| 1. |
- Liu, Baoqing, et al.
(författare)
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Effect of gas distributor on gas–liquid dispersion and mass transfer characteristics in stirred tank
- 2019
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762. ; 145, s. 314-322
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Tidskriftsartikel (refereegranskat)abstract
- Aiming at the fact that the function of gas distributor is often neglected in the case of high viscosity conditions, a novel spherical micro-orifice gas distributor was proposed and investigated experimentally in water system and non-Newtonian viscous system, respectively. The comparisons of gas–liquid dispersion and mass transfer performance between novel spherical micro-orifice gas distributor and traditional ring distributor were also done. Furthermore, the effects of gas distributors on the gas–liquid dispersion and mass transfer characteristics of three wide-viscosity-range impellers including LDB impeller, FZ impeller and MB impeller were also researched, and an impeller-distributor configuration with good gas–liquid dispersion and mass transfer performance was achieved. The results show that, compared with ring gas distributor, the bubbles dispersed by novel spherical micro-orifice gas distributor are smaller, and the gas holdup and volumetric mass transfer coefficient are relatively higher under the same power consumption per unit volume. Meanwhile, the significant effect of gas distributor geometry on gas dispersion was found for high-viscosity liquid, but not relevant for low-viscosity batches. In addition, compared with other impeller-distributor configurations, the configuration consisting of FZ impeller and novel spherical micro-orifice gas distributor can achieve greater global gas holdup and higher oxygen mass transfer rate, which is recommended especially in viscous system with high gas flow rate. The research is beneficial to promote the application of novel spherical micro-orifice gas distributor in stirred tanks.
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| 2. |
- Sun, Ning, et al.
(författare)
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Design guidelines for fluid-elastic instability of tube bundles subjected to two-phase cross flow
- 2019
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Ingår i: Journal of Zhejiang University: Science A. - 1673-565X. ; 20:8, s. 577-589
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Tidskriftsartikel (refereegranskat)abstract
- Fluid-elastic instability of tube bundles is the main cause of vibration failure of heat exchangers. To establish more reasonable and reliable design guidelines for fluid-elastic instability of tube bundles subjected to two-phase cross flow, we investigated experimentally the effects of the flow conditions of the two-phase flow and the geometrical characteristics of the tube bundles on damping, vibration, and fluid-elastic instability. Moreover, we proposed recommended values of the instability constant based on the conductivity difference measurement (CDM) model and the classification of tube bundle arrangements. The reliability of these values was also verified. The results indicated that the damping ratio in the lift direction was smaller than that in the drag direction and fluid-elastic instability was more prone to occur. The order of stability of the four tube bundle arrangements from high to low was normal triangular, normal square, rotated square, and rotated triangular. Thus, to avoid fluid-elastic instability, the normal triangular tube bundle is recommended for large shell-and-tube heat exchangers subjected to two-phase cross flow. In addition, for normal square and normal triangular tube bundles, the recommended instability constant is 4.0. For rotated square and rotated triangular tube bundles, the recommended instability constant is 1.1 when the mass damping parameter is less than or equal to 0.54, otherwise the value is 1.5.
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