• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.275-282
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• 2008

This paper presents numerical investigation of multi-phase flow in solid rocket motor nozzle and effect of multi-phases on the performance prediction of the Solid Rocket Motor. Aluminized propellants are frequently used in solid rocket motors to increase specific impulse. An Eulerian-Lagrangian description has been used to analyze the motion of the micrometer sized and discrete phase that consist of the larger particulates present in the Solid Rocket Motor. Uniform particles diameters and Rosin-Rammler diameter distribution method has been used for the simulation of different burning of aluminum droplets generating aluminum oxide smokes. Roe-FDS scheme has been used to simulate the effects of the multi-phase flow. The results obtained show the sensitivity of this distribution to the nozzle flow dynamics, primarily at the nozzle inlet and exit. The analysis also provides effect of two phases on performance prediction of Solid Rocket Motor.

• 한국가시화정보학회지
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• 제21권3호
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• pp.23-32
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• 2023

This study aims to explore the heat transfer and flow phenomena inside an instant water heater and the influence of the design parameters of the water heater on the heating performance was investigated by 3-D numerical simulations considering heat convection. The design parameters are the heating ceramic dimension, the power of the heating device, and the water flow rate. The results show that a reasonable space for the heating device is required to optimize the heating performance. It is desirable to design higher heating device as possible for a given electric power. There exists a critical water flow rate that best meets the heating performance. The change in electric power has no impact on the flow phenomena and heating performance.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1603-1618
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• 2024

Emergency operation plans are indispensable elements for effective process safety management especially when unanticipated events occur under extreme situations. In the paper, a synthesis framework is proposed for the integration success path planning and performance analysis. Within the synthesis framework, success path planning is implemented through flow-directed signal tracing, renaming and reconstruction from a complete collection of Minimal Path Sets (MPSs) that are obtained using graph traversal search on GO-FLOW model diagram. The performance of success paths is then evaluated and prioritized according to the task complexity and probability calculation of MPSs for optimum action plans identification. Finally, an Auxiliary Feed Water System of Pressurized Water Reactor (PWR-AFWS) is taken as an example system to demonstrate the flow-directed MPSs search method for success path planning and performance analysis. It is concluded that the synthesis framework is capable of providing procedural guidance for emergency response and safety management with optimal success path planning under extreme situations.

• 한국의류학회지
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• 제37권4호
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• pp.554-564
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• 2013

This study identified the characteristic and meaning of flow experience through the experiences related to fashion models' role performance; subsequently, the following findings were obtained. First, fashion models' flow experience could be divided into characteristics such as temporality, spatiality, relationality, physicalness and pleasure. Second, the process of this flow experience ultimately led to the complete moment. The complete moment can be said to be the aesthetic experience that provides both the meaningful experience and the aesthetic pleasure; it is the experiential knowledge at the dimension of mysterious integration that their body and mind are integrated into one. The beauty that fashion models exercise at the aspect of this aesthetic experience is that of performance and is an individual physical movement where they perceive their role and exercise their inner ability to express their costume most beautifully. Accordingly, the beauty of performance can be said to mean that the fashion show was successfully held by inducing both the performer and the audience into an aesthetic response. The process of specialized planning and preparation is required for fashion models to exercise the beauty of performance at the complete movement reached through flow experience and a successful fashion show. Diverse elements of the fashion show should be more organically constituted through such a process. Fashion models should exert efforts to embody acts such as walking, posing and turning through the performance of their excellent role as well as develop a training program to complete it.

• 한국유체기계학회 논문집
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• 제19권1호
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• pp.18-23
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• 2016

A HVAC(Heating Ventilation and Air Conditioning) is adapted to increase the comfort of the cabin environment for train. The train HVAC duct system has very long duct and many outlets due to the shape of a train set. the duct cross section shape is limited by a roof structure and equipments. Therefore, the pressure distribution and flow uniformity is an important performance indicator for the duct system. In this study, the existing blow down type HVAC duct system for a train was supplemented to improve the flow uniformity by applying a design method combining design of experiment (DOE) with numerical analysis. The design variables and the test sets were selected and the performance for each test set was evaluated using CFD(Computational Fluid Dynamics). The influence of each design variable on the system performance was analysed based on the results of the performance evaluation on the test sets. Furthermore, the optimized model, whose the flow uniformity was improved was produced using the direct optimization(gradient-based method). Finally, the performance of the optimized model was evaluated using numerical analysis, and it was confirmed that its flow uniformity has indeed improved.

• 설비공학논문집
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• 제18권9호
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• pp.714-721
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• 2006

In evaporative cooling applications, the evaporation water is supplied usually sufficiently larger than the amount evaporated to enlarge contact surface between the water and the air. Especially in indirect evaporative coolers, however, if the evaporation water flow rate is excessively large, the evaporative cooling effect is not used for heat absorption from the hot fluid but spent to the sensible cooling of the evaporation water itself. This would result in a decrease in the cooling performance of the indirect evaporative cooler. In this study, the effects of the evaporation water flow rate on the cooling performance are investigated theoretically. The cooling process in an indirect evaporative cooler is modeled into a set of linear differential equations and solved to obtain the exact solutions to the temperatures of the hot fluid, the moist air, and the evaporation water. Based on the exact solutions, it is analyzed how much the cooling performance is affected by the evaporation water flow rate. The results show that the decrease in the cooling effectiveness is substantial even for a small flow rate of the evaporation water and the relative decrease is more serious for a high-performance evaporative cooler.

• 대한기계학회논문집
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• 제16권4호
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• pp.795-802
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• 1992

본 연구에서는 일정한 각도의 분사를 갖는 평씨일(plain seal)에 대하여 각 인자들이 누수성능에 미치는 영향을 수치적으로 조사하였다. 인자들로는 축방향 레 이놀즈수, 축회전속도, 분사의 유입속도, 간극비, 분사의 위치 및 유입각 등이 고려되 었다.

• 한국수소및신에너지학회논문집
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• 제25권2호
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• pp.191-199
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• 2014

Effects of design variables on the performance of a double-inlet centrifugal blower have been analyzed based on the three-dimensional flow analysis. Two design variables, blade inlet and outlet angles, are introduced to enhance a blower performance. General analysis code, ANSYS-CFX13, is employed to analyze internal flow and a blower performance. SST turbulence model is employed to estimate the eddy viscosity. Throughout the shape optimization of an impeller at the design flow condition, the blower efficiency and pressure are successfully increased by 4.7 and 1.02 percent compared to reference one. It is noted that separated flow observed near cut-off region can be reduced by optimal design of blade angles, which results in stable flow pattern in the blade passage and increase of a blower performance. The stable flow at the impeller also makes good effects at the outlet of a volute casing.

• 대한기계학회논문집B
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• 제23권6호
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• pp.695-702
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• 1999

A cross-flow fan which constitutes a fan-duct system with a stabilizer and a scroll-casing is widely used in many air-ventilating and air-conditioning devices. The cross-flow fan system has many design parameters which have crucial influence on the performance and the noise characteristics of the devices, which means many difficulties during the design stage of the devices and the general design guide has not sufficiently established yet. This study presents the experimental results of the parameter investigation of some chosen design parameter values, which are the shapes of the stabilizers, the profiles of the scroll casing part, and the diffusion angles of the flow exit. The results are expressed by the varying performance characteristics with the values of the parameters. They are found to have considerable effects on the system performance and should be considered with care in the design stage. Finally some helpful guides for the design and manufacturing of the cross-flow fan system are proposed.

• Advances in aircraft and spacecraft science
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• 제9권2호
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• pp.131-148
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• 2022

The paper presents the surface-modified NACA 2412 airfoil performance with variable cavity characteristics such as size, shape and orientation, by numerically investigated with the pre-validation study. The study attempts to improve the airfoil aerodynamic performance at 30 m/s with a variable angle of attack (AOA) ranging from 0° to 20° under Reynolds number (R_e) 4.4×10⁵. Through passive surface control techniques, a boundary layer control strategy has been enhanced to improve flow performance. An intense background survey has been carried out over the modifier orientation, shape, and numbers to differentiate the sub-critical and post-critical flow regimes. The wall-bounded flows along with its governing equations are investigated using Reynolds Average Navier Strokes (RANS) solver coupled with one-equational transport Spalart Allmaras model. It was observed that the aerodynamic efficiency of cavity airfoil had been improved by enhancing maximum lift to drag ratio ((l/d) max) with delayed flow separation by keeping the flow attached beyond 0.25C even at a higher angle of attack. Detailed investigation on the cavity distribution pattern reveals that cavity depth and width are essential in degrading the early flow separation characteristics. In this study, overall general performance comparison, all the cavity airfoil models have delayed stalling compared to the original airfoil.