Thermal-aerodynamiccharacteristicsof staggered mixed tubes bundle composed of circular and drop-shaped tubes

Abstract

The purpose of this study is to clarify heat transfer and fluid flow behavior across six-row mixed tubes bundles. The tubes bundle is consisting of circular and drop-shaped cross-sections in a staggered arrangement. The Reynolds number Re for the flow is varied from 1.78 × 10 3 to 18.72 × 10 3 . Six cases of the mixed tubes bundle are considered. The results of the mixed tubes bundles are compared with those of the circular (case I) and drop-shaped ones (case II). ANSYS Fluent soft-ware package is utilized to simulate the convective heat transfer and aerodynamic. 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 1 st , 3 rd , 5 th rows, and drop-shaped tubes in the 2 nd , 4 th , 6 th rows) increases the average-Nusselt number Nu (cid:2911)(cid:2932) by about 1 ÷ 8 % and 48 ÷ 49 % compared to that of the circular and drop-shaped tubes bundle, respectively. Case VII (drop-shaped tubes in the 1 st , 2 nd , 4 th , 6 th rows, and circular tubes in the 3 rd , 4 th rows) has the lowest friction factor 𝑓 compared to the other cases of circular and mixed tubes bundles. Moreover, the maximum values of the thermal-hydraulic performance 𝜀 are achieved in the case IV at Re = 1.78 × 10 3 and the case VII at Re > 1.78 × 10 3 , which were about 15 % and (2 ÷ 5) %, respectively, higher than those obtained for the drop-shaped tubes bundle. Generalized correlations for Nu (cid:2911)(cid:2932) , 𝑓 , and 𝜀 for the studied mixed tubes bundles were predicted.