• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.251-258
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• 1990

Optimal design of heat exchanger for closed CO$_{2}$ gas turbine plant of three processes selected from the result of cycle analysis have been discussed previously paper(I) has been carried out under specified inlet and outlet conditions. Independent variables such as number of parallel connection, tube diameter, shell side and tube side pressure loss as well as dependent variables such as shell diameter, number of tubes, number of serial connections were all characterized according to the standardization or so. Search method was used to construct a computer simulation together with the calculation of heat transfer rate by logarithmic mean temperature difference method. Strength analysis of major parts was carried to examine their dimensions satisfying heat transfer and pressure loss requirements.

• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.97-108
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• 2010

Fluid-elastic instability and turbulence-induced vibration of steam generator U-tubes of a nuclear power plant are studied numerically to investigate the effect of design changes of support structures in the upper region of the tubes. Two steam generator models, Model A and Model B, are considered in this study. The main design features of both models are identical except for the conditions of vertical and horizontal support bars. The location and number of vertical and horizontal support bars at the middle of the U-bend region in Model A differs from that of Model B. The stability ratio and the amplitude of turbulence-induced vibration are calculated by a computer program based on the ASME code. The mode shape with a large modal displacement at the upper region of the U-tube is the key parameter related to the fretting wear between the tube and its support structures, such as vertical, horizontal, and diagonal support bars. Therefore, the location and the number of vertical and horizontal support bars have a great influence on the fretting wear mechanism. The variation in the stability ratios for each vibrational mode is compared with respect to Model A and Model B. Even though both models satisfy the design criteria, Model A shows substantial improvements over Model B, particularly in terms of having greater amplitude margins in the turbulence-excited vibration (especially at the inner region of the tube bundle) and better stability ratios for the fluid-elastic instability.

• Plant Journal
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• v.15 no.2
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• pp.56-61
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• 2019

In this study, the failure analysis of the internal tube occurred in the high pressure feedwater heater for power generation boiler of 500 MW supercritical pressure coal fired power plant was investigated. I suggested a prediction model that can diagnose internal tube failure by changing the position of level control valve on the shell side and the suction flow rate of the boiler feedwater pump. The suggested prediction model is demonstrated through additional cases of feedwater system unbalance. The simultaneous comparison of the shell side level control valve position and the suction flow rate of the boiler feedwater pump compared to the normal operating state value, even in the case of the high pressure feedwater heater for the power boiler, It can be a powerful prediction diagnosis.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1256-1261
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• 2009

Seawater amounts to 70% of the earth and represents a quite unlimited resource for the production of fresh water by desalination processes and for the extraction of dissolved salts present in it. Recently, the falling film evaporation has increased in interest as an efficient method for seawater desalination system. In the desalination system, the flow characteristics of the falling film is very important issue to make highly efficient system. So, this study is taken to investigate numerically the falling film thickness on the inlet Renold Number ranges are 400 to 700. Numerical simulations are performed using FLUENT6.3.26, a commercial CFD code.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.3
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• pp.8-14
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• 2011

The clogging of the flow area at the tube support plates(TSPs), especially at the upper TSPs results in the water level oscillation of a steam generator during normal operation. A reduction of the TSP flow area causes to increase in pressure drop within the two-phase flow zone, which destabilizes the boiling flow through the tube bundle. This phenomenon was occasionally observed at a few domestic and foreign nuclear power plants. One of the methods for defining the flow area clogging is visual inspection, which is the most effective inspection method. The results of the visual inspection for TSPs' flow area are clogging images on TSPs' quartrefoil lobes. These images are complexly distorted due to lens aberration and external factors like the distance to a subject and angle etc. In this work, we developed the analysis algorithm for clogging image of the TSP flow area of steam generators. For this purpose, we designed an image verification device applicable to the camera employed in the field for visual inspection and then, we demonstrated the validity of image analysis algorithm by using this device and commercial autoCAD program.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.228-236
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• 1996

An electrolysis system with a vertically circulating mercury capillary bundle electrode was developed with a very large electrode area in a minimum space. This system was operated by forcedly feeding mercury and aqueous solution containing metal ion into a fiber bundle packed densely within a small porous glass tube. In order to test the characteristics and stability of the electrolysis system, the reduction voltammograms of uranyl and ferric ions were measured with changes of the mercury flow rate and the aqueous flow rate. The aqueous flow rate had a large effect on the electrochemical reaction of metal ion occurring at the interface between the mercury and the aqueous solution and had to be regulated as an appropriate value to have a good limiting current shape. The limiting current was linearly proportional to the aqueous flow rate, and complete reductions of uranyl and ferric ions were rapidly and continuously accomplished at the potential showing limiting current. With a mercury flow rate high enough to keep a capillary continuum of mercury in the fiber bundle, the mercury flow rate had almost no effect on the electrochemical reaction. This system was confirmed to be effective and stable enough to control rapidly and continuously the oxidation state of metal ions fed into the system under an appropriate aqueous flow rate.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.98-104
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• 2005

Pannier-arrangement condensers are usually adopted in the turbine generator units of combined cycle power plants. Optimization of operating performance and economy is an important goal, which requires accurate understanding of flow and heat transfer effects in the condenser. The tube bundle arrangement and steam flow behaviors of pannier-arrangement condensers are very different from those of common condensers. The physical model for existing numerical simulation program of condenser is refined by constructing the correlations for flow resistance and condensation heat exchange coefficient in which the influences of steam flow direction are considered according to available experimental data. The adaptability of the developed physical model and simulation program of pannier-arrangement condenser is verified with available experimental data.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1536-1537
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• 2005

We have made point electron sources using carbon nanotubes (CNTs). For the fabrication of point electron sources, CNTs were dispersed in a solution and attached on electrochemically etched W tips using electrophoresis. In our study, we have utilized various CNTs such as single-walled CNT (SWCNT), multiwalled CNT (MWCNT), and thin-MWCNT and threshold current, turn-on voltage, filed enhancement factor of each emitter have been studied upon a tube/bundle diameter and length. In addition, fieldemitted electron energy distribution of various CNT emitters is characterized.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.393-398
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• 2001

Pulsations, vibration and stress are the basic dynamic phenomena in power plant piping systems which directly affect system reliability. These phenomena are both acoustical and mechanical in nature and are closely interrelated. It was noticed that thermodynamic parameters were changed after replacing with new type tube bundles of reheat exchanger. It was reported later that the drain piping connecting the new bundle header with the associated drain tank is regularly pulsating at about every 3 second with 13.4㎐ and 7.5mm, p-p in amplitude. This amplitude is about 6 times higher than reference level of sound piping. The results of finite element analysis of the pipeline showed that its dominant natural frequency is 13.4㎐. The soundness is predicted whether the bending dynamic stress evaluated excesses the maximum allowable high cycle fatigue stress or not by the measured amplitude of vibration.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.243-251
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• 2004

Absorption chiller/heater can utilize the unused energy of the daily life waste heat, the industry waste heat. the solar energy and the earth energy. These can contribute to energy savings. But the absorption chiller/heater has a demerit that the size of absorption chiller/heater is larger than that of the vapor compression type based on same capacity. In this study. the experimental apparatus of an absorber is manufactured as a plate. which is newly applied in an absorber. The experimental apparatus is composed of a plate type absorber. which can increase the heat exchange area per unit volume and thus facilitating to deeply investigate more detail features instead of that done by the existing type. i.e.. horizontal tube bundle type. The characteristics of heat transfer and refrigeration capacity are studied experimentally. The absorption enhancement by using surfactant is closely examined through the experiment and comparative figures are presented in quantitative and qualitative analysis.