Heat transfer in gas fluidization is investigated at a particle scale by means of a combined discrete element method and computational fluid dynamicsapproach. To develop understanding of heat transfer at various conditions, the effects of a few important material properties such as particle size, the Hamaker constant and particle thermal conductivity are examined through controlled numerical experiments. It is found that the convective heat transfer is dominant, and radiative heat transfer becomes important when the temperature is high. Conductive heat transfer also plays a role depending on the flow regimes and material properties. The heat transfer between a fluidized bed and an immersed surface is enhanced by the increase of particle thermal conductivity while it is little affected by Young's modulus. The findings should be useful for better understanding and predicting the heat transfer in gas fluidization.