Numerical implementation of the Cheng and Todreas correlation for wire wrapped bundle friction factors-desirable improvements in the transition flow region

The Cheng and Todreas (1986) correlation is widely used for calculation of pressure loss in wire wrapped hexagonal rod bundles. Recent application indicates that the transition region friction factor calculated causes reverse pressure drop as flow rate increases in the vicinity of the transition to turbulent boundary. A modified friction factor formula for the transition region is proposed to avoid this anomalous behavior. The newly introduced exponent in this formula was calibrated by 58 available bundle data sets to be 13. This modified formula not only achieves the original objective but also slightly improves the accuracy of prediction in the transition region.