0–1 for all types of ribbed channels with different AR and rib configurations. In Fig. 5(e) and (f), the A, B variations against AR and BR are respectively depicted. As indicated in Fig. 5(e) and (f), the zero A value at BR = 0 with no flow and the typical A coefficient and B exponent in Dittus–Boelter correlation are selected to typify the A, B values at the limiting conditions of BR = 0 and BR = 1.
Within present BR range tested, the A coefficients collected in Fig. 5(e) consistently increase as BR decreases from unity (plain channel condition) by increasing the relative rib height. However, another physical constraint at the limiting condition of BR = 0, which features the full blockage condition, calls for the vanished