In this work the characterization of the water flow through a flat solar collector and solar collectors systems interconnected is presented. This allows analyzing the behavior of flow distribution in the headers pipe and riser tubes of flat solar collectors. The hydraulic analysis allows determining if the water flow inside the risers presents a no-uniform distribution, having that the mass flow rate through riser tubes increases when they are located a greater distance from inlet of header pipe. This effect also occurs at system composed of several solar collectors interconnected, through their own header pipes, which behaves like a simple flat solar collector with header pipe longer and major number of riser tubes.
The hydraulic model of the water flow through a flat solar collector, equipped with different number of riser tubes, is modeled in the FLUENT® software and comparing with theory and methodology knowing for the calculation of pressure drop in pipe sections and accessories. The results show the curves obtained for hydraulic behavior for the cases of study, where is observed that the water flow is no-uniform. This no uniformity provokes that the friction coefficient varies depending of the position of riser tube.