Condensation inside smooth horizontal tubes: Part 2. Improvement of heat exchange prediction

Abstract

Original scientific paper https://doi.org/10.2298/TSCI140815045RIn this study, a theoretical model of film condensation inside horizontal tubes with more precise definition of friction coefficient on interphase is presented to calculate the heat transfer coefficient under two-phase annular and intermediate flow conditions. This more precise definition contains experimental substantiation of correction for calculation of pressure losses by friction and correction that takes into account surface suction on the interphase. Comparison of this model with the experimental data of various authors demonstrates that the results are in satisfactory and close agreement.

Substantiation and the range of application of a new method for heat transfer prediction in condensing inside plain tubes

“…Good agreement of the experiments with the calculations (divergence within 25%) proves the correctness of the Rifert et al [14] method. The practical application of the Rifert et al [14] method for calculating heat transfer under various condensation parameters is complicated by the necessity of the solution of the dependence (2) given in an implicit form. Solving the equation 2is possible in two ways.…”

“…In Table 1 it is shown the comparison of the additional complexes from (9) and for condensation of steam [24], methane [25], isobutene [17], freon R22 [14] and freon R245fa [26]. As seen from Table 1, the values of the additional complexes are practically the same (divergence within 25%).…”

“…Rifert et al [14] measured local heat transfer coefficients for condensation of steam and R22 inside a horizontal tube by the "thickness wall" method. The authors showed a good convergence of their own experimental data with the calculation by (2), on condition that the friction coefficient C f is determined by the method they proposed.…”

“…Comparison of heat transfer coefficients predicted by the Rifert et al [14] method with experimental data in condensing propylene, propane, dimethyl ether, isobutene [17] and FC-72 [18] is shown in Figs. 1-2.…”

“…The analysis of the theory [10] shows that for β > 10 (under the influence of vapour velocity on heat transfer) and Pr l = 1-3 under the changes of Re l from 8 • 10 2 to 2 • 10 4 , the impact of Re l on Nu f can be neglected. Figure 3 shows the influence of [24] for steam at Pr l = 0.95, β = 150; 2 -data from Lee et al [18] for fluid FC-72 at Pr l = 8.2, β = 40; 3 -data from Yu et al [30], Rifert et al [14], Park et al [17], Kwon et al [31] for freon R22 and from Kim et al [28] for carbon dioxide at Pr l = 2.4, β = 10; 4 -data from Kim et al [28] for carbon dioxide at Pr l = 2.4, β = 100; 5 -data from Boyko et al [24] for steam at Pr l = 0.95, β = 100 Fig. 3 displays, only at high vapour velocities (β more than 100) there is an insignificant decrease of Nu f with an increase of Re l .…”