In this work, subcooled droplet impact on a highly thermally conductive spherical surface was investigated both theoretically and experimentally. Specifically, the effect of Weber number on spreading of droplets of three different liquids namely water, isopropyl alcohol and acetone was studied. The droplet shape evolution and surface wetting upon droplet impact at surface temperatures ranging between 20 o C and 250 o C were investigated using a high speed camera. Maximum droplet spread was measured and compared with available correlations. Generally wetting contact was observed at surface temperatures below or close to saturation temperature whilst a non-wetting contact was exhibited at surface temperatures significantly greater than the saturation temperature. The drop in surface temperature was found to be significantly lower in this non-wetting contact regime which led to significant reduction in heat transfer coefficient. Despite a very small temperature drop in the film boiling regime indicating small fraction of vaporization, Schlieren imaging of acetone droplets showed qualitative vapour field around the rebounding droplets. The droplet spreading patterns in cold condition and film boiling regime were simulated using the 3D CFD models which were found to be in good agreement with the experimental observations.

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Intensification is intrinsic to better chemical and process engineering and has always been used in practice. Multiphase reactions and reactors are ubiquitous in chemical and allied industries and are of great economic and ecological importance. There is a great scope for intensifying multiphase reactions and reactors for realizing productivity enhancements, which are crucial for sustainable manufacturing. These enhancements can be in terms of increased throughput; better yield, conversion, and selectivity; smaller environmental footprint; and intrinsically safer operations. The advances in intensified reactors especially micro-reactors and microfluidic devices have created significant awareness about intensification in recent decades. In this note, we discuss different strategies for intensifying multiphase reactions and reactors based on the published information. Variety of tools and examples are presented to showcase the potential of intensification. We have found the efforts towards intensification of multiphase reactions and reactors very rewarding academically as well as professionally. We hope that this note will further stimulate interest in this area and pave the way towards realizing next generation productivity for chemical and allied industries.

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