This paper proposes a simplified method based on air supply opening model to accelerate the simulation process of the ceiling diffusers. Experimentally, a sub-scale room is set-up to measure the temperature field in the room. Numerically, room with a fully description of the diffuser geometry is established. Conservation equations are solved using FLUENT commercial flow solver. The code is validated by comparing the numerical results obtained from three different turbulence models with the available experimental data. The validation shows that the standard k-epsilon turbulence model can be used to simulate the round and square diffusers successfully. After validation, a simplified model is established for the round and square diffusers. The round diffuser is replaced with a cylinder that has the same diffuser neck diameter, wherein the flow radically emerges from its outer surface. The square diffuser is simplified and simulated as a rectangular and the flow emerges from its sides in two directions. The simple method is compared with the fully description method, and it is found that this simple Method is applicable to practical room air flow simulations. This new model is simple enough to enable the modeling of a room with several diffusers. (C) 2013 Elsevier B.V. All rights reserved.