To increase the yield and selectivity in reactive bubbly flows, the gas-liquid interactions have to be understood in depth. In the current fundamental study, flow and concentration data of the wakes of two-dimensional bubbles in an organic solvent are obtained experimentally in a flat-bed reactor. The unsteady mass transport phenomena in these turbulent wakes of two freely rising, two-dimensional bubbles with bubble Reynolds numbers $\mathrm{Re}=949$ and $\mathrm{Re}=388$ are evaluated by analyzing Lagrangian Coherent Structures (LCS). To reveal how LCS govern the transport of dissolved gas in bubble wakes, and therefore affect gas-liquid reactions, LCS in two-dimensional velocity fields are computed and compared with concentration fields of dissolved gas. The analysis of backward Finite Time Lyapunov Exponent (bFTLE) fields reveals coherent fluid dynamic structures for both bubble Reynolds numbers studied. In the higher bubble Reynolds number case, two types of coherent structures are found, which hinder the mixing of the dissolved gas and the liquid bulk. Repelling LCS are found to enclose parcels transported into the vortices, and indicate thus, which fluid parcels can possibly take part in chemical reactions. Due to higher mixing, unveiled by details from the LCS and FTLE analyses, and therefore increased contact area between dissolved gas and fresh liquid, higher yields of reaction products are suggested for the lower bubble Reynolds number case in this two-dimensional study. This is contradicting the rule of thumb that mixing increases for higher bubble Reynolds numbers.

A custom-developed magneto-mechanical resonator (MMR) for wireless pressure measurement is investigated for potential applications in process engineering. The MMR sensor utilises changes in the resonance frequency caused by pressure on a flexible 3D printed membrane. The thickness of the printed membrane plays a crucial role in determining the performance and sensitivity of MMRs and can be tailored to meet the requirements of specific applications. The study includes static and dynamic measurements to determine the pressure sensitivity and temporal resolution of the sensor. The results show a minimum sensitivity of 0.06 Hz mbar − 1 and are in agreement with theoretical calculations and measurements. The maximum sensor readout frequency is 2 Hz in this study. Additionally, the temperature dependence of the sensor is investigated, revealing a significant dependence of the resonance frequency on temperature. The developed MMR offers a promising and versatile method for precise pressure measurements in process engineering environments.

Additive Manufacturing (AM), particularly Laser Powder Bed Fusion (PBF-LB/M), has transformed the production of complex metallic structures, enabling applications in smart reactors where enhanced heat and mass transfer at minimal pressure drop are critical. Triply Periodic Minimal Surface (TPMS) structures, such as Gyroid-TPSf and Schwarz-Diamond-TPSf geometries, offer unique advantages due to their high surface area-to-volume ratios, tunable porosity, and zero mean curvature. However, their manufacturability using PBF-LB/M remains underexplored, especially for demanding applications in process engineering that require structural integrity under extreme conditions. This study investigates the design and manufacturability of TPMS structures using 316L stainless steel via PBF-LB/M, focusing on the interaction of the key parameters porosity, unit cell size, and sheet thickness, of which two are independent variables while the third is a dependent variable. Through numerical simulations, experimental validation, and process optimization, practical design guidelines are developed. In this study, the design parameters of Gyroid-TPSf and Schwarz-Diamond-TPSf samples include porosities ranging from 70 to 90% and unit cell sizes from 2 to 20 mm. The results indicate that specifically, at large unit cell sizes (e.g., 20 mm), the decreased curvature radius reduces self-supporting effects, leading to insufficient mechanical stability during printing and resulting in local deformation. Conversely, at small unit cell sizes combined with high porosity levels (e.g., 2 mm and 90%), the sheet thickness becomes critically thin, often below the printable resolution, resulting in incomplete or fragile structures. CFD simulations were validated against experimental data across various volume flow rates. This work enables a knowledge-based selection of a suitable type of TPMS and its design parameters depending on the required flow characteristics in a given process engineering task while maintaining manufacturability. In conclusion, the study underscores the need for further refinement of design and manufacturing processes to fully exploit their benefits.