In this study, numerical analysis of water and water based nanofluids in ETSCs were made by using CFD. Validation of the study was made by comparing an experimental and two different numerical results. Thanks to the analyzes, the effects of water based Al2O3-H2O and CuO-H2O nanofluids compared to water on heat transfer for different volume fractions of nanoparticle, different collector angles, different mass flow rates and different numbers of evacuated tubes were examined. According to these parameters, the thermal and hydraulic statuses of the collector were examined by using the Boussinesq approximation and the tank outlet temperatures were determined. It has been determined that the use of nanofluid in ETSC systems has improved heat transfer and the best improvement was obtained with CuO-H2O nanofluid.