Accelerating tube flow through

The simplest flow-through cells are actually caps fitted at the end of the ISE and the reference electrode and connected by a tube (see fig. 5.5). Some researchers [80, 92] claim that stirring the solution inside the cap by a rod driven by an external magnet (fig. 5.56) accelerates the ISE response and improves the potential stability (see also section 5.1.2). The solution can also be led... 

Fig. 7.2. Diagram of the PDS-1000/He, a stationary particle bombardment machine that is connected to a helium gas container. Controlled by adjustable valves, the gas stream (He) terminates in an acceleration tube, which is mounted on the top of a target chamber. This chamber is closed by a door and set under vacuum shortly before bombardment. When gas flows into the acceleration tube, the rupture disc bursts releasing the shock wave into the lower part of the tube. The gas pressure then accelerates the macrocarrier sheet containing the microprojectiles on its lower surface. The net-like stopping screen holds the macrocarrier sheet back and serves to block the shock wave, while the microprojectiles slip through the pores of the grid and continue on towards their final target.

During the flow of the streams through the accelerating tubes, several factors may lead to pressure drop along the path. These factors include friction between the gas flow and the inside wall of the tube, acceleration of the particles, collisions of particles on the wall and between particles etc. For convenience, the pressure drop through the accelerating tube can be considered to consist of two constituents caused by gas flow and particles, respectively, -Apx.d and -Apdc p, which are discussed separately below. 

Similar to the calculation of pipe-resistance, the pressure drop caused by the gas flow passing through the accelerating tube, -ApXd, can be represented by... 

Thus, the sub-total pressure drop due to the suspension flow passing through the accelerating tube is written as... 

In Chap. 4 we explored the consequences of a weak departure from strict adherence to the conditions for unidirectional flow namely, the effect of slight curvature in flow through a circular tube. For that case, the centripetal acceleration associated with the curved path of the primary flow was shown to produce a weak secondary motion in the plane orthogonal to the tube axis. In this chapter we consider another class of deviations from unidirectional flow that occur when the boundaries are slightly nonparallel. 

Polymerization occurs to almost complete yield with no termination or transfer, but with two species of different activity. An example of such a reaction is the anionic polymerization of styrene, in which both the free anion and the ion pair are active species. However, these polymerizations proceed so rapidly that they can no longer be followed with the normal kinetic techniques. Kinetic measurements are therefore carried out by accelerated flow techniques (Figure 18-5). A turbulent current must prevail in this flow tube (Reynolds number over 10,000), since the chains would show growth times of differing duration with a laminar current. In a flow tube, the effective polymerization time t depends on the volume Vq of the flow tube (distance between the mixing jets) and on the volume V of the total liquid flowing through in the time t ... 

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