Complex turbulent flow and heat transfer characteristics of tubes with internal longitudinal plate-rectangle fins in EGR cooler

Complex flow and heat transfer characteristics of the tubes with internal longitudinal plat-rectangle fins in EGR (Exhaust Gas Recirculation) cooler are investigated by experiment. Each internally finned tube is single-tube structure. The effects of internal fin width, inscribed circle diameter, wave number and upwind distance on heat transfer performance are examined. The range of internal fin width is from 2.5 mm to 3.5 mm, inscribed circle diameter selects 5 mm, 7 mm and 9 mm, and wave number gets 3, 4, 5. The heat transfer coefficient, friction factor and Nusselt number in the fully developed region are obtained. The experimental results show that the friction factor increased with the increase of wave number, while it decreases with the increase of internal fin width and inscribed circle diameter. When 4.4 mm ≤ D_h ≤ 4.9 mm, d_ins = 7 mm (d_ins/D_i = 50%) and N = 4, the heat transfer enhancement effects of internally finned tubes should be the best. Moreover, general correlations are proposed to describe the characteristics of the fin configuration for 1689 ≤ Re ≤ 5076, 4.05 mm ≤ D_h ≤ 14 mm. In addition, when manufacturing the internally finned tube, it is better to select large upwind distance.