Numerical analysis of periodically developed fluid flow and heat transfer characteristics in the triangular wavy fin-and-tube heat exchanger based on field synergy principle

In this article the three-dimensional periodically developed incompressible flow in the triangular wavy fin-and-tube heat exchanger is numerically simulated. A novel CLEARER algorithm is adopted to guarantee the coupling between the pressure and velocity, and it can also overcome the severe grid non-orthogonality in the complex wavy fin-and-tube heat exchanger. The influence of wavy angle, fin pitch, tube diameter, and wavy density on pressure drop and heat transfer characteristics is provided under different Reynolds numbers. The numerical results show that with the increase of wavy angle, tube diameter, or wavy density both the friction factor and Colburn factor will increase, while the increase rate of friction factor is higher than that of the Colburn factor. Opposite to the wavy fin-and-tube heat exchanger with uniform inlet velocity distribution, the wavy fin-and-tube heat exchanger with periodically developed flow owns a higher Colburn factor at larger fin pitch. The influence of wavy angle, fin pitch, tube diameter, and wavy density on the heat transfer performance can all be explained well from the viewpoint of the field synergy principle, and it means that the higher Colburn factor can be attributed to the better synergy between the velocity field and temperature field. Those results may provide an insight into the heat transfer enhancement in the wavy fin-and-tube heat exchanger.