Water heaters are important tools to use solar energy, as one of the main renewable energy sources, for increasing water temperature. The present research was conducted to predict the outlet fluid temperature of a solar water heater with a flat plate collector by the computational fluid dynamics method. Initially, the ambient temperature, the temperature of the inlet and outlet fluid, and the temperature of the collector were experimentally measured from 10 am to 18 pm every two hours. The fluid flow tubes of the flat plate solar collector were simulated in the ANSYS Fluent Software. The temperature of the outlet fluid was calculated based on the measured variables by the computational fluid dynamics method. For that, the k-ε turbulent model was used for simulating the collector in the software. Validation was carried out between experimental data and numerical results. The results of the simulation showed that computational fluid dynamics can predict the outlet fluid temperature with errors between 1 to 22% .In most cases, the predicted temperatures were higher than those of experimented data and higher errors were observed for higher flow rates.
