where k and n are the number of the selected dimensionless groups
and the sample data points, respectively. With the methods used by
Fang and Xu [34] and Fang et al. [35], ten dimensionless groups
from the best existing correlations are initially chosen. Then,
through variable transformations the dimensionless groups are
reduced to eight (k = 8). Substituting the eight dimensionless
groups into Eq. (6), the general form of heat transfer correlation
for supercritical water heat transfer becomes