• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1051-1060
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• 2003

The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm ; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1511-1516
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• 2020

The Korea Research Institute of Standards and Science (KRISS) established a new standard of the absorbed dose to water in LINAC X-ray beams. To confirm the equivalence of the new standard with other national metrology institutes (NMIs), a bilateral comparison study of the absorbed dose to water in high energy X-ray beams was performed between the KRISS and the National Metrology Institute of Japan (NMIJ). The comparison was made in-directly. Three transfer chambers were calibrated in the high energy X-ray beams by both laboratories and the calibration coefficients were compared. The average ratios of the calibration coefficients of the three transfer chambers obtained by the KRISS to those obtained by the NMIJ were 1.004, 1.006, 1.006, 1.007 for 6, 10, 15 and 18 MV X-ray beams, respectively. The calibration coefficients obtained at the KRISS were higher than those at the NMIJ but they were in good agreement within the expanded uncertainty of 1.0% (k = 2). The results of this study will be used as the evidence for the KRISS standard being comparable with those of other NMIs, temporarily, in the interim period up to finalizing a key comparison study, BIPM.RI(I)-K6 managed by the Consultative Committee for Ionizing Radiation.

• Journal of Power System Engineering
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• v.13 no.2
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• pp.49-55
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• 2009

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new tube-and-plate type condenser which will cost less and will be as efficient as the spiral type. As a standard condenser type, tube-and-plate type condenser is used in this study. A two-dimensional numerical model for the tube-and-plate type condenser is proposed, and the flow and heat transfer characteristics for several types of condensers are investigated.

• Journal of Magnetics
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• v.20 no.4
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• pp.450-459
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• 2015

In this paper, the safety distances and maximum permissible power (MPP) of resonant wireless power transfer systems are defined and derived with regard to human exposure to electromagnetic field (EMF). The definition is based on the calculated induced current density and electric field in the standard human model located between the transmitting and receiving coil. In order to avoid the adverse health effects such as stimulation of nerve tissues, the induced current and electric field must not exceed the basic restriction values specified in EMF safety guidelines. The different combinations of diameters of the coils and the distance between the two coils are investigated and their effects are analyzed. Two versions of EMF safety guidelines (ICNIRP 1998 and ICNIRP 2010) are used as bases for safety distance calculation and the difference between the two guidelines are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.141-149
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• 2002

A numerical simulation is performed for the cooling heat transfer of a heated cylindrical pedestal by an axisymmetric jet impingement. Based on the k- $\varepsilon$- f$\sub$${\mu}$/ model of Park et at., the linear and nonlinear stress-strain relations are extended. The Reynolds number based on the jet diameter(D) is fixed at Re$\sub$D/ = 23000. The local heat transfer coefficients are compared with available experimental data. The predictions by k- $\varepsilon$-f$\sub$${\mu}$/ model are in good agreement with the experiments, whereas the standard 7- f model does not properly resolve the flow structures.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.95-97
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• 2003

The cost losing synchronous through a transient instability is extremely high in modern power systems. This paper presents a power transfer capability calculation algorithm considering transient stability. The theoretical development is straightforward: dynamic equations are converted to numerically equivalent algebraic equation and then integrated into the standard formulation for power transfer capability calculation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.1
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• pp.24-28
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• 2006

This paper presents a power transfer capability calculation algorithm considering transient stability, The theoretical development is straightforward: dynamic equations are converted to numerically equivalent algebraic equation and then integrated into the standard formulation for power transfer capability calculation. The proposed method is applied to IEEE-24 Reliability Test System and the results shows the effectiveness of the method.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.79-87
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• 2002

The present work analyzed the effect of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly, by obtaining velocity and pressure fields, turbulent intensity, flow-mixing factors, heat transfer coefficient and friction factor using three-dimensional RANS analysis. NJl5, NJ25, NJ35, NJ45, which were designed by the authors, were tested to evaluate the performances in enhancing the heat transfer. Standard $\kappa-\epsilon$ model is used as a turbulence closure model, and, periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant, but the twist angle of mixing vane is changed. The results with three turbulence models( $\kappa-\epsilon$, $\kappa-\omega$, RSM) were compared with experimental data.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.959-961
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• 2003

In this paper, we describe implemented DMAC (Direct Memory Access Controller) architecture on Altera's $Excalibur^{TM}$ that includes industry-standard $ARM922T^{TM}$ 32-bit RISC processor core operating at 200 MHz. We implemented DMAC based on AMBA (Advanced Micro-controller Bus Architecture) AHB (Advanced Micro-performance Bus) interface. Implemented DMAC has 8-channel and can extend supportable channel count according to user application. We used round-robin method for priority selection. Implemented DMAC supports data transfer between Memory-to-Memory, Memory-to-Peripheral and Peripheral-to-Memory. The max transfer count is 1024 per a time and it can support byte, half-word and word transfer according to AHB protocol (HSIZE signals). We implemented with VHDL and functional verification using $ModelSim^{TM}$. Then, we synthesized using $LeonardoSpectrum^{TM}$ with Altera $Excalibur^{TM}$ library. We did FPGA P&R and targeting using $Quartus^{TM}$. We can use implemented DMAC module at any system that needs high speed and broad bandwidth data transfers.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.128-130
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• 2004

The cost losing synchronous through a transient instability is extremely high in modem power systems. This paper presents a power transfer capability calculation algorithm considering transient stability. The theoretical development is straightforward: dynamic equations are converted to numerically equivalent algebraic equation and then integrated into the standard formulation for power transfer capability calculation. The proposed method is applied to IEEE-24 Reliability Test System and the results shows the effectiveness of the method.