43 8 Vol. 43,No. 8 2009 8 Atomic Energy Science and Technology Aug. 2009,, (, 710049) :,,,,,,,,, ;, : ; ; ; : TL33 :A :100026931 (2009) 0820730208 Effects of Curvature on Characteristics f or Annular Flo w in Vertical Narro w Annular Gap DU Dong2xiao, SU Guang2hui, Q IU Sui2zheng ( S tate Key L aboratory of M ulti p hase Flow in Power Engi neering, X i an J iaotong Universit y, X i an 710049, China) Abstract : Based on t he separated flow model, a mathematical model for annular upward flow in vertical narrow annuli wit h bilateral heating was developed. The t heoretical model is based on t he mass, momentum, and energy conservation equations of liquid films and the moment um conservation equation of t he vapor core. The predicted result s agree wit h t he experimental data very well. By numerically solving t he equations, t he influences of curvat ure o n t he characteristics of annular upward flow, including liquid film t hickness, temperat ure and velocit y dist ributio n in liquid films and critical heat flux, were o btained. The t hickness of inner liquid film decreases wit h an increase in cur2 vat ure, while the t hickness of outer liquid film increases wit h curvat ure. When t he dry2 out point occurs on the inner t ube, the critical heat flux will increase with the decrease of curvat ure. And t he case reverses when t he dryout point occurs on the outer t ube. :2008205201 ; :2008209227 : (51482060105WJ0816) ; (NCET20620837) : (1985 ),,,,
8 : 731 Key words : narrow annular gap ; curvat ure ; critical heat flux ; annular flow,,,,,,,, ( ),, [122 ] 20 220 kg/ (m 2 s) 0. 1 10 MPa 0. 5 3. 5 mm ; [ 3 ],, [ 122 ], 1,,,, ( 1), :1) ;2) ;3) ;4) ;5),,, 1 Fig. 1 Scheme of annular flow in an annuli with bilateral heating [122 ] ( ),, [ 2 ], 2 xc,, s ( ) 2, 2 MPa 90 kg/ ( m 2 s),, :1), ; 2),, CH F,, xc xc, 2 2. 1 3
732 43 2 xc (a) (b) Fig. 2 Comparison between theoretical and experimental data of xc at different pressures (a) and mass velocities ( b) : s = 0. 95 mm, s = 1. 5 mm ; : s = 0. 95 mm, s = 1. 5 mm Z, 3,, :,,, o / i, 8 mm, 2. 2 4 Y, Y + = 0, Y + = 1 3 Fig. 3 Liquid film thickness vs. axial length at different curvatures :a s = 0. 95 mm ;b s = 2. 0 mm ; :c s = 0. 95 mm ;d s = 2. 0 mm,mm : 2. 0, 8. 0, 14. 0, µ 20. 0 ;,mm : 2. 0, 8. 0 ; g 14. 0, g 20. 0 p = 15 MPa, G = 80 kg m - 2 s - 1, qi = 50 kw m - 2, qo = 120 kw m - 2
8 : 733 Tk ( k i o, ) Tsat,,,,,,,,,, 0. 95 mm, ; 2. 0 mm,, 2. 3 5,,,, ;,, 2. 4 6 h,,, 2. 5 xc 7,
734 43 xc CHF :,CH F xc, CH F, ;CHF,, CHF
8 : 735 8 xc CH F :,CHF xc,ch F, 7 8, 8 mm, xc CHF,, 2. 6 p xc 9 xc p : ( 3 MPa ), xc p ; p 3 MPa, xc p ; xc 8 12 MPa, ; 8 mm, xc p p 2. 7 G xc 10, xc G : xc G ; 8 mm, G x c,, xc,, xc, 8 mm,, 8 mm, 3,,
736 43
8 : 737 1), ;,, 2),,, 3) 8 mm, : [1 ] SU Guanghui, GOU J unli, FU KUDA K J. A theoretical model of annular upward flow in a vertical annulus gap [J ]. Journal of Nuclear Sci2 ence Technology, 2003, 40 (1) : 1211. [ 2 ] SU G H, GOU J L, QIU S Z, et al. Theoretical calculation of annular upward flow in a narrow annuli with bilateral heating [ J ]. Nuclear Engi2 neering and Design, 2003, 225 (223) : 2192247. [3 ],,,. [J ]., 2007,41 ( ) :68273. DUAN Feng, SU Guanghui, QIU Suizheng, et al. Influence of heat flux ratio on dryout point in narrow annuli[j ]. At Energy Sci Technol, 2007, 41 (Suppl. ) : 68273 (in Chinese).