• Title/Summary/Keyword: Mixing Factor

검색결과 471건 처리시간 0.021초

Airside Performance of Convex Louver Fin-and-Tube Heat Exchangers

  • Kim, Nae-Hyun;Oh, Wang-Kyu
    • International Journal of Air-Conditioning and Refrigeration
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    • 제16권3호
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    • pp.100-107
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    • 2008
  • The heat transfer and friction characteristics of heat exchangers having convex louver fins are experimentally investigated, and the results are compared with those of wave fin counterparts. Eighteen samples (nine convex louver fin samples and nine wave fin samples) which had different fm pitches (1.81 mm to 2.54 mm) and tube rows (one to four) were tested. The convex angle was $11.7^{\circ}$. The j factors are insensitive to fin pitch, while f factors increase as fin pitch increases. The effect of fin pitch on f factor is more significant for the wave fin compared with the convex louver fin. It appears that the complex fin pattern of the convex louver fin induces intense mixing of the flow, and thus reduces the effect of fin pitch. Both the j and f factors decrease as the number of tube row increases. However, as the Reynolds number increases, the effect of tube row diminishes. Comparison of the convex louver fin j factors with those of wave fin reveals that convex louver fin j factors are 18% to 29% higher than those of wave fin. The f factors are 16% to 34% higher for the convex louver fin. The difference increases as fin pitch decreases. Existing correlation fails to adequately predict the present data. More data is needed for a general correlation of the convex louver fin geometry.

난류가 플랑크톤의 거동에 미치는 영향: 역학적 관점에서 본 얇은 층의 형성과정 (Effect of Turbulence on the Plankton Behavior: Mechanical Perspective of a Process for Developing Thin Layers)

  • 황진환
    • 한국해양학회지:바다
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    • 제17권4호
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    • pp.283-291
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    • 2012
  • 본 연구에서는 최근 물리적 관측 방법으로 그 존재가 확인된 얇은 층(thin layer)의 형성 메커니즘에 대하여 검토하였다. 기존의 연구들에서는 성층과 전단응력의 상대적 크기인 Richardson수가 얇은 층의 중요한 결정요인인 것으로 밝혀졌다. 성층이 없는 조건하에서의 물리적 수치 실험은 미세 난류(micro-structure turbulence)가 플랑크톤의 거동에 변화를 주어 성장과 재생산 등에 영향줄 수 있음을 설명하였다. 기존의 플랑크톤 거동에 성층과 전단응력의 효과를 고려하여 최근 Gyrotaxis의 메커니즘으로 얇은 층이 형성되는 과정을 설명하였다. 이러한 생태학적 문제에 물리학적 연구방법론의 적용이라는 최근의 연구경향은 현재 및 향후에 해양생태학에서 중요한 접근방법이라고 할 수 있다.

요인 실험분석에 의한 SB 라텍스 개질 콘크리트의 강도예측 (Strength Estimation of Stylene-Butadien Latex Modified Concrete by Factorial Experimental Design)

  • 윤경구;이주형;홍창우
    • 산업기술연구
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    • 제21권B호
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    • pp.307-315
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    • 2001
  • The purpose of this study was to provide the evaluation and prediction of strengths of SB latex modified concrete(LMC) using a statistical method and factorial experimental design method. The main experimental variables were as follows ; W/C ( 4 levels ; 31, 33, 35, 42%), S/a( 2 levels ; 55, 58%) and L/C(2 levels ; 5, 15%). The compressive strength and flexural strength of LMC were selected as a factor of response. The statistical method was carried out to analyze the results, together with factorial experimental design method and response surface method. The analysis showed that if L/C had been 15%, W/C appeared to be around 33% to achieve the design strength of $350kgf/cm^2$. In this case, the flexural strength and the slump came to around $68kgf/cm^2$ and 18cm, respectively. Eventhough the L/C varied, the design strength and W/C could be predictable together with slump value and flexural strength. As a result of series of experiments in this study, W/C and L/C were proved to be the main factors influencing on the compressive and flexural strength of LMC. Both of strength and slump values could be predictable from the mixing proportion of LMC.

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Ultrasonic Speed and Isentropic Compressibility of 2-propanol with Hydrocarbons at 298.15 and 308.15 K

  • Gahlyan, Suman;Verma, Sweety;Rani, Manju;Maken, Sanjeev
    • Korean Chemical Engineering Research
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    • 제55권5호
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    • pp.668-678
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    • 2017
  • Intermolecular interactions were studied for binary mixtures of 2-propanol + cyclohexane, n-hexane, benzene, toluene, o-, m- and p-xylenes by measuring ultrasonic speeds (u) over the entire range of composition at 298.15 K and 308.15 K. From these results the deviation in ultrasonic speed was calculated. These results were fitted to the Redlich-Kister equation to derive the binary coefficients along with standard deviations between the experimental and calculated data. Acoustic parameters such as excess isentropic compressibility ($K_s^E$), intermolecular free length ($L_f$) and available volume ($V_a$) were also derived from ultrasonic speed data and Jacobson's free length theory. The ultrasonic speed data were correlated by Nomoto's relation, Van Dael's mixing relation, impedance dependence relation, and Schaaff's collision factor theory. Van Dael's relation gives the best prediction of u in the binary mixtures containing aliphatic hydrocarbons. The ultrasonic speed data and isentropic compressibility were further analyzed in terms of Jacobson's free length theory.

PDMS-바이오 멤브렌인을 이용한 용해성과 비용해성 휘발성유기화학물질의 가스 제거에 관한 연구 (A Study on the Removal of Soluble and Insoluble gas of VOCs Using PDMS Biomembrane)

  • 하상안
    • 한국환경과학회지
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    • 제15권3호
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    • pp.211-219
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    • 2006
  • An experimental study on the removal of VOCs gas using a biomembrane reactor were carried out at various inlet gas concentration, specific loading rate, retention time and gas flow rate of volume. The variations of efficiency and various parameters, which are relevant to gas removal, with mixing of soluble gas and without have been discussed. More than 95% of the toluene and methanol present in the feed was successfully removed in each study. The elimination of methanol with mixture of soluble compound of about 300 mg/h corresponds to a portion of 21% if there is a feed stream of 1400 mg/h. On the contrary the maximum efficiency of about 72% of toluene was reached. This is to be rated as a treatment of sorption that the limiting factor of the dismantling speed could be represented by this difficult degradable component. Nevertheless the elimination capacities for this reactor for toluene were on a very high level. For substances which show a very high solubility in silicon rubber an advantage of a bio membrane is clearly shown. Therefore a similarly good result is expected for n-hexane, because of its relatively good permeability which was distinguished during permeation experiments.

Flocculating 효모균주의 재순환에 의한 Tower 발효조를 이용한 연속알콜발효 (Continuous Alcohol Fermentation by a Tower Fermentor with Cell Recycle Using Flocculating Yeast Strain)

  • 페차랏칸자나시리완;유연우김공환
    • KSBB Journal
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    • 제4권1호
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    • pp.11-14
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    • 1989
  • Tower fermentor를 이용한 연속 알콜발효에서 cell re-cycle과 aeration에 대한 영향을 검토하였다. 균주는 floc-culationg 효모인 Saccharomyces cerecisiae TS4를 를 사용하였다. 15% glucose를 사용한 cell recycle system의 연속 알콜발효에서 cell 농도는 50%/1였고, ethanol productiv는 26.4g EtOH/l-hr로서 cell농도가 가장 높은 값을 나타내었으며, aeration rate는 3.8$\times$ $10^-^3$ VVM이상부터는 ethanol pro-ductivity가 감소하였다.

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에멀젼화의 퇴적조건과 예감제 첨가에 관한 연구 (A Study on the Optimum Condition and GMB Addition in Emulsifying)

  • 안명석;조명찬;김종현
    • 화약ㆍ발파
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    • 제22권1호
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    • pp.1-4
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    • 2004
  • 우리나라에서 전통적으로 사용해 왔던 제2세대의 젤라틴 다이너마이트 폭약은 경제구조와 안전의식 및 생활환경의 급변으로 제5세대의 에멀젼폭약으로 급변, 대체되고 있다. 이제 대량생산 및 발파기술의 도입으로 벌크에멀젼폭약의 상용화가 눈앞에 다가왔다. 그러나 에멀젼 폭약 제조기술의 중요한 요소인 계면활성제에 대한 연구발표가 부족하고 특히 그라스마이크로볼륨(GMB)의 사용기술은 전무한 실정이다. 실험실연구를 통하여 에멀젼 폭약 제조시 최적의 계면활성제를 알고 그의 효율적 사용법(최적반응온도 변화도)과 GMB의 혼합적정온도와 시점을 연구하여 제조공정에서의 경제성과 안전성을 향상시켰다.

직접구동 피에조 인젝터의 CRDi 단기통 디젤엔진 연소 특성 분석 (Analysis on Combustion Characteristics of CRDi Single-cylinder Diesel Engine with Direct Needle-driven Piezo Injector)

  • 정명철;성기수;김상명;이진욱
    • 한국자동차공학회논문집
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    • 제22권5호
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    • pp.108-115
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    • 2014
  • In this study, experimental approaching method was applied under and single-cylinder engine to research the performance of direct needle-driven piezo injector (DPI) for CR direct-injection. As key-point factor of this DPI that relies on direct-acting operating of injector needle, unlike conventional hydraulic-servo, its nozzle needle can be directly driven by piezo actuator. Thus, effect of direct-acting injection of DPI on diesel combustion and emission characteristics was investigated under common-rail single-cylinder direct-injection engine, equipped with three different driving mechanism, including indirect-acting solenoid, piezo and DPI system. As main results, it found that a direct-acting piezo injector has higher of IMEP. And it has higher heat release rate during premixed combustion and mixing controlled combustion phase due to its higher heat release, even though nitrogen oxide (NOx) formations were increased slightly.

분리장치의 형상에 따른 미립자 유동특성 (Flow Characteristics of Fine Particles for Separated Device Shapes)

  • 황선경;이성수;정효상
    • 한국정밀공학회지
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    • 제30권5호
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    • pp.544-551
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    • 2013
  • Recently high speed mixer, which is mixing, grinding, dispersion for liquid-liquid material, has been widely used several industries such as food, cosmetics, pharmaceuticals, fine chemicals, electronic material. This high speed mixer has a core element part called particle separation device. Particle separation device, which makes mixed liquid and liquid material using shear forces from a rotor and a stator, is a decisive factor in the distributed parts. In this study, we examined the velocity distribution of the two models of particle separation device using computation fluid dynamics, so that we were able to see the difference of the velocity distribution according to the shape. Also, by experiment, we observed that the use of rotor-screen type is deemed more suitable in case of accurately considering the effect of improving of the dispersibility through the circulation of the future.

Effects of Gap Resistance and Failure Location on prompt Fission Gas Release from a Cladding Breach

  • Tak, Nam-Il;Chun, Moon-Hyun;Ahn, Hee-Jin;Park, Jong-Kil;Rhee, In-Hyoung
    • 한국원자력학회:학술대회논문집
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    • 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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    • pp.184-189
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    • 1997
  • A prompt fission gas release model incorporating the resistance to gas flow in the gap was developed and the effects of gap resistance and failure location on prompt fission gas release from the cladding breach were assessed. The process of prompt fission gas release from the plenum and gap into the coolant was modeled in accordance with three major phenomena: (1) transient gas flow in the gap, (2) the growth of the fission gas bubble while it is still attached to the breach, and (3) the detachment of the fission gas bubble from the breach and mixing with the coolant. The cumulative mass release fraction by the present model was calculated for the case of Young-Gwang 3 & 4 nuclear fuel rod as a typical example. The results showed that the release behavior of prompt fission gas with time was different from the frictionless model which has frequently been used in a simplified approach, and that the location of cladding failure was another key factor for the prompt fission gas release process due to the resistance in the gap.

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