Correlations and numerical analysis of thermal-hydraulic performance of staggered mixed tube bundle composed of circular and drop-shaped tubes

Abstract

Flow and heat transfer across six-row staggered mixed tube bundles composing of circular and drop-shaped tubes have been investigated numerically. The Reynolds number Re was within the range of 1.78 × 103–18.72 × 103. Six cases of the mixed tube bundle were discussed. The streamlines, velocity, turbulent kinetic energy, temperature, and static pressure contours for the studied cases were predicted using Ansys Fluent software package. The results of the mixed tube bundles were compared with those of the circular and drop-shaped ones. The best thermal performance was obtained for case IV (circular tubes in the 1st, 3rd, 5th rows, and drop-shaped tubes in the 2nd, 4th, 6th rows). However, it was found that case VII (drop-shaped tubes in the 1st, 2nd, 4th, 6th rows, and circular tubes in the 3rd, 4th rows) has the best hydraulic performance compared to the other cases of circular and mixed tube bundles. Besides, the average Nusselt number Nu¯, friction factor f, and efficiency ε were observed to be positively correlated to the Reynolds number. As the Re increased, both Nu¯ and ε increased, while f decreased. Results showed that the maximum values of the thermal-hydraulic performance were achieved for case IV at Re = 1.78 × 103 and 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. Finally, generalized correlations of Nu¯, f, and ε (in terms of Re) were developed, offering a useful reference for the design of such heat exchangers.