Evaluation of 6 Different Correlations for the Flow Friction Factor of Stirling Engine Regenerators

The topic of this paper is to compare six well known and often used correlations for the flow friction factor of Stirling engine regenerators /1-5/. Therefore, the experimental methods and the geometric constraints in terms of the ranges of wire diameter and porosity investigated are summarized for each correlation. Additionally, the different equations for Reynolds number and flow friction factor are discussed in order to derive one general applicable set of equations for the Reynolds number and the friction factor. Using these general equations, it is possible to show all data in one plot, which gives a good impression of the characteristics of each set of data and the deviations among them. Additionally, the correlations are applied to a 2^nd order computer model (PROSA), which was used to recalculate the performance of the well known GPU-3 engine. The results of these calculations in terms of regenerator pressure drop, mechanical power output and efficiency are also presented in the paper. This clearly indicates the impact of the different correlations on the simulation results.