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We develop a method to model the microwave transmissivity of row crops that explicitly accounts for their periodic nature as well as multiple scattering. We hypothesize that this method could eventually be used to improve satellite retrieval of soil moisture and vegetation optical depth in agricultural regions. The method is characterized by unit cells terminated by periodic boundary conditions and Floquet port excitations solved using commercial software. Individual plants are represented by vertically oriented dielectric cylinders. We calculate canopy transmissivity, reflectivity, and loss in terms of S-parameters. We validate the model with analytical solutions and illustrate the effect of canopy scattering. Our simulation results are consistent with both simulated and measured data published in the literature.

This study investigated the effect of multiple impeller designs and configurations on the Sauter mean diameter and the uniformity of droplet size in a 100 L scale stirred tank. By using a borescope installed inside the tank, droplet images of a highly turbid liquid-liquid system were captured even at high impeller speeds, and by adjusting the borescope position, it could be observed how the droplet size changed depending on the position. The area of the flow pattern produced by the impeller was taken as an impeller region, and it explained well the change in the droplet size due to the varying liquid phase volume and impeller spacing. In addition, the change of the Sauter mean diameter and the droplet size uniformity was also elucidated by the variation of the impeller diameter, blade angle, and number of impellers. All three parameters showed a decrease in the deviation between droplet sizes as they increased, but increasing the impeller diameter was the most effective in reducing the Sauter mean diameter itself.

This work introduces an external loop to a bubble column and presents enhanced gas exchange in the heterogeneous flow regime. Gas exchange experiments under the same amount of gas input were carried out with varying gas velocity to understand the difference of bubble characteristic between the bubble column (BCR) and the bubble column with an external loop (BCR-EL). The observation of rise and descending velocity of bubbles in the BCR-EL showed that the fraction of bubbles passing the downcomer continuously increases with the incremental superficial gas velocity. A gas molecule in the liquid phase is desorbed by another gas molecule, and this gas exchange was assumed to be a phenomenon that a reactant in the liquid phase is converted to a product. To test the validity of the assumed gas exchange as a reaction in the experiments with the BCR-EL, a modeling study was performed using Fisher-Tropsch synthesis. It prevailed that the syngas conversion was higher in the BCR at the homogeneous flow regime, while the BCR-EL at the heterogeneous flow regime (above 0.08 m/s) had higher syngas conversion than the BCR due to higher gas recycle to the downcomer.

This work addressed liquid–liquid mass transfer for actual industrial conditions of high pH with coexisting salt. The Sauter mean diameter was determined from the direct measurement of a chlorobenzene droplet size using a borescope system. At a high NaOH concentration, the droplet size decreased significantly due to the reduced density difference between two phases, and it further decreased when NaOH and NaCl coexisted. A Sauter mean diameter correlation with a density difference term was proposed, and it successfully predicted the experimental results. To determine the mass transfer coefficient, the solubility and the concentration gradient of chlorobenzene in the aqueous phase were measured under various conditions. As the NaOH and NaCl concentration increased, the solubility of chlorobenzene and the rate of change of chlorobenzene concentration in the aqueous phase both decreased, but the decrease in solubility was more pronounced. Thus, the mass transfer coefficient increased with the NaOH and NaCl co...