The relation between heat transfer coefficient and Reynolds
number of cold water at different surface roughnesses is shown
in Fig. 6. Based on the present data, the average relative uncertainties
of heat transfer coefficient are ±15.3%. It can be seen that the
heat transfer coefficient increases with increasing Reynolds number
and surface roughness. The increase in Reynolds number
between 1300 and 3200 results in the augmentation of the heat
transfer coefficient around 89.4%. This is because the flow mechanism
inside the corrugated channel can be divided into 2 parts:
main flow and recirculation flow [13].