• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1227-1234
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• 1994

A cold spot temperature control system for the batch annealing furnace has been established in order to reduce energy consumption which is essential to improve productivity and stabilize the properties of products. A relationship between annealing cycle time and gas flow rate is developed and also for the variation of coil cold spot temperature with time during heating, and actual temperature measurements at mid-width of each coil during soaking. The results of the temperature variation effect on the cold rolled steel sheet batch annealing are as follows. (1) Cooling rate increasing gradually with increasing atmospheric gas flow, but heating rate is hardly increasing without atmospheric gas component change. (2) In case of short time heating, the slowest heating part is the center of B coil and in case of ling time heating, the low temperature point moves from the center of coil to inside coil. (3) The outside of top coil is the highest temperature point under heating, which becomes the lowest temperature point under cooling. (4) Soaking time determination depends on the input coil width, and soaking time for quality homogenization of 1214 mm width coil must be 2 hours longer than that of 914 mm width coil.

• Nuclear Engineering and Technology
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• v.33 no.4
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• pp.397-408
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• 2001

A marine reactor shows very different thermal-hydraulic characteristics compared to a land- based reactor. Especially, study on the variation of flow field due to ship motions such as inclination, heaving and rolling is essential since the flow variation has great influence on the reactor cooling capability. In this study, the natural circulation characteristics of integral type marine reactor with modular steam generators were analyzed using computational fluid dynamics code, CFX-4, for inclined conditions. The numerical analyses are performed using the results of natural circulation experiments for integral reactor which are already conducted at Seoul National University. From the results, it was found that the flow rate in the ascending steam generator cassettes increases due to buoyancy effect. Due to this flow variation, temperature difference occurs at the outlets of the each steam generator cassettes. which is mitigated through downcomer by thermal mixing. Also, around the upper pressure header the flow from descending hot leg goes up to the ascending steam generator cassettes due to large natural circulation driving force in ascending steam generator cassettes. From this result, the increase of How rate in the ascending steam generator cassettes could be understood qualitatively.

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.120-125
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• 1997

In the present work the influence of various physical parameters on the two-phase flow behavior in a self-heated porous medium has been studied using a numerical model, that is, the effects of heat generation rate, of porosity, of particle size, and of system pressure on the dryout process. To analyze the effect of these parameters, the variation of both liquid volumetric fraction (i.e., liquid saturation) and liquid axial velocity is evaluated at the steady state or at the onset of a first boiled-out region. The analysis of computational results indicate that a qualitative tendency exists between the parameters such as heat generation rate, porosity, effective particle diameter and the temporal development of the liquid volumetric fraction field up to dryout. In addition to these parameters, a variation of fluid properties such as phase density, phase viscosity due to a change of system pressure can be used for gaining insight into the nature of two-phase flow behavior up to dryout.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.55-60
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• 1999

A centrifugal compressor was tested with three different diffusers with plate vanes. The vane inlet angle was varied from 15 to 30 dog. The higher static pressure rises are obtained with lower vane stagger angle. In the stable region the static pressure field in vaneless space is very sensitive to flow rate. The impeller has a stabilizing effect over the whole stable operating range. The diffuser has a stabilizing effect at high flow rate but is destabilizing at low flow rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.386-395
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• 2005

With the development of a living standard, the importance of indoor air conditioning system in all kinds of buildings and vehicles has increased. A lot of researches on energy losses in a duct and various kinds of flow pattern in branches or junctions have been carried out over many years, because the primary object of a duct system used in HVAC is to provide equal flow rate in the interior of each room by minimizing pressure drop. In this study, to get equal flow distribution in each branch, a blockage is applied to the rectangular duct system. The flow analysis for flow distribution of a rectangular duct with two branches was performed by CFD. By using SIMPLE algorithm and finite volume method, flow analysis is performed in the case of 3-D, incompressible, turbulent flow. Also, the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent fluid flow. The distribution diagrams of static pressure, velocity vector, turbulent energy and kinetic energy in accordance with variation of Reynolds number and blockages location in a rectangular duct show that flow distribution at duct outlets is improved by a blockage. In this rectangular duct system, mean velocity and flow rate distribution in two branch outlets are nearly constant regardless of variation of Reynolds number, and a flow pattern of the internal duct has a same tendency as well.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.60-68
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• 2010

In this study, the seepage flow monitoring method by hydaulic head loss rate graph was developed for the purpose of monitoring the seepage flow from the see side or from the lake on sea dike in which seepage force was varied periodically. The hydraulic head loss rate was defined in this method. The value of the rate is in the range from 0 to 1. the value of 0 means perfectly free flow of seepage. the value of 1 means perfect waterproofing. The value of coefficient of determination in the hydraulic head loss rate graph closer to 1 means that the seepage flow way is stable. The value of coefficient of determination in the hydraulic head loss rate graph closer to 0 means that the hole may exist or the piping may be in the progress. The pore water pressure data measured in Saemangeum sea dike was analyzed with the developed method The result showed that the variation of seepage flow state was detected sensitively by this method and the interception effect of sea dike could be estimated quantitatively.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.67-73
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• 2013

This experimental work described the effect of flow control valve type on the performance of wobble plate type fuel pump for the stable DME fuel supply. In order to study this, different four types of flow control valves (ITV, SCV, IMV and MPROP) were installed on the wobble plate fuel pump, and fuel flow rate, torque, and temperature variation of pump were investigated under various operating conditions by using pump performance test system. It was revealed that wobble plate type fuel pump worked well with ITV and SCV control valve, and the flow rate and torque of fuel pump was in proportion to the value of valve open duty. The maximum flow rate and torque of fuel pump were achieved around the 50% duty of control valve. Temperature variation at all pump measuring points were under $60^{\circ}C$ which is acceptable.

• Journal of computational fluids engineering
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• v.13 no.3
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• pp.44-50
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• 2008

The present study is carried out in order to investigate the effect of the periodic acceleration in the stenosed and bifurcated blood vessels. The blood flow and wall shear stress are changed under body movement or acceleration variation. Numerical studies are performed for various periodic acceleration phase angles, bifurcation angles and section area ratios of inlet and outlet. It is found that blood flow and wall shear stress are changed about ${\pm}20%$ and ${\pm}24%$ as acceleration phase angle variation with the same periodic frequency. also wall shear stress and blood flow rate are decreased as bifurcation angle increased.

• Journal of the Korean Society of Safety
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• v.5 no.3
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• pp.27-32
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• 1990

Standardization of solar collector test method is desirable for improvement solar collector quality and Valuation of collector thermal performance. In the present work, test loop proposed by Chun, is modified for convenience of test and obtained accurate collector thermal performance. An experimental investigation hat been carried out with a modified collector test loop under a real sun condition in order to confirm the utility of modified test loop and study the effect of variation of flow rate on thermal efficiency, the range of optimum flow rate and critical incident angle.

• Journal of the Korea Safety Management & Science
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• v.20 no.4
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• pp.7-13
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• 2018

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.