TAILIEUCHUNG - Heat Transfer Handbook part 69

Heat Transfer Handbook part 69. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | 674 BOILING is determined from the liquid fraction of the flow m 1 - x using eq. . The effect of heat flux on nucleate boiling is introduced using the boiling number which is defined as Bo mhqLG 9-98 This dimensionless group represents the ratio of the actual heat flux to the maximum heat flux achievable by complete evaporation of the liquid. For Bo 230Bo0 5 aL and for Bo 1 46Bo0 5 L acb aL N8 For N the value acb is determined from eq. and the value of anb in the bubble suppression regime is calculated from F Bo0 5 exp - L Then the larger value is chosen for atp. For N the value of acb is calculated with eq. while anb in the bubble suppression regime is determined as F Bo0 5 exp - L Again one chooses the larger value for atp. In the equations above the constant F is when Bo and is when Bo . This method is also applicable to vetrical annuli. Forannulargaps between the innerand outertubes greaterthan 4 mm the equivalent diameteris the difference between the two diametesr. Forannuli less than 4 mm the equivalent diameteris obtained by evaluating the hydraulic diameter using only the heated perimeter. Kan-dlikar 1990 has also proposed a fluid-specific correlation similar to that of Shah using an empirical constant specific to the particular fluid. Gungor-Winterton Correlation Gungor and Winterton 1986 proposed a Chen type of correlation based on a large database 3693 points covering water refrigerants R-11 R-12 R-22 R-113 and R-114 and ethylene glycol for mostly vertical up flows and some vertical down flows as FLOW BOILING IN VERTICAL TUBES 675 atp EaL S anb with aL calculated from eq. using the local liquid fraction of the flow m 1 - x . Their convection enhancement factor E is E 1 24 000Bo1 16 XttJ where Xtt is the Martinelli parameter defined in eq. . Their boiling suppression factor S is S 1 ReL 17 .

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