Augmentation of the heat transfer in a compact heat exchanger with asymmetric herringbone wavy-fin
Palavras-chave:
Compact heat exchanger, Asymmetric wavy fin, Heat transfer augmentation, Passive technique, Computational Fluid DynamicsResumo
The passive heat transfer intensification technique is a successful approach in thermal
engineering applied to the heat exchanger. Present work evaluates through numerical modeling a compact fin-
and-tube heat exchanger with asymmetric herringbone fins and aligned/ staggered circular tubes arrangement.
Numerical modeling is performed considering a steady-state and turbulent flow. Heat transfer and pressure loss
are evaluated by Colburn (j) and Friction (f) factors. A wave amplitude growth ratio of 0.8 and 1.2 were
evaluated for a range of Reynolds number between 800 and 5000. The density mesh analysis is ensured by Grid
Convergence Index methodology (GCI) and the numerical robustness is verified through experimental
comparison. Colburn factor is increased of 36% and 13% for the configuration with amplitude growth ratio of
1.2, for aligned and staggered cases, respectively, in relation to their reference cases. Friction factor is increased
of 35.3% and 12.7% for the aligned and staggered cases, respectively, for amplitude ratio of 1.2. The main flow
phenomenology found is related to the generation of downstream secondary flow, boundary layer separation at
the waves tip and reduction of the wake behind of the tubes. For higher wave amplitude, mixtures between cold
and hot streams decrease the recirculation zones and increase the local heat transfer coefficient.
