Temperature fluctuations in a mixing tee were simulated with and without a porous media in FLUENT using the LES turbulent flow model with the sub-grid scale (SGS) Smagorinsky-Lilly (SL) model with buoyancy. The normalized mean and fluctuating temperatures are used to describe the time-averaged temperatures and the time-averaged temperature fluctuation intensities. For the tee junction without the porous media, the predicted normalized mean temperature and temperature fluctuations compare well with previous experimental data. Comparison of the numerical results with the porous media with both experimental and numerical data without porous media shows that the porous media significantly reduces the temperature fluctuations. Moreover, analysis of the temperature fluctuations and the power spectrum densities (PSD) at the locations having the strongest temperature fluctuations in the tee junction shows that the porous media significantly reduces the thermal fatigue effects and can be useful in various structures such as tee junctions, elbows, piping systems. (C) 2010 Elsevier Ltd. All rights reserved.