Heat Transfer Handbook part 77. 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. | CONDENSATION IN SMOOTH TUBES 755 data analysis and physical guidance from analytical solutions. The final correlation separates the heat transfer by film condensation in the upper part of the horizontal tube from the forced-convective heat transfer in the bottom pool 12 Nu ---------- 1 Ga Pr J 25 1 - Nuy n where 0 is the angle subtended from the top of tube to the liquid level and Nuz 8 PrQ 4 C V For 0 Fr C1 - C2 - For Fri C1 C2 where Fr is the liquid Froude number. Due to the inside the radical of eq. the correlation above matches the Dittus-Boelter single-phase correlation when x 0. If the area occupied by the thin condensate film is neglected 0 is geometrically related to the void fraction by 0l sin 20l n 2n If a void fraction model is assumed this transcendental equation must be solved to obtain the desired quantity 0 . Jaster and Kosky 9776 deduced an approximate relationship which is much easier to use. In the context of the present topic their simplification can be stated as 0l arccos 2a - 1 n n The simplicity achieved by this assumption is well worth the modest errors associated with it. These errors are themselves mitigated by the fact that the forced-convective Nusselt number by which the quantity in eq. is multiplied is normally considerably smaller than the filmwise Nusselt number. The void fraction correlation of Zivi 1964 eq. was used with this correlation. Equation is to be used when G 500 kg s m2 and Frso 20. Even though the Dobson correlations yield reasonable results available data suggest the need for further 756 CONDENSATION development of heat transfer models in the wavy or wavy-annular regions at higher mass fluxes. Shear-Driven Annular Flow Condensation The annular flow regime represents the situation where the interfacial shear stresses dominate and create a nearly .
