A solution strategy for the film model for non-isothermal gas–liquid reactions

A general solution strategy for the film model for gas–liquid reaction has been proposed using the boundary element method (BEM) of discretization over subintervals in gas–liquid films. Non-isothermal effects in the film are included and the associated temperature changes near the gas–liquid interface are computed. The accuracy of the solution procedure is first established using some simple isothermal and non-isothermal benchmark problems and with semi-analytical solutions. Then illustrative results are presented for a non-isothermal series reaction system to illustrate effects of various parameters such as Arrhenius number, solubility changes with temperature, effect of volatility of the liquid phase reactant, etc. The proposed solution method provides fast and accurate values for interfacial fluxes and fluxes into the bulk liquid in addition to concentration profiles. Hence the method is extremely useful for coupling local effects of the film model with global effects based on CFD coupled compartmental model for gas–liquid reactors.     

Automatic segmentation of coronary tree in CT angiography images

In this study, we proposed an automatic approach to segment the three‐dimensional coronary tree from computed tomography angiography (CTA) image data. Compared to the previous studies, our approach can efficiently locate the coronary root through extracting aorta by using circular Hough transform. Then, we extracted the two‐dimensional coronary borders in multiple projection directions by dynamic programming and used the border information to reconstruct the coronary surface by the spline fitting. The performance of our approach has been validated on the CTA dataset from 50 subjects, with the comparison to the manual segmentation by an experienced medical physician on the corresponding CTA data and X‐ray angiography data. Our experiments have shown that the average bias between our approach and the manual segmentation are 2.44 mm² with confidence interval [‐2.20 mm², 6.68 mm²] for cross‐sectional lumen area, 0.84 mm with confidence interval [‐2.76 mm, 4.44 mm] for maximum lumen diameter, and 0.32 mm with confidence interval [‐1.14 mm, 1.78 mm] for minimum lumen diameter. The results can demonstrate the potential effectiveness of our approach in CTA image processing.     

Mathematical modeling and simulation for gas–liquid reactors

Gas–liquid reactors are widely used in many industrial processes such as oxidation, hydroformylation, chlorination, etc. The paper develops comprehensive model for reactors using the mixing cell approach. It incorporates heat and mass transfer effects in the film and uses a boundary element method to solve the film model equations. The fluxes obtained at the interface are then directly used as the link to the reactor model. Simple isothermal and non-isothermal reactions were numerically tested. Application to two industrially important case studies, chlorination of butanoic acid and oxidation of cyclohexane are briefly illustrated. For the autocatalytic chlorination of butanoic acid, the yield of desired product, monochlorobutanoic acid, is favored by the high degree of mixing in the liquid phase. Therefore, this reaction should be carried out in a CSTR. A series of five bubble tanks with parallel gas reactant feed for cyclohexane oxidation was also simulated. It was found that the cyclohexane conversion is low while the oxygen conversion is relatively high and almost constant in each tank. Due to the complex multistep nature of this reaction scheme, oxygen is consumed in many steps of oxidation and selectivity of main products (which are intermediate products in the reaction scheme) depends on the critical control of over-oxidation in the kinetic mechanism.