• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.116-121
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• 2014

In order to study the improvement of the multi stage regeneration cycles, muti-stage processes were applied to the cycles, respectively or together. The kinds of the cycles are multi stage reheater cycle (MS) and multi stage reheater regeneration cycle (MSR). Working fluid used was R134a and R245fa. Temperature of the heat source was $65^{\circ}C$, $75^{\circ}C$, and $85^{\circ}C$, and temperature of the heat sink was $5^{\circ}C$. Optimization simulation was conducted for improving the gross power and efficiency with multi stage reheater regeneration cycle for ocean thermal energy conversion(OTEC) with changing of a heat source, kind of the working fluid, and type of the cycle. Performance analysis of the various components was simulated by using the Aspen HYSYS for analysis of the thermodynamic cycle. R245fa shows better performance than R134a. This paper showed the most suitable working fluid with changing of a heat source and the kinds of working cycle. Compared to each other, MS showed better performance at gross power and MSR showed higher cycle efficiency.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.18-18
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• 2000

산업용 가스터빈에서 대기로 방출되는 배기열을 효과적으로 이용하기 위한 역 브레이튼 사이클 가스터빈(Reverse Brayton Cycle Gas Turbine) 엔진의 출력과 비연료 소비율 및 열효율을 기본 브레이튼 사이클 엔진, 재열사이클에 역 브레이튼 사이클을 추가한 엔진, 역 브레이튼 사이클에 중간냉각기를 추가한 엔진의 출력, 비연료 소비율 및 열효율을 비교하였다.(중략)

• The KSFM Journal of Fluid Machinery
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• v.9 no.6 s.39
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• pp.35-44
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• 2006

Operation conditions of a reheat cycle gas turbine for a combined cycle power plant was analyzed. Based on measured performance parameters of the gas turbine, a performance analysis program predicted component characteristic parameters such as compressor air flow, compressor efficiency, efficiencies of both the high and low pressure turbines, and coolant flows. The predicted air flow and its variation with the inlet guide vane setting were sufficiently accurate. The compressor running characteristic in terms of the relations between air flow, pressure ratio and efficiency was presented. The variations of the efficiencies of both the high and low pressure turbines were also presented. Almost constant flow functions of both turbines were predicted. The current methodology and obtained data can be utilized for performance diagnosis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.472-479
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• 2006

Recently, various methods have been developed to improve the performance of gas turbines for combined cycle power plants. This paper especially focused on the gas turbine with a reheat process. The purpose of this study is to analyze performance characteristics of a reheat-cycle gas turbine on both a design point and off-design operations. Results of the parametric study of this model show how operating and design parameters influence on the performance of the gas turbine. Moreover, possibilities for the analysis of off-design performance based on a self-generated compressor performance characteristic map are presented.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.89-102
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• 1995

The evaluation of reheat cracking susceptibility in CrMoV turbine rotor steel was performed using thermally simulated heat affected zones. The examinations were carried out in terms of microstructural characterization, microhardness measurement and a Charpy type notch opening three point bend test. It was found that reheat cracking susceptibility increased as the peak temperature increased. This effect was due to the combined effects of the carbide dissolution and unrestricted grain growth at 1350.deg. C peak temperature. Reheat cracking susceptibility was estimated based on microhardness measurement and prior austenite grain size. It was established that for this particular material, reheat cracking in coarse grained heat affected zone can be eliminated if the microhardness is below about 360DPH and the grain size is below about 30.mu.m. It is evident that reheat cracking susceptibility can be eliminated or reduced by carefully controlling the welding parameters such that a refined structure is produced in the coarse grained heat affected zone.

• Journal of the KSME
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• v.30 no.2
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• pp.107-114
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• 1990

(1) Cr-Mo-V 합금강 로우터재료는 사용도중 템퍼 취화된다. 템퍼취화된 소재는 취성제거처리 혹 은 재열처리를 하여 취성을 감소시킬 수 있다. (2) 축의 신뢰도를 파괴역학 원리를 적용하여 계산하였으며 템퍼 취화된 소재는 파손 위험성이 있으나 열처리 된 소재는 취성파괴 및 고 사이클 하중에 의한 피로균열 성장에 대해서 안전성 이 충분하다는 결론을 얻을 수 있다. (3) 샬피 V-노치 충격치 (CVN)와 파괴인성치(K$_{tc}$ )의 관계식을 취성재료에도 적용할 수 있 는가의 여부에 대해서는 많은 조사가 필요하다. (4) 취성소재의 피로균열 개시값$\Delta$ $K_{th}$을 알고 있으면 취송소재로 제조된 구조물의 파괴역학적인 해석을 하는데 도움을 줄 수 있다.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.11-17
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• 2016

In this study, the simulation for performance comparison between basic single stage organic rankine cycle, multi stage reheater cycle and multi stage reheater & recuperator cycle was carried out. The multi stage reheater cycle and multi stage reheater & recuperator cycle was designed to improve the efficiency for organic rankine cycle using heat source from industrial waste heat and heat sink from deep ocean water. R245fa was selected as a refrigerant for the cycle and system efficiencies were simulated by the variation of the heat sink temperature and the cycle classification. Performance characteristics were simulated by using the Aspen HYSYS. It was confirmed that the system efficiency was decreased by the increase of heat sink temperature. These results can be considered to be applied as geo-ocean thermal energy conversion in where plenty of geothermal or ocean thermal resource exist.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.35-43
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• 2010

In this study, an ideal water-recirculated oxy-fuel power generation system is proposed. The results of parametric studies of the performance characteristics of the system are discussed. For a given choice of the turbine inlet temperature, the turbine, which produces power, can be either a gas or a steam turbine. For maximum efficiency, the turbine inlet temperature is selected as the level of state-of-the-art gas turbines and the reheat cycle may be adopted not only to enhance the turbine power but also to maintain dryness of the water with a turbine exhaust temperature that is as high as possible. To obtain a low condensation temperature for a high purity of $CO_2$, a relatively low pressure expansion process may be added. Finally, the performance of the water-recirculated oxy-fuel power generation system is discussed with reference to various operating parameters and system configurations. The optimal operating conditions for high performance and a high purity of $CO_2$ are proposed.

• Food Science and Preservation
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• v.11 no.2
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• pp.250-256
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• 2004

The objectives of this study were to develop a new commercial grain cooler suited to domestic weather and post-harvesting conditions for paddy, and to evaluate the performance. A prototype grain cooler capable of cooling paddy of 200 tons within 24 hours was developed. The grain cooler was designed to control the refrigeration capacity from 0 to 100% by controlling the capacity of compressor with unloading solenoid valve and by changing the flow rates of hot refrigerant gas flowing into reheater and evaporator from compressor. And a controller with one chip microprocessor was developed to control temperature and relative humidity of cooling air. The maximum cooling capacity of the grain cooler was 35,284㎉/hr at condensing/evaporating pressure of 16.5/3.6 kgf/$\textrm{cm}^2$. Maximum flow rate of cooling air was 120 ㎥/min at static pressure of 279 mmAq. The total maximum required power was 22.8㎾, and total required energy was saved from 26.7 to 33.3% of maximum power depending on operating conditions. The coefficient of performance of refrigeration devices and total coefficient of performance of the grain cooler were 4.71 and 1.8, respectively.