Discontinuous flow

A well-mixed stirred tank (which we will continue to call a CSTR despite possibly discontinuous flow) has p = Pout- The unsteady-state balance for total mass is obtained just by including the accumulation term ... 

One assumes that a discontinuous flow occurs between regions 1 and 2, as shown in Fig. 1.2. The flow is also assumed to be one-dimensional and in a steady state, and not subject to a viscous force, an external force, or a chemical reaction. 

The solution expressed by Eq. (1.36) indicates that there is no discontinuous flow between the upstream 1 and the downstream 2. However, the solution given by Eq. (1.37) indicates the existence of a discontinuity of pressure, density, and temperature between 1 and 2. This discontinuity is called a normal shock wave , which is set-up in a flow field perpendicular to the flow direction. Discussions on the structures of normal shock waves and supersonic flow fields can be found in the relevant monographs. 

It is obvious that the entropy change will be positive in the region Mi > 1 and negative in the region Mi < 1 for gases with 1 < y < 1-67. Thus, Eq. (1.46) is valid only when Ml is greater than unity. In other words, a discontinuous flow is formed only when Ml > 1. This discontinuous surface perpendicular to the flow direction is the normal shock wave. The downstream Mach number, Mj, is always < 1, i. e. subsonic flow, and the stagnation pressure ratio is obtained as a function of Mi by Eqs. (1.37) and (1.41). The ratios of temperature, pressure, and density across the shock wave are obtained as a function of Mi by the use of Eqs. (1.38)-(1.40) and Eqs. (1.25)-(1.27). The characteristics of a normal shock wave are summarized as follows ... 

The whole assembly was placed in a discontinuous flow analyser [75] for the titration of 0.1 M NaOH with 0.1 M HCl. 

Other types of discontinuous flow reactors may be used for transient kinetic studies in which, for example, isotopically labelled reactants are widely used in kinetic studies. This kind of investigation has been particularly developed in the case of discontinuous flow reactors. A different instrument called TAP (for Temporal Analysis of Products) permits extremely sensitive detection of intermediates or products. The results obtained with these various instruments can provide information about reaction mechanisms. 

The continuity of the aquifer and active flow in it are independently checked by each of these parameters. This is essential because 14C may decrease with depth (and distance) also in cases of discontinuous flow. As a matter of fact, the obtained average flow velocity of 0.66 m/year is extremely slow, and it might indicate lack of flow in parts of the system. 

Roe, PL. (1985), Some contributions to the modeling of Discontinuous flows, in Lecture Notes in Applied Mathematics , Vol. 22, Springer-Verlag, Berlin, pp. 163-193. 

Roe PL (1985) Some contributions to the modeling of discontinuous flow. Lectures in Applied Mathematics 22 163-192... 

Similar to FI systems, in-line coupling of a sequential injection network with suitable detectors renders a detailed insight into leaching kinetics. As a consequence of the discontinuous flow nature of SIA, the in-line hyphenation of microcolumn assays with ETAAS is relatively simple, because of the discrete, noncontinuous operation of the detector. On the other hand, interfacing the miniaturized flow assembly with continuously operating detectors such as FAAS, HG-AFS, ICP-AES and ICP-MS requires the incorporation of conventional sample injectors (e.g., solenoid valves, rotary valves) for discrete introduction into the detection instrument of metered leachate volumes. 

Proper exploitation of multi-commutation has led to the inception of different flow analysers such as the multi-pumping flow system, the multi-syringe flow injection system, the flow-batch system, the discontinuous flow system [153] and the all injection system [154],... 

T.J. Cardwell, R.W. Cattrall, G.J. Cross, J.R. O Cornell, J.D. Petty, G.R. Scollary, Determination of titratable acidity of wines and total acidity of vinegars by discontinuous flow analysis using photometric end-point detection, Analyst 116 (1991) 1051. 

By maintaining the sample/reagent flow rates ratio, constant flow rates are attained, and this is inherent to, e.g., stepper motors driving syringe pumps (see also 6.1.2). A conceptual advance on differential pumping is to vary the flow rates of one or both pumps in a reproducible manner and this is the essence of the discontinuous flow analyser [139]. 

J.D. Petty, D.A. Petty, R.M. Peachey, T.K. Smith, B.L. Krieger, High-accuracy preformed gradient discontinuous flow titrimetry, Talanta 41 (1994) 359. 

R.W. Cattrall, G.R. Scollary, Discontinuous flow analysis generation of fluid flows by differential pumping, Anal. Method. Instrum. 2 (1995) 61. 

It is pointed out in [252] that more than 10% of the world oil recovery is accomplished by injecting steam or CO2 for the production of oil by EOR. Here, the foam bubble size is comparable or slightly more than the pore diameter. To increase oil production, highly disperse steam foam is required, which pushes the oil out of the reservoir while moving both as a continuous and discontinuous flow. It has to be emphasized that the choice of surfactant is important to accomplish the process. Typically, the surfactant concentration is much higher than CMC, which predetermines the expensiveness of the process. The foam is destroyed when coming in contact with oil and rock, which requires its increased consumption. Three mechanisms of foam formation under reservoir conditions are proposed in [253], determined by the liquid flow rate and the throat radius between the pores. When the foam flows in a reservoir, its aggregative stability is disturbed due to coalescence. Hence, the choice of... 

To produce a high quality surface (10-12), it is necessary to avoid a discontinuous flow of the melt through the profiling channel. A high quality profile with a polished surface is produced with degradation of the polymer surface as a consequence of the effect of the magnetostrictive transducer. The ultrasonic oscillations reduce the toughness of the polymer and the resistance of the wall affect the melt flow at the channel boundary. 

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