We have developed a network of pipes of dendritic geometry in a solar collector with a disc-shaped body. The fluid in the network pipes is a nanofluid composed of a mixture of nanoparticles of alumina (Al2O3) and water as a base fluid in order to harvest a greater amount of thermal energy from incoming solar radiation. The sizes of the network pipes are obtained by using constructal theory methods. Thermal conductivity was obtained by the Hamilton-Crosser model; physical properties such as density and specific heat capacity were described as a function of the volumetric fraction of nanoparticles in the fluid. Optimal size of the network presented for every level of construction was established by the condition of minimal thermal resistance. Temperature profiles and the aspect ratio of the construction elements were defined as a function of the volumetric fraction of nanoparticles. Results show that by increasing the volume fraction of nanoparticles, thermal energy gain also increases, reaching a higher outlet temperature of the fluid when alumina nanoparticles are used. (C) 2017 Elsevier Ltd. All rights reserved.