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Combined cycle power (CCP) plant using LNG plays key role in electric supply including nuclear and coal power generation systems. Power reduction of gas turbine during summer can be recovered if gas turbine intake cooling system can be implemented in existing LNG based CCP plants. Furthermore, steam injection, turbine cooling air precooling and turbine case cooling technologies can be considered for enhancing power and efficiency of CCP plants. Such approaches are being widely studied in global gas turbine society. The present study aims to investigate net benefit of implementing those technologies for enhancing power and efficiency of an existing LNG based CCP. For performance comparison, (1) gas turbine intake cooling system, (2) steam injection, and (3) turbine cooling air precooling technologies are implemented to Busan LNG CCP plant
객체지향 패러다임을 적용한 시스템으로 재개발한다면 재사용을 통한 소프트웨어 생산성 향상을 이룰 수 있고, 유지보수 비용을 절감할 수 있게 된다. 절차중심의 시스템을 객체지향 패러다임을 적용한 형태로 변환시킬 때 특히 코드에서 자동 혹은 반자동으로 객체를 추출하고자 하는 기법들이 많이 연구되고 있다. 그러나 이들 방법에서는 개념적인 객체의 추출이 용이하지 않다. 따라서 추출되는 객체의 개념적 무결성이 떨어지는 문제가 발생한다. 본 논문에서는 절차중심으로 개발된 프로그램을 객체지향 시스템으로 바꾸려고 할 때 발생되는 문제점중의 하나인 객체추출 방법 및 틀에 대해 논한다. 원시 코드 및 설계 복구 정보를 입력받은 후 먼저 실세계의 응용영역에 대한 객체 모델링을 이용하여 객체를 추출한다. 그리고 코드의 기능, 코드의 전역변수 및 인터페이스를 분석하여 객체를 추출하므로써 객체의 개념적 무결성을 높이며, 클래스 계층구조의 구축을 용이하게 한다. If there is redeveloping into the system applying the object-oriented paradigm, productivity improvement of software through reuse would be accomplished and maintenance cost be reduced. When a procedure-oriented system is transformed to a type applying the object-oriented paradigm, various techniques are studied to extract objects from source code automatically or semi-automatically. However, it is not easy to extract conceptual objects when those techniques are applied. This problem entails another problem which drops the conceptual integrity of the extracted objects. In this paper, we suggest an object extraction method and tool development to resolve the problem occurring at the time when the programs developed through procedure-oriented is transformed to an object-oriented system. The suggested method allow to extract the desired objects using object modeling for various application domains of the real world given source code and design recovery information. During the extraction process, functionality and global variables of the source code as well as its interface are rigorously analyzed. This process can enhance the conceptual integrity of the objects and make easy to construct class hierarchies.
We investigate two-dimensional laminar flow around rectangular cylinders placed in a uniform stream. Numerical simulations are performed, using finite volume method, in the ranges of 50≤Re≤150 and 0.1≤W/H≤1.0, where Re and W/H are the Reynolds number and the width-to-height ratio, respectively. The immersed boundary method is used to handle the rectangular cylinder in a rectangular grid system. Comparisons with the previous results show good agreement in Strouhal number, drag and lift coefficient. The present study reports the detailed information of flow structure at different width-to-height ratios in the ranges of 50≤Re≤150.
Heat transfer and pressure drop inside radially splitted duct is important factor which to decide the efficiency of machine. Promoting heat transfer in radial direction requires a design approach to distribute cooling or heating flow from a source evenly with minimum pressure loss. If the difference between inner and outer diameter of radial system is larger, the whole radial passage should be splitted into several smaller ducts for controlling flow distribution and velocity. In the present study, a radial cooling ducts are modeled at its real scale to investigate flow and heat transfer characteristics experimentally and analytically. The cooling duct system has total twelve radial ducts with mixture of straight and splitted ducts. For the investigation, cooling flow direction varied from radially inward and outward, and it operates in the ranges of Re=14000~28000. Also, to investigate influence of cross flow, inward flow with cross flow was researched. The experiments employs transient heat transfer tests using two narrow band thermochromic liquid crystals. Heat transfer and flow distribution are calculated numerically using finite volume method based on same condition to validate modeling approach against measured data. The results shows good agreements between the tests and prediction. The detailed observation of flow characteristics provides design guides for such a radial cooling duct system.
In this paper, EP-Kalina cycle applying liquid-vapor ejector and motive pump is newly proposed. In this EP-Kalina cycle, the liquid-vapor ejector is used to increase pressure difference between inlet and outlet of the turbine. Also the motive pump enhances the performance of liquid-vapor ejector, resulting in increase of system efficiency of OTEC cycles. The comparison cycles in this study are basic, Kalina, EKalina and EP-Kalina ones. The pump work, net power, APRe, APRc, TPP and system efficiency of each cycle are compared. In case of net power, EP-Kalina cycle is lowest among the cycles due to the application of the motive pump. But, the net power difference of cycles seems to be minor since the pump work of cycles is merely about 1㎾, compared to turbine gross power of 20㎾. The system efficiency of EP-Kalina cycle shows 3.22%, relatively 44% higher than that of basic OTEC cycle. Therefore, the system efficiency is increased by applying the liquid-vapor ejector and the motive pump. Additional performance analysis is necessary to optimize the proposed EP-Kalina cycle.