4. SFM_web

# 4. SFM_web - ENU 4134 Separated Flow Model(s D Schubring...

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ENU 4134 – Separated Flow Model(s) D. Schubring July 29, 2010

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Learning Objectives I 1-d-i Select and implement appropriate void fraction correlations (void-quality-slip relations) I 1-d-ii Use the separated flow model (SFM) to estimate pressure drop (feeds into 5-b )
Separated Flow Model(s) In the SFM, the velocities of liquid and vapor are no longer assumed equal, although thermal equilibrium is still assumed. To close the model, we need some relation to replace v f = v g . In general, these relations are termed void fraction correlations or (as in T&K), void-quality-slip relations .

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General Void-Quality-Slip Relations Some relations among void fraction, { α } , flow quality, x , slip ratio, S = { v v } / { v l } , and volumetric fraction of vapor, { β } , are general. These relations come from Chapter 5. These include: S = x 1 - x ρ l ρ v 1 - { α } { α } (1) { α } = 1 1 + 1 - x x ρ g ρ f S (2) { β } = 1 1 + 1 - x x ρ g ρ f (3) These relations are always true. You should be very adept as using these as needed.
Closure Equation Several closure relations will be explored in this course, including: I HEM, in which S = 1. I The Martinelli-Nelson void fraction, in which { α } is correlated as a function of pressure and quality for steam-water only . I The drift flux model. I Rouhani-Axelsson void fraction correlation (later – annular flow, project, etc.)

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Martinelli-Nelson Void Fraction Figure 11-17, page 497. 5/34 3'"4 ׌׻ 3064 ް৊ࢤੂ઎োࢥம ˜ÔиӠ ůПёχÔƦӠ 6.364%4 \$6=*!&7( ϒ׻ ;< =< >< ƀīƈڌம \$633&) ϖ׻ ϗ׻ Ϙ׻ Q­Xyr«¶È%\$ÈZ¶È³ 'È ৔৕৖ৗ੧੨ ѽѾѿமતம 1+,24 ĝǐ ଗटठம ߺ ѦѧѭѮӠ ͌Ӡ Ĝǐ ߹ Ҁҁ҂மȞம gyV#[.2b\$¡ )HVy¡ >}Q2O3:d¡ 3>:* 534 ӉӠ କம ȍ ߫ம ࣇம ÃŜ ōŜ Ԇம Ҹ ߯ம ͅӠ ɢӠ ¡ò ͉Ӡ 6334 6-34 §¨©ǐ íǐ ª«¬ǐðưYǐ ɤ͋Ӡ ͍̇Ӡ g¢kò 38#4 ࡯ம 9:;4 Ӿ׻ ϔ׻ 9¡"¡ ϕ׻ ¡׻ <>4*>4 \$ ?33&4 :#I¡ ɣӠ \;¡ }:ò 6 .
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