We present simulation results for the freezing of a pallet comprising 40x36x18 vials and compare it with engineering runs of the Janssen COVID-19 vaccine in section 3.1; this analysis identified a number of complex freezing phenomena that are investigated in the following sections. To generalize our findings, we also studied the freezing of smaller systems, i. Unless stated otherwise, 1000 repetitions were carried out for each simulation study to capture the variability of the process. All simulations comprise vials containing 1 mL of 5 wt.% sucrose solution. The nucleation kinetics parameters used for the simulation of this solution lead to singlevial nucleation temperature distributions in the range of -5°C to -15°C, as typically observed when freezing diluted aqueous solutions in laboratory freeze-dryers. A list of all simulation parameters is provided in table .