Fig. 12 shows the frictional resistance coefficient of water and
CueH2O nanofluids (Cu:25 nm, 0.1 wt%) with different temperature.
It can be seen from Fig. 12, the increment rate of the frictional
resistance coefficient is less than 1% in the whole working temperature
area. It indicates that the nanofluids has a little effect on
the pump power, it is suitable for solar thermal energy systems.