Investigation of hydrodynamics and transition regime in an internal loop airlift reactor using CFD

Abstract

-CFD modeling for an internal loop airlift reactor is developed for different superficial gas velocities, ranging from 0.015 to 0.073 m/s. Based on the presence of gas bubbles in the downcomer, three regimes can be generally classified as: no gas bubbles (I), stagnation of gas bubbles (II), and recirculation of gas bubbles into the riser (III). The aim of the study is to carefully investigate the regime transition from II to III by considering the gas distribution. In regime II, the CFD simulation results show that the gas holdup difference between the riser and the downcomer remains constant. Due to the transition from regime II to III, the gas holdup difference sharply increases and the ratio of gas holdup in the downcomer and riser changes between the two regimes. At a superficial gas velocity slightly lower than that of the transitional regime, a small amount of gas is dragged to the riser, while the behavior of the regime is similar to regime II. The computational results show that CFD can be used as an effective tool to provide information on the details of the transition regime in internal loop airlift reactors.

Evaluation of scale‐up methodologies and computational fluid dynamics simulation for fucoxanthin production in airlift photobioareactor

“…In detail, fluid rises in the draft tube while it moves in the opposite direction in the space between the reactor wall and the draft tube; the flow pattern of culture medium supported these findings (Figure S1). This motion is caused by the bulk density difference in these two regions that is a driving force 53 . In this study, the movements of culture medium and also cells progressed with the same way.…”

“…This motion is caused by the bulk density difference in these two regions that is a driving force. 53 In this study, the movements of culture medium and also cells progressed with the same way. In Figure 5c-e, air and culture medium velocity profiles within the PBR were investigated for different regions through the reactor column.…”

Heat transfer analyses using computational fluid dynamics in the air blast freezing of guava pulp in large containers

“…Tanaka et al (2012) developed a transient threedimensional computational fluid dynamics model to investigate the cooling performance of a partially loaded cold store in the cooling process. The model accounted for turbulence by means of the standard k-ε model with standard wall profiles (Ghasemi and Hosseini, 2012). The model was validated successfully in cooling experiments with a mean error of 0.36 m/s and 1.4 °C for the air velocity in a refrigerated room and the temperature of the product, respectively.…”

Bubbly flow in an airlift column: a CFD study

“…Airlift columns in contrast have received comparatively less attention in simulation studies. Recent simulations of bubbly flow in the internal loop type are given in the literature . In most of these studies, comparison with experiment has been made only for integral data like the total gas holdups in riser and downcomer or the average liquid circulation velocity.…”