A device for heat transfer, particularly in fluidized bed equipment. Several layers of heat exchanger tubes are provided, with radial arms mounted in between to mix and loosen the product. In addition, a process is disclosed for heat transfer in high-temperature processes for bulk material, particularly granulates or powders, in fluidized bed units, where the heat is transferred to and absorbed by the fluidized bed on several levels, and by the fluidized bulk material being agitated mechanically between these levels. This allows transfer of high energy densities without the risk of bridging or local overheating.