• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1475-1482
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• 2006

Wet compression means the injection of water droplets into the compressor of gas turbines. This method decreases the compression work and increases the turbine output by decreasing the compressor exit temperature through the evaporation of water droplets inside the compressor. Researches on wet compression, up to now, have been focused on the thermodynamic analysis of wet compression where the decrease in exit flow temperature and compression work is demonstrated. This paper provides thermodynamic and aerodynamic analysis on wet compression in a centrifugal compressor for a microturbine. The meanline dry compression performance analysis of centrifugal compressor is coupled with the thermodynamic equation of wet compression to get the meanline performance of wet compression. The most influencing parameter in the analysis is the evaporative rate of water droplets. It is found that the impeller exit flow temperature and compression work decreases as the evaporative rate increases. And the exit flow angle decreases as the evaporative rate increases.

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.41-48
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• 2020

The present study discussed the thermodynamic analysis of the hydrogen liquefaction process to build a hydrogen liquefaction pilot plant with a small capacity (0.5 ton/day). A 2-stage Brayton cycle utilizing LNG/LN2 cold energy was suggested to be built in Korea for the hydrogen liquefaction pilot plant with a small capacity. Thermodynamic analysis on the effect of various variables on the efficiency of hydrogen liquefaction process was performed. As a result, the CASE in which the ortho-para conversion catalyst was infiltrated inside the heat exchanger showed the best process efficiency. Finally, thermodynamic analysis was performed on the effect of turbo expander compression ratio on the hydrogen liquefaction process and it was confirmed that an optimal turbo expander compression ratio exists.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.94-102
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• 2001

The thermodynamic second law analysis, which means available energy or exergy analysis, for the indicated performance of Otto cycle engine has been carried out. Each operating process of the engine is simplified and modeled into the thermodynamic cycle. The calculation of the lost work and exergy through each process has been done with the thermodynamic relations and experimental data. The experimental data were measured from the test of single cylinder Otto cycle engine which operated at 2500 rpm, WOT(Wide Open Throttle) and MBT(Minimum advanced spark timing for Best Torque) condition with different fuels: gasoline, methanol and mixture of butane-methanol called M90. Experimental data such as cylinder pressure, air and fuel flow rate, exhaust gas temperature, inlet gas temperature and etc. were used for the analysis. The proposed model and procedure of the analysis are verified through the comparison of the work done in the study with experimental results. The calculated results show that the greatest lost work is generated during combustion process. And the lost work during expansion, exhaust, compression and induction process follows in order.

• 한국주조공학회지
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• 제25권1호
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• pp.36-39
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• 2005

The thermodynamic analysis of deoxidation in molten coppyr by Fe has been made. Equilibrium oxygen solubility saturated with FeO in Cu-Fe-O system has been derived without and with consideration of the solute interaction between Fe and O. The derived relationship of oxygen contents with Fe has been compared with the experimental results done by Kulkarni and the minimum oxygen solubility could be predicted by a simple first order interaction method, Wagner model.

• 한국주조공학회지
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• 제41권5호
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• pp.445-453
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• 2021

다양한 합금계에 대한 계산열역학은 CALPHAD 기법으로 잘 알려져있다. 실험적으로 측정된 열역학 특성들을 활용하여 각 상에 대한 Gibbs 에너지 모델 파라미터들을 구하여, 주로 실험적으로 측정되지 못한 영역에 대한 예측이나 실험 결과에 대한 열역학 해석에 활용되고 있다. 본 연구에서는 내열 주조 합금 (IN-657)이 장시간 사용 후에 일정 영역에서 파괴되는 현상의 열역학적 해석을 위해 Ni-Cr-Nb-C 사원계 시스템의 열역학 모델링을 수행하였고, Cr 함량에 따른 시스템의 안정상, 온도에 따른 상분율 및 Ni₂Cr상의 long range ordering 파라미터를 계산하였고 실험결과와 비교하였다. 계산된 열역학 물성들은 실험으로 보고된 파괴온도 영역 및 해당 영역에서 생성된 안정상에 대한 결과를 잘 설명한다. CALPHAD 기법을 통한 열역학 모델링은 다양한 주조 합금의 열역학적 거동을 해석하고 예측하는데 유용하게 사용될 수 있을 것으로 기대된다.

• Coupled systems mechanics
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• 제4권3호
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• pp.237-249
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• 2015

In the gear meshing process, gear temperature field concerns the meshing surface friction, the friction heat depends on the contact pressure, the contact pressure is affected by the elastic deformation of gears and the temperature field caused by the thermal deformation, so the temperature field, stress field and displacement field should be mutual coupling. It is necessary to consider in meshing gear pair in the operation process of thermodynamic coupling contact stress (TCCS) and thermodynamic coupling deformation (TCD), and based on thermodynamic coupling analysis (TCA) of gear teeth deformation.

• 한국표면공학회지
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• 제45권3호
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• pp.136-141
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• 2012

'Jikjisimcheyocheal (Jikji afterwards)' is known as a first book printed by the metal type in the world. The metal type used for printing this book has not been found yet. To help for replicating the original metal type, it is required to investigate the composition analysis of the copied metal type. In this study, the composition analysis and thermodynamic care for replicating of ancient metal type was performed on the basis of an analytical reports concerned with the ancient metal type which made after Jikji printing. Metal types were made by remelting and casting of the mother alloy which came from a cast of a mixed metals in accordance with the composition revealed in the literatures. Change of composition during remelting of mother alloy and casting of metal was detected by the EDS analysis. The reasons for variation in composition were discussed by metallurgical and thermodynamic point of view, and a mixing ratio of metals to get the original composition of ancient metal type is suggested. Some attention should be paid on mixing, melting and casting of metals to get an objected composition for copy of ancient metal type.

• Journal of Advanced Marine Engineering and Technology
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• 제40권6호
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• pp.476-483
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• 2016

해양온도차발전용 유기랭킨사이클은 해양의 표층수와 심층수사이의 온도차를 이용하여 발전하는 사이클이다. 작동유체는 유기랭킨사이클의 열역학적 성능에 있어 중요한 요소이다. 유기랭킨사이클의 열역학적 분석방법으로 핀치포인트분석이 있다. 본 연구는 열교환기내 핀치포인트온도차의 변화와 열원 및 열침의 출구온도의 변화에 따른 열역학적 성능분석을 수행하였다. 핀치포인트분석법에 따라 설계한 해양온도차발전용 단순랭킨사이클에 7종의 단일 작동유체를 적용하여 열역학적 성능을 분석하였다. 성능분석결과 열교환기에서 핀치포인트온도차와 열원 및 열침의 온도변화가 작을수록 사이클 총 비가역성 및 총 엑서지 파괴인자가 감소하였으며, 제2법칙 효율은 상승하였다. 또한 비가역성은 열역학적 변화가 발생한 곳에서 크게 변화하였다. RE245fa2는 선정한 작동유체 중에서 가장 우수한 열역학적 성능을 보여주었으며, 모든 작동유체의 성능은 유사하였다. 열교환기 및 작동유체 선정에 있어 열역학적 성능과 함께 다양한 요소들에 대해서도 엄밀한 이론적 근거가 필요하다.

• 설비공학논문집
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• 제1권3호
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• pp.219-227
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• 1989

Performance analysis of an absorption heat pump system for solar energy recovery has been done by computer simulation to find improved working pairs. Based on the thermodynamic analysis, the coefficient of performance and mass flow ratio have been calculated to compare two aqueous solutions [LiCl-water, $LiCi-CaCl_2-Zn(NO_3)_2$-water] which were developed for cooling by others, with the conventional LiBr-water solution. As a result of this analysis, the performances of the new aqueous solutions were found to be better than that of LiBr-water solution not only in cooling systems, but also in heating and in heat transformer systems. Their theoretical thermodynamic performance data were given here with.

• Bulletin of the Korean Chemical Society
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• 제22권7호
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• pp.663-668
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• 2001

Thermodynamic and electrical functions of aminophenol and anthranilic acid complexes with Mn(Ⅱ), Fe(Ⅱ), Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) were determined. ΔG°, ΔH° and ΔS° were calculated with the help of stability constant values at different temperatures. It was found that the complexing processes have an exothermic nature. The studied complexes behave like semiconductors. The conduction takes place according to hopping mechanism. To show the composition of complexes conductometric and photometric titrations, IR spectra, thermal analysis and X-ray diffraction techniques were employed.