A kind of new modified computational fluid dynamics-discrete element method (CFD-DEM) method was founded by combining CFD based on unstructured mesh and DEM. The turbulent dense gas-solid two phase flow and the heat transfer in the equipment with complex geometry can be simulated by the programs based on the new method when the k-epsilon turbulence model and the multiway coupling heat transfer model among particles, walls and gas were employed. The new CFD-DEM coupling method that combining k-epsilon turbulence model and heat transfer model, was employed to simulate the flow and the heat transfer behaviors in. the fluidized bed with an immersed tube. The microscale mechanism of heat transfer in the fluidized bed was explored by the simulation results and the critical factors that influence the heat transfer between the tube and the bed were discussed. The profiles of average solids fraction and heat transfer coefficient between gas-tube and particle-tube around the tube were obtained and the influences of fluidization parameters such as gas velocity and particle diameter on the transfer coefficient were explored by simulations. The computational results agree well with the experiment, which shows that the new CFD-DEM method is feasible and accurate for the simulation of complex gas-solid flow with heat transfer. And this will improve the farther simulation study of the gas-solid two phase flow with chemical reactions in the fluidized bed. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 3109-3124, 2009