• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.755-756
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• 2006

This paper presents the temperature distribution of the oil-immersed self-cooled transformer with radiator performed by coupled magneto-fluid-thermal analysis. Particularly, 3D temperature distribution of cooling oil and sub-components under the natural convection is obtained by computational fluid dynamics analysis, while heat sources are predetermined by magnetic field analysis using F.E.M. The predicted temperature distribution of the power transformer model is compared with the measured data for verifying the validity of the proposed analysis.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.990-992
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• 2005

This paper presents a new magneto-thermal finite element analysis for predicting the temperature rise of the EHV GIS bus bar. The power losses of a bus bar calculated by the magnetic field analysis are used as the input data to predict the temperature rise for the thermal analysis. The heat-transfer coefficients on the boundaries are analytically calculated by applying the Nusselt number considering material constant and model geometry for the natural convection. The temperature distribution in a bus bar by coupled magneto-thermal finite element analysis shows good agreement with the experimental data.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.72-79
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• 2000

In recent, occupational diseases in harmful working places become a social issue. It is the well-known fact that a respiration in polluted working places exert a serious effect on health of workers. Accordingly, the cutting off contaminants air originally is the best way to improve working environments. In these cases, ventilation systems should be essentially installed to dilute or exhaust the contaminated indoor air. In this study, we investigated the characteristics of ventilation system of the noxious gas in working indoor places with natural ventilation by using COMET. The numerical simulations were carried out the natural ventilation with two phase(air, dust). For turbulent flow, Reynolds stresses were closed by the standard $\kappa$-$\varepsilon$ model. The results are as follows ; 1) In the natural exhaust in the working place, the flows of the central region have a more rapid velocity vector than the right and left one. 2) Numerical results show that the distribution of contaminants concentration have greater influence on convection than the case of diffusion by government of velocity vectors. 3) To observe the velocity variation with distance, three location of distance are considered. As results, it shows that the velocity are 0.075(m/s) at y=5(m), 10(m) and mean concentration are raised 10.6% at y=5(m), 10(m). 4) We have presented the useful data for the adequate counterplan in the harmful working places by carrying out the various investigation of the natural ventilation.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.8-19
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• 1993

The natural convection model of the consolidated system has been developed to make sure the removal of decay heat generated in the spent fuel for the loss of forced cooling accident. The numerical technique employed was based on the ADI scheme. The calculation of heat generation rate in the spent fuel was peformed by the ANS-79 decay heat model, and the nonuniform surface heat flux is assumed with a chopped sine curve for the conservative decay heat generation input. The sensitivity study was performed to examine the possibility of the pool bulk boiling by varying the various parameters, i.e. inter-fuel spacing ratio, heat generation power, and radius of the fuel rod. The application results of this model show that the natural circulation flow through compacted spent fuel bundles enables the pool temperature to control in a safe and effective manner, after the required cooling time. The corresponding acceptance criteria of the cooling time for rearranging the spent fuel rods were also found.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.516-525
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• 1994

Since the TMI and Chernobyl accidents, many passive safety features are suggested in advanced reactors in order to enhance the safety in future nuclear power plants. In order to verify the effectiveness and provide the data for detailed design of passive cooling system, in the present work, the effects of air inlet position and external condition on the natural circulated air flow rate and the natural and forced convective heat transfer coefficient have been investigated for the one-side heated closed path such as the passive containment cooling system of the Westinghouse's AP-600. A series of experiments have been peformed with the 1/26th scaled segment type test facility of the AP-600 passive containment. Under natural and forced convection, the air velocities and temperatures are measured at several points of the air flow path. The experimental result are compared with a simple one-dimensional model and it shows a good agreement.

• Tribology and Lubricants
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• v.33 no.3
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• pp.112-118
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• 2017

Tilting pad journal bearings(TPJBs) are widely used for high speed rotating machinery owing to their rotordynamic stability and thermal management feature. With increase in the rotating speed of such machinery, an increasingly important aspect of TPJB design is the prediction of their thermal behaviors. Researchers have conducted detailed investigations in the last two decades, which provided design tools for the TPJBs. Based on these previous studies, this paper presents a thermohydrodynamic(THD) analysis model for TPJBs. To calculate pressure distribution, we solve the generalized Reynolds equation and to predict the lubricant temperature, we solve the 3D energy equation. We employ the oil mixing theory to calculate pad inlet temperature; further, to consider heat conduction via the pad, we solve the heat conduction equation for the pads. We assume the shaft temperature as the averaged oil film temperature and apply natural convection boundary conditions to the pad side and back surfaces. To validate the analysis model, we compare the predicted pad temperatures with those from previous research. The results show good agreement with previous research. In addition, we conduct parametric studies on a TPJB which was used in a gas turbine simulator system. The predicted results show that film temperature largely depends on the rotating speed and oil supply condition.

• Journal of ILASS-Korea
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• v.17 no.2
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• pp.64-70
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• 2012

Water mist fire suppression systems which use relatively small droplets of water with high injection pressure are increasingly being used in wider applications because of its greater efficiency, low flooding damage and low toxicity. However, the performance of the system significantly relies on the water mist characteristics and it requires better understanding of fire suppression mechanism of water mist. In the present study, computational fluid dynamics simulations were carried out to investigate cooling performance of water mist in heated chamber. The gas phase was prepared with natural convection heat transfer model for incompressible ideal case and then the effects of water mist injection characteristics on cooling capabilities were investigated upon the basis of the pre-determined temperature field. For the simulation of water mist behavior, Lagrangian discrete phase model was employed by using a commercial code, FLUENT. Smaller droplet sizes, greater injection angles and higher flow rates provided relatively higher cooling performance.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.3
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• pp.240-249
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• 2009

HRSG(Heat Recovery Steam Generator) building is large enclosed structure included various heat sources. This building needs to appropriately keep internal air temperature for worker's safety and operability of control devices. In this study, ventilation analysis is performed to find proper ventilation method for temperature control. Ventilation analysis is applied to entire internal space of the building with standard $k-{\varepsilon}$ model and enhanced wall treatment because of large size of the structure. And the ventilation method is considered natural and forced convection with two louver structures which has damper or not. Louver structure affect directly air circulation in near HRSG and lower region of the building. Forced ventilation provides strong inertial force which cause upward airflow. From the analysis, it is found that design requirement for internal air temperature can be satisfied by forced ventilation method with louver structure without damper.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.207-212
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• 1993

Numerical inverstigation of heat transfer in phase-change energy storage devices was performed in order to aid In the design process for a finned Phase-Change Material( PCM). A simplified model based on a quasi-linear, transient, thin fin equation, which predicts the fraction of melted phase-change material, and the shape of liquid-solid interface as a function of time, is used. The model is solved by using Finite Volume Method(FVM), and the numerical results have showed good agreement with experimental data.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.9
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• pp.434-441
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• 2003

This paper deals with the temperature characteristics according to the cooling medium and the duct size in model transformers. For the analysis and the temperature-rise tests, two 400kVA model transformers have been manufactured. One has been filled with the alpha oil as the cooling medium and constructed the duct sizes of $3\textrm{mm}$ and $5\textrm{mm}$ in the low-voltage and high-voltage windings respectively. The other has been filled the beta oil and the duct sizes were $4\textrm{mm}$ and $6\textrm{mm}$. The temperature-rise tests have been performed by the back-to-back method and the load factor has been controlled the range of 90%∼130%. The temperature values have been measured by the thermocouple and from the sixteen points in each transformer. A commercial CFD program "FLUENT" has been used for the analysis of temperature distribution. The geometry of transformer has been modeled to 3-dimensional by using the hybrid calculation mesh including the radiator. And also, the natural convection velocity has been measured at the oil top position, and compared with the calculated results.