The energy
balance of the test section is illustrated in Fig. 4, indicating
the test section, which was well insulated. The single-phase Nusselt
numbers were also compared with the prediction methods of
Gnielinski [24] and Lee and Garimella [25], which were applied
for laminar developing flow. The comparisons presented in Fig. 5
indicate that the experimental results tended to agree fairly with
the predictions, corresponding to a uniform heat flux boundary
condition.