Numerical predictions of wavy fin coil performance

A numerical study has been conducted to predict the air-side heat transfer and pressure drop characteristics of a 2-row finned tube heat exchanger having a herringbone wavy fin geometry. The calculations were performed using the FLUENT CFD code, Ver. 4.5. The calculations were performed in three dimensions and account for conduction within the fins. The computational domain was chosen to cover the entire fin length in the air flow direction. The calculations are implemented for the frontal air velocities between 1.0 and 3.0m/s yielding hydraulic diameter Reynolds number from 380 to 1150. The uniqueness of this work is inclusion of the tubes in the wavy channel geometry, and use of a three-dimensional (3D) calculation model. The flow and thermal fields in this finned tube heat exchanger as well as the temperature distribution of the fin are presented and described, The fin efficiency is numerically determined and compared with that given by the Schmidt equation (1949) and found to agree within +/- 2.3%. Predictions were performed for a herringbone channel without and with tubes. The tubes considerably increase the pressure drop, but the effect on the average heat transfer coefficient is much smaller. The calculation results are compared with test data taken by Kang and Webb (1998) for a test sample having the same geometry. The FLUENT over predicts the air-side heat transfer coefficient by 6% and pressure drop by 13%.