Fluidized beds are widely used in reactive industrial processes such as: olefins production, oil cracking or uranium fluorination because of their high efficiency mixing properties. In such processes, the chemical reaction is strongly dependent on the temperature and liquid is injected into the reactor in order to cool it. The experimental data of the time evolution of the gas temperature in an anisothermal dense fluidized bed with a liquid injection provided by INEOS is first compared with the results predicted by a simple model with an assumption of a perfectly mixed fluidized bed (uniform solid and temperature distribution in the bed). The results of this simple model show that the time evolution of the gas temperature is accurately predicted. Additionally, we point out that the wall-to-bed heat transfer plays a crucial role of the gas temperature in the bed. Then, we performed 3-D numerical simulations that let us investigate local interactions between phases and heat transfer with wall. The simulations show that the liquid evaporates quickly and the temperature is in a satisfactory agreement with the experiment data.