• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2173-2187
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• 2022

A 3D thermo-elasto-hydrodynamic model is developed to analyze the sealing performance of a notched mechanical seal applied in the reactor coolant pump. In the model, the generalized Reynolds equation, the energy equation coupled with notch heat balance equation, the heat conduction equations, and the deformation equations of the sealing rings are iteratively solved by the finite element method. The film pressure and temperature distribution are obtained, and the deformation of the sealing rings is revealed to study the mechanism of the notched mechanical seals. A parameterized study is conducted to analyze the sealing performance under different operating conditions. As a comparison, the sealing performance of non-notched seals is also studied. The results show that the hydrostatic effect is dominant in the load-carrying capacity of the fluid film due to the radial mechanical and thermal deformations. The notch can cool the fluid film and influence the thermal deformation of seal rings. The sealing performance is sensitive to the pressure difference, ambient temperature, and rotational speed. It is suggested to set the notches on the softer sealing rings to acquire the greater hydrodynamic effect. Compared with the non-notched, the notched end face holds a better lubrication performance, especially under lower rotational speed.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.84.2-84.2
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• 2010

발전용 연료전지시스템은 지구 온난화의 주요 원인인 $CO_2$의 발생을 기존 발전시스템에 비해 현저히 줄일 수 있는 친환경, 고효율 발전시스템으로서 분산형 발전이 가능한 혁신적인 발전시스템이다. 또한 전기 생산과 동시에 열을 발생시켜 소형열병합 발전을 함으로써 에너지효율을 극대화 할 수 있다. 본 논문에서는 2.4MW급 발전용 연료전지시스템 프로세스 모델링을 통해 얻은 결과 값인 Heat and Material Balance 데이터와 실제운전중인 데이터를 비교, 분석하여 운전시간, 온도, 고도 및 운전조건에 따른 출력특성을 파악함으로써 향후 프로세스 설계 시 정확도를 높일 수 있을 것이다.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.409-413
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• 2016

The 500 MW rated steam turbine model in coal fired power plant is developed to be used for validation and verification of controller rather than for the education of operator. The valve, steam turbine, reheater and generator are modeled and integrated into the simulator. And the data from the plant heat balance diagram are used for estimation of the model parameters together with actual operating data. It is found that the outputs of model such as pressure, temperature and speed are similar to the operating ones. So, it is expected that the developed model will play a very big role in controller development.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.37-40
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• 1996

Cable-In-Conduit Conductor(CICC) is widely accepted as an advanced superconductor configuration for large scale applications such as tokamak fusion reactors, MAGLEV (MAGnetic LEVitation), and SMES (Superconducting Magnetic Energy Storage). The stability of CICC cooled with supercritical helium can be very high if it is operated below a certain limiting current. This limiting current can be determined by Stekly type heat balance equation. The stability characteristic of CICC for AC operation is more complicated than that of DC because there are additional instability sources which are associated with local flux change. Ramp-rate limitation is a phenomenon discovered during US-DPC (United States-Demonstration Poloidal Coil) program, which showed apparent quench current degradation associated with high dB/dt. This paper describes recent experimental investigation results on the ramp-rate limitation and discusses current imbalance, induced current, current redistribution due to local quench of the strand in the cable.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.274-277
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• 2009

본 논문에서는 소형 PEM(Proton Exchange Membrane) 연료전지 스택의 BOS(Balance of Stack) 제어에 관하여 논의한다. 별도의 가습 장치가 필요치 않고 BOS의 구성이 비교적 간단한 소형 PEM 연료전지 시스템에서는 팬과 퍼지밸브만의 제어를 통해 스택 내부 수분의 조절과 열 관리가 수행된다. 따라서 본 논문에서는 부하에 따른 최적의 공기유량을 계산하고 요구되는 유량의 공급을 위해 팬을 제어하는 알고리즘을 통해 소형 연료전지 시스템의 과도응답 특성과 안정성을 향상시키는 방법에 관하여 제안한다. 150W급 소형 연료전지 시스템을 꾸미고, 마이크로컨트롤러를 이용한 제어회로를 구현하여 실험함으로써 제안된 알고리즘의 유용함을 검증하였다.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.155-163
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• 1999

A numerical study for simulating a swirling pulverized coal combustion in axisymmetric geometry is done here by applying the weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard ${\kappa}-{\varepsilon}$ turbulence model, whereas the Lagrangian approach is used for the particulate phase for soot. The eddydissipation model is employed for the reaction rate for gaseous mixture, and the single-step first-order reaction model for the devolatilization process for coal. By comparing the numerical results with experimental ones, the models used here are confirmed and found to be one of good alternatives for simulating the combustion as well as radiative characteristics.

• Journal of the Korean Society of Combustion
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• v.17 no.1
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• pp.1-11
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• 2012

A slag building simplified model was developed to determine wall heat flux of a Shell 300 MW coal gasifier. In the model 4 layers(particulate, sintered, molten slag, solidified slag) were considered and mass conservation and energy balance were used to obtain each slag layer's thickness and surface temperature. Thermo-chemical and fluid charateristics of the gasifier were studied with and without considering the slag model using commercial CFD code FLUENT. Consideration of the slag layer did not affect syn-gas mole fractions. However, the slag layer caused to increase the exit gas temperature by about 50 K.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.49-51
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• 2012

In this paper, the integration issue, such as an air-side integration design between the gas turbine and air separation unit, is described and analyzed by the exergy and energy balance of the combined-cycle power block in an IGCC power plant. The results showed that the net power of the system was almost same, but that of the gas turbine was decreased as the integration degree increased. The highest exergy loss was occurred in the combustor of gas turbine, which was affected by the chemical reaction, heat conduction, mass diffusion, and viscous dissipation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.4
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• pp.304-314
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• 2002

Performance analysis of the automotive air-conditioning system is conducted by using computer simulation, and performance tests are carried out by using the climate wind tunnel in order to verify simulation. Evaporator and condenser were modeled by using empirical correlation which was obtained from calorimeter data, and compressor was modeled by using map based method. The steady state thermodynamic conditions of refrigerant satisfying mass and energy balance were assumed in the simulation program for automotive airconditioning system. The system performance was analyzed by finite difference method until differential air enthalpy between evaporator inlet and outlet becomes converged. Simulation results are in good agreement with experimental results at most operating conditions. Variation of discharge temperature and pressure of compressor, outlet temperature of evaporator, cooling capacity, and COP were investigated in term of air volume flow rate for evaporator, compressor capacity, compressor speed, superheat of thermostatic expansion valve, and diameter of suction line.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.321-327
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• 2000

This study represents numerical analysis in top opening rectangular with a heating source. The governing equations were solved by a finite volume method, a SIMPLE algorithm was adopted to solve a pressure term. The top boundary with free surface was calculated by energy balance condition. As the results of simulations, the magnitudes of the velocity vectors and isotherms were very small at the lower space of a heating source. The mean Nusselt numbers are increased proportionally to the Grashof number, the heat transfer at Y/H=0.25 was greater than other positions.