摘要
Numerical studies of included angle effect on turbulent flow and heat transfer in rhombic serpentine heat exchangers are presented for the first time. Five included angles (γ) are examined, i.e. γ = 45-deg, 60-deg, 90-deg, 120-deg, and 135-deg, with rotation numbers (Ro) and coolant-to-wall density ratios (Δρ/ρ) ranging from 0 to 0.2 and 0.1 to 0.2, respectively, at a constant Reynolds number (Re) of 10,000. The Reynolds-averaged Navier-Stokes (RANS) equations with low-Re realizable k-ε model and enhanced wall treatment are solved with the tradeoff between accuracy and computational cost. Code validations are performed through the comparisons with previous measured local Nusselt number ratio (Nu/Nu ∞ ) and thermal performance factor (TPF) for both stationary and rotating channels. The results show that the value of γ significantly affects the flow fields and heat transfer behaviors in both stationary and rotating cases. In the stationary situation, the Nu/Nu ∞ distributions on leading and trailing walls of the channels with slant walls (γ ≠ 90-deg) are asymmetric. As the channel rotates, there exists a critical rotating number, Ro c , in between Ro = 0.1 and 0.2. Beyond Ro c , f/f 0 decreases with increasing γ. The friction reduction of 135-deg channel to 90-deg channel for Ro = 0.2 and Δρ/ρ = 0.1 is about 43%. Furthermore, above Ro c and a critical Δρ/ρ around 0.2, the TPF increases with increasing γ, resulting in a 6% TPF augmentation when comparing the 135-deg channel with the 90-deg one.