• Title/Summary/Keyword: Fluid flow generation system

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Application of CFD Method to Performance Prediction of Fire-Suppression System for Electric Power Utilities (발전설비용 소화시스템의 성능 예측을 위한 CFD기법 적용 연구)

  • Chung, H.T.;Bae, K.Y.;Kim, C.H.;Jeong, I.S.;Bae, J.S.;Han, Y.S.;Kim, J.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.296-299
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    • 2008
  • In the present research, the exclusive analysis system based on the CFD method were suggested to predict the fire-suppression performance of water mist fire-suppression equipments for design applications. The computing scope is ranged from starting pump to fire-suppression equipments, composed of three parts that calculation of flow rate and pressure distribution at each nozzle, examining of spray performance and predicting of fire-suppression performance in the fire space. Application were done to the fire-suppression system for electric power generation plants. The results were analyzed by comparison between numerical results and initial design conditions in terms of thermal and fluid mechanics.

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A Study on the Boiling Heat Transfer of R-113 in a Concentric Annular Tube (환상이중원관에서 R-113의 비등열전달에 관한 연구)

  • Kim, M.H.;Kim, C.H.;Oh, C.;Yoon, S.H.;Kim, K.K.
    • Journal of Advanced Marine Engineering and Technology
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    • v.18 no.5
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    • pp.12-23
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    • 1994
  • The two-phase flow is observed in power plants, chemical process plants, and refrigeration systems etc., and it is very important to solve the heat transfer mechanism of a boiler, an automic reactor, a condenser and various types of evaporators. Recently, the problem of two phase heat transfer is braught up in many regions with development of energy saving technique. In flow boiling system it is necessary to store data in each condition because the heat transfer characteristics of flow boiling region vary by the change of flow pattern and the magnetude of heat flux to tube length, and be subtly affected by the flow and heating condition. So basic study for knowing flow pattern in heat transfer region and the relation between heat transfer characteristic and flow condition is desired to accumulate data in wide variety of liquid and flow system in the study of heat transfer of two phase flow. In this study R-113 was selected as working fluid whose properties were programmed by least square method, and experiment was conducted in the region of mass flow $1.628{\times}10^6$~$4.884{\times}10^6$/kg/$m^2$hr with inlet subcooling 10~3$0^{\circ}C$, sustaining test section inlet pressure to 1.5kg$_f$/$cm^2$abs.

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Design of The Micro Fluidic Heat Flux Sensor (유동형 미세 열유속 센서의 설계)

  • Kim, Jung-Kyun;Cho, Sung-Cheon;Lee, Sun-Kyu
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.11
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    • pp.138-145
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    • 2009
  • A suspended membrane micro fluidic heat flux sensor that is able to measure the heat flow rate was designed and fabricated by a complementary-metal-oxide-semiconductor-compatible process. The combination of a thirty-junction gold and nickel thermoelectric sensor with an ultralow noise preamplifier, low pass filter, and lock-in amp has enabled the resolution of 50 nW power and provides the sensitivity of $11.4\;mV/{\mu}W$. The heater modulation method was used to eliminate low frequency noises from sensor output. It is measured with various heat flux fluid of DI-water to test as micro fluidic application. In order to estimate the heat generation of samples from the output measurement of a micro fluidic heat-flux sensor, a methodology for modeling and simulating electro-thermal behavior in the micro fluidic heat-flux sensor with integrated electronic circuit is presented and validated. The electro-thermal model was constructed by using system dynamics, particularly the bond graph. The electro-thermal system model in which the thermal and the electrical domain are coupled expresses the heat generation of samples converts thermal input to electrical output. The proposed electro-thermal system model shows good agreement with measured output voltage response in transient state and steady-state.

A Study on Thermo-flow Characteristics Analysis of Electric Water Pump (전동 워터펌프의 열유동 특성 해석에 관한 연구)

  • Kim, Sung-Chul;Song, Hyeong-Geun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.5
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    • pp.95-101
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    • 2012
  • An electric water pump for engine cooling system has an advantage which particularly in the cold start, the use of the electric water pump saves fuel and leads to a corresponding reduction in emissions. The canned type electric water pump without mechanical sealing elements was selected to meet the requirements for operational reliability and life. However, the electric water pump for internal combustion engine generates much more heat loss than for hybrid electric vehicle since it is operated by the electric power of high current and low voltage. In this study, the fluid flow and thermal characteristics of the canned type electric water pump as an inverter integrated water pump has been investigated under the effects of heat generation. The analysis conditions such as outdoor air temperature of $125^{\circ}C$, water pump speed of 6000 rpm, coolant temperature of $106^{\circ}C$ and coolant flow rate of 120 L/min was used as a standard condition. Therefore, flow fields and temperature distribution inside the water pump were obtained. Also, we checked the feasibility of the canned type for the electric water pump in comparison with the mechanical seal type.

Performance Analysis on CHP Plant using Back Pressure Turbine according to Return Temperature Variation (배압터빈을 사용하는 열병합발전소의 열 회수 온도에 따른 성능특성 분석)

  • Im, Shin Young;Lee, Jong Jun;Jeon, Young-Shin;Kim, Hyung-Taek
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.6
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    • pp.26-33
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    • 2016
  • Combined heat and power (CHP) system is one of the power generation system which can generate both electricity and heat. Generally, mid-size and big-size CHP plant in Korea generate electricity from gas turbine and steam turbine, then supply heat from exhaust gas. Actually, CHP can supply heat using district heater which is located at low pressure turbine exit or inlet. When the district heater locates after low pressure turbine, which called back pressure type turbine, there need neither condenser nor mode change operating control logic. When the district heater locates in front of low pressure turbine or uses low pressure turbine extraction steam flow, which calls condensing type turbine, which kind of turbine requires condenser. In this case, mode change operation methods are used for generating maximum electricity or maximum heat according to demanding the seasonal electricity and heat.

The Wave Power Generator on Small Ship for Charging Engine Start-Up Battery (엔진 시동용 소형선 탑재형 파력 발전 시스템)

  • Kisoo, Ryu;Sungjin, Kang;Byeongseok, Yu
    • Journal of the Society of Naval Architects of Korea
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    • v.59 no.6
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    • pp.439-446
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    • 2022
  • Efforts to reduce carbon dioxide(CO2) emissions are being carried out due to climate environmental problems. Eco-friendly ships are also being developed, and various energy saving measures have been developed and applied. In ships, researches have been conducted in various fields such as electric propulsion system and energy saving devices. In addition, the development of ships using various renewable energy, such as kite using wind power and wind power generation, has been carried out. This paper proposes a plan to use renewable energy for ships by applying wave generators to small ships. In 2016, 130 small domestic ships drifted by sea due to discharge of starting storage batteries, and discharge cases accounted for the largest portion of the causes of domestic ship accidents. This is due to the excessive use of storage batteries for starting the main engine by departing in a weak storage battery state for small ships. Accordingly, two type wave power generators - opened flow wave power generator and enclosed vibrator type wave power generator - are developed for charging a starting storage battery when the ships are stationary at sea or port. Opened flow wave power generator utilizes the flow of fluid in the ship by using wave induced ship motion. Enclosed vibrator type wave power generator utilizes the pendulum kinetic energy located in a ship due to wave induced ship motion.

Numerical simulation and experimental study of non-stationary downburst outflow based on wall jet model

  • Yongli Zhong;Yichen Liu;Hua Zhang;Zhitao Yan;Xinpeng Liu;Jun Luo;Kaihong Bai;Feng Li
    • Wind and Structures
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    • v.38 no.2
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    • pp.129-146
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    • 2024
  • Aiming at the problem of non-stationary wind field simulation of downbursts, a non-stationary down-burst generation system was designed by adding a nozzle and program control valve to the inlet of the original wall jet model. The computational fluid dynamics (CFD) method was used to simulate the downburst. Firstly, the two-dimensional (2D) model was used to study the outflow situation, and the database of working conditions was formed. Then the combined superposition of working conditions was carried out to simulate the full-scale measured downburst. The three-dimensional (3D) large eddy simulation (LES) was used for further verification based on this superposition condition. Finally, the wind tunnel test is used to further verify. The results show that after the valve is opened, the wind ve-locity at low altitude increases rapidly, then stays stable, and the wind velocity at each point fluctuates. The velocity of the 2D model matches the wind velocity trend of the measured downburst well. The 3D model matches the measured downburst flow in terms of wind velocity and pulsation characteris-tics. The time-varying mean wind velocity of the wind tunnel test is in better agreement with the meas-ured time-varying mean wind velocity of the downburst. The power spectrum of fluctuating wind ve-locity at different vertical heights for the test condition also agrees well with the von Karman spectrum, and conforms to the "-5/3" law. The vertical profile of the maximum time-varying average wind veloci-ty obtained from the test shows the basic characteristics of the typical wind profile of the downburst. The effectiveness of the downburst generation system is verified.

Numerical Simulation of Irregular Airflow in OWC Wave Generation System Considering Sea Water Exchange (해수교환을 고려한 진동수주형 파력발전구조물에서 불규칙공기흐름에 관한 수치해석)

  • Lee, Kwang Ho;Park, Jung Hyun;Cho, Sung;Kim, Do Sam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.25 no.3
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    • pp.128-137
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    • 2013
  • Due to the global warming and air pollution, interest in renewable energies has increased in recent years. In particular, the crisis of the depletion of fossil energy resources in the near future has accelerated the renewable energy technologies. Among the renewable energy resources, oceans covering almost three-fourths of earth's surface have an enormous amount of energy. For this reason, various approaches have been made to harness the tremendous energy potential. In order to achieve two purposes: to improve harbor water quality and to use wave energy, this study proposed a sea water exchange structure applying an Oscillating Water Column (OWC) wave generation system that utilizes the air flow velocity induced by the vertical motion of water column in the air chamber as a driving force of turbine. In particular, the airflow velocity in the air chamber was estimated from the time variations of water surface profile computed by using 3D-NIT model based on the 3-dimensional irregular numerical wave tank. The relationship of the frequency spectrums between the computed airflow velocities and the incident waves was analyzed. This study also discussed the characteristics of frequency spectrums in the air chamber according to the presence of the structure, wave deformations by the structure, and the power of the water and air flows were also investigated. It is found that the phase difference exists in the time series data of water level fluctuations and air flow in the air chamber and the air flow power is superior to the fluid flow power.

A Study on Cooling Performance of In-wheel Motor for Green Car (그린카용 인휠 모터의 냉각 성능에 관한 연구)

  • Jung, Jung-Hun;Kim, Sung-Chul;Hong, Jung-Pyo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.1
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    • pp.61-67
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    • 2012
  • The in-wheel motor used in green car was designed and constructed for an electric direct-drive traction system. It is difficult to connect cooling water piping because the in-wheel motor is located within the wheel structure. In the air cooling structure for the in-wheel motor, a outer surface on the housing is provided with cooling grooves to increase the heat transfer area. In this study, we carried out the analysis on the fluid flow and thermal characteristics of the in-wheel motor under the effects of motor speed and heat generation. In order to check the problem of heat release, the analysis has been performed using conjugate heat transfer (conduction and convection). As a result, flow fields and temperature distribution inside the in-wheel motor were obtained for base speed condition (1250 rpm) and maximum speed condition (5000 rpm). Also, the thermo-flow characteristics analysis of in-wheel motor for vehicles was performed in consideration of ram air effect. Therefore, we checked the feasibility of the air cooling for the housing geometry having cooling grooves and investigated the cooling performance enhancement.

Position Control of Micro Particles in a Fluid Flow Using Ultrasonic Standing Wave (정재초음파를 이용한 유동중 미세 입자 위치 제어)

  • Cho, Seung-Hyun;Seo, Dae-Cheol;Ahn, Bong-Young;Kim, Ki-Bok;Kim, Yong-Il
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.2
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    • pp.131-136
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    • 2008
  • Using ultrasonic standing waves, micro particles submerged or flowing in fluid can be manipulated. Due to acoustic radiation force of ultrasound, particles are forced to move to pressure nodal or antinodal lines. In this work, we propose a method to control the position of micro particle in a flow by adjusting the frequency of the standing wave. To this end, standing wave field generation system including a few millimeter thick micro channel was established using an immersible ultrasonic transducer. The present generation system works valid in a frequency range between 2.0 MHz and 2.5 MHz. We observed the SiC particles in water moved to pressure nodal lines by the standing wave. The effect of the channel thickness and operating frequency was also investigated. Interestingly, it was shown that the operating frequency have a close relation with the location of the pressure nodal line. Consequently, it fan be said that the position of particle movement rail be controlled by adjusting the ultrasound frequency. The maximum range of the controllable position was about 261 micrometers under the given condition. The resulted observations reveal the possibility of various applications of the ultrasonic standing wave to the manipulation of particles submerged in a fluid.