Flow and heat transfer characteristics of staggered mixed circular and drop-shaped tube bundle

The purpose of this study is to clarify heat transfer and fluid flow behavior across six-row mixed tube bundles. The tube bundle consists of circular and drop-shaped cross sections in a staggered arrangement. The Reynolds number Re for the flow is varied from 1.78 × 103 to 18.72 × 103. Six cases of the mixed tube bundle were considered. The results of the mixed tube bundles were compared with those of the circular (case I) and drop-shaped ones (case II). The Ansys Fluent software package was utilized to predict the flow pattern over the tube bundles. The results of the numerical simulation showed that the cross-sectional shape of the tubes and their location in the bundle significantly affect the heat transfer and pressure drop in the bundle. Case IV (circular tubes in the first, third, and fifth rows and drop-shaped tubes in the second, fourth, and sixth rows) increases the average Nusselt number Nu¯ by about 1.11%–8.10% and 47.86%–49.04% compared to that of the circular and drop-shaped tube bundles, respectively. Case VII (drop-shaped tubes in the first, second, fourth, and sixth rows and circular tubes in the third and fourth rows) has the lowest friction factor f compared to the other cases of circular and mixed tube bundles. Moreover, the maximum values of the thermal–hydraulic performance ε were achieved for case IV at Re = 1.78 × 103 and the case VII at Re >1.78 × 103, which were about 14.55% and (2.08–4.49)%, respectively, higher than those obtained for the drop-shaped tube bundle. Generalized correlations of Nu¯, f, and ε for the studied mixed tube bundles were predicted.