• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.97-109
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• 2022

Multi-dimensional coupling analysis is a research hot spot in nuclear reactor thermal hydraulic study and both the full-scale system transient response and local key three-dimensional thermal hydraulic phenomenon could be obtained simultaneously, which can achieve the balance between efficiency and accuracy in the numerical simulation of nuclear reactor. A one-dimensional to three-dimensional (1D-3D) coupling platform for the nuclear reactor multi-dimensional analysis is developed by XJTU-NuTheL (Nuclear Thermal-hydraulic Laboratory at Xi'an Jiaotong University) based on the CFD code Fluent and system code RELAP5 through the Dynamic Link Library (DLL) technology and Fluent user-defined functions (UDF). In this paper, the International Standard Problem (ISP) No. 43 is selected as the benchmark and the rapid boron dilution transient in the nuclear reactor is studied with the coupling code. The code validation is conducted first and the numerical simulation results show good agreement with the experimental data. The three-dimensional flow and temperature fields in the downcomer are analyzed in detail during the transient scenarios. The strong reverse flow is observed beneath the inlet cold leg, causing the de-borated water slug to mainly diffuse in the circumferential direction. The deviations between the experimental data and the transients predicted by the coupling code are also discussed.

• Solar Energy
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• v.10 no.3
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• pp.27-34
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• 1990

The main objective of this study was to find the relationship between transpiration rate and environmental factors for crops in hydroponic culture within plastic greenhouse by using the computer model developed from the heat balance around leaves of a crop. A computer model was developed and verified through comparison with the experimental results for lettuce in hydroponic culture in a polyethylene film house. The model may be extensively used for the water management and thermal environment study of crops in protected culture, if the supplemented studies for some crops would be accomplished.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2015-2020
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• 2007

Diesel is an excellent candidate fuel for fuel cell applications due to its high hydrogen density and well-established infrastructure. But, it is hard to guarantee desirable performance of diesel reformer because diesel reforming has several problems such as sulfur poisoning of catalyst and carbon deposition. We have been focusing on diesel autothermal reforming(ATR) for substantial period. It is reported that ATR of diesel has several technical advantages such as relatively high efficiency and fuel conversion compared to steam reforming(SR) and partial oxidation(POX). In this paper, we investigate characteristics of diesel reforming under various ratios of reactants(oxygen to carbon ratio, steam to carbon ratio) for improvement of reforming performances(high reforming efficiency, high fuel conversion, low carbon deposition). We also exhibit calculated heat balance of autothermal reformer at each condition to help thermal management of SOFC system.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2194-2199
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• 2007

An experimental study is performed to investigate the thermal and flow characteristics of subcooled liquid nitrogen in a natural circulation loop. Experimental apparatus is designed and constructed such that a closed loop is cooled at the top by a cryocooler and heated nearly at the bottom by cartridge heaters. Steady state is obtained by controlling the heating power to the cartridge heaters and a thin-film heater to reduce the cooling power of the cryocooler. Temperature is measured at several locations of the loop and the mass flow rate through the loop is estimated from the energy balance in terms of the measured temperatures. Experiment is repeated for various values of the vertical height between the cooling and heating parts. The results show that the heat transfer capability of the loop has a maximum at a certain value of height. The optimal height to maximize the heat transfer is in a good agreement with analytical prediction to take into account the buoyancy and viscous forces in the loop.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.5 no.4
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• pp.35-42
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• 1991

Recently, HID lamps have been considered as important in regard to the trend of energy saving, and increasingly and diversely used in various ways. This paper will show the simulating models concerning high-pressure arc discharge system directly applicable for its design and manufacture, and analyze its various characteristics. For warm-up characteristics, the evaporating process of inner atoms is described in terms of second-order differential equation: for the thermal conduction from are axis to discharge wall and outer bulb, its transfer process is introduced according to five first-order differential equations. Under the steady state satisfying LTE, the time-variant characteristics are suggested by means of time-dependent energy balance equation derived from fluid equations, approximation of radiation energy and material functions in the discharge tube. The simulating models concerning these equations are then applied for high-pressure mercury lamp.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.333-335
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• 2014

As the user demand for power plants becomes various, design objective becomes complicated. To review the system feasibility, system objective and evaluation criteria need to be newly defined. In this study, engineering design procedure of the multi-purpose power plant, such as barge-mounted combined cycle power plant with $CO_2$ capture, was shown as a previous work for the feasibility review of the system alternatives. For the system design, heat and mass balance for each system configuration was firstly performed. Using the thermal analysis results, conceptual design of system alternatives was carried out. And then, preliminary design of the major equipment was done. The engineering calculation results of this study would be used as the evaluation data for system feasibility review.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.27-32
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• 2001

A study has been made of the condition to maintaining Taylor-Proudman column flows in a compressible rotating fluid, which is driven by small mechanical and/or thermal perturbations imposing on the container wall in the basic state of isothermal rigid body rotation. The Rossby and system Ekman numbers are assumed to be very small. The Taylor-Proudman column flow can be produced when energy parameter, e, becomes constant on the whole flow region. Energy balance concept, related to energy parameter, and its physical interpretation are given with comprehensive discussions.

• Journal of Environmental Science International
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• v.8 no.2
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• pp.151-154
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• 1999

To verify the accuracy of the numerical experiment of Part I, measurements at the matured rice canopy located around Junam reservoir were performed at August 14, 1995. According to the measured data, the foliage temperature recorded the highest value, and the ground temperature was the lowest around noon, and these results coincided with those of the numerical experiment using the combined model of Part I. From the estimation using measured data, the maximum value of the latent heat flux was 380$Wm^2$, the highest value among energy balance terms, and the energy redistribution ratio of the latent heat flux was averaged as 0.5, the highest values among redistribution ratios. These results are the same as those of the numerical experiment in tendency, but they reveals a little lower in the absolute values than those from the numerical experiment.

• New & Renewable Energy
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• v.2 no.2 s.6
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• pp.50-59
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• 2006

An experimental and numerical study is carried out to investigate the performance and the efficiency humidifying Membrane Electrolyte Assembly and having the double-layered catalyst in a fuel cell system which is taken into account the physical and thermal concept. Based on the principals of the problem, the equation of electronic charge conservation equation, gas-phase continuity equation, and mass balance equation are used for the numerical calculation. A unit cell for $200cm^2$ MEA is assembled and measured for finding better operational situation. After finding the optimal condition, 10 cell stacked PEMFC is fabricated. For the performance evaluation, V-I and power curves are examined in detail by changing the condition of humidity, temperature, pressure, thickness of catalyst and oxidant. It is found that the power is maximized around 500W at 80A.

• Tribology and Lubricants
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• v.14 no.3
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• pp.39-45
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• 1998

Reynolds equation, which describes behavior of fluid film in journal bearings, basically satisfies mass conservation. But, boundary conditions usually used with this equation, e.g. half Sommerfeld or Reynolds boundary conditions, cannot fulfill this natural law of conservation. In the case of connecting rod bearing, where applied load is dynamic and its magnitude is relatively large, such unrealistic boundary conditions have serious influence on calculation results, especially on lubricant flow rate or power disspation which are important parameters in thermal analysis. In this paper, mass-conserving boundary condition was applied in the finite element analysis of connecting rod bearings. Lubricant flow rate and power dissipation rate were calculated together with journal center locus, minimum film thickness and maxmium film pressure. These computation results were compared with those of the case of Reynolds boundary condition. Balance between inlet and outlet flow rate was well achieved in the case of mass-conserving boundary condition.