• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.179-189
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• 1994

A performance of reactor coolant pump in two-phase flow is examined using the pump geometric conditions and the performance of the pump in single-phase flow. Wall friction loss of the reactor coolant pump in single-phase flow is prdicted using the Truckenbrodt boundary layer theory, and the head loss in two-phase flow is predicted with calculated well friction loss and separation loss coefficients. The analysis results are compared with the Combustion Engineering pump test data. The effect of two-phase multiplier on the peak clad temperature in Loss-of-Coolant Accident is also examined using the RELAP5 and the results indicate the importance of its accuracy.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.421-426
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• 2009

This paper describes on energy loss in a pipe of refuse collecting system. Analysis energy loss in a pipe is the decisive factor in a design for refuse collecting system. From the analysis energy loss, we can determine the capacity of turbo blower. The flow characteristics in the pipe with the refuse bag are analyzed by three-dimensional Navier-Stokes analysis. The refuse bag is modeled using the actual measurement. We obtain friction factor by changing refuse bag's size and mixing ratio and Reynolds number. And From the result we calculate energy loss by using compressible flow analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.822-833
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• 2000

This experimental study concerns the characteristics of a transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure drops and skin-friction coefficients have been measured for the fully developed flow of water and that of glycerine-water solution (44%) at a inner cylinder rotational speed of $0{\sim}600$ rpm, respectively. The transitional flow has been examined by the measurement of pressure drops and the visualization of flow field, to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients and to understand the flow instability mechanism. The present results show that the skin-friction coefficients have the significant relation with the Rossby numbers, only for laminar regime. The occurrence of transition has been checked by the gradient changes of pressure drops and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, it is gradually declined for turbulent flow regime. Consequently, the critical (axial-flow) Reynolds number decreases as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the excitation of taylor vortices.

• Tribology and Lubricants
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• v.19 no.5
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• pp.292-297
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• 2003

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive (HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss form factor of HDD can be obtained from this analysis at each operation conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.159-165
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• 2001

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive(HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss from factor of HDD can be obtained from this analysis at each operation conditions.

• Journal of Biosystems Engineering
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• v.30 no.4 s.111
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• pp.202-209
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• 2005

The output of Stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, 6 kinds of steel wires, 4 kinds of combined steel wires, 8 kinds of combined steel wires with screen meshes were used. The results are summarized as follows; Among 6 kinds of steel wires $({\phi}0.7\;mm,\;{\phi}0.9\;mm,\;{\phi}1.2\;mm,\;{\phi}\;1.6\;mm,\;{\phi}2.0\;mm,\;{\phi}2.7\;mm),$ the two steel wires $({\phi}0.7\;mm,\;{\phi}0.9\;mm)$ showed the highest in effectiveness. Among 4 kinds of combined steel wires $({\phi}l.6-{\phi}l.2\;mm,\;{\phi}1.2-{\phi}l.6\;mm,\;{\phi}0.9-{\phi}l.2\;mm,\;{\phi}l.2-{\phi}0.9\;mm),\;the\;{\phi}1.2-{\phi}0.9\;mm$ showed the highest in effectiveness. Among 8 kinds of combined steel wires with screen meshes $(150-{\phi}0.9\;mm,\;150-{\phi}l.2\;mm,\;{\phi}0.9\;mm-150,\;{\phi}1.2\;mm-150,\;150-{\phi}0.9\;mm-150,\;150-{\phi}1.2\;mm-150,\;150-{\phi}l.6\;mm-150,\;150-{\phi}2.0\;mm-150),\;the\;{\phi}l.2\;mm-150$ showed the highest in effectiveness.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.562-570
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• 2003

This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed flows of water and of 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), respectively, when the inner cylinder rotates at the speed of 0～600 rpm. Also, the visualization of vortex flows has been performed to observe the unstable waves. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, whereas it becomes smaller as Re increases for the transitional flow regime and. then, it gradually approach to zero for the turbulent flow regime. Consequently, the critical (bulk flow) Reynolds number Re$\_$c/ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.10
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• pp.2630-2636
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• 1995

A theoretically based prediction for the determination of the subchannel friction factor at low pitch to the rod diameter ratio (P/D < 1.2) in the bare rod bundle flow has been developed. The present model assumes the validity of the Law of Wall over the entire flow area. The algebraic form of the Law of the Wall is integrated over the entire flow area and the local friction velocity variation along the rod periphery is considered in this study. The present method is applied to the rod bundles with P/D < 1.2, and the prediction results show good agreement with the available experimental data.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.731-734
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus with two circular manholes was installed for this study. The range of the experimental discharges were from $1.0\ell/sec$ to $4.4\ell/sec$. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios$(h_m/D_{in})$ were from 1,2 to 1.25. The average head loss coefficients for upstream manhole and downstream manhole were 0.58 and 0.23 respectively. Head loss at upstream manhole is nearly 2.5 times more than one at downstream manhole.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2095-2100
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• 2003

This Experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ration of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin-friction coefficients have been measured for fully developed flow of bentonite-water solution(5%) when the inner cylinder rotates at the speed $0{\sim}400rpm$. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number $R_o$ With respect to the skin friction coefficients. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. In all flow regime, the skin friction coefficient is increased by the inner cylinder rotation. The critical (bulk flow) Reynolds number $Re_c$ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.