Train flow

FIGURE 8-1. Site Worker Training Flow Diagram... 

In this section we illustrate how the proposed theory for single, surfactant-laden bubbles in a cylindrical tube can be extended to predict the hydrodynamic resistance of bubble trains flowing in porous media. Some of the basic ideas are known (7, 23), so the present discussion is brief. 

Flow tubes tend to operate on a faster timescale determined by the residence time in the flow tube and the position of a movable injector. The reactive surface can appear as coating or thin film on the flow tube wall (wetted-wall), either static or flowing, or can be in form of droplets or aerosol particles (droplet train flow tube and bubble column... 

Wall-coated flow tube reactors have been used to study the uptake coefficients onto liquid and solid surfaces. This method is sensitive over a wide range of y (10" to 10 1). For liquids this method has the advantage that the liquid surface is constantly renewed, however if the uptake rate is fast, the liquid phase becomes saturated with the species and the process is limited by diffusion within the liquid, so that corrections must be applied [70,72,74]. Many experiments were designed to investigate the interaction of atmospheric species on solid surfaces. In this case the walls of the flow tube were cooled and thin films of substrate material were frozen on the wall. Most of the reaction probabilities were obtained from studies on flow tubes coated with water-ice, NAT or frozen sulfate. Droplet train flow tube reactors have used where liquid droplets are generated by means of a vibrating orifice [75]. The uptake of gaseous species in contact with these droplets has been measured by tunable diode laser spectroscopy [41]. 

Thulasidas TC, Abraham MA, Cerro RL. Axial dispersion of bubble-train flow in capillaries. Chem Eng Sci 1996. 

Using a simple scaling analysis, involving (1) viscous pressure drop, (2) hydrostatic pressure drop, (3) interfacial pressure drop and (4) penetration theory for mass transfer, it has been demonstrated that two-phase laminar bubble-train flow in small channels can exhibit better mass transfer for a given power input than turbulent contactors. 

A. Morita, M. Sugiyama, H. Kameda, S. Koda, D. R. Hanson Mass accommodation coefficient of water molecular dynamics simulation and revised analysis of droplet train/flow reactor experiment, J. Phys. Chem. B 108, 9111-9120 (2004). 

Thulasidas, T. C., Abraham, M. A., Cerro, R. L. (1997). Flow patterns in liquid slugs during bubble-train flow inside capillaries. Chemical Engineering Science, 52, 2947-2962. 

Bubble train flow Elongated bubble flow Intermittent flow Plug flow Segmented flow Slug flow Taylor bubble flow... 

The analytical model developed by Thulasidas et al. [6], which is suitable for bubble train flow, showed that the transition to complete bypass (pattern 2a) occurs in horizontal flow at Ca = 0.7, in upward flow at Ca = 0.5, and in downward flow at Ca = 0.6. 

T.C. Thulasidas, M.A. Abraham, R.L. Cerro, Dispersion during bubble train flow in capillaries, Chem. Eng. Sci, 1999, 54, 61-76. 

R. Gruber, T. Melin, Radial mass transfer enhancement in bubble-train flow. International Journal of Heat and Mass Transfer, 2003, 46, 2799-2808. 

T. C. Thulasidas, M. A. Abraham and R. L. Cerro, Bubble-train flow in capillaries of circular and square cross-section. ChemicalEn neeringScience, 1995, 50(2), 183-199. 

Containment spray system (one of two trains) flow diagram. 

Eskin D, Mostowfi F. A model of a bubble train flow accompanied with mass transfer through a long microchannel. Int. J. Heat Fluid Flow 2012 33(1) 147-155. 

Sundaram, M.S., and Steinberg, M. (1986) Interaction between Coal and Methane during En-trained-Flow Flash Pyrolysis in Relation to Enhancement in Ethylene Yield, ACS Div. of Fuel Chem. Prepr 31(1), 162-9, New York, NY (Apr. 13-18). 

Recent measurements of accommodation coefficients of H20(g) to H20(l) have been made mainly using a liquid droplet train flow reactor or liquid droplet growth method. Although the obtained values converge within 0.1 values obtained by both methods. For example, the values of a obtained by the liquid droplet train method of Li et al. (2001) are 0.17 0.03 and 0.32 0.04 at 280 and 258 K, while the value by... 

Morita, A., Sugiyama, M., Koda, S. Gas-phase flow and diffusion analysis of the droplet train/ flow-reactor technique for the mass accommodation process. J. Phys. Chem. A107,1749-1759... 

The operational experience has shown that the Loss of RHR Function could be caused by a variety of events, from losses of power and other support systems to failures within the I C System and similar. Furthermore, the loss of RHR function could (and in many cases was) be caused by human interaction issues, like closing isolation valves, erroneous train/flow path manipulations, transfer, etc. All such possible causes are extremely plant specific, so a careful assessment needs to be performed to identify all such issues which lead to high risk configurations. 

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