| dc.contributor.author | Luo, Jianjun. | en_US |
| dc.date.accessioned | 2014-10-21T12:37:50Z | |
| dc.date.available | 2002 | |
| dc.date.issued | 2002 | en_US |
| dc.identifier.other | AAINQ77597 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55888 | |
| dc.description | An experiment for investigating bubble coalescence rate in turbulent pipe flow was designed based on measuring evolution of the specific interfacial area at two locations along the pipeline. A broad range of operating conditions (i.e. 0.008 < phiG < 0.5, 4 < epsilonp < 26 w/kg, 25 mum < d32 < 8,700 mum, and sodium dodecyl sulfate (SDS) concentration range of 0--50 ppm) were investigated. Three bubble coalescence rates were developed based on the temporal rate of variation of Sauter mean diameter, specific interfacial area, and bubble population density and the resulting findings were discussed in terms of hydrodynamic factors (including gas hold-up, energy dissipation rate and bubble size) and interfacial properties. The bubble coalescence rate was found to increase as the gas hold-up and the energy dissipation rate increase, and decrease as the bubble size and SAA concentration increase. Compared to tap water, the normalized coalescence rates were found to decrease radically by the presence of minute dosage of SAA due to the decisive role interfacial characteristics play. The exponential format of interfacial parameters can be used to characterize their effect on bubble coalescence processes, which implies that the interfacial characteristics affect the bubble coalescence through influencing coalescence efficiency which leads to decreasing bubble coalescence rate in gas/liquid turbulent flow. A theoretical collision model was adapted to the case of bubble coalescence rate in turbulent two-phase flow in pipes, and the resulting expression was found to apply not only to pure water system but also to contaminated streams displaying surface activity. The use of different interfacial parameters (such as the static surface tension, surface pressure, Gibbs surface excess and surface excess based on long-term approximation) to explain how SAA retards bubble coalescence rate was evaluated and it was found although the dimensionless forms of these interfacial parameters are correlated with bubble coalescence rate for SDS aqueous solutions to the similar degrees, the surface excess based on the long-term approximation could prevail due to its revealing the underlying mechanism of coalescence hindrance. | en_US |
| dc.description | Factors affecting bubble dispersion and sparger performance were systematically investigated though the use of a 25.4 mm pipe loop in which liquid velocities of up to 3.2 m/s, and gas holdup varying between 0.008 and 0.5 were tested. Trace dosage of either MIBC or SDS was added to simulate the industrial streams. The use of novel dynamic spargers results in the formation of large interfacial area of contact (up to 5,400 m2/m3) and small bubbles (d32 down to 25 mum). The efficiency by which dynamic spargers utilize energy for the formation of interfacial area was found to be one order of magnitude higher than that obtained in mechanically-agitated tanks and traditional pipe nozzles, and more efficient than some of the commonly used static mixers operating at the same power input per unit mass of the stream processed. The interfacial area and the Sauter mean bubble size can be predicted by using correlation equations for MIBC and SDS aqueous solutions. (Abstract shortened by UMI.) | en_US |
| dc.description | Thesis (Ph.D.)--DalTech - Dalhousie University (Canada), 2002. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Engineering, Chemical. | en_US |
| dc.subject | Physics, Fluid and Plasma. | en_US |
| dc.title | Bubble dispersion and coalescence in turbulent pipe flow. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
