• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.04a
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• pp.284-288
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• 2010

Length of staircase get longer and evacuation load get heavier in proportion to the building height. Therefore evacuation time could be considered proportional to square of building height. While smoke spreads vertically so rapidly, evacuation speed is too slow, therefore the reasonable measure for the safe of egress route is urgent. Existing pressurizing smoke control system of vertical exit route is seriously limited in function under the stack effect in winter. Stack effect in winter could be overcome with the methods of opening the staircase outward or letting airflow be free between staircase and outside.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.3
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• pp.127-133
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• 2017

Performance analysis has been carried out on a high side scroll compressor that had a fixed scroll equipped with a circular oil groove on its thrust surface. Oil was supplied to the oil groove through an intermittent opening from a high pressure oil reservoir formed inside the orbiting scroll hub. Oil in the groove was then delivered to both suction and back pressure chambers by pressure differentials and viscous pumping action of the orbiting scroll base plate. Mathematical modeling of this oil groove system was incorporated into a main compressor performance simulation program for an optimum oil groove design. The study findings were as follows. Pressure in the oil groove can be controlled by changing its configuration and the oil passage area. With an enlarged oil passage, the pressure in the oil groove heightens due to an increased flow rate, but the pressure elevation in the back pressure chamber is small, resulting in reduced friction loss at the thrust surface between the two scrolls. On the other hand, by increasing the oil passage area, the oil content in the refrigerant flow increases. Considering all these factors, the energy efficiency ratio could be improved by about 3.6% under the ARI condition by an optimal oil groove design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.237-243
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• 1996

Current low head and small scale hydroturbines have limitations in the minimum required head and flow rate for efficient operation. This study attempts to develop a new concept hydroturbine which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the economic respect could be attained. A small scale catapillar track- hydroturbine was fabricated and the performance test was carried out in a water tunnel over the head range of H = 0.8 m ~ 1.26 m. The peak turbine efficiency was 41.3% at the speed ratio of 0.6, and the turbine loss was mostly due to the friction at the chain drive used for power transmission from the runner to the shafts. This type of turbine is expected to become competitive when some improvement in the power transmission mechanism is made.

• Journal of Ocean Engineering and Technology
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• v.25 no.5
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• pp.15-20
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• 2011

This study carried out a series of experiments involving impact tests (Drop Weight type & Charpy type with a standard specimen and newly designed I-type specimen), hardness tests, and fracture surface observations of French-made roll shell steel (F), abnormal roll shell steel (M), reheated roll shell steel (R), and S25C steel under heat treatment conditiAn experimental study was carried out to study the solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. The lift forces acting on a fluidized particle play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport, the cleaning of particles from surfaces, etc. In this study a clear acrylic pipe was used to observe the movement of solid particles. Annular velocities varied from 0.4 to 1.2 m/s. The effect of the annulus inclination and drill pipe rotation on the carrying capacity of a drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully-developed flows of water and aqueous solutions of CMC (sodium carboxymethyl cellulose) and bentonite. The rotation of the inner cylinder was efficient at carrying particles to some degree. For a higher particle volume concentration, the hydraulic pressure loss of the mixture flow increased because of the friction between the wall and solids or between solids.

• Journal of the Korean Institute of Gas
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• v.13 no.5
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• pp.7-14
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• 2009

This study describes to analyze the pressure drop characteristics for the air-particle flow in pneumatic coal powder conveying system and to proper design of the orifice located in the system to enhance combustion efficiency in furnace of the coal-fired power plant. Usually the system consists of the straight type pipe, the curved type pipe and the elbow, which cause increase of the pressure drop. In this study, the pressure drop arised in the system with straight and curved type pipes is analyzed with interactions of motion of air flow and particles. It is realized that total pressure drop increases with increasing of the pipe length and the angle of curved type pipe due to friction loss of air and particles in the system. The program for analysis of the pressure drop and optimum design of the orifice size for air flow control in the system is developed. The result is also compared with the existing system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6B
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• pp.635-642
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• 2008

The influence of unsubmerged resistance bodies in a channel turbulence flow on energy loss was investigated by hydraulic experiments. Square-shaped multi-piers were used for unsubmerged structure or rigid vegetation in an open channel. In experimental channel flows multi-piers were arranged in double or single row along the channel direction, and mean-concept uniform elevations were attained and measured with a set of discharges and channel slopes. Applying the experimental results to the Manning equation, the equivalent resistance coefficient n, which implicates flow resistance and energy loss due to bottom friction as well as drag, was evaluated with varying the interval of piers and the uniform water depth. And the experimentally evaluated n values were compared with the semi-theoretical formula of the equivalent resistance coefficient derived from momentum analysis including a drag interaction coefficient. From the comparisons it was found that the interaction effect of piers on flow resistance was significant for the overall energy losses in a channel flow. The n values decrease when the interval of piers in flow-direction is less than about 2.2 times of the pier width. And it was also found that the n values increase with the 2/3 power of water depth in the theoretical formula, since the drag interaction coefficient was found to be mostly dependent on the interval of piers.

• Journal of the Korean Institute of Gas
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• v.10 no.4 s.33
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• pp.23-28
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• 2006

This paper presents the strength safety and the weight reduction analysis of nine gas valve models for a LPG cylinder using a finite element analysis program, MARC and Taguchi's experimental method. The maximum Von Mises stress of a gas valve body represents a safety of a brass valve structure for the given gas pressure of $91kg/cm^2$, which considered a safety factor of a LPG gas cylinder. The weight reduction analysis is very important for reducing a gas flow friction loss and a manufacturing cost as a design parameter. The calculated results present an design model 9 as an optimized design data with 10mm radius of a lower part gas flow pipe A, 6mm radius of an upper part gas flow pipe B and a connecting length 2 mm of tapered pipe D between lower and upper pipes.

• Nuclear Engineering and Technology
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• v.28 no.1
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• pp.56-71
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• 1996

The local hydrulic characteristics in subchannels of 5$\times$5 nuclear fuel bundles with spacer grids were measured at upstream and downstream of the spacer grid for the investigation of the spacer grid effects on turbulent flow structure by using an LDV(Laser Doppler Velocimeter). The measured parameters are axial velocity and turbulent intensity, skewness factor, and flatness factor. Pressure drops were also measured to evaluate the loss coefficient for the spacer grid and the friction factor for rod bundles. From these data, it was found that the turbulent mixing and forced mixing occur up to $x/D^h=10$ and 20 from the spacer grid, respectively. The turbulence decay behind spacer grid behaves in the similar decay rate as turbulent flow through mesh grids or screens. Mixing factors useful in subchannel analysis code were correlated from the data and show the highest value near spacer grid and then have a stable values.

• International Journal of Fluid Machinery and Systems
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• v.9 no.3
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• pp.194-204
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• 2016

Floating ring seals offer an opportunity to reduce leakage flows significantly in rotating machinery. Accordingly, they have been applied successfully to rotating machinery within the last several decades. For rocket turbopump applications, fundamental behavior and design philosophy have been revealed. However, further work is needed to explore the rotordynamic characteristics associated with rotor vibrations. In this study, rotordynamic forces for floating ring seals under rotor's whirling motions are calculated to elucidate rotordynamic characteristics. Comparisons between numerical simulation results and experiments demonstrated in our previous report are carried out. The three-dimensional Reynolds equation is solved by the finite-difference method to calculate hydrodynamic pressure distributions and the leakage flow rate. The entrance loss at the upstream inlet of the seal ring is calculated to estimate the Lomakin effect. The friction force at the secondary seal surface is also considered. Numerical simulation results showed that the rotordynamic forces of this type of floating ring seal are determined mainly by the friction force at the secondary seal surface. The seal ring is positioned almost concentrically relative to the rotor by the Lomakin effect. Numerical simulations agree quite well with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.10
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• pp.773-778
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• 2015

The local heat transfer and pressure drop of developed turbulent flows in convergent/divergent channels with square axial cross-sectional areas were experimentally investigated to improve the channel design, such as a gas turbine cooling system. Square convergent/divergent channels with one ribbed wall were manufactured with a fixed rib height e of 10 mm and a ratio of rib spacing p to height e of 10. The measurement was conducted for Reynolds numbers from 15,000 to 89,000. Convergent, divergent, and straight channels with ratios $D_{ho}/D_{hi}$ of 0.75, 1.33, and 1.0, respectively, are considered. Of the three channel types, the ribbed divergent channel was found to produce the best thermal performance under identical flow rate, pumping power, and pressure loss conditions.