Direct numerical simulations are performed to quantify the mixing performance of reactors commonly used for crystallization assisted by supercritical fluid above the mixture critical point. Two different reactors are tested: the semi-continuous reactor of milliliter volume range and the continuous microfluidic chip of nanoliter volume range. The current work shows that high performance computing (HPC) is a modern tool useful to analyze various designs and to quantify performances in chemical engineering. In-depth discussions on the numerical methods chosen to strike a good balance between accuracy and CPU time are presented. Physical analysis is also conducted with an emphasis on the turbulent mixing performance of the reactors. The results show a good mixing for the supercritical technologies considered and underline the increased mixing performance of the microfluidic chip.