Steady-state simulation of internal heat-transfer characteristics in a double tube reactor

A novel annular reactor-double tube reactor (DTR) was utilized innovatively to provide thermal energy for thermochemical reactions. A steady-state heat transfer model of DTR was established where classical heat transfer equations between the fixed bed, the fluidized bed and the wall were considered. The independence analysis showed that the different number of meshes was irrelevant. Compared with the experimental values, it was found that the calculated values of the model deviated within +15%, which illustrated good accuracy for temperature prediction. Based on the model, the numerical simulation of DTR showed that the heat exchange mainly occurred in the area with packing through the wall on both zones. Particle diameter in the reaction zone had a greater effect on heat transfer than the particle void ratio, and the bed-wall heat transfer coefficients were more sensitive to the increase of inlet gas velocities. Heat transfer would achieve quickly in DTR with only small packing heights. When temperature differences between the inlet gases of the two zones reached 600 degrees C, the effect of the initial packing height on the fluid and solid temperature in DTR could be significantly observed, indicating the importance of the annular fixed bed in strengthening the heat transfer process.