Two Phase Flow Part 7-Thermodynamics and Heat Flow-Lecture Slides, Slides of Thermodynamics

Download Two Phase Flow Part 7-Thermodynamics and Heat Flow-Lecture Slides and more Slides Thermodynamics in PDF only on Docsity! Total Pressure Drop, Separated Flow Model               2 1 222 2 2 2 2 2 2 2 v 2 1 v 1 v v 1 v 1 1 cos 2 g f m g g f m m SEP lo m lo m e f x x dx G dz x xdp x d G G dz p dz f G g D                                                                  Compare it with the HEM model pressure drop in two phase flow 1 2 2 2 21 cos 2 g lo m m lo m fg m HEM e f v f Gdp dx G x G v g dz p D dz                         docsity.com Two Phase multipliers in Separated Flow Model A number of methods are available with varying degree of accuracy 1. Lockhart – Martinelli (The first method) 2. Martinelli – Nelson 3. Soliman et. al. 4. Thom 5. Baroczy 6. Chisholm 7. Jones 8. Armand – Treshov 9. Beattie – Wahley 10. Freidal et. al. docsity.com The Lockhart – Martinelli Two Phase multipliers Same functional dependence of f on Re as in HEM model v v , , Re Re Re lo l on n n lo l C C C f f f   Where the values of C and ‘n’ 1. C1 = 0.316 and n = 0.25 2. C1 = 0.184 and n = 0.2 Combine these two equations , Re Re lo ln n lo l C C f f    22 2 1l llo l l lo f x f       You Get         2 22 2 2 1 1 1 n nm e l lo l ln m e l G x D x x G D               Similarly     v2 2 2 2 2 v v v v n m e n o n m e G xD x x G D           docsity.com Lockhart and Martinelli defined the parameter X such that The Lockhart – Martinelli Two Phase multipliers 2 v l fric fric dp dz X dp dz            2 v 2 l    Under thermal equilibrium condition and using f  (Re-n) dependence X2 becomes 2 2 1 n n f g g f x X x                       For n = 0.25 0.25 1.75 2 1f g g f x X x                       For n = 0.2 0.2 1.8 2 1f g g f x X x                    docsity.com Lockhart and Martinelli suggested that the two phase multipliers for the liquid and vapour flow correlated uniquely as a function of X The Lockhart – Martinelli Two Phase multipliers 2 2 1 1l C X X     2 2 v 1 CX X    2 1 1 X X CX     C depends on type of phase flow laminar or turbulent Turbulent (L)-Turbulent (G) ϕtt C = 20 Viscous (L)-Viscous (G) ϕvv C = 5 Turbulent (L)-Viscous (G) ϕtv C = 10 Viscous (L)-Turbulent (G) ϕvt C = 12   22 1l     docsity.com