4.2. Pressure drop
The experimental data of frictional pressure drop of water
through the smooth surface plate is compared with the calculated
results. As shown in Fig. 8, the pressure drop, which is calculated
with the friction factor correlation of Nilpueng and Wongwises
[15] and Kakac and Liu [16] agrees reasonably with the experimental
data. The mean absolute deviation (MAD) between measured
data and prediction results with friction factor correlation obtained
from Nilpueng and Wongwises’ correlation and Kakac and Liu’s
correlation is 9.89% and 27.43%, respectively. The effects of water
velocity and surface roughness on the frictional pressure drop
(dPF) are represented in Fig. 9. The frictional pressure drop
increases exponentially as the water velocity increases. In addition,
it can be clearly observed that the pressure drops increased with
increasing surface roughness.