Temperature fluctuations occur due to thermal mixing of hot and cold streams in the T-junctions of the piping system in nuclear power plants. Temperature fluctuations cause thermal fatigue of piping system. In the present work, thermal mixing experiments are carried out on a T-junction with water. Velocity and temperature fields are measured using hot film anemometer (HFA). Three dimensional steady state computational fluid dynamics (CFD) simulations have been carried out to predict the velocity and temperature fields. The predicted velocity and temperature fields are in good agreement with the experimental measurements. (C) 2010 Elsevier Ltd. All rights reserved.