Mist Deposition onto Hairy Root Cultures: Aerosol Modeling and Experiments

Abstract

We analyzed the applicability of the standard models for aerosol deposition in randomly packed fibrous filter beds to mist deposition across a bed of hairy roots in the nutrient mist bioreactor. Although the assumptions inherent in the models are met on a local level, the overall structure of the root bed introduces some uncertainty into the correct choice of root packing fraction and gas velocity required by the model. For reasonable parameter values, the minimum in the deposition efficiency curves is close to the peak in the mist number and mass distributions, and good penetration of the root bed is possible. We then measured the deposition of mist across a packed bed of Artemisia annua transformed roots as a function of droplet size, bed length, and gas flow rate at a root packing fraction alpha = 0.5. We compared the experimental measurements with the predictions of the aerosol deposition model and found good agreement between the measured and predicted values for the diameter where the deposition efficiency across the bed is 50%, D0.5. Agreement between the model and the experiments broke down when the flow rate was increased to the point where the creeping flow assumptions were no longer valid.

Using an aerosol deposition model to increase hairy root growth in a mist reactor

“…Although root beds have regions of high and low packing density and growth occurs in all directions, the model still describes the qualitative trends and behavior of mist deposition quite reasonably. Deposition experiments using manually packed root beds with a ¼ 0.5, showed that the model matched the experimental data quite well as long as the Reynolds number (Re) was <10 (Wyslouzil et al, 1997). The Reynolds number characterizes the relative importance of inertial and viscous forces during fluid flow, and for filtration problems:…”

“…In the current experiments, the Reynolds number was in the range of 5.29 < Re < 9.93, and the tube dimensions were similar to those used by Wyslouzil et al (1997).…”

“…The mist deposition model (Wyslouzil et al, 1997) treats dense beds of roots as fibrous filters. Although root beds have regions of high and low packing density and growth occurs in all directions, the model still describes the qualitative trends and behavior of mist deposition quite reasonably.…”

“…To explain this result, Kim et al (2002) compared the biological demand of the growing roots in the mist reactor to the level of substrate (sugar) deposited on the roots as a function of reactor packing fraction, where the deposition of medium droplets was calculated using a standard filter model (Wyslouzil et al, 1997). At low packing fractions the results suggested that the roots could not capture enough mist to grow at rates comparable to liquid culture methods, but at higher packing fractions the opposite appeared to be true.…”

Fog Water Collection Effectiveness: Mesh Intercomparisons

“…Of course, this represents only one of three factors that de Dios Rivera (2011) and others (Rajaram et al, 2016;Ritter, 2016, 2017) consider to represent the overall efficiency. Descriptions of the capture efficiency, η capt , as can be found in Regalado and Ritter (2016) are based upon work by Wyslouzil et al (1997), Friedlander (2000, Demoz et al (1996) and Davidson and Friedlander (1978). Regalado and Ritter (2016) illustrates a result for the droplet capture efficiency of a single cylindrical strand as ) is the dynamic viscosity of the air, and d (m) is the diameter of the assumed cylindrical screen elements.…”