Process Intensification of Cooling Crystallization of Cholesterol from Acetone Solution Using CO2 Gas Bubbles: Experiments and Modeling

Mriganka Mondal ◽  
Sandip Roy ◽  
Mamata Mukhopadhyay
Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2092
Niclas von Vietinghoff ◽  
David Hellmann ◽  
Jan Priebe ◽  
David W. Agar

Segmented slug flow systems in capillaries have already shown good potential for process intensification, due to their symmetry in the characteristic flow pattern. However, several challenges remain in this technology. For instance, in gas-consuming reactions, like Aliq + Bgas→Cliq, the gas droplets shrink and may even disappear, limiting the conversions and throughputs of capillary reactor systems. To overcome such shortcomings, an intermediate gas feed was developed. In order to maintain the well-defined slug flow characteristics, it is necessary to introduce the gas rapidly and precisely, in small aliquots of <10 µL. This allows us to preserve the well-defined alternating triphasic slug flow. A miniaturized electrolysis cell, together with a flow-observing system, was thus devised and implemented successfully as an intermediate gas feed. Feeding a new gas droplet into an existing liquid–liquid segmented flow had a success rate of up to 99%, whereas refilling an existing gas droplet is often limited by a lack of coalescence. Here, only at low volumetric flows, 70% of the gas bubbles were refilled by coalescence.

2008 ◽  
Vol 12 (4) ◽  
pp. 655-659 ◽  
Manabu Itoh ◽  
Yasuo Kuniyoshi ◽  
Masaaki Yokota ◽  
Norihito Doki ◽  
Kenji Shimizu

Abba Abdulhamid Abubakar ◽  
Bekir Sami Yilbas ◽  
Hussain Al-Qahtani

Abstract Carbonated water drops impact on a hydrophobic surface is examined. The influence of CO2 gas bubbles in droplet fluid on impacting droplet characteristics, such as spreading rates and restitution coefficient, are explored. The predictions of droplet wetting diameter and spreading rates are validated through the experimental data obtained from high-speed recording. The findings reveal that predictions agree well with the experimental data. CO2 gas bubbles in the droplet are compressed by the total impact pressure of the droplet liquid while slightly reducing the gas bubble sizes. The small size of close by bubbles at high pressure can merge forming large size bubbles, which occur towards the end of droplet spreading and retraction periods. The pressure increase in the fluid gives rise to increased vertical height of the droplet and slightly reduces the droplet contact diameter on the impacted surface. The work done during the compression of CO2 gas in bubbles lowers the restitution coefficient of the droplet after the retraction period.

O. M. Katz

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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