Improvements to the Cheng-Todreas wire-wrapped rod bundle friction factor correlation in response to pin number and in the transition flow region

Abstract

The Cheng-Todreas Detailed (CTD) Pressure Drop Correlation (1986) is the most accurate correlation for measuring the pressure drop of sodium coolant through a Sodium-Cooled Fast Reactor (SFR). Although CTD is the most accurate correlation, there is room for improvement with new data and modern ways to visualize data and check the accuracy of changes easily. This thesis attempts to offer a method for altering the CTD correlation to better account for changing pin numbers in SFR assemblies, and a better fit for the correlation to the data in the transition flow region between turbulent and laminar flow. Although CTD is more accurate than other correlations, it shows an inverse response to changing pin number in some geometries of bundle assemblies. In this thesis, a method is laid out to attempt to correct for that inverse response. Although no successful conclusion was reached, the thesis also offers a method for future attempts at improvement. In addition, a set of Matlab codes are offered that allow changes to be easily attempted and checked for validity. In addition, examining the data points of bundles in the transition flow regime shows possibilities for improving the accuracy of the correlation in that flow region. Two changes are implemented in this thesis: a change to the equation for the boundary between laminar and transition flow, and a change to the transition region friction factor equation. Both changes, when implemented, offer slight improvements to the overall accuracy and precision of the Cheng-Todreas Pressure Drop Correlation..