Numerical study of turbulent flow and heat transfer in cross-corrugated triangular ducts with delta-shaped baffles

Abstract

Cross-corrugated duct is commonly employed in plate heat exchanger. In this study, to further improve heat transfer in cross-corrugated triangular ducts, delta-shaped baffles are added. Three-dimensional turbulent flow and heat transfer in the channels with or without baffles has been numerically studied. A standard k-ε turbulence model together with enhanced wall treatment is applied to solve the turbulent flow in Re of 1000–6000. The fully developed cyclic mean Nusselt number and friction factor are obtained and validated by data from references, respectively. Influences of Reynolds number, baffle height and apex angle on heat transfer and pressure drop of the flow channel are investigated and discussed. Field synergy principle is applied to analyze the heat transfer enhancement in flow channels with or without baffles. The results show that when baffles are inserted, clockwise vortices and anticlockwise vortices are respectively generated in the low corrugations and the backward region of the baffles. Synergy effect of velocity and temperature gradient are strengthened in these vortices. Baffle height that is equivalent to corrugation height will lead to an increment of Nu by 2.1–4.3 times, but with a penalty of severe pressure loss. Flow channel at 60° apex angle performs best in heat transfer when baffle height equals to corrugation height, but in other two studied cases, apex angle of 90° performs best. When baffle height equals to corrugation height, friction factor is no longer proportional to Re in the channel with 60° and 90° apex angle.