• Title/Summary/Keyword: Mixing performance

Search Result 1,398, Processing Time 0.033 seconds

분배계통에 따른 지하주차장 환기설비 성능의 예측

  • 김경환;이재헌;오명도;김종필
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.13 no.10
    • /
    • pp.982-992
    • /
    • 2001
  • In this paper, the performance of ventilation equipments in enclosed parking garages were investigated for several air distribution systems by numerical method. Air change effectiveness of the non-mixing system was 0.42. It meant that more supply air as much as the design supply air was needed to maintain good indoor air quality. In the high speed nozzle ventilating system which is most expensive one, air change effectiveness was 0.54. Therefore this system satisfied to ventilation design. In the jet fan ventilating systems, air change effectiveness for jet fan ventilating system-A with 18 jet fans and jet fan ventilating system-B with 6 jet fans in circulation mixing arrangement were 0.565 and 0.42 respectively. Jet fan ventilating system-C with 6 jet fans in transport mixing arrangement was 0.535. Jet fan ventilating system-A and jet fan ventilating system-C met the ventilation design. But velocity in jet fan ventilating system-A was over 2.0m/s which is inappropriate in human comfort. Therefore this system is not proper to ventilation. Jet fan ventilating system-C was the optimum one for enclosed parking garages among 5 systems examined in this paper.

  • PDF

A Study on the Thermal Protection Performance of Elastomeric Insulators in Different Mixing Environments (탄성내열재 배합 환경에 따른 내열 성능 변화에 관한 연구)

  • Kim, Namjo;Seo, Sangkyu;Kang, Yoongoo;Go, Cheongah
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.23 no.1
    • /
    • pp.108-115
    • /
    • 2019
  • The thermal response of elastomeric insulators used as protection against high-temperature and high-pressure combustion gases varies depending on their composition and thermal environment conditions. In this paper, the thermal response characteristics of elastomeric insulators in different mixing environments were compared. Tests to determine thermal protection performance were carried out using a thermal protection rubber evaluation motor(TPREM), combustion gas velocities of 20 m/s and 100 m/s were tested at a chamber pressure of 1,000 psig. The pressure time curve of the chamber, the temperature time curve of the internal materials, the residual thickness and the thermal destruction depth of the test specimens were obtained. The results showed that the thermal protection performance of elastomeric insulators in different mixing environments was similar.

Frquency Characteristics of Electronic Mixing Optical Detection using APD for Radio over Fiber Network (무선 광파이버 네트웍(RoF)을 위한 APD 광전 믹싱검파의 주파수 특성)

  • Choi, Young-Kyu
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.58 no.7
    • /
    • pp.1386-1392
    • /
    • 2009
  • An analysis is presented for super-high-speed optical demodulation by an avalanche photodiode(APD) with electric mixing. A normalized gain is defined to evaluate the performance of the optical mixing detection. Unlike previous work, we include the effect of the nonlinear variation of the APD capacitance with bias voltage as well as the effect of parasitic and amplifier input capacitance. As a results, the normalized gain is dependent on the signal frequency and the frequency difference between the signal and the local oscillator frequency. However, the current through the equivalent resistance of the APD is almost independent of signal frequency. The mixing output is mainly attributed to the nonlinearity of the multiplication factor. We show also that there is an optimal local oscillator voltage at which the normalized gain is maximized for a given avalanche photodiode.

Turbulent Heat Transfer with Mixing Vane in Nuclear Fuel Assembly (핵연료 봉다발내 혼합날개에 의한 난류열전달 해석)

  • Jung, Sang-Ho;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
    • /
    • v.10 no.4
    • /
    • pp.9-14
    • /
    • 2007
  • The purpose of present work is to analyze the convective heat transfer downstream of mixing vane in subchannel of nuclear reactor with three-dimensional Navier-Stokes equations. SST model is selected as a turbulence closure by comparing the performances of two different turbulent closures. Three different shapes of mixing vane are tested. And, thermal-hydraulic performances of these vanes are discussed. The results show that twist of the vane improves the heat transfer performance far downstream of the vane.

A NUMERICAL STUDY ON FLOW AND STIRRING CHARACTERISTICS IN A MICROCHANNEL WITH PERIODIC ARRAY OF CROSS BAFFLES (엇갈림 배플 구조의 마이크로 채널 내 유동 및 혼합 특성에 관한 수치해석적 연구)

  • Heo, S.G.;Kang, S.M.;Suh, Y.K.
    • Journal of computational fluids engineering
    • /
    • v.11 no.4 s.35
    • /
    • pp.101-106
    • /
    • 2006
  • In the microfluidic devices the most important thing is mixing efficiency ol various fluids. In this study a newly designed miler is proposed to enhance the mixing effect with the purpose to apply it to microchannel mixing in a short future. This design is composed of a channel with cross baffles periodically arranged on the both bottom and top surfaces ol the channel. To obtain the yow patterns, the numerical computation was performed by using a commercial code, ANSYS CFX 10.0. To evaluate the mixing performance, we computed Lyapunov exponent and obtained Poincare sections. it was shown that our design provides the excellent mixing effect.

Simultaneous mixing and pumping using asymmetric microelectrodes (비대칭 미세전극을 이용한 동시 혼합 및 펌핑)

  • Kim, Byoung-Jae;Yoon, Sang-Youl;Lee, Kyung-Heon;Sung, Hyung-Jin
    • 한국가시화정보학회:학술대회논문집
    • /
    • 2007.11a
    • /
    • pp.77-83
    • /
    • 2007
  • This paper presents numerical and experimental works for simultaneous pumping and mixing small liquid using asymmetric microelectrode arrays, based on AC electroosmotic flows. To this end, four arrangements of electrode pairs were considered with diagonal/herringbone shapes. Numerical simulations were made of three-dimensional geometries by using the linear theory. The results indicated that the helical flow motions induced by the electrode arrays play a significant role in the mixing enhancement. The pumping performance was influenced by the slip velocity at the center region of the channel compared to that near the side walls. To validate the numerical predictions, the microfluidic devices were made through MEMS. The flow rate was obtained by using micro PIV, increasing the applied frequency. The electrolyte was potassium chloride solution. The flow patterns above electrodes were visualized to see lateral flow for mixing. The experimental results showed good agreements with the numerical predictions.

  • PDF

Effect of cake resistance by first-aggregation of in-line injection system (인라인 주입방식의 최초응집이 케이크 저항에 미치는 영향)

  • KIM, Taeyoung;PARK, Heekyung
    • Journal of Korean Society of Water and Wastewater
    • /
    • v.22 no.3
    • /
    • pp.281-288
    • /
    • 2008
  • Cake resistance is influenced by floc size deposited on membrane surface. Enlarging floc size can reduce cake resistance. The small particles are enlarged by coagulation and flocculation process in conventional mixing tank at membrane filtration system. Fully-grown flocs for reducing the cake resistance, however, are ruptured while passing through a pump. In light of this fact, this study aims to experimentally look at the reaggregation phenomenon of mixing system. In addition, reaggregation phenomenon of mixing system is compared with first-aggregation of in-line injection system in which coagulant is injected just before a pump. These results suggest that first-aggregation of in-line injection system is better than reaggregation of mixing system for G-value above $3100sec^{-1}$. Since G-value in pipe of actual membrane filtration system are usually larger than $3100sec^{-1}$. The performance of in-line injection system is expected to be better than the conventional mixing tank system.

Pressure Drop in Motionless Mixers

  • Yang, Hei-Cheon;Park, Sang-Kyoo
    • Journal of Mechanical Science and Technology
    • /
    • v.18 no.3
    • /
    • pp.526-532
    • /
    • 2004
  • A motionless mixer consists of a straight pipe or transfer tube containing the mixing elements that are used to cut, fold, twist, and re-combine the mixing fluid. The number of elements and their shape required in any application depend on the complexity of the mixing process. The objectives of this study are to develop new motionless mixers and to perform the experimental investigation of pressure drop in order to evaluate the performance of the new ones. Glycerin is used as a mixing fluid. Pressure drop is measured using a hydraulic manometer and correlations of friction factor are proposed as a function of Re. The friction factors of Sulzer SMX mixer are in qualitative good agreement with the published data. On the average, the friction factors of SSC and YNU mixers are about 36% lower than and 6% higher than that of the Sulzer one.

Shape Optimization of A Twist Mixing Vane in Nuclear Fuel Assembly (핵연료 봉다발내 비틀린 혼합날개의 형상최적설계)

  • Jung, Sang-Ho;Kim, Kwang-Yong
    • The KSFM Journal of Fluid Machinery
    • /
    • v.12 no.4
    • /
    • pp.7-13
    • /
    • 2009
  • The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of inverse of heat transfer rate and friction loss. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

SHAPE OPTIMIZATION OF A Y-MIXING VANE IN NUCLEAR FUEL ASSEMBLY (핵연료 봉다발내 Y 혼합날개의 형상최적설계)

  • Jung, S.H.;Kim, K.Y.;Kim, K.H.;Park, S.K.
    • Journal of computational fluids engineering
    • /
    • v.14 no.2
    • /
    • pp.1-8
    • /
    • 2009
  • The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.