Computational fluid dynamics (CFD) method was employed to study the effect of a novel internal-hollow cross disk (HCD) on flow and cracking in coil by coupling flow and energy equations with cracking reaction kinetics. Simulation results implied that geometrical structure change of inner wall surface by HCD embedment in cracking coil re-distributed patterns of flow field and strengthened radial velocity at reasonable pressure loss. The resulting longitude vortex disrupted flow boundary layer and improved near-wall turbulence

which in turn reduced thermal resistance and enhanced homogeneity of temperature distribution. Compared to regular cracking coils

the coil with HCD modification increased C3H8 conversion by 7.24%

olefin selectivity by 3.67%

and overall olefin yield by 6.94% which C2H4 yield had a slight decrease of 0.87% while C3H6 yield had a notable rise of 16.50%. Moreover

radial velocity from longitudinal vortex was found to promote exchange of near-wall high-temperature fluid to central low-temperature fluid with maximum temperature difference between fluids of 0.7℃. At the outlet

concentration of coking component of C6 and higher

was found decreased by 28.33% in coil with HCD than that in counterpart

indicating that HCD introduction could prevent near-wall high temperature and over-cracking and inhibit occurrence of coking. HCD strengthening mechanisms on heat and mass transfer were quantitatively analyzed and an overall evaluation was performed with consideration of pressure loss and performance improvement.