Abstract: The transient gas to particle heat transfer for fluidized and spouted regimes was studied using a Eulerian–Eulerian two-fluid model (TFM) in conjunction with the kinetic theory of granular flows (KTGF). The inlet gas temperature was transient which increased with time. Effect of modelling parameter of specularity coefficient on the simulation results was studied. It was found that specularity coefficient is a critical parameter which affects on the particles behaviour and the value of 0.025 leads to creation of incoherent spouting similar to the measurements. The temporal variation of particles concentration and temperature distribution in the spouted and fluidized regimes were compared with the corresponding experimental data for three distinct regions of spout, fountain and annulus. It was shown that the CFD model predicted the particles distribution properly for both regimes. In addition, the CFD predictions for particle temperature distribution for the spouted regime were in a better agreement with the measurements, when compared with that for the fluidized regime.