Numerical modelling of combustion in radiant tube heaters

Increasing the efficiency of a heating process means reducing the expenses for heating purposes and the economical heating method has been researched for many years. Within the scope of the study, the combustion event inside the U-type radiant tube placed in a room and the changes in the external environment were investigated numerically with the help of the Computational Fluid Dynamics (CFD) program. These calculations were compared with experimental data from the literature. In addition, the turbulence model, radiation model, thermal power and air excess coefficient parameters were changed and the effects of these changes on the radiant heater wall temperature, the temperature distribution in the radiant heater and the temperature distribution in the outdoor environment were investigated. In numerical studies, the Fluent package program was used as a Computational Fluid Dynamics (CFD) program. Calculations were carried out in three dimensions. Standard k-ε, RNG k-ε model and Realizable k-ε model were applied separately as turbulence model. As the combustion model, the eddy dissipation model, which is included in the species transport model, was applied. DO model and P1 model were applied separately as radiation model. When the results are examined, it is seen that the numerical results obtained in the case of using the P1 radiation model and the Standard k-ε model are quite close to the experimental results. In cases where the best results were obtained, the P1 radiation model and the Standard k-ε model were used, while the maximum surface temperatures were around 700 K, this value was around 655 K experimentally. In the results obtained with the DO radiation model, very high temperatures have occurred and the maximum surface temperatures are between 900-950 K. In numerical calculations, it was determined that the increase in the thermal power and the decrease in the excess air coefficient cause an increase in the temperatures in the room.