• 설비공학논문집
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• 제10권5호
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• pp.535-549
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• 1998

A numerical study for performance analysis of a counterflow type forced draft tower and natural draft cooling tower has been performed based on the method using the finite volume method with non-orthogonal body fitted and non-staggered grid system. For solving the coupling problem between water and air, air enthalpy balance, moisture fraction balance, water enthalpy balance, and water mass balance equations are solved with Navier-Stoke’s equations simultaneously. For the effect of turbulence, the standard k-$\varepsilon$ turbulent model is implied in this analysis. The predicted result of the present analysis is compared with the experimental data and the commercial software result to validate the present study, The predicted results show good agreement with the experimental data and the commercial software result. To investigate the influence of the cooling tower design parameters such as approach, range and wet bulb temperature, parametric studies are also peformed.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1201-1212
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• 1999

A numerical analysis is performed to predict the thermal response and ablation rate for charring or non-charring material which is designed to be used as thermal protection system (TPS). The numerical program composed of in-depth energy balance equation and the aerotherm chemical equilibrium (ACE) program. The ACE program calculates various thermochemical state from ablation products. The developed numerical program is verified by comparing the reported results from literature. The sensitivity tests for input parameters are performed. The thermal behavior of ablating material is mainly affected by density of ablating material, convective heat transfer coefficient and recovery enthalpy of flow field.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.305-307
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• 2014

Pyroprocessing (or pyrometallurgy) is the way of extracting from materials subjected to high temperatures. Generally, this process has a high energy consumption because of mass production and heating-up. To attain effective and efficient energy management, energetic analysis using 0-dimensional model is usually conducted. However, this model can lead to a misunderstanding about energy evaluation due to many assumptions and limitations. In this study, heat & mass balance using 0-dimensional model was reviewed to systematize problems and considerations in general process energy evaluation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.82.2-82.2
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• 2011

A channel design which is closely related with the mass transport overpotential is one of the most important procedures to optimize the whole fuel cell performance. In this study, three dimensional results of a numerical study for gas distribution in channels of a molten carbonate fuel cell (MCFC) unit cell for a 1kW class stack was presented. The relationship between the fuel and air distribution in the anode and cathode channels of the unit cell and the electric performance was observed. A charge balance model in the electrodes and the electrolyte coupled with a heat transfer model and a fluid flow model in the porous electrodes and the channels was solved for the mass, momentum, energy, species and charge conservation. The electronic and ionic charge balance in the anode and cathode current feeders, the electrolyte and GDEs were solved for using Ohm's law, while Butler-Volmer charge transfer kinetics described the charge transfer current density. The material transport was described by the diffusion and convection equations and Navier-Stokes equations govern the flow in the open channel. It was assumed that heat is produced by the electrochemical reactions and joule heating due to the electrical currents.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.224-227
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• 2011

공기흡입 엔진 부품의 고온 분출냉각 시험장치에서의 엔탈피값을 구하기 위하여, 시험부 유동에 대한 이론적 계산 및 측정을 수행하였다. 열평형 및 음속유동 방법에 의해 계산된 질량평균 엔탈피 값은 10 MJ/kg 이며, 슬러그형 구리 열량계를 사용하여 측정된 유동 중심에서의 엔탈피 값은 15 MJ/kg이었다. 일반적으로, 유동 중심 대 질량평균 엔탈피 비의 범위는 1.4에서 4이다. 본 시험장치는 고온 분출냉각 시험에 효과적인 낮은 엔탈피 구배를 갖는 것으로 나타났다.

• Journal of Power Electronics
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• 제9권5호
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• pp.700-707
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• 2009

The coal mill used in the coal-fired power plants is modeled in view of the controller design rather than the educational simulator. The coal mass flow and the outlet temperature are modeled by reinvestigating the mass balance and heat balance models physically. The archived data from a plant database are utilized to identify the model parameters. It can be seen that the simulated model outputs are well matched with the measured ones. It is also expected that the proposed model is useful for the controller design.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3918-3929
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• 2021

In this study, we experimentally investigate of a two-phase natural circulation loop that functions as a passive containment cooling system (PCCS). The experimental apparatus comprises two loops: a hot loop, for simulating containment under severe accidents, and a natural circulation loop, for simulating the PCCS. The experiment is conducted by controlling the pressure and inlet temperature of the hot loop in the range of 0.59-0.69 MPa (abs) and 119.6-158.8 ℃, respectively. The heat balance of the hot loop is established and compared with a natural circulation loop to assess the thermal reliability of the experimental apparatus, and an additional system is installed to measure the vapor mass flow rate. Furthermore, the thermal-hydraulic characteristics are considered in terms of a temperature, mass flow rate, heat transfer coefficient (HTC), etc. The flow rate of the natural circulation loop is induced primarily by flashing, and a distortion is observed in the local HTC because of the fully develop as well as subcooled boiling. As a result, we present the amount of heat capacity that the PCCS can passively remove according to the experimental conditions and compared the heat transfer performance using Chen's and Dittus-Boelter correlation.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 춘계학술발표회논문집(2)
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• pp.643-650
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• 1995

A numerical method for treating transient diffusion Involving change of phase is presented. In other methods of dealing with this class of problems, the mass flux balance at the moving phase boundary requires explicit treatment of two distinct phases. The technique, originating from the apparent heat capacity method in transient heat conduction with the phase change, avoids the difficulty by transferring the concentration discontinuity at the boundary to smoothed physical property variations near the moving front. This technique accomodates the nonlinearities which preclude use of analytical solutions. It was tested against known analytical solutions for simple cases and turned out to be quite accurate.

• 한국연소학회지
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• 제16권4호
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• pp.16-22
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• 2011

The present paper discusses thermal design parameters of different sizes of circulating fluidized bed (CFB) boilers with capacities ranging from 2 MWe pilot scale boiler to a 600 MWe utility boiler. Physical boiler size and shape of furnace were identified and dimensional data have been summarized. By performing thermal design for each of the boilers, heat transfer surface area, furnace shape and size, and allocation of heat transfer surface for water-steam side heat absorption have been recalculated, and presented. Although boilers may have significantly different capacity, the facilities have common design parameters, when they are evaluated as basic thermal design processes. The significance of thermal design procedure is explicitly discussed.

• 한국농공학회논문집
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• 제46권7호
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• pp.35-44
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• 2004

In this study, a ventilation model was developed to determine a ventilation rate for the balance of heat, moisture and $CO_{2}$ in a mushroom house. Internal and external temperature, relative humidity and $CO_{2}$ concentration were measured and used to validate the ventilation model. The effects of various environmental factors on physiological responses of mushroom were also investigated. The verified model was simulated under the observed ventilation rates with a difference of$ 0.001{\~}0.065\;m^{3}{\cdot}S^{-1}$ (relative error of $0.3{\~}18.9\%$) when external temperature varied 22.5 to $24.8^{circ}C$ and average ventilation rates was $0.35m^{3}{\cdot}S^{-1}$. The optimal conditions for mushroom growth (internal temperature $22 ^{circ}C$, relative humidity $80\%$, $CO_{2}$ concentration 1,000 ppm) were used for the model application with external temperature, relative humidity and $CO_{2}$ concentration of $27.5{\~}33.5^{circ}C$, $60\%$, and 355 ppm, respectively. Thermal balance was a important factor for an optimum ventilation up to the external temperature of $32^{circ}C$, while $CO_{2}$ concentration balance was more important over $32^{circ}C$. This suggests that humidification for moisture balance is required to maintain temperature and $CO_{2}$ concentration at an optimal level by ventilation in a mushroom house.