The experimental data of the Nusselt number of cold water
inside a smooth plate is compared with the previous correlation
before the effect of roughness surface on heat transfer coefficient
is investigated as depicted in Fig. 5. It can be seen in this figure that
the tendency of predicted data and experimental results is similar.
The predicted results of Khan correlation [11] and Okada correlation
[12] give a mean absolute deviation (MAD) of 28.2% and
18.82% with experimental data.