Drag of contaminated bubbles in power-law fluids

Motion of partially contaminated bubbles in power-law liquids: Effect of wall retardation

“…In physical sense, the total drag coefficient increases (thus the rise velocity decreases) as the amount of contamination increases and/or the Reynolds number decreases and/or the power-law index increases and/or the confinement ratio increases. Furthermore, unlike in the case of the motion of unconfined bubble in power-law fluids (Nalajala and Kishore, 2014a), regardless of values of the cap angle and confinement ratio, in the present case of motion of confined bubbles, the crossover Reynolds number in C d vs. Re curves with respect to power-law behavior index is not observed in the range of λ = 0.2-0.5. Thus, it can be concluded that the retardation effects are much stronger than the non-Newtonian effects of the power-law fluids at small values of the Reynolds number.…”

Heat Transfer from Confined Contaminated Bubbles to Power‐Law Liquids at Low to Moderate Reynolds and Prandtl Numbers

“…The stagnant cap model has been extensively adopted to interpret experimental results and found that this model is consistent with experimental results not only at low to moderate Reynolds numbers but also at large values of the Reynolds numbers. Furthermore, this model is also tested theoretically by many researchers and proved to be reliable under a wide range of Reynolds numbers . As per this model, contaminants can adsorb at the first front half of the bubble surface and move towards the backside of the bubble because of the surface advection caused by the main flow .…”

“…Therefore, both from theoretical and industrial applications viewpoints, development of results on the motion and heat transfer from the contaminated confined bubbles to surrounding contaminated non‐Newtonian liquids is a prerequisite for the rational design and operation of liquid–gas contacting equipment. In this connection, recently Kishore and coworkers reported numerical results on a series of analogous problems. For instance, Kishore and colleagues delineated the flow and drag behavior of contaminated bubbles in Newtonian and shear‐thinning power‐law fluids in the range of conditions: Re = 10 to 200, n = 0.6 to 1 and α = 0 to 180˚ using their in‐house CFD solver namely semi‐implicit marker and cell algorithm implemented on a staggered grid arrangement in spherical coordinates.…”

“…This solver was also used by Nalajala and colleagues to investigate the effect of the volume fraction of the contaminated bubbles on the flow and drag behavior of swarms (ensembles) of contaminated bubbles in Newtonian fluids. Their study reported in was extended by Nalajala and Kishore for a much wider range of conditions such as Re = 0.1 to 200; n = 0.2 to 1.6 and α = 0 to 180˚ using ANSYS Fluent. The corresponding heat transfer characteristics of single unconfined contaminated bubbles in power‐law fluids is numerically investigated by Nalajala and Kishore for a range of conditions Re = 0.1 to 200; n = 0.2 to 1.6, Pr = 1 to 1000 and α = 0 to 180˚ using ANSYS Fluent.…”

Effect of Surfactants on Gas Holdup in Shear-Thinning Fluids

“…However, several fluids in practical processing industries exhibit shear-thinning behavior. Thus far, numerous studies reporting the effect of surfactants on bubble motion behavior in shear-thinning fluids mainly focus on the shape and velocity of single bubbles [9][10][11]. As compared to that of Newtonian fluids, significantly less is known about the effect of surfactants on the gas holdup in shear-thinning fluids because of their complicated rheological characteristics.…”