The temperature curves of water in the two tanks are shown in
Fig. 10. As can be seen from the data, the water temperature in
system the nanofluids as working fluid increases more quickly than
that of system water as working fluid. Before 300 min (about
14:00), the water temperature rises faster. With the solar radiation
decline, the water temperature increased more and more slowly. In
the end, it reaches the maximum value. The highest temperature of
water in CueH2O nanofluid (Cu:25 nm, 0.1 wt%) system is increased
up to 12.24% compared with water system. Fig. 11 shows the heat
gain of water in the tank. The maximum heat gain of water in
CueH2O nanofluid (Cu:25 nm, 0.1 wt%) system is increased up to
24.52% compared with water system.