned to respective flows and subsystems. With these economic data locations of inefficiencies and opportunities for improvement are identified.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.45-54
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• 2009

An exergy analysis is carried out for the regenerative steam-injection gas turbine systems which has a potential of enhanced thermal efficiency and specific power. Using the analysis model in the view of the second law of thermodynamics, the effects of pressure ratio, steam injection ratio, ambient temperature and turbine inlet temperature are investigated on the performance of the system such as exergetic efficiency, heat recovery ratio of heat exchangers, exergy destruction, loss ratios, and on the optimal conditions for maximum exergy efficiency. The results of computation show that the regenerative steam-injection gas turbine system can make a notable enhancement of exergy efficiency and reduce irreversibilities of the system.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.93-100
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• 2009

An exergy analysis is carried out for the regenerative wet-compression Brayton cycle which has a potential of enhanced thermal efficiency owing to the reduced compression power consumption and the recuperation of exhaust energy. Using the analysis model, the effects of pressure ratio and water injection ratio are investigated on the exergy efficiency of system, exergy destruction ratio for each component of the system, and exergy loss ratio due to exhaust gas. The results of computation for the typical cases show that the regenerative wet-compression gas turbine cycle can make a notable enhancement of exergy efficiency. The injection of water results in a decrease of exergy loss of exhaust gas and an increase of net power output.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1036-1042
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• 2012

This paper describes an analysis on exergy efficiency of R744 OTEC power system to optimize the design for the operating parameters of this system. The operating parameters considered in this study include subcooling and superheating degree, evaporation and condensation temperature, and turbine and pump efficiency, respectively. The main results are summarized as follows : As the evaporation temperature, superheating degree, and turbine and pump efficiency of R744 OTEC power system increases, the exergy efficiency of this system increases, respectively. But condensation temperature and subcooling degree of R744 OTEC power system increases, the exergy efficiency of this system decreases, respectively. The effect of evaporation temperature and pump efficiency on R744 OTEC power system is the largest and the lowest among operation parameters, respectively. Therefore, the refrigerant temperature in the evaporator must be closely to the surface seawater temperature to enhance the exergy efficiency of R744 OTEC power system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1200-1210
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• 1990

Conventional efficiencies of the adiabatic compression process such as isentropic efficiency and polytropic efficiency can be explained as exergetic efficiencies replacing the reference atmospheric temperature with the temperature which can be determined in the process itself. So that, other efficies such as maximum isentropic efficiency can be defined by giving proper reference temperatures. By applying the same logical principles, exergetic and other rational efficiencies for the non-adiabatic compression process are also defined and discussed for their physical meanings and reasonable engineering applications.

• The Magazine for Energy Service Companies
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• s.62
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• pp.44-47
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• 2010

엑서지 진단기법을 개발해 그 수준을 한 차원 높이면서 새로운 에너지진단의 지평을 열고 있는 (주)엑서지엔지니어링. 우수한 에너지관리 및 환경문제에 대한 끊임없는 연구, 기술 전문 인력 확보, 고효율 에너지절약기기로 교체사업을 주도하는 등 분주하게 경영성과를 올리고 있는 엑서지엔지니어링 박명호 대표를 만나 ESCO 사업에 대한 기술력과 노하우를 들어보았다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.593-600
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• 2012

The exergy characteristics for R245fa and water working fluids have been analyzed for an electric generation system utilizing the Rankine cycle to recover heat from the wasted exhaust gas from a diesel engine used for the propulsion of a large ship. The theoretical calculation results showed that the efficiencies of exergy and system exergy improved as the turbine inlet pressure increased for R245fa at a fixed mass flow rate. Furthermore, the exergy destruction rates of the condenser and evaporator were relatively larger than those in other components. The exergy efficiency of the system increased with increasing mass flow rate. For a water working fluid, although the exergy destruction rate of the evaporator was similar to that for R245fa, the exergy loss rate varied significantly in response to variations in the pressure and mass flow rates at the turbine inlet.

• Journal of Energy Engineering
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• v.12 no.3
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• pp.165-176
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• 2003

In this study, the exergy analysis is conducted on the well known performance of already developed system and then compared with the efficiency of each equipment to propose optimum operation of the system. The system used in this study is 500 MW coal firing power plant. The efficiency of the boiler is 67% and the condenser is 99% by exergy analysis. The exergy consumption of the boiler was 32.95% at 100% load. The exergy consumption of the high pressure turbine and the low pressure turbine is 8.31% and 8.12%, respectively. Together with the concrete study on the object of performance revision of the low efficient development system proved in this study, if detailed exergy analysis on the operation condition of the equipments of the development system presently being operated is continued, then it is expected to help minimize the exergy consumption of relatively low efficient parts that are worn-out or miss-installed.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.684-687
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• 2010

본 논문은 복합사이클 발전플랜트의 폐열회수 보일러 최적운전 및 최적설계에 대한 새로운 접근 방법을 도출하기 위해 폐열회수 보일러에서 발생되는 증기로 증기터빈을 구동하는 하부사이클 효율을 검토하였다. 열역학 제1법칙 해석을 통해 하부사이클 에너지 평형을 검토하였고, 열역학 제2법칙을 통해 엑서지 평형을 검토하였다. 하부사이클 효율이 최대가 되는 폐열회수 보일러를 설계하기 위해서는 열역학 제1법칙을 해석할 경우 하부사이클 전체를 해석하여야 함을 알 수 있다. 하지만, 열역학 제2법칙을 통한 엑서지 해석을 행할 경우 하부사이클 효율이 최대가 되는 증발온도와 폐여회수 보일러에서 소모되는 엑서지가 최소가 되는 점이 일치함을 알 수 있었다. 따라서 본 논문을 통해 폐열회수 보일러에서 소모되는 엑서지 해석을 통해 하부사이클 효율이 최대가 되는 폐열회수 보일러 최적화가 가능함을 알 수 있다.

• Plant Journal
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• v.9 no.3
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• pp.43-47
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• 2013

Even if an expert who has majored energy engineering, it is a difficult concept to understand power output optimization and power efficiency optimization. In this study a diagram applying thermodynamic state value as specific exergy and exergy ratio was developed. Although general peoples who did not major energy engineering can be easily understand the concept of power output optimization and power efficiency through the developed diagram. A represented property that can identify the performance of power plant is the main steam temperature and pressure. At the developed diagram the maximum power output line and maximum power efficiency line are shown according to the temperature and pressure of main steam. Therefore we can identify how much a power plant approach to maximum power output and maximum power efficiency.