Experimental and Numerical Investigations on n-Decane Thermal Cracking at Supercritical Pressures in a Vertical Tube

The flow and heat-transfer behavior of thermal cracking n-decane was investigated experimentally and numerically. An electrically heated vertical tube (2 mm inner diameter) was applied to carry out thermal cracking of supercritical pressure n-decane at various pressures, temperatures, and resident times. The results showed that the second-order reactions increase the formation rates of the light products (especially CH4 and C2H4) for conversions greater than 13%, while the heavy product (C5–C9) formation rates are decreased. A global reaction model is given for n-decane conversions less than 13%, including 18 main product species. A computational fluid dynamics (CFD) model was developed using the real thermal properties and coupled with fuel flow, heat transfer, and wall thermal conduction. Three turbulence models were tried out and then compared to the experimental results. The "SST k–ω model" can better predict the wall temperature than other turbulence models. The predicted fuel and wall temperatures are in good agreement with experimental data. The results also show that n-decane continues to crack with almost half of the n-decane conversion in the connection pipe. Thus, the thermal cracking in the connection pipe should be more carefully analyzed in cracking models.