RegimeMaps_exampleBOARD

RegimeMaps_exampleBOARD - ENU 4134 – Regime Mapping...

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Unformatted text preview: ENU 4134 – Regime Mapping Example – D. Schubring 1 Using a flow regime map Repeating needed data from our SFM example: For the following conditions, compute the void fraction with the indicated models: m = 0.15 kg s−1 ˙ (1) 2 A = 1cm (2) −2 Gm = 1500 kg m s −1 (3) x = 0.125 (4) ◦ (5) Tsat = 270 C The liquid and vapor densities, along with pressure, need to be obtained using steam tables as: ρv = 28.1 kg m−3 (6) −3 (7) Psat = 5.505 M P a (8) ρf = 768 kg m We assumed churn flow. Is this actually the regime present? Plot the flow on the Hewitt and Roberts map (Figure 11-7, page 469)? If this flow is undergoing boiling, what regimes will it pass 2 through (i.e., compute ρl jl2 and ρv jv as a function of x)? Figure 1: Figure 11-7, page 469, T&K ENU 4134 – Regime Mapping Example – D. Schubring 2 Dropping brackets... (this becomes more common as we go through the term) 1500 = ρv jv + ρf jf ρv jv x= ρf jf + ρv jv 1500x = ρv jv (9) (10) (11) 1500 (1 − x) = ρf jf 2 ρv jv = 2 ρf jf = (12) 15002 x2 = 8.1 × 104 x2 ρv 15002 (1 − x)2 = 2930 (1 − x)2 ρf (13) (14) For x = 0.15: 2 ρv jv = = 8.1 × 104 × 0.152 = 1820 2 ρf jf (15) 2 = = 2930 (1 − 0.15) = 2120 (16) Figure 2 shows the results. The flow in question (x = 0.15) is not in the churn regime, but rather in the annular or wispy-annular regime. At most qualities, this flow is annular – typical of relatively low pressure flows. At higher pressure, lower density ratios allow for bubbly flow at a slightly higher quality. x=0.15 Figure 2: Conditions shown on the HR map. Indicated points (from top-left to bottom-right): x = 0.95, 0.85, 0.75, 0.65, 0.55, 0.45, 0.35, 0.25, 0.15, 0.05, 0.01. ...
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