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This work investigates the heat transfer design and performance of three general types of ammonia reactors for Power-to-Ammonia (P2A). Specifically, the reactors are an adiabatic quench cooled reactor (AQCR), an adiabatic indirect cooled reactor (AICR), and an internal direct cooled reactor (IDCR). We present rigorous steady-state and dynamic models for the three reactor types. Steady-state optimisation at nominal load shows that the AICR and IDCR achieve the highest reactant conversion at 30.0% and 29.4% respectively, whereas the AQCR reaction conversion is significantly lower at 26.9%. Through open-loop simulations around the optimal operating point, we illustrate the unstable oscillatory dynamics of the AQCR. In contrast, the AICR and IDCR showcase stable and fast decaying oscillations. Nonetheless, our stability analysis reveals that the optimal operating points for all reactors are situated precariously close to the reactor extinction threshold. As a result, even minor disturbances pose a substantial risk of extinguishing the reactors at optimal operating conditions. We optimise the reactors across an operating window from 30% to 130% of its nominal load, reflecting varying load in a P2A plant. Over this operational range, the AICR and IDCR yield similar reactant conversions and demonstrate adaptability to varying loads by achieving significantly higher conversions at lower loads. In contrast, the AQCR shows a less pronounced increase in reactant conversion at reduced loads. Considering the location of the optimal operating points close to reactor extinction, we evaluate operating the reactors at a 15 K higher feed temperature than optimal value (stability margin). Our analysis demonstrates that a 15 K safety margin only slightly reduces ammonia conversion across the operating window, while ensuring stable operation even in the event of a 15% decrease in the catalyst activity. • Dynamic and steady models for three types of ammonia reactors (AQCR, AICR, IDCR). • Heat exchange design in ammonia reactors for Power-to-Ammonia operation. • Optimisation and comparison of reactor conversions at nominal load. • Step responses of the reactors to disturbances in feed temperature. • Optimal and stable operation from 30% to 130% of nominal load. [ABSTRACT FROM AUTHOR]

• Experimentally-validated model to predict size and distribution of nanoparticles. • Model couples time-resolved fluid dynamic simulations with population balance. • Increasing mixing rate, increases overall nanoparticle synthesis but not local rate. • Combination of fast mixing and high rate leads to a burst of nuclei formation. Achieving size control during nanomaterial synthesis is critical for their deployment in numerous applications due to their strong size-properties relationships. However, it remains a challenge in the field due to multi-step mechanisms in nanoparticle synthesis. In this paper, we present an experimentally-validated model able to predict the particle size and distribution of silver nanoparticles synthesised in flow reactors by coupling time-resolved fluid dynamic simulations with population balance. The model reveals fundamental correlations between reactor design and the corresponding size of the nanoparticles. It shows that increasing mixing rate, increases the overall rate of nanoparticle formation, where nanoparticle synthesis takes place homogeneously in the whole of the reaction volume. In contrast, when there is a distinguishable interface between reactant streams (i.e. low mixing rate), nucleation and growth take place in a small fraction of the reaction volume in the interface between the inlet streams. The combination of fast mixing and high average nucleation rate can lead to a burst of nuclei formation translated in small size and narrow size distribution. This work presents a new approach for the use of computational-guided design of reactors for the synthesis of nanomaterials to move the field away from current trial-and-error strategies. [ABSTRACT FROM AUTHOR]