Water stream flow is the major factor that affects the performance of a spiral solar water collector, it can be maximize the collector performance by decreasing the water stream flow velocity. The water stream flow was in two spiral tube arrangements of length 15 m, diameter 0.012 m, and number of coils (11). The inner surface of the solar collector was coated with matte black paint with a mixture of nanomaterial (thermal dye with 5% TiN). The experimental rig placed in Babylon - Iraq, at longitude (44.4 E) and latitude (32.4 N) in the best experimental conditions for the province during the month's (2,3,4,5). Also, a simulation program was made to extract the results in the case of a single flow, where the geometry was drawn in the Solid Work program and then entered into the ANSYS program, where the same practical cases were applied. The experimental results were compared with the numerical results which gave a good agreement with an error percent of 11% and 8.8% in the closed and opened system, respectively. The experiment included two parts, the first part: the flow of water in four different levels at case of the closed system (1, 1.5, and 2) L/min. The second part: the flow of water was at the same levels but at case of open system. The results showed that a decrease in the mass flow rate leads to increase in exit temperature and thus increase in the temperature difference between (inlet and outlet). The maximum temperature difference in the closed system was 25.2℃ for a water flow rate of 1 L/min. The maximum temperature difference in the open system was 12.3℃ for the water flow rate of 1 L/min.

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