Simulation of heat transfer and fluid flow of hot oil in radiation section of an industrial furnace considering coke deposition

In this study, a steady three-dimensional simulation of the coil containing hot oil in the radiation section of the vertical cylindrical furnace of an industrial unit was investigated with and without considering oil decomposition and coke formation. Flow velocity and pressure, fluid outlet temperature, and coil wall temperature at different points of the coil were calculated using computational fluid dynamics. For model validation, the values of the simulated coil wall temperature at the end of the flow path and also the outlet fluid temperature from the coil were compared with the industrial data. For the simulation case of without deposition, the wall and outflow temperature showed 211.19% and 13.47% deviation, respectively. In order to improve the results, the simulation was repeated considering coke layer on the coil. The coke thicknesses in different passes of the coil were estimated using a trial-and-error procedure. The results indicated that the deviations for the wall temperature and the fluid temperature reduce to 14.25% and 12.48%, respectively. Results showed that the deposited coke layer reduced the temperature of the heat transfer fluid and enhanced the coil wall temperature. Then, the exact analyses of the fluid temperature, velocity, and pressure and also the wall temperature in different points of a coil’s bend were performed for the two cases of without deposition and with deposition. The minimum and maximum velocities were observed at the entrance to and exit from a bend, respectively.