Heat Transfer Around a Tube in In-Line Tube Banks Near a Plane Wall

Heat transfer in the third cylinder of four circular cylinders above a plane wall has been investigated in a crossflow of air. The turbulent boundary layer thickness along the wall with no cylinder present was about 21 mm. The cylinder diameter (d) was 15 mm, the clearance (c) between the cylinders and the wall was 0.75 ~ 60 mm (c/ d = 0.05 ~ 4.0), and the pitch (p) (which denotes the longitudinal spacing between cylinder centers) was 18 ~ 66 mm (p/d = 1.2 ~ 4.4). The Reynolds number (Re) based on the undisturbed uniform flow velocity above the wall ranged from 0.8 × 10⁴ ~ 4 × 10⁴. Variations in the characteristic features of local and mean Nusselt number Nu_m are discussed in relation to c/d, p/d, and Re. Nu_m yielded the compact expression Nu_m = 0.103 (p/d)^−0.12(c/d)^0.23Re^0.74, with a spread of ±5 percent in the ranges c/d = 0.18 ~ 0.61, p/d = 1.2 ~ 3.2, and Re = 0.8 × 10⁴ ~ 4 × 10⁴, except for the case with c/d = 0.18, p/d = 3.2.