An assessment of pressure drop and void fraction correlations with data from two-phase natural circulation loops

Void fraction and pressure drop correlations play an important role in pred icting the performance of natural circulation loops. Hence an assessment of the commonly used and often cited correlations for pressure drop and void fraction has been carried out with data from natural circulation loops. Thi s assessment considered 33 void fraction correlations and 14 pressure drop correlations. The void fraction correlations were initially tested against the various limiting conditions. Only 14 correlations were found to satisfy at least two limiting conditions (i.e., at x = 0; alpha = 0 and at x = 1; alpha = 1) and were assessed against the data. This assessment showed that the Chexal et al. (1996) correlation is better than all the others consider ed. The assessment of pressure drop correlations were carried out with the Chexal et al. (1996) correlation for void fraction and Saha-Zuber model for the onset of subcooled boiling. This assessment showed that most correlati ons give predictions close to each other.